'\"
'\" 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.
'\"
'\" RCS: $Id: scope.n,v 1.2 1999/01/27 18:56:04 jingham Exp $
'\"
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\"	Start paragraph describing an argument to a library procedure.
'\"	type is type of argument (int, etc.), in/out is either "in", "out",
'\"	or "in/out" to describe whether procedure reads or modifies arg,
'\"	and indent is equivalent to second arg of .IP (shouldn't ever be
'\"	needed;  use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\"	Give maximum sizes of arguments for setting tab stops.  Type and
'\"	name are examples of largest possible arguments that will be passed
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'\"
'\" .BS
'\"	Start box enclosure.  From here until next .BE, everything will be
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'\"
'\" .BE
'\"	End of box enclosure.
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'\"	Begin code excerpt.
'\"
'\" .CE
'\"	End code excerpt.
'\"
'\" .VS ?version? ?br?
'\"	Begin vertical sidebar, for use in marking newly-changed parts
'\"	of man pages.  The first argument is ignored and used for recording
'\"	the version when the .VS was added, so that the sidebars can be
'\"	found and removed when they reach a certain age.  If another argument
'\"	is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\"	End of vertical sidebar.
'\"
'\" .DS
'\"	Begin an indented unfilled display.
'\"
'\" .DE
'\"	End of indented unfilled display.
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'\" .SO
'\"	Start of list of standard options for a Tk widget.  The
'\"	options follow on successive lines, in four 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.
'\"
'\" .UL arg1 arg2
'\"	Print arg1 underlined, then print arg2 normally.
'\"
'\" SCCS: @(#) man.macros 1.9 97/08/22 18:50:59
'\"
'\"	# 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 \{\
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\&\\$1	\\fI\\$2\\fP
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\&\\fI\\$1\\fP
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..
'\"	# define tabbing values for .AP
.de AS
.nr )A 10n
.if !"\\$1"" .nr )A \\w'\\$1'u+3n
.nr )B \\n()Au+15n
.\"
.if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n
.nr )C \\n()Bu+\\w'(in/out)'u+2n
..
.AS Tcl_Interp Tcl_CreateInterp in/out
'\"	# BS - start boxed text
'\"	# ^y = starting y location
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.br
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.if n .ti 0
.if n \l'\\n(.lu\(ul'
.if n .fi
..
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.de BE
.nf
.ti 0
.mk ^t
.ie n \l'\\n(^lu\(ul'
.el \{\
.\"	Draw four-sided box normally, but don't draw top of
.\"	box if the box started on an earlier page.
.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'
.\}
.\}
.fi
.br
.nr ^b 0
..
'\"	# VS - start vertical sidebar
'\"	# ^Y = starting y location
'\"	# ^v = 1 (for troff;  for nroff this doesn't matter)
.de VS
.if !"\\$2"" .br
.mk ^Y
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.el .nr ^v 1u
..
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..
'\"	# Special macro to handle page bottom:  finish off current
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'\"	# page bottom macro.
.de ^B
.ev 2
'ti 0
'nf
.mk ^t
.if \\n(^b \{\
.\"	Draw three-sided box if this is the box's first page,
.\"	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
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..
'\"	# DS - begin display
.de DS
.RS
.nf
.sp
..
'\"	# DE - end display
.de DE
.fi
.RE
.sp
..
'\"	# SO - start of list of standard options
.de SO
.SH "STANDARD OPTIONS"
.LP
.nf
.ta 4c 8c 12c
.ft B
..
'\"	# SE - end of list of standard options
.de SE
.fi
.ft R
.LP
See the \\fBoptions\\fR 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
..
'\"	# CS - begin code excerpt
.de CS
.RS
.nf
.ta .25i .5i .75i 1i
..
'\"	# CE - end code excerpt
.de CE
.fi
.RE
..
.de UL
\\$1\l'|0\(ul'\\$2
..
.TH scope n "" Tcl "[incr\ Tcl]"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
scope \- capture the namespace context for a variable
.SH SYNOPSIS
\fBscope \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 string of the following form:
.CS
@itcl \fIobject varName\fP
.CE
This is recognized in any context as an instance variable belonging
to \fIobject\fR.  So with itcl3.0 and beyond, it is 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 use the \fC@itcl\fR syntax directly.  For example,
it is a bad idea to write code like this:
.CS
set {@itcl ::fred x} 3
puts "value = ${@itcl ::fred x}"
.CE
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
