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 1.9 2002/05/26 22:02:01 wiz 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
47 double
jn(int n,double x)48 jn(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
63 double
yn(int n,double x)64 yn(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