math/s_ctanh.c

   1 /* Complex hyperbole tangent for double.
   2    Copyright (C) 1997, 2005, 2011 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <complex.h>
  21 #include <fenv.h>
  22 #include <math.h>
  23 #include <math_private.h>
  24
  25
  26 __complex__ double
  27 __ctanh (__complex__ double x)
  28 {
  29   __complex__ double res;
  30
  31   if (__builtin_expect (!isfinite (__real__ x) || !isfinite (__imag__ x), 0))
  32     {
  33       if (__isinf_ns (__real__ x))
  34         {
  35           __real__ res = __copysign (1.0, __real__ x);
  36           __imag__ res = __copysign (0.0, __imag__ x);
  37         }
  38       else if (__imag__ x == 0.0)
  39         {
  40           res = x;
  41         }
  42       else
  43         {
  44           __real__ res = __nan ("");
  45           __imag__ res = __nan ("");
  46
  47           if (__isinf_ns (__imag__ x))
  48             feraiseexcept (FE_INVALID);
  49         }
  50     }
  51   else
  52     {
  53       double sin2ix, cos2ix;
  54       double den;
  55
  56       __sincos (2.0 * __imag__ x, &sin2ix, &cos2ix);
  57
  58       den = (__ieee754_cosh (2.0 * __real__ x) + cos2ix);
  59
  60       if (den == 0.0)
  61         {
  62           __complex__ double ez = __cexp (x);
  63           __complex__ double emz = __cexp (-x);
  64
  65           res = (ez - emz) / (ez + emz);
  66         }
  67       else
  68         {
  69           __real__ res = __ieee754_sinh (2.0 * __real__ x) / den;
  70           __imag__ res = sin2ix / den;
  71         }
  72     }
  73
  74   return res;
  75 }
  76 weak_alias (__ctanh, ctanh)
  77 #ifdef NO_LONG_DOUBLE
  78 strong_alias (__ctanh, __ctanhl)
  79 weak_alias (__ctanh, ctanhl)
  80 #endif