1/* @(#)w_jn.c 5.1 93/09/24 */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
9 * is preserved.
10 * ====================================================
11 */
12
13#include <sys/cdefs.h>
14#if defined(LIBM_SCCS) && !defined(lint)
15__RCSID("$NetBSD: w_jn.c,v 1.8 1999/07/02 15:37:44 simonb Exp $");
16#endif
17
18/*
19 * wrapper jn(int n, double x), yn(int n, double x)
20 * floating point Bessel's function of the 1st and 2nd kind
21 * of order n
22 *
23 * Special cases:
24 *	y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;
25 *	y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.
26 * Note 2. About jn(n,x), yn(n,x)
27 *	For n=0, j0(x) is called,
28 *	for n=1, j1(x) is called,
29 *	for n<x, forward recursion us used starting
30 *	from values of j0(x) and j1(x).
31 *	for n>x, a continued fraction approximation to
32 *	j(n,x)/j(n-1,x) is evaluated and then backward
33 *	recursion is used starting from a supposed value
34 *	for j(n,x). The resulting value of j(0,x) is
35 *	compared with the actual value to correct the
36 *	supposed value of j(n,x).
37 *
38 *	yn(n,x) is similar in all respects, except
39 *	that forward recursion is used for all
40 *	values of n>1.
41 *
42 */
43
44#include "math.h"
45#include "math_private.h"
46
47double
48jn(int n, double x)	/* wrapper jn */
49{
50#ifdef _IEEE_LIBM
51	return __ieee754_jn(n,x);
52#else
53	double z;
54	z = __ieee754_jn(n,x);
55	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
56	if(fabs(x)>X_TLOSS) {
57	    return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */
58	} else
59	    return z;
60#endif
61}
62
63double
64yn(int n, double x)	/* wrapper yn */
65{
66#ifdef _IEEE_LIBM
67	return __ieee754_yn(n,x);
68#else
69	double z;
70	z = __ieee754_yn(n,x);
71	if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;
72        if(x <= 0.0){
73                if(x==0.0)
74                    /* d= -one/(x-x); */
75                    return __kernel_standard((double)n,x,12);
76                else
77                    /* d = zero/(x-x); */
78                    return __kernel_standard((double)n,x,13);
79        }
80	if(x>X_TLOSS) {
81	    return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */
82	} else
83	    return z;
84#endif
85}
86