aboutsummaryrefslogtreecommitdiff
path: root/math/w_jn.c
blob: 41ec8b32d4ae54c71f17a1060cf4a48421d28052 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
/* @(#)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.
 * ====================================================
 */

#if defined(LIBM_SCCS) && !defined(lint)
static char rcsid[] = "$NetBSD: w_jn.c,v 1.6 1995/05/10 20:49:19 jtc Exp $";
#endif

/*
 * 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 <math.h>
#include <math_private.h>

#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;
	z = __ieee754_jn(n,x);
	if(_LIB_VERSION == _IEEE_ || __isnan(x) ) return z;
	if(fabs(x)>X_TLOSS) {
	    return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */
	} else
	    return z;
#endif
}
#ifdef NO_LONG_DOUBLE
strong_alias (jn, jnl)
#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;
	z = __ieee754_yn(n,x);
	if(_LIB_VERSION == _IEEE_ || __isnan(x) ) return z;
        if(x <= 0.0){
                if(x==0.0)
                    /* d= -one/(x-x); */
                    return __kernel_standard((double)n,x,12);
                else
                    /* d = zero/(x-x); */
                    return __kernel_standard((double)n,x,13);
        }
	if(x>X_TLOSS) {
	    return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */
	} else
	    return z;
#endif
}
#ifdef NO_LONG_DOUBLE
strong_alias (yn, ynl)
#endif