Introduction

... general text, maybe partly from slides/paper .... TODO: Maybe we should not refer to ::nx::core here and import instead the "needed" commands into ::nx namespace.

Using XOTcl 2.0 and the Next Scripting Language in the Next Scripting Framework

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 different interfaces and names of builtin methods. Currently, the Next Scripting Framework supports primarily XOTcl 2.0 (highly compatible with XOTcl 1.*) and the Next Scripting Language (XOTcl provides about twice as many predefined builtin methods compared to the Next Scripting Language).

A single Tcl interpreter can host both, XOTcl and the Next Scripting Language at the same time. This makes migration from XOTcl to Next easier. The following example script shows to use in a single script XOTcl and Next:

   namespace eval mypackage {

      package require XOTcl 2.0

      # Import XOTcl into the current namespace
      namespace import -force ::xotcl::*

      # Define a class using XOTcl
      Class C1
      C1 instproc foo {} {puts "hello world"}

      # Import Next into the current namespace
      namespace import -force ::nx::*

      # Define a class using Next
      Class create C2 {
         :method foo {} {puts "hello world"}
      }
   }

"Switching" between XOTcl and Next effectively means the load some packages (if needed) and to import either the base classes (Object and Class) of XOTcl or Next into the current namespace.

XOTcl Idioms in the Next Scripting Language

Defining Objects and Classes

XOTclNext Scripting Language
Class ClassName Class create ClassName
Object ObjectName Object create ObjectName
::xotcl::Class ClassName ::nx::Class create ClassName
::xotcl::Object ObjectName ::nx::Object create ObjectName

Defining Methods

Scripted Methods Defined in the Init-block of a Class/Object or with Separate Calls

XOTclNext Scripting Language
Class C
C instproc foo args {...}
C proc bar args {...}
# Define method and object method
# in the init-block of a class


Class create C {
  :method foo args {...}
  :object method bar args {...}
}

# Define method and object method with separate calls

Class create C
C method foo args {...}
C object method bar args {...}
Object o
o set x 1
o proc foo args {...}
# Define object method and set instance variable
# in the init-block of an object


Object create o {
  set :x 1
  :method foo args {...}
}

# Define object method and set instance variable
# with separate commands


Object create o
o eval {set :x 1}
o method foo args {...}

Define Different Kinds of Methods

XOTclNext Scripting Language
# Methods for defining methods:
#
#     proc
#     instproc
#     forward
#     instforward
#     parametercmd
#     instparametercmd
# Methods for defining methods:
#
#     method
#     forward
#     setter
#     alias
#     attribute
Class C
C instproc foo args {...}
C proc bar args {...}

Object o
o proc baz args {...}
# Define scripted methods

Class create C {
  :method foo args {...}
  :object method bar args {...}
}

Object create o {
  :method baz args {...}
}
Class C
C instforward f1 ...
C forward f2 ...

Object o
o forward f3 ...
# Define forwarder

Class create C {
  :forward f1 ...
  :object forward f2 ...
}

Object create o {
  :forward f3 ...
}
Class C
C instparametercmd p1
C parametercmd p2

Object o
o parametercmd p3
# Define setter and getter methods

Class create C {
  :setter p1 ?value_constraint?
  :object setter p2 ?value_constraint?
}

Object create o {
  :setter p3 ?value_constraint?
}
# Method "alias" not available

# Define method aliases
# (to scripted or non-scripted methods)


Class create C {
  :alias a1 ...
  :object alias a2 ...
}

Object create o {
  :alias a3 ...
}
# Parameters only available at class level

Class C \
   -parameter {
    x
    {y 1}
}
# Define object attributes
# (parameters for initializing objects)


Class create C {
  :attribute x
  :attribute {y 1}
  :object attribute oa1
}

Object create o {
  :attribute oa2
}

Method Modifiers and Method Protection

XOTclNext Scripting Language
# Method modifiers
#
#   "object",
#   "public", and
#   "protected"
#
# are not available.


# Method modifiers orthogonal over all kinds of methods
#
# Method-definition-methods:
#    method, forward, setter, alias, attribute


Class create C {
  :method-definiton-method ...
  :public method-definiton-method ...
  :protected method-definiton-method ...
  :object method-definiton-method ...
  :protected object method-definiton-method ...
  :public object method-definiton-method ...
}

Resolvers

The Next Scripting Framework defines Tcl resolvers for method and variable names to refer to object specific behavior. Withing method bodies these resolver treat variable and function names starting with a colon ":" 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.

