islower.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/*
FUNCTION
<<islower>>---lower-case character predicate

INDEX
islower

ANSI_SYNOPSIS
#include <ctype.h>
int islower(int <[c]>);

TRAD_SYNOPSIS
#include <ctype.h>
int islower(<[c]>);

DESCRIPTION
<<islower>> is a macro which classifies ASCII integer values by table
lookup.  It is a predicate returning non-zero for minuscules
(lower-case alphabetic characters), 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 islower>>'.

RETURNS
<<islower>> returns non-zero if <[c]> is a lower case letter (<<a>>--<<z>>).

PORTABILITY
<<islower>> is ANSI C.

No supporting OS subroutines are required.
*/
#include <_ansi.h>
#include <ctype.h>

#undef islower
int
_DEFUN(islower,(c),int c)
{
	return((_ctype_ + 1)[c] & _L);
}