... 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. +
In general, the Next Scripting Language differs from XOTcl in the following +respects: +
+ +
The encapsulation of Next Scripting is weak; a programmer can still + access e.g. other variables via some idioms, but this makes these + accesses implicit and is more typing effort. Through the weak + encapsulation a programmer should be encouraged to implement + methods to provide access to instance variables.
+ +
+ +
+ +
+ +
+ +
+Class create Stack {
+
+ :method init {} {
+ set :things ""
+ }
+
+ :method push {thing} {
+ set :things [linsert ${:things} 0 $thing]
+ return $thing
+ }
+
+ :method pop {} {
+ set top [lindex ${:things} 0]
+ set :things [lrange ${:things} 1 end]
+ return $top
+ }
+}
+
+Figure 1: Stack example in the Next Scripting Language
+ + +
+Class Stack
+
+Stack instproc init {} {
+ my instvar things
+ set things ""
+}
+
+Stack instproc push {thing} {
+ my instvar things
+ set things [linsert $things 0 $thing]
+ return $thing
+}
+
+Stack instproc pop {} {
+ my instvar things
+ set top [lindex $things 0]
+ set things [lrange $things 1 end]
+ return $top
+}
+
+Figure 2: Stack example in XOTcl
+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 +systems can have different different interfaces and names of built-in 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 +Language (XOTcl provides about twice as many predefined built-in methods compared to the Next Scripting Language).
A single Tcl interpreter can host both, XOTcl and the Next @@ -347,7 +430,7 @@ 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 +
Note that the Next resolvers can be used in the XOTcl 2.* environment as well.
In general, the Next Scripting Language favors the access to an +objects's own instance variables over variable accesses of other +objects. On the contrary, in XOTcl, the variable access to own and +other variables are completely symmetric. + +
In Next Scripting, access to local variables are performed via
+primarily via name resolvers, but using the standard tcl commands
+(like e.g. set, incr, append,
+info exists, etc.). In XOTcl, it is common to provide
+same-named methods registered on ::xotcl::Object for such
+purposes. This is one of the reasons, why the Next Scripting Language
+has a much smaller interface (less predefined methods). It is possible
+for an application program to register XOTcl-like methods in the Next
+Scripting Language via the primitives of the Next Scripting Framework.
+
+
| XOTcl | Next Scripting Language |
|---|---|