Tk_GetUid(3tk) Tk Library Procedures Tk_GetUid(3tk)
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NAME
Tk_GetUid, Tk_Uid - convert from string to unique identifier
SYNOPSIS
#include <tk.h>
Tk_Uid
Tk_GetUid(string)
ARGUMENTS
char *string (in) String for which the corre-
sponding unique identifier is
desired.
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DESCRIPTION
Tk_GetUid returns the unique identifier corresponding to string.
Unique identifiers are similar to atoms in Lisp, and are used in Tk to
speed up comparisons and searches. A unique identifier (type Tk_Uid)
is a string pointer and may be used anywhere that a variable of type
“char *” could be used. However, there is guaranteed to be exactly one
unique identifier for any given string value. If Tk_GetUid is called
twice, once with string a and once with string b, and if a and b have
the same string value (strcmp(a, b) == 0), then Tk_GetUid will return
exactly the same Tk_Uid value for each call (Tk_GetUid(a) == Tk_Ge-
tUid(b)). This means that variables of type Tk_Uid may be compared di-
rectly (x == y) without having to call strcmp. In addition, the return
value from Tk_GetUid will have the same string value as its argument
(strcmp(Tk_GetUid(a), a) == 0).
KEYWORDS
atom, unique identifier
Tk Tk_GetUid(3tk)
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