Index: ChangeLog-2.0.0-2.1.0.log
===================================================================
diff -u -r2a955681817e4db4776d7ae904babe8053c5ad74 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- ChangeLog-2.0.0-2.1.0.log (.../ChangeLog-2.0.0-2.1.0.log) (revision 2a955681817e4db4776d7ae904babe8053c5ad74)
+++ ChangeLog-2.0.0-2.1.0.log (.../ChangeLog-2.0.0-2.1.0.log) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -416,11 +416,10 @@
* nsf.c:
(ParamOptionParse): 'virtualobjectargs' and 'virtualclassargs'
defaulted to ConvertViaCmd when parsed from Tcl spec; explicitly
- set ConvertToNothing to match the intended semantics and to avoid
+ set ConvertToNothing to match the intended semantics and to avoid
false warnings (e.g., missing type=virtualobjectargs type checker).
[03b838a]
- (NsfParameterInfoCmd): Correct two typos in in-code
- comment. [6d563e2]
+ (NsfParameterInfoCmd): Correct two typos in code comment. [6d563e2]
2016-10-02 Stefan Sobernig <stefan.sobernig@wu.ac.at>
Index: ChangeLog-2.0b3-2.0b5.log
===================================================================
diff -u -r9aa53ef688133d4af8bdff20f8913fe34f8a44ad -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- ChangeLog-2.0b3-2.0b5.log (.../ChangeLog-2.0b3-2.0b5.log) (revision 9aa53ef688133d4af8bdff20f8913fe34f8a44ad)
+++ ChangeLog-2.0b3-2.0b5.log (.../ChangeLog-2.0b3-2.0b5.log) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -117,7 +117,7 @@
we might wish a more general solution (see comment for
futures releases)
- - when creation with an required configure parameter failed, delete the
+ - when creation with a required configure parameter failed, delete the
half-baked object to avoid confusing states.
- nx::test: show msg at start of test file
Index: ChangeLog-2.0b5-2.0.0.log
===================================================================
diff -u -rb5c493afe905b1bafc17697ed3ce01d1662c77b3 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- ChangeLog-2.0b5-2.0.0.log (.../ChangeLog-2.0b5-2.0.0.log) (revision b5c493afe905b1bafc17697ed3ce01d1662c77b3)
+++ ChangeLog-2.0b5-2.0.0.log (.../ChangeLog-2.0b5-2.0.0.log) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -529,7 +529,7 @@
function DependentSubClasses(). With the new implementation,
NsfParameterCacheClassInvalidateCmd() is as efficient as before without
to MostGeneralSuperclass optimization (but being complete now) when
- working on the root classes (an more efficient on subclasses).
+ working on the root classes (and more efficient on subclasses).
2014-06-04 Gustaf Neumann <neumann@wu-wien.ac.at>
Index: ChangeLog-2.2.0-2.3.0.log
===================================================================
diff -u -r63fa317128555211b749beedd51f32e82af6b340 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- ChangeLog-2.2.0-2.3.0.log (.../ChangeLog-2.2.0-2.3.0.log) (revision 63fa317128555211b749beedd51f32e82af6b340)
+++ ChangeLog-2.2.0-2.3.0.log (.../ChangeLog-2.2.0-2.3.0.log) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -279,7 +279,7 @@
* nsf.c, speedtest.xotcl: Improved handling of object property
autonamed [c86c0775]
* serializer.tcl: Preserve overriding slot accessor methods
- defined via XOTcl instprocs during serialisation. [542f9ead]
+ defined via XOTcl instprocs during serialization. [542f9ead]
2019-03-12 Stefan Sobernig <stefan.sobernig@wu.ac.at>
@@ -422,7 +422,7 @@
2018-10-24 Stefan Sobernig <stefan.sobernig@wu.ac.at>
* disposition.test, parameters.test: Adjust tests to reflect the
- changed representational behaviour for numerics (int, wide) according
+ changed representational behavior for numerics (int, wide) according
to TIP 514 (now in Tcl 8.7a2+). [fca63858]
2018-10-23 Gustaf Neumann <neumann@wu-wien.ac.at>
Index: doc/Announce2.3.0
===================================================================
diff -u -rfc11b2380eef48346410636908936e9468c74807 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- doc/Announce2.3.0 (.../Announce2.3.0) (revision fc11b2380eef48346410636908936e9468c74807)
+++ doc/Announce2.3.0 (.../Announce2.3.0) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -29,7 +29,7 @@
0
This is to avoid having to rely on pattern sniffing of the
- command names. In addition, the propery is now set early enough,
+ command names. In addition, the property is now set early enough,
right after allocating the NSF object, to test for the autonaming
condition from within the creation procedure (ttrace).
@@ -83,9 +83,9 @@
- XOTcl:
- * Improved compatibility of XOTcl2 with XOTcl1 behaviour
+ * Improved compatibility of XOTcl2 with XOTcl1 behavior
for volatile objects (see "volatile reform" above).
- * Improved compatibility of XOTcl2 with XOTcl1 behaviour for
+ * Improved compatibility of XOTcl2 with XOTcl1 behavior for
uplevel/upvar from within methods (see "uplevel/ upvar reform"
above).
Index: doc/next-migration.html
===================================================================
diff -u -r6cbeef2d45ae090cf57de7703e0b480125e277b1 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- doc/next-migration.html (.../next-migration.html) (revision 6cbeef2d45ae090cf57de7703e0b480125e277b1)
+++ doc/next-migration.html (.../next-migration.html) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -1,6488 +1,6488 @@
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-<head>
-<meta http-equiv="Content-Type" content="application/xhtml+xml; charset=UTF-8" />
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-<title>Migration Guide for the Next Scripting Language</title>
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-<span id="email"><code><<a href="mailto:neumann@wu-wien.ac.at">neumann@wu-wien.ac.at</a>></code></span><br />
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+<div id="header">
+<h1>Migration Guide for the Next Scripting Language</h1>
+<span id="author">Gustaf Neumann</span><br />
+<span id="email"><code><<a href="mailto:neumann@wu-wien.ac.at">neumann@wu-wien.ac.at</a>></code></span><br />
+<span id="revnumber">version 2.2.0,</span>
+<span id="revdate">September 2018</span>
+<br /><span id="revremark"></span>
<div id="toc">
<div id="toctitle">Table of Contents</div>
<noscript><p><b>JavaScript must be enabled in your browser to display the table of contents.</b></p></noscript>
-</div>
-</div>
-<div id="content">
-<div id="preamble">
-<div class="sectionbody">
-<div class="sidebarblock">
-<div class="content">
-<div class="title">Abstract</div>
-<div class="paragraph"><p>This document describes the differences between the Next Scripting
-Language Framework and XOTcl 1. In particular, it presents a
-migration guide from XOTcl 1 to NX, and presents potential
-incompatibilities between XOTcl 1 and XOTcl 2.</p></div>
-</div></div>
-<div class="paragraph"><p>The Next Scripting Language (NX) is a successor of XOTcl 1 and is
-based on 10 years of experience with XOTcl in projects containing
-several hundert thousand lines of code. While XOTcl was the first
-language designed to provide language support for design patterns, the
-focus of the Next Scripting Framework and NX are on combining this
-with Language Oriented Programming. In many respects, NX was designed
-to ease the learning of the language by novices (by using a more
-mainstream terminology, higher orthogonality of the methods, less
-predefined methods), to improve maintainability (remove sources of
-common errors) and to encourage developer to write better structured
-programs (to provide interfaces) especially for large projects, where
-many developers are involved.</p></div>
-<div class="paragraph"><p>The Next Scripting Language is based on the Next Scripting Framework
-which was developed based on the notion of language oriented
-programming. The Next Scripting Frameworks provides C-level support
-for defining and hosting multiple object systems in a single Tcl
-interpreter. The whole definition of NX is fully scripted
-(e.g. defined in <code>nx.tcl</code>). The Next Scripting Framework is shipped
-with three language definitions, containing NX and XOTcl 2. Most of
-the existing XOTcl 1 programs can be used without modification in the
-Next Scripting Framework by using XOTcl 2. The Next Scripting
-Framework requires Tcl 8.5 or newer.</p></div>
-<div class="paragraph"><p>Although NX is fully scripted (as well as XOTcl 2), our benchmarks
-show that scripts based on NX are often 2 or 4 times faster than the
-counterparts in XOTcl 1. But speed was not the primary focus on the
-Next Scripting Environment: The goal was primarily to find ways to
-repackage the power of XOTcl in an easy to learn environment, highly
-orthogonal environment, which is better suited for large projects,
-trying to reduce maintenance costs.</p></div>
-<div class="paragraph"><p>We expect that many user will find it attractive to upgrade
-from XOTcl 1 to XOTcl 2, and some other users will upgrade to NX.
-This document focuses mainly on the differences between XOTcl 1 and
-NX, but addresses as well potential incompatibilities between XOTcl 1
-and XOTcl 2. For an introduction to NX, please consult the NX tutorial.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_differences_between_xotcl_and_nx">1. Differences Between XOTcl and NX</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The Next Scripting Framework supports <em>Language Oriented Programming</em>
-by providing means to define potentially multiple object systems with
-different naming and functionality in a single interpreter. This
-makes the Next Scripting Framework a powerful instrument for defining
-multiple languages such as e.g. domain specific languages. This focus
-differs from XOTcl 1.</p></div>
-<div class="paragraph"><p>Technically, the language framework approach means that the languages
-implemented by the Next Scripting Framework (most prominently XOTcl 2
-and NX) are typically fully scripted and can be loaded via the usual
-Tcl <code>package require</code> mechanism.</p></div>
-<div class="paragraph"><p>Some of the new features below are provided by the Next Scripting
-Framework, some are implemented via the script files for XOTcl 2 and
-NX.</p></div>
-<div class="sect2">
-<h3 id="_features_of_nx">1.1. Features of NX</h3>
-<div class="paragraph"><p>In general, the Next Scripting Language (NX) differs from XOTcl
-in the following respects:</p></div>
-<div class="olist arabic"><ol class="arabic">
-<li>
-<p>
-<strong>Stronger Encapsulation:</strong> The Next Scripting Language favors
- a <em>stronger form of encapsulation</em> than XOTcl. Calling the own
- methods or accessing the own instance variables is typographically
- easier and computationally faster than these operations on other
- objects. This behavior is achieved via <em>resolvers</em>, which make some
- methods necessary in XOTcl 1 obsolete in NX (especially for importing
- instance variables). The encapsulation of NX is stronger than in
- XOTcl but still weak compared to languages like C++; a developer can
- still access other objects' variables via some idioms, but NX <em>makes
- accesses to other objects' variables explicit</em>. The requiredness to
- make these accesses explicit should encourage developer to implement
- well defined interfaces to provide access to instance variables.
-</p>
-</li>
-<li>
-<p>
-<strong>Additional Forms of Method Definition and Reuse:</strong>
- The Next Scripting Language
- provides much more orthogonal means to <em>define, reuse and
- introspect</em> scripted and C-implemented methods.
-</p>
-<div class="olist loweralpha"><ol class="loweralpha">
-<li>
-<p>
-It is possible to use NX <code>alias</code> to register methods
- under arbitrary names for arbitrary objects or classes.
-</p>
-</li>
-<li>
-<p>
-NX provides means for <em>method protection</em> (method modifiers
- <code>public</code>, <code>protected</code>, and <code>private</code>). Therefore developers have
- to define explicitly public interfaces in order to use methods
- from other objects.
-</p>
-</li>
-<li>
-<p>
-One can invoke in NX fully qualified methods to invoke
- methods outside the precedence path.
-</p>
-</li>
-<li>
-<p>
-One can define in NX <em>hierarchical method names</em> (similar to
- commands and subcommands, called method ensembles) in a
- convenient way to provide extensible, hierarchical naming of
- methods.
-</p>
-</li>
-<li>
-<p>
-One can use in NX the same interface to query (introspect)
- C-implemented and scripted methods/commands.
-</p>
-</li>
-</ol></div>
-</li>
-<li>
-<p>
-<strong>Orthogonal Parameterization:</strong>
- The Next Scripting Language provides an <em>orthogonal framework for
- parametrization</em> of methods and objects.
-</p>
-<div class="olist loweralpha"><ol class="loweralpha">
-<li>
-<p>
-In NX, the same argument parser is used for
-</p>
-<div class="ulist"><ul>
-<li>
-<p>
-Scripted Methods
-</p>
-</li>
-<li>
-<p>
-C-implemented methods and Tcl commands
-</p>
-</li>
-<li>
-<p>
-Object Parametrization
-</p>
-</li>
-</ul></div>
-</li>
-<li>
-<p>
-While XOTcl 1 provided only value-checkers for non-positional
- arguments for methods, the Next Scripting Framework provides
- the same value checkers for positional and non-positional
- arguments of methods, as well as for positional and
- non-positional configure parameters (<code>-parameter</code> in
- XOTcl 1).
-</p>
-</li>
-<li>
-<p>
-While XOTcl 1 supported only non-positional arguments at the
- begin of the argument list, these can be used now at arbitrary
- positions.
-</p>
-</li>
-</ol></div>
-</li>
-<li>
-<p>
-<strong>Value Checking:</strong>
-</p>
-<div class="olist loweralpha"><ol class="loweralpha">
-<li>
-<p>
-The Next Scripting Language supports checking of the <em>input
- parameters</em> and the <em>return values</em> of scripted and C-implemented
- methods and commands.
-</p>
-</li>
-<li>
-<p>
-NX provides a set of predefined checkers (like e.g. <code>integer</code>,
- <code>boolean</code>, <code>object</code>, …) which can be extended by the
- applications.
-</p>
-</li>
-<li>
-<p>
-Value Checking can be used for <em>single</em> and <em>multi-valued</em>
- parameters. One can e.g. define a list of integers
- with at least one entry by the parameter specification
- <code>integer,1..n</code>.
-</p>
-</li>
-<li>
-<p>
-Value Checking can be turned on/off globally or on the
- method/command level.
-</p>
-</li>
-</ol></div>
-</li>
-<li>
-<p>
-<strong>Scripted Init Blocks:</strong> The Next Scripting Language provides
- <em>scripted init blocks</em> for objects and classes (replacement for the
- dangerous dash "-" mechanism in XOTcl that allows one to set variables
- and invoke methods upon object creation).
-</p>
-</li>
-<li>
-<p>
-<strong>More Conventional Naming for Predefined Methods:</strong> The naming of
- the methods in the Next Scripting Language is much more in line with
- the mainstream naming conventions in OO languages. While for example
- XOTcl uses <code>proc</code> and <code>instproc</code> for object specific and inheritable
- methods, NX uses simply <code>method</code>.
-</p>
-</li>
-<li>
-<p>
-<strong>Profiling Support:</strong> The Next Scripting Language provides now two
- forms of profiling
-</p>
-<div class="ulist"><ul>
-<li>
-<p>
-Profiling via a DTrace provider (examples are e.g. in the dtrace
- subdirectory of the source tree)
-</p>
-</li>
-<li>
-<p>
-Significantly improved built-in profiling (results can be
- processed in Tcl).
-</p>
-</li>
-</ul></div>
-</li>
-<li>
-<p>
-<strong>Significantly Improved Test Suite:</strong> The regression test suite of
- Next Scripting Scripting framework contain now more than
- 5.000 tests, and order of magnitude more than in XOTcl 1.6
-</p>
-</li>
-<li>
-<p>
-<strong>Much Smaller Interface:</strong> The Next Scripting Language has a much
- <em>smaller interface</em> (i.e. provides less predefined methods) than
- XOTcl (see Table 1), although the expressiveness was increased in
- NX.
-</p>
-</li>
-</ol></div>
-<div class="tableblock">
-<table rules="all"
-width="50%"
-frame="hsides"
-cellspacing="0" cellpadding="4">
-<caption class="title">Table 1. Comparison of the Number of Predefined Methods in NX and XOTcl</caption>
-<col width="60%" />
-<col width="20%" />
-<col width="20%" />
-<thead>
-<tr>
-<th align="left" valign="top"></th>
-<th align="right" valign="top">NX</th>
-<th align="right" valign="top">XOTcl</th>
-</tr>
-</thead>
-<tfoot>
-<tr>
-<td align="left" valign="top"><p class="table">Total</p></td>
-<td align="right" valign="top"><p class="table">45</p></td>
-<td align="right" valign="top"><p class="table">124</p></td>
-</tr>
-</tfoot>
-<tbody>
-<tr>
-<td align="left" valign="top"><p class="table">Methods for Objects</p></td>
-<td align="right" valign="top"><p class="table">14</p></td>
-<td align="right" valign="top"><p class="table">51</p></td>
-</tr>
-<tr>
-<td align="left" valign="top"><p class="table">Methods for Classes</p></td>
-<td align="right" valign="top"><p class="table">9</p></td>
-<td align="right" valign="top"><p class="table">24</p></td>
-</tr>
-<tr>
-<td align="left" valign="top"><p class="table">Info-methods for Objects</p></td>
-<td align="right" valign="top"><p class="table">11</p></td>
-<td align="right" valign="top"><p class="table">25</p></td>
-</tr>
-<tr>
-<td align="left" valign="top"><p class="table">Info-methods for Classes</p></td>
-<td align="right" valign="top"><p class="table">11</p></td>
-<td align="right" valign="top"><p class="table">24</p></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>This comparison list compares mostly XOTcl 1 with NX, some features
-are also available in XOTcl 2 (2a, 2c 2d, 3, 4).</p></div>
-</div>
-<div class="sect2">
-<h3 id="_nx_and_xotcl_scripts">1.2. NX and XOTcl Scripts</h3>
-<div class="paragraph"><p>Below is a small, introductory example showing an implementation of a
-class <code>Stack</code> in NX and XOTcl. The purpose of this first example is
-just a quick overview. We will go into much more detailed comparison
-in the next sections.</p></div>
-<div class="paragraph"><p>NX supports a block syntax, where the methods are defined during the
-creation of the class. The XOTcl syntax is slightly more redundant,
-since every definition of a method is a single toplevel command
-starting with the class name (also NX supports the style used in
-XOTcl). In NX, all methods are per default protected (XOTcl does not
-support protection). In NX methods are defined in the definition of
-the class via <code>:method</code> or <code>:public method</code>. In XOTcl methods are
-defined via the <code>instproc</code> method.</p></div>
-<div class="paragraph"><p>Another difference is the notation to refer to instance variables. In
-NX, instance variable are named with a single colon in the front. In
-XOTcl, instance variables are imported using <code>instvar</code>.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="top">Stack example in NX </th>
-<th align="left" valign="top">Stack example in XOTcl</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="top"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Stack {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Stack of Things
-</span> <span class='nx-comment'>#
-</span>
- <span class='nx-keyword'>:variable</span> things <span class='nx-string'>""</span>
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
- }
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
- <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
- }
-}</pre></div></div></div></td>
-<td align="left" valign="top"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Stack of Things
-</span><span class='nx-comment'>#
-</span>
-<span class='nx-keyword'>Class</span> Stack
-
-Stack instproc <span class='nx-keyword'>init</span> {} {
- <span class='nx-keyword'>my</span> instvar things
- <span class='nx-keyword'>set</span> things <span class='nx-string'>""</span>
-}
-
-Stack instproc push {thing} {
- <span class='nx-keyword'>my</span> instvar things
- <span class='nx-keyword'>set</span> things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>$things</span> 0 <span class='nx-variable'>$thing</span>]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
-}
-
-Stack instproc pop {} {
- <span class='nx-keyword'>my</span> instvar things
- <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>$things</span> 0]
- <span class='nx-keyword'>set</span> things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>$things</span> 1 end]
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_using_xotcl_2_0_and_the_next_scripting_language_in_a_single_interpreter">1.3. Using XOTcl 2.0 and the Next Scripting Language in a Single Interpreter</h3>
-<div class="paragraph"><p>In general, the Next Scripting Framework supports multiple object
-systems concurrently. Effectively, every object system has different
-base classes for creating objects and classes. Therefore, these object
-systems can have different interfaces and names of built-in
-methods. Currently, the Next Scripting Framework is packaged with
-three object systems:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-NX
-</p>
-</li>
-<li>
-<p>
-XOTcl 2.0
-</p>
-</li>
-<li>
-<p>
-TclCool
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>XOTcl 2 is highly compatible with XOTcl 1, the language NX is
-described below in more details, the language TclCool was introduced
-in Tip#279 and serves primarily an example of a small OO language.</p></div>
-<div class="paragraph"><p>A single Tcl interpreter can host multiple Next Scripting Object
-Systems at the same time. This fact makes migration from XOTcl to NX
-easier. The following example script shows to use XOTcl and NX in a
-single script:</p></div>
-<div class="listingblock">
-<div class="title">Using Multiple Object Systems in a single Script</div>
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>namespace</span> <span class='nx-keyword'>eval</span> mypackage {
-
- <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> XOTcl 2.0
-
- <span class='nx-comment'># Define a class with a public method foo using XOTcl
-</span> <span class='nx-keyword'>xotcl::Class</span> C1
- C1 instproc foo {} {<span class='nx-keyword'>puts</span> <span class='nx-string'>"hello world"</span>}
-
- <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
-
- <span class='nx-comment'># Define a class with a public method foo using NX
-</span> <span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C2 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>puts</span> <span class='nx-string'>"hello world"</span>}
- }
-}</pre></div></div>
-<div class="paragraph"><p>One could certainly create object or classes from the different object
-systems via fully qualified names (e.g. using e.g. <code>::xotcl::Class</code> or
-<code>::nx::Class</code>), but for migration for systems without explicit
-namespaces switching between the object systems eases migration.
-"Switching" between XOTcl and NX effectively means the load some
-packages (if needed) and to import either the base classes (Object and
-Class) of XOTcl or NX into the current namespace.</p></div>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_xotcl_idioms_in_the_next_scripting_language">2. XOTcl Idioms in the Next Scripting Language</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>The following sections are intended for reader familiar with XOTcl and
-show, how certain language Idioms of XOTcl can be expressed in NX. In
-some cases, multiple possible realizations are listed</p></div>
-<div class="sect2">
-<h3 id="_defining_objects_and_classes">2.1. Defining Objects and Classes</h3>
-<div class="paragraph"><p>When creating objects or classes, one should use the method <code>create</code>
-explicitly. In XOTcl, a default <code>unknown</code> method handler was provided for
-classes, which create for every unknown method invocation an
-object/class with the name of the invoked method. This technique was
-convenient, but as well dangerous, since typos in method names lead
-easily to unexpected behavior. This default unknown method handler is not
-provided in NX (but can certainly be provided as a one-liner in NX by
-the application).</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> ClassName</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> ClassName</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Object</span> ObjectName</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> ObjectName</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_defining_methods">2.2. Defining Methods</h3>
-<div class="paragraph"><p>In general, both XOTcl and NX support methods on the object level
-(per-object methods, i.e. methods only applicable to a single object)
-and on the class level (methods inherited to instances of the
-classes). While the naming in XOTcl tried to follow closely the Tcl
-tradition (using the term <code>proc</code> for functions/methods), NX uses the
-term <code>method</code> for defining scripted methods.</p></div>
-<div class="paragraph"><p>XOTcl uses the prefix <code>inst</code> to denote that methods are provided for
-instances, calling therefore scripted methods for instances
-<code>instproc</code>. This is certainly an unusual term. The approach with the
-name prefix has the disadvantage, that for every different kind of
-method, two names have to be provided (e.g. <code>proc</code> and <code>instproc</code>,
-<code>forward</code> and <code>instforward</code>).</p></div>
-<div class="paragraph"><p>NX on the contrary uses the same term for defining instance method or
-object-specific methods. When the term (e.g. <code>method</code>) is used on a
-class, the method will be an instance method (i.e. applicable to the
-instances of the class). When the term is used on an object with the
-modifier <code>object</code>, an object-specific method is defined. This way one
-can define the same way object specific methods on an object as well
-as on a class.</p></div>
-<div class="paragraph"><p>Furthermore, both XOTcl and NX distinguish between scripted methods
-(section 3.2.1) and C-defined methods (section 3.2.2). Section 3.2.3
-introduces method protection, which is only supported by NX.</p></div>
-<div class="sect3">
-<h4 id="_scripted_methods_defined_in_the_init_block_of_a_class_object_or_with_separate_calls">2.2.1. Scripted Methods Defined in the Init-block of a Class/Object or with Separate Calls</h4>
-<div class="paragraph"><p>The following examples show the definition of a class and its methods
-in the init-block of a class (NX only), and the definition of methods
-via separate top level calls (XOTcl and NX).</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define instance method 'foo' and object
-</span><span class='nx-comment'># method 'bar' for a Class 'C' with separate
-</span><span class='nx-comment'># toplevel commands
-</span>
-<span class='nx-keyword'>Class</span> C
-C instproc foo args {...}
-C <span class='nx-keyword'>proc</span> bar args {...}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define instance method and object method
-</span><span class='nx-comment'># in the init-block of a class
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:method</span> foo args {...}
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> bar args {...}
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define instance method and object method
-</span><span class='nx-comment'># with separate commands
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C
-C <span class='nx-keyword'>method</span> foo args {...}
-C <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar args {...}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define object-specific method foo
-</span><span class='nx-comment'># for an object 'o' with separate commands
-</span>
-<span class='nx-keyword'>Object</span> o
-o <span class='nx-keyword'>set</span> x 1
-o <span class='nx-keyword'>proc</span> foo args {...}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define object method and set
-</span><span class='nx-comment'># instance variable in the init-block of
-</span><span class='nx-comment'># an object
-</span>
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>set</span> :x 1
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> foo args {...}
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define object method and set
-</span><span class='nx-comment'># instance variable with separate
-</span><span class='nx-comment'># commands
-</span>
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o
-o <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>set</span> :x 1}
-o <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo args {...}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_different_kinds_of_methods">2.2.2. Different Kinds of Methods</h4>
-<div class="paragraph"><p>This section describes various kinds of methods. The different kinds
-of methods are defined via different method-defining methods, which
-are summarized in the following table for XOTcl and NX.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Methods for defining methods:
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># proc
-</span><span class='nx-comment'># instproc
-</span><span class='nx-comment'># forward
-</span><span class='nx-comment'># instforward
-</span><span class='nx-comment'># parametercmd
-</span><span class='nx-comment'># instparametercmd
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># All these methods return empty.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Methods for defining methods:
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># alias
-</span><span class='nx-comment'># forward
-</span><span class='nx-comment'># method
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># All these methods return method-handles.</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>In addition to scripted methods (previous section) XOTcl supports
-forwarder (called <code>forward</code> and <code>instforward</code>) and accessor functions
-to variables (called <code>parametercmd</code> and <code>instparametercmd</code>). The
-accessor functions are used normally internally when object-specific
-parameters are defined (see Section 3.4).</p></div>
-<div class="paragraph"><p>In NX forwarders are called <code>forward</code>. NX does not provide a public
-available method to define variable accessors like <code>parametercmd</code> in
-XOTcl, but use internally the Next Scripting Framework primitive
-<code>nsf::method::setter</code> when appropriate.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> C
-C instforward f1 ...
-C <span class='nx-keyword'>forward</span> f2 ...
-
-<span class='nx-keyword'>Object</span> o
-o <span class='nx-keyword'>forward</span> f3 ...</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define forwarder
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:forward</span> f1 ...
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>forward</span> f2 ...
-}
-
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>forward</span> f3 ...
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define setter and getter methods in XOTcl.
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># XOTcl provides methods for these.
-</span>
-<span class='nx-keyword'>Class</span> C
-C instparametercmd p1
-C parametercmd p2
-
-<span class='nx-keyword'>Object</span> o
-o parametercmd p3</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define setter and getter methods in NX.
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># NX does not provide own methods, but uses
-</span><span class='nx-comment'># the low level framework commands, since
-</span><span class='nx-comment'># application developer will only
-</span><span class='nx-comment'># need it in rare cases.
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C
-::nsf::method::setter C p1
-::nsf::method::setter C -per-object p2
-
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o
-::nsf::method::setter o p3</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>NX supports in contrary to XOTcl the method <code>alias</code> which can be used
-to register arbitrary Tcl commands or methods for an object or class
-under a provided method name. Aliases can be used to reuse a certain implementation in
-e.g. different object systems under potentially different names. In
-some respects aliases are similar to forwarders, but they do not
-involve forwarding overhead.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Method "alias" not available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define method aliases
-</span><span class='nx-comment'># (to scripted or non-scripted methods)
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:alias</span> a1 ...
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>alias</span> a2 ...
-}
-
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>alias</span> a3 ...
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="method-protect-example">2.2.3. Method Modifiers and Method Protection</h4>
-<div class="paragraph"><p>NX supports four method modifiers <code>object</code>, <code>public</code>, <code>protected</code> and
-<code>private</code>. All method modifiers can be written in front of every
-method defining command. The method modifier <code>object</code> is used to denote
-object-specific methods (see above). The concept of method protection
-is new in NX.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Method modifiers
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># "object",
-</span><span class='nx-comment'># "public",
-</span><span class='nx-comment'># "protected", and
-</span><span class='nx-comment'># "private"
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># are not available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Method modifiers
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># "object",
-</span><span class='nx-comment'># "public",
-</span><span class='nx-comment'># "protected"
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># are applicable for all kinds of
-</span><span class='nx-comment'># method defining methods:
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># method, forward, alias
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># The modifier "private" is available for
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># method, forward, alias
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- :/<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:public</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:protected</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:private</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:protected</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
- <span class='nx-keyword'>:private</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>XOTcl does not provide method protection. In NX, all methods are
-defined per default as protected. This default can be changed by the
-application developer in various ways. The command <code>::nx::configure
-defaultMethodCallProtection true|false</code> can be used to set the default
-call protection for scripted methods, forwarder and aliases.
-The defaults can be overwritten also on a class level.</p></div>
-<div class="paragraph"><p>NX provides means for method hiding via the method modifier
-<code>private</code>. Hidden methods can be invoked only via the <code>-local</code> flag,
-which means: "call the specified method defined in the same
-class/object as the currently executing method".</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># XOTcl provides no means for
-</span><span class='nx-comment'># method hiding</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Hiding of methods via "private"
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
- <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> baz {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> + <span class='nx-variable'>$b</span>}}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a b} {: -local baz <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Sub -superclass Base {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a b} {: -local baz <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
- <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> baz {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> * <span class='nx-variable'>$b</span>}}
-
- <span class='nx-keyword'>:create</span> s1
-}
-
-s1 foo 3 4 ;<span class='nx-comment'># returns 7
-</span>s1 bar 3 4 ;<span class='nx-comment'># returns 12
-</span>s1 baz 3 4 ;<span class='nx-comment'># unable to dispatch method 'baz'</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="method-deletion">2.2.4. Method Deletion</h4>
-<div class="paragraph"><p>NX provides an explicit <code>delete</code> method for the deletion of methods.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># XOTcl provides only method deletion with
-</span><span class='nx-comment'># the equivalent of Tcl's "proc foo {} {}"
-</span><span class='nx-placeholder'>/cls/</span> instproc foo {} {}
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>proc</span> foo {} {}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Deletion of Methods
-</span><span class='nx-comment'>#
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/name/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_resolvers">2.3. Resolvers</h3>
-<div class="paragraph"><p>The Next Scripting Framework defines Tcl resolvers for method and
-variable names to implement object specific behavior. Within the
-bodies of scripted methods these resolver treat variable and function
-names starting with a colon <code>:</code> specially. In short, a colon-prefixed
-variable name refers to an instance variable, and a colon-prefixed
-function name refers to a method. The sub-sections below provide
-detailed examples.</p></div>
-<div class="paragraph"><p>Note that the resolvers of the Next Scripting Framework can be used in
-the XOTcl 2.* environment as well.</p></div>
-<div class="sect3">
-<h4 id="_invoking_methods">2.3.1. Invoking Methods</h4>
-<div class="paragraph"><p>In XOTcl, a method of the same object can be invoked via <code>my</code>, or in
-general via using the name of the object in front of the method name.</p></div>
-<div class="paragraph"><p>In NX, the own methods are called via the method name prefixed with a
-single colon. The invocation of the methods of other objects is the
-same in NX and XOTcl.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> C
-C instproc foo args {...}
-C instproc bar args {
- <span class='nx-keyword'>my</span> foo 1 2 3 ;<span class='nx-comment'># invoke own method
-</span> o baz ;<span class='nx-comment'># invoke other object's method
-</span>}
-<span class='nx-keyword'>Object</span> o
-o <span class='nx-keyword'>proc</span> baz {} {...}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:method</span> foo args {...}
- <span class='nx-keyword'>:method</span> bar args {
- :foo 1 2 3 ;<span class='nx-comment'># invoke own method
-</span> o baz ;<span class='nx-comment'># invoke other object's method
-</span> }
-}
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {} {...}
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_accessing_own_instance_variables_from_method_bodies">2.3.2. Accessing Own Instance Variables from Method Bodies</h4>
-<div class="paragraph"><p>In general, the Next Scripting Language favors the access to an
-objects’s own instance variables over variable accesses of other
-objects. This means that in NX it is syntactically easier to access
-the own instance variables. On the contrary, in XOTcl, the variable
-access to own and other variables are fully symmetric.</p></div>
-<div class="paragraph"><p>In XOTcl, the following approaches are used to access instance
-variables:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-Import instance variables via <code>instvar</code> and access variables via <code>$varName</code>
-</p>
-</li>
-<li>
-<p>
-Set or get instance variables via <code>my set varName ?value?</code> or other
- variable accessing methods registered on <code>xotcl::Object</code> such as
- <code>append</code>, <code>lappend</code>, <code>incr</code>, etc.
-</p>
-</li>
-<li>
-<p>
-Register same-named accessor functions and set/get values
- of instance variables via <code>my varName ?value?</code>
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>In NX, the favored approach to access instance variables is to use
-the name resolvers, although it is as well possible to import
-variables via <code>nx::var import</code> or to check for the existence of
-instance variables via <code>nx::var exists</code>.</p></div>
-<div class="paragraph"><p>The following examples summary the use cases for accessing the own and
-other instance variables.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> C
-C instproc foo args {
- <span class='nx-comment'># Method scoped variable a
-</span> <span class='nx-keyword'>set</span> a 1
- <span class='nx-comment'># Instance variable b
-</span> <span class='nx-keyword'>my</span> instvar b
- <span class='nx-keyword'>set</span> b 2
- <span class='nx-comment'># Global variable/namespaced variable c
-</span> <span class='nx-keyword'>set</span> ::c 3
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:method</span> foo args {...}
- <span class='nx-comment'># Method scoped variable a
-</span> <span class='nx-keyword'>set</span> a 1
- <span class='nx-comment'># Instance variable b
-</span> <span class='nx-keyword'>set</span> :b 2
- <span class='nx-comment'># Global variable/namespaced variable c
-</span> <span class='nx-keyword'>set</span> ::c 3
- }
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... instproc ... {
- <span class='nx-keyword'>my</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Set own instance variable to a value via
-</span><span class='nx-comment'># resolver (preferred and fastest way)
-</span>
-... <span class='nx-keyword'>method</span> ... {
- <span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/newVar/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... instproc ... {
- <span class='nx-keyword'>my</span> instvar <span class='nx-placeholder'>/varName/</span>
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Set own instance variable via
-</span><span class='nx-comment'># variable import
-</span>
-... <span class='nx-keyword'>method</span> ... {
- ::nx::var import [<span class='nx-keyword'>self</span>] <span class='nx-placeholder'>/varName/</span>
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... instproc ... {
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-keyword'>my</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/otherVar/</span>]
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Read own instance variable
-</span>
-... <span class='nx-keyword'>method</span> ... {
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/otherVar/</span>]
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... <span class='nx-keyword'>method</span> ... {
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/newVar/</span> <span class='nx-variable'>${</span><span class='nx-variable'>:/otherVar/}</span>
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... instproc ... {
- <span class='nx-keyword'>my</span> exists <span class='nx-placeholder'>/varName/</span>
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Test existence of own instance variable
-</span>
-... <span class='nx-keyword'>method</span> ... {
- <span class='nx-keyword'>info</span> :<span class='nx-placeholder'>/varName/</span>
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'> ... <span class='nx-keyword'>method</span> ... {
- ::nx::var exists [<span class='nx-keyword'>self</span>] <span class='nx-placeholder'>/varName/</span>
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_accessing_instance_variables_of_other_objects">2.3.3. Accessing Instance Variables of other Objects</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Set instance variable of object obj to a
-</span><span class='nx-comment'># value via resolver
-</span><span class='nx-comment'># (preferred way: define property on obj)
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> [<span class='nx-keyword'>list</span> <span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>]</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/otherVar/</span>]</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Read instance variable of object obj
-</span><span class='nx-comment'># via resolver
-</span>
-<span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/otherVar/</span>}]</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>... instproc ... {
- <span class='nx-placeholder'>/obj/</span> instvar <span class='nx-placeholder'>/varName/</span>
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Read instance variable of object /obj/
-</span><span class='nx-comment'># via import
-</span>
-... <span class='nx-keyword'>method</span> ... {
- ::nx::var import <span class='nx-placeholder'>/obj/</span> <span class='nx-placeholder'>/varName/</span>
- <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
-}</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> exists varName</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Test existence of instance variable of
-</span><span class='nx-comment'># object obj
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>info</span> exists :<span class='nx-placeholder'>/varName/</span>}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>::nx::var exists <span class='nx-placeholder'>/obj/</span> <span class='nx-placeholder'>/varName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_parameters">2.4. Parameters</h3>
-<div class="paragraph"><p>While XOTcl 1 had very limited forms of parameters, XOTcl 2 and NX
-provide a generalized and highly orthogonal parameter machinery
-handling various kinds of value constraints (also called value
-checkers). Parameters are used to specify,</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-how objects and classes are initialized (we call these parameter types
- <em>Configure Parameters</em>), and
-</p>
-</li>
-<li>
-<p>
-what values can be passed to methods (we call these <em>Method
- Parameters</em>).
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>Furthermore, parameters might be positional or non-positional, they
-might be optional or required, they might have a defined multiplicity,
-and value-types, they might be introspected, etc. The Next Scripting
-Framework provide a unified, C-implemented infrastructure to handle
-both, object and method parameters in the same way with a high degree
-of orthogonality.</p></div>
-<div class="paragraph"><p>Configuration parameters were specified in XOTcl 1 primarily via the
-method <code>parameter</code> in a rather limited way, XOTcl 1 only supported
-non-positional parameters in front of positional ones, supported no
-value constraints for positional parameters, provided no distinction
-between optional and required, and did not support multiplicity.</p></div>
-<div class="paragraph"><p>Furthermore, the Next Scripting Framework provides optionally <em>Return
-Value Checking</em> based on the same mechanism to check whether some
-methods return always the values as specified.</p></div>
-<div class="sect3">
-<h4 id="_parameters_for_configuring_objects_variables_and_properties">2.4.1. Parameters for Configuring Objects: Variables and Properties</h4>
-<div class="paragraph"><p>Configure parameters are used for specifying values for configuring
-objects when they are created (i.e. how instance variables are
-initialized, what parameters can be passed in for initialization, what
-default values are used, etc.). Such configuration parameters are
-supported in XOTcl primarily via the method <code>parameter</code>, which is used
-in XOTcl to define multiple parameters via a list of parameter
-specifications.</p></div>
-<div class="paragraph"><p>Since the term "parameter" is underspecified, NX uses a more
-differentiated terminology. NX distinguishes between configurable
-instance variables (also called <em>properties</em>) and non configurable
-instance variables (called <em>variables</em>), which might have as well
-e.g. default values. The values of configurable properties can be
-queried at runtime via <code>cget</code>, and their values can be altered via
-<code>configure</code>. When the value of a configure parameter is provided or
-changed, the value checkers from the variable definition are used to
-ensure, the value is permissible (i.e. it is for example an integer
-value). The sum of all configurable object parameters are called
-<em>configure parameters</em>. To define a define a configurable variable, NX
-uses the method <code>property</code>, for non-configurable variables, the method
-<code>variable</code> is used.</p></div>
-<div class="paragraph"><p>Optionally, one can define in NX, that a <code>property</code> or a
-<code>variable</code> should have a public, protected or private accessor. Such
-an accessor is a method with the same name as the variable. In XOTcl,
-every <code>parameter</code> defined as well automatically a same-named accessor
-method, leading to potential name conflicts with other method names.</p></div>
-<div class="paragraph"><p>In the examples below we show the definition of configurable a non-configurable instance variables using <code>variable</code> and <code>property</code>
-respectively.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define class "Foo" with instance
-</span><span class='nx-comment'># variables "x" and "y" initialized
-</span><span class='nx-comment'># on instance creation. The initialization
-</span><span class='nx-comment'># has to be performed in the constructor.
-</span>
-<span class='nx-keyword'>Class</span> Foo
-Foo instproc <span class='nx-keyword'>init</span> args {
- instvar x y
- <span class='nx-keyword'>set</span> x 1
- <span class='nx-keyword'>set</span> y 2
-}
-
-<span class='nx-comment'># Create instance of the class Foo
-</span>Foo f1
-
-<span class='nx-comment'># Object f1 has instance variables
-</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define class "Foo" with instance variables
-</span><span class='nx-comment'># "x" and "y" initialized on instance creation.
-</span><span class='nx-comment'># The method "variable" is similar in syntax
-</span><span class='nx-comment'># to Tcl's "variable" command. During
-</span><span class='nx-comment'># instance creation, the variable
-</span><span class='nx-comment'># definitions are used for the
-</span><span class='nx-comment'># initialization of the variables of the object.
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:variable</span> x 1
- <span class='nx-keyword'>:variable</span> y 2
-}
-
-<span class='nx-comment'># Create instance of the class Foo
-</span>Foo <span class='nx-keyword'>create</span> f1
-
-<span class='nx-comment'># Object f1 has instance variables
-</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>While XOTcl follows a procedural way to initialize variables via the
-constructor <code>init</code>, NX follows a more declarative approach. Often,
-classes have superclasses, which often want to provide their own
-instance variables and default values. The declarative approach from
-NX solves this via inheritance, while a procedural approach via
-assign statements in the constructor requires explicit constructor
-calls, which are often error-prone. Certainly, when a user prefers to
-assign initial values to instance variables via explicit assign
-operations in constructors, this is as well possible in NX.</p></div>
-<div class="paragraph"><p>NX uses the same mechanism to define class variables or object
-variables.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># No syntactic support for creating
-</span><span class='nx-comment'># class variables</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>
-<span class='nx-comment'># Define a object variable "V" with value 100 and
-</span><span class='nx-comment'># an instance variable "x". "V" is defined for the
-</span><span class='nx-comment'># class object Foo, "x" is defined in the
-</span><span class='nx-comment'># instances of the class. "object variable" works
-</span><span class='nx-comment'># similar to "object method".
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>variable</span> V 100
- <span class='nx-keyword'>:variable</span> x 1
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>In the next step, we define configurable instance variables which we
-call <em>properties</em> in NX.</p></div>
-<div class="paragraph"><p>XOTcl uses the method <code>parameter</code> is a shortcut for creating multiple
-configurable variables with automatically created accessors (methods for
-reading and writing of the variables). In NX, the preferred way to
-create configurable variables is to use the method <code>property</code>. The
-method <code>property</code> in NX is similar to <code>variable</code>, but makes the
-variables configurable, which means that</p></div>
-<div class="olist arabic"><ol class="arabic">
-<li>
-<p>
-one can specify the property as a non-positional parameter upon
- creation of the object,
-</p>
-</li>
-<li>
-<p>
-one can query the value via the method <code>cget</code>, and
-</p>
-</li>
-<li>
-<p>
-one can modify the value of the underlying variable via the method
- <code>configure</code>.
-</p>
-</li>
-</ol></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Parameters specified as a list
-</span><span class='nx-comment'># (short form); parameter
-</span><span class='nx-comment'># "a" has no default, "b" has default "1"
-</span>
-<span class='nx-keyword'>Class</span> Foo -parameter {a {b 1} {c <span class='nx-string'>"[info tclversion]"</span>}}
-
-<span class='nx-comment'># Create instance of the class Foo
-</span>Foo f1 -a 0
-
-<span class='nx-comment'># Object f1 has instance variables
-</span><span class='nx-comment'># a == 0 and b == 1
-</span>
-<span class='nx-comment'># XOTcl registers automatically accessors
-</span><span class='nx-comment'># for the parameters. Use the accessor
-</span><span class='nx-comment'># "b" to output the value of variable "b"
-</span><span class='nx-keyword'>puts</span> [f1 b]
-
-<span class='nx-comment'># Use the setter to alter value of
-</span><span class='nx-comment'># instance variable "b"
-</span>f1 b 100
-
-<span class='nx-comment'># Return the substituted value of
-</span><span class='nx-comment'># parameter "c", something like 8.7.
-</span><span class='nx-comment'># XOTcl substitutes always when it sees
-</span><span class='nx-comment'># square brackets or dollar signs.
-</span>f1 c
-</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define property "a" and "b". The
-</span><span class='nx-comment'># property "a" has no default, "b" has
-</span><span class='nx-comment'># default value "1"
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:property</span> a
- <span class='nx-keyword'>:property</span> {b 1}
- <span class='nx-keyword'>:property</span> {c <span class='nx-string'>"[info tclversion]"</span>}
- <span class='nx-keyword'>:property</span> {d:substdefault <span class='nx-string'>"[info tclversion]"</span>}
-}
-
-<span class='nx-comment'># Create instance of the class Foo
-</span>Foo <span class='nx-keyword'>create</span> f1 -a 0
-
-<span class='nx-comment'># Object f1 has instance variables
-</span><span class='nx-comment'># a == 0 and b == 1
-</span>
-<span class='nx-comment'># Use the method "cget" to query the value
-</span><span class='nx-comment'># of a configuration parameter
-</span><span class='nx-keyword'>puts</span> [f1 <span class='nx-keyword'>cget</span> -b]
-
-<span class='nx-comment'># Use the method "configure" to alter the
-</span><span class='nx-comment'># value of instance variable "b"
-</span>f1 <span class='nx-keyword'>configure</span> -b 100
-
-<span class='nx-comment'># Return the (non substituted) value of
-</span><span class='nx-comment'># parameter "c", and the substituted value
-</span><span class='nx-comment'># of parameter "d"
-</span>f1 <span class='nx-keyword'>cget</span> -c
-f1 <span class='nx-keyword'>cget</span> -d
-</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>In general, NX allows one to create variables and properties with and
-without accessor methods. The created accessor methods might be
-<code>public</code>, <code>protected</code> or <code>public</code>. When the value <code>none</code> is provided
-to <code>-accessor</code>, no accessor will be created. This is actually the
-default in NX. In order to change the default behavior in NX, one can use
-<code>::nx::configure defaultAccessor none|public|protected|private</code>.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># "parameter" creates always accessor
-</span><span class='nx-comment'># methods, accessor methods are
-</span><span class='nx-comment'># always public, no "cget" is available.
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -parameter {a {b 1}}
-
-<span class='nx-comment'># Use the accessor method to query
-</span><span class='nx-comment'># the value of a configuration parameter
-</span><span class='nx-keyword'>puts</span> [f1 b]
-
-<span class='nx-comment'># Use the accessor method to set the
-</span><span class='nx-comment'># value of instance variable "a"
-</span>f1 a 100
-
-<span class='nx-comment'># Use the accessor method to unset the
-</span><span class='nx-comment'># value of instance variable "a" n.a. via
-</span><span class='nx-comment'># accessor</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define property "a" and "b". The
-</span><span class='nx-comment'># property "a" has no default, "b" has
-</span><span class='nx-comment'># default value "1"
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:variable</span> -accessor <span class='nx-keyword'>public</span> a
- <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {b 1}
-}
-
-<span class='nx-comment'># Use the accessor method to query
-</span><span class='nx-comment'># the value of a configuration parameter
-</span><span class='nx-keyword'>puts</span> [f1 b get]
-
-<span class='nx-comment'># Use the accessor method to set the
-</span><span class='nx-comment'># value of instance variable "a"
-</span>f1 a <span class='nx-keyword'>set</span> 100
-
-<span class='nx-comment'># Use the accessor method to unset the
-</span><span class='nx-comment'># value of instance variable "a"
-</span>f1 a <span class='nx-keyword'>unset</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>Similar to <code>variable</code>, properties can be defined in NX on the class
-and on the object level.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># XOTcl provides no means to define
-</span><span class='nx-comment'># configurable variables at the object
-</span><span class='nx-comment'># level</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define class with a property for the class object
-</span><span class='nx-comment'># named "cp". This is similar to "static variables"
-</span><span class='nx-comment'># in some other object-oriented programming
-</span><span class='nx-comment'># languages.
