NAME

       code - capture the namespace context for a code fragment

SYNOPSIS

       itcl::code ?-namespace name? command ?arg arg ...?
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DESCRIPTION

       Creates  a  scoped value for the specified command and its associated arg arguments.  A scoped value is a
       list with three elements:  the "@scope" keyword, a namespace context, and a value string.   For  example,
       the command
              namespace foo {
                  code puts "Hello World!"
              }
       produces the scoped value:
              @scope ::foo {puts {Hello World!}}
       Note  that the code command captures the current namespace context.  If the -namespace flag is specified,
       then the current context is ignored, and the name string is used as the namespace context.

       Extensions like Tk execute ordinary code fragments in the global namespace.  A scoped  value  captures  a
       code  fragment together with its namespace context in a way that allows it to be executed properly later.
       It is needed, for example, to wrap up code fragments when a Tk widget is used within a namespace:
              namespace foo {
                  private proc report {mesg} {
                      puts "click: $mesg"
                  }

                  button .b1 -text "Push Me"         -command [code report "Hello World!"]
                  pack .b1
              }
       The code fragment associated with button .b1  only  makes  sense  in  the  context  of  namespace  "foo".
       Furthermore, the "report" procedure is private, and can only be accessed within that namespace.  The code
       command wraps up the code fragment in a way that allows it to be executed properly  when  the  button  is
       pressed.

       Also, note that the code command preserves the integrity of arguments on the command line.  This makes it
       a natural replacement for the list command, which is often used to format Tcl code fragments.   In  other
       words, instead of using the list command like this:
              after 1000 [list puts "Hello $name!"]
       use the code command like this:
              after 1000 [code puts "Hello $name!"]
       This not only formats the command correctly, but also captures its namespace context.

       Scoped  commands  can  be  invoked  like  ordinary code fragments, with or without the eval command.  For
       example, the following statements work properly:
              set cmd {@scope ::foo .b1}
              $cmd configure -background red

              set opts {-bg blue -fg white}
              eval $cmd configure $opts
       Note that scoped commands by-pass the usual protection mechanisms; the command:
              @scope ::foo {report {Hello World!}}
       can be used to access the "foo::report" proc from any namespace context, even though it is private.

KEYWORDS

       scope, callback, namespace, public, protected, private