kc3-lang/gnulib/lib/cosl.c

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• Hash : 7b089321
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  Date : 2025-01-01T09:24:36
  

  maint: run 'make update-copyright'
  

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• lib/cosl.c

• /* cos (cosine) function with 'long double' argument.
  
     Copyright (C) 2003-2025 Free Software Foundation, Inc.
  
     This file is free software: you can redistribute it and/or modify
     it under the terms of the GNU Lesser General Public License as
     published by the Free Software Foundation, either version 3 of the
     License, or (at your option) any later version.
  
     This file 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 Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public License
     along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  
  /* s_cosl.c -- long double version of s_sin.c.
   * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
   */
  
  /*
   * ====================================================
   * 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.
   * ====================================================
   */
  
  #include <config.h>
  
  /* Specification.  */
  #include <math.h>
  
  #if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
  
  long double
  cosl (long double x)
  {
    return cos (x);
  }
  
  #else
  
  /* Code based on glibc/sysdeps/ieee754/ldbl-128/s_cosl.c.  */
  
  /* cosl(x)
   * Return cosine function of x.
   *
   * kernel function:
   *      __kernel_sinl           ... sine function on [-pi/4,pi/4]
   *      __kernel_cosl           ... cosine function on [-pi/4,pi/4]
   *      __ieee754_rem_pio2l     ... argument reduction routine
   *
   * Method.
   *      Let S,C and T denote the sin, cos and tan respectively on
   *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
   *      in [-pi/4 , +pi/4], and let n = k mod 4.
   *      We have
   *
   *          n        sin(x)      cos(x)        tan(x)
   *     ----------------------------------------------------------
   *          0          S           C             T
   *          1          C          -S            -1/T
   *          2         -S          -C             T
   *          3         -C           S            -1/T
   *     ----------------------------------------------------------
   *
   * Special cases:
   *      Let trig be any of sin, cos, or tan.
   *      trig(+-INF)  is NaN, with signals;
   *      trig(NaN)    is that NaN;
   *
   * Accuracy:
   *      TRIG(x) returns trig(x) nearly rounded
   */
  
  # include "trigl.h"
  
  long double
  cosl (long double x)
  {
    long double y[2],z=0.0L;
    int n;
  
    /* cosl(NaN) is NaN */
    if (isnanl (x))
      return x;
  
    /* |x| ~< pi/4 */
    if (x >= -0.7853981633974483096156608458198757210492
        && x <= 0.7853981633974483096156608458198757210492)
      return kernel_cosl(x, z);
  
    /* cosl(Inf) is NaN, cosl(0) is 1 */
    else if (x + x == x && x != 0.0)
      return x - x;           /* NaN */
  
    /* argument reduction needed */
    else
      {
        n = ieee754_rem_pio2l (x, y);
        switch (n & 3)
          {
          case 0:
            return  kernel_cosl (y[0], y[1]);
          case 1:
            return -kernel_sinl (y[0], y[1], 1);
          case 2:
            return -kernel_cosl (y[0], y[1]);
          default:
            return  kernel_sinl (y[0], y[1], 1);
          }
      }
  }
  
  #endif
  
  #if 0
  int
  main (void)
  {
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *29));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *30));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *32));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *2/3));
    printf ("%.16Lg\n", cosl (0.7853981633974483096156608458198757210492 *4/3));
  }
  #endif
  

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