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- ...
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>property</span> cp 101
-}
-
-<span class='nx-comment'># Define object property "op"
-</span>
-<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>property</span> op 102
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>NX supports <em>value constraints</em> (value-checkers) for object and method
-parameters in an orthogonal manner. NX provides a predefined set of
-value checkers, which can be extended by the application developer.
-In NX, the <em>value checking is optional</em>. This means that it is possible to
-develop e.g. which a large amount of value-checking and deploy the
-script with value checking turned off, if the script is highly
-performance sensitive.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># No value constraints for
-</span><span class='nx-comment'># parameter available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Predefined value constraints:
-</span><span class='nx-comment'># object, class, alnum, alpha, ascii, boolean,
-</span><span class='nx-comment'># control, digit, double, false, graph, integer,
-</span><span class='nx-comment'># lower, parameter, print, punct, space, true,
-</span><span class='nx-comment'># upper, wordchar, xdigit
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># User defined value constraints are possible.
-</span><span class='nx-comment'># All parameter value checkers can be turned on
-</span><span class='nx-comment'># and off at runtime.
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># Define a required boolean property "a"
-</span><span class='nx-comment'># and an integer property "b" with a default.
-</span><span class='nx-comment'># The first definition uses "properties",
-</span><span class='nx-comment'># the second definition uses multiple
-</span><span class='nx-comment'># "property" statements.
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
- a:boolean
- {b:integer 1}
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:property</span> a:boolean
- <span class='nx-keyword'>:property</span> {b:integer 1}
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>In XOTcl all configure parameters were <em>optional</em>. Required parameters have
-to be passed to the constructor of the object.</p></div>
-<div class="paragraph"><p>NX allows one to define <em>optional</em> and <em>required</em> configure parameters (as
-well as method parameters). Therefore, configure parameters can be used
-as the single mechanism to parametrize objects. It is in NX not
-necessary (and per default not possible) to pass arguments to the
-constructor.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Required parameter not available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Required parameter:
-</span><span class='nx-comment'># Define a required property "a" and a
-</span><span class='nx-comment'># required boolean property "b"
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
- a:required
- b:boolean,required
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:property</span> a:required
- <span class='nx-keyword'>:property</span> b:boolean,required
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>NX supports in contrary to XOTcl to define the <em>multiplicity</em> of values
-per parameter. In NX, one can specify that a parameter can accept the
-value "" (empty) in addition to e.g. an integer, or one can specify that the
-value is an empty or non-empty list of values via the multiplicity. For
-every specified value, the value checkers are applied.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Multiplicity for parameter
-</span><span class='nx-comment'># not available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Parameter with multiplicity
-</span><span class='nx-comment'># ints is a list of integers, with default
-</span><span class='nx-comment'># objs is a non-empty list of objects
-</span><span class='nx-comment'># obj is a single object, maybe empty
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
- {ints:integer,0..n <span class='nx-string'>""</span>}
- objs<span class='nx-keyword'>:object</span>,1..n
- obj<span class='nx-keyword'>:object</span>,0..1
-}</pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:property</span> {ints:integer,0..n <span class='nx-string'>""</span>}
- <span class='nx-keyword'>:property</span> objs<span class='nx-keyword'>:object</span>,1..n
- <span class='nx-keyword'>:property</span> obj<span class='nx-keyword'>:object</span>,0..1
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>For the implementation of variables and properties, NX uses slot
-objects, which are an extension to the <code>-slots</code> already available in
-XOTcl. While very for every <code>property</code> in NX, a slot object is created,
-for performance reasons, not every <code>variable</code> has a slot associated.</p></div>
-<div class="paragraph"><p>When a property is created, NX does actually three things:</p></div>
-<div class="olist arabic"><ol class="arabic">
-<li>
-<p>
-Create a slot object, which can be specified in more detail
- using the init-block of the slot object
-</p>
-</li>
-<li>
-<p>
-Create a parameter definition for the initialization of the
- object (usable via a non-positional parameter during object
- creation), and
-</p>
-</li>
-<li>
-<p>
-register optionally an accessor function (setter), for which the usual
- protection levels (<code>public</code>, <code>protected</code> or <code>private</code>) can be used.
-</p>
-</li>
-</ol></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define parameters via slots
-</span>
-<span class='nx-keyword'>Class</span> Foo -slots {
- <span class='nx-keyword'>Attribute</span> a
- <span class='nx-keyword'>Attribute</span> b -default 1
-}
-
-<span class='nx-comment'># Create instance of the class Foo
-</span><span class='nx-comment'># and provide a value for instance
-</span><span class='nx-comment'># variable "a"
-</span>Foo f1 -a 0
-
-<span class='nx-comment'># Object f1 has a == 0 and b == 1</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Configurable parameters specified via the
-</span><span class='nx-comment'># method "property" (supports method
-</span><span class='nx-comment'># modifiers and scripted configuration;
-</span><span class='nx-comment'># see below)
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
- <span class='nx-keyword'>:property</span> a
- <span class='nx-keyword'>:property</span> {b 1}
-}
-
-<span class='nx-comment'># Create instance of the class Foo and
-</span><span class='nx-comment'># provide a value for instance variable "a"
-</span>Foo <span class='nx-keyword'>create</span> f1 -a 0
-
-<span class='nx-comment'># Object f1 has a == 0 and b == 1</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>Since the slots are objects, the slot objects can be configured and
-parametrized like every other object in NX. Slot objects can be
-provided with a scripted initialization as well. We show first the
-definition of properties similar to the functionality provided as well
-by XOTcl and show afterwards how to use value constraints, optional
-parameters, etc. in NX.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define parameter with an
-</span><span class='nx-comment'># attribute-specific type checker
-</span>
-<span class='nx-keyword'>Class</span> Person -slots {
- <span class='nx-keyword'>Attribute</span> <span class='nx-keyword'>create</span> sex -type <span class='nx-string'>"sex"</span> {
- <span class='nx-keyword'>my</span> <span class='nx-keyword'>proc</span> type=sex {name value} {
- <span class='nx-keyword'>switch</span> -glob <span class='nx-variable'>$value</span> {
- m* {<span class='nx-keyword'>return</span> m}
- f* {<span class='nx-keyword'>return</span> f}
- default {
- <span class='nx-keyword'>error</span> <span class='nx-string'>"expected sex but got $value"</span>
- }
- }
- }
- }
-}</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Configure parameter with scripted
-</span><span class='nx-comment'># definition (init-block), defining a
-</span><span class='nx-comment'># property specific type checker
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Person {
- <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> sex:sex,convert {
-
- <span class='nx-comment'># define a converter to standardize representation
-</span> <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> type=sex {name value} {
- <span class='nx-keyword'>switch</span> -glob <span class='nx-variable'>$value</span> {
- m* {<span class='nx-keyword'>return</span> m}
- f* {<span class='nx-keyword'>return</span> f}
- default {<span class='nx-keyword'>error</span> <span class='nx-string'>"expected sex but got $value"</span>}
- }
- }
-
- }
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>The parameters provided by a class for the initialization of
-instances can be introspected via querying the parameters
-of the method create: <code>/cls/ info lookup parameters create</code>
-(see <a href="#info_configure_parameter">[info_configure_parameter]</a>).</p></div>
-</div>
-<div class="sect3">
-<h4 id="_delete_variable_handlers">2.4.2. Delete Variable Handlers</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># No syntactic support for deleting
-</span><span class='nx-comment'># variable handlers</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Like deletion of Methods:
-</span><span class='nx-comment'># Delete on the object, where the
-</span><span class='nx-comment'># variable handler is defined.
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>property</span> <span class='nx-placeholder'>/name/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>property</span> <span class='nx-placeholder'>/name/</span>
-
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>variable</span> <span class='nx-placeholder'>/name/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>variable</span> <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_method_parameters">2.4.3. Method Parameters</h4>
-<div class="paragraph"><p>Method parameters are used to specify the interface of a single method
-(what kind of values may be passed to a method, what default values
-are provided etc.). The method parameters specifications in XOTcl 1
-were limited and allowed only value constraints for non positional
-arguments.</p></div>
-<div class="paragraph"><p>NX and XOTcl 2 provide value constraints for all kind of method parameters.
-While XOTcl 1 required non-positional arguments to be listed in front of
-positional arguments, this limitation is lifted in XOTcl 2.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define method foo with non-positional
-</span><span class='nx-comment'># parameters (x, y and y) and positional
-</span><span class='nx-comment'># parameter (a and b)
-</span>
-<span class='nx-keyword'>Class</span> C
-C instproc foo {
- -x:integer
- -y:required
- -z
- a
- b
-} {
- <span class='nx-comment'># ...
-</span>}
-C <span class='nx-keyword'>create</span> c1
-
-<span class='nx-comment'># invoke method foo
-</span>c1 foo -x 1 -y a 2 3</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define method foo with
-</span><span class='nx-comment'># non-positional parameters
-</span><span class='nx-comment'># (x, y and y) and positional
-</span><span class='nx-comment'># parameter (a and b)
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {
- -x:integer
- -y:required
- -z
- a
- b
- } {
- <span class='nx-comment'># ...
-</span> }
- <span class='nx-keyword'>:create</span> c1
-}
-<span class='nx-comment'># invoke method foo
-</span>c1 foo -x 1 -y a 2 3</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Only leading non-positional
-</span><span class='nx-comment'># parameters are available; no
-</span><span class='nx-comment'># optional positional parameters,
-</span><span class='nx-comment'># no value constraints on
-</span><span class='nx-comment'># positional parameters,
-</span><span class='nx-comment'># no multiplicity, ...</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define various forms of parameters
-</span><span class='nx-comment'># not available in XOTcl 1
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-comment'># trailing (or interleaved) non-positional
-</span> <span class='nx-comment'># parameters
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m1 {a b -x:integer -y} {
- <span class='nx-comment'># ...
-</span> }
-
- <span class='nx-comment'># positional parameters with value constraints
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m2 {a:integer b:boolean} {
- <span class='nx-comment'>#...
-</span> }
-
- <span class='nx-comment'># optional positional parameter (trailing)
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-keyword'>set</span> {varName value:optional} {
- <span class='nx-comment'># ....
-</span> }
-
- <span class='nx-comment'># parameter with multiplicity
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m3 {-objs<span class='nx-keyword'>:object</span>,1..n c<span class='nx-keyword'>:class</span>,0..1} {
- <span class='nx-comment'># ...
-</span> }
-
- <span class='nx-comment'># In general, the same list of value
-</span> <span class='nx-comment'># constraints as for configure parameter is
-</span> <span class='nx-comment'># available (see above).
-</span> <span class='nx-comment'>#
-</span> <span class='nx-comment'># User defined value constraints are
-</span> <span class='nx-comment'># possible. All parameter value checkers
-</span> <span class='nx-comment'># can be turned on and off.
-</span>}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_return_value_checking">2.4.4. Return Value Checking</h4>
-<div class="paragraph"><p><em>Return value checking</em> is a functionality available in the Next
-Scripting Framework, that was not yet available in XOTcl 1. A return
-value checker assures that a method returns always a value satisfying
-some value constraints. Return value checkers can be defined on all
-forms of methods (scripted or C-implemented). Like for other value
-checkers, return value checkers can be turned on and off.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># No return value checking
-</span><span class='nx-comment'># available</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define method foo with non-positional
-</span><span class='nx-comment'># parameters (x, y and y) and positional
-</span><span class='nx-comment'># parameter (a and b)
-</span>
-<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
-
- <span class='nx-comment'># Define method foo which returns an
-</span> <span class='nx-comment'># integer value
-</span> <span class='nx-keyword'>:method</span> foo -returns integer {-x:integer} {
- <span class='nx-comment'># ...
-</span> }
-
- <span class='nx-comment'># Define an alias for the Tcl command ::incr
-</span> <span class='nx-comment'># and assure, it always returns an integer
-</span> <span class='nx-comment'># value
-</span> <span class='nx-keyword'>:alias</span> <span class='nx-keyword'>incr</span> -returns integer ::incr
-
- <span class='nx-comment'># Define a forwarder that has to return an
-</span> <span class='nx-comment'># integer value
-</span> <span class='nx-keyword'>:forward</span> ++ -returns integer ::expr 1 +
-
- <span class='nx-comment'># Define a method that has to return a
-</span> <span class='nx-comment'># non-empty list of objects
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> instances {} \
- -returns <span class='nx-keyword'>object</span>,1..n {
- <span class='nx-keyword'>return</span> [<span class='nx-keyword'>:info</span> instances]
- }
-}</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_interceptors">2.5. Interceptors</h3>
-<div class="paragraph"><p>XOTcl and NX allow the definition of the same set of interceptors,
-namely class- and object-level mixins and class- and object-level
-filters. The primary difference in NX is the naming, since NX abandons
-the prefix "inst" from the names of instance specific method, but uses
-the modifier <code>object</code>" for object specific methods.</p></div>
-<div class="paragraph"><p>Therefore, in NX, if a <code>mixin</code> is registered on a class-level, it is
-applicable for the instances (a per-class mixin), and if and <code>object
-mixin</code> is registered, it is a per-object mixin. In both cases, the
-term <code>mixin</code> is used, in the second case with the modifier
-<code>object</code>. As in all other cases, one can register the same way a
-per-object mixin on a plain object or on a class object.</p></div>
-<div class="sect3">
-<h4 id="_register_mixin_classes_and_mixin_guards">2.5.1. Register Mixin Classes and Mixin Guards</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> instmixin ...
-<span class='nx-placeholder'>/cls/</span> instmixinguard /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
-
-<span class='nx-comment'># Query per-class mixin
-</span><span class='nx-placeholder'>/cls/</span> instmixin</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Register/clear per-class mixin and guard for
-</span><span class='nx-comment'># a class
-</span>
-<span class='nx-placeholder'>/cls/</span> mixins add|<span class='nx-keyword'>set</span>|clear ...
-<span class='nx-placeholder'>/cls/</span> mixins <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>configure</span> -mixin ...
-
-<span class='nx-comment'># Query per-class mixins
-</span><span class='nx-placeholder'>/cls/</span> mixins get
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>cget</span> -mixins
-
-<span class='nx-comment'># Query per-class mixins (without guards)
-</span><span class='nx-placeholder'>/cls/</span> mixins classes</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>mixin</span> ...
-<span class='nx-placeholder'>/obj/</span> mixinguard /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
-
-<span class='nx-comment'># Query per-object mixins
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>mixin</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Register/clear per-object mixin and guard for
-</span><span class='nx-comment'># an object
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins add|<span class='nx-keyword'>set</span>|clear ...
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>configure</span> -object-mixins ...
-
-<span class='nx-comment'># Query per-object mixin
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins get
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>cget</span> -object-mixin
-
-<span class='nx-comment'># Query per-object mixins (without guards)
-</span><span class='nx-placeholder'>/cls/</span> mixins classes</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_register_filters_and_filter_guards">2.5.2. Register Filters and Filter Guards</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Register per-class filter and guard for
-</span><span class='nx-comment'># a class
-</span><span class='nx-placeholder'>/cls/</span> instfilter ...
-<span class='nx-placeholder'>/cls/</span> instfilterguard /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
-
-<span class='nx-comment'># Query per-class filter
-</span><span class='nx-placeholder'>/cls/</span> instfilter</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Register/clear per-class filter and guard for
-</span><span class='nx-comment'># a class
-</span>
-<span class='nx-placeholder'>/cls/</span> filters add|<span class='nx-keyword'>set</span>|clear ...
-<span class='nx-placeholder'>/cls/</span> filters <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>configure</span> -filters ...
-
-<span class='nx-comment'># Query per-class filters
-</span><span class='nx-placeholder'>/cls/</span> filters get
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>cget</span> -filters
-
-<span class='nx-comment'># Query per-class filters (without guards)
-</span><span class='nx-placeholder'>/cls/</span> filters <span class='nx-keyword'>methods</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>filter</span> ...
-<span class='nx-placeholder'>/obj/</span> filterguard /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Register(clear per-object filter and guard for
-</span><span class='nx-comment'># an object
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> filters add|<span class='nx-keyword'>set</span>|clear ...
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> filters <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>configure</span> -object-filters ...
-
-<span class='nx-comment'># Query per-object filters
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span> filters get
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>cget</span> -object-filters
-
-<span class='nx-comment'># Query per-object filters (without guards)
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span> filters <span class='nx-keyword'>methods</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_introspection">2.6. Introspection</h3>
-<div class="paragraph"><p>In general, introspection in NX became more orthogonal and less
-dependent on the type of the method. In XOTcl it was e.g. necessary
-that a developer had to know, whether a method is e.g. scripted or not
-and has to use accordingly different sub-methods of <code>info</code>.</p></div>
-<div class="paragraph"><p>In NX, one can use e.g. always <code>info method</code> with a subcommand and the
-framework tries to hide the differences as far as possible. So, one
-can for example obtain with <code>info method parameter</code> the parameters of
-scripted and C-implemented methods the same way, one can get the
-definition of all methods via <code>info method definition</code> and one can get
-an manual-like interface description via <code>info method
-syntax</code>. In addition, NX provides means to query the type of
-a method, and NX allows one to filter by the type of the method.</p></div>
-<div class="sect3">
-<h4 id="_list_sub_and_superclass_relations">2.6.1. List sub- and superclass relations</h4>
-<div class="paragraph"><p>While XOTcl used singular words for introspecting sub- and superclass
-relations, NX uses plural word to indicate that potentially a list of
-values is returned.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>superclass</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> superclasses <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-</tr>
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-</div>
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-<h4 id="_list_methods_defined_by_classes">2.6.2. List methods defined by classes</h4>
-<div class="paragraph"><p>While XOTcl uses different names for obtaining different kinds of
-methods defined by a class, NX uses <code>info methods</code> in an orthogonal
-manner. NX allows as well to use the call protection to filter the
-returned methods.</p></div>
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-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
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-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
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-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type forwarder <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?pattern?</span>
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-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_methods_defined_by_objects">2.6.3. List methods defined by objects</h4>
-<div class="paragraph"><p>While XOTcl uses different names for obtaining different kinds of
-methods defined by an object, NX uses <code>info methods</code> in an orthogonal
-manner. NX allows as well to use the call protection to filter the
-returned methods.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
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-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>alias</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type forwarder <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -callprotection <span class='nx-keyword'>public</span>|<span class='nx-keyword'>protected</span> ...</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_check_existence_of_a_method">2.6.4. Check existence of a method</h4>
-<div class="paragraph"><p>NX provides multiple ways of checking, whether a method exists; one
-can use <code>info method exists</code> to check, if a given method exists
-(return boolean), or one can use <code>info methods ?pattern?</code>, where
-<code>pattern</code> might be a single method name without wild-card
-characters. The method <code>info methods ?pattern?</code> returns a list of
-matching names, which might be empty. These different methods appear
-appropriate depending on the context.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
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-<td align="left" valign="middle"><div><div class="listingblock">
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- [inst](commands|procs|parametercmd) \
- <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
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-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> exists <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_callable_methods">2.6.5. List callable methods</h4>
-<div class="paragraph"><p>In order to obtain for an object the set of artefacts defined in the
- class hierarchy, NX uses <code>info lookup</code>. One can either lookup methods
- (via <code>info lookup methods</code>) or slots (via <code>info lookup slots</code>). The
- plural term refers to a potential set of return values.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>methods</span> ... <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-comment'># Returns list of method names</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List only application specific methods
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>methods</span> -source application ... <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-comment'># Returns list of method names</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Options for 'info methods'
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># -incontext
-</span><span class='nx-comment'># -nomixins</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Options for 'info lookup methods'
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># -source ...
-</span><span class='nx-comment'># -callprotection ...
-</span><span class='nx-comment'># -incontext
-</span><span class='nx-comment'># -type ...
-</span><span class='nx-comment'># -nomixins</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List slot objects defined for obj
-</span><span class='nx-comment'># -source might be all|application|baseclasses
-</span><span class='nx-comment'># -type is the class of the slot object
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> slots <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?-source ...?</span> <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># Returns list of slot objects</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List registered filters
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> filters -order <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># List registered mixins
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> mixins -heritage <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List registered filters
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> filters <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># List registered mixins
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> mixins <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_object_class_where_a_specified_method_is_defined">2.6.6. List object/class where a specified method is defined</h4>
-<div class="paragraph"><p><code>info lookup</code> can be used as well to determine, where exactly an
- artefact is located. One can obtain this way a method handle, where
-a method or filter is defined.</p></div>
-<div class="paragraph"><p>The concept of a <em>method-handle</em> is new in NX. The method-handle
-can be used to obtain more information about the method, such as
-e.g. the definition of the method.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> procsearch <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-comment'># Returns method-handle</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> filtersearch <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>filter</span> <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-comment'># Returns method-handle</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_definition_of_scripted_methods">2.6.7. List definition of scripted methods</h4>
-<div class="paragraph"><p>XOTcl contains a long list of <code>info</code> subcommands for different kinds of
-methods and for obtaining more detailed information about these
-methods.</p></div>
-<div class="paragraph"><p>In NX, this list of <code>info</code> subcommands is much shorter and more
-orthogonal. For example <code>info method definition</code> can be used to obtain
-with a single command the full definition of a <em>scripted method</em>, and
-furthermore, it works as well the same way to obtain e.g. the
-definition of a <em>forwarder</em> or an <em>alias</em>.</p></div>
-<div class="paragraph"><p>While XOTcl uses different names for info options for objects and
-classes (using the prefix "inst" for instance specific method), NX
-uses for object specific method the modifier <code>object</code>. For definition
-of class object specific methods, use the modifier <code>object</code> as usual.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instbody <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> body <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> body <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> body <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instargs <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instnonposargs <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> parameter <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> parameter <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instdefault <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> default <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># not needed, part of
-</span><span class='nx-comment'># "info ?object? method parameter"</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instpre <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> pre <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> precondition <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> precondition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instpost <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> post <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> postcondition <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> postcondition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-<div class="paragraph"><p>Another powerful introspection option in NX is <code>info ?object? method
-syntax</code> which obtains a representation of the parameters of a
-method in the style of Tcl man pages (regardless of the kind of
-method).</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> syntax <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> syntax <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="info_configure_parameter">2.6.8. List Configure Parameters</h4>
-<div class="paragraph"><p>The way, how newly created objects can be configured is determined in NX
-via properties. The configuration happens during creation via the
-methods <code>create</code> or <code>new</code> or during runtime via <code>configure</code>. These
-methods have therefore virtual argument lists, depending on the object
-or class on which they are applied.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Return the parameters applicable to
-</span><span class='nx-comment'># the create method of a certain class.
-</span><span class='nx-comment'># class can be configured. A pattern can
-</span><span class='nx-comment'># be used to filter the results.
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> parameters <span class='nx-keyword'>create</span> ?<span class='nx-placeholder'>/pattern/</span>?
-
-<span class='nx-comment'># Return in the result in documentation syntax
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>create</span> ?<span class='nx-placeholder'>/pattern/</span>?
-
-<span class='nx-comment'># "info lookup parameters configure" returns
-</span><span class='nx-comment'># parameters available for configuring the
-</span><span class='nx-comment'># current object (might contain object
-</span><span class='nx-comment'># specific information)
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> parameters <span class='nx-keyword'>configure</span> <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># "info lookup configure syntax" returns syntax of
-</span><span class='nx-comment'># a call to configure in the Tcl parameter syntax
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
-
-<span class='nx-comment'># Obtain information from a parameter
-</span><span class='nx-comment'># (as e.g. returned from "info lookup
-</span><span class='nx-comment'># parameters configure").
-</span>
-nsf::parameter::info name <span class='nx-placeholder'>/parameter/</span>
-nsf::parameter::info syntax <span class='nx-placeholder'>/parameter/</span>
-nsf::parameter::info type <span class='nx-placeholder'>/parameter/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_variable_declarations_property_and_variable">2.6.9. List Variable Declarations (property and variable)</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># obtain parameter definitions defined
-</span><span class='nx-comment'># for a class
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> parameter</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># "info variables" returns handles of
-</span><span class='nx-comment'># properties and variables defined by this
-</span><span class='nx-comment'># class or object
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> variables <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> variables <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># "info lookup variables" returns handles
-</span><span class='nx-comment'># of variables and properties applicable
-</span><span class='nx-comment'># for the current object (might contain
-</span><span class='nx-comment'># object specific information)
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> variables <span class='nx-placeholder'>/pattern/</span>
-
-<span class='nx-comment'># "info variable" lists details about a
-</span><span class='nx-comment'># single property or variable.
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> definition <span class='nx-placeholder'>/handle/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> name <span class='nx-placeholder'>/handle/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> parameter <span class='nx-placeholder'>/handle/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_slots">2.6.10. List Slots</h4>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
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-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Return list of slots objects defined on the
-</span><span class='nx-comment'># object or class
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># -source might be all|application|baseclasses
-</span><span class='nx-comment'># -type is the class of the slot object
-</span><span class='nx-comment'># -closure includes slots of superclasses
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> slots \
- <span class='nx-placeholder'>?-type value?</span> <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?-source value?</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> slots <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?pattern?</span>
-
-<span class='nx-comment'># List reachable slot objects defined for obj
-</span><span class='nx-comment'># -source might be all|application|baseclasses
-</span><span class='nx-comment'># -type is the class of the slot object
-</span><span class='nx-comment'># Returns list of slot objects.
-</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> slots \
- <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?-source ... ?</span>pattern?
-
-<span class='nx-comment'># Obtain definition, name or parameter from
-</span><span class='nx-comment'># slot object
-</span>
-<span class='nx-placeholder'>/slotobj/</span> definition
-<span class='nx-placeholder'>/slotobj/</span> name
-<span class='nx-placeholder'>/slotobj/</span> parameter</pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_filter_or_mixins">2.6.11. List Filter or Mixins</h4>
-<div class="paragraph"><p>In NX all introspection options for filters are provided via
-<code>info filters</code> and all introspection options for mixins are
-provided via <code>info mixins</code>.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>filter</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> filterguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> filters \
- <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instfilter \
- <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instfilterguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> filters \
- <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>mixin</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order ?</span>pattern?
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> mixinguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> mixins \
- <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
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-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixin \
- <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixinguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixins \
- <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-heritage?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_definition_of_methods_defined_by_aliases_setters_or_forwarders">2.6.12. List definition of methods defined by aliases, setters or forwarders</h4>
-<div class="paragraph"><p>As mentioned earlier, <code>info method definition</code> can be used on every
-kind of method. The same call can be used to obtain the definition of
-a scripted method, a method-alias, a forwarder or a setter method.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_method_handles">2.6.13. List Method-Handles</h4>
-<div class="paragraph"><p>NX supports <em>method-handles</em> to provide means to obtain further
-information about a method or to change maybe some properties of a
-method. When a method is created, the method creating method returns
-the method handle to the created method.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
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-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># List the method handle of the specified method,
-</span><span class='nx-comment'># can be used e.g. for aliases. "handle" is the short
-</span><span class='nx-comment'># form of "definitionhandle".
-</span><span class='nx-comment'>#
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> handle <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> handle <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-comment'>#
-</span><span class='nx-comment'># For ensemble methods (method name contains
-</span><span class='nx-comment'># spaces) one can query as well the registration
-</span><span class='nx-comment'># handle, which is the handle to the root of the
-</span><span class='nx-comment'># ensemble; the definition handle points to the
-</span><span class='nx-comment'># leaf of the ensemble.
-</span><span class='nx-comment'>#
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> registrationhandle <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> registrationhandle <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-comment'>#
-</span><span class='nx-comment'># For aliases, one can query the original
-</span><span class='nx-comment'># definition via "info method origin"
-</span><span class='nx-comment'>#
-</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> origin <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> origin <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_type_of_a_method">2.6.14. List type of a method</h4>
-<div class="paragraph"><p>The method <code>info ?object? method type</code> is new in NX to obtain the type of the
-specified method.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
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-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> type <span class='nx-placeholder'>/methodName/</span>
-<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> type <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_list_the_scope_of_mixin_classes">2.6.15. List the scope of mixin classes</h4>
-<div class="paragraph"><p>NX provides a richer set of introspection options to obtain
-information, where mixins classes are mixed into.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List objects, where /cls/ is a
-</span><span class='nx-comment'># per-object mixin
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?-closure?</span> \
- <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List classes, where /cls/ is a per-class mixin
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope <span class='nx-keyword'>class</span> <span class='nx-placeholder'>?-closure?</span> \
- <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># List objects and classes, where /cls/ is
-</span><span class='nx-comment'># either a per-object or a per-class mixin
-</span>
-<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope all <span class='nx-placeholder'>?-closure?</span> \
- <span class='nx-placeholder'>?pattern?</span></pre></div></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_check_properties_of_object_and_classes">2.6.16. Check properties of object and classes</h4>
-<div class="paragraph"><p>Similar as noted before, NX uses rather a hierarchical approach of
-naming using multiple layers of subcommands).</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> istype <span class='nx-placeholder'>/sometype/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check if object is a subtype of some class
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> has type <span class='nx-placeholder'>/sometype/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> ismixin <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check if object has the specified mixin registered
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> has <span class='nx-keyword'>mixin</span> <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> isclass ?<span class='nx-placeholder'>/cls/</span>?</pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check if object is an NX class
-</span><span class='nx-placeholder'>/obj/</span> has type ::nx::Class
-
-<span class='nx-comment'># Check if object is a class in one of the
-</span><span class='nx-comment'># NSF object systems
-</span>::nsf::is <span class='nx-keyword'>class</span> <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> ismetaclass <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check if class is an NX metaclass
-</span><span class='nx-keyword'>expr</span> {[<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> heritage ::nx::Class] ne <span class='nx-string'>""</span>}
-
-<span class='nx-comment'># Check if object is a metaclass in one of the
-</span><span class='nx-comment'># NSF object systems
-</span>::nsf::is <span class='nx-keyword'>metaclass</span> <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check if object is a baseclass of an object system
-</span>::nsf::is baseclass <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Return name of object (without namespace prefix)
-</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> name</pre></div></div></div></td>
-</tr>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span>::exists <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Check for existence of object (nsf primitive)
-</span>::nsf::object::exists <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
-</tr>
-</tbody>
-</table>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_call_stack_introspection">2.6.17. Call-stack Introspection</h4>
-<div class="paragraph"><p>Call-stack introspection is very similar in NX and XOTcl. NX uses for
-subcommand the term <code>current</code> instead of <code>self</code>, since <code>self</code> has a
-strong connotation to the current object. The term <code>proc</code> is renamed
-by <code>method</code>.</p></div>
-<div class="tableblock">
-<table rules="all"
-width="100%"
-frame="void"
-cellspacing="0" cellpadding="4">
-<col width="50%" />
-<col width="50%" />
-<thead>
-<tr>
-<th align="left" valign="middle">XOTcl </th>
-<th align="left" valign="middle">Next Scripting Language</th>
-</tr>
-</thead>
-<tbody>
-<tr>
-<td align="left" valign="middle"><div><div class="listingblock">
-<div class="content"><style type='text/css'>
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-<div class="sect2">
-<h3 id="_dispatch_aliases_etc">2.8. Dispatch, Aliases, etc.</h3>
-<div class="paragraph"><p>todo: to be done or omitted</p></div>
-</div>
-<div class="sect2">
-<h3 id="_assertions">2.9. Assertions</h3>
-<div class="paragraph"><p>In contrary to XOTcl, NX provides no pre-registered methods for
-assertion handling. All assertion handling can e performed via the
-Next Scripting primitive <code>nsf::method::assertion</code>.</p></div>
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-<div class="sect2">
-<h3 id="_method_protection">2.10. Method Protection</h3>
-<div class="paragraph"><p>As described <a href="#method-protect-example">above</a>, NX supports method
-protection via the method modifiers <code>protected</code> and <code>public</code>. A
-protected method can be only called from an object of that class,
-while public methods can be called from every object. The method
-protection can be used to every kind of method, such as e.g. scripted
-methods, aliases, forwarders, or accessors. For invocations,
-the most specific definition (might be a mixin) is used for
-determining the protection.</p></div>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_incompatibilities_between_xotcl_1_and_xotcl_2">3. Incompatibilities between XOTcl 1 and XOTcl 2</h2>
-<div class="sectionbody">
-<div class="sect2">
-<h3 id="_resolvers_2">3.1. Resolvers</h3>
-<div class="paragraph"><p>The resolvers (variable resolvers, function resolvers) of the Next
-Scripting Framework are used as well within XOTcl 2. When variable
-names or method names starting with a single colon are used in XOTcl 1
-scripts, conflicts will arise with the resolver. These names must be
-replaced.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_parameters_2">3.2. Parameters</h3>
-<div class="paragraph"><p>The following changes for parameters could be regarded as bug-fixes.</p></div>
-<div class="sect3">
-<h4 id="_parameter_usage_without_a_value">3.2.1. Parameter usage without a value</h4>
-<div class="paragraph"><p>In XOTcl 1, it was possible to call a parameter method during object
-creation via the dash-interface without a value (in the example below <code>-x</code>).</p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># XOTcl example
-</span>
-<span class='nx-keyword'>Class</span> Foo -parameter {x y}
-Foo f1 -x -y 1</pre></div></div>
-<div class="paragraph"><p>Such cases are most likely mistakes. All parameter configurations in XOTcl 2 require an argument.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_ignored_parameter_definitions">3.2.2. Ignored Parameter definitions</h4>
-<div class="paragraph"><p>In XOTcl 1, a more specific parameter definition without a default was ignored
-when a more general parameter definition with a default was
-present. In the example below, the object <code>b1</code> contained in XOTcl 1
-incorrectly the parameter <code>x</code> (set via default from <code>Foo</code>), while in
-XOTcl 2, the variable won’t be set.</p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># XOTcl example
-</span>
-<span class='nx-keyword'>Class</span> Foo -parameter {{x 1}}
-<span class='nx-keyword'>Class</span> Bar -superclass Foo -parameter x
-Bar b1</pre></div></div>
-</div>
-<div class="sect3">
-<h4 id="_changing_classes_and_superclasses">3.2.3. Changing classes and superclasses</h4>
-<div class="paragraph"><p>NX does not define the methods <code>class</code> and <code>superclass</code> (like XOTcl), but allows one to
-alter all object/class relations (including
-class/superclass/object-mixin/…)
-<code>nsf::relation::set</code>. The class and superclass can be certainly queried
-in all variants with <code>info class</code> or <code>info superclasses</code>.</p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># NX example
-</span>
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo
-Foo <span class='nx-keyword'>create</span> f1
-
-<span class='nx-comment'># now alter the class of object f1
-</span>nsf::relation::set f1 <span class='nx-keyword'>class</span> ::nx::Object</pre></div></div>
-</div>
-<div class="sect3">
-<h4 id="_overwriting_procs_methods_with_objects_and_vice_versa">3.2.4. Overwriting procs/methods with objects and vice versa</h4>
-<div class="paragraph"><p>NSF is now more conservative on object/method creation. In contrary to
-XOTcl 1 NSF does not allow one to redefined a pre-existing command
-(e.g. "set") with an object and vice versa. Like in XOTcl 1,
-preexisting objects and classes con be redefined (necessary for
-reloading objects/classes in a running interpreter).</p></div>
-</div>
-<div class="sect3">
-<h4 id="_info_heritage">3.2.5. Info heritage</h4>
-<div class="paragraph"><p><code>info heritage</code> returns in XOTcl 1 the transitive superclass
-hierarchy, which is equivalent with <code>info superclasses -closure</code> and
-therefore not necessary. In XOTcl 2 (and NX), <code>info heritage</code> includes
-as well the transitive per-class mixins.</p></div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_slots">3.3. Slots</h3>
-<div class="paragraph"><p>All slot objects (also XOTcl slot objects) are now next-scripting
-objects of baseclass <code>::nx::Slot</code>. The name of the experimental
-default-setter <code>initcmd</code> was changed to <code>defaultcmd</code>. Code directly
-working on the slots objects has to be adapted.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_obsolete_commands">3.4. Obsolete Commands</h3>
-<div class="paragraph"><p>Parameter-classes were rarely used and have been replaced by the more
-general object parametrization. Therefore, <code>cl info parameterclass</code> has
-been removed.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_stronger_checking">3.5. Stronger Checking</h3>
-<div class="paragraph"><p>The Next Scripting Framework performs stronger checking than XOTcl 1
-For example, the requiredness of slots in XOTcl 1 was just a
-comment, while XOTcl 2 enforces it.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_exit_handlers">3.6. Exit Handlers</h3>
-<div class="paragraph"><p>The exit handler interface changed from a method of <code>::xotcl::Object</code>
-into the Tcl command <code>::nsf::exithandler</code>:</p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># NX example
-</span>::nsf::exithandler <span class='nx-keyword'>set</span>|get|<span class='nx-keyword'>unset</span> <span class='nx-placeholder'>?arg?</span></pre></div></div>
-</div>
-</div>
-</div>
-</div>
-<div id="footnotes"><hr /></div>
-<div id="footer">
-<div id="footer-text">
-Version 2.2.0<br />
-Last updated 2019-04-19 00:25:17 CEST
-</div>
-</div>
-</body>
-</html>
+</div>
+</div>
+<div id="content">
+<div id="preamble">
+<div class="sectionbody">
+<div class="sidebarblock">
+<div class="content">
+<div class="title">Abstract</div>
+<div class="paragraph"><p>This document describes the differences between the Next Scripting
+Language Framework and XOTcl 1. In particular, it presents a
+migration guide from XOTcl 1 to NX, and presents potential
+incompatibilities between XOTcl 1 and XOTcl 2.</p></div>
+</div></div>
+<div class="paragraph"><p>The Next Scripting Language (NX) is a successor of XOTcl 1 and is
+based on 10 years of experience with XOTcl in projects containing
+several hundert thousand lines of code. While XOTcl was the first
+language designed to provide language support for design patterns, the
+focus of the Next Scripting Framework and NX are on combining this
+with Language Oriented Programming. In many respects, NX was designed
+to ease the learning of the language by novices (by using a more
+mainstream terminology, higher orthogonality of the methods, less
+predefined methods), to improve maintainability (remove sources of
+common errors) and to encourage developer to write better structured
+programs (to provide interfaces) especially for large projects, where
+many developers are involved.</p></div>
+<div class="paragraph"><p>The Next Scripting Language is based on the Next Scripting Framework
+which was developed based on the notion of language oriented
+programming. The Next Scripting Frameworks provides C-level support
+for defining and hosting multiple object systems in a single Tcl
+interpreter. The whole definition of NX is fully scripted
+(e.g. defined in <code>nx.tcl</code>). The Next Scripting Framework is shipped
+with three language definitions, containing NX and XOTcl 2. Most of
+the existing XOTcl 1 programs can be used without modification in the
+Next Scripting Framework by using XOTcl 2. The Next Scripting
+Framework requires Tcl 8.5 or newer.</p></div>
+<div class="paragraph"><p>Although NX is fully scripted (as well as XOTcl 2), our benchmarks
+show that scripts based on NX are often 2 or 4 times faster than the
+counterparts in XOTcl 1. But speed was not the primary focus on the
+Next Scripting Environment: The goal was primarily to find ways to
+repackage the power of XOTcl in an easy to learn environment, highly
+orthogonal environment, which is better suited for large projects,
+trying to reduce maintenance costs.</p></div>
+<div class="paragraph"><p>We expect that many user will find it attractive to upgrade
+from XOTcl 1 to XOTcl 2, and some other users will upgrade to NX.
+This document focuses mainly on the differences between XOTcl 1 and
+NX, but addresses as well potential incompatibilities between XOTcl 1
+and XOTcl 2. For an introduction to NX, please consult the NX tutorial.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_differences_between_xotcl_and_nx">1. Differences Between XOTcl and NX</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The Next Scripting Framework supports <em>Language Oriented Programming</em>
+by providing means to define potentially multiple object systems with
+different naming and functionality in a single interpreter. This
+makes the Next Scripting Framework a powerful instrument for defining
+multiple languages such as e.g. domain specific languages. This focus
+differs from XOTcl 1.</p></div>
+<div class="paragraph"><p>Technically, the language framework approach means that the languages
+implemented by the Next Scripting Framework (most prominently XOTcl 2
+and NX) are typically fully scripted and can be loaded via the usual
+Tcl <code>package require</code> mechanism.</p></div>
+<div class="paragraph"><p>Some of the new features below are provided by the Next Scripting
+Framework, some are implemented via the script files for XOTcl 2 and
+NX.</p></div>
+<div class="sect2">
+<h3 id="_features_of_nx">1.1. Features of NX</h3>
+<div class="paragraph"><p>In general, the Next Scripting Language (NX) differs from XOTcl
+in the following respects:</p></div>
+<div class="olist arabic"><ol class="arabic">
+<li>
+<p>
+<strong>Stronger Encapsulation:</strong> The Next Scripting Language favors
+ a <em>stronger form of encapsulation</em> than XOTcl. Calling the own
+ methods or accessing the own instance variables is typographically
+ easier and computationally faster than these operations on other
+ objects. This behavior is achieved via <em>resolvers</em>, which make some
+ methods necessary in XOTcl 1 obsolete in NX (especially for importing
+ instance variables). The encapsulation of NX is stronger than in
+ XOTcl but still weak compared to languages like C++; a developer can
+ still access other objects' variables via some idioms, but NX <em>makes
+ accesses to other objects' variables explicit</em>. The requiredness to
+ make these accesses explicit should encourage developer to implement
+ well defined interfaces to provide access to instance variables.
+</p>
+</li>
+<li>
+<p>
+<strong>Additional Forms of Method Definition and Reuse:</strong>
+ The Next Scripting Language
+ provides much more orthogonal means to <em>define, reuse and
+ introspect</em> scripted and C-implemented methods.
+</p>
+<div class="olist loweralpha"><ol class="loweralpha">
+<li>
+<p>
+It is possible to use NX <code>alias</code> to register methods
+ under arbitrary names for arbitrary objects or classes.
+</p>
+</li>
+<li>
+<p>
+NX provides means for <em>method protection</em> (method modifiers
+ <code>public</code>, <code>protected</code>, and <code>private</code>). Therefore developers have
+ to define explicitly public interfaces in order to use methods
+ from other objects.
+</p>
+</li>
+<li>
+<p>
+One can invoke in NX fully qualified methods to invoke
+ methods outside the precedence path.
+</p>
+</li>
+<li>
+<p>
+One can define in NX <em>hierarchical method names</em> (similar to
+ commands and subcommands, called method ensembles) in a
+ convenient way to provide extensible, hierarchical naming of
+ methods.
+</p>
+</li>
+<li>
+<p>
+One can use in NX the same interface to query (introspect)
+ C-implemented and scripted methods/commands.
+</p>
+</li>
+</ol></div>
+</li>
+<li>
+<p>
+<strong>Orthogonal Parameterization:</strong>
+ The Next Scripting Language provides an <em>orthogonal framework for
+ parametrization</em> of methods and objects.
+</p>
+<div class="olist loweralpha"><ol class="loweralpha">
+<li>
+<p>
+In NX, the same argument parser is used for
+</p>
+<div class="ulist"><ul>
+<li>
+<p>
+Scripted Methods
+</p>
+</li>
+<li>
+<p>
+C-implemented methods and Tcl commands
+</p>
+</li>
+<li>
+<p>
+Object Parametrization
+</p>
+</li>
+</ul></div>
+</li>
+<li>
+<p>
+While XOTcl 1 provided only value-checkers for non-positional
+ arguments for methods, the Next Scripting Framework provides
+ the same value checkers for positional and non-positional
+ arguments of methods, as well as for positional and
+ non-positional configure parameters (<code>-parameter</code> in
+ XOTcl 1).
+</p>
+</li>
+<li>
+<p>
+While XOTcl 1 supported only non-positional arguments at the
+ begin of the argument list, these can be used now at arbitrary
+ positions.
+</p>
+</li>
+</ol></div>
+</li>
+<li>
+<p>
+<strong>Value Checking:</strong>
+</p>
+<div class="olist loweralpha"><ol class="loweralpha">
+<li>
+<p>
+The Next Scripting Language supports checking of the <em>input
+ parameters</em> and the <em>return values</em> of scripted and C-implemented
+ methods and commands.
+</p>
+</li>
+<li>
+<p>
+NX provides a set of predefined checkers (like e.g. <code>integer</code>,
+ <code>boolean</code>, <code>object</code>, …) which can be extended by the
+ applications.
+</p>
+</li>
+<li>
+<p>
+Value Checking can be used for <em>single</em> and <em>multi-valued</em>
+ parameters. One can e.g. define a list of integers
+ with at least one entry by the parameter specification
+ <code>integer,1..n</code>.
+</p>
+</li>
+<li>
+<p>
+Value Checking can be turned on/off globally or on the
+ method/command level.
+</p>
+</li>
+</ol></div>
+</li>
+<li>
+<p>
+<strong>Scripted Init Blocks:</strong> The Next Scripting Language provides
+ <em>scripted init blocks</em> for objects and classes (replacement for the
+ dangerous dash "-" mechanism in XOTcl that allows one to set variables
+ and invoke methods upon object creation).
+</p>
+</li>
+<li>
+<p>
+<strong>More Conventional Naming for Predefined Methods:</strong> The naming of
+ the methods in the Next Scripting Language is much more in line with
+ the mainstream naming conventions in OO languages. While for example
+ XOTcl uses <code>proc</code> and <code>instproc</code> for object specific and inheritable
+ methods, NX uses simply <code>method</code>.
+</p>
+</li>
+<li>
+<p>
+<strong>Profiling Support:</strong> The Next Scripting Language provides now two
+ forms of profiling
+</p>
+<div class="ulist"><ul>
+<li>
+<p>
+Profiling via a DTrace provider (examples are e.g. in the dtrace
+ subdirectory of the source tree)
+</p>
+</li>
+<li>
+<p>
+Significantly improved built-in profiling (results can be
+ processed in Tcl).
+</p>
+</li>
+</ul></div>
+</li>
+<li>
+<p>
+<strong>Significantly Improved Test Suite:</strong> The regression test suite of
+ Next Scripting Scripting framework contain now more than
+ 5.000 tests, and order of magnitude more than in XOTcl 1.6
+</p>
+</li>
+<li>
+<p>
+<strong>Much Smaller Interface:</strong> The Next Scripting Language has a much
+ <em>smaller interface</em> (i.e. provides less predefined methods) than
+ XOTcl (see Table 1), although the expressiveness was increased in
+ NX.
