libquadmath/math/catanq.c

   1 /* Return arc tangent of complex __float128 value.
   2    Copyright (C) 1997, 1998 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 "quadmath-imp.h"
  22
  23
  24 __complex128
  25 catanq (__complex128 x)
  26 {
  27   __complex128 res;
  28   int rcls = fpclassifyq (__real__ x);
  29   int icls = fpclassifyq (__imag__ x);
  30
  31   if (rcls <= QUADFP_INFINITE || icls <= QUADFP_INFINITE)
  32     {
  33       if (rcls == QUADFP_INFINITE)
  34         {
  35           __real__ res = copysignq (M_PI_2q, __real__ x);
  36           __imag__ res = copysignq (0.0, __imag__ x);
  37         }
  38       else if (icls == QUADFP_INFINITE)
  39         {
  40           if (rcls >= QUADFP_ZERO)
  41             __real__ res = copysignq (M_PI_2q, __real__ x);
  42           else
  43             __real__ res = nanq ("");
  44           __imag__ res = copysignq (0.0, __imag__ x);
  45         }
  46       else if (icls == QUADFP_ZERO || icls == QUADFP_INFINITE)
  47         {
  48           __real__ res = nanq ("");
  49           __imag__ res = copysignq (0.0, __imag__ x);
  50         }
  51       else
  52         {
  53           __real__ res = nanq ("");
  54           __imag__ res = nanq ("");
  55         }
  56     }
  57   else if (rcls == QUADFP_ZERO && icls == QUADFP_ZERO)
  58     {
  59       res = x;
  60     }
  61   else
  62     {
  63       __float128 r2, num, den;
  64
  65       r2 = __real__ x * __real__ x;
  66
  67       den = 1 - r2 - __imag__ x * __imag__ x;
  68
  69       __real__ res = 0.5 * atan2q (2.0 * __real__ x, den);
  70
  71       num = __imag__ x + 1.0;
  72       num = r2 + num * num;
  73
  74       den = __imag__ x - 1.0;
  75       den = r2 + den * den;
  76
  77       __imag__ res = 0.25 * logq (num / den);
  78     }
  79
  80   return res;
  81 }