isdigit.c from Gdb at Krugle
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/*
FUNCTION
<<isdigit>>---decimal digit predicate
INDEX
isdigit
ANSI_SYNOPSIS
#include <ctype.h>
int isdigit(int <[c]>);
TRAD_SYNOPSIS
#include <ctype.h>
int isdigit(<[c]>);
DESCRIPTION
<<isdigit>> is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for decimal digits, and 0 for
other characters. It is defined only when <<isascii>>(<[c]>) is true
or <[c]> is EOF.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using `<<#undef isdigit>>'.
RETURNS
<<isdigit>> returns non-zero if <[c]> is a decimal digit (<<0>>--<<9>>).
PORTABILITY
<<isdigit>> is ANSI C.
No supporting OS subroutines are required.
*/
#include <_ansi.h>
#include <ctype.h>
#undef isdigit
int
_DEFUN(isdigit,(c),int c)
{
return((_ctype_ + 1)[c] & _N);
}
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