+</p>
+</li>
+</ol></div>
+<div class="tableblock">
+<table rules="all"
+width="50%"
+frame="hsides"
+cellspacing="0" cellpadding="4">
+<caption class="title">Table 1. Comparison of the Number of Predefined Methods in NX and XOTcl</caption>
+<col width="60%" />
+<col width="20%" />
+<col width="20%" />
+<thead>
+<tr>
+<th align="left" valign="top"></th>
+<th align="right" valign="top">NX</th>
+<th align="right" valign="top">XOTcl</th>
+</tr>
+</thead>
+<tfoot>
+<tr>
+<td align="left" valign="top"><p class="table">Total</p></td>
+<td align="right" valign="top"><p class="table">45</p></td>
+<td align="right" valign="top"><p class="table">124</p></td>
+</tr>
+</tfoot>
+<tbody>
+<tr>
+<td align="left" valign="top"><p class="table">Methods for Objects</p></td>
+<td align="right" valign="top"><p class="table">14</p></td>
+<td align="right" valign="top"><p class="table">51</p></td>
+</tr>
+<tr>
+<td align="left" valign="top"><p class="table">Methods for Classes</p></td>
+<td align="right" valign="top"><p class="table">9</p></td>
+<td align="right" valign="top"><p class="table">24</p></td>
+</tr>
+<tr>
+<td align="left" valign="top"><p class="table">Info-methods for Objects</p></td>
+<td align="right" valign="top"><p class="table">11</p></td>
+<td align="right" valign="top"><p class="table">25</p></td>
+</tr>
+<tr>
+<td align="left" valign="top"><p class="table">Info-methods for Classes</p></td>
+<td align="right" valign="top"><p class="table">11</p></td>
+<td align="right" valign="top"><p class="table">24</p></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>This comparison list compares mostly XOTcl 1 with NX, some features
+are also available in XOTcl 2 (2a, 2c 2d, 3, 4).</p></div>
+</div>
+<div class="sect2">
+<h3 id="_nx_and_xotcl_scripts">1.2. NX and XOTcl Scripts</h3>
+<div class="paragraph"><p>Below is a small, introductory example showing an implementation of a
+class <code>Stack</code> in NX and XOTcl. The purpose of this first example is
+just a quick overview. We will go into much more detailed comparison
+in the next sections.</p></div>
+<div class="paragraph"><p>NX supports a block syntax, where the methods are defined during the
+creation of the class. The XOTcl syntax is slightly more redundant,
+since every definition of a method is a single toplevel command
+starting with the class name (also NX supports the style used in
+XOTcl). In NX, all methods are per default protected (XOTcl does not
+support protection). In NX methods are defined in the definition of
+the class via <code>:method</code> or <code>:public method</code>. In XOTcl methods are
+defined via the <code>instproc</code> method.</p></div>
+<div class="paragraph"><p>Another difference is the notation to refer to instance variables. In
+NX, instance variable are named with a single colon in the front. In
+XOTcl, instance variables are imported using <code>instvar</code>.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="top">Stack example in NX </th>
+<th align="left" valign="top">Stack example in XOTcl</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="top"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Stack {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Stack of Things
+</span> <span class='nx-comment'>#
+</span>
+ <span class='nx-keyword'>:variable</span> things <span class='nx-string'>""</span>
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
+ }
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
+ <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
+ }
+}</pre></div></div></div></td>
+<td align="left" valign="top"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Stack of Things
+</span><span class='nx-comment'>#
+</span>
+<span class='nx-keyword'>Class</span> Stack
+
+Stack instproc <span class='nx-keyword'>init</span> {} {
+ <span class='nx-keyword'>my</span> instvar things
+ <span class='nx-keyword'>set</span> things <span class='nx-string'>""</span>
+}
+
+Stack instproc push {thing} {
+ <span class='nx-keyword'>my</span> instvar things
+ <span class='nx-keyword'>set</span> things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>$things</span> 0 <span class='nx-variable'>$thing</span>]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
+}
+
+Stack instproc pop {} {
+ <span class='nx-keyword'>my</span> instvar things
+ <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>$things</span> 0]
+ <span class='nx-keyword'>set</span> things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>$things</span> 1 end]
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_using_xotcl_2_0_and_the_next_scripting_language_in_a_single_interpreter">1.3. Using XOTcl 2.0 and the Next Scripting Language in a Single Interpreter</h3>
+<div class="paragraph"><p>In general, the Next Scripting Framework supports multiple object
+systems concurrently. Effectively, every object system has different
+base classes for creating objects and classes. Therefore, these object
+systems can have different interfaces and names of built-in
+methods. Currently, the Next Scripting Framework is packaged with
+three object systems:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+NX
+</p>
+</li>
+<li>
+<p>
+XOTcl 2.0
+</p>
+</li>
+<li>
+<p>
+TclCool
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>XOTcl 2 is highly compatible with XOTcl 1, the language NX is
+described below in more details, the language TclCool was introduced
+in Tip#279 and serves primarily an example of a small OO language.</p></div>
+<div class="paragraph"><p>A single Tcl interpreter can host multiple Next Scripting Object
+Systems at the same time. This fact makes migration from XOTcl to NX
+easier. The following example script shows to use XOTcl and NX in a
+single script:</p></div>
+<div class="listingblock">
+<div class="title">Using Multiple Object Systems in a single Script</div>
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>namespace</span> <span class='nx-keyword'>eval</span> mypackage {
+
+ <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> XOTcl 2.0
+
+ <span class='nx-comment'># Define a class with a public method foo using XOTcl
+</span> <span class='nx-keyword'>xotcl::Class</span> C1
+ C1 instproc foo {} {<span class='nx-keyword'>puts</span> <span class='nx-string'>"hello world"</span>}
+
+ <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
+
+ <span class='nx-comment'># Define a class with a public method foo using NX
+</span> <span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C2 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>puts</span> <span class='nx-string'>"hello world"</span>}
+ }
+}</pre></div></div>
+<div class="paragraph"><p>One could certainly create object or classes from the different object
+systems via fully qualified names (e.g. using e.g. <code>::xotcl::Class</code> or
+<code>::nx::Class</code>), but for migration for systems without explicit
+namespaces switching between the object systems eases migration.
+"Switching" between XOTcl and NX effectively means the load some
+packages (if needed) and to import either the base classes (Object and
+Class) of XOTcl or NX into the current namespace.</p></div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_xotcl_idioms_in_the_next_scripting_language">2. XOTcl Idioms in the Next Scripting Language</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>The following sections are intended for reader familiar with XOTcl and
+show, how certain language Idioms of XOTcl can be expressed in NX. In
+some cases, multiple possible realizations are listed</p></div>
+<div class="sect2">
+<h3 id="_defining_objects_and_classes">2.1. Defining Objects and Classes</h3>
+<div class="paragraph"><p>When creating objects or classes, one should use the method <code>create</code>
+explicitly. In XOTcl, a default <code>unknown</code> method handler was provided for
+classes, which create for every unknown method invocation an
+object/class with the name of the invoked method. This technique was
+convenient, but as well dangerous, since typos in method names lead
+easily to unexpected behavior. This default unknown method handler is not
+provided in NX (but can certainly be provided as a one-liner in NX by
+the application).</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> ClassName</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> ClassName</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Object</span> ObjectName</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> ObjectName</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_defining_methods">2.2. Defining Methods</h3>
+<div class="paragraph"><p>In general, both XOTcl and NX support methods on the object level
+(per-object methods, i.e. methods only applicable to a single object)
+and on the class level (methods inherited to instances of the
+classes). While the naming in XOTcl tried to follow closely the Tcl
+tradition (using the term <code>proc</code> for functions/methods), NX uses the
+term <code>method</code> for defining scripted methods.</p></div>
+<div class="paragraph"><p>XOTcl uses the prefix <code>inst</code> to denote that methods are provided for
+instances, calling therefore scripted methods for instances
+<code>instproc</code>. This is certainly an unusual term. The approach with the
+name prefix has the disadvantage, that for every different kind of
+method, two names have to be provided (e.g. <code>proc</code> and <code>instproc</code>,
+<code>forward</code> and <code>instforward</code>).</p></div>
+<div class="paragraph"><p>NX on the contrary uses the same term for defining instance method or
+object-specific methods. When the term (e.g. <code>method</code>) is used on a
+class, the method will be an instance method (i.e. applicable to the
+instances of the class). When the term is used on an object with the
+modifier <code>object</code>, an object-specific method is defined. This way one
+can define the same way object specific methods on an object as well
+as on a class.</p></div>
+<div class="paragraph"><p>Furthermore, both XOTcl and NX distinguish between scripted methods
+(section 3.2.1) and C-defined methods (section 3.2.2). Section 3.2.3
+introduces method protection, which is only supported by NX.</p></div>
+<div class="sect3">
+<h4 id="_scripted_methods_defined_in_the_init_block_of_a_class_object_or_with_separate_calls">2.2.1. Scripted Methods Defined in the Init-block of a Class/Object or with Separate Calls</h4>
+<div class="paragraph"><p>The following examples show the definition of a class and its methods
+in the init-block of a class (NX only), and the definition of methods
+via separate top level calls (XOTcl and NX).</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define instance method 'foo' and object
+</span><span class='nx-comment'># method 'bar' for a Class 'C' with separate
+</span><span class='nx-comment'># toplevel commands
+</span>
+<span class='nx-keyword'>Class</span> C
+C instproc foo args {...}
+C <span class='nx-keyword'>proc</span> bar args {...}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define instance method and object method
+</span><span class='nx-comment'># in the init-block of a class
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:method</span> foo args {...}
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> bar args {...}
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define instance method and object method
+</span><span class='nx-comment'># with separate commands
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C
+C <span class='nx-keyword'>method</span> foo args {...}
+C <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar args {...}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define object-specific method foo
+</span><span class='nx-comment'># for an object 'o' with separate commands
+</span>
+<span class='nx-keyword'>Object</span> o
+o <span class='nx-keyword'>set</span> x 1
+o <span class='nx-keyword'>proc</span> foo args {...}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define object method and set
+</span><span class='nx-comment'># instance variable in the init-block of
+</span><span class='nx-comment'># an object
+</span>
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>set</span> :x 1
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> foo args {...}
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define object method and set
+</span><span class='nx-comment'># instance variable with separate
+</span><span class='nx-comment'># commands
+</span>
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o
+o <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>set</span> :x 1}
+o <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo args {...}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_different_kinds_of_methods">2.2.2. Different Kinds of Methods</h4>
+<div class="paragraph"><p>This section describes various kinds of methods. The different kinds
+of methods are defined via different method-defining methods, which
+are summarized in the following table for XOTcl and NX.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Methods for defining methods:
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># proc
+</span><span class='nx-comment'># instproc
+</span><span class='nx-comment'># forward
+</span><span class='nx-comment'># instforward
+</span><span class='nx-comment'># parametercmd
+</span><span class='nx-comment'># instparametercmd
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># All these methods return empty.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Methods for defining methods:
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># alias
+</span><span class='nx-comment'># forward
+</span><span class='nx-comment'># method
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># All these methods return method-handles.</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>In addition to scripted methods (previous section) XOTcl supports
+forwarder (called <code>forward</code> and <code>instforward</code>) and accessor functions
+to variables (called <code>parametercmd</code> and <code>instparametercmd</code>). The
+accessor functions are used normally internally when object-specific
+parameters are defined (see Section 3.4).</p></div>
+<div class="paragraph"><p>In NX forwarders are called <code>forward</code>. NX does not provide a public
+available method to define variable accessors like <code>parametercmd</code> in
+XOTcl, but use internally the Next Scripting Framework primitive
+<code>nsf::method::setter</code> when appropriate.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> C
+C instforward f1 ...
+C <span class='nx-keyword'>forward</span> f2 ...
+
+<span class='nx-keyword'>Object</span> o
+o <span class='nx-keyword'>forward</span> f3 ...</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define forwarder
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:forward</span> f1 ...
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>forward</span> f2 ...
+}
+
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>forward</span> f3 ...
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define setter and getter methods in XOTcl.
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># XOTcl provides methods for these.
+</span>
+<span class='nx-keyword'>Class</span> C
+C instparametercmd p1
+C parametercmd p2
+
+<span class='nx-keyword'>Object</span> o
+o parametercmd p3</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define setter and getter methods in NX.
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># NX does not provide own methods, but uses
+</span><span class='nx-comment'># the low level framework commands, since
+</span><span class='nx-comment'># application developer will only
+</span><span class='nx-comment'># need it in rare cases.
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C
+::nsf::method::setter C p1
+::nsf::method::setter C -per-object p2
+
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o
+::nsf::method::setter o p3</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>NX supports in contrary to XOTcl the method <code>alias</code> which can be used
+to register arbitrary Tcl commands or methods for an object or class
+under a provided method name. Aliases can be used to reuse a certain implementation in
+e.g. different object systems under potentially different names. In
+some respects aliases are similar to forwarders, but they do not
+involve forwarding overhead.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Method "alias" not available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define method aliases
+</span><span class='nx-comment'># (to scripted or non-scripted methods)
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:alias</span> a1 ...
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>alias</span> a2 ...
+}
+
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>alias</span> a3 ...
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="method-protect-example">2.2.3. Method Modifiers and Method Protection</h4>
+<div class="paragraph"><p>NX supports four method modifiers <code>object</code>, <code>public</code>, <code>protected</code> and
+<code>private</code>. All method modifiers can be written in front of every
+method defining command. The method modifier <code>object</code> is used to denote
+object-specific methods (see above). The concept of method protection
+is new in NX.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Method modifiers
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># "object",
+</span><span class='nx-comment'># "public",
+</span><span class='nx-comment'># "protected", and
+</span><span class='nx-comment'># "private"
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># are not available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Method modifiers
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># "object",
+</span><span class='nx-comment'># "public",
+</span><span class='nx-comment'># "protected"
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># are applicable for all kinds of
+</span><span class='nx-comment'># method defining methods:
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># method, forward, alias
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># The modifier "private" is available for
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># method, forward, alias
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ :/<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:public</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:protected</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:private</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:protected</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+ <span class='nx-keyword'>:private</span> <span class='nx-keyword'>object</span> /<span class='nx-keyword'>method</span>-definition-method/ ...
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>XOTcl does not provide method protection. In NX, all methods are
+defined per default as protected. This default can be changed by the
+application developer in various ways. The command <code>::nx::configure
+defaultMethodCallProtection true|false</code> can be used to set the default
+call protection for scripted methods, forwarder and aliases.
+The defaults can be overwritten also on a class level.</p></div>
+<div class="paragraph"><p>NX provides means for method hiding via the method modifier
+<code>private</code>. Hidden methods can be invoked only via the <code>-local</code> flag,
+which means: "call the specified method defined in the same
+class/object as the currently executing method".</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># XOTcl provides no means for
+</span><span class='nx-comment'># method hiding</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Hiding of methods via "private"
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
+ <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> baz {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> + <span class='nx-variable'>$b</span>}}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a b} {: -local baz <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Sub -superclass Base {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a b} {: -local baz <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
+ <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> baz {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> * <span class='nx-variable'>$b</span>}}
+
+ <span class='nx-keyword'>:create</span> s1
+}
+
+s1 foo 3 4 ;<span class='nx-comment'># returns 7
+</span>s1 bar 3 4 ;<span class='nx-comment'># returns 12
+</span>s1 baz 3 4 ;<span class='nx-comment'># unable to dispatch method 'baz'</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="method-deletion">2.2.4. Method Deletion</h4>
+<div class="paragraph"><p>NX provides an explicit <code>delete</code> method for the deletion of methods.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># XOTcl provides only method deletion with
+</span><span class='nx-comment'># the equivalent of Tcl's "proc foo {} {}"
+</span><span class='nx-placeholder'>/cls/</span> instproc foo {} {}
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>proc</span> foo {} {}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Deletion of Methods
+</span><span class='nx-comment'>#
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/name/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_resolvers">2.3. Resolvers</h3>
+<div class="paragraph"><p>The Next Scripting Framework defines Tcl resolvers for method and
+variable names to implement object specific behavior. Within the
+bodies of scripted methods these resolver treat variable and function
+names starting with a colon <code>:</code> specially. In short, a colon-prefixed
+variable name refers to an instance variable, and a colon-prefixed
+function name refers to a method. The sub-sections below provide
+detailed examples.</p></div>
+<div class="paragraph"><p>Note that the resolvers of the Next Scripting Framework can be used in
+the XOTcl 2.* environment as well.</p></div>
+<div class="sect3">
+<h4 id="_invoking_methods">2.3.1. Invoking Methods</h4>
+<div class="paragraph"><p>In XOTcl, a method of the same object can be invoked via <code>my</code>, or in
+general via using the name of the object in front of the method name.</p></div>
+<div class="paragraph"><p>In NX, the own methods are called via the method name prefixed with a
+single colon. The invocation of the methods of other objects is the
+same in NX and XOTcl.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> C
+C instproc foo args {...}
+C instproc bar args {
+ <span class='nx-keyword'>my</span> foo 1 2 3 ;<span class='nx-comment'># invoke own method
+</span> o baz ;<span class='nx-comment'># invoke other object's method
+</span>}
+<span class='nx-keyword'>Object</span> o
+o <span class='nx-keyword'>proc</span> baz {} {...}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:method</span> foo args {...}
+ <span class='nx-keyword'>:method</span> bar args {
+ :foo 1 2 3 ;<span class='nx-comment'># invoke own method
+</span> o baz ;<span class='nx-comment'># invoke other object's method
+</span> }
+}
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {} {...}
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_accessing_own_instance_variables_from_method_bodies">2.3.2. Accessing Own Instance Variables from Method Bodies</h4>
+<div class="paragraph"><p>In general, the Next Scripting Language favors the access to an
+objects’s own instance variables over variable accesses of other
+objects. This means that in NX it is syntactically easier to access
+the own instance variables. On the contrary, in XOTcl, the variable
+access to own and other variables are fully symmetric.</p></div>
+<div class="paragraph"><p>In XOTcl, the following approaches are used to access instance
+variables:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+Import instance variables via <code>instvar</code> and access variables via <code>$varName</code>
+</p>
+</li>
+<li>
+<p>
+Set or get instance variables via <code>my set varName ?value?</code> or other
+ variable accessing methods registered on <code>xotcl::Object</code> such as
+ <code>append</code>, <code>lappend</code>, <code>incr</code>, etc.
+</p>
+</li>
+<li>
+<p>
+Register same-named accessor functions and set/get values
+ of instance variables via <code>my varName ?value?</code>
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>In NX, the favored approach to access instance variables is to use
+the name resolvers, although it is as well possible to import
+variables via <code>nx::var import</code> or to check for the existence of
+instance variables via <code>nx::var exists</code>.</p></div>
+<div class="paragraph"><p>The following examples summary the use cases for accessing the own and
+other instance variables.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> C
+C instproc foo args {
+ <span class='nx-comment'># Method scoped variable a
+</span> <span class='nx-keyword'>set</span> a 1
+ <span class='nx-comment'># Instance variable b
+</span> <span class='nx-keyword'>my</span> instvar b
+ <span class='nx-keyword'>set</span> b 2
+ <span class='nx-comment'># Global variable/namespaced variable c
+</span> <span class='nx-keyword'>set</span> ::c 3
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:method</span> foo args {...}
+ <span class='nx-comment'># Method scoped variable a
+</span> <span class='nx-keyword'>set</span> a 1
+ <span class='nx-comment'># Instance variable b
+</span> <span class='nx-keyword'>set</span> :b 2
+ <span class='nx-comment'># Global variable/namespaced variable c
+</span> <span class='nx-keyword'>set</span> ::c 3
+ }
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... instproc ... {
+ <span class='nx-keyword'>my</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Set own instance variable to a value via
+</span><span class='nx-comment'># resolver (preferred and fastest way)
+</span>
+... <span class='nx-keyword'>method</span> ... {
+ <span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/newVar/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... instproc ... {
+ <span class='nx-keyword'>my</span> instvar <span class='nx-placeholder'>/varName/</span>
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Set own instance variable via
+</span><span class='nx-comment'># variable import
+</span>
+... <span class='nx-keyword'>method</span> ... {
+ ::nx::var import [<span class='nx-keyword'>self</span>] <span class='nx-placeholder'>/varName/</span>
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... instproc ... {
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-keyword'>my</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/otherVar/</span>]
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Read own instance variable
+</span>
+... <span class='nx-keyword'>method</span> ... {
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/otherVar/</span>]
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... <span class='nx-keyword'>method</span> ... {
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/newVar/</span> <span class='nx-variable'>${</span><span class='nx-variable'>:/otherVar/}</span>
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... instproc ... {
+ <span class='nx-keyword'>my</span> exists <span class='nx-placeholder'>/varName/</span>
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Test existence of own instance variable
+</span>
+... <span class='nx-keyword'>method</span> ... {
+ <span class='nx-keyword'>info</span> :<span class='nx-placeholder'>/varName/</span>
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'> ... <span class='nx-keyword'>method</span> ... {
+ ::nx::var exists [<span class='nx-keyword'>self</span>] <span class='nx-placeholder'>/varName/</span>
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_accessing_instance_variables_of_other_objects">2.3.3. Accessing Instance Variables of other Objects</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Set instance variable of object obj to a
+</span><span class='nx-comment'># value via resolver
+</span><span class='nx-comment'># (preferred way: define property on obj)
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> [<span class='nx-keyword'>list</span> <span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>]</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/otherVar/</span>]</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Read instance variable of object obj
+</span><span class='nx-comment'># via resolver
+</span>
+<span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> [<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>set</span> :<span class='nx-placeholder'>/otherVar/</span>}]</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>... instproc ... {
+ <span class='nx-placeholder'>/obj/</span> instvar <span class='nx-placeholder'>/varName/</span>
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Read instance variable of object /obj/
+</span><span class='nx-comment'># via import
+</span>
+... <span class='nx-keyword'>method</span> ... {
+ ::nx::var import <span class='nx-placeholder'>/obj/</span> <span class='nx-placeholder'>/varName/</span>
+ <span class='nx-keyword'>set</span> <span class='nx-placeholder'>/varName/</span> <span class='nx-placeholder'>?value?</span>
+}</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> exists varName</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Test existence of instance variable of
+</span><span class='nx-comment'># object obj
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>eval</span> {<span class='nx-keyword'>info</span> exists :<span class='nx-placeholder'>/varName/</span>}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nx::var exists <span class='nx-placeholder'>/obj/</span> <span class='nx-placeholder'>/varName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_parameters">2.4. Parameters</h3>
+<div class="paragraph"><p>While XOTcl 1 had very limited forms of parameters, XOTcl 2 and NX
+provide a generalized and highly orthogonal parameter machinery
+handling various kinds of value constraints (also called value
+checkers). Parameters are used to specify,</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+how objects and classes are initialized (we call these parameter types
+ <em>Configure Parameters</em>), and
+</p>
+</li>
+<li>
+<p>
+what values can be passed to methods (we call these <em>Method
+ Parameters</em>).
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>Furthermore, parameters might be positional or non-positional, they
+might be optional or required, they might have a defined multiplicity,
+and value-types, they might be introspected, etc. The Next Scripting
+Framework provide a unified, C-implemented infrastructure to handle
+both, object and method parameters in the same way with a high degree
+of orthogonality.</p></div>
+<div class="paragraph"><p>Configuration parameters were specified in XOTcl 1 primarily via the
+method <code>parameter</code> in a rather limited way, XOTcl 1 only supported
+non-positional parameters in front of positional ones, supported no
+value constraints for positional parameters, provided no distinction
+between optional and required, and did not support multiplicity.</p></div>
+<div class="paragraph"><p>Furthermore, the Next Scripting Framework provides optionally <em>Return
+Value Checking</em> based on the same mechanism to check whether some
+methods return always the values as specified.</p></div>
+<div class="sect3">
+<h4 id="_parameters_for_configuring_objects_variables_and_properties">2.4.1. Parameters for Configuring Objects: Variables and Properties</h4>
+<div class="paragraph"><p>Configure parameters are used for specifying values for configuring
+objects when they are created (i.e. how instance variables are
+initialized, what parameters can be passed in for initialization, what
+default values are used, etc.). Such configuration parameters are
+supported in XOTcl primarily via the method <code>parameter</code>, which is used
+in XOTcl to define multiple parameters via a list of parameter
+specifications.</p></div>
+<div class="paragraph"><p>Since the term "parameter" is underspecified, NX uses a more
+differentiated terminology. NX distinguishes between configurable
+instance variables (also called <em>properties</em>) and non configurable
+instance variables (called <em>variables</em>), which might have as well
+e.g. default values. The values of configurable properties can be
+queried at runtime via <code>cget</code>, and their values can be altered via
+<code>configure</code>. When the value of a configure parameter is provided or
+changed, the value checkers from the variable definition are used to
+ensure, the value is permissible (i.e. it is for example an integer
+value). The sum of all configurable object parameters are called
+<em>configure parameters</em>. To define a define a configurable variable, NX
+uses the method <code>property</code>, for non-configurable variables, the method
+<code>variable</code> is used.</p></div>
+<div class="paragraph"><p>Optionally, one can define in NX, that a <code>property</code> or a
+<code>variable</code> should have a public, protected or private accessor. Such
+an accessor is a method with the same name as the variable. In XOTcl,
+every <code>parameter</code> defined as well automatically a same-named accessor
+method, leading to potential name conflicts with other method names.</p></div>
+<div class="paragraph"><p>In the examples below we show the definition of configurable a non-configurable instance variables using <code>variable</code> and <code>property</code>
+respectively.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define class "Foo" with instance
+</span><span class='nx-comment'># variables "x" and "y" initialized
+</span><span class='nx-comment'># on instance creation. The initialization
+</span><span class='nx-comment'># has to be performed in the constructor.
+</span>
+<span class='nx-keyword'>Class</span> Foo
+Foo instproc <span class='nx-keyword'>init</span> args {
+ instvar x y
+ <span class='nx-keyword'>set</span> x 1
+ <span class='nx-keyword'>set</span> y 2
+}
+
+<span class='nx-comment'># Create instance of the class Foo
+</span>Foo f1
+
+<span class='nx-comment'># Object f1 has instance variables
+</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define class "Foo" with instance variables
+</span><span class='nx-comment'># "x" and "y" initialized on instance creation.
+</span><span class='nx-comment'># The method "variable" is similar in syntax
+</span><span class='nx-comment'># to Tcl's "variable" command. During
+</span><span class='nx-comment'># instance creation, the variable
+</span><span class='nx-comment'># definitions are used for the
+</span><span class='nx-comment'># initialization of the variables of the object.
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:variable</span> x 1
+ <span class='nx-keyword'>:variable</span> y 2
+}
+
+<span class='nx-comment'># Create instance of the class Foo
+</span>Foo <span class='nx-keyword'>create</span> f1
+
+<span class='nx-comment'># Object f1 has instance variables
+</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>While XOTcl follows a procedural way to initialize variables via the
+constructor <code>init</code>, NX follows a more declarative approach. Often,
+classes have superclasses, which often want to provide their own
+instance variables and default values. The declarative approach from
+NX solves this via inheritance, while a procedural approach via
+assign statements in the constructor requires explicit constructor
+calls, which are often error-prone. Certainly, when a user prefers to
+assign initial values to instance variables via explicit assign
+operations in constructors, this is as well possible in NX.</p></div>
+<div class="paragraph"><p>NX uses the same mechanism to define class variables or object
+variables.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># No syntactic support for creating
+</span><span class='nx-comment'># class variables</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>
+<span class='nx-comment'># Define a object variable "V" with value 100 and
+</span><span class='nx-comment'># an instance variable "x". "V" is defined for the
+</span><span class='nx-comment'># class object Foo, "x" is defined in the
+</span><span class='nx-comment'># instances of the class. "object variable" works
+</span><span class='nx-comment'># similar to "object method".
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>variable</span> V 100
+ <span class='nx-keyword'>:variable</span> x 1
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>In the next step, we define configurable instance variables which we
+call <em>properties</em> in NX.</p></div>
+<div class="paragraph"><p>XOTcl uses the method <code>parameter</code> is a shortcut for creating multiple
+configurable variables with automatically created accessors (methods for
+reading and writing of the variables). In NX, the preferred way to
+create configurable variables is to use the method <code>property</code>. The
+method <code>property</code> in NX is similar to <code>variable</code>, but makes the
+variables configurable, which means that</p></div>
+<div class="olist arabic"><ol class="arabic">
+<li>
+<p>
+one can specify the property as a non-positional parameter upon
+ creation of the object,
+</p>
+</li>
+<li>
+<p>
+one can query the value via the method <code>cget</code>, and
+</p>
+</li>
+<li>
+<p>
+one can modify the value of the underlying variable via the method
+ <code>configure</code>.
+</p>
+</li>
+</ol></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Parameters specified as a list
+</span><span class='nx-comment'># (short form); parameter
+</span><span class='nx-comment'># "a" has no default, "b" has default "1"
+</span>
+<span class='nx-keyword'>Class</span> Foo -parameter {a {b 1} {c <span class='nx-string'>"[info tclversion]"</span>}}
+
+<span class='nx-comment'># Create instance of the class Foo
+</span>Foo f1 -a 0
+
+<span class='nx-comment'># Object f1 has instance variables
+</span><span class='nx-comment'># a == 0 and b == 1
+</span>
+<span class='nx-comment'># XOTcl registers automatically accessors
+</span><span class='nx-comment'># for the parameters. Use the accessor
+</span><span class='nx-comment'># "b" to output the value of variable "b"
+</span><span class='nx-keyword'>puts</span> [f1 b]
+
+<span class='nx-comment'># Use the setter to alter value of
+</span><span class='nx-comment'># instance variable "b"
+</span>f1 b 100
+
+<span class='nx-comment'># Return the substituted value of
+</span><span class='nx-comment'># parameter "c", something like 8.7.
+</span><span class='nx-comment'># XOTcl substitutes always when it sees
+</span><span class='nx-comment'># square brackets or dollar signs.
+</span>f1 c
+</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define property "a" and "b". The
+</span><span class='nx-comment'># property "a" has no default, "b" has
+</span><span class='nx-comment'># default value "1"
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:property</span> a
+ <span class='nx-keyword'>:property</span> {b 1}
+ <span class='nx-keyword'>:property</span> {c <span class='nx-string'>"[info tclversion]"</span>}
+ <span class='nx-keyword'>:property</span> {d:substdefault <span class='nx-string'>"[info tclversion]"</span>}
+}
+
+<span class='nx-comment'># Create instance of the class Foo
+</span>Foo <span class='nx-keyword'>create</span> f1 -a 0
+
+<span class='nx-comment'># Object f1 has instance variables
+</span><span class='nx-comment'># a == 0 and b == 1
+</span>
+<span class='nx-comment'># Use the method "cget" to query the value
+</span><span class='nx-comment'># of a configuration parameter
+</span><span class='nx-keyword'>puts</span> [f1 <span class='nx-keyword'>cget</span> -b]
+
+<span class='nx-comment'># Use the method "configure" to alter the
+</span><span class='nx-comment'># value of instance variable "b"
+</span>f1 <span class='nx-keyword'>configure</span> -b 100
+
+<span class='nx-comment'># Return the (non substituted) value of
+</span><span class='nx-comment'># parameter "c", and the substituted value
+</span><span class='nx-comment'># of parameter "d"
+</span>f1 <span class='nx-keyword'>cget</span> -c
+f1 <span class='nx-keyword'>cget</span> -d
+</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>In general, NX allows one to create variables and properties with and
+without accessor methods. The created accessor methods might be
+<code>public</code>, <code>protected</code> or <code>public</code>. When the value <code>none</code> is provided
+to <code>-accessor</code>, no accessor will be created. This is actually the
+default in NX. In order to change the default behavior in NX, one can use
+<code>::nx::configure defaultAccessor none|public|protected|private</code>.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># "parameter" creates always accessor
+</span><span class='nx-comment'># methods, accessor methods are
+</span><span class='nx-comment'># always public, no "cget" is available.
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -parameter {a {b 1}}
+
+<span class='nx-comment'># Use the accessor method to query
+</span><span class='nx-comment'># the value of a configuration parameter
+</span><span class='nx-keyword'>puts</span> [f1 b]
+
+<span class='nx-comment'># Use the accessor method to set the
+</span><span class='nx-comment'># value of instance variable "a"
+</span>f1 a 100
+
+<span class='nx-comment'># Use the accessor method to unset the
+</span><span class='nx-comment'># value of instance variable "a" n.a. via
+</span><span class='nx-comment'># accessor</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define property "a" and "b". The
+</span><span class='nx-comment'># property "a" has no default, "b" has
+</span><span class='nx-comment'># default value "1"
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:variable</span> -accessor <span class='nx-keyword'>public</span> a
+ <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {b 1}
+}
+
+<span class='nx-comment'># Use the accessor method to query
+</span><span class='nx-comment'># the value of a configuration parameter
+</span><span class='nx-keyword'>puts</span> [f1 b get]
+
+<span class='nx-comment'># Use the accessor method to set the
+</span><span class='nx-comment'># value of instance variable "a"
+</span>f1 a <span class='nx-keyword'>set</span> 100
+
+<span class='nx-comment'># Use the accessor method to unset the
+</span><span class='nx-comment'># value of instance variable "a"
+</span>f1 a <span class='nx-keyword'>unset</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>Similar to <code>variable</code>, properties can be defined in NX on the class
+and on the object level.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># XOTcl provides no means to define
+</span><span class='nx-comment'># configurable variables at the object
+</span><span class='nx-comment'># level</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define class with a property for the class object
+</span><span class='nx-comment'># named "cp". This is similar to "static variables"
+</span><span class='nx-comment'># in some other object-oriented programming
+</span><span class='nx-comment'># languages.
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ ...
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>property</span> cp 101
+}
+
+<span class='nx-comment'># Define object property "op"
+</span>
+<span class='nx-keyword'>Object</span> <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>property</span> op 102
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>NX supports <em>value constraints</em> (value-checkers) for object and method
+parameters in an orthogonal manner. NX provides a predefined set of
+value checkers, which can be extended by the application developer.
+In NX, the <em>value checking is optional</em>. This means that it is possible to
+develop e.g. which a large amount of value-checking and deploy the
+script with value checking turned off, if the script is highly
+performance sensitive.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># No value constraints for
+</span><span class='nx-comment'># parameter available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Predefined value constraints:
+</span><span class='nx-comment'># object, class, alnum, alpha, ascii, boolean,
+</span><span class='nx-comment'># control, digit, double, false, graph, integer,
+</span><span class='nx-comment'># lower, parameter, print, punct, space, true,
+</span><span class='nx-comment'># upper, wordchar, xdigit
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># User defined value constraints are possible.
+</span><span class='nx-comment'># All parameter value checkers can be turned on
+</span><span class='nx-comment'># and off at runtime.
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># Define a required boolean property "a"
+</span><span class='nx-comment'># and an integer property "b" with a default.
+</span><span class='nx-comment'># The first definition uses "properties",
+</span><span class='nx-comment'># the second definition uses multiple
+</span><span class='nx-comment'># "property" statements.
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
+ a:boolean
+ {b:integer 1}
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:property</span> a:boolean
+ <span class='nx-keyword'>:property</span> {b:integer 1}
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>In XOTcl all configure parameters were <em>optional</em>. Required parameters have
+to be passed to the constructor of the object.</p></div>
+<div class="paragraph"><p>NX allows one to define <em>optional</em> and <em>required</em> configure parameters (as
+well as method parameters). Therefore, configure parameters can be used
+as the single mechanism to parametrize objects. It is in NX not
+necessary (and per default not possible) to pass arguments to the
+constructor.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Required parameter not available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Required parameter:
+</span><span class='nx-comment'># Define a required property "a" and a
+</span><span class='nx-comment'># required boolean property "b"
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
+ a:required
+ b:boolean,required
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:property</span> a:required
+ <span class='nx-keyword'>:property</span> b:boolean,required
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>NX supports in contrary to XOTcl to define the <em>multiplicity</em> of values
+per parameter. In NX, one can specify that a parameter can accept the
+value "" (empty) in addition to e.g. an integer, or one can specify that the
+value is an empty or non-empty list of values via the multiplicity. For
+every specified value, the value checkers are applied.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Multiplicity for parameter
+</span><span class='nx-comment'># not available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Parameter with multiplicity
+</span><span class='nx-comment'># ints is a list of integers, with default
+</span><span class='nx-comment'># objs is a non-empty list of objects
+</span><span class='nx-comment'># obj is a single object, maybe empty
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo -properties {
+ {ints:integer,0..n <span class='nx-string'>""</span>}
+ objs<span class='nx-keyword'>:object</span>,1..n
+ obj<span class='nx-keyword'>:object</span>,0..1
+}</pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:property</span> {ints:integer,0..n <span class='nx-string'>""</span>}
+ <span class='nx-keyword'>:property</span> objs<span class='nx-keyword'>:object</span>,1..n
+ <span class='nx-keyword'>:property</span> obj<span class='nx-keyword'>:object</span>,0..1
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>For the implementation of variables and properties, NX uses slot
+objects, which are an extension to the <code>-slots</code> already available in
+XOTcl. While very for every <code>property</code> in NX, a slot object is created,
+for performance reasons, not every <code>variable</code> has a slot associated.</p></div>
+<div class="paragraph"><p>When a property is created, NX does actually three things:</p></div>
+<div class="olist arabic"><ol class="arabic">
+<li>
+<p>
+Create a slot object, which can be specified in more detail
+ using the init-block of the slot object
+</p>
+</li>
+<li>
+<p>
+Create a parameter definition for the initialization of the
+ object (usable via a non-positional parameter during object
+ creation), and
+</p>
+</li>
+<li>
+<p>
+register optionally an accessor function (setter), for which the usual
+ protection levels (<code>public</code>, <code>protected</code> or <code>private</code>) can be used.
+</p>
+</li>
+</ol></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define parameters via slots
+</span>
+<span class='nx-keyword'>Class</span> Foo -slots {
+ <span class='nx-keyword'>Attribute</span> a
+ <span class='nx-keyword'>Attribute</span> b -default 1
+}
+
+<span class='nx-comment'># Create instance of the class Foo
+</span><span class='nx-comment'># and provide a value for instance
+</span><span class='nx-comment'># variable "a"
+</span>Foo f1 -a 0
+
+<span class='nx-comment'># Object f1 has a == 0 and b == 1</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Configurable parameters specified via the
+</span><span class='nx-comment'># method "property" (supports method
+</span><span class='nx-comment'># modifiers and scripted configuration;
+</span><span class='nx-comment'># see below)
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Foo {
+ <span class='nx-keyword'>:property</span> a
+ <span class='nx-keyword'>:property</span> {b 1}
+}
+
+<span class='nx-comment'># Create instance of the class Foo and
+</span><span class='nx-comment'># provide a value for instance variable "a"
+</span>Foo <span class='nx-keyword'>create</span> f1 -a 0
+
+<span class='nx-comment'># Object f1 has a == 0 and b == 1</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>Since the slots are objects, the slot objects can be configured and
+parametrized like every other object in NX. Slot objects can be
+provided with a scripted initialization as well. We show first the
+definition of properties similar to the functionality provided as well
+by XOTcl and show afterwards how to use value constraints, optional
+parameters, etc. in NX.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define parameter with an
+</span><span class='nx-comment'># attribute-specific type checker
+</span>
+<span class='nx-keyword'>Class</span> Person -slots {
+ <span class='nx-keyword'>Attribute</span> <span class='nx-keyword'>create</span> sex -type <span class='nx-string'>"sex"</span> {
+ <span class='nx-keyword'>my</span> <span class='nx-keyword'>proc</span> type=sex {name value} {
+ <span class='nx-keyword'>switch</span> -glob <span class='nx-variable'>$value</span> {
+ m* {<span class='nx-keyword'>return</span> m}
+ f* {<span class='nx-keyword'>return</span> f}
+ default {
+ <span class='nx-keyword'>error</span> <span class='nx-string'>"expected sex but got $value"</span>
+ }
+ }
+ }
+ }
+}</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Configure parameter with scripted
+</span><span class='nx-comment'># definition (init-block), defining a
+</span><span class='nx-comment'># property specific type checker
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> Person {
+ <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> sex:sex,convert {
+
+ <span class='nx-comment'># define a converter to standardize representation
+</span> <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> type=sex {name value} {
+ <span class='nx-keyword'>switch</span> -glob <span class='nx-variable'>$value</span> {
+ m* {<span class='nx-keyword'>return</span> m}
+ f* {<span class='nx-keyword'>return</span> f}
+ default {<span class='nx-keyword'>error</span> <span class='nx-string'>"expected sex but got $value"</span>}
+ }
+ }
+
+ }
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>The parameters provided by a class for the initialization of
+instances can be introspected via querying the parameters
+of the method create: <code>/cls/ info lookup parameters create</code>
+(see <a href="#info_configure_parameter">[info_configure_parameter]</a>).</p></div>
+</div>
+<div class="sect3">
+<h4 id="_delete_variable_handlers">2.4.2. Delete Variable Handlers</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># No syntactic support for deleting
+</span><span class='nx-comment'># variable handlers</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Like deletion of Methods:
+</span><span class='nx-comment'># Delete on the object, where the
+</span><span class='nx-comment'># variable handler is defined.
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>property</span> <span class='nx-placeholder'>/name/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>property</span> <span class='nx-placeholder'>/name/</span>
+
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>variable</span> <span class='nx-placeholder'>/name/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>delete</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>variable</span> <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_method_parameters">2.4.3. Method Parameters</h4>
+<div class="paragraph"><p>Method parameters are used to specify the interface of a single method
+(what kind of values may be passed to a method, what default values
+are provided etc.). The method parameters specifications in XOTcl 1
+were limited and allowed only value constraints for non positional
+arguments.</p></div>
+<div class="paragraph"><p>NX and XOTcl 2 provide value constraints for all kind of method parameters.
+While XOTcl 1 required non-positional arguments to be listed in front of
+positional arguments, this limitation is lifted in XOTcl 2.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define method foo with non-positional
+</span><span class='nx-comment'># parameters (x, y and y) and positional
+</span><span class='nx-comment'># parameter (a and b)
+</span>
+<span class='nx-keyword'>Class</span> C
+C instproc foo {
+ -x:integer
+ -y:required
+ -z
+ a
+ b
+} {
+ <span class='nx-comment'># ...
+</span>}
+C <span class='nx-keyword'>create</span> c1
+
+<span class='nx-comment'># invoke method foo
+</span>c1 foo -x 1 -y a 2 3</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define method foo with
+</span><span class='nx-comment'># non-positional parameters
+</span><span class='nx-comment'># (x, y and y) and positional
+</span><span class='nx-comment'># parameter (a and b)
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {
+ -x:integer
+ -y:required
+ -z
+ a
+ b
+ } {
+ <span class='nx-comment'># ...
+</span> }
+ <span class='nx-keyword'>:create</span> c1
+}
+<span class='nx-comment'># invoke method foo
+</span>c1 foo -x 1 -y a 2 3</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Only leading non-positional
+</span><span class='nx-comment'># parameters are available; no
+</span><span class='nx-comment'># optional positional parameters,
+</span><span class='nx-comment'># no value constraints on
+</span><span class='nx-comment'># positional parameters,
+</span><span class='nx-comment'># no multiplicity, ...</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define various forms of parameters
+</span><span class='nx-comment'># not available in XOTcl 1
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-comment'># trailing (or interleaved) non-positional
+</span> <span class='nx-comment'># parameters
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m1 {a b -x:integer -y} {
+ <span class='nx-comment'># ...
+</span> }
+
+ <span class='nx-comment'># positional parameters with value constraints
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m2 {a:integer b:boolean} {
+ <span class='nx-comment'>#...
+</span> }
+
+ <span class='nx-comment'># optional positional parameter (trailing)
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-keyword'>set</span> {varName value:optional} {
+ <span class='nx-comment'># ....
+</span> }
+
+ <span class='nx-comment'># parameter with multiplicity
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> m3 {-objs<span class='nx-keyword'>:object</span>,1..n c<span class='nx-keyword'>:class</span>,0..1} {
+ <span class='nx-comment'># ...
+</span> }
+
+ <span class='nx-comment'># In general, the same list of value
+</span> <span class='nx-comment'># constraints as for configure parameter is
+</span> <span class='nx-comment'># available (see above).
+</span> <span class='nx-comment'>#
+</span> <span class='nx-comment'># User defined value constraints are
+</span> <span class='nx-comment'># possible. All parameter value checkers
+</span> <span class='nx-comment'># can be turned on and off.
+</span>}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_return_value_checking">2.4.4. Return Value Checking</h4>
+<div class="paragraph"><p><em>Return value checking</em> is a functionality available in the Next
+Scripting Framework, that was not yet available in XOTcl 1. A return
+value checker assures that a method returns always a value satisfying
+some value constraints. Return value checkers can be defined on all
+forms of methods (scripted or C-implemented). Like for other value
+checkers, return value checkers can be turned on and off.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># No return value checking
+</span><span class='nx-comment'># available</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define method foo with non-positional
+</span><span class='nx-comment'># parameters (x, y and y) and positional
+</span><span class='nx-comment'># parameter (a and b)
+</span>
+<span class='nx-keyword'>Class</span> <span class='nx-keyword'>create</span> C {
+
+ <span class='nx-comment'># Define method foo which returns an
+</span> <span class='nx-comment'># integer value
+</span> <span class='nx-keyword'>:method</span> foo -returns integer {-x:integer} {
+ <span class='nx-comment'># ...
+</span> }
+
+ <span class='nx-comment'># Define an alias for the Tcl command ::incr
+</span> <span class='nx-comment'># and assure, it always returns an integer
+</span> <span class='nx-comment'># value
+</span> <span class='nx-keyword'>:alias</span> <span class='nx-keyword'>incr</span> -returns integer ::incr
+
+ <span class='nx-comment'># Define a forwarder that has to return an
+</span> <span class='nx-comment'># integer value
+</span> <span class='nx-keyword'>:forward</span> ++ -returns integer ::expr 1 +
+
+ <span class='nx-comment'># Define a method that has to return a
+</span> <span class='nx-comment'># non-empty list of objects
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> instances {} \
+ -returns <span class='nx-keyword'>object</span>,1..n {
+ <span class='nx-keyword'>return</span> [<span class='nx-keyword'>:info</span> instances]
+ }
+}</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_interceptors">2.5. Interceptors</h3>
+<div class="paragraph"><p>XOTcl and NX allow the definition of the same set of interceptors,
+namely class- and object-level mixins and class- and object-level
+filters. The primary difference in NX is the naming, since NX abandons
+the prefix "inst" from the names of instance specific method, but uses
+the modifier <code>object</code>" for object specific methods.</p></div>
+<div class="paragraph"><p>Therefore, in NX, if a <code>mixin</code> is registered on a class-level, it is
+applicable for the instances (a per-class mixin), and if and <code>object
+mixin</code> is registered, it is a per-object mixin. In both cases, the
+term <code>mixin</code> is used, in the second case with the modifier
+<code>object</code>. As in all other cases, one can register the same way a
+per-object mixin on a plain object or on a class object.</p></div>
+<div class="sect3">
+<h4 id="_register_mixin_classes_and_mixin_guards">2.5.1. Register Mixin Classes and Mixin Guards</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> instmixin ...
+<span class='nx-placeholder'>/cls/</span> instmixinguard /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
+
+<span class='nx-comment'># Query per-class mixin
+</span><span class='nx-placeholder'>/cls/</span> instmixin</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Register/clear per-class mixin and guard for
+</span><span class='nx-comment'># a class
+</span>
+<span class='nx-placeholder'>/cls/</span> mixins add|<span class='nx-keyword'>set</span>|clear ...
+<span class='nx-placeholder'>/cls/</span> mixins <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>configure</span> -mixin ...
+
+<span class='nx-comment'># Query per-class mixins
+</span><span class='nx-placeholder'>/cls/</span> mixins get
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>cget</span> -mixins
+
+<span class='nx-comment'># Query per-class mixins (without guards)
+</span><span class='nx-placeholder'>/cls/</span> mixins classes</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>mixin</span> ...
+<span class='nx-placeholder'>/obj/</span> mixinguard /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
+
+<span class='nx-comment'># Query per-object mixins
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>mixin</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Register/clear per-object mixin and guard for
+</span><span class='nx-comment'># an object
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins add|<span class='nx-keyword'>set</span>|clear ...
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>mixin</span>/ <span class='nx-placeholder'>?condition?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>configure</span> -object-mixins ...
+
+<span class='nx-comment'># Query per-object mixin
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> mixins get
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>cget</span> -object-mixin
+
+<span class='nx-comment'># Query per-object mixins (without guards)
+</span><span class='nx-placeholder'>/cls/</span> mixins classes</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_register_filters_and_filter_guards">2.5.2. Register Filters and Filter Guards</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Register per-class filter and guard for
+</span><span class='nx-comment'># a class
+</span><span class='nx-placeholder'>/cls/</span> instfilter ...
+<span class='nx-placeholder'>/cls/</span> instfilterguard /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
+
+<span class='nx-comment'># Query per-class filter
+</span><span class='nx-placeholder'>/cls/</span> instfilter</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Register/clear per-class filter and guard for
+</span><span class='nx-comment'># a class
+</span>
+<span class='nx-placeholder'>/cls/</span> filters add|<span class='nx-keyword'>set</span>|clear ...
+<span class='nx-placeholder'>/cls/</span> filters <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>configure</span> -filters ...
+
+<span class='nx-comment'># Query per-class filters
+</span><span class='nx-placeholder'>/cls/</span> filters get
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>cget</span> -filters
+
+<span class='nx-comment'># Query per-class filters (without guards)
+</span><span class='nx-placeholder'>/cls/</span> filters <span class='nx-keyword'>methods</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>filter</span> ...
+<span class='nx-placeholder'>/obj/</span> filterguard /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Register(clear per-object filter and guard for
+</span><span class='nx-comment'># an object
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> filters add|<span class='nx-keyword'>set</span>|clear ...
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span> filters <span class='nx-keyword'>guard</span> /<span class='nx-keyword'>filter</span>/ <span class='nx-placeholder'>?condition?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>configure</span> -object-filters ...
