w_expf.c

来自「Glibc 2.3.2源代码(解压后有100多M)」· C语言 代码 · 共 60 行

/* w_expf.c -- float version of w_exp.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, [e-mail].
 */

/*
 * ====================================================
 * 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.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: w_expf.c,v 1.3 1995/05/10 20:48:53 jtc Exp $";
#endif

/* 
 * wrapper expf(x)
 */

#include "math.h"
#include "math_private.h"

#ifdef __STDC__
static const float
#else
static float
#endif
o_threshold=  8.8721679688e+01,  /* 0x42b17180 */
u_threshold= -1.0397208405e+02;  /* 0xc2cff1b5 */

#ifdef __STDC__
	float __expf(float x)		/* wrapper expf */
#else
	float __expf(x)			/* wrapper expf */
	float x;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_expf(x);
#else
	float z;
	z = __ieee754_expf(x);
	if(_LIB_VERSION == _IEEE_) return z;
	if(__finitef(x)) {
	    if(x>o_threshold)
	        /* exp overflow */
	        return (float)__kernel_standard((double)x,(double)x,106);
	    else if(x<u_threshold)
	        /* exp underflow */
	        return (float)__kernel_standard((double)x,(double)x,107);
	} 
	return z;
#endif
}
weak_alias (__expf, expf)