isalnum.c from Gdb at Krugle
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/*
FUNCTION
<<isalnum>>---alphanumeric character predicate
INDEX
isalnum
ANSI_SYNOPSIS
#include <ctype.h>
int isalnum(int <[c]>);
TRAD_SYNOPSIS
#include <ctype.h>
int isalnum(<[c]>);
DESCRIPTION
<<isalnum>> is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for alphabetic or
numeric ASCII characters, and <<0>> for other arguments. It is defined
for all integer values.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using `<<#undef isalnum>>'.
RETURNS
<<isalnum>> returns non-zero if <[c]> is a letter (<<a>>--<<z>> or
<<A>>--<<Z>>) or a digit (<<0>>--<<9>>).
PORTABILITY
<<isalnum>> is ANSI C.
No OS subroutines are required.
*/
#include <_ansi.h>
#include <ctype.h>
#undef isalnum
int
_DEFUN(isalnum,(c),int c)
{
return((_ctype_ + 1)[c] & (_U|_L|_N));
}
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