Note that the Next resolvers are used in the XOTcl 2.* environment as well.

Invoking Methods

XOTclNext Scripting Language
Class C
C instproc foo args {...}
C instproc bar args {
  my foo 1 2 3 ;# invoke own method
  o baz       ;# invoke other objects method
}
Object o
o proc baz {} {...}
Class create C {
  :method foo args {...}
  :method bar args {
     :foo 1 2 3 ;# invoke own method
     o baz     ;# invoke other objects method
  }
}
Object create o {
  :method baz {} {...}
}

Accessing Own Instance Variables from Method Bodies

XOTclNext Scripting Language
Class C
C instproc foo args {
  # method scoped variable a
  set a 1
  # instance variable b
  my instvar b
  set b 2
  # global variable/namespaced variable c
  set ::c 3
}
Class create C {
  :method foo args {...}
    # method scoped variable a
    set a 1
    # instance variable b
    set :b 2
    # global variable/namespaced variable c
    set ::c 3
  }
}
my set varname value # set own instance variable to a value via resolver
# (prefered and fastest way)


set :newVar value
my instvar newVar
set newVar value
# set own instance variable via variable import

::nx::var import [self] varname
set varname value
set newVar [my set otherVar] # read own instance variable

set newVar [set :otherVar]

set newVar ${:otherVar}
my exists varname # Test existence of own instance variable

info :varname
::nx::var exists [self] varname

Accessing Instance Variables of other Objects

XOTclNext Scripting Language
obj set varname value # set instance variable of object obj to a value via namespace
# resolver (prefered way: define setter method on obj)


obj eval [list set :varname value]
set newVar [obj set otherVar] # read instance variable of object obj via resolver

set newVar [obj eval {set :otherVar}]
obj instvar newVar
set newVar value
# read instance variable of object obj via import

::nx::var import obj newVar
set newVar value
obj exists varname # Test existence of instance variable of object obj

obj eval {info exists :varname}
::nx::var exists obj varname

Object Parameters

Method Parameters

Introspection

List methods defined by objects

XOTclNext Scripting Language
obj info commands ?pattern? obj info methods ?pattern?
obj info parametercmd ?pattern? obj info methods -methodtype setter ?pattern?
obj info procs ?pattern? obj info methods -methodtype scripted ?pattern?
n.a. obj info methods -methodtype alias ?pattern?
n.a. obj info methods -methodtype forwarder ?pattern?
n.a. obj info methods -methodtype object ?pattern?
n.a. obj info methods -callprotection public|protected ...

List methods defined by classes

cls info instcommands ?pattern? cls info methods ?pattern?
cls info instparametercmd ?pattern? cls info methods -methodtype setter ?pattern?
cls info instprocs ?pattern? cls info methods -methodtype scripted ?pattern?
n.a. cls info methods -methodtype alias ?pattern?
n.a. cls info methods -methodtype forwarder ?pattern?
n.a. cls info methods -methodtype object ?pattern?
n.a. cls info methods -callprotection public|protected ...

List class object specific methods

cls info commands ?pattern? cls object info methods ?pattern?
cls info parametercmd ?pattern? cls object info methods -methodtype setter ?pattern?
cls info procs ?pattern? cls object info methods -methodtype scripted ?pattern?
n.a. cls object info methods -methodtype alias ?pattern?
n.a. cls object info methods -methodtype forwarder ?pattern?
n.a. cls object info methods -methodtype object ?pattern?
n.a. cls object info methods -callprotection public|protected ...

