s_signif.c

来自「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」· C语言 代码 · 共 35 行

/* @(#)s_signif.c 5.1 93/09/24 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice 
 * is preserved.
 * ====================================================
 */

/*
 * significand(x) computes just
 * 	scalb(x, (double) -ilogb(x)),
 * for exercising the fraction-part(F) IEEE 754-1985 test vector.
 */

#include "fdlibm.h"

#ifdef __STDC__
	double significand(double x)
#else
	double significand(x)
	double x;
#endif
{
#ifndef _DOUBLE_IS_32BITS
	return __ieee754_scalb(x,(double) -ilogb(x));
#else /* defined (_DOUBLE_IS_32BITS) */
	return (double) significandf ((float) x);
#endif /* defined (_DOUBLE_IS_32BITS) */
}