isalpha.c from Gdb at Krugle
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/*
FUNCTION
<<isalpha>>---alphabetic character predicate
INDEX
isalpha
ANSI_SYNOPSIS
#include <ctype.h>
int isalpha(int <[c]>);
TRAD_SYNOPSIS
#include <ctype.h>
int isalpha(<[c]>);
DESCRIPTION
<<isalpha>> is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero when <[c]> represents an
alphabetic ASCII character, and 0 otherwise. 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 isalpha>>'.
RETURNS
<<isalpha>> returns non-zero if <[c]> is a letter (<<A>>--<<Z>> or
<<a>>--<<z>>).
PORTABILITY
<<isalpha>> is ANSI C.
No supporting OS subroutines are required.
*/
#include <_ansi.h>
#include <ctype.h>
#undef isalpha
int
_DEFUN(isalpha,(c),int c)
{
return((_ctype_ + 1)[c] & (_U|_L));
}
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