+
+<span class='nx-comment'># Query per-object filters
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span> filters get
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>cget</span> -object-filters
+
+<span class='nx-comment'># Query per-object filters (without guards)
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span> filters <span class='nx-keyword'>methods</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_introspection">2.6. Introspection</h3>
+<div class="paragraph"><p>In general, introspection in NX became more orthogonal and less
+dependent on the type of the method. In XOTcl it was e.g. necessary
+that a developer had to know, whether a method is e.g. scripted or not
+and has to use accordingly different sub-methods of <code>info</code>.</p></div>
+<div class="paragraph"><p>In NX, one can use e.g. always <code>info method</code> with a subcommand and the
+framework tries to hide the differences as far as possible. So, one
+can for example obtain with <code>info method parameter</code> the parameters of
+scripted and C-implemented methods the same way, one can get the
+definition of all methods via <code>info method definition</code> and one can get
+an manual-like interface description via <code>info method
+syntax</code>. In addition, NX provides means to query the type of
+a method, and NX allows one to filter by the type of the method.</p></div>
+<div class="sect3">
+<h4 id="_list_sub_and_superclass_relations">2.6.1. List sub- and superclass relations</h4>
+<div class="paragraph"><p>While XOTcl used singular words for introspecting sub- and superclass
+relations, NX uses plural word to indicate that potentially a list of
+values is returned.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>superclass</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> superclasses <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> subclass <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> subclasses -type setter <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_methods_defined_by_classes">2.6.2. List methods defined by classes</h4>
+<div class="paragraph"><p>While XOTcl uses different names for obtaining different kinds of
+methods defined by a class, NX uses <code>info methods</code> in an orthogonal
+manner. NX allows as well to use the call protection to filter the
+returned methods.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instcommands <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instparametercmd <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type setter <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instprocs <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type scripted <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>alias</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type forwarder <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> -callprotection <span class='nx-keyword'>public</span>|<span class='nx-keyword'>protected</span> ...</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_methods_defined_by_objects">2.6.3. List methods defined by objects</h4>
+<div class="paragraph"><p>While XOTcl uses different names for obtaining different kinds of
+methods defined by an object, NX uses <code>info methods</code> in an orthogonal
+manner. NX allows as well to use the call protection to filter the
+returned methods.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> commands <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> parametercmd <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type setter <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> procs <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type scripted <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>alias</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type forwarder <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -type <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> -callprotection <span class='nx-keyword'>public</span>|<span class='nx-keyword'>protected</span> ...</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_check_existence_of_a_method">2.6.4. Check existence of a method</h4>
+<div class="paragraph"><p>NX provides multiple ways of checking, whether a method exists; one
+can use <code>info method exists</code> to check, if a given method exists
+(return boolean), or one can use <code>info methods ?pattern?</code>, where
+<code>pattern</code> might be a single method name without wild-card
+characters. The method <code>info methods ?pattern?</code> returns a list of
+matching names, which might be empty. These different methods appear
+appropriate depending on the context.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>/obj|cls/ <span class='nx-keyword'>info</span> \
+ [inst](commands|procs|parametercmd) \
+ <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> exists <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> exists <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_callable_methods">2.6.5. List callable methods</h4>
+<div class="paragraph"><p>In order to obtain for an object the set of artefacts defined in the
+ class hierarchy, NX uses <code>info lookup</code>. One can either lookup methods
+ (via <code>info lookup methods</code>) or slots (via <code>info lookup slots</code>). The
+ plural term refers to a potential set of return values.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>methods</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>methods</span> ... <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-comment'># Returns list of method names</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List only application specific methods
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>methods</span> -source application ... <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-comment'># Returns list of method names</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Options for 'info methods'
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># -incontext
+</span><span class='nx-comment'># -nomixins</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Options for 'info lookup methods'
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># -source ...
+</span><span class='nx-comment'># -callprotection ...
+</span><span class='nx-comment'># -incontext
+</span><span class='nx-comment'># -type ...
+</span><span class='nx-comment'># -nomixins</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List slot objects defined for obj
+</span><span class='nx-comment'># -source might be all|application|baseclasses
+</span><span class='nx-comment'># -type is the class of the slot object
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> slots <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?-source ...?</span> <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># Returns list of slot objects</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List registered filters
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> filters -order <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># List registered mixins
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> mixins -heritage <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List registered filters
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> filters <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># List registered mixins
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> mixins <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_object_class_where_a_specified_method_is_defined">2.6.6. List object/class where a specified method is defined</h4>
+<div class="paragraph"><p><code>info lookup</code> can be used as well to determine, where exactly an
+ artefact is located. One can obtain this way a method handle, where
+a method or filter is defined.</p></div>
+<div class="paragraph"><p>The concept of a <em>method-handle</em> is new in NX. The method-handle
+can be used to obtain more information about the method, such as
+e.g. the definition of the method.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> procsearch <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>method</span> <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-comment'># Returns method-handle</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> filtersearch <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> <span class='nx-keyword'>filter</span> <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-comment'># Returns method-handle</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_definition_of_scripted_methods">2.6.7. List definition of scripted methods</h4>
+<div class="paragraph"><p>XOTcl contains a long list of <code>info</code> subcommands for different kinds of
+methods and for obtaining more detailed information about these
+methods.</p></div>
+<div class="paragraph"><p>In NX, this list of <code>info</code> subcommands is much shorter and more
+orthogonal. For example <code>info method definition</code> can be used to obtain
+with a single command the full definition of a <em>scripted method</em>, and
+furthermore, it works as well the same way to obtain e.g. the
+definition of a <em>forwarder</em> or an <em>alias</em>.</p></div>
+<div class="paragraph"><p>While XOTcl uses different names for info options for objects and
+classes (using the prefix "inst" for instance specific method), NX
+uses for object specific method the modifier <code>object</code>. For definition
+of class object specific methods, use the modifier <code>object</code> as usual.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instbody <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> body <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> body <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> body <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instargs <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instnonposargs <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> args <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> parameter <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> parameter <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instdefault <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> default <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># not needed, part of
+</span><span class='nx-comment'># "info ?object? method parameter"</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instpre <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> pre <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> precondition <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> precondition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instpost <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> post <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> postcondition <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> postcondition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+<div class="paragraph"><p>Another powerful introspection option in NX is <code>info ?object? method
+syntax</code> which obtains a representation of the parameters of a
+method in the style of Tcl man pages (regardless of the kind of
+method).</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> syntax <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> syntax <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="info_configure_parameter">2.6.8. List Configure Parameters</h4>
+<div class="paragraph"><p>The way, how newly created objects can be configured is determined in NX
+via properties. The configuration happens during creation via the
+methods <code>create</code> or <code>new</code> or during runtime via <code>configure</code>. These
+methods have therefore virtual argument lists, depending on the object
+or class on which they are applied.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Return the parameters applicable to
+</span><span class='nx-comment'># the create method of a certain class.
+</span><span class='nx-comment'># class can be configured. A pattern can
+</span><span class='nx-comment'># be used to filter the results.
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> parameters <span class='nx-keyword'>create</span> ?<span class='nx-placeholder'>/pattern/</span>?
+
+<span class='nx-comment'># Return in the result in documentation syntax
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>create</span> ?<span class='nx-placeholder'>/pattern/</span>?
+
+<span class='nx-comment'># "info lookup parameters configure" returns
+</span><span class='nx-comment'># parameters available for configuring the
+</span><span class='nx-comment'># current object (might contain object
+</span><span class='nx-comment'># specific information)
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> parameters <span class='nx-keyword'>configure</span> <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># "info lookup configure syntax" returns syntax of
+</span><span class='nx-comment'># a call to configure in the Tcl parameter syntax
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
+
+<span class='nx-comment'># Obtain information from a parameter
+</span><span class='nx-comment'># (as e.g. returned from "info lookup
+</span><span class='nx-comment'># parameters configure").
+</span>
+nsf::parameter::info name <span class='nx-placeholder'>/parameter/</span>
+nsf::parameter::info syntax <span class='nx-placeholder'>/parameter/</span>
+nsf::parameter::info type <span class='nx-placeholder'>/parameter/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_variable_declarations_property_and_variable">2.6.9. List Variable Declarations (property and variable)</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># obtain parameter definitions defined
+</span><span class='nx-comment'># for a class
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> parameter</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># "info variables" returns handles of
+</span><span class='nx-comment'># properties and variables defined by this
+</span><span class='nx-comment'># class or object
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> variables <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> variables <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># "info lookup variables" returns handles
+</span><span class='nx-comment'># of variables and properties applicable
+</span><span class='nx-comment'># for the current object (might contain
+</span><span class='nx-comment'># object specific information)
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> variables <span class='nx-placeholder'>/pattern/</span>
+
+<span class='nx-comment'># "info variable" lists details about a
+</span><span class='nx-comment'># single property or variable.
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> definition <span class='nx-placeholder'>/handle/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> name <span class='nx-placeholder'>/handle/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>variable</span> parameter <span class='nx-placeholder'>/handle/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_slots">2.6.10. List Slots</h4>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Return list of slots objects defined on the
+</span><span class='nx-comment'># object or class
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># -source might be all|application|baseclasses
+</span><span class='nx-comment'># -type is the class of the slot object
+</span><span class='nx-comment'># -closure includes slots of superclasses
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> slots \
+ <span class='nx-placeholder'>?-type value?</span> <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?-source value?</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> slots <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?pattern?</span>
+
+<span class='nx-comment'># List reachable slot objects defined for obj
+</span><span class='nx-comment'># -source might be all|application|baseclasses
+</span><span class='nx-comment'># -type is the class of the slot object
+</span><span class='nx-comment'># Returns list of slot objects.
+</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> slots \
+ <span class='nx-placeholder'>?-type ...?</span> <span class='nx-placeholder'>?-source ... ?</span>pattern?
+
+<span class='nx-comment'># Obtain definition, name or parameter from
+</span><span class='nx-comment'># slot object
+</span>
+<span class='nx-placeholder'>/slotobj/</span> definition
+<span class='nx-placeholder'>/slotobj/</span> name
+<span class='nx-placeholder'>/slotobj/</span> parameter</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_filter_or_mixins">2.6.11. List Filter or Mixins</h4>
+<div class="paragraph"><p>In NX all introspection options for filters are provided via
+<code>info filters</code> and all introspection options for mixins are
+provided via <code>info mixins</code>.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>filter</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> filterguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> filters \
+ <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instfilter \
+ <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instfilterguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> filters \
+ <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>mixin</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order ?</span>pattern?
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> mixinguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> mixins \
+ <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixin \
+ <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-order?</span> <span class='nx-placeholder'>?pattern?</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixinguard <span class='nx-placeholder'>/name/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixins \
+ <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?-guards?</span> <span class='nx-placeholder'>?-heritage?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_definition_of_methods_defined_by_aliases_setters_or_forwarders">2.6.12. List definition of methods defined by aliases, setters or forwarders</h4>
+<div class="paragraph"><p>As mentioned earlier, <code>info method definition</code> can be used on every
+kind of method. The same call can be used to obtain the definition of
+a scripted method, a method-alias, a forwarder or a setter method.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> definition <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_method_handles">2.6.13. List Method-Handles</h4>
+<div class="paragraph"><p>NX supports <em>method-handles</em> to provide means to obtain further
+information about a method or to change maybe some properties of a
+method. When a method is created, the method creating method returns
+the method handle to the created method.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># List the method handle of the specified method,
+</span><span class='nx-comment'># can be used e.g. for aliases. "handle" is the short
+</span><span class='nx-comment'># form of "definitionhandle".
+</span><span class='nx-comment'>#
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> handle <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> handle <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-comment'>#
+</span><span class='nx-comment'># For ensemble methods (method name contains
+</span><span class='nx-comment'># spaces) one can query as well the registration
+</span><span class='nx-comment'># handle, which is the handle to the root of the
+</span><span class='nx-comment'># ensemble; the definition handle points to the
+</span><span class='nx-comment'># leaf of the ensemble.
+</span><span class='nx-comment'>#
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> registrationhandle <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> registrationhandle <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-comment'>#
+</span><span class='nx-comment'># For aliases, one can query the original
+</span><span class='nx-comment'># definition via "info method origin"
+</span><span class='nx-comment'>#
+</span><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> origin <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> origin <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_type_of_a_method">2.6.14. List type of a method</h4>
+<div class="paragraph"><p>The method <code>info ?object? method type</code> is new in NX to obtain the type of the
+specified method.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>method</span> type <span class='nx-placeholder'>/methodName/</span>
+<span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> type <span class='nx-placeholder'>/methodName/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_list_the_scope_of_mixin_classes">2.6.15. List the scope of mixin classes</h4>
+<div class="paragraph"><p>NX provides a richer set of introspection options to obtain
+information, where mixins classes are mixed into.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List objects, where /cls/ is a
+</span><span class='nx-comment'># per-object mixin
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope <span class='nx-keyword'>object</span> <span class='nx-placeholder'>?-closure?</span> \
+ <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instmixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List classes, where /cls/ is a per-class mixin
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope <span class='nx-keyword'>class</span> <span class='nx-placeholder'>?-closure?</span> \
+ <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># List objects and classes, where /cls/ is
+</span><span class='nx-comment'># either a per-object or a per-class mixin
+</span>
+<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof -scope all <span class='nx-placeholder'>?-closure?</span> \
+ <span class='nx-placeholder'>?pattern?</span></pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> mixinof <span class='nx-placeholder'>?-closure?</span> <span class='nx-placeholder'>?pattern?</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_check_properties_of_object_and_classes">2.6.16. Check properties of object and classes</h4>
+<div class="paragraph"><p>Similar as noted before, NX uses rather a hierarchical approach of
+naming using multiple layers of subcommands).</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> istype <span class='nx-placeholder'>/sometype/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check if object is a subtype of some class
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> has type <span class='nx-placeholder'>/sometype/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> ismixin <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check if object has the specified mixin registered
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> has <span class='nx-keyword'>mixin</span> <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> isclass ?<span class='nx-placeholder'>/cls/</span>?</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check if object is an NX class
+</span><span class='nx-placeholder'>/obj/</span> has type ::nx::Class
+
+<span class='nx-comment'># Check if object is a class in one of the
+</span><span class='nx-comment'># NSF object systems
+</span>::nsf::is <span class='nx-keyword'>class</span> <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> ismetaclass <span class='nx-placeholder'>/cls/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check if class is an NX metaclass
+</span><span class='nx-keyword'>expr</span> {[<span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> heritage ::nx::Class] ne <span class='nx-string'>""</span>}
+
+<span class='nx-comment'># Check if object is a metaclass in one of the
+</span><span class='nx-comment'># NSF object systems
+</span>::nsf::is <span class='nx-keyword'>metaclass</span> <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check if object is a baseclass of an object system
+</span>::nsf::is baseclass <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Return name of object (without namespace prefix)
+</span><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> name</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span>::exists <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Check for existence of object (nsf primitive)
+</span>::nsf::object::exists <span class='nx-placeholder'>/obj/</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_call_stack_introspection">2.6.17. Call-stack Introspection</h4>
+<div class="paragraph"><p>Call-stack introspection is very similar in NX and XOTcl. NX uses for
+subcommand the term <code>current</code> instead of <code>self</code>, since <code>self</code> has a
+strong connotation to the current object. The term <code>proc</code> is renamed
+by <code>method</code>.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span></pre></div></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> <span class='nx-keyword'>object</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> <span class='nx-keyword'>class</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> <span class='nx-keyword'>class</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> args</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> args</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> <span class='nx-keyword'>proc</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> <span class='nx-keyword'>method</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> callingclass</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> calledclass</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> callingobject</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> callingobject</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> callingproc</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> callingmethod</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> calledclass</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> calledclass</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> calledproc</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> calledmethod</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> isnextcall</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> isnextcall</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> <span class='nx-keyword'>next</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Returns method-handle of the
+</span><span class='nx-comment'># method to be called via "next"
+</span><span class='nx-keyword'>current</span> <span class='nx-keyword'>next</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> filterreg</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Returns method-handle of the
+</span><span class='nx-comment'># filter method
+</span><span class='nx-keyword'>current</span> filterreg</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> callinglevel</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> callinglevel</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>self</span> activelevel</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>current</span> activelevel</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_other_predefined_methods">2.7. Other Predefined Methods</h3>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> requireNamespace</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>require</span> <span class='nx-keyword'>namespace</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># n.a.</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>require</span> <span class='nx-keyword'>method</span></pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_dispatch_aliases_etc">2.8. Dispatch, Aliases, etc.</h3>
+<div class="paragraph"><p>todo: to be done or omitted</p></div>
+</div>
+<div class="sect2">
+<h3 id="_assertions">2.9. Assertions</h3>
+<div class="paragraph"><p>In contrary to XOTcl, NX provides no pre-registered methods for
+assertion handling. All assertion handling can e performed via the
+Next Scripting primitive <code>nsf::method::assertion</code>.</p></div>
+<div class="tableblock">
+<table rules="all"
+width="100%"
+frame="void"
+cellspacing="0" cellpadding="4">
+<col width="50%" />
+<col width="50%" />
+<thead>
+<tr>
+<th align="left" valign="middle">XOTcl </th>
+<th align="left" valign="middle">Next Scripting Language</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> check <span class='nx-placeholder'>/checkoptions/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/obj/</span> check <span class='nx-placeholder'>/checkoptions/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> check</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/obj/</span> check</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> invar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
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+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span>-invar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
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+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>info</span> invar</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
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+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/obj/</span> <span class='nx-keyword'>object</span>-invar</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
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+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> instinvar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>class</span>-invar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> instinvar</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>class</span>-invar</pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> invar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
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+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span>-invar <span class='nx-placeholder'>/conditions/</span></pre></div></div></div></td>
+</tr>
+<tr>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>info</span> invar</pre></div></div></div></td>
+<td align="left" valign="middle"><div><div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nsf::method::assertion <span class='nx-placeholder'>/cls/</span> <span class='nx-keyword'>object</span>-invar</pre></div></div></div></td>
+</tr>
+</tbody>
+</table>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_method_protection">2.10. Method Protection</h3>
+<div class="paragraph"><p>As described <a href="#method-protect-example">above</a>, NX supports method
+protection via the method modifiers <code>protected</code> and <code>public</code>. A
+protected method can be only called from an object of that class,
+while public methods can be called from every object. The method
+protection can be used to every kind of method, such as e.g. scripted
+methods, aliases, forwarders, or accessors. For invocations,
+the most specific definition (might be a mixin) is used for
+determining the protection.</p></div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_incompatibilities_between_xotcl_1_and_xotcl_2">3. Incompatibilities between XOTcl 1 and XOTcl 2</h2>
+<div class="sectionbody">
+<div class="sect2">
+<h3 id="_resolvers_2">3.1. Resolvers</h3>
+<div class="paragraph"><p>The resolvers (variable resolvers, function resolvers) of the Next
+Scripting Framework are used as well within XOTcl 2. When variable
+names or method names starting with a single colon are used in XOTcl 1
+scripts, conflicts will arise with the resolver. These names must be
+replaced.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_parameters_2">3.2. Parameters</h3>
+<div class="paragraph"><p>The following changes for parameters could be regarded as bug-fixes.</p></div>
+<div class="sect3">
+<h4 id="_parameter_usage_without_a_value">3.2.1. Parameter usage without a value</h4>
+<div class="paragraph"><p>In XOTcl 1, it was possible to call a parameter method during object
+creation via the dash-interface without a value (in the example below <code>-x</code>).</p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># XOTcl example
+</span>
+<span class='nx-keyword'>Class</span> Foo -parameter {x y}
+Foo f1 -x -y 1</pre></div></div>
+<div class="paragraph"><p>Such cases are most likely mistakes. All parameter configurations in XOTcl 2 require an argument.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_ignored_parameter_definitions">3.2.2. Ignored Parameter definitions</h4>
+<div class="paragraph"><p>In XOTcl 1, a more specific parameter definition without a default was ignored
+when a more general parameter definition with a default was
+present. In the example below, the object <code>b1</code> contained in XOTcl 1
+incorrectly the parameter <code>x</code> (set via default from <code>Foo</code>), while in
+XOTcl 2, the variable won’t be set.</p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># XOTcl example
+</span>
+<span class='nx-keyword'>Class</span> Foo -parameter {{x 1}}
+<span class='nx-keyword'>Class</span> Bar -superclass Foo -parameter x
+Bar b1</pre></div></div>
+</div>
+<div class="sect3">
+<h4 id="_changing_classes_and_superclasses">3.2.3. Changing classes and superclasses</h4>
+<div class="paragraph"><p>NX does not define the methods <code>class</code> and <code>superclass</code> (like XOTcl), but allows one to
+alter all object/class relations (including
+class/superclass/object-mixin/…)
+<code>nsf::relation::set</code>. The class and superclass can be certainly queried
+in all variants with <code>info class</code> or <code>info superclasses</code>.</p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># NX example
+</span>
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo
+Foo <span class='nx-keyword'>create</span> f1
+
+<span class='nx-comment'># now alter the class of object f1
+</span>nsf::relation::set f1 <span class='nx-keyword'>class</span> ::nx::Object</pre></div></div>
+</div>
+<div class="sect3">
+<h4 id="_overwriting_procs_methods_with_objects_and_vice_versa">3.2.4. Overwriting procs/methods with objects and vice versa</h4>
+<div class="paragraph"><p>NSF is now more conservative on object/method creation. In contrary to
+XOTcl 1 NSF does not allow one to redefined a pre-existing command
+(e.g. "set") with an object and vice versa. Like in XOTcl 1,
+preexisting objects and classes con be redefined (necessary for
+reloading objects/classes in a running interpreter).</p></div>
+</div>
+<div class="sect3">
+<h4 id="_info_heritage">3.2.5. Info heritage</h4>
+<div class="paragraph"><p><code>info heritage</code> returns in XOTcl 1 the transitive superclass
+hierarchy, which is equivalent with <code>info superclasses -closure</code> and
+therefore not necessary. In XOTcl 2 (and NX), <code>info heritage</code> includes
+as well the transitive per-class mixins.</p></div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_slots">3.3. Slots</h3>
+<div class="paragraph"><p>All slot objects (also XOTcl slot objects) are now next-scripting
+objects of baseclass <code>::nx::Slot</code>. The name of the experimental
+default-setter <code>initcmd</code> was changed to <code>defaultcmd</code>. Code directly
+working on the slots objects has to be adapted.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_obsolete_commands">3.4. Obsolete Commands</h3>
+<div class="paragraph"><p>Parameter-classes were rarely used and have been replaced by the more
+general object parametrization. Therefore, <code>cl info parameterclass</code> has
+been removed.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_stronger_checking">3.5. Stronger Checking</h3>
+<div class="paragraph"><p>The Next Scripting Framework performs stronger checking than XOTcl 1
+For example, the requiredness of slots in XOTcl 1 was just a
+comment, while XOTcl 2 enforces it.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_exit_handlers">3.6. Exit Handlers</h3>
+<div class="paragraph"><p>The exit handler interface changed from a method of <code>::xotcl::Object</code>
+into the Tcl command <code>::nsf::exithandler</code>:</p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># NX example
+</span>::nsf::exithandler <span class='nx-keyword'>set</span>|get|<span class='nx-keyword'>unset</span> <span class='nx-placeholder'>?arg?</span></pre></div></div>
+</div>
+</div>
+</div>
+</div>
+<div id="footnotes"><hr /></div>
+<div id="footer">
+<div id="footer-text">
+Version 2.2.0<br />
+Last updated 2019-04-19 00:25:17 CEST
+</div>
+</div>
+</body>
+</html>
Index: doc/next-tutorial/next-tutorial.html
===================================================================
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-<h1>Tutorial for the Next Scripting Language</h1>
-<span id="author">Gustaf Neumann <neumann@wu-wien.ac.at>, Stefan Sobernig <stefan.sobernig@wu.ac.at></span><br />
-<span id="revnumber">version 2.2.0,</span>
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-<br /><span id="revremark">Written for the Initial Release of the Next Scripting Framework.</span>
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+<body class="article">
+<div id="header">
+<h1>Tutorial for the Next Scripting Language</h1>
+<span id="author">Gustaf Neumann <neumann@wu-wien.ac.at>, Stefan Sobernig <stefan.sobernig@wu.ac.at></span><br />
+<span id="revnumber">version 2.2.0,</span>
+<span id="revdate">September 2018</span>
+<br /><span id="revremark">Written for the Initial Release of the Next Scripting Framework.</span>
<div id="toc">
<div id="toctitle">Table of Contents</div>
<noscript><p><b>JavaScript must be enabled in your browser to display the table of contents.</b></p></noscript>
-</div>
-</div>
-<div id="content">
-<div id="preamble">
-<div class="sectionbody">
-<div class="sidebarblock">
-<div class="content">
-<div class="title">Abstract</div>
-<div class="paragraph"><p>This document provides a tutorial for the Next Scripting
-Language NX.</p></div>
-</div></div>
-<div class="paragraph"><p>The Next Scripting Language (NX) is a highly flexible object oriented
-scripting language based on Tcl <a href="#Ousterhout 1990">[Ousterhout 1990]</a>. NX is a successor
-of XOTcl 1 <a href="#Neumann and Zdun 2000a">[Neumann and Zdun 2000a]</a> and was developed based on 10
-years of experience with XOTcl in projects containing several hundred
-thousand lines of code. While XOTcl was the first language designed to
-provide <em>language support for design patterns</em>, the focus of the Next
-Scripting Framework and NX is on combining this with <em>Language
-Oriented Programming</em>. In many respects, NX was designed to ease the
-learning of the language for novices (by using a more mainstream
-terminology, higher orthogonality of the methods, less predefined
-methods), to improve maintainability (remove sources of common errors)
-and to encourage developers to write better structured programs (to
-provide interfaces) especially for large projects, where many
-developers are involved.</p></div>
-<div class="paragraph"><p>The Next Scripting Language is based on the Next Scripting Framework
-(NSF) which was developed based on the notion of language oriented
-programming. The Next Scripting Frameworks provides C-level support
-for defining and hosting multiple object systems in a single Tcl
-interpreter. The name of the Next Scripting Framework is derived from
-the universal method combinator "next", which was introduced in XOTcl.
-The combinator "next" serves as a single instrument for method
-combination with filters, per-object and transitive per-class mixin
-classes, object methods and multiple inheritance.</p></div>
-<div class="paragraph"><p>The definition of NX is fully scripted (e.g. defined in
-<code>nx.tcl</code>). The Next Scripting Framework is shipped with three language
-definitions, containing NX and XOTcl 2. Most of the existing XOTcl 1
-programs can be used without modification in the Next Scripting
-Framework by using XOTcl 2. The Next Scripting Framework requires Tcl
-8.5 or newer.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_nx_and_its_roots">1. NX and its Roots</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>Object oriented extensions of Tcl have quite a
-long history. Two of the most prominent early Tcl based OO languages
-were <em>incr Tcl</em> (abbreviated as itcl) and Object Tcl (<em>OTcl</em>
-<a href="#Wetherall and Lindblad 1995">[Wetherall and Lindblad 1995]</a>). While itcl provides a traditional
-C++/Java-like object system, OTcl was following the CLOS approach and
-supports a dynamic object system, allowing incremental class and
-object extensions and re-classing of objects.</p></div>
-<div class="paragraph"><p>Extended Object Tcl (abbreviated as XOTcl <a href="#Neumann and Zdun 2000a">[Neumann and Zdun 2000a]</a>)
-is a successor of OTcl and was the first language providing language
-support for design patterns. XOTcl extends OTcl by providing namespace
-support, adding assertions, dynamic object aggregations, slots and by
-introducing per-object and per-class filters and per-object and
-per-class mixins.</p></div>
-<div class="paragraph"><p>XOTcl was so far released in more than 30 versions. It is described in
-its detail in more than 20 papers and serves as a basis for other
-object systems like TclOO [Donal ???]. The scripting language <em>NX</em> and
-the <em>Next Scripting Framework</em> <a href="#Neumann and Sobernig 2009">[Neumann and Sobernig 2009]</a> extend
-the basic ideas of XOTcl by providing support for <em>language-oriented
-programming</em>. The the Next Scripting Framework supports multiple
-object systems concurrently. Effectively, every object system has
-different base classes for creating objects and classes. Therefore,
-these object systems can have different interfaces and can
-follow different naming conventions for built-in methods. Currently,
-the Next Scripting Framework is packaged with three object systems:
-NX, XOTcl 2.0, and TclCool (the language introduced by TIP#279).</p></div>
-<div class="imageblock" style="text-align:center;">
-<div class="content">
-<img src="languages.png" alt="Languages" width="500" />
-</div>
-<div class="title">Figure 1. Language History of the Next Scripting Language</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>The primary purpose of this document is to introduce NX to beginners.
-We expect some prior knowledge of programming languages, and some
-knowledge about Tcl. In the following sections we introduce NX by
-examples. In later sections we introduce the more advanced concepts of
-the language. Conceptually, most of the addressed concepts are very
-similar to XOTcl. Concerning the differences between NX and XOTcl,
-please refer to the <em>Migration Guide for the Next Scripting Language</em>.</p></div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_introductory_overview_example_stack">2. Introductory Overview Example: Stack</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>A classical programming example is the implementation of a stack, which
-is most likely familiar to many readers from many introductory
-programming courses. A stack is a last-in first-out data structure
-which is manipulated via operations like <code>push</code> (add something to the
-stack) and <code>pop</code> remove an entry from the stack. These operations are
-called <em>methods</em> in the context of object oriented programming
-systems. Primary goals of object orientation are encapsulation and
-abstraction. Therefore, we define a common unit (a class) that defines
-and encapsulates the behavior of a stack and provides methods to a user
-of the data structure that abstract from the actual implementation.</p></div>
-<div class="sect2">
-<h3 id="_define_a_class_stack">2.1. Define a Class "Stack"</h3>
-<div class="paragraph"><p>In our first example, we define a class named <code>Stack</code> with the methods
-<code>push</code> and <code>pop</code>. When an instance of the stack is created (e.g. a
-concrete stack <code>s1</code>) the stack will contain an instance variable named
-<code>things</code>, initialized with the an empty list.</p></div>
-<div class="paragraph" id="xmp-class-stack"><div class="title">Listing 2: Class Stack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Stack of Things
-</span> <span class='nx-comment'>#
-</span>
- <span class='nx-keyword'>:variable</span> things {}
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
- }
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
- <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p>Typically, classes are defined in NX via <code>nx::Class create</code>, followed
-by the name of the new class (here: <code>Stack</code>). The definition of the
-stack placed between curly braces and contains here just the method
-definitions. Methods of the class are defined via <code>:method</code> followed
-by the name of the method, an argument list and the body of the
-method, consisting of Tcl and NX statements.</p></div>
-<div class="paragraph"><p>When an instance of <code>Stack</code> is created, it will contain an instance
-variable named <code>things</code>. If several <code>Stack</code> instances are created,
-each of the instances will have their own (same-named but different)
-instance variable. The instance variable <code>things</code> is used in our
-example as a list for the internal representation of the stack. We
-define in a next step the methods to access and modify this list
-structure. A user of the stack using the provided methods does not
-have to have any knowledge about the name or the structure of the
-internal representation (the instance variable <code>things</code>).</p></div>
-<div class="paragraph"><p>The method <code>push</code> receives an argument <code>thing</code> which should be placed
-on the stack. Note that we do not have to specify the type of the
-element on the stack, so we can push strings as well as numbers or
-other kind of things. When an element is pushed, we add this element
-as the first element to the list <code>things</code>. We insert the element using
-the Tcl command <code>linsert</code> which receives the list as first element,
-the position where the element should be added as second and the new
-element as third argument. To access the value of the instance
-variable we use Tcl’s dollar operator followed by the name. The
-names of instance variables are preceded with a colon <code>:</code>. Since the
-name contains a non-plain character, Tcl requires us to put braces
-around the name. The command <code>linsert</code> and its arguments are placed
-between square brackets. This means that the function <code>linsert</code> is called and
-a new list is returned, where the new element is inserted at the first
-position (index 0) in the list <code>things</code>. The result of the <code>linsert</code>
-function is assigned again to the instance variable <code>things</code>, which is
-updated this way. Finally the method <code>push</code> returns the pushed thing
-using the <code>return</code> statement.</p></div>
-<div class="paragraph"><p>The method <code>pop</code> returns the most recently stacked element and removes
-it from the stack. Therefore, it takes the first element from the list
-(using the Tcl command <code>lindex</code>), assigns it to the method-scoped
-variable <code>top</code>, removes the element from the instance variable
-<code>things</code> (by using the Tcl command <code>lrange</code>) and returns the value
-popped element <code>top</code>.</p></div>
-<div class="paragraph"><p>This finishes our first implementation of the stack, more enhanced
-versions will follow. Note that the methods <code>push</code> and <code>pop</code> are
-defined as <code>public</code>; this means that these methods can be
-used from all other objects in the system. Therefore, these methods
-provide an interface to the stack implementation.</p></div>
-<div class="paragraph" id="xmp-using-stack"><div class="title">Listing 3: Using the Stack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#!/usr/bin/env tclsh
-</span><span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Stack of Things
-</span> <span class='nx-comment'>#
-</span> ....
-}
-
-Stack <span class='nx-keyword'>create</span> s1
-s1 push a
-s1 push b
-s1 push c
-<span class='nx-keyword'>puts</span> [s1 pop]
-<span class='nx-keyword'>puts</span> [s1 pop]
-s1 <span class='nx-keyword'>destroy</span></pre></div></div>
-<div class="paragraph"><p>Now we want to use the stack. The code snippet in <a href="#xmp-using-stack">Listing 3</a> shows how to use the class Stack in a script.
-Since NX is based on Tcl, the script will be called with the Tcl shell
-<code>tclsh</code>. In the Tcl shell we have to <code>require package nx</code> to use the
-Next Scripting Framework and NX. The next lines contain the definition
-of the stack as presented before. Of course, it is as well possible to
-make the definition of the stack an own package, such we could simple
-say <code>package require stack</code>, or to save the definition of a stack
-simply in a file and load it via <code>source</code>.</p></div>
-<div class="paragraph"><p>In line 12 we create an instance of the stack, namely the stack object
-<code>s1</code>. The object <code>s1</code> is an instance of <code>Stack</code> and has therefore
-access to its methods. The methods like <code>push</code> or <code>pop</code> can be invoked
-via a command starting with the object name followed by the
-method name. In lines 13-15 we push on the stack the values <code>a</code>, then
-<code>b</code>, and <code>c</code>. In line 16 we output the result of the <code>pop</code> method
-using the Tcl command <code>puts</code>. We will see on standard output the
-value+c+ (the last stacked item). The output of the line 17 is the
-value <code>b</code> (the previously stacked item). Finally, in line 18 we
-destroy the object. This is not necessary here, but shows the life
-cycle of an object. In some respects, <code>destroy</code> is the counterpart of
-<code>create</code> from line 12.</p></div>
-<div class="imageblock" id="fig-class-object" style="text-align:center;">
-<div class="content">
-<img src="object-class-appclass.png" alt="object-class-appclass.png" />
-</div>
-<div class="title">Figure 4. Class and Object Diagram</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p><a href="#fig-class-object">Figure 4</a> shows the actual class and
-object structure of the first <code>Stack</code> example. Note that the common
-root class is <code>nx::Object</code> that contains methods for all objects.
-Since classes are as well objects in NX, <code>nx::Class</code> is a
-specialization of <code>nx::Object</code>. <code>nx::Class</code> provides methods for
-creating objects, such as the method <code>create</code> which is used to create
-objects (and classes as well).</p></div>
-</div>
-<div class="sect2">
-<h3 id="_define_an_object_named_stack">2.2. Define an Object Named "stack"</h3>
-<div class="paragraph"><p>The definition of the stack in <a href="#xmp-class-stack">Listing 2</a>
-follows the traditional object oriented approach, found in
-practically every object oriented programming language: Define a class
-with some methods, create instances from this class, and use the
-methods defined in the class in the instances of the class.</p></div>
-<div class="paragraph"><p>In our next example, we introduce <em>generic objects</em> and <em>object
-specific methods</em>. With NX, we can define generic objects, which are
-instances of the most generic class <code>nx::Object</code> (sometimes called
-<em>common root class</em>). <code>nx::Object</code> is predefined and contains a
-minimal set of methods applicable to all NX objects. In this example,
-we define a generic object named <code>stack</code> and provide methods for this
-object. The methods defined above were methods provided by a class for
-objects. Now we define object specific methods, which are methods
-applicable only to the object for which they are defined.</p></div>
-<div class="paragraph" id="xmp-object-stack"><div class="title">Listing 5: Object stack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> stack {
-
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>variable</span> things {}
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> push {thing} {
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
- }
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> pop {} {
- <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p>The example in <a href="#xmp-object-stack">Listing 5</a> defines the
-object <code>stack</code> in a very similar way as the class <code>Stack</code>. But the
-following points are different.</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-First, we use <code>nx::Object</code> instead of <code>nx::Class</code> to denote
- that we want to create a generic object, not a class.
-</p>
-</li>
-<li>
-<p>
-We use <code>:object variable</code> to define the variable <code>things</code> just for
- this single instance (the object <code>stack</code>).
-</p>
-</li>
-<li>
-<p>
-The definition for the methods <code>push</code> and <code>pop</code> are the same as
- before, but here we defined these with <code>object method</code>. Therefore,
- these two methods <code>push</code> and <code>pop</code> are object-specific.
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>In order to use
-the stack, we can use directly the object <code>stack</code> in the same way as
-we have used the object <code>s1</code> in <a href="#xmp-using-stack">Listing 3</a>
-the class diagram for this the object <code>stack</code>.</p></div>
-<div class="imageblock" id="img-object-stack" style="text-align:center;">
-<div class="content">
-<img src="object-stack.png" alt="object-stack.png" />
-</div>
-<div class="title">Figure 6. Object stack</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>A reader might wonder when to use a class <code>Stack</code> or rather an object
-<code>stack</code>. A big difference is certainly that one can define easily
-multiple instances of a class, while the object is actually a
-single, tailored entity. The concept of the object <code>stack</code> is similar to a module,
-providing a certain functionality via a common interface, without
-providing the functionality to create multiple instances. The reuse of
-methods provided by the class to objects is as well a difference. If
-the methods of the class are updated, all instances of the class will
-immediately get the modified behavior. However, this does not mean that
-the reuse for the methods of <code>stack</code> is not possible. NX allows for
-example to copy objects (similar to prototype based languages) or to
-reuse methods via e.g. aliases (more about this later).</p></div>
-<div class="paragraph"><p>Note that we use capitalized names for classes and lowercase names for
-instances. This is not required and a pure convention making it easier
-to understand scripts without much analysis.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_implementing_features_using_mixin_classes">2.3. Implementing Features using Mixin Classes</h3>
-<div class="paragraph"><p>So far, the definition of the stack methods was pretty minimal.
-Suppose, we want to define "safe stacks" that protect e.g. against
-stack under-runs (a stack under-run happens, when more <code>pop</code> than
-<code>push</code> operations are issued on a stack). Safety checking can be
-implemented mostly independent from the implementation details of the
-stack (usage of internal data structures). There are as well different
-ways of checking the safety. Therefore we say that safety checking is
-orthogonal to the stack core implementation.</p></div>
-<div class="paragraph"><p>With NX we can define stack-safety as a separate class using methods
-with the same names as the implementations before, and "mix" this
-behavior into classes or objects. The implementation of <code>Safety</code> in
-stack under-runs and to issue error messages, when this happens.</p></div>
-<div class="paragraph" id="xmp-class-safety"><div class="title">Listing 7: Class Safety</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Safety {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Implement stack safety by defining an additional
-</span> <span class='nx-comment'># instance variable named "count" that keeps track of
-</span> <span class='nx-comment'># the number of stacked elements. The methods of
-</span> <span class='nx-comment'># this class have the same names and argument lists
-</span> <span class='nx-comment'># as the methods of Stack; these methods "shadow"
-</span> <span class='nx-comment'># the methods of class Stack.
-</span> <span class='nx-comment'>#
-</span>
- <span class='nx-keyword'>:variable</span> count 0
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
- <span class='nx-keyword'>incr</span> :count
- <span class='nx-keyword'>next</span>
- }
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
- <span class='nx-keyword'>if</span> {<span class='nx-variable'>${</span><span class='nx-variable'>:count}</span> == 0} { <span class='nx-keyword'>error</span> <span class='nx-string'>"Stack empty!"</span> }
- <span class='nx-keyword'>incr</span> :count -1
- <span class='nx-keyword'>next</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p>Note that all the methods of the class <code>Safety</code> end with <code>next</code>.
-This command is a primitive command of NX, which calls the
-same-named method with the same argument list as the current
-invocation.</p></div>
-<div class="paragraph"><p>Assume we save the definition of the class <code>Stack</code> in a file named
-<code>Stack.tcl</code> and the definition of the class <code>Safety</code> in a file named
-<code>Safety.tcl</code> in the current directory. When we load the classes
-<code>Stack</code> and <code>Safety</code> into the same script (see the terminal dialog in
-e.g. a certain stack <code>s2</code> as a safe stack, while all other stacks
-(such as <code>s1</code>) might be still "unsafe". This can be achieved via the
-option <code>-mixin</code> at the object creation time (see line 9 in
-option <code>-mixin</code> mixes the class <code>Safety</code> into the new instance <code>s2</code>.</p></div>
-<div class="paragraph" id="xmp-using-class-safety"><div class="title">Listing 8: Using the Class Safety</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>% <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
-2.0
-% <span class='nx-keyword'>source</span> Stack.tcl
-::Stack
-% <span class='nx-keyword'>source</span> Safety.tcl
-::Safety
-% Stack <span class='nx-keyword'>create</span> s1
-::s1
-% Stack <span class='nx-keyword'>create</span> s2 -object-mixin Safety
-::s2
-% s2 push a
-% s2 pop
-a
-% s2 pop
-Stack empty!
-
-% s1 <span class='nx-keyword'>info</span> precedence
-::Stack ::nx::Object
-
-% s2 <span class='nx-keyword'>info</span> precedence
-::Safety ::Stack ::nx::Object</pre></div></div>
-<div class="paragraph"><p>When the method <code>push</code> of <code>s2</code> is called, first the method of the
-mixin class <code>Safety</code> will be invoked that increments the counter and
-continues with <code>next</code> to call the shadowed method, here the method
-<code>push</code> of the <code>Stack</code> implementation that actually pushes the item.
-The same happens, when <code>s2 pop</code> is invoked, first the method of
-<code>Safety</code> is called, then the method of the <code>Stack</code>. When the stack is
-empty (the value of <code>count</code> reaches 0), and <code>pop</code> is invoked, the
-mixin class <code>Safety</code> generates an error message (raises an exception),
-and does not invoke the method of the <code>Stack</code>.</p></div>
-<div class="paragraph"><p>The last two commands in
-<a href="#xmp-using-class-safety">Listing 8</a>
-use introspection to query for the objects
-<code>s1</code> and <code>s2</code> in which order the involved classes are processed. This
-order is called the <code>precedence order</code> and is obtained via <code>info
-precedence</code>. We see that the mixin class <code>Safety</code> is only in use for
-<code>s2</code>, and takes there precedence over <code>Stack</code>. The common root class
-<code>nx::Object</code> is for both <code>s1</code> and <code>s2</code> the base class.</p></div>
-<div class="imageblock" id="img-per-object-mixin" style="text-align:center;">
-<div class="content">
-<img src="per-object-mixin.png" alt="per-object-mixin.png" />
-</div>
-<div class="title">Figure 9. Per-object Mixin</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>Note that in <a href="#xmp-using-class-safety">Listing 8</a>,
-the class <code>Safety</code> is only mixed into a single object (here
-<code>s2</code>), therefore we refer to this case as a <em>per-object mixin</em>.
-<a href="#img-per-object-mixin">Figure 9</a> shows the class
-diagram, where the class <code>Safety</code> is used as a per-object mixin for
-<code>s2</code>.</p></div>
-<div class="paragraph"><p>The mixin class <code>Safety</code> can be used as well in other ways, such as e.g. for
-defining classes of safe stacks:</p></div>
-<div class="paragraph" id="xmp-class-safestack"><div class="title">Listing 10: Class SafeStack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Create a safe stack class by using Stack and mixin
-</span><span class='nx-comment'># Safety
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> SafeStack -superclasses Stack -mixins Safety
-
-SafeStack <span class='nx-keyword'>create</span> s3</pre></div></div>
-<div class="paragraph"><p>The difference of a per-class mixin and a per-object mixin is that
-the per-class mixin is applicable to all instances of the
-class. Therefore, we call these mixins also sometimes instance mixins.
-In our example in <a href="#xmp-class-safestack">Listing 10</a>,
-<code>Safety</code> is mixed into the definition of
-<code>SafeStack</code>. Therefore, all instances of the class <code>SafeStack</code> (here
-the instance <code>s3</code>) will be using the safety definitions.</p></div>
-<div class="imageblock" id="img-per-class-mixin" style="text-align:center;">
-<div class="content">
-<img src="per-class-mixin.png" alt="per-class-mixin.png" />
-</div>
-<div class="title">Figure 11. Per-class Mixin</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p><a href="#img-per-class-mixin">Figure 11</a> shows the class diagram
-for this definition.
-Note that we could use <code>Safety</code> as well as a per-class mixin on
-<code>Stack</code>. In this case, all stacks would be safe stacks and we could
-not provide a selective feature selection (which might be perfectly
-fine).</p></div>
-</div>
-<div class="sect2">
-<h3 id="_define_different_kinds_of_stacks">2.4. Define Different Kinds of Stacks</h3>
-<div class="paragraph"><p>The definition of <code>Stack</code> is generic and allows all kind of elements
-to be stacked. Suppose, we want to use the generic stack definition,
-but a certain stack (say, stack <code>s4</code>) should be a stack for integers
-only. This behavior can be achieved by the same means as introduced
-already in <a href="#xmp-object-stack">Listing 5</a>, namely
-object-specific methods.</p></div>
-<div class="paragraph" id="xmp-object-integer-stack"><div class="title">Listing 12: Object Integer Stack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>Stack <span class='nx-keyword'>create</span> s4 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Create a stack with a object-specific method
-</span> <span class='nx-comment'># to check the type of entries
-</span> <span class='nx-comment'>#
-</span>
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> push {thing:integer} {
- <span class='nx-keyword'>next</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p>The program snippet in <a href="#xmp-object-integer-stack">Listing 12</a> defines an instance <code>s4</code> of the class
-<code>Stack</code> and provides an object specific method for <code>push</code> to implement
-an integer stack. The method <code>pull</code> is the same for the integer stack
-as for all other stacks, so it will be reused as usual from the class
-<code>Stack</code>. The object-specific method <code>push</code> of <code>s4</code> has a value
-constraint in its argument list (<code>thing:integer</code>) that makes sure
-that only integers can be stacked. In case the argument is not an
-integer, an exception will be raised. Of course, one could perform the
-value constraint checking as well in the body of the method <code>proc</code> by
-accepting an generic argument and by performing the test for the value
-in the body of the method. In the case, the passed value is an
-integer, the <code>push</code> method of <a href="#xmp-object-integer-stack">Listing 12</a> calls <code>next</code>, and therefore calls the
-shadowed generic definition of <code>push</code> as provided by <code>Stack</code>.</p></div>
-<div class="paragraph" id="xmp-class-integer-stack"><div class="title">Listing 13: Class IntegerStack</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> IntegerStack -superclass Stack {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Create a Stack accepting only integers
-</span> <span class='nx-comment'>#
-</span>
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing:integer} {
- <span class='nx-keyword'>next</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p>An alternative approach is shown in
-<a href="#xmp-class-integer-stack">Listing 13</a>, where the class
-<code>IntegerStack</code> is defined, using the same method definition
-as <code>s4</code>, this time on the class level.</p></div>
-</div>
-<div class="sect2">
-<h3 id="_define_object_specific_methods_on_classes">2.5. Define Object Specific Methods on Classes</h3>
-<div class="paragraph"><p>In our previous examples we defined methods provided by classes
-(applicable for their instances) and object-specific methods (methods
-defined on objects, which are only applicable for these objects). In
-this section, we introduce methods that are defined on the class
-objects. Such methods are sometimes called <em>class methods</em> or
-<em>static methods</em>.</p></div>
-<div class="paragraph"><p>In NX classes are objects, they are specialized objects with
-additional methods. Methods for classes are often used for managing
-the life-cycles of the instances of the classes (we will come to this
-point in later sections in more detail). Since classes are objects, we
-can use exactly the same notation as above to define class methods by
-using <code>object method</code>. The methods defined on the class object are
-in all respects identical with object specific methods shown in the
-examples above.</p></div>
-<div class="paragraph" id="xmp-stack2"><div class="title">Listing 14: Class Stack2</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack2 {
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> available_stacks {} {
- <span class='nx-keyword'>return</span> [<span class='nx-keyword'>llength</span> [<span class='nx-keyword'>:info</span> instances]]
- }
-
- <span class='nx-keyword'>:variable</span> things {}
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
- }
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
- <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
- <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
- <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
- }
-}
-
-Stack2 <span class='nx-keyword'>create</span> s1
-Stack2 <span class='nx-keyword'>create</span> s2
-
-<span class='nx-keyword'>puts</span> [Stack2 available_stacks]</pre></div></div>
-<div class="paragraph"><p>The class <code>Stack2</code> in <a href="#xmp-stack2">Listing 14</a> consists of the
-earlier definition of the class <code>Stack</code> and is extended by the
-class-specific method <code>available_stacks</code>, which returns the
-current number of instances of the stack. The final command <code>puts</code>
-(line 26) prints 2 to the console.</p></div>
-<div class="imageblock" id="img-stack2" style="text-align:center;">
-<div class="content">
-<img src="stack2.png" alt="stack2.png" />
-</div>
-<div class="title">Figure 15. Stack2</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>The class diagram in <a href="#img-stack2">Figure 15</a> shows the
-diagrammatic representation of the class object-specific method
-<code>available_stacks</code>. Since every class is a specialization of the
-common root class <code>nx::Object</code>, the common root class is often omitted
-from the class diagrams, so it was omitted here as well in the diagram.</p></div>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_basic_language_features_of_nx">3. Basic Language Features of NX</h2>
-<div class="sectionbody">
-<div class="sect2">
-<h3 id="_variables_and_properties">3.1. Variables and Properties</h3>
-<div class="paragraph"><p>In general, NX does not need variable declarations. It allows one to
-create or modify variables on the fly by using for example the Tcl
-commands <code>set</code> and <code>unset</code>. Depending on the variable name (or more
-precisely, depending on the variable name’s prefix consisting of
-colons "<code>:</code>") a variable is either local to a method, or it is an
-instance variable, or a global variable. The rules are:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-A variable without any colon prefix refers typically to a method
- scoped variable. Such a variable is created during the invocation
- of the method, and it is deleted, when the method ends. In the
- example below, the variable <code>a</code> is method scoped.
