1
2/* @(#)w_jn.c 1.3 95/01/18 */
3/*
4 * ====================================================
5 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 *
7 * Developed at SunSoft, a Sun Microsystems, Inc. business.
8 * Permission to use, copy, modify, and distribute this
9 * software is freely granted, provided that this notice
10 * is preserved.
11 * ====================================================
12 */
13
14/*
15 * wrapper ieee_jn(int n, double x), ieee_yn(int n, double x)
16 * floating point Bessel's function of the 1st and 2nd kind
17 * of order n
18 *
19 * Special cases:
20 *	y0(0)=ieee_y1(0)=ieee_yn(n,0) = -inf with division by zero signal;
21 *	y0(-ve)=ieee_y1(-ve)=ieee_yn(n,-ve) are NaN with invalid signal.
22 * Note 2. About ieee_jn(n,x), ieee_yn(n,x)
23 *	For n=0, ieee_j0(x) is called,
24 *	for n=1, ieee_j1(x) is called,
25 *	for n<x, forward recursion us used starting
26 *	from values of ieee_j0(x) and ieee_j1(x).
27 *	for n>x, a continued fraction approximation to
28 *	j(n,x)/j(n-1,x) is evaluated and then backward
29 *	recursion is used starting from a supposed value
30 *	for j(n,x). The resulting value of j(0,x) is
31 *	compared with the actual value to correct the
32 *	supposed value of j(n,x).
33 *
34 *	yn(n,x) is similar in all respects, except
35 *	that forward recursion is used for all
36 *	values of n>1.
37 *
38 */
39
40#include "fdlibm.h"
41
42#ifdef __STDC__
43	double ieee_jn(int n, double x)	/* wrapper jn */
44#else
45	double ieee_jn(n,x)			/* wrapper jn */
46	double x; int n;
47#endif
48{
49#ifdef _IEEE_LIBM
50	return __ieee754_jn(n,x);
51#else
52	double z;
53	z = __ieee754_jn(n,x);
54	if(_LIB_VERSION == _IEEE_ || ieee_isnan(x) ) return z;
55	if(ieee_fabs(x)>X_TLOSS) {
56	    return __kernel_standard((double)n,x,38); /* ieee_jn(|x|>X_TLOSS,n) */
57	} else
58	    return z;
59#endif
60}
61
62#ifdef __STDC__
63	double ieee_yn(int n, double x)	/* wrapper yn */
64#else
65	double ieee_yn(n,x)			/* wrapper yn */
66	double x; int n;
67#endif
68{
69#ifdef _IEEE_LIBM
70	return __ieee754_yn(n,x);
71#else
72	double z;
73	z = __ieee754_yn(n,x);
74	if(_LIB_VERSION == _IEEE_ || ieee_isnan(x) ) return z;
75        if(x <= 0.0){
76                if(x==0.0)
77                    /* d= -one/(x-x); */
78                    return __kernel_standard((double)n,x,12);
79                else
80                    /* d = zero/(x-x); */
81                    return __kernel_standard((double)n,x,13);
82        }
83	if(x>X_TLOSS) {
84	    return __kernel_standard((double)n,x,39); /* ieee_yn(x>X_TLOSS,n) */
85	} else
86	    return z;
87#endif
88}
89