1 

     2 /*

     3  * Copyright (c) 1998, 2001, Oracle and/or its affiliates. All rights reserved.

     4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     5  *

     6  * This code is free software; you can redistribute it and/or modify it

     7  * under the terms of the GNU General Public License version 2 only, as

     8  * published by the Free Software Foundation.  Oracle designates this

     9  * particular file as subject to the "Classpath" exception as provided

    10  * by Oracle in the LICENSE file that accompanied this code.

    11  *

    12  * This code is distributed in the hope that it will be useful, but WITHOUT

    13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    14  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    15  * version 2 for more details (a copy is included in the LICENSE file that

    16  * accompanied this code).

    17  *

    18  * You should have received a copy of the GNU General Public License version

    19  * 2 along with this work; if not, write to the Free Software Foundation,

    20  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    21  *

    22  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    23  * or visit www.oracle.com if you need additional information or have any

    24  * questions.

    25  */

    26 

    27 /*

    28  * wrapper jn(int n, double x), yn(int n, double x)

    29  * floating point Bessel's function of the 1st and 2nd kind

    30  * of order n

    31  *

    32  * Special cases:

    33  *      y0(0)=y1(0)=yn(n,0) = -inf with division by zero signal;

    34  *      y0(-ve)=y1(-ve)=yn(n,-ve) are NaN with invalid signal.

    35  * Note 2. About jn(n,x), yn(n,x)

    36  *      For n=0, j0(x) is called,

    37  *      for n=1, j1(x) is called,

    38  *      for n<x, forward recursion us used starting

    39  *      from values of j0(x) and j1(x).

    40  *      for n>x, a continued fraction approximation to

    41  *      j(n,x)/j(n-1,x) is evaluated and then backward

    42  *      recursion is used starting from a supposed value

    43  *      for j(n,x). The resulting value of j(0,x) is

    44  *      compared with the actual value to correct the

    45  *      supposed value of j(n,x).

    46  *

    47  *      yn(n,x) is similar in all respects, except

    48  *      that forward recursion is used for all

    49  *      values of n>1.

    50  *

    51  */

    52 

    53 #include "fdlibm.h"

    54 

    55 #ifdef __STDC__

    56         double jn(int n, double x)      /* wrapper jn */

    57 #else

    58         double jn(n,x)                  /* wrapper jn */

    59         double x; int n;

    60 #endif

    61 {

    62 #ifdef _IEEE_LIBM

    63         return __ieee754_jn(n,x);

    64 #else

    65         double z;

    66         z = __ieee754_jn(n,x);

    67         if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;

    68         if(fabs(x)>X_TLOSS) {

    69             return __kernel_standard((double)n,x,38); /* jn(|x|>X_TLOSS,n) */

    70         } else

    71             return z;

    72 #endif

    73 }

    74 

    75 #ifdef __STDC__

    76         double yn(int n, double x)      /* wrapper yn */

    77 #else

    78         double yn(n,x)                  /* wrapper yn */

    79         double x; int n;

    80 #endif

    81 {

    82 #ifdef _IEEE_LIBM

    83         return __ieee754_yn(n,x);

    84 #else

    85         double z;

    86         z = __ieee754_yn(n,x);

    87         if(_LIB_VERSION == _IEEE_ || isnan(x) ) return z;

    88         if(x <= 0.0){

    89                 if(x==0.0)

    90                     /* d= -one/(x-x); */

    91                     return __kernel_standard((double)n,x,12);

    92                 else

    93                     /* d = zero/(x-x); */

    94                     return __kernel_standard((double)n,x,13);

    95         }

    96         if(x>X_TLOSS) {

    97             return __kernel_standard((double)n,x,39); /* yn(x>X_TLOSS,n) */

    98         } else

    99             return z;

   100 #endif

   101 }