math/s_catan.c

   1 /* Return arc tangent of complex 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 __catan (__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 (rcls == FP_INFINITE)
  37         {
  38           __real__ res = __copysign (M_PI_2, __real__ x);
  39           __imag__ res = __copysign (0.0, __imag__ x);
  40         }
  41       else if (icls == FP_INFINITE)
  42         {
  43           if (rcls >= FP_ZERO)
  44             __real__ res = __copysign (M_PI_2, __real__ x);
  45           else
  46             __real__ res = __nan ("");
  47           __imag__ res = __copysign (0.0, __imag__ x);
  48         }
  49       else if (icls == FP_ZERO || icls == FP_INFINITE)
  50         {
  51           __real__ res = __nan ("");
  52           __imag__ res = __copysign (0.0, __imag__ x);
  53         }
  54       else
  55         {
  56           __real__ res = __nan ("");
  57           __imag__ res = __nan ("");
  58         }
  59     }
  60   else if (rcls == FP_ZERO && icls == FP_ZERO)
  61     {
  62       res = x;
  63     }
  64   else
  65     {
  66       double r2, num, den;
  67
  68       r2 = __real__ x * __real__ x;
  69
  70       den = 1 - r2 - __imag__ x * __imag__ x;
  71
  72       __real__ res = 0.5 * __ieee754_atan2 (2.0 * __real__ x, den);
  73
  74       num = __imag__ x + 1.0;
  75       num = r2 + num * num;
  76
  77       den = __imag__ x - 1.0;
  78       den = r2 + den * den;
  79
  80       __imag__ res = 0.25 * __ieee754_log (num / den);
  81     }
  82
  83   return res;
  84 }
  85 weak_alias (__catan, catan)
  86 #ifdef NO_LONG_DOUBLE
  87 strong_alias (__catan, __catanl)
  88 weak_alias (__catan, catanl)
  89 #endif