List callable methods

XOTclNext Scripting Language
obj info methods ?pattern? obj info callable ?pattern?
n.a. # list only application specific methods
obj info callable -application

List object/class where some method is defined

XOTclNext Scripting Language
obj procsearch methodName obj info callable -which methodName

List definition of scripted methods defined by classes

XOTclNext Scripting Language
cls info instbody methodName cls info method body methodName
cls info instargs methodName cls info method args methodName
cls info instnonposargs methodName cls info method parameter methodName
cls info instdefault methodName cls info method parameter methodName
cls info instpre methodName cls info method precondition methodName
cls info instpost methodName cls info method postcondition methodName
n.a. cls info method definition methodName

List definition of scripted object specific methods

XOTclNext Scripting Language
obj info body methodName obj info method body methodName
obj info args methodName obj info method args methodName
obj info nonposargs methodName obj info method parameter methodName
obj info default methodName obj info method parameter methodName
obj info pre methodName obj info method precondition methodName
obj info post methodName obj info method postcondition methodName
n.a. obj info method definition methodName

For definition of class object specific methods, use modifier object as shown in examples above.

List filter or mixins

XOTclNext Scripting Language
obj info filter ?-order? ?-guards? ?pattern? obj info filter ?-order? ?-guards? ?pattern?
cls info filter ?-order? ?-guards? ?pattern? cls object info filter ?-order? ?-guards? ?pattern?
cls info instfilter ?-order? ?-guards? ?pattern? cls info filter ?-order? ?-guards? ?pattern?
obj info mixin ?-order? ?-guards? ?pattern? obj info mixin ?-order? ?-guards? ?pattern?
cls info mixin ?-order? ?-guards? ?pattern? cls object info mixin ?-order? ?-guards? ?pattern?
cls info instmixin ?-order? ?-guards? ?pattern? cls info mixin ?-order? ?-guards? ?pattern?

List definition of methods defined by aliases, setters or forwarders

XOTclNext Scripting Language
n.a. obj info method definition methodName
n.a. cls ?object? info method definition methodName

List fully qualified name of method

XOTclNext Scripting Language
n.a. obj info method name methodName
n.a. cls ?object? info method name methodName

List type of a method

XOTclNext Scripting Language
n.a. obj info method type methodName
n.a. cls ?object? info method type methodName

List the scope of mixin classes

XOTclNext Scripting Language
cls info mixinof ?-closure? ?pattern? cls info mixinof -scope object ?-closure? ?pattern?
cls info instmixinof ?-closure? ?pattern? cls info mixinof -scope class ?-closure? ?pattern?
n.a. cls info mixinof -scope all ?-closure? ?pattern?

Check properties of object and classes

XOTclNext Scripting Language
obj istype sometype TODO: ::nx::core::objectproperty and/or ::nx::objectproperty and/or nx::is?

::nx::core::objectproperty obj type sometype


obj info is type sometype
obj ismixin cls ::nx::core::objectproperty obj mixin cls

obj info is mixin cls
obj isclass ?cls? ::nx::core::objectproperty obj|cls class

obj info is class
obj ismetaclass cls ::nx::core::objectproperty obj|cls metaclass
obj info is metaclass
n.a. ::nx::core::objectproperty cls baseclass
cls info is baseclass
obj isobject obj2 ::nx::core::objectproperty obj|obj2 object
obj info is object

Predefined Methods

Dispatch, Aliases, etc.

Assertions

XOTclNext Scripting Language
obj check checkoptions ::nx::core::assertion obj check checkptions
obj info check ::nx::core::assertion obj check
obj invar conditions ::nx::core::assertion obj object-invar conditions
obj info invar ::nx::core::assertion obj object-invar
cls instinvar conditions ::nx::core::assertion cls class-invar conditions
cls info instinvar ::nx::core::assertion cls class-invar
cls invar conditions ::nx::core::assertion cls object-invar conditions
cls info invar ::nx::core::assertion cls object-invar

Method Protection

Incompatibilities between Next Scripting/XOTcl 2.0 and XOTcl 1.*

Resolvers

The tesolvers of the Next Scripting Framework are used as well within XOTcl 2.0. When names starting with single colons are used in XOTcl 1.* scripts, conflicts will arise.

Stronger Checking

The Next Scripting Framework performs stronger checking than XOTcl 1.*. For example, the requiredness of slots in XOTcl was just a comment, while Next enforces it.

Different results

Exit Handlers

The exit hander interface changed from a method of ::xotcl::Object into three Tcl procs in the ::nx::core namespace. Next provides now:

   ::nx::core::setExitHandler script
   ::nx::core::getExitHandler
   ::nx::core::unsetExitHandler

Last modified: Sun Aug 1 17:43:17 CEST 2010