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/* @(#)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
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