-</p>
-</li>
-<li>
-<p>
-A variable with a single colon prefix refers to an instance
- variable. An instance variable is part of the object; when the
- object is destroyed, its instance variables are deleted as well. In the
- example below, the variable <code>b</code> is an instance variable.
-</p>
-</li>
-<li>
-<p>
-A variable with two leading colons refers to a global variable. The
- lifespan of a globale variable ends when the variable is explicitly
- unset or the script terminates. Variables, which are placed in Tcl
- namespaces, are also global variables. In the example below, the
- variable <code>c</code> is a global variable.
-</p>
-</li>
-</ul></div>
-<div class="paragraph" id="xmp-var-resolver"><div class="title">Listing 16: Scopes of Variables</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo {
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo args {...}
- <span class='nx-comment'># "a" is a method scoped variable
-</span> <span class='nx-keyword'>set</span> a 1
- <span class='nx-comment'># "b" is an Instance variable
-</span> <span class='nx-keyword'>set</span> :b 2
- <span class='nx-comment'># "c" is a global variable/namespaced variable
-</span> <span class='nx-keyword'>set</span> ::c 3
- }
-}</pre></div></div>
-<div class="paragraph"><p><a href="#xmp-var-resolver">Listing 16</a> shows a method <code>foo</code>
-of some class <code>Foo</code> referring to differently scoped variables.</p></div>
-<div class="sect3">
-<h4 id="_properties_configurable_instance_variables">3.1.1. Properties: Configurable Instance Variables</h4>
-<div class="paragraph"><p>As described above, there is no need to declare instance variables in
-NX. In many cases, a developer might want to define some value
-constraints for variables, or to provide defaults, or to make
-variables configurable upon object creation. Often, variables are
-"inherited", meaning that the variables declared in a general class
-are also available in a more specialized class. For these purposes NX
-provides <em>variable handlers</em> responsible for the management of
-instance variables. We distinguish in NX between configurable
-variables (called <code>property</code>) and variables that are not configurable
-(called <code>variable</code>).</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>A <strong>property</strong> is a definition of a configurable instance variable.</p></div>
-</div></div>
-<div class="paragraph"><p>The term configurable means that (a) one can provide at creation time of
-an instance a value for this variable, and (b), one can query the
-value via the accessor function <code>cget</code> and (c), one can change the
-value of the variable via <code>configure</code> at runtime. Since the general
-accessor function <code>cget</code> and <code>configure</code> are available, an application
-developer does not have to program own accessor methods. When value
-checkers are provided, each time, the value of the variable is to be
-changed, the constrained are checked as well.</p></div>
-<div class="imageblock" id="img-person-student" style="text-align:center;">
-<div class="content">
-<img src="person-student.png" alt="person-student.png" />
-</div>
-<div class="title">Figure 17. Classes Person and Student</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>The class diagram above defines the classes <code>Person</code> and
-<code>Student</code>. For both classes, configurable instance variable are
-specified by defining these as properties. The listing below shows
-an implementation of this conceptual model in NX.</p></div>
-<div class="paragraph" id="xmp-properties"><div class="title">Listing 18: Properties</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Define a class Person with properties "name"
-</span><span class='nx-comment'># and "birthday"
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person {
- <span class='nx-keyword'>:property</span> name:required
- <span class='nx-keyword'>:property</span> birthday
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Define a class Student as specialization of Person
-</span><span class='nx-comment'># with additional properties
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Student -superclass Person {
- <span class='nx-keyword'>:property</span> matnr:required
- <span class='nx-keyword'>:property</span> {oncampus:boolean true}
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Create instances using configure parameters
-</span><span class='nx-comment'># for the initialization
-</span><span class='nx-comment'>#
-</span>Person <span class='nx-keyword'>create</span> p1 -name Bob
-Student <span class='nx-keyword'>create</span> s1 -name Susan -matnr 4711
-
-<span class='nx-comment'># Access property value via accessor method
-</span><span class='nx-keyword'>puts</span> <span class='nx-string'>"The name of s1 is [s1 cget -name]"</span></pre></div></div>
-<div class="paragraph"><p>By defining <code>name</code> and <code>birthday</code> as properties of <code>Person</code>, NX makes
-these configurable. When we create an instance of <code>Person</code> named
-<code>p1</code>, we can provide a value for e.g. the name by specifying <code>-name</code>
-during creation. The properties result in non-positional configure parameters
-which can be provided in any order. In our listing, we create an instance of
-<code>Person</code> using the configure parameter <code>name</code> and provide the value of
-<code>Bob</code> to the instance variable <code>name</code>.</p></div>
-<div class="paragraph"><p>The class <code>Student</code> is defined as a specialization of <code>Person</code> with
-two additional properties: <code>matnr</code> and <code>oncampus</code>. The property
-<code>matnr</code> is required (it has to be provided, when an instance of this
-class is created), and the property <code>oncampus</code> is boolean, and is per
-default set to <code>true</code>. Note that the class <code>Student</code> inherits the
-properties of <code>Person</code>. So, <code>Student</code> has four properties in total.</p></div>
-<div class="paragraph"><p>The property definitions provide the <code>configure parameters</code> for
-instance creation. Many other languages require such parameters to be
-passed via arguments of a constructor, which is often error prone,
-when values are to be passed to superclasses. Also in dynamic
-languages, the relationships between classes can be easily changed,
-and different superclasses might have different requirements in their
-constructors. The declarative approach in NX reduces the need for
-tailored constructor methods significantly.</p></div>
-<div class="paragraph"><p>Note that the property <code>matnr</code> of class <code>Student</code> is required. This
-means, that if we try to create an instance of <code>Student</code>, a runtime
-exception will be triggered. The property <code>oncamups</code> is boolean and
-contains a default value. Providing a default value means that
-whenever we create an instance of this class the object will contain
-such an instance variable, even when we provide no value via the
-configure parameters.</p></div>
-<div class="paragraph"><p>In our listing, we create an instance of <code>Student</code> using the two
-configure parameters <code>name</code> and <code>matnr</code>. Finally, we use method <code>cget</code>
-to obtain the value of the instance variable <code>name</code> of object <code>s1</code>.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_non_configurable_instance_variables">3.1.2. Non-configurable Instance Variables</h4>
-<div class="paragraph"><p>In practice, not all instance variables should be configurable. But
-still, we want to be able to provide defaults similar to
-properties. To define non-configurable instance variables the
-predefined method <code>variable</code> can be used. Such instance variables are
-often used for e.g. keeping the internal state of an object. The
-usage of <code>variable</code> is in many respects similar to <code>property</code>. One
-difference is, that <code>property</code> uses the same syntax as for method
-parameters, whereas <code>variable</code> receives the default value as a
-separate argument (similar to the <code>variable</code> command in plain
-Tcl). The introductory Stack example in <a href="#xmp-class-stack">Listing 2</a> uses already the method <code>variable</code>.</p></div>
-<div class="paragraph" id="xmp-variable"><div class="title">Listing 19: Declaring Variables</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
- <span class='nx-keyword'>:variable</span> x 1
- <span class='nx-comment'># ...
-</span>}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Derived -superclass Base {
- <span class='nx-keyword'>:variable</span> y 2
- <span class='nx-comment'># ...
-</span>}
-
-<span class='nx-comment'># Create instance of the class Derived
-</span>Derived <span class='nx-keyword'>create</span> d1
-
-<span class='nx-comment'># Object d1 has instance variables
-</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div>
-<div class="paragraph"><p>Note that the variable definitions are inherited in the same way as
-properties. The example in <a href="#xmp-variable">Listing 19</a> shows a
-class <code>Derived</code> that inherits from <code>Base</code>. When an instance <code>d1</code> is
-created, it will contain the two instance variables <code>x</code> and <code>y</code>.
-Note that the variable declarations from <code>property</code> and <code>variable</code> are
-used to initialize (and to configure) the instances variables of an object.</p></div>
-<div class="paragraph" id="xmp-constructor"><div class="title">Listing 20: Setting Variables in the Constructor</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base2 {
- <span class='nx-comment'># ...
-</span> <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
- <span class='nx-keyword'>set</span> :x 1
- <span class='nx-comment'># ....
-</span> }
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Derived2 -superclass Base2 {
- <span class='nx-comment'># ...
-</span> <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
- <span class='nx-keyword'>set</span> :y 2
- <span class='nx-keyword'>next</span>
- <span class='nx-comment'># ....
-</span> }
-}
-
-<span class='nx-comment'># Create instance of the class Derived2
-</span>Derived2 <span class='nx-keyword'>create</span> d2</pre></div></div>
-<div class="paragraph"><p>In many other object oriented languages, the instance variables are
-initialized solely by the constructor (similar to class <code>Derived2</code> in
-<a href="#xmp-constructor">Listing 20</a>). This approach is certainly
-also possible in NX. Note that the approach using constructors
-requires an explicit method chaining between the constructors and is
-less declarative than the approach in NX using <code>property</code> and <code>variable</code>.</p></div>
-<div class="paragraph"><p>Both, <code>property</code> and <code>variable</code> provide much more functionalities. One
-can for example declare <code>public</code>, <code>protected</code> or <code>private</code> accessor
-methods, or one can define variables to be incremental (for
-e.g. adding values to a list of values), or one can define variables
-specific behavior.</p></div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_method_definitions">3.2. Method Definitions</h3>
-<div class="paragraph"><p>The basic building blocks of an object oriented program are object and
-classes, which contain named pieces of code, the methods.</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p><strong>Methods</strong> are subroutines (pieces of code) associated with objects
-and/or classes. A method has a name, receives optionally arguments
-during invocation and returns a value.</p></div>
-</div></div>
-<div class="paragraph"><p>Plain Tcl provides subroutines, which are not associated with objects
-or classes. Tcl distinguishes between +proc+s (scripted subroutines)
-and commands (system-languages implemented subroutines).</p></div>
-<div class="paragraph"><p>Methods might have different scopes, defining, on which kind of
-objects these methods are applicable to. These are described in more
-detail later on. For the time being, we deal here with methods defined
-on classes, which are applicable for the instance of these classes.</p></div>
-<div class="sect3">
-<h4 id="_scripted_methods">3.2.1. Scripted Methods</h4>
-<div class="paragraph"><p>Since NX is a scripting language, most methods are most likely
-scripted methods, in which the method body contains Tcl code.</p></div>
-<div class="paragraph" id="xmp-fido1"><div class="title">Listing 21: Scripted method</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Define a class
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
-
- <span class='nx-comment'># Define a scripted method for the class
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span>
- }
-}
-
-<span class='nx-comment'># Create an instance of the class
-</span>Dog <span class='nx-keyword'>create</span> fido
-
-<span class='nx-comment'># The following line prints "::fido Bark, bark, bark."
-</span>fido bark</pre></div></div>
-<div class="paragraph"><p>In the example above we create a class <code>Dog</code> with a scripted method
-named <code>bark</code>. The method body defines the code, which is executed when
-the method is invoked. In this example, the method <code>bar</code> prints out a
-line on the terminal starting with the object name (this is determined
-by the built in command <code>self</code>) followed by "Bark, bark, bark.". This
-method is defined on a class and applicable to instances of the class
-(here the instance <code>fido</code>).</p></div>
-</div>
-<div class="sect3">
-<h4 id="_c_implemented_methods">3.2.2. C-implemented Methods</h4>
-<div class="paragraph"><p>Not all of the methods usable in NX are scripted methods; many
-predefined methods are defined in the underlying system language,
-which is typically C. For example, in <a href="#xmp-fido1">Listing 21</a> we
-used the method <code>create</code> to create the class <code>Dog</code> and to create the
-dog instance <code>fido</code>. These methods are implemented in C in the next
-scripting framework.</p></div>
-<div class="paragraph"><p>C-implemented methods are not only provided by the underlying
-framework but might be as well defined by application developers. This
-is an advanced topic, not covered here. However, application developer
-might reuse some generic C code to define their own C-implemented
-methods. Such methods are for example <em>accessors</em>, <em>forwarders</em> and
-<em>aliases</em>.</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>An <strong>accessor method</strong> is a method that accesses instance
-variables of an object. A call to an accessor
-without arguments uses the accessor as a getter, obtaining the actual
-value of the associated variable. A call to an accessor with an
-argument uses it as a setter, setting the value of the associated
-variable.</p></div>
-</div></div>
-<div class="paragraph"><p>NX provides support for C-implemented accessor methods. Accessors have
-already been mentioned in the section about properties. When
-the option <code>-accessor public|protected|private</code> is provided to a
-<code>variable</code> or <code>property</code> definition, NX creates automatically a
-same-named accessors method.</p></div>
-<div class="paragraph" id="xmp-fido2"><div class="title">Listing 22: Accessor Methods</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
- <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} { Tail <span class='nx-keyword'>create</span> [<span class='nx-keyword'>self</span>]::tail}
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Tail {
- <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {length:double 5}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> wag {} {<span class='nx-keyword'>return</span> Joy}
-}
-
-<span class='nx-comment'># Create an instance of the class
-</span>Dog <span class='nx-keyword'>create</span> fido
-
-<span class='nx-comment'># Use the accessor "length" as a getter, to obtain the value
-</span><span class='nx-comment'># of a property. The following call returns the length of the
-</span><span class='nx-comment'># tail of fido
-</span>fido::tail length get
-
-<span class='nx-comment'># Use the accessor "length" as a setter, to alter the value
-</span><span class='nx-comment'># of a property. The following call changes the length of
-</span><span class='nx-comment'># the tail of fido
-</span>fido::tail length <span class='nx-keyword'>set</span> 10
-
-<span class='nx-comment'># Proving an invalid values will raise an error
-</span>fido::tail length <span class='nx-keyword'>set</span> <span class='nx-string'>"Hello"</span></pre></div></div>
-<div class="paragraph"><p><a href="#xmp-fido2">Listing 22</a> shows an extended example, where every dog
-has a tail. The object <code>tail</code> is created as a subobject of the dog in
-the constructor <code>init</code>. The subobject can be accessed by providing the
-full name of the subobject <code>fido::tail</code>. The method <code>length</code> is an
-C-implemented accessor, that enforces the value constraint (here a
-floating point number, since length uses the value constraint
-<code>double</code>). Line 25 will therefore raise an exception, since the
-provided values cannot be converted to a double number.</p></div>
-<div class="paragraph" id="xmp-fido3"><div class="title">Listing 23: Forwarder Methods</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
- <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
- Tail <span class='nx-keyword'>create</span> [<span class='nx-keyword'>self</span>]::tail
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>forward</span> wag [<span class='nx-keyword'>self</span>]::tail wag
- }
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Tail {
- <span class='nx-keyword'>:property</span> {length 5}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> wag {} {<span class='nx-keyword'>return</span> Joy}
-}
-
-<span class='nx-comment'># Create an instance of the class
-</span>Dog <span class='nx-keyword'>create</span> fido
-
-<span class='nx-comment'># The invocation of "fido wag" is delegated to "fido::tail wag".
-</span><span class='nx-comment'># Therefore, the following method returns "Joy".
-</span>fido wag</pre></div></div>
-<div class="paragraph"><p><a href="#xmp-fido3">Listing 23</a> again extends the example by adding a
-forwarder named <code>wag</code> to the object (e.g. <code>fido</code>). The forwarder
-redirects all calls of the form <code>fido wag</code> with arbitrary arguments to
-the subobject <code>fido::tail</code>.</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>A <strong>forwarder method</strong> is a
-C-implemented method that redirects an invocation for a certain method
-to either a method of another object or to some other method of the
-same object. Forwarding an invocation of a method to some other
-object is a means of delegation.</p></div>
-</div></div>
-<div class="paragraph"><p>The functionality of the forwarder can just as well be implemented as
-a scripted method, but for the most common cases, the forward
-implementation is more efficient, and the <code>forward</code> method expresses
-the intention of the developer.</p></div>
-<div class="paragraph"><p>The method <code>forwarder</code> has several options to change e.g. the order of
-the arguments, or to substitute certain patterns in the argument list
-etc. This will be described in later sections.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_method_aliases">3.2.3. Method-Aliases</h4>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>An <strong>alias method</strong> is a means to register either an existing method,
-or a Tcl proc, or a Tcl command as a method with the provided
-name on a class or object.</p></div>
-</div></div>
-<div class="paragraph"><p>In some way, the method alias is a restricted form of a forwarder,
-though it does not support delegation to different objects or argument
-reordering. The advantage of the method alias compared to a forwarder
-is that it has close to zero overhead, especially for aliasing
-c-implemented methods.</p></div>
-<div class="paragraph" id="xmp-fido4"><div class="title">Listing 24: Method-Alias</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
-
- <span class='nx-comment'># Define a public alias for the method "bark"
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>alias</span> warn [<span class='nx-keyword'>:info</span> <span class='nx-keyword'>method</span> handle bark]
- <span class='nx-comment'># ...
-</span>}
-
-<span class='nx-comment'># Create an instance of the class
-</span>Dog <span class='nx-keyword'>create</span> fido
-
-<span class='nx-comment'># The following line prints "::fido Bark, bark, bark."
-</span>fido warn</pre></div></div>
-<div class="paragraph"><p><a href="#xmp-fido4">Listing 24</a> extends the last example by defining an
-alias for the method <code>bark</code>. The example only shows the bare
-mechanism. In general, method aliases are very powerful means for
-reusing pre-existing functionality. The full object system of NX and
-XOTcl2 is built from aliases, reusing functionality provided by the
-next scripting framework under different names. Method aliases
-are as well a means for implementing traits in NX.</p></div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_method_protection">3.3. Method Protection</h3>
-<div class="paragraph"><p>All kinds of methods might have different kind of protections in NX.
-The call-protection defines from which calling context methods might
-be called. The Next Scripting Framework supports as well redefinition
-protection for methods.</p></div>
-<div class="paragraph"><p>NX distinguishes between <code>public</code>, <code>protected</code> and <code>private</code> methods,
-where the default call-protection is <code>protected</code>.</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>A <strong>public</strong> method can be called from every context. A <strong>protected</strong>
-method can only be invoked from the same object. A <strong>private</strong> method
-can only be invoked from methods defined on the same entity
-(defined on the same class or on the same object) via the invocation
-with the local flag (i.e. "<code>: -local foo</code>").</p></div>
-</div></div>
-<div class="paragraph"><p>All kind of method protections are applicable for all kind of methods,
-either scripted or C-implemented.</p></div>
-<div class="paragraph"><p>The distinction between public and protected leads to interfaces for
-classes and objects. Public methods are intended for consumers of
-these entities. Public methods define the intended ways of providing
-methods for external usages (usages, from other objects or
-classes). Protected methods are intended for the implementor of the
-class or subclasses and not for public usage. The distinction between
-protected and public reduces the coupling between consumers and the
-implementation, and offers more flexibility to the developer.</p></div>
-<div class="paragraph" id="xmp-protected-method"><div class="title">Listing 25: Protected Methods</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo {
-
- <span class='nx-comment'># Define a public method
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
- <span class='nx-comment'># ....
-</span> <span class='nx-keyword'>return</span> [:helper]
- }
-
- <span class='nx-comment'># Define a protected method
-</span> <span class='nx-keyword'>:method</span> helper {} {
- <span class='nx-keyword'>return</span> 1
- }
-}
-
-<span class='nx-comment'># Create an instance of the class:
-</span>Foo <span class='nx-keyword'>create</span> f1
-
-<span class='nx-comment'># The invocation of the public method "foo" returns 1
-</span>f1 foo
-
-<span class='nx-comment'># The invocation of the protected method "helper" raises an error:
-</span>f1 helper</pre></div></div>
-<div class="paragraph"><p>The example above uses <code>:protected method helper …</code>. We could have
-used here as well <code>:method helper …</code>, since the default method
-call-protection is already protected.</p></div>
-<div class="paragraph"><p>The method call-protection of <code>private</code> goes one step further and
-helps to hide implementation details also for implementors of
-subclasses. Private methods are a means for avoiding unanticipated name
-clashes. Consider the following example:</p></div>
-<div class="paragraph" id="xmp-private-method"><div class="title">Listing 26: Private Methods</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
- <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> helper {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> + <span class='nx-variable'>$b</span>}}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a b} {: -local helper <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Sub -superclass Base {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a b} {: -local helper <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
- <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> helper {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> * <span class='nx-variable'>$b</span>}}
- <span class='nx-keyword'>:create</span> s1
-}
-
-s1 foo 3 4 ;<span class='nx-comment'># returns 7
-</span>s1 bar 3 4 ;<span class='nx-comment'># returns 12
-</span>s1 helper 3 4 ;<span class='nx-comment'># raises error: unable to dispatch method helper</span></pre></div></div>
-<div class="paragraph"><p>The base class implements a public method <code>foo</code> using the helper
-method named <code>helper</code>. The derived class implements a as well a public
-method <code>bar</code>, which is also using a helper method named <code>helper</code>. When
-an instance <code>s1</code> is created from the derived class, the method <code>foo</code>
-is invoked which uses in turn the private method of the base
-class. Therefore, the invocation <code>s1 foo 3 4</code> returns its sum. If
-the <code>local</code> flag had not beed used in helper, <code>s1</code> would
-have tried to call the helper of <code>Sub</code>, which would be incorrect. For
-all other purposes, the private methods are "invisible" in all
-situations, e.g., when mixins are used, or within the <code>next</code>-path, etc.</p></div>
-<div class="paragraph"><p>By using the <code>-local</code> flag at the call site it is possible to invoke
-only the local definition of the method. If we would call the method
-without this flag, the resolution order would be the standard
-resolution order, starting with filters, mixins, object methods
-and the full intrinsic class hierarchy.</p></div>
-<div class="paragraph"><p>NX supports the modifier <code>private</code> for methods and properties. In all
-cases <code>private</code> is an instrument to avoid unanticipated interactions
-and means actually "accessible for methods defined on the same entity
-(object or class)". The main usage for <code>private</code> is to improve
-locality of the code e.g. for compositional operations.</p></div>
-<div class="paragraph"><p>In order to improve locality for properties, a private property
-defines therefore internally a variable with a different name to avoid
-unintended interactions. The variable should be accessed via the
-private accessor, which can be invoked with the <code>-local</code> flag. In the
-following example class <code>D</code> introduces a private property with the
-same name as a property in the superclass.</p></div>
-<div class="paragraph" id="xmp-private-properties"><div class="title">Listing 27: Private Properties</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Define a class C with a property "x" and a public accessor
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {x c}
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Define a subclass D with a private property "x"
-</span><span class='nx-comment'># and a method bar, which is capable of accessing
-</span><span class='nx-comment'># the private property.
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D -superclass C {
- <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>private</span> {x d}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {p} {<span class='nx-keyword'>return</span> [: -local <span class='nx-variable'>$p</span> get]}
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># The private and public (or protected) properties
-</span><span class='nx-comment'># define internally separate variable that do not
-</span><span class='nx-comment'># conflict.
-</span><span class='nx-comment'>#
-</span>D <span class='nx-keyword'>create</span> d1
-<span class='nx-keyword'>puts</span> [d1 x get] ;<span class='nx-comment'># prints "c"
-</span><span class='nx-keyword'>puts</span> [d1 bar x] ;<span class='nx-comment'># prints "d"</span></pre></div></div>
-<div class="paragraph"><p>Without the <code>private</code> definition of the property, the definition of
-property <code>x</code> in class <code>D</code> would shadow the
-definition of the property in the superclass <code>C</code> for its instances
-(<code>d1 x</code> or <code>set :x</code> would return <code>d</code> instead of <code>c</code>).</p></div>
-</div>
-<div class="sect2">
-<h3 id="_applicability_of_methods">3.4. Applicability of Methods</h3>
-<div class="paragraph"><p>As defined above, a method is a subroutine defined on an object or
-class. This object (or class) contains the method. If the object (or
-class) is deleted, the contained methods will be deleted as well.</p></div>
-<div class="sect3">
-<h4 id="_instance_methods">3.4.1. Instance Methods</h4>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>Typically, methods are defined on a class, and the methods defined on the
-class are applicable to the instances (direct or indirect) of this
-class. These methods are called <strong>instance methods</strong>.</p></div>
-</div></div>
-<div class="paragraph"><p>In the following example method, <code>foo</code> is an instance method defined
-on class <code>C</code>.</p></div>
-<div class="paragraph" id="xmp-instance-applicable"><div class="title">Listing 28: Methods applicable for instances</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
- <span class='nx-keyword'>:create</span> c1
-}
-
-<span class='nx-comment'># Method "foo" is defined on class "C"
-</span><span class='nx-comment'># and applicable to the instances of "C"
-</span>c1 foo</pre></div></div>
-<div class="paragraph"><p>There are many programming languages that only allow these types of methods.
-However, NX also allows methods to be defined on objects.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_object_methods">3.4.2. Object Methods</h4>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>Methods defined on objects are <strong>object methods</strong>. Object
-methods are only applicable on the object, on which they are defined.
-Object methods cannot be inherited from other objects.</p></div>
-</div></div>
-<div class="paragraph"><p>The following example defines an object method <code>bar</code> on the
-instance <code>c1</code> of class <code>C</code>, and as well as the object specific method
-<code>baz</code> defined on the object <code>o1</code>. An object method is defined
-via <code>object method</code>.</p></div>
-<div class="paragraph"><p>Note that we can define a object method that shadows (redefines)
-for this object methods provided from classes.</p></div>
-<div class="paragraph" id="xmp-object-applicable1"><div class="title">Listing 29: Object Method</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
- <span class='nx-keyword'>:create</span> c1 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 2}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {<span class='nx-keyword'>return</span> 3}
- }
-}
-
-<span class='nx-comment'># Method "bar" is an object specific method of "c1"
-</span>c1 bar
-
-<span class='nx-comment'># object-specific method "foo" returns 2
-</span>c1 foo
-
-<span class='nx-comment'># Method "baz" is an object specific method of "o1"
-</span><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o1 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {} {<span class='nx-keyword'>return</span> 4}
-}
-o1 baz</pre></div></div>
-</div>
-<div class="sect3">
-<h4 id="_class_methods">3.4.3. Class Methods</h4>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>A <strong>class method</strong> is a method defined on a class, which is only
-applicable to the class object itself. The class method is actually
-an object method of the class object.</p></div>
-</div></div>
-<div class="paragraph"><p>In NX, all classes are objects. Classes are in NX special kind of
-objects that have e.g. the ability to create instances and to provide
-methods for the instances. Classes manage their instances. The general
-method set for classes is defined on the meta-classes (more about
-this later).</p></div>
-<div class="paragraph"><p>The following example defines a public class method <code>bar</code> on class
-<code>C</code>. The class method is specified by using the modifier <code>object</code> in
-front of <code>method</code> in the method definition command.</p></div>
-<div class="paragraph" id="xmp-object-applicable2"><div class="title">Listing 30: Class Methods</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Define a class method "bar" and an instance
-</span> <span class='nx-comment'># method "foo"
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {<span class='nx-keyword'>return</span> 2}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Create an instance of the current class
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:create</span> c1
-}
-
-<span class='nx-comment'># Method "bar" is a class method of class "C"
-</span><span class='nx-comment'># therefore applicable on the class object "C"
-</span>C bar
-
-<span class='nx-comment'># Method "foo" is an instance method of "C"
-</span><span class='nx-comment'># therefore applicable on instance "c1"
-</span>c1 foo
-
-<span class='nx-comment'># When trying to invoke the class method on the
-</span><span class='nx-comment'># instance, an error will be raised.
-</span>c1 bar</pre></div></div>
-<div class="paragraph"><p>In some other object-oriented programming languages, class methods
-are called "static methods".</p></div>
-</div>
-</div>
-<div class="sect2">
-<h3 id="_ensemble_methods">3.5. Ensemble Methods</h3>
-<div class="paragraph"><p>NX provides <em>ensemble methods</em> as a means to structure the method name
-space and to group related methods. Ensemble methods are similar in
-concept to Tcl’s ensemble commands.</p></div>
-<div class="exampleblock">
-<div class="content">
-<div class="paragraph"><p>An <strong>ensemble method</strong> is a form of a hierarchical method consisting of
-a container method and sub-methods. The first argument of the
-container method is interpreted as a selector (the sub-method). Every
-sub-method can be an container method as well.</p></div>
-</div></div>
-<div class="paragraph"><p>Ensemble methods provide a means to group related commands together,
-and they are extensible in various ways. It is possible to add
-sub-methods at any time to existing ensembles. Furthermore, it is
-possible to extend ensemble methods via mixin classes.</p></div>
-<div class="paragraph"><p>The following example defines an ensemble method for <code>string</code>. An
-ensemble method is defined when the provide method name contains a
-space.</p></div>
-<div class="paragraph" id="xmp-ensemble-methods"><div class="title">Listing 31: Ensemble Method</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
-
- <span class='nx-comment'># Define an ensemble method "string" with sub-methods
-</span> <span class='nx-comment'># "length", "tolower" and "info"
-</span>
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string length"</span> {x} {....}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string tolower"</span> {x} {...}
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string info"</span> {x} {...}
- <span class='nx-comment'>#...
-</span> <span class='nx-keyword'>:create</span> c1
-}
-
-<span class='nx-comment'># Invoke the ensemble method
-</span>c1 <span class='nx-keyword'>string</span> length <span class='nx-string'>"hello world"</span></pre></div></div>
-</div>
-<div class="sect2">
-<h3 id="_method_resolution">3.6. Method Resolution</h3>
-<div class="paragraph"><p>When a method is invoked, the applicable method is searched in the
-following order:</p></div>
-Per-object Mixins -> Per-class Mixins -> Object -> Intrinsic Class Hierarchy
-<div class="paragraph"><p>In the case, no mixins are involved, first the object is searched for
-an object method with the given name, and then the class hierarchy
-of the object. The method can be defined multiple times on the search
-path, so some of these method definitions might be <em>shadowed</em> by the
-more specific definitions.</p></div>
-<div class="paragraph" id="xmp-method-resolution"><div class="title">Listing 32: Method Resolution with Intrinsic Classes</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
- <span class='nx-keyword'>return</span> <span class='nx-string'>"C foo: [next]"</span>
- }
-}
-
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D -superclass C {
-
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
- <span class='nx-keyword'>return</span> <span class='nx-string'>"D foo: [next]"</span>
- }
-
- <span class='nx-keyword'>:create</span> d1 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {} {
- <span class='nx-keyword'>return</span> <span class='nx-string'>"d1 foo: [next]"</span>
- }
- }
-}
-
-<span class='nx-comment'># Invoke the method foo
-</span>d1 foo
-<span class='nx-comment'># result: "d1 foo: D foo: C foo: "
-</span>
-<span class='nx-comment'># Query the precedence order from NX via introspection
-</span>d1 <span class='nx-keyword'>info</span> precedence
-<span class='nx-comment'># result: "::D ::C ::nx::Object"</span></pre></div></div>
-<div class="paragraph"><p>Consider the example in
-<a href="#xmp-method-resolution">Listing 32</a>. When the method
-<code>foo</code> is invoked on object <code>d1</code>, the object method has the highest
-precedence and is therefore invoked. The object methods shadows
-the same-named methods in the class hierarchy, namely the method <code>foo</code>
-of class <code>D</code> and the method <code>foo</code> of class <code>C</code>. The shadowed methods
-can be still invoked, either via the primitive <code>next</code> or via method
-handles (we used already method handles in the section about method
-aliases). In the example above, <code>next</code> calls the shadowed method and
-add their results to the results of every method. So, the final result
-contains parts from <code>d1</code>, <code>D</code> and <code>C</code>. Note that the topmost <code>next</code>
-in method <code>foo</code> of class <code>C</code> shadows no method <code>foo</code> and simply
-returns empty (and not an error message).</p></div>
-<div class="paragraph"><p>The introspection method <code>info precedence</code> provides information about
-the order, in which classes processed during method resolution.</p></div>
-<div class="paragraph" id="xmp-method-resolution2"><div class="title">Listing 33: Method Resolution with Mixin Classes</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> M1 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} { <span class='nx-keyword'>return</span> <span class='nx-string'>"M1 foo: [next]"</span>}
-}
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> M2 {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} { <span class='nx-keyword'>return</span> <span class='nx-string'>"M2 foo: [next]"</span>}
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># "d1" is created based on the definitions of the last example
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># Add the methods from "M1" as per-object mixin to "d1"
-</span>d1 <span class='nx-keyword'>object</span> mixins add M1
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Add the methods from "M2" as per-class mixin to class "C"
-</span>C mixins add M2
-
-<span class='nx-comment'># Invoke the method foo
-</span>d1 foo
-<span class='nx-comment'># result: "M1 foo: M2 foo: d1 foo: D foo: C foo: "
-</span>
-<span class='nx-comment'># Query the precedence order from NX via introspection
-</span>d1 <span class='nx-keyword'>info</span> precedence
-<span class='nx-comment'># result: "::M1 ::M2 ::D ::C ::nx::Object"</span></pre></div></div>
-<div class="paragraph"><p>The example in <a href="#xmp-method-resolution2">Listing 33</a> is
-an extension of the previous example. We define here two additional
-classes <code>M1</code> and <code>M2</code> which are used as per-object and per-class
-mixins. Both classes define the method <code>foo</code>, these methods shadow
-the definitions of the intrinsic class hierarchy. Therefore an
-invocation of <code>foo</code> on object <code>d1</code> causes first an invocation of
-method in the per-object mixin.</p></div>
-<div class="paragraph" id="xmp-method-resolution3"><div class="title">Listing 34: Method Invocation Flags</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># "d1" is created based on the definitions of the last two examples,
-</span><span class='nx-comment'># the mixins "M1" and "M2" are registered.
-</span><span class='nx-comment'>#
-</span><span class='nx-comment'># Define a public object method "bar", which calls the method
-</span><span class='nx-comment'># "foo" which various invocation options:
-</span><span class='nx-comment'>#
-</span>d1 <span class='nx-keyword'>public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {
- <span class='nx-keyword'>puts</span> [:foo]
- <span class='nx-keyword'>puts</span> [: -local foo]
- <span class='nx-keyword'>puts</span> [: -intrinsic foo]
- <span class='nx-keyword'>puts</span> [: -system foo]
-}
-
-<span class='nx-comment'># Invoke the method "bar"
-</span>d1 bar</pre></div></div>
-<div class="paragraph"><p>In the first line of the body of method <code>bar</code>, the method <code>foo</code> is
-called as usual with an implicit receiver, which defaults to the
-current object (therefore, the call is equivalent to <code>d1 foo</code>). The
-next three calls show how to provide flags that influence the method
-resolution. The flags can be provided between the colon and the method
-name. These flags are used rather seldom but can be helpful in some
-situations.</p></div>
-<div class="paragraph"><p>The invocation flag <code>-local</code> means that the method has to be resolved
-from the same place, where the current method is defined. Since the
-current method is defined as a object method, <code>foo</code> is resolved as
-a object method. The effect is that the mixin definitions are
-ignored. The invocation flag <code>-local</code> was already introduced int the
-section about method protection, where it was used to call <em>private</em>
-methods.</p></div>
-<div class="paragraph"><p>The invocation flag <code>-intrinsic</code> means that the method has to be resolved
-from the intrinsic definitions, meaning simply without mixins. The
-effect is here the same as with the invocation flag <code>-local</code>.</p></div>
-<div class="paragraph"><p>The invocation flag <code>-system</code> means that the method has to be resolved
-from basic - typically predefined - classes of the object system. This
-can be useful, when script overloads system methods, but still want to
-call the shadowed methods from the base classes. In our case, we have
-no definitions of <code>foo</code> on the base clases, therefore an error message
-is returned.</p></div>
-<div class="paragraph"><p>The output of <a href="#xmp-method-resolution3">Listing 34</a> is:</p></div>
-<div class="listingblock">
-<div class="content">
-<pre><code> M1 foo: M2 foo: d1 foo: D foo: C foo:
- d1 foo: D foo: C foo:
- d1 foo: D foo: C foo:
- ::d1: unable to dispatch method 'foo'</code></pre>
-</div></div>
-</div>
-<div class="sect2">
-<h3 id="_parameters">3.7. Parameters</h3>
-<div class="paragraph"><p>NX provides a generalized mechanism for passing values to either
-methods (we refer to these as <em>method parameters</em>) or to objects
-(these are called <em>configure parameters</em>). Both kind of parameters
-might have different features, such as:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-Positional and non-positional parameters
-</p>
-</li>
-<li>
-<p>
-Required and non-required parameters
-</p>
-</li>
-<li>
-<p>
-Default values for parameters
-</p>
-</li>
-<li>
-<p>
-Value-checking for parameters
-</p>
-</li>
-<li>
-<p>
-Multiplicity of parameters
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>TODO: complete list above and provide a short summary of the section</p></div>
-<div class="paragraph"><p>Before we discuss method and configure parameters in more detail, we
-describe the parameter features in the subsequent sections based on
-method parameters.</p></div>
-<div class="sect3">
-<h4 id="_positional_and_non_positional_parameters">3.7.1. Positional and Non-Positional Parameters</h4>
-<div class="paragraph"><p>If the position of a parameter in the list of formal arguments
-(e.g. passed to a function) is significant for its meaning, this is a
-<em>positional</em> parameter. If the meaning of the parameter is independent
-of its position, this is a <em>non-positional</em> parameter. When we call a
-method with positional parameters, the meaning of the parameters (the
-association with the argument in the argument list of the method) is
-determined by its position. When we call a method with non-positional
-parameters, their meaning is determined via a name passed with the
-argument during invocation.</p></div>
-<div class="paragraph" id="xmp-posnonpos"><div class="title">Listing 35: Positional and Non-Positional Method Parameters</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o1 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Method foo has positional parameters:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x y} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Method bar has non-positional parameters:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {-x -y} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Method baz has non-positional and
-</span> <span class='nx-comment'># positional parameters:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {-x -y a} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x? [info exists x] y? [info exists y] a=$a"</span>
- }
-}
-
-<span class='nx-comment'># invoke foo (positional parameters)
-</span>o1 foo 1 2
-
-<span class='nx-comment'># invoke bar (non-positional parameters)
-</span>o1 bar -y 3 -x 1
-o1 bar -x 1 -y 3
-
-<span class='nx-comment'># invoke baz (positional and non-positional parameters)
-</span>o1 baz -x 1 100
-o1 baz 200
-o1 baz -- -y</pre></div></div>
-<div class="paragraph"><p>Consider the example in <a href="#xmp-posnonpos">Listing 35</a>. The method
-<code>foo</code> has the argument list <code>x y</code>. This means that the first argument
-is passed in an invocation like <code>o1 foo 1 2</code> to <code>x</code> (here, the value
-<code>1</code>), and the second argument is passed to <code>y</code> (here the value <code>2</code>).
-Method <code>bar</code> has in contrary just with non-positional arguments. Here
-we pass the names of the parameter together with the values. In the
-invocation <code>o1 bar -y 3 -x 1</code> the names of the parameters are prefixed
-with a dash ("-"). No matter whether in which order we write the
-non-positional parameters in the invocation (see line 30 and 31 in
-<a href="#xmp-posnonpos">Listing 35</a>) in both cases the variables <code>x</code>
-and <code>y</code> in the body of the method <code>bar</code> get the same values assigned
-(<code>x</code> becomes <code>1</code>, <code>y</code> becomes <code>3</code>).</p></div>
-<div class="paragraph"><p>It is certainly possible to combine positional and non-positional
-arguments. Method <code>baz</code> provides two non-positional parameter (<code>-y</code>
-and <code>-y</code>) and one positional parameter (namely <code>a</code>). The invocation in
-line 34 passes the value of <code>1</code> to <code>x</code> and the value of <code>100</code> to <code>a</code>.
-There is no value passed to <code>y</code>, therefore value of <code>y</code> will be
-undefined in the body of <code>baz</code>, <code>info exists y</code> checks for the
-existence of the variable <code>y</code> and returns <code>0</code>.</p></div>
-<div class="paragraph"><p>The invocation in line 35 passes only a value to the positional
-parameter. A more tricky case is in line 36, where we want to pass
-<code>-y</code> as a value to the positional parameter <code>a</code>. The case is more
-tricky since syntactically the argument parser might consider <code>-y</code> as
-the name of one of the non-positional parameter. Therefore we use <code>--</code>
-(double dash) to indicate the end of the block of the non-positional
-parameters and therefore the value of <code>-y</code> is passed to <code>a</code>.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_optional_and_required_parameters">3.7.2. Optional and Required Parameters</h4>
-<div class="paragraph"><p>Per default positional parameters are required, and non-positional
-parameters are optional (they can be left out). By using parameter
-options, we can as well define positional parameters, which are
-optional, and non-positional parameters, which are required.</p></div>
-<div class="paragraph" id="xmp-optional-req"><div class="title">Listing 36: Optional and Required Method Parameters</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o2 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Method foo has one required and one optional
-</span> <span class='nx-comment'># positional parameter:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:required y:optional} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y? [info exists y]"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Method bar has one required and one optional
-</span> <span class='nx-comment'># non-positional parameter:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {-x:required -y:optional} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y? [info exists y]"</span>
- }
-}
-
-<span class='nx-comment'># invoke foo (one optional positional parameter is missing)
-</span>o2 foo 1</pre></div></div>
-<div class="paragraph"><p>The example in <a href="#xmp-optional-req">Listing 36</a> defined method <code>foo</code>
-with one required and one optional positional parameter. For this
-purpose we use the parameter options <code>required</code> and <code>optional</code>. The
-parameter options are separated from the parameter name by a colon. If
-there are multiple parameter options, these are separated by commas
-(we show this in later examples).</p></div>
-<div class="paragraph"><p>The parameter definition <code>x:required</code> for method <code>foo</code> is equivalent
-to <code>x</code> without any parameter options (see e.g. previous example),
-since positional parameters are per default required. The invocation
-in line 21 of <a href="#xmp-optional-req">Listing 36</a> will lead to an
-undefined variable <code>y</code> in method <code>foo</code>, because no value us passed to
-the optional parameter. Note that only trailing positional parameters might be
-optional. If we would call method <code>foo</code> of <a href="#xmp-posnonpos">Listing 35</a> with only one argument, the system would raise an
-exception.</p></div>
-<div class="paragraph"><p>Similarly, we define method <code>bar</code> in <a href="#xmp-optional-req">Listing 36</a> with one required and one optional non-positional
-parameter. The parameter definition <code>-y:optional</code> is equivalent to
-<code>-y</code>, since non-positional parameter are per default optional.
-However, the non-positional parameter <code>-x:required</code> is required. If we
-invoke <code>bar</code> without it, the system will raise an exception.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_default_values_for_parameters">3.7.3. Default Values for Parameters</h4>
-<div class="paragraph"><p>Optional parameters might have a default value. This default value is used,
-when no argument is provided for the corresponding parameter. Default values can be
-specified for positional and non-positional parameters.</p></div>
-<div class="paragraph" id="xmp-default-value"><div class="title">Listing 37: Method Parameters with Default Values</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o3 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Positional parameter with default value:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {{x 1} {y 2}} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Non-positional parameter with default value:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {{-x 10} {-y 20}} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
- }
-}
-
-<span class='nx-comment'># use default values
-</span>o3 foo
-o3 bar</pre></div></div>
-<div class="paragraph"><p>In order to define a default value for a parameter, the parameter
-specification must be of the form of a 2 element list, where the
-second argument is the default value. See for an example in
-<a href="#xmp-default-value">Listing 37</a>.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_value_constraints">3.7.4. Value Constraints</h4>
-<div class="paragraph"><p>NX provides value constraints for all kind of parameters. By
-specifying value constraints a developer can restrict the permissible
-values for a parameter and document the expected values in the source
-code. Value checking in NX is conditional, it can be turned on or off
-in general or on a per-usage level (more about this later). The same
-mechanisms can be used not only for input value checking, but as well
-for return value checking (we will address this point as well later).</p></div>
-<div class="sect4">
-<h5 id="_built_in_value_constraints">Built-in Value Constraints</h5>
-<div class="paragraph"><p>NX comes with a set of built-in value constraints, which can be
-extended on the scripting level. The built-in checkers are either the
-native checkers provided directly by the Next Scripting Framework (the
-most efficient checkers) or the value checkers provided by Tcl through
-<code>string is …</code>. The built-in checkers have as well the advantage that
-they can be used also at any time during bootstrap of an object
-system, at a time, when e.g. no objects or methods are defined. The
-same checkers are used as well for all C-implemented primitives of NX
-and the Next Scripting Framework.</p></div>
-<div class="imageblock" id="img-value-checkers" style="text-align:center;">
-<div class="content">
-<img src="value-checkers.png" alt="value-checkers.png" />
-</div>
-<div class="title">Figure 38. General Applicable Value Checkers in NX</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p><a href="#img-value-checkers">Figure 38</a> shows the built-in
-general applicable value checkers available in NX, which can be used
-for all method and configure parameters. In the next step, we show how to
-use these value-checkers for checking permissible values for method
-parameters. Then we will show, how to provide more detailed value
-constraints.</p></div>
-<div class="paragraph" id="xmp-value-check"><div class="title">Listing 39: Method Parameters with Value Constraints</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o4 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Positional parameter with value constraints:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:integer o<span class='nx-keyword'>:object</span>,optional} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x o? [info exists o]"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Non-positional parameter with value constraints:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {{-x:integer 10} {-verbose:boolean false}} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x verbose=$verbose"</span>
- }
-}
-
-<span class='nx-comment'># The following invocation raises an exception, since the
-</span><span class='nx-comment'># value "a" for parameter "x" is not an integer
-</span>o4 foo a</pre></div></div>
-<div class="paragraph"><p>Value constraints are specified as parameter options in the parameter
-specifications. The parameter specification <code>x:integer</code> defines <code>x</code> as
-a required positional parameter which value is constraint to an
-integer. The parameter specification <code>o:object,optional</code> shows how to
-combine multiple parameter options. The parameter <code>o</code> is an optional
-positional parameter, its value must be an object (see
-<a href="#xmp-value-check">Listing 39</a>). Value constraints are
-specified exactly the same way for non-positional parameters (see
-method <code>bar</code> in <a href="#xmp-value-check">Listing 39</a>).</p></div>
-<div class="paragraph" id="xmp-check-parameterized"><div class="title">Listing 40: Parameterized Value Constraints</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Create classes for Person and Project
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Project
-
-<span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o5 {
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Parameterized value constraints
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> work {
- -person<span class='nx-keyword'>:object</span>,type=Person
- -project<span class='nx-keyword'>:object</span>,type=Project
- } {
- <span class='nx-comment'># ...
