kc3-lang/libquadmath/math/atanhq.c

Branch - branch -master

• Show log

  Commit

• Hash : 4f659ab9
  Author : Thomas de Grivel
  Date : 2025-11-02T19:33:45
  

  initial commit
  

Download

• math/atanhq.c

• /* s_atanhl.c -- long double version of s_atan.c.
   * Conversion to long double by Ulrich Drepper,
   * Cygnus Support, drepper@cygnus.com.
   */
  
  /*
   * ====================================================
   * 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.
   * ====================================================
   */
  
  /* atanhq(x)
   * Method :
   *    1.Reduced x to positive by atanh(-x) = -atanh(x)
   *    2.For x>=0.5
   *                   1              2x                          x
   *	atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
   *                   2             1 - x                      1 - x
   *
   *	For x<0.5
   *	atanhl(x) = 0.5*log1pq(2x+2x*x/(1-x))
   *
   * Special cases:
   *	atanhl(x) is NaN if |x| > 1 with signal;
   *	atanhl(NaN) is that NaN with no signal;
   *	atanhl(+-1) is +-INF with signal.
   *
   */
  
  #include "quadmath-imp.h"
  
  static const __float128 one = 1, huge = 1e4900Q;
  
  static const __float128 zero = 0;
  
  __float128
  atanhq(__float128 x)
  {
  	__float128 t;
  	uint32_t jx, ix;
  	ieee854_float128 u;
  
  	u.value = x;
  	jx = u.words32.w0;
  	ix = jx & 0x7fffffff;
  	u.words32.w0 = ix;
  	if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */
  	  {
  	    if (u.value == one)
  	      return x/zero;
  	    else
  	      return (x-x)/(x-x);
  	  }
  	if(ix<0x3fc60000 && (huge+x)>zero)	/* x < 2^-57 */
  	  {
  	    math_check_force_underflow (x);
  	    return x;
  	  }
  
  	if(ix<0x3ffe0000) {		/* x < 0.5 */
  	    t = u.value+u.value;
  	    t = 0.5*log1pq(t+t*u.value/(one-u.value));
  	} else
  	    t = 0.5*log1pq((u.value+u.value)/(one-u.value));
  	if(jx & 0x80000000) return -t; else return t;
  }
  

Download