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RedHat 9 (Linux i386) - man page for scope (redhat section n)

scope(n)				    [incr Tcl]					 scope(n)

NAME
       scope - capture the namespace context for a variable

SYNOPSIS
       scope name

DESCRIPTION
       Creates a scoped value for the specified name, which must be a variable name.  If the name
       is an instance variable, then the scope command returns a string of  the  following  form:
       @itcl  object  varName This is recognized in any context as an instance variable belonging
       to object.  So with itcl3.0 and beyond, it is possible to use instance variables  in  con-
       junction  with widgets.	For example, if you have an object with a private variable x, and
       you can use x in conjunction with the -textvariable option of  an  entry  widget.   Before
       itcl3.0, only common variables could be used in this manner.

       If  the	name  is  not an instance variable, then it must be a common variable or a global
       variable.  In that case, the scope command returns the fully qualified name of  the  vari-
       able, e.g., ::foo::bar::x.

       If the name is not recognized as a variable, the scope command returns an error.

       Ordinary  variable  names refer to variables in the global namespace.  A scoped value cap-
       tures a variable name together with its namespace context in a way that allows  it  to  be
       referenced properly later.  It is needed, for example, to wrap up variable names when a Tk
       widget is used within a namespace: namespace foo {
	   private variable mode 1

	   radiobutton .rb1 -text "Mode #1"	    -variable [scope mode] -value 1
	   pack .rb1

	   radiobutton .rb2 -text "Mode #2"	    -variable [scope mode] -value 2
	   pack .rb2 } Radiobuttons .rb1 and .rb2 interact via the variable "mode"  contained  in
       the  namespace  "foo".  The scope command guarantees this by returning the fully qualified
       variable name ::foo::mode.

       You should never use the @itcl syntax directly.	For example, it is a bad  idea	to  write
       code  like  this:  set  {@itcl  ::fred  x} 3 puts "value = ${@itcl ::fred x}" Instead, you
       should always use the scope command to generate the variable name dynamically.  Then,  you
       can pass that name to a widget or to any other bit of code in your program.

KEYWORDS
       code, namespace, variable

itcl											 scope(n)


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