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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 __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

}