w_exp.c

来自「This is a resource based on j2me embedde」· C语言 代码 · 共 66 行

/*
 * @(#)w_exp.c	1.11 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 exp(x)
 */

#include "fdlibm.h"

#ifndef _IEEE_LIBM
#ifdef __STDC__
static const double
#else
static double
#endif
o_threshold=  7.09782712893383973096e+02,  /* 0x40862E42, 0xFEFA39EF */
u_threshold= -7.45133219101941108420e+02;  /* 0xc0874910, 0xD52D3051 */
#endif

#ifdef __STDC__
	double exp(double x)		/* wrapper exp */
#else
	double exp(x)			/* wrapper exp */
	double x;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_exp(x);
#else
	double z;
	z = __ieee754_exp(x);
	if(_LIB_VERSION == _IEEE_) return z;
	if(finite(x)) {
	    if(x>o_threshold)
	        return __kernel_standard(x,x,6); /* exp overflow */
	    else if(x<u_threshold)
	        return __kernel_standard(x,x,7); /* exp underflow */
	}
	return z;
#endif
}