/* @(#)w_jn.c 1.3 95/01/18 */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunSoft, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ /* * 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 nx, 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 "fdlibm.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 }