math/s_casinh.c

   1 /* Return arc hyperbole sine for double value.
   2    Copyright (C) 1997-2012 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 <math.h>
  22 #include <math_private.h>
  23
  24
  25 __complex__ double
  26 __casinh (__complex__ double x)
  27 {
  28   __complex__ double res;
  29   int rcls = fpclassify (__real__ x);
  30   int icls = fpclassify (__imag__ x);
  31
  32   if (rcls <= FP_INFINITE || icls <= FP_INFINITE)
  33     {
  34       if (icls == FP_INFINITE)
  35         {
  36           __real__ res = __copysign (HUGE_VAL, __real__ x);
  37
  38           if (rcls == FP_NAN)
  39             __imag__ res = __nan ("");
  40           else
  41             __imag__ res = __copysign (rcls >= FP_ZERO ? M_PI_2 : M_PI_4,
  42                                        __imag__ x);
  43         }
  44       else if (rcls <= FP_INFINITE)
  45         {
  46           __real__ res = __real__ x;
  47           if ((rcls == FP_INFINITE && icls >= FP_ZERO)
  48               || (rcls == FP_NAN && icls == FP_ZERO))
  49             __imag__ res = __copysign (0.0, __imag__ x);
  50           else
  51             __imag__ res = __nan ("");
  52         }
  53       else
  54         {
  55           __real__ res = __nan ("");
  56           __imag__ res = __nan ("");
  57         }
  58     }
  59   else if (rcls == FP_ZERO && icls == FP_ZERO)
  60     {
  61       res = x;
  62     }
  63   else
  64     {
  65       __complex__ double y;
  66
  67       __real__ y = (__real__ x - __imag__ x) * (__real__ x + __imag__ x) + 1.0;
  68       __imag__ y = 2.0 * __real__ x * __imag__ x;
  69
  70       y = __csqrt (y);
  71
  72       __real__ y += __real__ x;
  73       __imag__ y += __imag__ x;
  74
  75       res = __clog (y);
  76
  77       /* Ensure zeros have correct sign and results are correct if
  78          very close to branch cuts.  */
  79       __real__ res = __copysign (__real__ res, __real__ x);
  80       __imag__ res = __copysign (__imag__ res, __imag__ x);
  81     }
  82
  83   return res;
  84 }
  85 weak_alias (__casinh, casinh)
  86 #ifdef NO_LONG_DOUBLE
  87 strong_alias (__casinh, __casinhl)
  88 weak_alias (__casinh, casinhl)
  89 #endif