'\"
'\" Copyright (c) 1993-1998  Lucent Technologies, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH scope 3itcl "" itcl "[incr\ Tcl]"
.\" The -*- nroff -*- definitions below are for supplemental macros used
.\" in Tcl/Tk manual entries.
.\"
.\" .AP type name in/out ?indent?
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.\" .SO ?manpage?
.\"	Start of list of standard options for a Tk widget. The manpage
.\"	argument defines where to look up the standard options; if
.\"	omitted, defaults to "options". The options follow on successive
.\"	lines, in three columns separated by tabs.
.\"
.\" .SE
.\"	End of list of standard options for a Tk widget.
.\"
.\" .OP cmdName dbName dbClass
.\"	Start of description of a specific option.  cmdName gives the
.\"	option's name as specified in the class command, dbName gives
.\"	the option's name in the option database, and dbClass gives
.\"	the option's class in the option database.
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.\" .UL arg1 arg2
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.\"	# Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
.if t .wh -1.3i ^B
.nr ^l \n(.l
.ad b
.\"	# Start an argument description
.de AP
.ie !"\\$4"" .TP \\$4
.el \{\
.   ie !"\\$2"" .TP \\n()Cu
.   el          .TP 15
.\}
.ta \\n()Au \\n()Bu
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\&\\$1 \\fI\\$2\\fP (\\$3)
.\".b
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.br
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\&\\fI\\$1\\fP
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..
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.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
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.if n \l'\\n(.lu\(ul'
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.ie n \l'\\n(^lu\(ul'
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.ie !\\n(^b-1 \{\
\h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
.el \}\
\h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul'
.\}
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.fi
.br
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.\"	draw two sides but no top otherwise.
.ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c
.\}
.if \\n(^v \{\
.nr ^x \\n(^tu+1v-\\n(^Yu
\kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c
.\}
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'fi
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..
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.de DS
.RS
.nf
.sp
..
.\"	# DE - end display
.de DE
.fi
.RE
.sp
..
.\"	# SO - start of list of standard options
.de SO
'ie '\\$1'' .ds So \\fBoptions\\fR
'el .ds So \\fB\\$1\\fR
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 5.5c 11c
.ft B
..
.\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\*(So manual entry for details on the standard options.
..
.\"	# OP - start of full description for a single option
.de OP
.LP
.nf
.ta 4c
Command-Line Name:	\\fB\\$1\\fR
Database Name:	\\fB\\$2\\fR
Database Class:	\\fB\\$3\\fR
.fi
.IP
..
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.RE
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.\"	# UL - underline word
.de UL
\\$1\l'|0\(ul'\\$2
..
.\"	# QW - apply quotation marks to word
.de QW
.ie '\\*(lq'"' ``\\$1''\\$2
.\"" fix emacs highlighting
.el \\*(lq\\$1\\*(rq\\$2
..
.\"	# PQ - apply parens and quotation marks to word
.de PQ
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.\"" fix emacs highlighting
.el (\\*(lq\\$1\\*(rq\\$2)\\$3
..
.\"	# QR - quoted range
.de QR
.ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3
.\"" fix emacs highlighting
.el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3
..
.\"	# MT - "empty" string
.de MT
.QW ""
..
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
itcl::scope \- capture the namespace context for a variable
.SH SYNOPSIS
\fBitcl::scope \fIname\fR
.BE

.SH DESCRIPTION
.PP
Creates a scoped value for the specified \fIname\fR, which must
be a variable name.  If the \fIname\fR is an instance variable,
then the scope command returns a name which will resolve in any
context as an instance variable belonging to \fIobject\fR.  
The precise format of this name is an internal detail to Itcl.
Use of such a scoped value makes it possible to use
instance variables in conjunction with widgets.  For example, if you
have an object with a private variable \fCx\fR, and you can use
\fCx\fR in conjunction with the \fC-textvariable\fR option of an
entry widget.  Before itcl3.0, only common variables could be used
in this manner.
.PP
If the \fIname\fR 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 variable, e.g.,
\fC::foo::bar::x\fR.
.PP
If the \fIname\fR is not recognized as a variable, the scope
command returns an error.
.PP
Ordinary variable names refer to variables in the global namespace.
A scoped value captures 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:
.CS
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
}
.CE
Radiobuttons \fC.rb1\fR and \fC.rb2\fR interact via the variable
"mode" contained in the namespace "foo".  The \fBscope\fR command
guarantees this by returning the fully qualified variable name
\fC::foo::mode\fR.
.PP
You should never attempt to craft your own scoped variable names,
even if you believe you've flawlessly reverse-engineered the encoding.
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.

.SH KEYWORDS
code, namespace, variable