code(n) 							    [incr Tcl]								   code(n)

NAME

       code - capture the namespace context for a code fragment

SYNOPSIS

       code ?-namespace name? command ?arg arg ...?

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  cur-
       rent  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  cor-
       rectly, 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

itcl									3.0								   code(n)