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markom |
'\"
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'\" Copyright (c) 1990 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" RCS: @(#) $Id: GetUid.3,v 1.1.1.1 2002-01-16 10:25:48 markom Exp $
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'\"
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.so man.macros
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.TH Tk_GetUid 3 "" Tk "Tk Library Procedures"
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.BS
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.SH NAME
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Tk_GetUid, Tk_Uid \- convert from string to unique identifier
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.SH SYNOPSIS
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.nf
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\fB#include \fR
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.sp
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\fB#typedef char *Tk_Uid\fR
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.sp
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Tk_Uid
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\fBTk_GetUid\fR(\fIstring\fR)
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.SH ARGUMENTS
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.AP char *string in
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String for which the corresponding unique identifier is
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desired.
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.BE
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.SH DESCRIPTION
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.PP
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\fBTk_GetUid\fR returns the unique identifier corresponding
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to \fIstring\fR.
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Unique identifiers are similar to atoms in Lisp, and are used
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in Tk to speed up comparisons and
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searches. A unique identifier (type Tk_Uid) is a string pointer
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and may be used anywhere that a variable of type ``char *''
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could be used. However, there is guaranteed to be exactly
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one unique identifier for any given string value. If \fBTk_GetUid\fR
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is called twice, once with string \fIa\fR and once with string
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\fIb\fR, and if \fIa\fR and \fIb\fR have the same string value
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(strcmp(a, b) == 0), then \fBTk_GetUid\fR will return exactly
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the same Tk_Uid value for each call (Tk_GetUid(a) == Tk_GetUid(b)).
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This means that variables of type
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Tk_Uid may be compared directly (x == y) without having to call
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\fBstrcmp\fR.
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In addition, the return value from \fBTk_GetUid\fR will have the
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same string value as its argument (strcmp(Tk_GetUid(a), a) == 0).
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.SH KEYWORDS
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atom, unique identifier
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