math/s_ctan.c

   1 /* Complex tangent function for double.
   2    Copyright (C) 1997, 2005 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 <fenv.h>
  23 #include <math.h>
  24
  25 #include "math_private.h"
  26
  27
  28 __complex__ double
  29 __ctan (__complex__ double x)
  30 {
  31   __complex__ double res;
  32
  33   if (!isfinite (__real__ x) || !isfinite (__imag__ x))
  34     {
  35       if (__isinf (__imag__ x))
  36         {
  37           __real__ res = __copysign (0.0, __real__ x);
  38           __imag__ res = __copysign (1.0, __imag__ x);
  39         }
  40       else if (__real__ x == 0.0)
  41         {
  42           res = x;
  43         }
  44       else
  45         {
  46           __real__ res = __nan ("");
  47           __imag__ res = __nan ("");
  48
  49 #ifdef FE_INVALID
  50           if (__isinf (__real__ x))
  51             feraiseexcept (FE_INVALID);
  52 #endif
  53         }
  54     }
  55   else
  56     {
  57       double sin2rx, cos2rx;
  58       double den;
  59
  60       __sincos (2.0 * __real__ x, &sin2rx, &cos2rx);
  61
  62       den = cos2rx + __ieee754_cosh (2.0 * __imag__ x);
  63
  64       if (den == 0.0)
  65         {
  66           __complex__ double ez = __cexp (1.0i * x);
  67           __complex__ double emz = __cexp (-1.0i * x);
  68
  69           res = (ez - emz) / (ez + emz) * -1.0i;
  70         }
  71       else
  72         {
  73           __real__ res = sin2rx / den;
  74           __imag__ res = __ieee754_sinh (2.0 * __imag__ x) / den;
  75         }
  76     }
  77
  78   return res;
  79 }
  80 weak_alias (__ctan, ctan)
  81 #ifdef NO_LONG_DOUBLE
  82 strong_alias (__ctan, __ctanl)
  83 weak_alias (__ctan, ctanl)
  84 #endif