math/s_catanh.c

   1 /* Return arc hyperbole tangent for double value.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <complex.h>
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26
  27 __complex__ double
  28 __catanh (__complex__ double x)
  29 {
  30   __complex__ double res;
  31   int rcls = fpclassify (__real__ x);
  32   int icls = fpclassify (__imag__ x);
  33
  34   if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
  35     {
  36       if (icls == FP_INFINITE)
  37         {
  38           __real__ res = __copysign (0.0, __real__ x);
  39           __imag__ res = __copysign (M_PI_2, __imag__ x);
  40         }
  41       else if (rcls == FP_INFINITE || rcls == FP_ZERO)
  42         {
  43           __real__ res = __copysign (0.0, __real__ x);
  44           if (icls >= FP_ZERO)
  45             __imag__ res = __copysign (M_PI_2, __imag__ x);
  46           else
  47             __imag__ res = __nan ("");
  48         }
  49       else
  50         {
  51           __real__ res = __nan ("");
  52           __imag__ res = __nan ("");
  53         }
  54     }
  55   else if (rcls == FP_ZERO && icls == FP_ZERO)
  56     {
  57       res = x;
  58     }
  59   else
  60     {
  61       double i2, num, den;
  62
  63       i2 = __imag__ x * __imag__ x;
  64
  65       num = 1.0 + __real__ x;
  66       num = i2 + num * num;
  67
  68       den = 1.0 - __real__ x;
  69       den = i2 + den * den;
  70
  71       __real__ res = 0.25 * (__ieee754_log (num) - __ieee754_log (den));
  72
  73       den = 1 - __real__ x * __real__ x - i2;
  74
  75       __imag__ res = 0.5 * __ieee754_atan2 (2.0 * __imag__ x, den);
  76     }
  77
  78   return res;
  79 }
  80 weak_alias (__catanh, catanh)
  81 #ifdef NO_LONG_DOUBLE
  82 strong_alias (__catanh, __catanhl)
  83 weak_alias (__catanh, catanhl)
  84 #endif