| The Android Open Source Project | b07e1d9 | 2009-03-03 19:29:30 -0800 | [diff] [blame] | 1 | |
| 2 | /* @(#)w_jn.c 1.3 95/01/18 */ |
| 3 | /* |
| 4 | * ==================================================== |
| 5 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
| 6 | * |
| 7 | * Developed at SunSoft, a Sun Microsystems, Inc. business. |
| 8 | * Permission to use, copy, modify, and distribute this |
| 9 | * software is freely granted, provided that this notice |
| 10 | * is preserved. |
| 11 | * ==================================================== |
| 12 | */ |
| 13 | |
| 14 | /* |
| 15 | * wrapper ieee_jn(int n, double x), ieee_yn(int n, double x) |
| 16 | * floating point Bessel's function of the 1st and 2nd kind |
| 17 | * of order n |
| 18 | * |
| 19 | * Special cases: |
| 20 | * y0(0)=ieee_y1(0)=ieee_yn(n,0) = -inf with division by zero signal; |
| 21 | * y0(-ve)=ieee_y1(-ve)=ieee_yn(n,-ve) are NaN with invalid signal. |
| 22 | * Note 2. About ieee_jn(n,x), ieee_yn(n,x) |
| 23 | * For n=0, ieee_j0(x) is called, |
| 24 | * for n=1, ieee_j1(x) is called, |
| 25 | * for n<x, forward recursion us used starting |
| 26 | * from values of ieee_j0(x) and ieee_j1(x). |
| 27 | * for n>x, a continued fraction approximation to |
| 28 | * j(n,x)/j(n-1,x) is evaluated and then backward |
| 29 | * recursion is used starting from a supposed value |
| 30 | * for j(n,x). The resulting value of j(0,x) is |
| 31 | * compared with the actual value to correct the |
| 32 | * supposed value of j(n,x). |
| 33 | * |
| 34 | * yn(n,x) is similar in all respects, except |
| 35 | * that forward recursion is used for all |
| 36 | * values of n>1. |
| 37 | * |
| 38 | */ |
| 39 | |
| 40 | #include "fdlibm.h" |
| 41 | |
| 42 | #ifdef __STDC__ |
| 43 | double ieee_jn(int n, double x) /* wrapper jn */ |
| 44 | #else |
| 45 | double ieee_jn(n,x) /* wrapper jn */ |
| 46 | double x; int n; |
| 47 | #endif |
| 48 | { |
| 49 | #ifdef _IEEE_LIBM |
| 50 | return __ieee754_jn(n,x); |
| 51 | #else |
| 52 | double z; |
| 53 | z = __ieee754_jn(n,x); |
| 54 | if(_LIB_VERSION == _IEEE_ || ieee_isnan(x) ) return z; |
| 55 | if(ieee_fabs(x)>X_TLOSS) { |
| 56 | return __kernel_standard((double)n,x,38); /* ieee_jn(|x|>X_TLOSS,n) */ |
| 57 | } else |
| 58 | return z; |
| 59 | #endif |
| 60 | } |
| 61 | |
| 62 | #ifdef __STDC__ |
| 63 | double ieee_yn(int n, double x) /* wrapper yn */ |
| 64 | #else |
| 65 | double ieee_yn(n,x) /* wrapper yn */ |
| 66 | double x; int n; |
| 67 | #endif |
| 68 | { |
| 69 | #ifdef _IEEE_LIBM |
| 70 | return __ieee754_yn(n,x); |
| 71 | #else |
| 72 | double z; |
| 73 | z = __ieee754_yn(n,x); |
| 74 | if(_LIB_VERSION == _IEEE_ || ieee_isnan(x) ) return z; |
| 75 | if(x <= 0.0){ |
| 76 | if(x==0.0) |
| 77 | /* d= -one/(x-x); */ |
| 78 | return __kernel_standard((double)n,x,12); |
| 79 | else |
| 80 | /* d = zero/(x-x); */ |
| 81 | return __kernel_standard((double)n,x,13); |
| 82 | } |
| 83 | if(x>X_TLOSS) { |
| 84 | return __kernel_standard((double)n,x,39); /* ieee_yn(x>X_TLOSS,n) */ |
| 85 | } else |
| 86 | return z; |
| 87 | #endif |
| 88 | } |