w_jn.c

ecos实时嵌入式操作系统

//===========================================================================
//
//      w_jn.c
//
//      Part of the standard mathematical function library
//
//===========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 2 or (at your option) any later version.
//
// eCos is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License along
// with eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
// by itself cause the resulting work to be covered by the GNU General Public
// License. However the source code for this file must still be made available
// in accordance with section (3) of the GNU General Public License.
//
// This exception does not invalidate any other reasons why a work based on
// this file might be covered by the GNU General Public License.
//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//===========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   jlarmour
// Contributors:  jlarmour
// Date:        1998-02-13
// Purpose:     
// Description: 
// Usage:       
//
//####DESCRIPTIONEND####
//
//===========================================================================

// CONFIGURATION

#include <pkgconf/libm.h>   // Configuration header

// Include the Math library?
#ifdef CYGPKG_LIBM     

// Derived from code with the following copyright


/* @(#)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 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 "mathincl/fdlibm.h"

        double jn(int n, double x)      /* wrapper jn */
{
#ifdef CYGSEM_LIBM_COMPAT_IEEE_ONLY
        return __ieee754_jn(n,x);
#else
        double z;
        z = __ieee754_jn(n,x);
        if(cyg_libm_get_compat_mode() == CYGNUM_LIBM_COMPAT_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
}

        double yn(int n, double x)      /* wrapper yn */
{
#ifdef CYGSEM_LIBM_COMPAT_IEEE_ONLY
        return __ieee754_yn(n,x);
#else
        double z;
        z = __ieee754_yn(n,x);
        if(cyg_libm_get_compat_mode() == CYGNUM_LIBM_COMPAT_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
}

#endif // ifdef CYGPKG_LIBM     

// EOF w_jn.c