-</span> }
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Create a Person and a Project instance
-</span><span class='nx-comment'>#
-</span>Person <span class='nx-keyword'>create</span> gustaf
-Project <span class='nx-keyword'>create</span> nx
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Use method with value constraints
-</span><span class='nx-comment'>#
-</span>o5 work -person gustaf -project nx</pre></div></div>
-<div class="paragraph"><p>The native checkers <code>object</code>, <code>class</code>, <code>metaclass</code> and <code>baseclass</code> can
-be further specialized with the parameter option <code>type</code> to restrict
-the permissible values to instances of certain classes. We can use for
-example the native value constraint <code>object</code> either for testing
-whether an argument is some object (without further constraints, as in
-<a href="#xmp-default-value">Listing 37</a>, method <code>foo</code>), or we can
-constrain the value further to some type (direct or indirect instance
-of a class). This is shown by method <code>work</code> in
-<a href="#xmp-check-parameterized">Listing 40</a> which requires
-the parameter <code>-person</code> to be an instance of class <code>Person</code> and the
-parameter <code>-project</code> to be an instance of class <code>Project</code>.</p></div>
-</div>
-<div class="sect4">
-<h5 id="_scripted_value_constraints">Scripted Value Constraints</h5>
-<div class="paragraph"><p>The set of predefined value checkers can be extended by application
-programs via defining methods following certain conventions. The user
-defined value checkers are defined as methods of the class <code>nx::Slot</code>
-or of one of its subclasses or instances. We will address such cases
-in the next sections. In the following example we define two new
-value checkers on class <code>nx::Slot</code>. The first value checker is called
-<code>groupsize</code>, the second one is called <code>choice</code>.</p></div>
-<div class="paragraph" id="xmp-user-types"><div class="title">Listing 41: Scripted Value Checker for Method Parameters</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Value checker named "groupsize"
-</span><span class='nx-comment'>#
-</span>::nx::Slot <span class='nx-keyword'>method</span> type=groupsize {name value} {
- <span class='nx-keyword'>if</span> {<span class='nx-variable'>$value</span> < 1 || <span class='nx-variable'>$value</span> > 6} {
- <span class='nx-keyword'>error</span> <span class='nx-string'>"Value '$value' of parameter $name is not between 1 and 6"</span>
- }
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Value checker named "choice" with extra argument
-</span><span class='nx-comment'>#
-</span>::nx::Slot <span class='nx-keyword'>method</span> type=choice {name value arg} {
- <span class='nx-keyword'>if</span> {<span class='nx-variable'>$value</span> ni [<span class='nx-keyword'>split</span> <span class='nx-variable'>$arg</span> |]} {
- <span class='nx-keyword'>error</span> <span class='nx-string'>"Value '$value' of parameter $name not in permissible values $arg"</span>
- }
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Create an application class D
-</span><span class='nx-comment'># using the new value checkers
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D {
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a:groupsize} {
- <span class='nx-comment'># ...
-</span> }
- <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a:choice,arg=red|yellow|green b:choice,arg=good|bad} {
- <span class='nx-comment'># ...
-</span> }
-}
-
-D <span class='nx-keyword'>create</span> d1
-
-<span class='nx-comment'># testing "groupsize";
-</span><span class='nx-comment'># the second call (with value 10) will raise an exception:
-</span>d1 foo 2
-d1 foo 10
-
-<span class='nx-comment'># testing "choice"
-</span><span class='nx-comment'># the second call (with value pink for parameter a)
-</span><span class='nx-comment'># will raise an exception:
-</span>d1 bar green good
-d1 bar pink bad</pre></div></div>
-<div class="paragraph"><p>In order to define a checker <code>groupsize</code> a method of the name
-<code>type=groupsize</code> is defined. This method receives two arguments,
-<code>name</code> and <code>value</code>. The first argument is the name of the parameter
-(mostly used for the error message) and the second parameter is
-provided value. The value checker simply tests whether the provided
-value is between 1 and 3 and raises an exception if this is not the
-case (invocation in line 36 in <a href="#xmp-user-types">Listing 41</a>).</p></div>
-<div class="paragraph"><p>The checker <code>groupsize</code> has the permissible values defined in its
-method’s body. It is as well possible to define more generic checkers
-that can be parameterized. For this parameterization, one can pass an
-argument to the checker method (last argument). The checker <code>choice</code>
-can be used for restricting the values to a set of predefined
-constants. This set is defined in the parameter specification. The
-parameter <code>a</code> of method <code>bar</code> in <a href="#xmp-user-types">Listing 41</a>
-is restricted to the values <code>red</code>, <code>yellow</code> or <code>green</code>, and the
-parameter <code>b</code> is restricted to <code>good</code> or <code>bad</code>. Note that the syntax
-of the permissible values is solely defined by the definition of the
-value checker in lines 13 to 17. The invocation in line 39 will be ok,
-the invocation in line 40 will raise an exception, since <code>pink</code> is not
-allowed.</p></div>
-<div class="paragraph"><p>If the same checks are used in many places in the program,
-defining names for the value checker will be the better choice since
-it improves maintainability. For seldom used kind of checks, the
-parameterized value checkers might be more convenient.</p></div>
-</div>
-</div>
-<div class="sect3">
-<h4 id="_multiplicity">3.7.5. Multiplicity</h4>
-<div class="sidebarblock">
-<div class="content">
-<div class="paragraph"><p><strong>Multiplicity</strong> is used to define whether a parameter should receive
-single or multiple values.</p></div>
-</div></div>
-<div class="paragraph"><p>A multiplicity specification has a lower and an upper bound. A lower
-bound of <code>0</code> means that the value might be empty. A lower bound of <code>1</code>
-means that the parameter needs at least one value. The upper bound
-might be <code>1</code> or <code>n</code> (or synonymously <code>*</code>). While the upper bound of
-<code>1</code> states that at most one value has to be passed, the upper bound of
-<code>n</code> says that multiple values are permitted. Other kinds of
-multiplicity are currently not allowed.</p></div>
-<div class="paragraph"><p>The multiplicity is written as parameter option in the parameter
-specification in the form <em>lower-bound</em>..<em>upper-bound</em>. If no
-multiplicity is defined the default multiplicity is <code>1..1</code>, which
-means: provide exactly one (atomic) value (this was the case in the
-previous examples).</p></div>
-<div class="paragraph" id="xmp-multiplicity"><div class="title">Listing 42: Method Parameters with Explicit Multiplicity</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o6 {
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Positional parameter with an possibly empty
-</span> <span class='nx-comment'># single value
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:integer,0..1} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Positional parameter with an possibly empty
-</span> <span class='nx-comment'># list of values value
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {x:integer,0..n} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
- }
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># Positional parameter with a non-empty
-</span> <span class='nx-comment'># list of values
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {x:integer,1..n} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
- }
-}</pre></div></div>
-<div class="paragraph"><p><a href="#xmp-multiplicity">Listing 42</a> contains three examples for
-positional parameters with different multiplicities. Multiplicity is
-often combined with value constraints. A parameter specification of
-the form <code>x:integer,0..n</code> means that the parameter <code>x</code> receives a list
-of integers, which might be empty. Note that the value constraints are
-applied to every single element of the list.</p></div>
-<div class="paragraph"><p>The parameter specification <code>x:integer,0..1</code> means that <code>x</code> might be
-an integer or it might be empty. This is one style of specifying that
-no explicit value is passed for a certain parameter. Another style is
-to use required or optional parameters. NX does not enforce any
-particular style for handling unspecified values.</p></div>
-<div class="paragraph"><p>All the examples in <a href="#xmp-multiplicity">Listing 42</a> are for
-single positional parameters. Certainly, multiplicity is fully
-orthogonal with the other parameter features and can be used as well
-for multiple parameters, non-positional parameter, default values,
-etc.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_defaults_substitution">3.7.6. Defaults substitution</h4>
-<div class="paragraph"><p>Optional object and method parameters can set a default value. Recall
-that default values can be specified for positional and non-positional
-parameters, alike. This default value is used to define a
-corresponding method-local and object variable, respectively, and to
-set it to the default value. By default, the default value is taken
-literally (without any substitutions). Default values can also be
-preprocessed into a final value using Tcl substitution as provided by
-the Tcl <code>[subst]</code> command. To control the kind of substitutions to be
-performed, the parameter option <code>substdefault</code> can be provided.</p></div>
-<div class="paragraph" id="substdefault"><div class="title">Listing 43: Default-value substitution using <code>substdefault</code></div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> ::D
-<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> ::C {
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># By default all substitutions (command, variable, control
-</span> <span class='nx-comment'># characters) are active, when "substdefault" is used:
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:property</span> {d<span class='nx-keyword'>:object</span>,type=::D,substdefault {[::D <span class='nx-keyword'>new</span>]}}
-
- <span class='nx-comment'>#
-</span> <span class='nx-comment'># The actual property values are computed and
-</span> <span class='nx-comment'># set at instantiation time.
-</span> <span class='nx-comment'>#
-</span> <span class='nx-keyword'>:create</span> ::c
-}
-
-::c <span class='nx-keyword'>cget</span> -d</pre></div></div>
-<div class="paragraph"><p><a href="#substdefault">Listing 43</a> uses <code>substdefault</code>
-to provide a default value for the property <code>d</code>. In this example, the
-default value is a fresh instance of
-class <code>::D</code>. When the parameter option <code>substdefault</code> is used
-default, all substitution kinds of Tcl are active: command, variable, and
-backslash substitution. <code>substdefault</code> can be
-parametrized to include or to exclude any combination of substitution
-kinds by providing a bitmask:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-<code>substdefault=0b111</code>: all substitutions active (default)
-</p>
-</li>
-<li>
-<p>
-<code>substdefault=0b100</code>: substitute backslashes only (like <code>subst -novariables -nocommands</code>)
-</p>
-</li>
-<li>
-<p>
-<code>substdefault=0b010</code>: substitute variables only (like <code>subst -nobackslashes -nocommands</code>)
-</p>
-</li>
-<li>
-<p>
-<code>substdefault=0b001</code>: substitute commands only (like <code>subst -nobackslashes -novariables</code>)
-</p>
-</li>
-<li>
-<p>
-<code>substdefault=0b000</code>: substitute nothing (like <code>subst -nobackslashes -nocommands -novariables</code>, noop)
-</p>
-</li>
-</ul></div>
-</div>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_advanced_language_features">4. Advanced Language Features</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>…</p></div>
-<div class="sect2">
-<h3 id="_objects_classes_and_meta_classes">4.1. Objects, Classes and Meta-Classes</h3>
-<div class="paragraph"><p>…</p></div>
-</div>
-<div class="sect2">
-<h3 id="_resolution_order_and_next_path">4.2. Resolution Order and Next-Path</h3>
-<div class="paragraph"><p>…</p></div>
-</div>
-<div class="sect2">
-<h3 id="_details_on_method_and_configure_parameters">4.3. Details on Method and Configure Parameters</h3>
-<div class="paragraph"><p>The parameter specifications are used in NX for the following
-purposes. They are used for</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-the specification of input arguments of methods and commands, for
-</p>
-</li>
-<li>
-<p>
-the specification of return values of methods and commands, and for
-</p>
-</li>
-<li>
-<p>
-the specification for the initialization of objects.
-</p>
-</li>
-</ul></div>
-<div class="paragraph"><p>We refer to the first two as method parameters and the last one as
-configure parameters. The examples in the previous sections all parameter
-specification were specifications of method parameters.</p></div>
-<div class="sidebarblock">
-<div class="content">
-<div class="paragraph"><p><strong>Method parameters</strong> specify properties about permissible values passed
-to methods.</p></div>
-</div></div>
-<div class="paragraph"><p>The method parameter specify how methods are invoked, how the
-actual arguments are passed to local variables of the invoked method
-and what kind of checks should be performed on these.</p></div>
-<div class="sidebarblock">
-<div class="content">
-<div class="paragraph"><p><strong>Configure parameters</strong> are parameters that specify, how objects
-can be parameterized upon creation.</p></div>
-</div></div>
-<div class="paragraph"><p>Syntactically, configure parameters and method parameters are the same,
-although there are certain differences (e.g. some parameter options
-are only applicable for objects parameters, the list of object
-parameters is computed dynamically from the class structures, object
-parameters are often used in combination with special setter methods,
-etc.). Consider the following example, where we define the two
-application classes <code>Person</code> and <code>Student</code> with a few properties.</p></div>
-<div class="paragraph" id="xmp-object-parameters"><div class="title">Listing 44: Configure Parameters</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'>#
-</span><span class='nx-comment'># Define a class Person with properties "name"
-</span><span class='nx-comment'># and "birthday"
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person {
- <span class='nx-keyword'>:property</span> name:required
- <span class='nx-keyword'>:property</span> birthday
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Define a class Student as specialization of Person
-</span><span class='nx-comment'># with and additional property
-</span><span class='nx-comment'>#
-</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Student -superclass Person {
- <span class='nx-keyword'>:property</span> matnr:required
- <span class='nx-keyword'>:property</span> {oncampus:boolean true}
-}
-
-<span class='nx-comment'>#
-</span><span class='nx-comment'># Create instances using configure parameters
-</span><span class='nx-comment'># for the initialization
-</span><span class='nx-comment'>#
-</span>Person <span class='nx-keyword'>create</span> p1 -name Bob
-Student <span class='nx-keyword'>create</span> s1 -name Susan -matnr 4711
-
-<span class='nx-comment'># Access property value via "cget" method
-</span><span class='nx-keyword'>puts</span> <span class='nx-string'>"The name of s1 is [s1 cget -name]"</span></pre></div></div>
-<div class="paragraph"><p>The class <code>Person</code> has two properties <code>name</code> and <code>birthday</code>, where the
-property <code>name</code> is required, the property <code>birthday</code> is not. The
-class <code>Student</code> is a subclass of <code>Person</code> with the additional required
-property <code>matnr</code> and an optional property <code>oncampus</code> with the
-default value <code>true</code> (see <a href="#xmp-object-parameters">Listing 44</a>). The class diagram below visualizes these
-definitions.</p></div>
-<div class="imageblock" id="img-configure-parameters" style="text-align:center;">
-<div class="content">
-<img src="configure-parameter.png" alt="configure-parameter.png" />
-</div>
-<div class="title">Figure 45. System and Application Classes</div>
-</div>
-<div class="paragraph"><p></p></div>
-<div class="paragraph"><p>In NX, these definitions imply that instances of the class of <code>Person</code>
-have the properties <code>name</code> and <code>birthday</code> as <em>non-positional object
-parameters</em>. Furthermore it implies that instances of <code>Student</code> will
-have the configure parameters of <code>Person</code> augmented with the object
-parameters from <code>Student</code> (namely <code>matnr</code> and <code>oncampus</code>). Based on
-these configure parameters, we can create a <code>Person</code> named <code>Bob</code> and a
-<code>Student</code> named <code>Susan</code> with the matriculation number <code>4711</code> (see line
-23 and 24 in <<xmp-object-parameters,
-instance variables <code>name</code>, <code>matnr</code> and <code>oncampus</code> (the latter is
-initialized with the default value).</p></div>
-<div class="sect3">
-<h4 id="_configure_parameters_available_for_all_nx_objects">4.3.1. Configure Parameters available for all NX Objects</h4>
-<div class="paragraph"><p>The configure parameters are not limited to the application defined
-properties, also NX provides some predefined definitions. Since
-<code>Person</code> is a subclass of <code>nx::Object</code> also the configure parameters of
-<code>nx::Object</code> are inherited. In the introductory stack example, we used
-<code>-mixins</code> applied to an object to denote per-object mixins (see
-<a href="#xmp-using-class-safety">Listing 8</a>). Since <code>mixins</code>
-is defined as a parameter on <code>nx::Object</code> it can be used as an object
-parameter <code>-mixins</code> for all objects in NX. To put it in other words,
-every object can be configured to have per-object mixins. If we would
-remove this definition, this feature would be removed as well.</p></div>
-<div class="paragraph"><p>As shown in the introductory examples, every object can be configured
-via a scripted initialization block (the optional scripted block
-specified at object creation as last argument; see
-<a href="#xmp-object-stack">Listing 5</a> or
-<a href="#xmp-object-integer-stack">Listing 12</a>). The
-scripted block and its meaning are as well defined by the means of
-configure parameters. However, this configure parameter is positional (last
-argument) and optional (it can be omitted). The following listing shows
-the configure parameters of <code>Person p1</code> and <code>Student s1</code>.</p></div>
-<div class="paragraph" id="xmp-object-parameter-list"><div class="title">Listing 46: Computed Actual Configure Parameter</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>Configure parameters <span class='nx-keyword'>for</span> Person p1:
- Command:
- p1 <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
- Result:
- -name <span class='nx-placeholder'>/value/</span> ?-birthday <span class='nx-placeholder'>/value/</span>? ?-object-mixins /mixinreg .../<span class='nx-placeholder'>?
- ?</span>-class /<span class='nx-keyword'>class</span>/? ?-object-filters /filterreg .../? ?/__initblock/?
-
-Configure parameter <span class='nx-keyword'>for</span> Student s1:
- Command:
- s1 <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
- Result:
- ?-oncampus <span class='nx-placeholder'>/boolean/</span>? -matnr <span class='nx-placeholder'>/value/</span> -name <span class='nx-placeholder'>/value/</span>
- ?-birthday <span class='nx-placeholder'>/value/</span>? ?-object-mixins /mixinreg .../? ?-class /<span class='nx-keyword'>class</span>/<span class='nx-placeholder'>?
- ?</span>-object-filters /filterreg .../? ?/__initblock/?</pre></div></div>
-<div class="paragraph"><p>The given parameter show, how (a) objects can be configured
-at runtime or (b) how new instances can be configured
-at creation time via the <code>new</code> or <code>create</code> methods.
-Introspection can be used to obtain the configuration
-parameters from an object via
-<code>p1 info lookup parameters configure</code>
-(returning the configure parameters currently applicable for
-<code>configure</code> or <code>cget</code>) or from a class
-<code>Person info lookup parameters create</code> on a class
-(returning the configure parameters applicable when an object
-of this class is created)</p></div>
-<div class="paragraph"><p>The listed configure parameter types <code>mixinreg</code> and
-<code>filterreg</code> are for converting definitions of filters and mixins. The
-last value <code>__initblock</code> says that the content of this variable
-will be executed in the context of the object being created (before
-the constructor <code>init</code> is called). More about the configure parameter
-types later.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_configure_parameters_available_for_all_nx_classes">4.3.2. Configure Parameters available for all NX Classes</h4>
-<div class="paragraph"><p>Since classes are certain kind of objects, classes are parameterized
-in the same way as objects. A typical parameter for a class definition
-is the relation of the class to its superclass.In our example, we have
-specified, that <code>Student</code> has <code>Person</code> as superclass via the
-non-positional configure parameter <code>-superclass</code>. If no superclass is
-specified for a class, the default superclass is
-<code>nx::Object</code>. Therefore <code>nx::Object</code> is the default value for the
-parameter <code>superclass</code>.</p></div>
-<div class="paragraph"><p>Another frequently used parameter for classes is <code>-mixins</code> to denote
-per-class mixins (see e.g. the introductory Stack example in
-<a href="#xmp-class-safestack">Listing 10</a>), which is defined in
-the same way.</p></div>
-<div class="paragraph"><p>Since <code>Student</code> is an instance of the meta-class <code>nx::Class</code> it
-inherits the configure parameters from <code>nx::Class</code> (see class diagram
-<a href="#img-configure-parameters">Figure 45</a>).
-Therefore, one can use e.g. <code>-superclass</code> in the definition of classes.</p></div>
-<div class="paragraph"><p>Since <code>nx::Class</code> is a subclass of <code>nx::Object</code>, the meta-class
-<code>nx::Class</code> inherits the parameter definitions from the most general
-class <code>nx::Object</code>. Therefore, every class might as well be configured
-with a scripted initialization block the same way as objects can be
-configured. We used actually this scripted initialization block in
-most examples for defining the methods of the class. The following
-listing shows (simplified) the parameters applicable for <code>Class
-Student</code>.</p></div>
-<div class="paragraph" id="xmp-class-parameter-list"><div class="title">Listing 47: Parameters for Classes</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>Configure parameter <span class='nx-keyword'>for</span> <span class='nx-keyword'>class</span> <span class='nx-keyword'>nx::Class</span>
- Command:
- <span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
- Result:
- ?-superclass /<span class='nx-keyword'>class</span> .../? ?-mixins /mixinreg .../<span class='nx-placeholder'>?
- ?</span>-filters /filterreg .../? ?-object-mixins /mixinreg .../<span class='nx-placeholder'>?
- ?</span>-class /<span class='nx-keyword'>class</span>/? ?-object-filters /filterreg .../? ?/__initblock/?</pre></div></div>
-</div>
-<div class="sect3">
-<h4 id="_user_defined_parameter_types">4.3.3. User defined Parameter Types</h4>
-<div class="paragraph"><p>More detailed definition of the configure parameter types comes here.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_slot_classes_and_slot_objects">4.3.4. Slot Classes and Slot Objects</h4>
-<div class="paragraph"><p>In one of the previous sections, we defined scripted (application
-defined) checker methods on a class named <code>nx::Slot</code>. In general NX
-offers the possibility to define value checkers not only for all
-usages of parameters but as well differently for method parameters or
-configure parameters</p></div>
-<div class="imageblock" id="img-slots" style="text-align:center;">
-<div class="content">
-<img src="slots.png" alt="slots.png" />
-</div>
-<div class="title">Figure 48. Slot Classes and Objects</div>
-</div>
-<div class="paragraph"><p></p></div>
-</div>
-<div class="sect3">
-<h4 id="_attribute_slots">4.3.5. Attribute Slots</h4>
-<div class="paragraph"><p>Still Missing</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-return value checking
-</p>
-</li>
-<li>
-<p>
-switch
-</p>
-</li>
-<li>
-<p>
-initcmd …
-</p>
-</li>
-<li>
-<p>
-subst rules
-</p>
-</li>
-<li>
-<p>
-converter
-</p>
-</li>
-<li>
-<p>
-incremental slots
-</p>
-</li>
-</ul></div>
-</div>
-</div>
-</div>
-</div>
-<div class="sect1">
-<h2 id="_miscellaneous">5. Miscellaneous</h2>
-<div class="sectionbody">
-<div class="paragraph"><p>…</p></div>
-<div class="sect2">
-<h3 id="_profiling">5.1. Profiling</h3>
-<div class="paragraph"><p>…</p></div>
-</div>
-<div class="sect2">
-<h3 id="_unknown_handlers">5.2. Unknown Handlers</h3>
-<div class="paragraph"><p>NX provides two kinds of unknown handlers:</p></div>
-<div class="ulist"><ul>
-<li>
-<p>
-Unknown handlers for methods
-</p>
-</li>
-<li>
-<p>
-Unknown handlers for objects and classes
-</p>
-</li>
-</ul></div>
-<div class="sect3">
-<h4 id="_unknown_handlers_for_methods">5.2.1. Unknown Handlers for Methods</h4>
-<div class="paragraph"><p>Object and classes might be equipped
-with a method <code>unknown</code> which is called in cases, where an unknown
-method is called. The method unknown receives as first argument the
-called method followed by the provided arguments</p></div>
-<div class="paragraph" id="xmp-unknown-method"><div class="title">Listing 49: Unknown Method Handler</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>::nx::Object <span class='nx-keyword'>create</span> o {
- <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> <span class='nx-keyword'>unknown</span> {called_method args} {
- <span class='nx-keyword'>puts</span> <span class='nx-string'>"Unknown method '$called_method' called"</span>
- }
-}
-
-<span class='nx-comment'># Invoke an unknown method for object o:
-</span>o foo 1 2 3
-
-<span class='nx-comment'># Output will be: "Unknown method 'foo' called"</span></pre></div></div>
-<div class="paragraph"><p>Without any provision of an unknown method handler, an error will be
-raised, when an unknown method is called.</p></div>
-</div>
-<div class="sect3">
-<h4 id="_unknown_handlers_for_objects_and_classes">5.2.2. Unknown Handlers for Objects and Classes</h4>
-<div class="paragraph"><p>The next scripting framework provides in addition to unknown method
-handlers also a means to dynamically create objects and classes, when
-these are referenced. This happens e.g. when superclasses, mixins, or
-parent objects are referenced. This mechanism can be used to implement
-e.g. lazy loading of these classes. Nsf allows one to register multiple
-unknown handlers, each identified by a key (a unique name, different
-from the keys of other unknown handlers).</p></div>
-<div class="paragraph" id="xmp-unknown-class"><div class="title">Listing 50: Unknown Class Handler</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'>::nx::Class <span class='nx-keyword'>public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> __unknown {name} {
- <span class='nx-comment'># A very simple unknown handler, showing just how
-</span> <span class='nx-comment'># the mechanism works.
-</span> <span class='nx-keyword'>puts</span> <span class='nx-string'>"***** __unknown called with <$name>"</span>
- ::nx::Class <span class='nx-keyword'>create</span> <span class='nx-variable'>$name</span>
-}
-
-<span class='nx-comment'># Register an unknown handler as a method of ::nx::Class
-</span>::nsf::object::unknown::add nx {::nx::Class __unknown}
-
-::nx::Object <span class='nx-keyword'>create</span> o {
- <span class='nx-comment'># The class M is unknown at this point
-</span>
- <span class='nx-keyword'>:object</span> mixins add M
- <span class='nx-comment'># The line above has triggered the unknown class handler,
-</span> <span class='nx-comment'># class M is now defined
-</span>
- <span class='nx-keyword'>puts</span> [<span class='nx-keyword'>:info</span> <span class='nx-keyword'>object</span> mixins]
- <span class='nx-comment'># The output will be:
-</span> <span class='nx-comment'># ***** __unknown called with <::M>
-</span> <span class='nx-comment'># ::M
-</span>}</pre></div></div>
-<div class="paragraph"><p>The Next Scripting Framework allows one to add, query, delete and list unknown handlers.</p></div>
-<div class="paragraph" id="xmp-unknown-registration"><div class="title">Listing 51: Unknown Handler registration</div><p></p></div>
-<div class="listingblock">
-<div class="content"><style type='text/css'>
-.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
-table.nx {border-collapse: collapse; border-spacing: 3px;}
-.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
-.nx-string {color: #779977; font-weight: normal; font-style: italic;}
-.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
-.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
-.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
-.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
-</style>
-<pre class='nx'><span class='nx-comment'># Interface for unknown handlers:
-</span><span class='nx-comment'># nsf::object::unknown::add /key/ /handler/
-</span><span class='nx-comment'># nsf::object::unknown::get /key/
-</span><span class='nx-comment'># nsf::object::unknown::delete /key/
-</span><span class='nx-comment'># nsf::object::unknown::keys</span></pre></div></div>
-<div class="ulist bibliography"><div class="title">References</div><ul>
-<li>
-<p>
-<a id="Zdun"></a> U. Zdun, M. Strembeck, G. Neumann:
- Object-Based and Class-Based Composition of Transitive Mixins,
- Information and Software Technology, 49(8) 2007 .
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Zdun 1999a"></a> G. Neumann and U. Zdun: Filters as a
- language support for design patterns in object-oriented scripting
- languages. In Proceedings of COOTS’99, 5th Conference on
- Object-Oriented Technologies and Systems, San Diego, May 1999.
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Zdun 1999b"></a> G. Neumann and U. Zdun: Implementing
- object-specific design patterns using per-object mixins. In Proc. of
- NOSA`99, Second Nordic Workshop on Software Architecture, Ronneby,
- Sweden, August 1999.
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Zdun 1999c"></a> G. Neumann and U. Zdun: Enhancing
- object-based system composition through per-object mixins. In
- Proceedings of Asia-Pacific Software Engineering Conference (APSEC),
- Takamatsu, Japan, December 1999.
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Zdun 2000a"></a> G. Neumann and U. Zdun: XOTCL, an
- object-oriented scripting language. In Proceedings of Tcl2k: The
- 7th USENIX Tcl/Tk Conference, Austin, Texas, February 2000.
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Zdun 2000b"></a> G. Neumann and U. Zdun: Towards the Usage
- of Dynamic Object Aggregations as a Form of Composition In:
- Proceedings of Symposium of Applied Computing (SAC’00), Como,
- Italy, Mar 19-21, 2000.
-</p>
-</li>
-<li>
-<p>
-<a id="Neumann and Sobernig 2009"></a> G. Neumann, S. Sobernig: XOTcl 2.0 - A
- Ten-Year Retrospective and Outlook, in: Proceedings of the Sixteenth
- Annual Tcl/Tk Conference, Portland, Oregon, October, 2009.
-</p>
-</li>
-<li>
-<p>
-<a id="Ousterhout 1990"></a> J. K. Ousterhout: Tcl: An embeddable command
- language. In Proc. of the 1990 Winter USENIX Conference, January 1990.
-</p>
-</li>
-<li>
-<p>
-<a id="Ousterhout 1998"></a> J. K. Ousterhout: Scripting: Higher Level
- Programming for the 21st Century, IEEE Computer 31(3), March 1998.
-</p>
-</li>
-<li>
-<p>
-<a id="Wetherall and Lindblad 1995"></a> D. Wetherall and C. J. Lindblad: Extending Tcl for
- Dynamic Object-Oriented Programming. Proc. of the Tcl/Tk Workshop '95,
- July 1995.
-</p>
-</li>
-</ul></div>
-</div>
-</div>
-</div>
-</div>
-</div>
-<div id="footnotes"><hr /></div>
-<div id="footer">
-<div id="footer-text">
-Version 2.2.0<br />
-Last updated 2019-04-12 16:25:08 CEST
-</div>
-</div>
-</body>
-</html>
+</div>
+</div>
+<div id="content">
+<div id="preamble">
+<div class="sectionbody">
+<div class="sidebarblock">
+<div class="content">
+<div class="title">Abstract</div>
+<div class="paragraph"><p>This document provides a tutorial for the Next Scripting
+Language NX.</p></div>
+</div></div>
+<div class="paragraph"><p>The Next Scripting Language (NX) is a highly flexible object oriented
+scripting language based on Tcl <a href="#Ousterhout 1990">[Ousterhout 1990]</a>. NX is a successor
+of XOTcl 1 <a href="#Neumann and Zdun 2000a">[Neumann and Zdun 2000a]</a> and was developed based on 10
+years of experience with XOTcl in projects containing several hundred
+thousand lines of code. While XOTcl was the first language designed to
+provide <em>language support for design patterns</em>, the focus of the Next
+Scripting Framework and NX is on combining this with <em>Language
+Oriented Programming</em>. In many respects, NX was designed to ease the
+learning of the language for novices (by using a more mainstream
+terminology, higher orthogonality of the methods, less predefined
+methods), to improve maintainability (remove sources of common errors)
+and to encourage developers to write better structured programs (to
+provide interfaces) especially for large projects, where many
+developers are involved.</p></div>
+<div class="paragraph"><p>The Next Scripting Language is based on the Next Scripting Framework
+(NSF) which was developed based on the notion of language oriented
+programming. The Next Scripting Frameworks provides C-level support
+for defining and hosting multiple object systems in a single Tcl
+interpreter. The name of the Next Scripting Framework is derived from
+the universal method combinator "next", which was introduced in XOTcl.
+The combinator "next" serves as a single instrument for method
+combination with filters, per-object and transitive per-class mixin
+classes, object methods and multiple inheritance.</p></div>
+<div class="paragraph"><p>The definition of NX is fully scripted (e.g. defined in
+<code>nx.tcl</code>). The Next Scripting Framework is shipped with three language
+definitions, containing NX and XOTcl 2. Most of the existing XOTcl 1
+programs can be used without modification in the Next Scripting
+Framework by using XOTcl 2. The Next Scripting Framework requires Tcl
+8.5 or newer.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_nx_and_its_roots">1. NX and its Roots</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>Object oriented extensions of Tcl have quite a
+long history. Two of the most prominent early Tcl based OO languages
+were <em>incr Tcl</em> (abbreviated as itcl) and Object Tcl (<em>OTcl</em>
+<a href="#Wetherall and Lindblad 1995">[Wetherall and Lindblad 1995]</a>). While itcl provides a traditional
+C++/Java-like object system, OTcl was following the CLOS approach and
+supports a dynamic object system, allowing incremental class and
+object extensions and re-classing of objects.</p></div>
+<div class="paragraph"><p>Extended Object Tcl (abbreviated as XOTcl <a href="#Neumann and Zdun 2000a">[Neumann and Zdun 2000a]</a>)
+is a successor of OTcl and was the first language providing language
+support for design patterns. XOTcl extends OTcl by providing namespace
+support, adding assertions, dynamic object aggregations, slots and by
+introducing per-object and per-class filters and per-object and
+per-class mixins.</p></div>
+<div class="paragraph"><p>XOTcl was so far released in more than 30 versions. It is described in
+its detail in more than 20 papers and serves as a basis for other
+object systems like TclOO [Donal ???]. The scripting language <em>NX</em> and
+the <em>Next Scripting Framework</em> <a href="#Neumann and Sobernig 2009">[Neumann and Sobernig 2009]</a> extend
+the basic ideas of XOTcl by providing support for <em>language-oriented
+programming</em>. The the Next Scripting Framework supports multiple
+object systems concurrently. Effectively, every object system has
+different base classes for creating objects and classes. Therefore,
+these object systems can have different interfaces and can
+follow different naming conventions for built-in methods. Currently,
+the Next Scripting Framework is packaged with three object systems:
+NX, XOTcl 2.0, and TclCool (the language introduced by TIP#279).</p></div>
+<div class="imageblock" style="text-align:center;">
+<div class="content">
+<img src="languages.png" alt="Languages" width="500" />
+</div>
+<div class="title">Figure 1. Language History of the Next Scripting Language</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>The primary purpose of this document is to introduce NX to beginners.
+We expect some prior knowledge of programming languages, and some
+knowledge about Tcl. In the following sections we introduce NX by
+examples. In later sections we introduce the more advanced concepts of
+the language. Conceptually, most of the addressed concepts are very
+similar to XOTcl. Concerning the differences between NX and XOTcl,
+please refer to the <em>Migration Guide for the Next Scripting Language</em>.</p></div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_introductory_overview_example_stack">2. Introductory Overview Example: Stack</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>A classical programming example is the implementation of a stack, which
+is most likely familiar to many readers from many introductory
+programming courses. A stack is a last-in first-out data structure
+which is manipulated via operations like <code>push</code> (add something to the
+stack) and <code>pop</code> remove an entry from the stack. These operations are
+called <em>methods</em> in the context of object oriented programming
+systems. Primary goals of object orientation are encapsulation and
+abstraction. Therefore, we define a common unit (a class) that defines
+and encapsulates the behavior of a stack and provides methods to a user
+of the data structure that abstract from the actual implementation.</p></div>
+<div class="sect2">
+<h3 id="_define_a_class_stack">2.1. Define a Class "Stack"</h3>
+<div class="paragraph"><p>In our first example, we define a class named <code>Stack</code> with the methods
+<code>push</code> and <code>pop</code>. When an instance of the stack is created (e.g. a
+concrete stack <code>s1</code>) the stack will contain an instance variable named
+<code>things</code>, initialized with the an empty list.</p></div>
+<div class="paragraph" id="xmp-class-stack"><div class="title">Listing 2: Class Stack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Stack of Things
+</span> <span class='nx-comment'>#
+</span>
+ <span class='nx-keyword'>:variable</span> things {}
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
+ }
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
+ <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p>Typically, classes are defined in NX via <code>nx::Class create</code>, followed
+by the name of the new class (here: <code>Stack</code>). The definition of the
+stack placed between curly braces and contains here just the method
+definitions. Methods of the class are defined via <code>:method</code> followed
+by the name of the method, an argument list and the body of the
+method, consisting of Tcl and NX statements.</p></div>
+<div class="paragraph"><p>When an instance of <code>Stack</code> is created, it will contain an instance
+variable named <code>things</code>. If several <code>Stack</code> instances are created,
+each of the instances will have their own (same-named but different)
+instance variable. The instance variable <code>things</code> is used in our
+example as a list for the internal representation of the stack. We
+define in a next step the methods to access and modify this list
+structure. A user of the stack using the provided methods does not
+have to have any knowledge about the name or the structure of the
+internal representation (the instance variable <code>things</code>).</p></div>
+<div class="paragraph"><p>The method <code>push</code> receives an argument <code>thing</code> which should be placed
+on the stack. Note that we do not have to specify the type of the
+element on the stack, so we can push strings as well as numbers or
+other kind of things. When an element is pushed, we add this element
+as the first element to the list <code>things</code>. We insert the element using
+the Tcl command <code>linsert</code> which receives the list as first element,
+the position where the element should be added as second and the new
+element as third argument. To access the value of the instance
+variable we use Tcl’s dollar operator followed by the name. The
+names of instance variables are preceded with a colon <code>:</code>. Since the
+name contains a non-plain character, Tcl requires us to put braces
+around the name. The command <code>linsert</code> and its arguments are placed
+between square brackets. This means that the function <code>linsert</code> is called and
+a new list is returned, where the new element is inserted at the first
+position (index 0) in the list <code>things</code>. The result of the <code>linsert</code>
+function is assigned again to the instance variable <code>things</code>, which is
+updated this way. Finally the method <code>push</code> returns the pushed thing
+using the <code>return</code> statement.</p></div>
+<div class="paragraph"><p>The method <code>pop</code> returns the most recently stacked element and removes
+it from the stack. Therefore, it takes the first element from the list
+(using the Tcl command <code>lindex</code>), assigns it to the method-scoped
+variable <code>top</code>, removes the element from the instance variable
+<code>things</code> (by using the Tcl command <code>lrange</code>) and returns the value
+popped element <code>top</code>.</p></div>
+<div class="paragraph"><p>This finishes our first implementation of the stack, more enhanced
+versions will follow. Note that the methods <code>push</code> and <code>pop</code> are
+defined as <code>public</code>; this means that these methods can be
+used from all other objects in the system. Therefore, these methods
+provide an interface to the stack implementation.</p></div>
+<div class="paragraph" id="xmp-using-stack"><div class="title">Listing 3: Using the Stack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#!/usr/bin/env tclsh
+</span><span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Stack of Things
+</span> <span class='nx-comment'>#
+</span> ....
+}
+
+Stack <span class='nx-keyword'>create</span> s1
+s1 push a
+s1 push b
+s1 push c
+<span class='nx-keyword'>puts</span> [s1 pop]
+<span class='nx-keyword'>puts</span> [s1 pop]
+s1 <span class='nx-keyword'>destroy</span></pre></div></div>
+<div class="paragraph"><p>Now we want to use the stack. The code snippet in <a href="#xmp-using-stack">Listing 3</a> shows how to use the class Stack in a script.
+Since NX is based on Tcl, the script will be called with the Tcl shell
+<code>tclsh</code>. In the Tcl shell we have to <code>require package nx</code> to use the
+Next Scripting Framework and NX. The next lines contain the definition
+of the stack as presented before. Of course, it is as well possible to
+make the definition of the stack an own package, such we could simple
+say <code>package require stack</code>, or to save the definition of a stack
+simply in a file and load it via <code>source</code>.</p></div>
+<div class="paragraph"><p>In line 12 we create an instance of the stack, namely the stack object
+<code>s1</code>. The object <code>s1</code> is an instance of <code>Stack</code> and has therefore
+access to its methods. The methods like <code>push</code> or <code>pop</code> can be invoked
+via a command starting with the object name followed by the
+method name. In lines 13-15 we push on the stack the values <code>a</code>, then
+<code>b</code>, and <code>c</code>. In line 16 we output the result of the <code>pop</code> method
+using the Tcl command <code>puts</code>. We will see on standard output the
+value+c+ (the last stacked item). The output of the line 17 is the
+value <code>b</code> (the previously stacked item). Finally, in line 18 we
+destroy the object. This is not necessary here, but shows the life
+cycle of an object. In some respects, <code>destroy</code> is the counterpart of
+<code>create</code> from line 12.</p></div>
+<div class="imageblock" id="fig-class-object" style="text-align:center;">
+<div class="content">
+<img src="object-class-appclass.png" alt="object-class-appclass.png" />
+</div>
+<div class="title">Figure 4. Class and Object Diagram</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p><a href="#fig-class-object">Figure 4</a> shows the actual class and
+object structure of the first <code>Stack</code> example. Note that the common
+root class is <code>nx::Object</code> that contains methods for all objects.
+Since classes are as well objects in NX, <code>nx::Class</code> is a
+specialization of <code>nx::Object</code>. <code>nx::Class</code> provides methods for
+creating objects, such as the method <code>create</code> which is used to create
+objects (and classes as well).</p></div>
+</div>
+<div class="sect2">
+<h3 id="_define_an_object_named_stack">2.2. Define an Object Named "stack"</h3>
+<div class="paragraph"><p>The definition of the stack in <a href="#xmp-class-stack">Listing 2</a>
+follows the traditional object oriented approach, found in
+practically every object oriented programming language: Define a class
+with some methods, create instances from this class, and use the
+methods defined in the class in the instances of the class.</p></div>
+<div class="paragraph"><p>In our next example, we introduce <em>generic objects</em> and <em>object
+specific methods</em>. With NX, we can define generic objects, which are
+instances of the most generic class <code>nx::Object</code> (sometimes called
+<em>common root class</em>). <code>nx::Object</code> is predefined and contains a
+minimal set of methods applicable to all NX objects. In this example,
+we define a generic object named <code>stack</code> and provide methods for this
+object. The methods defined above were methods provided by a class for
+objects. Now we define object specific methods, which are methods
+applicable only to the object for which they are defined.</p></div>
+<div class="paragraph" id="xmp-object-stack"><div class="title">Listing 5: Object stack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> stack {
+
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>variable</span> things {}
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> push {thing} {
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
+ }
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> pop {} {
+ <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p>The example in <a href="#xmp-object-stack">Listing 5</a> defines the
+object <code>stack</code> in a very similar way as the class <code>Stack</code>. But the
+following points are different.</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+First, we use <code>nx::Object</code> instead of <code>nx::Class</code> to denote
+ that we want to create a generic object, not a class.
+</p>
+</li>
+<li>
+<p>
+We use <code>:object variable</code> to define the variable <code>things</code> just for
+ this single instance (the object <code>stack</code>).
+</p>
+</li>
+<li>
+<p>
+The definition for the methods <code>push</code> and <code>pop</code> are the same as
+ before, but here we defined these with <code>object method</code>. Therefore,
+ these two methods <code>push</code> and <code>pop</code> are object-specific.
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>In order to use
+the stack, we can use directly the object <code>stack</code> in the same way as
+we have used the object <code>s1</code> in <a href="#xmp-using-stack">Listing 3</a>
+the class diagram for this the object <code>stack</code>.</p></div>
+<div class="imageblock" id="img-object-stack" style="text-align:center;">
+<div class="content">
+<img src="object-stack.png" alt="object-stack.png" />
+</div>
+<div class="title">Figure 6. Object stack</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>A reader might wonder when to use a class <code>Stack</code> or rather an object
+<code>stack</code>. A big difference is certainly that one can define easily
+multiple instances of a class, while the object is actually a
+single, tailored entity. The concept of the object <code>stack</code> is similar to a module,
+providing a certain functionality via a common interface, without
+providing the functionality to create multiple instances. The reuse of
+methods provided by the class to objects is as well a difference. If
+the methods of the class are updated, all instances of the class will
+immediately get the modified behavior. However, this does not mean that
+the reuse for the methods of <code>stack</code> is not possible. NX allows for
+example to copy objects (similar to prototype based languages) or to
+reuse methods via e.g. aliases (more about this later).</p></div>
+<div class="paragraph"><p>Note that we use capitalized names for classes and lowercase names for
+instances. This is not required and a pure convention making it easier
+to understand scripts without much analysis.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_implementing_features_using_mixin_classes">2.3. Implementing Features using Mixin Classes</h3>
+<div class="paragraph"><p>So far, the definition of the stack methods was pretty minimal.
+Suppose, we want to define "safe stacks" that protect e.g. against
+stack under-runs (a stack under-run happens, when more <code>pop</code> than
+<code>push</code> operations are issued on a stack). Safety checking can be
+implemented mostly independent from the implementation details of the
+stack (usage of internal data structures). There are as well different
+ways of checking the safety. Therefore we say that safety checking is
+orthogonal to the stack core implementation.</p></div>
+<div class="paragraph"><p>With NX we can define stack-safety as a separate class using methods
+with the same names as the implementations before, and "mix" this
+behavior into classes or objects. The implementation of <code>Safety</code> in
+stack under-runs and to issue error messages, when this happens.</p></div>
+<div class="paragraph" id="xmp-class-safety"><div class="title">Listing 7: Class Safety</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Safety {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Implement stack safety by defining an additional
+</span> <span class='nx-comment'># instance variable named "count" that keeps track of
+</span> <span class='nx-comment'># the number of stacked elements. The methods of
+</span> <span class='nx-comment'># this class have the same names and argument lists
+</span> <span class='nx-comment'># as the methods of Stack; these methods "shadow"
+</span> <span class='nx-comment'># the methods of class Stack.
+</span> <span class='nx-comment'>#
+</span>
+ <span class='nx-keyword'>:variable</span> count 0
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
+ <span class='nx-keyword'>incr</span> :count
+ <span class='nx-keyword'>next</span>
+ }
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
+ <span class='nx-keyword'>if</span> {<span class='nx-variable'>${</span><span class='nx-variable'>:count}</span> == 0} { <span class='nx-keyword'>error</span> <span class='nx-string'>"Stack empty!"</span> }
+ <span class='nx-keyword'>incr</span> :count -1
+ <span class='nx-keyword'>next</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p>Note that all the methods of the class <code>Safety</code> end with <code>next</code>.
+This command is a primitive command of NX, which calls the
+same-named method with the same argument list as the current
+invocation.</p></div>
+<div class="paragraph"><p>Assume we save the definition of the class <code>Stack</code> in a file named
+<code>Stack.tcl</code> and the definition of the class <code>Safety</code> in a file named
+<code>Safety.tcl</code> in the current directory. When we load the classes
+<code>Stack</code> and <code>Safety</code> into the same script (see the terminal dialog in
+e.g. a certain stack <code>s2</code> as a safe stack, while all other stacks
+(such as <code>s1</code>) might be still "unsafe". This can be achieved via the
+option <code>-mixin</code> at the object creation time (see line 9 in
+option <code>-mixin</code> mixes the class <code>Safety</code> into the new instance <code>s2</code>.</p></div>
+<div class="paragraph" id="xmp-using-class-safety"><div class="title">Listing 8: Using the Class Safety</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>% <span class='nx-keyword'>package</span> <span class='nx-keyword'>require</span> nx
+2.0
+% <span class='nx-keyword'>source</span> Stack.tcl
+::Stack
+% <span class='nx-keyword'>source</span> Safety.tcl
+::Safety
+% Stack <span class='nx-keyword'>create</span> s1
+::s1
+% Stack <span class='nx-keyword'>create</span> s2 -object-mixin Safety
+::s2
+% s2 push a
+% s2 pop
+a
+% s2 pop
+Stack empty!
+
+% s1 <span class='nx-keyword'>info</span> precedence
+::Stack ::nx::Object
+
+% s2 <span class='nx-keyword'>info</span> precedence
+::Safety ::Stack ::nx::Object</pre></div></div>
+<div class="paragraph"><p>When the method <code>push</code> of <code>s2</code> is called, first the method of the
+mixin class <code>Safety</code> will be invoked that increments the counter and
+continues with <code>next</code> to call the shadowed method, here the method
+<code>push</code> of the <code>Stack</code> implementation that actually pushes the item.
+The same happens, when <code>s2 pop</code> is invoked, first the method of
+<code>Safety</code> is called, then the method of the <code>Stack</code>. When the stack is
+empty (the value of <code>count</code> reaches 0), and <code>pop</code> is invoked, the
+mixin class <code>Safety</code> generates an error message (raises an exception),
+and does not invoke the method of the <code>Stack</code>.</p></div>
+<div class="paragraph"><p>The last two commands in
+<a href="#xmp-using-class-safety">Listing 8</a>
+use introspection to query for the objects
+<code>s1</code> and <code>s2</code> in which order the involved classes are processed. This
+order is called the <code>precedence order</code> and is obtained via <code>info
+precedence</code>. We see that the mixin class <code>Safety</code> is only in use for
+<code>s2</code>, and takes there precedence over <code>Stack</code>. The common root class
+<code>nx::Object</code> is for both <code>s1</code> and <code>s2</code> the base class.</p></div>
+<div class="imageblock" id="img-per-object-mixin" style="text-align:center;">
+<div class="content">
+<img src="per-object-mixin.png" alt="per-object-mixin.png" />
+</div>
+<div class="title">Figure 9. Per-object Mixin</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>Note that in <a href="#xmp-using-class-safety">Listing 8</a>,
+the class <code>Safety</code> is only mixed into a single object (here
+<code>s2</code>), therefore we refer to this case as a <em>per-object mixin</em>.
