math/s_ctan.c

   1 /* Complex tangent function 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
  24 #include <math_private.h>
  25
  26
  27 __complex__ double
  28 __ctan (__complex__ double x)
  29 {
  30   __complex__ double res;
  31
  32   if (__builtin_expect (!isfinite (__real__ x) || !isfinite (__imag__ x), 0))
  33     {
  34       if (__isinf_ns (__imag__ x))
  35         {
  36           __real__ res = __copysign (0.0, __real__ x);
  37           __imag__ res = __copysign (1.0, __imag__ x);
  38         }
  39       else if (__real__ x == 0.0)
  40         {
  41           res = x;
  42         }
  43       else
  44         {
  45           __real__ res = __nan ("");
  46           __imag__ res = __nan ("");
  47
  48           if (__isinf_ns (__real__ x))
  49             feraiseexcept (FE_INVALID);
  50         }
  51     }
  52   else
  53     {
  54       double sin2rx, cos2rx;
  55       double den;
  56
  57       __sincos (2.0 * __real__ x, &sin2rx, &cos2rx);
  58
  59       den = cos2rx + __ieee754_cosh (2.0 * __imag__ x);
  60
  61       if (den == 0.0)
  62         {
  63           __complex__ double ez = __cexp (1.0i * x);
  64           __complex__ double emz = __cexp (-1.0i * x);
  65
  66           res = (ez - emz) / (ez + emz) * -1.0i;
  67         }
  68       else
  69         {
  70           __real__ res = sin2rx / den;
  71           __imag__ res = __ieee754_sinh (2.0 * __imag__ x) / den;
  72         }
  73     }
  74
  75   return res;
  76 }
  77 weak_alias (__ctan, ctan)
  78 #ifdef NO_LONG_DOUBLE
  79 strong_alias (__ctan, __ctanl)
  80 weak_alias (__ctan, ctanl)
  81 #endif