w_y0.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 51 行

/* from: @(#)w_j0.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.
 * ====================================================
 */

#ifndef lint
static char rcsid[] = "$Id: w_y0.c,v 1.2 1997/02/22 15:12:36 peter Exp $";
#endif

/*
 * wrapper y0(double x)
 */

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

#ifdef __STDC__
	double y0(double x)		/* wrapper y0 */
#else
	double y0(x)			/* wrapper y0 */
	double x;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_y0(x);
#else
	double z;
	z = __ieee754_y0(x);
	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
        if(x <= 0.0){
                if(x==0.0)
                    /* d= -one/(x-x); */
                    return __kernel_standard(x,x,8);
                else
                    /* d = zero/(x-x); */
                    return __kernel_standard(x,x,9);
        }
	if(x>X_TLOSS) {
	        return __kernel_standard(x,x,35); /* y0(x>X_TLOSS) */
	} else
	    return z;
#endif
}