w_powf.c

来自「基于组件方式开发操作系统的OSKIT源代码」· C语言 代码 · 共 73 行

/* w_powf.c -- float version of w_pow.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.
 * ====================================================
 */

#ifndef lint
static char rcsid[] = "$\Id: w_powf.c,v 1.2 1995/05/30 05:51:38 rgrimes Exp $";
#endif

/*
 * wrapper powf(x,y) return x**y
 */

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


#ifdef __STDC__
	float powf(float x, float y)	/* wrapper powf */
#else
	float powf(x,y)			/* wrapper powf */
	float x,y;
#endif
{
#ifdef _IEEE_LIBM
	return  __ieee754_powf(x,y);
#else
	float z;
	z=__ieee754_powf(x,y);
	if(_LIB_VERSION == _IEEE_|| isnanf(y)) return z;
	if(isnanf(x)) {
	    if(y==(float)0.0)
	        /* powf(NaN,0.0) */
	        return (float)__kernel_standard((double)x,(double)y,142);
	    else
		return z;
	}
	if(x==(float)0.0){
	    if(y==(float)0.0)
	        /* powf(0.0,0.0) */
	        return (float)__kernel_standard((double)x,(double)y,120);
	    if(finitef(y)&&y<(float)0.0)
	        /* powf(0.0,negative) */
	        return (float)__kernel_standard((double)x,(double)y,123);
	    return z;
	}
	if(!finitef(z)) {
	    if(finitef(x)&&finitef(y)) {
	        if(isnanf(z))
		    /* powf neg**non-int */
	            return (float)__kernel_standard((double)x,(double)y,124);
	        else
		    /* powf overflow */
	            return (float)__kernel_standard((double)x,(double)y,121);
	    }
	}
	if(z==(float)0.0&&finitef(x)&&finitef(y))
	    /* powf underflow */
	    return (float)__kernel_standard((double)x,(double)y,122);
	return z;
#endif
}