+<a href="#img-per-object-mixin">Figure 9</a> shows the class
+diagram, where the class <code>Safety</code> is used as a per-object mixin for
+<code>s2</code>.</p></div>
+<div class="paragraph"><p>The mixin class <code>Safety</code> can be used as well in other ways, such as e.g. for
+defining classes of safe stacks:</p></div>
+<div class="paragraph" id="xmp-class-safestack"><div class="title">Listing 10: Class SafeStack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Create a safe stack class by using Stack and mixin
+</span><span class='nx-comment'># Safety
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> SafeStack -superclasses Stack -mixins Safety
+
+SafeStack <span class='nx-keyword'>create</span> s3</pre></div></div>
+<div class="paragraph"><p>The difference of a per-class mixin and a per-object mixin is that
+the per-class mixin is applicable to all instances of the
+class. Therefore, we call these mixins also sometimes instance mixins.
+In our example in <a href="#xmp-class-safestack">Listing 10</a>,
+<code>Safety</code> is mixed into the definition of
+<code>SafeStack</code>. Therefore, all instances of the class <code>SafeStack</code> (here
+the instance <code>s3</code>) will be using the safety definitions.</p></div>
+<div class="imageblock" id="img-per-class-mixin" style="text-align:center;">
+<div class="content">
+<img src="per-class-mixin.png" alt="per-class-mixin.png" />
+</div>
+<div class="title">Figure 11. Per-class Mixin</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p><a href="#img-per-class-mixin">Figure 11</a> shows the class diagram
+for this definition.
+Note that we could use <code>Safety</code> as well as a per-class mixin on
+<code>Stack</code>. In this case, all stacks would be safe stacks and we could
+not provide a selective feature selection (which might be perfectly
+fine).</p></div>
+</div>
+<div class="sect2">
+<h3 id="_define_different_kinds_of_stacks">2.4. Define Different Kinds of Stacks</h3>
+<div class="paragraph"><p>The definition of <code>Stack</code> is generic and allows all kind of elements
+to be stacked. Suppose, we want to use the generic stack definition,
+but a certain stack (say, stack <code>s4</code>) should be a stack for integers
+only. This behavior can be achieved by the same means as introduced
+already in <a href="#xmp-object-stack">Listing 5</a>, namely
+object-specific methods.</p></div>
+<div class="paragraph" id="xmp-object-integer-stack"><div class="title">Listing 12: Object Integer Stack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>Stack <span class='nx-keyword'>create</span> s4 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Create a stack with a object-specific method
+</span> <span class='nx-comment'># to check the type of entries
+</span> <span class='nx-comment'>#
+</span>
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> push {thing:integer} {
+ <span class='nx-keyword'>next</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p>The program snippet in <a href="#xmp-object-integer-stack">Listing 12</a> defines an instance <code>s4</code> of the class
+<code>Stack</code> and provides an object specific method for <code>push</code> to implement
+an integer stack. The method <code>pull</code> is the same for the integer stack
+as for all other stacks, so it will be reused as usual from the class
+<code>Stack</code>. The object-specific method <code>push</code> of <code>s4</code> has a value
+constraint in its argument list (<code>thing:integer</code>) that makes sure
+that only integers can be stacked. In case the argument is not an
+integer, an exception will be raised. Of course, one could perform the
+value constraint checking as well in the body of the method <code>proc</code> by
+accepting an generic argument and by performing the test for the value
+in the body of the method. In the case, the passed value is an
+integer, the <code>push</code> method of <a href="#xmp-object-integer-stack">Listing 12</a> calls <code>next</code>, and therefore calls the
+shadowed generic definition of <code>push</code> as provided by <code>Stack</code>.</p></div>
+<div class="paragraph" id="xmp-class-integer-stack"><div class="title">Listing 13: Class IntegerStack</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> IntegerStack -superclass Stack {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Create a Stack accepting only integers
+</span> <span class='nx-comment'>#
+</span>
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing:integer} {
+ <span class='nx-keyword'>next</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p>An alternative approach is shown in
+<a href="#xmp-class-integer-stack">Listing 13</a>, where the class
+<code>IntegerStack</code> is defined, using the same method definition
+as <code>s4</code>, this time on the class level.</p></div>
+</div>
+<div class="sect2">
+<h3 id="_define_object_specific_methods_on_classes">2.5. Define Object Specific Methods on Classes</h3>
+<div class="paragraph"><p>In our previous examples we defined methods provided by classes
+(applicable for their instances) and object-specific methods (methods
+defined on objects, which are only applicable for these objects). In
+this section, we introduce methods that are defined on the class
+objects. Such methods are sometimes called <em>class methods</em> or
+<em>static methods</em>.</p></div>
+<div class="paragraph"><p>In NX classes are objects, they are specialized objects with
+additional methods. Methods for classes are often used for managing
+the life-cycles of the instances of the classes (we will come to this
+point in later sections in more detail). Since classes are objects, we
+can use exactly the same notation as above to define class methods by
+using <code>object method</code>. The methods defined on the class object are
+in all respects identical with object specific methods shown in the
+examples above.</p></div>
+<div class="paragraph" id="xmp-stack2"><div class="title">Listing 14: Class Stack2</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Stack2 {
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> available_stacks {} {
+ <span class='nx-keyword'>return</span> [<span class='nx-keyword'>llength</span> [<span class='nx-keyword'>:info</span> instances]]
+ }
+
+ <span class='nx-keyword'>:variable</span> things {}
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> push {thing} {
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>linsert</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0 <span class='nx-variable'>$thing</span>]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$thing</span>
+ }
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> pop {} {
+ <span class='nx-keyword'>set</span> top [<span class='nx-keyword'>lindex</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 0]
+ <span class='nx-keyword'>set</span> :things [<span class='nx-keyword'>lrange</span> <span class='nx-variable'>${</span><span class='nx-variable'>:things}</span> 1 end]
+ <span class='nx-keyword'>return</span> <span class='nx-variable'>$top</span>
+ }
+}
+
+Stack2 <span class='nx-keyword'>create</span> s1
+Stack2 <span class='nx-keyword'>create</span> s2
+
+<span class='nx-keyword'>puts</span> [Stack2 available_stacks]</pre></div></div>
+<div class="paragraph"><p>The class <code>Stack2</code> in <a href="#xmp-stack2">Listing 14</a> consists of the
+earlier definition of the class <code>Stack</code> and is extended by the
+class-specific method <code>available_stacks</code>, which returns the
+current number of instances of the stack. The final command <code>puts</code>
+(line 26) prints 2 to the console.</p></div>
+<div class="imageblock" id="img-stack2" style="text-align:center;">
+<div class="content">
+<img src="stack2.png" alt="stack2.png" />
+</div>
+<div class="title">Figure 15. Stack2</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>The class diagram in <a href="#img-stack2">Figure 15</a> shows the
+diagrammatic representation of the class object-specific method
+<code>available_stacks</code>. Since every class is a specialization of the
+common root class <code>nx::Object</code>, the common root class is often omitted
+from the class diagrams, so it was omitted here as well in the diagram.</p></div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_basic_language_features_of_nx">3. Basic Language Features of NX</h2>
+<div class="sectionbody">
+<div class="sect2">
+<h3 id="_variables_and_properties">3.1. Variables and Properties</h3>
+<div class="paragraph"><p>In general, NX does not need variable declarations. It allows one to
+create or modify variables on the fly by using for example the Tcl
+commands <code>set</code> and <code>unset</code>. Depending on the variable name (or more
+precisely, depending on the variable name’s prefix consisting of
+colons "<code>:</code>") a variable is either local to a method, or it is an
+instance variable, or a global variable. The rules are:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+A variable without any colon prefix refers typically to a method
+ scoped variable. Such a variable is created during the invocation
+ of the method, and it is deleted, when the method ends. In the
+ example below, the variable <code>a</code> is method scoped.
+</p>
+</li>
+<li>
+<p>
+A variable with a single colon prefix refers to an instance
+ variable. An instance variable is part of the object; when the
+ object is destroyed, its instance variables are deleted as well. In the
+ example below, the variable <code>b</code> is an instance variable.
+</p>
+</li>
+<li>
+<p>
+A variable with two leading colons refers to a global variable. The
+ lifespan of a globale variable ends when the variable is explicitly
+ unset or the script terminates. Variables, which are placed in Tcl
+ namespaces, are also global variables. In the example below, the
+ variable <code>c</code> is a global variable.
+</p>
+</li>
+</ul></div>
+<div class="paragraph" id="xmp-var-resolver"><div class="title">Listing 16: Scopes of Variables</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo {
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo args {...}
+ <span class='nx-comment'># "a" is a method scoped variable
+</span> <span class='nx-keyword'>set</span> a 1
+ <span class='nx-comment'># "b" is an Instance variable
+</span> <span class='nx-keyword'>set</span> :b 2
+ <span class='nx-comment'># "c" is a global variable/namespaced variable
+</span> <span class='nx-keyword'>set</span> ::c 3
+ }
+}</pre></div></div>
+<div class="paragraph"><p><a href="#xmp-var-resolver">Listing 16</a> shows a method <code>foo</code>
+of some class <code>Foo</code> referring to differently scoped variables.</p></div>
+<div class="sect3">
+<h4 id="_properties_configurable_instance_variables">3.1.1. Properties: Configurable Instance Variables</h4>
+<div class="paragraph"><p>As described above, there is no need to declare instance variables in
+NX. In many cases, a developer might want to define some value
+constraints for variables, or to provide defaults, or to make
+variables configurable upon object creation. Often, variables are
+"inherited", meaning that the variables declared in a general class
+are also available in a more specialized class. For these purposes NX
+provides <em>variable handlers</em> responsible for the management of
+instance variables. We distinguish in NX between configurable
+variables (called <code>property</code>) and variables that are not configurable
+(called <code>variable</code>).</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>A <strong>property</strong> is a definition of a configurable instance variable.</p></div>
+</div></div>
+<div class="paragraph"><p>The term configurable means that (a) one can provide at creation time of
+an instance a value for this variable, and (b), one can query the
+value via the accessor function <code>cget</code> and (c), one can change the
+value of the variable via <code>configure</code> at runtime. Since the general
+accessor function <code>cget</code> and <code>configure</code> are available, an application
+developer does not have to program own accessor methods. When value
+checkers are provided, each time, the value of the variable is to be
+changed, the constrained are checked as well.</p></div>
+<div class="imageblock" id="img-person-student" style="text-align:center;">
+<div class="content">
+<img src="person-student.png" alt="person-student.png" />
+</div>
+<div class="title">Figure 17. Classes Person and Student</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>The class diagram above defines the classes <code>Person</code> and
+<code>Student</code>. For both classes, configurable instance variable are
+specified by defining these as properties. The listing below shows
+an implementation of this conceptual model in NX.</p></div>
+<div class="paragraph" id="xmp-properties"><div class="title">Listing 18: Properties</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Define a class Person with properties "name"
+</span><span class='nx-comment'># and "birthday"
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person {
+ <span class='nx-keyword'>:property</span> name:required
+ <span class='nx-keyword'>:property</span> birthday
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Define a class Student as specialization of Person
+</span><span class='nx-comment'># with additional properties
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Student -superclass Person {
+ <span class='nx-keyword'>:property</span> matnr:required
+ <span class='nx-keyword'>:property</span> {oncampus:boolean true}
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Create instances using configure parameters
+</span><span class='nx-comment'># for the initialization
+</span><span class='nx-comment'>#
+</span>Person <span class='nx-keyword'>create</span> p1 -name Bob
+Student <span class='nx-keyword'>create</span> s1 -name Susan -matnr 4711
+
+<span class='nx-comment'># Access property value via accessor method
+</span><span class='nx-keyword'>puts</span> <span class='nx-string'>"The name of s1 is [s1 cget -name]"</span></pre></div></div>
+<div class="paragraph"><p>By defining <code>name</code> and <code>birthday</code> as properties of <code>Person</code>, NX makes
+these configurable. When we create an instance of <code>Person</code> named
+<code>p1</code>, we can provide a value for e.g. the name by specifying <code>-name</code>
+during creation. The properties result in non-positional configure parameters
+which can be provided in any order. In our listing, we create an instance of
+<code>Person</code> using the configure parameter <code>name</code> and provide the value of
+<code>Bob</code> to the instance variable <code>name</code>.</p></div>
+<div class="paragraph"><p>The class <code>Student</code> is defined as a specialization of <code>Person</code> with
+two additional properties: <code>matnr</code> and <code>oncampus</code>. The property
+<code>matnr</code> is required (it has to be provided, when an instance of this
+class is created), and the property <code>oncampus</code> is boolean, and is per
+default set to <code>true</code>. Note that the class <code>Student</code> inherits the
+properties of <code>Person</code>. So, <code>Student</code> has four properties in total.</p></div>
+<div class="paragraph"><p>The property definitions provide the <code>configure parameters</code> for
+instance creation. Many other languages require such parameters to be
+passed via arguments of a constructor, which is often error prone,
+when values are to be passed to superclasses. Also in dynamic
+languages, the relationships between classes can be easily changed,
+and different superclasses might have different requirements in their
+constructors. The declarative approach in NX reduces the need for
+tailored constructor methods significantly.</p></div>
+<div class="paragraph"><p>Note that the property <code>matnr</code> of class <code>Student</code> is required. This
+means, that if we try to create an instance of <code>Student</code>, a runtime
+exception will be triggered. The property <code>oncamups</code> is boolean and
+contains a default value. Providing a default value means that
+whenever we create an instance of this class the object will contain
+such an instance variable, even when we provide no value via the
+configure parameters.</p></div>
+<div class="paragraph"><p>In our listing, we create an instance of <code>Student</code> using the two
+configure parameters <code>name</code> and <code>matnr</code>. Finally, we use method <code>cget</code>
+to obtain the value of the instance variable <code>name</code> of object <code>s1</code>.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_non_configurable_instance_variables">3.1.2. Non-configurable Instance Variables</h4>
+<div class="paragraph"><p>In practice, not all instance variables should be configurable. But
+still, we want to be able to provide defaults similar to
+properties. To define non-configurable instance variables the
+predefined method <code>variable</code> can be used. Such instance variables are
+often used for e.g. keeping the internal state of an object. The
+usage of <code>variable</code> is in many respects similar to <code>property</code>. One
+difference is, that <code>property</code> uses the same syntax as for method
+parameters, whereas <code>variable</code> receives the default value as a
+separate argument (similar to the <code>variable</code> command in plain
+Tcl). The introductory Stack example in <a href="#xmp-class-stack">Listing 2</a> uses already the method <code>variable</code>.</p></div>
+<div class="paragraph" id="xmp-variable"><div class="title">Listing 19: Declaring Variables</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
+ <span class='nx-keyword'>:variable</span> x 1
+ <span class='nx-comment'># ...
+</span>}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Derived -superclass Base {
+ <span class='nx-keyword'>:variable</span> y 2
+ <span class='nx-comment'># ...
+</span>}
+
+<span class='nx-comment'># Create instance of the class Derived
+</span>Derived <span class='nx-keyword'>create</span> d1
+
+<span class='nx-comment'># Object d1 has instance variables
+</span><span class='nx-comment'># x == 1 and y == 2</span></pre></div></div>
+<div class="paragraph"><p>Note that the variable definitions are inherited in the same way as
+properties. The example in <a href="#xmp-variable">Listing 19</a> shows a
+class <code>Derived</code> that inherits from <code>Base</code>. When an instance <code>d1</code> is
+created, it will contain the two instance variables <code>x</code> and <code>y</code>.
+Note that the variable declarations from <code>property</code> and <code>variable</code> are
+used to initialize (and to configure) the instances variables of an object.</p></div>
+<div class="paragraph" id="xmp-constructor"><div class="title">Listing 20: Setting Variables in the Constructor</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base2 {
+ <span class='nx-comment'># ...
+</span> <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
+ <span class='nx-keyword'>set</span> :x 1
+ <span class='nx-comment'># ....
+</span> }
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Derived2 -superclass Base2 {
+ <span class='nx-comment'># ...
+</span> <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
+ <span class='nx-keyword'>set</span> :y 2
+ <span class='nx-keyword'>next</span>
+ <span class='nx-comment'># ....
+</span> }
+}
+
+<span class='nx-comment'># Create instance of the class Derived2
+</span>Derived2 <span class='nx-keyword'>create</span> d2</pre></div></div>
+<div class="paragraph"><p>In many other object oriented languages, the instance variables are
+initialized solely by the constructor (similar to class <code>Derived2</code> in
+<a href="#xmp-constructor">Listing 20</a>). This approach is certainly
+also possible in NX. Note that the approach using constructors
+requires an explicit method chaining between the constructors and is
+less declarative than the approach in NX using <code>property</code> and <code>variable</code>.</p></div>
+<div class="paragraph"><p>Both, <code>property</code> and <code>variable</code> provide much more functionalities. One
+can for example declare <code>public</code>, <code>protected</code> or <code>private</code> accessor
+methods, or one can define variables to be incremental (for
+e.g. adding values to a list of values), or one can define variables
+specific behavior.</p></div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_method_definitions">3.2. Method Definitions</h3>
+<div class="paragraph"><p>The basic building blocks of an object oriented program are object and
+classes, which contain named pieces of code, the methods.</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p><strong>Methods</strong> are subroutines (pieces of code) associated with objects
+and/or classes. A method has a name, receives optionally arguments
+during invocation and returns a value.</p></div>
+</div></div>
+<div class="paragraph"><p>Plain Tcl provides subroutines, which are not associated with objects
+or classes. Tcl distinguishes between +proc+s (scripted subroutines)
+and commands (system-languages implemented subroutines).</p></div>
+<div class="paragraph"><p>Methods might have different scopes, defining, on which kind of
+objects these methods are applicable to. These are described in more
+detail later on. For the time being, we deal here with methods defined
+on classes, which are applicable for the instance of these classes.</p></div>
+<div class="sect3">
+<h4 id="_scripted_methods">3.2.1. Scripted Methods</h4>
+<div class="paragraph"><p>Since NX is a scripting language, most methods are most likely
+scripted methods, in which the method body contains Tcl code.</p></div>
+<div class="paragraph" id="xmp-fido1"><div class="title">Listing 21: Scripted method</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Define a class
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
+
+ <span class='nx-comment'># Define a scripted method for the class
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span>
+ }
+}
+
+<span class='nx-comment'># Create an instance of the class
+</span>Dog <span class='nx-keyword'>create</span> fido
+
+<span class='nx-comment'># The following line prints "::fido Bark, bark, bark."
+</span>fido bark</pre></div></div>
+<div class="paragraph"><p>In the example above we create a class <code>Dog</code> with a scripted method
+named <code>bark</code>. The method body defines the code, which is executed when
+the method is invoked. In this example, the method <code>bar</code> prints out a
+line on the terminal starting with the object name (this is determined
+by the built in command <code>self</code>) followed by "Bark, bark, bark.". This
+method is defined on a class and applicable to instances of the class
+(here the instance <code>fido</code>).</p></div>
+</div>
+<div class="sect3">
+<h4 id="_c_implemented_methods">3.2.2. C-implemented Methods</h4>
+<div class="paragraph"><p>Not all of the methods usable in NX are scripted methods; many
+predefined methods are defined in the underlying system language,
+which is typically C. For example, in <a href="#xmp-fido1">Listing 21</a> we
+used the method <code>create</code> to create the class <code>Dog</code> and to create the
+dog instance <code>fido</code>. These methods are implemented in C in the next
+scripting framework.</p></div>
+<div class="paragraph"><p>C-implemented methods are not only provided by the underlying
+framework but might be as well defined by application developers. This
+is an advanced topic, not covered here. However, application developer
+might reuse some generic C code to define their own C-implemented
+methods. Such methods are for example <em>accessors</em>, <em>forwarders</em> and
+<em>aliases</em>.</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>An <strong>accessor method</strong> is a method that accesses instance
+variables of an object. A call to an accessor
+without arguments uses the accessor as a getter, obtaining the actual
+value of the associated variable. A call to an accessor with an
+argument uses it as a setter, setting the value of the associated
+variable.</p></div>
+</div></div>
+<div class="paragraph"><p>NX provides support for C-implemented accessor methods. Accessors have
+already been mentioned in the section about properties. When
+the option <code>-accessor public|protected|private</code> is provided to a
+<code>variable</code> or <code>property</code> definition, NX creates automatically a
+same-named accessors method.</p></div>
+<div class="paragraph" id="xmp-fido2"><div class="title">Listing 22: Accessor Methods</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
+ <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} { Tail <span class='nx-keyword'>create</span> [<span class='nx-keyword'>self</span>]::tail}
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Tail {
+ <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {length:double 5}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> wag {} {<span class='nx-keyword'>return</span> Joy}
+}
+
+<span class='nx-comment'># Create an instance of the class
+</span>Dog <span class='nx-keyword'>create</span> fido
+
+<span class='nx-comment'># Use the accessor "length" as a getter, to obtain the value
+</span><span class='nx-comment'># of a property. The following call returns the length of the
+</span><span class='nx-comment'># tail of fido
+</span>fido::tail length get
+
+<span class='nx-comment'># Use the accessor "length" as a setter, to alter the value
+</span><span class='nx-comment'># of a property. The following call changes the length of
+</span><span class='nx-comment'># the tail of fido
+</span>fido::tail length <span class='nx-keyword'>set</span> 10
+
+<span class='nx-comment'># Proving an invalid values will raise an error
+</span>fido::tail length <span class='nx-keyword'>set</span> <span class='nx-string'>"Hello"</span></pre></div></div>
+<div class="paragraph"><p><a href="#xmp-fido2">Listing 22</a> shows an extended example, where every dog
+has a tail. The object <code>tail</code> is created as a subobject of the dog in
+the constructor <code>init</code>. The subobject can be accessed by providing the
+full name of the subobject <code>fido::tail</code>. The method <code>length</code> is an
+C-implemented accessor, that enforces the value constraint (here a
+floating point number, since length uses the value constraint
+<code>double</code>). Line 25 will therefore raise an exception, since the
+provided values cannot be converted to a double number.</p></div>
+<div class="paragraph" id="xmp-fido3"><div class="title">Listing 23: Forwarder Methods</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
+ <span class='nx-keyword'>:method</span> <span class='nx-keyword'>init</span> {} {
+ Tail <span class='nx-keyword'>create</span> [<span class='nx-keyword'>self</span>]::tail
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>forward</span> wag [<span class='nx-keyword'>self</span>]::tail wag
+ }
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Tail {
+ <span class='nx-keyword'>:property</span> {length 5}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> wag {} {<span class='nx-keyword'>return</span> Joy}
+}
+
+<span class='nx-comment'># Create an instance of the class
+</span>Dog <span class='nx-keyword'>create</span> fido
+
+<span class='nx-comment'># The invocation of "fido wag" is delegated to "fido::tail wag".
+</span><span class='nx-comment'># Therefore, the following method returns "Joy".
+</span>fido wag</pre></div></div>
+<div class="paragraph"><p><a href="#xmp-fido3">Listing 23</a> again extends the example by adding a
+forwarder named <code>wag</code> to the object (e.g. <code>fido</code>). The forwarder
+redirects all calls of the form <code>fido wag</code> with arbitrary arguments to
+the subobject <code>fido::tail</code>.</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>A <strong>forwarder method</strong> is a
+C-implemented method that redirects an invocation for a certain method
+to either a method of another object or to some other method of the
+same object. Forwarding an invocation of a method to some other
+object is a means of delegation.</p></div>
+</div></div>
+<div class="paragraph"><p>The functionality of the forwarder can just as well be implemented as
+a scripted method, but for the most common cases, the forward
+implementation is more efficient, and the <code>forward</code> method expresses
+the intention of the developer.</p></div>
+<div class="paragraph"><p>The method <code>forwarder</code> has several options to change e.g. the order of
+the arguments, or to substitute certain patterns in the argument list
+etc. This will be described in later sections.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_method_aliases">3.2.3. Method-Aliases</h4>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>An <strong>alias method</strong> is a means to register either an existing method,
+or a Tcl proc, or a Tcl command as a method with the provided
+name on a class or object.</p></div>
+</div></div>
+<div class="paragraph"><p>In some way, the method alias is a restricted form of a forwarder,
+though it does not support delegation to different objects or argument
+reordering. The advantage of the method alias compared to a forwarder
+is that it has close to zero overhead, especially for aliasing
+c-implemented methods.</p></div>
+<div class="paragraph" id="xmp-fido4"><div class="title">Listing 24: Method-Alias</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Dog {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bark {} { <span class='nx-keyword'>puts</span> <span class='nx-string'>"[self] Bark, bark, bark."</span> }
+
+ <span class='nx-comment'># Define a public alias for the method "bark"
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>alias</span> warn [<span class='nx-keyword'>:info</span> <span class='nx-keyword'>method</span> handle bark]
+ <span class='nx-comment'># ...
+</span>}
+
+<span class='nx-comment'># Create an instance of the class
+</span>Dog <span class='nx-keyword'>create</span> fido
+
+<span class='nx-comment'># The following line prints "::fido Bark, bark, bark."
+</span>fido warn</pre></div></div>
+<div class="paragraph"><p><a href="#xmp-fido4">Listing 24</a> extends the last example by defining an
+alias for the method <code>bark</code>. The example only shows the bare
+mechanism. In general, method aliases are very powerful means for
+reusing pre-existing functionality. The full object system of NX and
+XOTcl2 is built from aliases, reusing functionality provided by the
+next scripting framework under different names. Method aliases
+are as well a means for implementing traits in NX.</p></div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_method_protection">3.3. Method Protection</h3>
+<div class="paragraph"><p>All kinds of methods might have different kind of protections in NX.
+The call-protection defines from which calling context methods might
+be called. The Next Scripting Framework supports as well redefinition
+protection for methods.</p></div>
+<div class="paragraph"><p>NX distinguishes between <code>public</code>, <code>protected</code> and <code>private</code> methods,
+where the default call-protection is <code>protected</code>.</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>A <strong>public</strong> method can be called from every context. A <strong>protected</strong>
+method can only be invoked from the same object. A <strong>private</strong> method
+can only be invoked from methods defined on the same entity
+(defined on the same class or on the same object) via the invocation
+with the local flag (i.e. "<code>: -local foo</code>").</p></div>
+</div></div>
+<div class="paragraph"><p>All kind of method protections are applicable for all kind of methods,
+either scripted or C-implemented.</p></div>
+<div class="paragraph"><p>The distinction between public and protected leads to interfaces for
+classes and objects. Public methods are intended for consumers of
+these entities. Public methods define the intended ways of providing
+methods for external usages (usages, from other objects or
+classes). Protected methods are intended for the implementor of the
+class or subclasses and not for public usage. The distinction between
+protected and public reduces the coupling between consumers and the
+implementation, and offers more flexibility to the developer.</p></div>
+<div class="paragraph" id="xmp-protected-method"><div class="title">Listing 25: Protected Methods</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Foo {
+
+ <span class='nx-comment'># Define a public method
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
+ <span class='nx-comment'># ....
+</span> <span class='nx-keyword'>return</span> [:helper]
+ }
+
+ <span class='nx-comment'># Define a protected method
+</span> <span class='nx-keyword'>:method</span> helper {} {
+ <span class='nx-keyword'>return</span> 1
+ }
+}
+
+<span class='nx-comment'># Create an instance of the class:
+</span>Foo <span class='nx-keyword'>create</span> f1
+
+<span class='nx-comment'># The invocation of the public method "foo" returns 1
+</span>f1 foo
+
+<span class='nx-comment'># The invocation of the protected method "helper" raises an error:
+</span>f1 helper</pre></div></div>
+<div class="paragraph"><p>The example above uses <code>:protected method helper …</code>. We could have
+used here as well <code>:method helper …</code>, since the default method
+call-protection is already protected.</p></div>
+<div class="paragraph"><p>The method call-protection of <code>private</code> goes one step further and
+helps to hide implementation details also for implementors of
+subclasses. Private methods are a means for avoiding unanticipated name
+clashes. Consider the following example:</p></div>
+<div class="paragraph" id="xmp-private-method"><div class="title">Listing 26: Private Methods</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Base {
+ <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> helper {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> + <span class='nx-variable'>$b</span>}}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a b} {: -local helper <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Sub -superclass Base {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a b} {: -local helper <span class='nx-variable'>$a</span> <span class='nx-variable'>$b</span>}
+ <span class='nx-keyword'>:private</span> <span class='nx-keyword'>method</span> helper {a b} {<span class='nx-keyword'>expr</span> {<span class='nx-variable'>$a</span> * <span class='nx-variable'>$b</span>}}
+ <span class='nx-keyword'>:create</span> s1
+}
+
+s1 foo 3 4 ;<span class='nx-comment'># returns 7
+</span>s1 bar 3 4 ;<span class='nx-comment'># returns 12
+</span>s1 helper 3 4 ;<span class='nx-comment'># raises error: unable to dispatch method helper</span></pre></div></div>
+<div class="paragraph"><p>The base class implements a public method <code>foo</code> using the helper
+method named <code>helper</code>. The derived class implements a as well a public
+method <code>bar</code>, which is also using a helper method named <code>helper</code>. When
+an instance <code>s1</code> is created from the derived class, the method <code>foo</code>
+is invoked which uses in turn the private method of the base
+class. Therefore, the invocation <code>s1 foo 3 4</code> returns its sum. If
+the <code>local</code> flag had not beed used in helper, <code>s1</code> would
+have tried to call the helper of <code>Sub</code>, which would be incorrect. For
+all other purposes, the private methods are "invisible" in all
+situations, e.g., when mixins are used, or within the <code>next</code>-path, etc.</p></div>
+<div class="paragraph"><p>By using the <code>-local</code> flag at the call site it is possible to invoke
+only the local definition of the method. If we would call the method
+without this flag, the resolution order would be the standard
+resolution order, starting with filters, mixins, object methods
+and the full intrinsic class hierarchy.</p></div>
+<div class="paragraph"><p>NX supports the modifier <code>private</code> for methods and properties. In all
+cases <code>private</code> is an instrument to avoid unanticipated interactions
+and means actually "accessible for methods defined on the same entity
+(object or class)". The main usage for <code>private</code> is to improve
+locality of the code e.g. for compositional operations.</p></div>
+<div class="paragraph"><p>In order to improve locality for properties, a private property
+defines therefore internally a variable with a different name to avoid
+unintended interactions. The variable should be accessed via the
+private accessor, which can be invoked with the <code>-local</code> flag. In the
+following example class <code>D</code> introduces a private property with the
+same name as a property in the superclass.</p></div>
+<div class="paragraph" id="xmp-private-properties"><div class="title">Listing 27: Private Properties</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Define a class C with a property "x" and a public accessor
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>public</span> {x c}
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Define a subclass D with a private property "x"
+</span><span class='nx-comment'># and a method bar, which is capable of accessing
+</span><span class='nx-comment'># the private property.
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D -superclass C {
+ <span class='nx-keyword'>:property</span> -accessor <span class='nx-keyword'>private</span> {x d}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {p} {<span class='nx-keyword'>return</span> [: -local <span class='nx-variable'>$p</span> get]}
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># The private and public (or protected) properties
+</span><span class='nx-comment'># define internally separate variable that do not
+</span><span class='nx-comment'># conflict.
+</span><span class='nx-comment'>#
+</span>D <span class='nx-keyword'>create</span> d1
+<span class='nx-keyword'>puts</span> [d1 x get] ;<span class='nx-comment'># prints "c"
+</span><span class='nx-keyword'>puts</span> [d1 bar x] ;<span class='nx-comment'># prints "d"</span></pre></div></div>
+<div class="paragraph"><p>Without the <code>private</code> definition of the property, the definition of
+property <code>x</code> in class <code>D</code> would shadow the
+definition of the property in the superclass <code>C</code> for its instances
+(<code>d1 x</code> or <code>set :x</code> would return <code>d</code> instead of <code>c</code>).</p></div>
+</div>
+<div class="sect2">
+<h3 id="_applicability_of_methods">3.4. Applicability of Methods</h3>
+<div class="paragraph"><p>As defined above, a method is a subroutine defined on an object or
+class. This object (or class) contains the method. If the object (or
+class) is deleted, the contained methods will be deleted as well.</p></div>
+<div class="sect3">
+<h4 id="_instance_methods">3.4.1. Instance Methods</h4>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>Typically, methods are defined on a class, and the methods defined on the
+class are applicable to the instances (direct or indirect) of this
+class. These methods are called <strong>instance methods</strong>.</p></div>
+</div></div>
+<div class="paragraph"><p>In the following example method, <code>foo</code> is an instance method defined
+on class <code>C</code>.</p></div>
+<div class="paragraph" id="xmp-instance-applicable"><div class="title">Listing 28: Methods applicable for instances</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
+ <span class='nx-keyword'>:create</span> c1
+}
+
+<span class='nx-comment'># Method "foo" is defined on class "C"
+</span><span class='nx-comment'># and applicable to the instances of "C"
+</span>c1 foo</pre></div></div>
+<div class="paragraph"><p>There are many programming languages that only allow these types of methods.
+However, NX also allows methods to be defined on objects.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_object_methods">3.4.2. Object Methods</h4>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>Methods defined on objects are <strong>object methods</strong>. Object
+methods are only applicable on the object, on which they are defined.
+Object methods cannot be inherited from other objects.</p></div>
+</div></div>
+<div class="paragraph"><p>The following example defines an object method <code>bar</code> on the
+instance <code>c1</code> of class <code>C</code>, and as well as the object specific method
+<code>baz</code> defined on the object <code>o1</code>. An object method is defined
+via <code>object method</code>.</p></div>
+<div class="paragraph"><p>Note that we can define a object method that shadows (redefines)
+for this object methods provided from classes.</p></div>
+<div class="paragraph" id="xmp-object-applicable1"><div class="title">Listing 29: Object Method</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
+ <span class='nx-keyword'>:create</span> c1 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 2}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {<span class='nx-keyword'>return</span> 3}
+ }
+}
+
+<span class='nx-comment'># Method "bar" is an object specific method of "c1"
+</span>c1 bar
+
+<span class='nx-comment'># object-specific method "foo" returns 2
+</span>c1 foo
+
+<span class='nx-comment'># Method "baz" is an object specific method of "o1"
+</span><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o1 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {} {<span class='nx-keyword'>return</span> 4}
+}
+o1 baz</pre></div></div>
+</div>
+<div class="sect3">
+<h4 id="_class_methods">3.4.3. Class Methods</h4>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>A <strong>class method</strong> is a method defined on a class, which is only
+applicable to the class object itself. The class method is actually
+an object method of the class object.</p></div>
+</div></div>
+<div class="paragraph"><p>In NX, all classes are objects. Classes are in NX special kind of
+objects that have e.g. the ability to create instances and to provide
+methods for the instances. Classes manage their instances. The general
+method set for classes is defined on the meta-classes (more about
+this later).</p></div>
+<div class="paragraph"><p>The following example defines a public class method <code>bar</code> on class
+<code>C</code>. The class method is specified by using the modifier <code>object</code> in
+front of <code>method</code> in the method definition command.</p></div>
+<div class="paragraph" id="xmp-object-applicable2"><div class="title">Listing 30: Class Methods</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Define a class method "bar" and an instance
+</span> <span class='nx-comment'># method "foo"
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {<span class='nx-keyword'>return</span> 2}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {<span class='nx-keyword'>return</span> 1}
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Create an instance of the current class
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:create</span> c1
+}
+
+<span class='nx-comment'># Method "bar" is a class method of class "C"
+</span><span class='nx-comment'># therefore applicable on the class object "C"
+</span>C bar
+
+<span class='nx-comment'># Method "foo" is an instance method of "C"
+</span><span class='nx-comment'># therefore applicable on instance "c1"
+</span>c1 foo
+
+<span class='nx-comment'># When trying to invoke the class method on the
+</span><span class='nx-comment'># instance, an error will be raised.
+</span>c1 bar</pre></div></div>
+<div class="paragraph"><p>In some other object-oriented programming languages, class methods
+are called "static methods".</p></div>
+</div>
+</div>
+<div class="sect2">
+<h3 id="_ensemble_methods">3.5. Ensemble Methods</h3>
+<div class="paragraph"><p>NX provides <em>ensemble methods</em> as a means to structure the method name
+space and to group related methods. Ensemble methods are similar in
+concept to Tcl’s ensemble commands.</p></div>
+<div class="exampleblock">
+<div class="content">
+<div class="paragraph"><p>An <strong>ensemble method</strong> is a form of a hierarchical method consisting of
+a container method and sub-methods. The first argument of the
+container method is interpreted as a selector (the sub-method). Every
+sub-method can be an container method as well.</p></div>
+</div></div>
+<div class="paragraph"><p>Ensemble methods provide a means to group related commands together,
+and they are extensible in various ways. It is possible to add
+sub-methods at any time to existing ensembles. Furthermore, it is
+possible to extend ensemble methods via mixin classes.</p></div>
+<div class="paragraph"><p>The following example defines an ensemble method for <code>string</code>. An
+ensemble method is defined when the provide method name contains a
+space.</p></div>
+<div class="paragraph" id="xmp-ensemble-methods"><div class="title">Listing 31: Ensemble Method</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+
+ <span class='nx-comment'># Define an ensemble method "string" with sub-methods
+</span> <span class='nx-comment'># "length", "tolower" and "info"
+</span>
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string length"</span> {x} {....}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string tolower"</span> {x} {...}
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> <span class='nx-string'>"string info"</span> {x} {...}
+ <span class='nx-comment'>#...
+</span> <span class='nx-keyword'>:create</span> c1
+}
+
+<span class='nx-comment'># Invoke the ensemble method
+</span>c1 <span class='nx-keyword'>string</span> length <span class='nx-string'>"hello world"</span></pre></div></div>
+</div>
+<div class="sect2">
+<h3 id="_method_resolution">3.6. Method Resolution</h3>
+<div class="paragraph"><p>When a method is invoked, the applicable method is searched in the
+following order:</p></div>
+Per-object Mixins -> Per-class Mixins -> Object -> Intrinsic Class Hierarchy
+<div class="paragraph"><p>In the case, no mixins are involved, first the object is searched for
+an object method with the given name, and then the class hierarchy
+of the object. The method can be defined multiple times on the search
+path, so some of these method definitions might be <em>shadowed</em> by the
+more specific definitions.</p></div>
+<div class="paragraph" id="xmp-method-resolution"><div class="title">Listing 32: Method Resolution with Intrinsic Classes</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> C {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
+ <span class='nx-keyword'>return</span> <span class='nx-string'>"C foo: [next]"</span>
+ }
+}
+
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D -superclass C {
+
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} {
+ <span class='nx-keyword'>return</span> <span class='nx-string'>"D foo: [next]"</span>
+ }
+
+ <span class='nx-keyword'>:create</span> d1 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {} {
+ <span class='nx-keyword'>return</span> <span class='nx-string'>"d1 foo: [next]"</span>
+ }
+ }
+}
+
+<span class='nx-comment'># Invoke the method foo
+</span>d1 foo
+<span class='nx-comment'># result: "d1 foo: D foo: C foo: "
+</span>
+<span class='nx-comment'># Query the precedence order from NX via introspection
+</span>d1 <span class='nx-keyword'>info</span> precedence
+<span class='nx-comment'># result: "::D ::C ::nx::Object"</span></pre></div></div>
+<div class="paragraph"><p>Consider the example in
+<a href="#xmp-method-resolution">Listing 32</a>. When the method
+<code>foo</code> is invoked on object <code>d1</code>, the object method has the highest
+precedence and is therefore invoked. The object methods shadows
+the same-named methods in the class hierarchy, namely the method <code>foo</code>
+of class <code>D</code> and the method <code>foo</code> of class <code>C</code>. The shadowed methods
+can be still invoked, either via the primitive <code>next</code> or via method
+handles (we used already method handles in the section about method
+aliases). In the example above, <code>next</code> calls the shadowed method and
+add their results to the results of every method. So, the final result
+contains parts from <code>d1</code>, <code>D</code> and <code>C</code>. Note that the topmost <code>next</code>
+in method <code>foo</code> of class <code>C</code> shadows no method <code>foo</code> and simply
+returns empty (and not an error message).</p></div>
+<div class="paragraph"><p>The introspection method <code>info precedence</code> provides information about
+the order, in which classes processed during method resolution.</p></div>
+<div class="paragraph" id="xmp-method-resolution2"><div class="title">Listing 33: Method Resolution with Mixin Classes</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> M1 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} { <span class='nx-keyword'>return</span> <span class='nx-string'>"M1 foo: [next]"</span>}
+}
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> M2 {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {} { <span class='nx-keyword'>return</span> <span class='nx-string'>"M2 foo: [next]"</span>}
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># "d1" is created based on the definitions of the last example
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># Add the methods from "M1" as per-object mixin to "d1"
+</span>d1 <span class='nx-keyword'>object</span> mixins add M1
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Add the methods from "M2" as per-class mixin to class "C"
+</span>C mixins add M2
+
+<span class='nx-comment'># Invoke the method foo
+</span>d1 foo
+<span class='nx-comment'># result: "M1 foo: M2 foo: d1 foo: D foo: C foo: "
+</span>
+<span class='nx-comment'># Query the precedence order from NX via introspection
+</span>d1 <span class='nx-keyword'>info</span> precedence
+<span class='nx-comment'># result: "::M1 ::M2 ::D ::C ::nx::Object"</span></pre></div></div>
+<div class="paragraph"><p>The example in <a href="#xmp-method-resolution2">Listing 33</a> is
+an extension of the previous example. We define here two additional
+classes <code>M1</code> and <code>M2</code> which are used as per-object and per-class
+mixins. Both classes define the method <code>foo</code>, these methods shadow
+the definitions of the intrinsic class hierarchy. Therefore an
+invocation of <code>foo</code> on object <code>d1</code> causes first an invocation of
+method in the per-object mixin.</p></div>
+<div class="paragraph" id="xmp-method-resolution3"><div class="title">Listing 34: Method Invocation Flags</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># "d1" is created based on the definitions of the last two examples,
+</span><span class='nx-comment'># the mixins "M1" and "M2" are registered.
+</span><span class='nx-comment'>#
+</span><span class='nx-comment'># Define a public object method "bar", which calls the method
+</span><span class='nx-comment'># "foo" which various invocation options:
+</span><span class='nx-comment'>#
+</span>d1 <span class='nx-keyword'>public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {} {
+ <span class='nx-keyword'>puts</span> [:foo]
+ <span class='nx-keyword'>puts</span> [: -local foo]
+ <span class='nx-keyword'>puts</span> [: -intrinsic foo]
+ <span class='nx-keyword'>puts</span> [: -system foo]
+}
+
+<span class='nx-comment'># Invoke the method "bar"
+</span>d1 bar</pre></div></div>
+<div class="paragraph"><p>In the first line of the body of method <code>bar</code>, the method <code>foo</code> is
+called as usual with an implicit receiver, which defaults to the
+current object (therefore, the call is equivalent to <code>d1 foo</code>). The
+next three calls show how to provide flags that influence the method
+resolution. The flags can be provided between the colon and the method
+name. These flags are used rather seldom but can be helpful in some
+situations.</p></div>
+<div class="paragraph"><p>The invocation flag <code>-local</code> means that the method has to be resolved
+from the same place, where the current method is defined. Since the
+current method is defined as a object method, <code>foo</code> is resolved as
+a object method. The effect is that the mixin definitions are
+ignored. The invocation flag <code>-local</code> was already introduced int the
+section about method protection, where it was used to call <em>private</em>
+methods.</p></div>
+<div class="paragraph"><p>The invocation flag <code>-intrinsic</code> means that the method has to be resolved
+from the intrinsic definitions, meaning simply without mixins. The
+effect is here the same as with the invocation flag <code>-local</code>.</p></div>
+<div class="paragraph"><p>The invocation flag <code>-system</code> means that the method has to be resolved
+from basic - typically predefined - classes of the object system. This
+can be useful, when script overloads system methods, but still want to
+call the shadowed methods from the base classes. In our case, we have
+no definitions of <code>foo</code> on the base clases, therefore an error message
+is returned.</p></div>
+<div class="paragraph"><p>The output of <a href="#xmp-method-resolution3">Listing 34</a> is:</p></div>
+<div class="listingblock">
+<div class="content">
+<pre><code> M1 foo: M2 foo: d1 foo: D foo: C foo:
+ d1 foo: D foo: C foo:
+ d1 foo: D foo: C foo:
+ ::d1: unable to dispatch method 'foo'</code></pre>
+</div></div>
+</div>
+<div class="sect2">
+<h3 id="_parameters">3.7. Parameters</h3>
+<div class="paragraph"><p>NX provides a generalized mechanism for passing values to either
+methods (we refer to these as <em>method parameters</em>) or to objects
+(these are called <em>configure parameters</em>). Both kind of parameters
+might have different features, such as:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+Positional and non-positional parameters
+</p>
+</li>
+<li>
+<p>
+Required and non-required parameters
+</p>
+</li>
+<li>
+<p>
+Default values for parameters
+</p>
+</li>
+<li>
+<p>
+Value-checking for parameters
+</p>
+</li>
+<li>
+<p>
+Multiplicity of parameters
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>TODO: complete list above and provide a short summary of the section</p></div>
+<div class="paragraph"><p>Before we discuss method and configure parameters in more detail, we
+describe the parameter features in the subsequent sections based on
+method parameters.</p></div>
+<div class="sect3">
+<h4 id="_positional_and_non_positional_parameters">3.7.1. Positional and Non-Positional Parameters</h4>
+<div class="paragraph"><p>If the position of a parameter in the list of formal arguments
+(e.g. passed to a function) is significant for its meaning, this is a
+<em>positional</em> parameter. If the meaning of the parameter is independent
+of its position, this is a <em>non-positional</em> parameter. When we call a
+method with positional parameters, the meaning of the parameters (the
+association with the argument in the argument list of the method) is
+determined by its position. When we call a method with non-positional
+parameters, their meaning is determined via a name passed with the
+argument during invocation.</p></div>
+<div class="paragraph" id="xmp-posnonpos"><div class="title">Listing 35: Positional and Non-Positional Method Parameters</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o1 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Method foo has positional parameters:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x y} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Method bar has non-positional parameters:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {-x -y} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Method baz has non-positional and
+</span> <span class='nx-comment'># positional parameters:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {-x -y a} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x? [info exists x] y? [info exists y] a=$a"</span>
+ }
+}
+
+<span class='nx-comment'># invoke foo (positional parameters)
+</span>o1 foo 1 2
+
+<span class='nx-comment'># invoke bar (non-positional parameters)
+</span>o1 bar -y 3 -x 1
+o1 bar -x 1 -y 3
+
+<span class='nx-comment'># invoke baz (positional and non-positional parameters)
+</span>o1 baz -x 1 100
+o1 baz 200
+o1 baz -- -y</pre></div></div>
+<div class="paragraph"><p>Consider the example in <a href="#xmp-posnonpos">Listing 35</a>. The method
+<code>foo</code> has the argument list <code>x y</code>. This means that the first argument
+is passed in an invocation like <code>o1 foo 1 2</code> to <code>x</code> (here, the value
+<code>1</code>), and the second argument is passed to <code>y</code> (here the value <code>2</code>).
+Method <code>bar</code> has in contrary just with non-positional arguments. Here
+we pass the names of the parameter together with the values. In the
+invocation <code>o1 bar -y 3 -x 1</code> the names of the parameters are prefixed
+with a dash ("-"). No matter whether in which order we write the
+non-positional parameters in the invocation (see line 30 and 31 in
+<a href="#xmp-posnonpos">Listing 35</a>) in both cases the variables <code>x</code>
+and <code>y</code> in the body of the method <code>bar</code> get the same values assigned
+(<code>x</code> becomes <code>1</code>, <code>y</code> becomes <code>3</code>).</p></div>
+<div class="paragraph"><p>It is certainly possible to combine positional and non-positional
+arguments. Method <code>baz</code> provides two non-positional parameter (<code>-y</code>
+and <code>-y</code>) and one positional parameter (namely <code>a</code>). The invocation in
+line 34 passes the value of <code>1</code> to <code>x</code> and the value of <code>100</code> to <code>a</code>.
