w_jn.c

Newlib 嵌入式 C库 标准实现代码

/* @(#)w_jn.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.
 * ====================================================
 */

/*
 * wrapper jn(int n, double x), yn(int n, double x)
 * floating point Bessel's function of the 1st and 2nd kind
 * of order n
 *          
 * Special cases:
 *	y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
 *	y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
 * Note 2. About jn(n,x), yn(n,x)
 *	For n=0, j0(x) is called,
 *	for n=1, j1(x) is called,
 *	for n<x, forward recursion us used starting
 *	from values of j0(x) and j1(x).
 *	for n>x, a continued fraction approximation to
 *	j(n,x)/j(n-1,x) is evaluated and then backward
 *	recursion is used starting from a supposed value
 *	for j(n,x). The resulting value of j(0,x) is
 *	compared with the actual value to correct the
 *	supposed value of j(n,x).
 *
 *	yn(n,x) is similar in all respects, except
 *	that forward recursion is used for all
 *	values of n>1.
 *	
 */

#include "fdlibm.h"
#include <errno.h>

#ifndef _DOUBLE_IS_32BITS

#ifdef __STDC__
	double jn(int n, double x)	/* wrapper jn */
#else
	double jn(n,x)			/* wrapper jn */
	double x; int n;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_jn(n,x);
#else
	double z;
	struct exception exc;
	z = __ieee754_jn(n,x);
	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
	if(fabs(x)>X_TLOSS) {
	    /* jn(|x|>X_TLOSS) */
            exc.type = TLOSS;
            exc.name = "jn";
	    exc.err = 0;
	    exc.arg1 = n;
	    exc.arg2 = x;
            exc.retval = 0.0;
            if (_LIB_VERSION == _POSIX_)
                errno = ERANGE;
            else if (!matherr(&exc)) {
               errno = ERANGE;
            }        
	    if (exc.err != 0)
	       errno = exc.err;
            return exc.retval; 
	} else
	    return z;
#endif
}

#ifdef __STDC__
	double yn(int n, double x)	/* wrapper yn */
#else
	double yn(n,x)			/* wrapper yn */
	double x; int n;
#endif
{
#ifdef _IEEE_LIBM
	return __ieee754_yn(n,x);
#else
	double z;
	struct exception exc;
	z = __ieee754_yn(n,x);
	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
        if(x <= 0.0){
	    /* yn(n,0) = -inf or yn(x<0) = NaN */
#ifndef HUGE_VAL 
#define HUGE_VAL inf
	    double inf = 0.0;

	    SET_HIGH_WORD(inf,0x7ff00000);	/* set inf to infinite */
#endif
	    exc.type = DOMAIN;	/* should be SING for IEEE */
	    exc.name = "yn";
	    exc.err = 0;
	    exc.arg1 = n;
	    exc.arg2 = x;
	    if (_LIB_VERSION == _SVID_)
	        exc.retval = -HUGE;
	    else
	        exc.retval = -HUGE_VAL;
	    if (_LIB_VERSION == _POSIX_)
	        errno = EDOM;
	    else if (!matherr(&exc)) {
	        errno = EDOM;
	    }
	    if (exc.err != 0)
	       errno = exc.err;
            return exc.retval; 
        }
	if(x>X_TLOSS) {
	    /* yn(x>X_TLOSS) */
            exc.type = TLOSS;
            exc.name = "yn";
	    exc.err = 0;
	    exc.arg1 = n;
	    exc.arg2 = x;
            exc.retval = 0.0;
            if (_LIB_VERSION == _POSIX_)
                errno = ERANGE;
            else if (!matherr(&exc)) {
                errno = ERANGE;
            }        
	    if (exc.err != 0)
	       errno = exc.err;
            return exc.retval; 
	} else
	    return z;
#endif
}

#endif /* defined(_DOUBLE_IS_32BITS) */