w_pow.c

来自「This is a resource based on j2me embedde」· C语言 代码 · 共 75 行

/*
 * @(#)w_pow.c	1.9 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program is free software; you can redistribute it and/or  
 * modify it under the terms of the GNU General Public License version  
 * 2 only, as published by the Free Software Foundation.   
 *   
 * This program is distributed in the hope that it will be useful, but  
 * WITHOUT ANY WARRANTY; without even the implied warranty of  
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
 * General Public License version 2 for more details (a copy is  
 * included at /legal/license.txt).   
 *   
 * You should have received a copy of the GNU General Public License  
 * version 2 along with this work; if not, write to the Free Software  
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
 * 02110-1301 USA   
 *   
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
 * Clara, CA 95054 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */


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

#include "fdlibm.h"


#ifdef __STDC__
	double pow(double x, double y)	/* wrapper pow */
#else
	double pow(x,y)			/* wrapper pow */
	double x,y;
#endif
{
#ifdef _IEEE_LIBM
	return  __ieee754_pow(x,y);
#else
	double z;
	z=__ieee754_pow(x,y);
	if(_LIB_VERSION == _IEEE_|| isnan(y)) return z;
	if(isnan(x)) {
	    if(y==0.0)
	        return __kernel_standard(x,y,42); /* pow(NaN,0.0) */
	    else
		return z;
	}
	if(x==0.0){
	    if(y==0.0)
	        return __kernel_standard(x,y,20); /* pow(0.0,0.0) */
	    if(finite(y)&&y<0.0)
	        return __kernel_standard(x,y,23); /* pow(0.0,negative) */
	    return z;
	}
	if(!finite(z)) {
	    if(finite(x)&&finite(y)) {
	        if(isnan(z))
	            return __kernel_standard(x,y,24); /* pow neg**non-int */
	        else
	            return __kernel_standard(x,y,21); /* pow overflow */
	    }
	}
	if(z==0.0&&finite(x)&&finite(y))
	    return __kernel_standard(x,y,22); /* pow underflow */
	return z;
#endif
}