+There is no value passed to <code>y</code>, therefore value of <code>y</code> will be
+undefined in the body of <code>baz</code>, <code>info exists y</code> checks for the
+existence of the variable <code>y</code> and returns <code>0</code>.</p></div>
+<div class="paragraph"><p>The invocation in line 35 passes only a value to the positional
+parameter. A more tricky case is in line 36, where we want to pass
+<code>-y</code> as a value to the positional parameter <code>a</code>. The case is more
+tricky since syntactically the argument parser might consider <code>-y</code> as
+the name of one of the non-positional parameter. Therefore we use <code>--</code>
+(double dash) to indicate the end of the block of the non-positional
+parameters and therefore the value of <code>-y</code> is passed to <code>a</code>.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_optional_and_required_parameters">3.7.2. Optional and Required Parameters</h4>
+<div class="paragraph"><p>Per default positional parameters are required, and non-positional
+parameters are optional (they can be left out). By using parameter
+options, we can as well define positional parameters, which are
+optional, and non-positional parameters, which are required.</p></div>
+<div class="paragraph" id="xmp-optional-req"><div class="title">Listing 36: Optional and Required Method Parameters</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o2 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Method foo has one required and one optional
+</span> <span class='nx-comment'># positional parameter:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:required y:optional} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y? [info exists y]"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Method bar has one required and one optional
+</span> <span class='nx-comment'># non-positional parameter:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {-x:required -y:optional} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y? [info exists y]"</span>
+ }
+}
+
+<span class='nx-comment'># invoke foo (one optional positional parameter is missing)
+</span>o2 foo 1</pre></div></div>
+<div class="paragraph"><p>The example in <a href="#xmp-optional-req">Listing 36</a> defined method <code>foo</code>
+with one required and one optional positional parameter. For this
+purpose we use the parameter options <code>required</code> and <code>optional</code>. The
+parameter options are separated from the parameter name by a colon. If
+there are multiple parameter options, these are separated by commas
+(we show this in later examples).</p></div>
+<div class="paragraph"><p>The parameter definition <code>x:required</code> for method <code>foo</code> is equivalent
+to <code>x</code> without any parameter options (see e.g. previous example),
+since positional parameters are per default required. The invocation
+in line 21 of <a href="#xmp-optional-req">Listing 36</a> will lead to an
+undefined variable <code>y</code> in method <code>foo</code>, because no value us passed to
+the optional parameter. Note that only trailing positional parameters might be
+optional. If we would call method <code>foo</code> of <a href="#xmp-posnonpos">Listing 35</a> with only one argument, the system would raise an
+exception.</p></div>
+<div class="paragraph"><p>Similarly, we define method <code>bar</code> in <a href="#xmp-optional-req">Listing 36</a> with one required and one optional non-positional
+parameter. The parameter definition <code>-y:optional</code> is equivalent to
+<code>-y</code>, since non-positional parameter are per default optional.
+However, the non-positional parameter <code>-x:required</code> is required. If we
+invoke <code>bar</code> without it, the system will raise an exception.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_default_values_for_parameters">3.7.3. Default Values for Parameters</h4>
+<div class="paragraph"><p>Optional parameters might have a default value. This default value is used,
+when no argument is provided for the corresponding parameter. Default values can be
+specified for positional and non-positional parameters.</p></div>
+<div class="paragraph" id="xmp-default-value"><div class="title">Listing 37: Method Parameters with Default Values</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o3 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Positional parameter with default value:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {{x 1} {y 2}} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Non-positional parameter with default value:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {{-x 10} {-y 20}} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x y=$y"</span>
+ }
+}
+
+<span class='nx-comment'># use default values
+</span>o3 foo
+o3 bar</pre></div></div>
+<div class="paragraph"><p>In order to define a default value for a parameter, the parameter
+specification must be of the form of a 2 element list, where the
+second argument is the default value. See for an example in
+<a href="#xmp-default-value">Listing 37</a>.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_value_constraints">3.7.4. Value Constraints</h4>
+<div class="paragraph"><p>NX provides value constraints for all kind of parameters. By
+specifying value constraints a developer can restrict the permissible
+values for a parameter and document the expected values in the source
+code. Value checking in NX is conditional, it can be turned on or off
+in general or on a per-usage level (more about this later). The same
+mechanisms can be used not only for input value checking, but as well
+for return value checking (we will address this point as well later).</p></div>
+<div class="sect4">
+<h5 id="_built_in_value_constraints">Built-in Value Constraints</h5>
+<div class="paragraph"><p>NX comes with a set of built-in value constraints, which can be
+extended on the scripting level. The built-in checkers are either the
+native checkers provided directly by the Next Scripting Framework (the
+most efficient checkers) or the value checkers provided by Tcl through
+<code>string is …</code>. The built-in checkers have as well the advantage that
+they can be used also at any time during bootstrap of an object
+system, at a time, when e.g. no objects or methods are defined. The
+same checkers are used as well for all C-implemented primitives of NX
+and the Next Scripting Framework.</p></div>
+<div class="imageblock" id="img-value-checkers" style="text-align:center;">
+<div class="content">
+<img src="value-checkers.png" alt="value-checkers.png" />
+</div>
+<div class="title">Figure 38. General Applicable Value Checkers in NX</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p><a href="#img-value-checkers">Figure 38</a> shows the built-in
+general applicable value checkers available in NX, which can be used
+for all method and configure parameters. In the next step, we show how to
+use these value-checkers for checking permissible values for method
+parameters. Then we will show, how to provide more detailed value
+constraints.</p></div>
+<div class="paragraph" id="xmp-value-check"><div class="title">Listing 39: Method Parameters with Value Constraints</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o4 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Positional parameter with value constraints:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:integer o<span class='nx-keyword'>:object</span>,optional} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x o? [info exists o]"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Non-positional parameter with value constraints:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {{-x:integer 10} {-verbose:boolean false}} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x verbose=$verbose"</span>
+ }
+}
+
+<span class='nx-comment'># The following invocation raises an exception, since the
+</span><span class='nx-comment'># value "a" for parameter "x" is not an integer
+</span>o4 foo a</pre></div></div>
+<div class="paragraph"><p>Value constraints are specified as parameter options in the parameter
+specifications. The parameter specification <code>x:integer</code> defines <code>x</code> as
+a required positional parameter which value is constraint to an
+integer. The parameter specification <code>o:object,optional</code> shows how to
+combine multiple parameter options. The parameter <code>o</code> is an optional
+positional parameter, its value must be an object (see
+<a href="#xmp-value-check">Listing 39</a>). Value constraints are
+specified exactly the same way for non-positional parameters (see
+method <code>bar</code> in <a href="#xmp-value-check">Listing 39</a>).</p></div>
+<div class="paragraph" id="xmp-check-parameterized"><div class="title">Listing 40: Parameterized Value Constraints</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Create classes for Person and Project
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Project
+
+<span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o5 {
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Parameterized value constraints
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> work {
+ -person<span class='nx-keyword'>:object</span>,type=Person
+ -project<span class='nx-keyword'>:object</span>,type=Project
+ } {
+ <span class='nx-comment'># ...
+</span> }
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Create a Person and a Project instance
+</span><span class='nx-comment'>#
+</span>Person <span class='nx-keyword'>create</span> gustaf
+Project <span class='nx-keyword'>create</span> nx
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Use method with value constraints
+</span><span class='nx-comment'>#
+</span>o5 work -person gustaf -project nx</pre></div></div>
+<div class="paragraph"><p>The native checkers <code>object</code>, <code>class</code>, <code>metaclass</code> and <code>baseclass</code> can
+be further specialized with the parameter option <code>type</code> to restrict
+the permissible values to instances of certain classes. We can use for
+example the native value constraint <code>object</code> either for testing
+whether an argument is some object (without further constraints, as in
+<a href="#xmp-default-value">Listing 37</a>, method <code>foo</code>), or we can
+constrain the value further to some type (direct or indirect instance
+of a class). This is shown by method <code>work</code> in
+<a href="#xmp-check-parameterized">Listing 40</a> which requires
+the parameter <code>-person</code> to be an instance of class <code>Person</code> and the
+parameter <code>-project</code> to be an instance of class <code>Project</code>.</p></div>
+</div>
+<div class="sect4">
+<h5 id="_scripted_value_constraints">Scripted Value Constraints</h5>
+<div class="paragraph"><p>The set of predefined value checkers can be extended by application
+programs via defining methods following certain conventions. The user
+defined value checkers are defined as methods of the class <code>nx::Slot</code>
+or of one of its subclasses or instances. We will address such cases
+in the next sections. In the following example we define two new
+value checkers on class <code>nx::Slot</code>. The first value checker is called
+<code>groupsize</code>, the second one is called <code>choice</code>.</p></div>
+<div class="paragraph" id="xmp-user-types"><div class="title">Listing 41: Scripted Value Checker for Method Parameters</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Value checker named "groupsize"
+</span><span class='nx-comment'>#
+</span>::nx::Slot <span class='nx-keyword'>method</span> type=groupsize {name value} {
+ <span class='nx-keyword'>if</span> {<span class='nx-variable'>$value</span> < 1 || <span class='nx-variable'>$value</span> > 6} {
+ <span class='nx-keyword'>error</span> <span class='nx-string'>"Value '$value' of parameter $name is not between 1 and 6"</span>
+ }
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Value checker named "choice" with extra argument
+</span><span class='nx-comment'>#
+</span>::nx::Slot <span class='nx-keyword'>method</span> type=choice {name value arg} {
+ <span class='nx-keyword'>if</span> {<span class='nx-variable'>$value</span> ni [<span class='nx-keyword'>split</span> <span class='nx-variable'>$arg</span> |]} {
+ <span class='nx-keyword'>error</span> <span class='nx-string'>"Value '$value' of parameter $name not in permissible values $arg"</span>
+ }
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Create an application class D
+</span><span class='nx-comment'># using the new value checkers
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> D {
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> foo {a:groupsize} {
+ <span class='nx-comment'># ...
+</span> }
+ <span class='nx-keyword'>:public</span> <span class='nx-keyword'>method</span> bar {a:choice,arg=red|yellow|green b:choice,arg=good|bad} {
+ <span class='nx-comment'># ...
+</span> }
+}
+
+D <span class='nx-keyword'>create</span> d1
+
+<span class='nx-comment'># testing "groupsize";
+</span><span class='nx-comment'># the second call (with value 10) will raise an exception:
+</span>d1 foo 2
+d1 foo 10
+
+<span class='nx-comment'># testing "choice"
+</span><span class='nx-comment'># the second call (with value pink for parameter a)
+</span><span class='nx-comment'># will raise an exception:
+</span>d1 bar green good
+d1 bar pink bad</pre></div></div>
+<div class="paragraph"><p>In order to define a checker <code>groupsize</code> a method of the name
+<code>type=groupsize</code> is defined. This method receives two arguments,
+<code>name</code> and <code>value</code>. The first argument is the name of the parameter
+(mostly used for the error message) and the second parameter is
+provided value. The value checker simply tests whether the provided
+value is between 1 and 3 and raises an exception if this is not the
+case (invocation in line 36 in <a href="#xmp-user-types">Listing 41</a>).</p></div>
+<div class="paragraph"><p>The checker <code>groupsize</code> has the permissible values defined in its
+method’s body. It is as well possible to define more generic checkers
+that can be parameterized. For this parameterization, one can pass an
+argument to the checker method (last argument). The checker <code>choice</code>
+can be used for restricting the values to a set of predefined
+constants. This set is defined in the parameter specification. The
+parameter <code>a</code> of method <code>bar</code> in <a href="#xmp-user-types">Listing 41</a>
+is restricted to the values <code>red</code>, <code>yellow</code> or <code>green</code>, and the
+parameter <code>b</code> is restricted to <code>good</code> or <code>bad</code>. Note that the syntax
+of the permissible values is solely defined by the definition of the
+value checker in lines 13 to 17. The invocation in line 39 will be ok,
+the invocation in line 40 will raise an exception, since <code>pink</code> is not
+allowed.</p></div>
+<div class="paragraph"><p>If the same checks are used in many places in the program,
+defining names for the value checker will be the better choice since
+it improves maintainability. For seldom used kind of checks, the
+parameterized value checkers might be more convenient.</p></div>
+</div>
+</div>
+<div class="sect3">
+<h4 id="_multiplicity">3.7.5. Multiplicity</h4>
+<div class="sidebarblock">
+<div class="content">
+<div class="paragraph"><p><strong>Multiplicity</strong> is used to define whether a parameter should receive
+single or multiple values.</p></div>
+</div></div>
+<div class="paragraph"><p>A multiplicity specification has a lower and an upper bound. A lower
+bound of <code>0</code> means that the value might be empty. A lower bound of <code>1</code>
+means that the parameter needs at least one value. The upper bound
+might be <code>1</code> or <code>n</code> (or synonymously <code>*</code>). While the upper bound of
+<code>1</code> states that at most one value has to be passed, the upper bound of
+<code>n</code> says that multiple values are permitted. Other kinds of
+multiplicity are currently not allowed.</p></div>
+<div class="paragraph"><p>The multiplicity is written as parameter option in the parameter
+specification in the form <em>lower-bound</em>..<em>upper-bound</em>. If no
+multiplicity is defined the default multiplicity is <code>1..1</code>, which
+means: provide exactly one (atomic) value (this was the case in the
+previous examples).</p></div>
+<div class="paragraph" id="xmp-multiplicity"><div class="title">Listing 42: Method Parameters with Explicit Multiplicity</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Object</span> <span class='nx-keyword'>create</span> o6 {
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Positional parameter with an possibly empty
+</span> <span class='nx-comment'># single value
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> foo {x:integer,0..1} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Positional parameter with an possibly empty
+</span> <span class='nx-comment'># list of values value
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> bar {x:integer,0..n} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
+ }
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># Positional parameter with a non-empty
+</span> <span class='nx-comment'># list of values
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> baz {x:integer,1..n} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"x=$x"</span>
+ }
+}</pre></div></div>
+<div class="paragraph"><p><a href="#xmp-multiplicity">Listing 42</a> contains three examples for
+positional parameters with different multiplicities. Multiplicity is
+often combined with value constraints. A parameter specification of
+the form <code>x:integer,0..n</code> means that the parameter <code>x</code> receives a list
+of integers, which might be empty. Note that the value constraints are
+applied to every single element of the list.</p></div>
+<div class="paragraph"><p>The parameter specification <code>x:integer,0..1</code> means that <code>x</code> might be
+an integer or it might be empty. This is one style of specifying that
+no explicit value is passed for a certain parameter. Another style is
+to use required or optional parameters. NX does not enforce any
+particular style for handling unspecified values.</p></div>
+<div class="paragraph"><p>All the examples in <a href="#xmp-multiplicity">Listing 42</a> are for
+single positional parameters. Certainly, multiplicity is fully
+orthogonal with the other parameter features and can be used as well
+for multiple parameters, non-positional parameter, default values,
+etc.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_defaults_substitution">3.7.6. Defaults substitution</h4>
+<div class="paragraph"><p>Optional object and method parameters can set a default value. Recall
+that default values can be specified for positional and non-positional
+parameters, alike. This default value is used to define a
+corresponding method-local and object variable, respectively, and to
+set it to the default value. By default, the default value is taken
+literally (without any substitutions). Default values can also be
+preprocessed into a final value using Tcl substitution as provided by
+the Tcl <code>[subst]</code> command. To control the kind of substitutions to be
+performed, the parameter option <code>substdefault</code> can be provided.</p></div>
+<div class="paragraph" id="substdefault"><div class="title">Listing 43: Default-value substitution using <code>substdefault</code></div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> ::D
+<span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> ::C {
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># By default all substitutions (command, variable, control
+</span> <span class='nx-comment'># characters) are active, when "substdefault" is used:
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:property</span> {d<span class='nx-keyword'>:object</span>,type=::D,substdefault {[::D <span class='nx-keyword'>new</span>]}}
+
+ <span class='nx-comment'>#
+</span> <span class='nx-comment'># The actual property values are computed and
+</span> <span class='nx-comment'># set at instantiation time.
+</span> <span class='nx-comment'>#
+</span> <span class='nx-keyword'>:create</span> ::c
+}
+
+::c <span class='nx-keyword'>cget</span> -d</pre></div></div>
+<div class="paragraph"><p><a href="#substdefault">Listing 43</a> uses <code>substdefault</code>
+to provide a default value for the property <code>d</code>. In this example, the
+default value is a fresh instance of
+class <code>::D</code>. When the parameter option <code>substdefault</code> is used
+default, all substitution kinds of Tcl are active: command, variable, and
+backslash substitution. <code>substdefault</code> can be
+parametrized to include or to exclude any combination of substitution
+kinds by providing a bitmask:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+<code>substdefault=0b111</code>: all substitutions active (default)
+</p>
+</li>
+<li>
+<p>
+<code>substdefault=0b100</code>: substitute backslashes only (like <code>subst -novariables -nocommands</code>)
+</p>
+</li>
+<li>
+<p>
+<code>substdefault=0b010</code>: substitute variables only (like <code>subst -nobackslashes -nocommands</code>)
+</p>
+</li>
+<li>
+<p>
+<code>substdefault=0b001</code>: substitute commands only (like <code>subst -nobackslashes -novariables</code>)
+</p>
+</li>
+<li>
+<p>
+<code>substdefault=0b000</code>: substitute nothing (like <code>subst -nobackslashes -nocommands -novariables</code>, noop)
+</p>
+</li>
+</ul></div>
+</div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_advanced_language_features">4. Advanced Language Features</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>…</p></div>
+<div class="sect2">
+<h3 id="_objects_classes_and_meta_classes">4.1. Objects, Classes and Meta-Classes</h3>
+<div class="paragraph"><p>…</p></div>
+</div>
+<div class="sect2">
+<h3 id="_resolution_order_and_next_path">4.2. Resolution Order and Next-Path</h3>
+<div class="paragraph"><p>…</p></div>
+</div>
+<div class="sect2">
+<h3 id="_details_on_method_and_configure_parameters">4.3. Details on Method and Configure Parameters</h3>
+<div class="paragraph"><p>The parameter specifications are used in NX for the following
+purposes. They are used for</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+the specification of input arguments of methods and commands, for
+</p>
+</li>
+<li>
+<p>
+the specification of return values of methods and commands, and for
+</p>
+</li>
+<li>
+<p>
+the specification for the initialization of objects.
+</p>
+</li>
+</ul></div>
+<div class="paragraph"><p>We refer to the first two as method parameters and the last one as
+configure parameters. The examples in the previous sections all parameter
+specification were specifications of method parameters.</p></div>
+<div class="sidebarblock">
+<div class="content">
+<div class="paragraph"><p><strong>Method parameters</strong> specify properties about permissible values passed
+to methods.</p></div>
+</div></div>
+<div class="paragraph"><p>The method parameter specify how methods are invoked, how the
+actual arguments are passed to local variables of the invoked method
+and what kind of checks should be performed on these.</p></div>
+<div class="sidebarblock">
+<div class="content">
+<div class="paragraph"><p><strong>Configure parameters</strong> are parameters that specify, how objects
+can be parameterized upon creation.</p></div>
+</div></div>
+<div class="paragraph"><p>Syntactically, configure parameters and method parameters are the same,
+although there are certain differences (e.g. some parameter options
+are only applicable for objects parameters, the list of object
+parameters is computed dynamically from the class structures, object
+parameters are often used in combination with special setter methods,
+etc.). Consider the following example, where we define the two
+application classes <code>Person</code> and <code>Student</code> with a few properties.</p></div>
+<div class="paragraph" id="xmp-object-parameters"><div class="title">Listing 44: Configure Parameters</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'>#
+</span><span class='nx-comment'># Define a class Person with properties "name"
+</span><span class='nx-comment'># and "birthday"
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Person {
+ <span class='nx-keyword'>:property</span> name:required
+ <span class='nx-keyword'>:property</span> birthday
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Define a class Student as specialization of Person
+</span><span class='nx-comment'># with and additional property
+</span><span class='nx-comment'>#
+</span><span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>create</span> Student -superclass Person {
+ <span class='nx-keyword'>:property</span> matnr:required
+ <span class='nx-keyword'>:property</span> {oncampus:boolean true}
+}
+
+<span class='nx-comment'>#
+</span><span class='nx-comment'># Create instances using configure parameters
+</span><span class='nx-comment'># for the initialization
+</span><span class='nx-comment'>#
+</span>Person <span class='nx-keyword'>create</span> p1 -name Bob
+Student <span class='nx-keyword'>create</span> s1 -name Susan -matnr 4711
+
+<span class='nx-comment'># Access property value via "cget" method
+</span><span class='nx-keyword'>puts</span> <span class='nx-string'>"The name of s1 is [s1 cget -name]"</span></pre></div></div>
+<div class="paragraph"><p>The class <code>Person</code> has two properties <code>name</code> and <code>birthday</code>, where the
+property <code>name</code> is required, the property <code>birthday</code> is not. The
+class <code>Student</code> is a subclass of <code>Person</code> with the additional required
+property <code>matnr</code> and an optional property <code>oncampus</code> with the
+default value <code>true</code> (see <a href="#xmp-object-parameters">Listing 44</a>). The class diagram below visualizes these
+definitions.</p></div>
+<div class="imageblock" id="img-configure-parameters" style="text-align:center;">
+<div class="content">
+<img src="configure-parameter.png" alt="configure-parameter.png" />
+</div>
+<div class="title">Figure 45. System and Application Classes</div>
+</div>
+<div class="paragraph"><p></p></div>
+<div class="paragraph"><p>In NX, these definitions imply that instances of the class of <code>Person</code>
+have the properties <code>name</code> and <code>birthday</code> as <em>non-positional object
+parameters</em>. Furthermore it implies that instances of <code>Student</code> will
+have the configure parameters of <code>Person</code> augmented with the object
+parameters from <code>Student</code> (namely <code>matnr</code> and <code>oncampus</code>). Based on
+these configure parameters, we can create a <code>Person</code> named <code>Bob</code> and a
+<code>Student</code> named <code>Susan</code> with the matriculation number <code>4711</code> (see line
+23 and 24 in <<xmp-object-parameters,
+instance variables <code>name</code>, <code>matnr</code> and <code>oncampus</code> (the latter is
+initialized with the default value).</p></div>
+<div class="sect3">
+<h4 id="_configure_parameters_available_for_all_nx_objects">4.3.1. Configure Parameters available for all NX Objects</h4>
+<div class="paragraph"><p>The configure parameters are not limited to the application defined
+properties, also NX provides some predefined definitions. Since
+<code>Person</code> is a subclass of <code>nx::Object</code> also the configure parameters of
+<code>nx::Object</code> are inherited. In the introductory stack example, we used
+<code>-mixins</code> applied to an object to denote per-object mixins (see
+<a href="#xmp-using-class-safety">Listing 8</a>). Since <code>mixins</code>
+is defined as a parameter on <code>nx::Object</code> it can be used as an object
+parameter <code>-mixins</code> for all objects in NX. To put it in other words,
+every object can be configured to have per-object mixins. If we would
+remove this definition, this feature would be removed as well.</p></div>
+<div class="paragraph"><p>As shown in the introductory examples, every object can be configured
+via a scripted initialization block (the optional scripted block
+specified at object creation as last argument; see
+<a href="#xmp-object-stack">Listing 5</a> or
+<a href="#xmp-object-integer-stack">Listing 12</a>). The
+scripted block and its meaning are as well defined by the means of
+configure parameters. However, this configure parameter is positional (last
+argument) and optional (it can be omitted). The following listing shows
+the configure parameters of <code>Person p1</code> and <code>Student s1</code>.</p></div>
+<div class="paragraph" id="xmp-object-parameter-list"><div class="title">Listing 46: Computed Actual Configure Parameter</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>Configure parameters <span class='nx-keyword'>for</span> Person p1:
+ Command:
+ p1 <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
+ Result:
+ -name <span class='nx-placeholder'>/value/</span> ?-birthday <span class='nx-placeholder'>/value/</span>? ?-object-mixins /mixinreg .../<span class='nx-placeholder'>?
+ ?</span>-class /<span class='nx-keyword'>class</span>/? ?-object-filters /filterreg .../? ?/__initblock/?
+
+Configure parameter <span class='nx-keyword'>for</span> Student s1:
+ Command:
+ s1 <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
+ Result:
+ ?-oncampus <span class='nx-placeholder'>/boolean/</span>? -matnr <span class='nx-placeholder'>/value/</span> -name <span class='nx-placeholder'>/value/</span>
+ ?-birthday <span class='nx-placeholder'>/value/</span>? ?-object-mixins /mixinreg .../? ?-class /<span class='nx-keyword'>class</span>/<span class='nx-placeholder'>?
+ ?</span>-object-filters /filterreg .../? ?/__initblock/?</pre></div></div>
+<div class="paragraph"><p>The given parameter show, how (a) objects can be configured
+at runtime or (b) how new instances can be configured
+at creation time via the <code>new</code> or <code>create</code> methods.
+Introspection can be used to obtain the configuration
+parameters from an object via
+<code>p1 info lookup parameters configure</code>
+(returning the configure parameters currently applicable for
+<code>configure</code> or <code>cget</code>) or from a class
+<code>Person info lookup parameters create</code> on a class
+(returning the configure parameters applicable when an object
+of this class is created)</p></div>
+<div class="paragraph"><p>The listed configure parameter types <code>mixinreg</code> and
+<code>filterreg</code> are for converting definitions of filters and mixins. The
+last value <code>__initblock</code> says that the content of this variable
+will be executed in the context of the object being created (before
+the constructor <code>init</code> is called). More about the configure parameter
+types later.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_configure_parameters_available_for_all_nx_classes">4.3.2. Configure Parameters available for all NX Classes</h4>
+<div class="paragraph"><p>Since classes are certain kind of objects, classes are parameterized
+in the same way as objects. A typical parameter for a class definition
+is the relation of the class to its superclass.In our example, we have
+specified, that <code>Student</code> has <code>Person</code> as superclass via the
+non-positional configure parameter <code>-superclass</code>. If no superclass is
+specified for a class, the default superclass is
+<code>nx::Object</code>. Therefore <code>nx::Object</code> is the default value for the
+parameter <code>superclass</code>.</p></div>
+<div class="paragraph"><p>Another frequently used parameter for classes is <code>-mixins</code> to denote
+per-class mixins (see e.g. the introductory Stack example in
+<a href="#xmp-class-safestack">Listing 10</a>), which is defined in
+the same way.</p></div>
+<div class="paragraph"><p>Since <code>Student</code> is an instance of the meta-class <code>nx::Class</code> it
+inherits the configure parameters from <code>nx::Class</code> (see class diagram
+<a href="#img-configure-parameters">Figure 45</a>).
+Therefore, one can use e.g. <code>-superclass</code> in the definition of classes.</p></div>
+<div class="paragraph"><p>Since <code>nx::Class</code> is a subclass of <code>nx::Object</code>, the meta-class
+<code>nx::Class</code> inherits the parameter definitions from the most general
+class <code>nx::Object</code>. Therefore, every class might as well be configured
+with a scripted initialization block the same way as objects can be
+configured. We used actually this scripted initialization block in
+most examples for defining the methods of the class. The following
+listing shows (simplified) the parameters applicable for <code>Class
+Student</code>.</p></div>
+<div class="paragraph" id="xmp-class-parameter-list"><div class="title">Listing 47: Parameters for Classes</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>Configure parameter <span class='nx-keyword'>for</span> <span class='nx-keyword'>class</span> <span class='nx-keyword'>nx::Class</span>
+ Command:
+ <span class='nx-keyword'>nx::Class</span> <span class='nx-keyword'>info</span> <span class='nx-keyword'>lookup</span> syntax <span class='nx-keyword'>configure</span>
+ Result:
+ ?-superclass /<span class='nx-keyword'>class</span> .../? ?-mixins /mixinreg .../<span class='nx-placeholder'>?
+ ?</span>-filters /filterreg .../? ?-object-mixins /mixinreg .../<span class='nx-placeholder'>?
+ ?</span>-class /<span class='nx-keyword'>class</span>/? ?-object-filters /filterreg .../? ?/__initblock/?</pre></div></div>
+</div>
+<div class="sect3">
+<h4 id="_user_defined_parameter_types">4.3.3. User defined Parameter Types</h4>
+<div class="paragraph"><p>More detailed definition of the configure parameter types comes here.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_slot_classes_and_slot_objects">4.3.4. Slot Classes and Slot Objects</h4>
+<div class="paragraph"><p>In one of the previous sections, we defined scripted (application
+defined) checker methods on a class named <code>nx::Slot</code>. In general NX
+offers the possibility to define value checkers not only for all
+usages of parameters but as well differently for method parameters or
+configure parameters</p></div>
+<div class="imageblock" id="img-slots" style="text-align:center;">
+<div class="content">
+<img src="slots.png" alt="slots.png" />
+</div>
+<div class="title">Figure 48. Slot Classes and Objects</div>
+</div>
+<div class="paragraph"><p></p></div>
+</div>
+<div class="sect3">
+<h4 id="_attribute_slots">4.3.5. Attribute Slots</h4>
+<div class="paragraph"><p>Still Missing</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+return value checking
+</p>
+</li>
+<li>
+<p>
+switch
+</p>
+</li>
+<li>
+<p>
+initcmd …
+</p>
+</li>
+<li>
+<p>
+subst rules
+</p>
+</li>
+<li>
+<p>
+converter
+</p>
+</li>
+<li>
+<p>
+incremental slots
+</p>
+</li>
+</ul></div>
+</div>
+</div>
+</div>
+</div>
+<div class="sect1">
+<h2 id="_miscellaneous">5. Miscellaneous</h2>
+<div class="sectionbody">
+<div class="paragraph"><p>…</p></div>
+<div class="sect2">
+<h3 id="_profiling">5.1. Profiling</h3>
+<div class="paragraph"><p>…</p></div>
+</div>
+<div class="sect2">
+<h3 id="_unknown_handlers">5.2. Unknown Handlers</h3>
+<div class="paragraph"><p>NX provides two kinds of unknown handlers:</p></div>
+<div class="ulist"><ul>
+<li>
+<p>
+Unknown handlers for methods
+</p>
+</li>
+<li>
+<p>
+Unknown handlers for objects and classes
+</p>
+</li>
+</ul></div>
+<div class="sect3">
+<h4 id="_unknown_handlers_for_methods">5.2.1. Unknown Handlers for Methods</h4>
+<div class="paragraph"><p>Object and classes might be equipped
+with a method <code>unknown</code> which is called in cases, where an unknown
+method is called. The method unknown receives as first argument the
+called method followed by the provided arguments</p></div>
+<div class="paragraph" id="xmp-unknown-method"><div class="title">Listing 49: Unknown Method Handler</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nx::Object <span class='nx-keyword'>create</span> o {
+ <span class='nx-keyword'>:object</span> <span class='nx-keyword'>method</span> <span class='nx-keyword'>unknown</span> {called_method args} {
+ <span class='nx-keyword'>puts</span> <span class='nx-string'>"Unknown method '$called_method' called"</span>
+ }
+}
+
+<span class='nx-comment'># Invoke an unknown method for object o:
+</span>o foo 1 2 3
+
+<span class='nx-comment'># Output will be: "Unknown method 'foo' called"</span></pre></div></div>
+<div class="paragraph"><p>Without any provision of an unknown method handler, an error will be
+raised, when an unknown method is called.</p></div>
+</div>
+<div class="sect3">
+<h4 id="_unknown_handlers_for_objects_and_classes">5.2.2. Unknown Handlers for Objects and Classes</h4>
+<div class="paragraph"><p>The next scripting framework provides in addition to unknown method
+handlers also a means to dynamically create objects and classes, when
+these are referenced. This happens e.g. when superclasses, mixins, or
+parent objects are referenced. This mechanism can be used to implement
+e.g. lazy loading of these classes. Nsf allows one to register multiple
+unknown handlers, each identified by a key (a unique name, different
+from the keys of other unknown handlers).</p></div>
+<div class="paragraph" id="xmp-unknown-class"><div class="title">Listing 50: Unknown Class Handler</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'>::nx::Class <span class='nx-keyword'>public</span> <span class='nx-keyword'>object</span> <span class='nx-keyword'>method</span> __unknown {name} {
+ <span class='nx-comment'># A very simple unknown handler, showing just how
+</span> <span class='nx-comment'># the mechanism works.
+</span> <span class='nx-keyword'>puts</span> <span class='nx-string'>"***** __unknown called with <$name>"</span>
+ ::nx::Class <span class='nx-keyword'>create</span> <span class='nx-variable'>$name</span>
+}
+
+<span class='nx-comment'># Register an unknown handler as a method of ::nx::Class
+</span>::nsf::object::unknown::add nx {::nx::Class __unknown}
+
+::nx::Object <span class='nx-keyword'>create</span> o {
+ <span class='nx-comment'># The class M is unknown at this point
+</span>
+ <span class='nx-keyword'>:object</span> mixins add M
+ <span class='nx-comment'># The line above has triggered the unknown class handler,
+</span> <span class='nx-comment'># class M is now defined
+</span>
+ <span class='nx-keyword'>puts</span> [<span class='nx-keyword'>:info</span> <span class='nx-keyword'>object</span> mixins]
+ <span class='nx-comment'># The output will be:
+</span> <span class='nx-comment'># ***** __unknown called with <::M>
+</span> <span class='nx-comment'># ::M
+</span>}</pre></div></div>
+<div class="paragraph"><p>The Next Scripting Framework allows one to add, query, delete and list unknown handlers.</p></div>
+<div class="paragraph" id="xmp-unknown-registration"><div class="title">Listing 51: Unknown Handler registration</div><p></p></div>
+<div class="listingblock">
+<div class="content"><style type='text/css'>
+.nx {color: #000000; font-weight: normal; font-style: normal; padding-left: 10px}
+table.nx {border-collapse: collapse; border-spacing: 3px;}
+.nx-linenr {border-right: 1px solid #DDDDDD;padding-right: 5px; color: #2B547D;font-style: italic;}
+.nx-string {color: #779977; font-weight: normal; font-style: italic;}
+.nx-comment {color: #717ab3; font-weight: normal; font-style: italic;}
+.nx-keyword {color: #7f0055; font-weight: normal; font-style: normal;}
+.nx-placeholder {color: #AF663F; font-weight: normal; font-style: italic;}
+.nx-variable {color: #AF663F; font-weight: normal; font-style: normal;}
+</style>
+<pre class='nx'><span class='nx-comment'># Interface for unknown handlers:
+</span><span class='nx-comment'># nsf::object::unknown::add /key/ /handler/
+</span><span class='nx-comment'># nsf::object::unknown::get /key/
+</span><span class='nx-comment'># nsf::object::unknown::delete /key/
+</span><span class='nx-comment'># nsf::object::unknown::keys</span></pre></div></div>
+<div class="ulist bibliography"><div class="title">References</div><ul>
+<li>
+<p>
+<a id="Zdun"></a> U. Zdun, M. Strembeck, G. Neumann:
+ Object-Based and Class-Based Composition of Transitive Mixins,
+ Information and Software Technology, 49(8) 2007 .
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Zdun 1999a"></a> G. Neumann and U. Zdun: Filters as a
+ language support for design patterns in object-oriented scripting
+ languages. In Proceedings of COOTS’99, 5th Conference on
+ Object-Oriented Technologies and Systems, San Diego, May 1999.
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Zdun 1999b"></a> G. Neumann and U. Zdun: Implementing
+ object-specific design patterns using per-object mixins. In Proc. of
+ NOSA`99, Second Nordic Workshop on Software Architecture, Ronneby,
+ Sweden, August 1999.
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Zdun 1999c"></a> G. Neumann and U. Zdun: Enhancing
+ object-based system composition through per-object mixins. In
+ Proceedings of Asia-Pacific Software Engineering Conference (APSEC),
+ Takamatsu, Japan, December 1999.
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Zdun 2000a"></a> G. Neumann and U. Zdun: XOTCL, an
+ object-oriented scripting language. In Proceedings of Tcl2k: The
+ 7th USENIX Tcl/Tk Conference, Austin, Texas, February 2000.
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Zdun 2000b"></a> G. Neumann and U. Zdun: Towards the Usage
+ of Dynamic Object Aggregations as a Form of Composition In:
+ Proceedings of Symposium of Applied Computing (SAC’00), Como,
+ Italy, Mar 19-21, 2000.
+</p>
+</li>
+<li>
+<p>
+<a id="Neumann and Sobernig 2009"></a> G. Neumann, S. Sobernig: XOTcl 2.0 - A
+ Ten-Year Retrospective and Outlook, in: Proceedings of the Sixteenth
+ Annual Tcl/Tk Conference, Portland, Oregon, October, 2009.
+</p>
+</li>
+<li>
+<p>
+<a id="Ousterhout 1990"></a> J. K. Ousterhout: Tcl: An embeddable command
+ language. In Proc. of the 1990 Winter USENIX Conference, January 1990.
+</p>
+</li>
+<li>
+<p>
+<a id="Ousterhout 1998"></a> J. K. Ousterhout: Scripting: Higher Level
+ Programming for the 21st Century, IEEE Computer 31(3), March 1998.
+</p>
+</li>
+<li>
+<p>
+<a id="Wetherall and Lindblad 1995"></a> D. Wetherall and C. J. Lindblad: Extending Tcl for
+ Dynamic Object-Oriented Programming. Proc. of the Tcl/Tk Workshop '95,
+ July 1995.
+</p>
+</li>
+</ul></div>
+</div>
+</div>
+</div>
+</div>
+</div>
+<div id="footnotes"><hr /></div>
+<div id="footer">
+<div id="footer-text">
+Version 2.2.0<br />
+Last updated 2019-04-12 16:25:08 CEST
+</div>
+</div>
+</body>
+</html>
Index: library/xotcl/apps/comm/link-checker.xotcl
===================================================================
diff -u -r9a0b8bb0992be0561d8187c275fc1d9b7e0bbcd0 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- library/xotcl/apps/comm/link-checker.xotcl (.../link-checker.xotcl) (revision 9a0b8bb0992be0561d8187c275fc1d9b7e0bbcd0)
+++ library/xotcl/apps/comm/link-checker.xotcl (.../link-checker.xotcl) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -15,7 +15,7 @@
<tr><td>-local <td> A string match pattern to decide
which url should be treated as local
e.g. -local *wu-wien.ac.at/*
- Per default the locality filter ist set
+ Per default the locality filter is set
to the name of the host followed by '/*'</td></tr>
<tr><td>-restrict <td> 0 or 1, sets the locality filter to the subtree
implied by the URL</td></tr>
Index: library/xotcl/doc/Announce-1.6.0
===================================================================
diff -u -rb5c493afe905b1bafc17697ed3ce01d1662c77b3 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- library/xotcl/doc/Announce-1.6.0 (.../Announce-1.6.0) (revision b5c493afe905b1bafc17697ed3ce01d1662c77b3)
+++ library/xotcl/doc/Announce-1.6.0 (.../Announce-1.6.0) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -58,7 +58,7 @@
will be marked as deprecated in the near future.
Please note that the behavior of the match pattern has
- changed and is therefor not completely compatible with
+ changed and is therefore not completely compatible with
prior versions.
* New info subcommands:
Index: library/xotcl/doc/tutorial.html
===================================================================
diff -u -rcfb3421c9ebcc80ee2b48544717135b56c7c9946 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- library/xotcl/doc/tutorial.html (.../tutorial.html) (revision cfb3421c9ebcc80ee2b48544717135b56c7c9946)
+++ library/xotcl/doc/tutorial.html (.../tutorial.html) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -861,7 +861,7 @@
<P>Initially XOTcl offers two new commands: <tt>Object</tt> and
<tt>Class</tt>. They represent hooks to the features of the language.
This section discusses both of them in detail and shows how they
-function in the context of XOTcl. Note, that even if most of this is
+function in the context of XOTcl. Note that even if most of this is
compatible to OTcl, a few changes occur. For this reason, this
section is no introduction to plain OTcl. The <tt>Object</tt> command
provides access to the <tt>Object</tt> class, which holds the common
@@ -1024,7 +1024,7 @@
</P>
<LI><P STYLE="margin-bottom: 0in"><tt>self class</tt>: the self
command with the argument <tt>class</tt> returns the name of the
- class, which holds the currently executing instproc. Note, that this
+ class, which holds the currently executing instproc. Note that this
may be different to the class of the current object. If it is called
from a proc it returns an empty string.
</P>
@@ -1041,7 +1041,7 @@
<tt>my</tt> <tt>set</tt> persons($name) [<tt>clock</tt> seconds]
}
</pre><P>
-<P>Note, that there is a difference to the realization of these
+<P>Note that there is a difference to the realization of these
object information to OTcl. XOTcl uses commands in order to make
XOTcl-methods compatible to Tcl-procedures and accessible via
namespace-paths. OTcl uses the three variables <tt>self</tt>, <tt>class</tt>
@@ -1544,8 +1544,8 @@
leaves it's instances with the class <tt>Object</tt>.
</P>
<P>So all empty class- and superclass-relationships are automatically
-reset to <tt>Object</tt>. Note, that this are differences to OTcl,
-where the destruction of an class destroys all instances and an empty
+reset to <tt>Object</tt>. Note that this are differences to OTcl,
+where the destruction of a class destroys all instances and an empty
super-class list remains empty.
</P>
<H3><A NAME="class_method_chaining"></A>Method Chaining
@@ -1622,7 +1622,7 @@
four instance variables <tt>cookName</tt>, <tt>roomNumber</tt>,
<tt>doorPosition</tt> and <tt>stoveType</tt> set up with default
values in this order (since this is the order of the classes in the
-next-path). Note, that the order is important, because one missing
+next-path). Note that the order is important, because one missing
next call, in one of the <tt>init</tt> methods, means that succeeding
<tt>init</tt> methods will not be executed. This mechanism functions
equally on all kinds of instprocs, not only on constructors.
@@ -1754,8 +1754,7 @@
predefined meta-class <tt>Class</tt>, or by adding an instmixin class
(see <A HREF="per-class-mixins">below</A>) containing <tt>Class</tt>
to the precedence chain of the class. By defining <tt>Object
-instmixin Class</tt> one can even change the object system of XOTcl in
-in a way such that every created Object is a meta-class.
+instmixin Class</tt> one can even change the object system of XOTclin a way such that every created Object is a meta-class.
</P>
<P>Since the concept of a meta-class are sometimes
confusing to people of a background of some other programming
@@ -1970,7 +1969,7 @@
<tt>doInitializations</tt>.
</p>
<p>
- Note, that <tt>recreate</tt> is not called, when a someone tries
+ Note that <tt>recreate</tt> is not called, when a someone tries
to recreate a class as an object or an object as a class. In these
cases, <tt>destroy</tt> + <tt>create</tt> are used.
<pre CLASS="code">
@@ -2320,7 +2319,7 @@
<P>All messages to a filtered object must go through the filter before
they reach their destination object. A simple example would be a sole
filter on the class of the object. To define such a filter two steps
-are necessary. Firstly an filter method has to be defined, then the
+are necessary. Firstly a filter method has to be defined, then the
filter has to be registered. The filter method consists of three parts
which are all optional. A filter method has the following form:
</P>
@@ -2812,13 +2811,13 @@
</P>
The inverse operation of <tt>info mixin</tt> is <tt>mixinof</tt> finds
-out, into which objects an per-object mixin class is mixed into.
+out, into which objects a per-object mixin class is mixed into.
<pre CLASS="code">
<em>clsName</em> <tt>info</tt> mixinof <em>?pattern?</em>
</pre>
-<P> Note, that the constructors (init methods) of per-object mixins (and per-class mixins)
+<P> Note that the constructors (init methods) of per-object mixins (and per-class mixins)
are only called, if the mixin is registered already during object
initialization (when <tt>init</tt> is called). For per-object mixins, one can
achieve the initialization of a mixin via an idiom like
@@ -2827,7 +2826,7 @@
</pre>
that registers the mixin before <tt>init</tt> is called. When a mixin is registered
after object creation and it needs initializations, it is necessary to
-define special methods for this. Note, that the behavior described
+define special methods for this. Note that the behavior described
here is introduced in version 0.84 to ensure consistent behavior of
intrinsic classes, per-object and per-class mixins, and to achieve
predictable behavior for dynamic registration for all kind of mixins,
@@ -2897,7 +2896,7 @@
<em>className</em> <tt>instmixin</tt> <em>mixinList</em>
</pre>
The inverse operation of <tt>info inmixin</tt> is <tt>instmixinof</tt> finds
-out, into which objects an per-object mixin class is mixed into.
+out, into which objects a per-object mixin class is mixed into.
<pre CLASS="code">
<em>className</em> <tt>info</tt> instmixinof <em>?-closure? ?pattern?</em>
@@ -2962,7 +2961,7 @@
</P>
<p>Per-class mixins are applied transitively. That means the per-class
-mixin A of a per-class mixin B is also applied for an object in in B's
+mixin A of a per-class mixin B is also applied for an objectin B's
scope. This is exactly the same as how superclasses are applied for
instances. Consider the following example</p>
@@ -3244,7 +3243,7 @@
</CENTER>
</P>
<P>
-Note, that the list of possible actions can be
+Note that the list of possible actions can be
extended by extending the class <tt>::xotcl::Relations</tt>.
</P>
@@ -3257,9 +3256,9 @@
accessible within their scope. But the interceptors are mechanisms,
which cover more then their sole scope. The meaningful usage of the
meta-programming abilities often requires to go further and to get
-information from the caller's and the callee's scope (e.g for
+information from the caller's and the callee's scope (e.g. for
delegation decisions). Therefore, we introduced rich call-stack
-information for the interceptors. Note, that these are also available
+information for the interceptors. Note that these are also available
for ordinary methods, but the "called..." info options return empty
strings.
</P>
@@ -3383,7 +3382,7 @@
</CENTER>
</P>
<p><br></p>
-<P>Note, that three options with the prefix <tt>calling</tt>
+<P>Note that three options with the prefix <tt>calling</tt>
represent the values of <tt>self</tt>, <tt>self proc</tt>, and <tt>self
class</tt> in the scope where the original call was invoked. In the
following section we will show a simple program in which all of the
@@ -4770,7 +4769,7 @@
<H2><A NAME="autonames">Automatic Name Creation</A>
</H2>
The XOTcl <FONT SIZE=2>autoname</FONT>
-instance method provides an simple way to take the task of
+instance method provides a simple way to take the task of
automatically creating names out of the responsibility of the
programmer. The example below shows how to create on each invocation
of method <FONT SIZE=2>new</FONT> an agent with a fresh name
Index: library/xotcl/library/comm/Httpd.xotcl
===================================================================
diff -u -r6b093438fe4e4b2aae05f6662de2346980a0a111 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- library/xotcl/library/comm/Httpd.xotcl (.../Httpd.xotcl) (revision 6b093438fe4e4b2aae05f6662de2346980a0a111)
+++ library/xotcl/library/comm/Httpd.xotcl (.../Httpd.xotcl) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -612,7 +612,7 @@
Httpd::Responder::Wrk instproc respond {} {
my instvar fileName method resourceName hasFormData
[my info parent] instvar respondpatterns
- ### auch das ist ein kandidat fuer eine chain of responsibility
+ ### auch das ist ein Kandidat fuer eine Chain-of responsibility
foreach {pattern action} $respondpatterns {
if {[regexp $pattern "$method $resourceName $hasFormData"]} {
my $action
@@ -752,7 +752,7 @@
# (credentials) ok sind. Hier habe ich probleme auf die sachen,
# die der worker gesendet (bspw. nonce) hat zu kommen. Ich
# weiß, man kann mit [my info children] daran kommen. Aber,
- # was ist, wenn man mehrere Worker hat?
+ # was is, wenn man mehrere Worker hat?
## Fredj, das sollte kein Problem sein: das credentialsNotOk wird
## vom aktuellen worker (respond) aufgerufen. man kann dem *NotOk
Index: library/xotcl/library/lib/trace.xotcl
===================================================================
diff -u -r073177c8b1304443107efeeb0c334e9477346778 -r2352fb1a509bd00ec49c9677798caad6bfec4d71
--- library/xotcl/library/lib/trace.xotcl (.../trace.xotcl) (revision 073177c8b1304443107efeeb0c334e9477346778)
+++ library/xotcl/library/lib/trace.xotcl (.../trace.xotcl) (revision 2352fb1a509bd00ec49c9677798caad6bfec4d71)
@@ -46,7 +46,7 @@
@ Object instproc statFilter {} {
Description {Experimental statistics filter}
}
- @ Object instproc showVars {args "ist of variables"} {
+ @ Object instproc showVars {args "list of variables"} {
Description {Show the values of the specified variables (or of all variables)
of an object on stderr.}
}