sysdeps/libm-ieee754/s_clog.c

   1 /* Compute complex natural logarithm.
   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 Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    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    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  18    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include <complex.h>
  22 #include <math.h>
  23
  24 #include "math_private.h"
  25
  26
  27 __complex__ double
  28 __clog (__complex__ double x)
  29 {
  30   __complex__ double result;
  31
  32   if (__real__ x == 0.0 && __imag__ x == 0.0)
  33     {
  34       __imag__ result = signbit (__real__ x) ? M_PI : 0.0;
  35       if (signbit (__imag__ x))
  36         __imag__ result = __copysign (__imag__ result, -1.0);
  37       /* Yes, the following line raises an exception.  */
  38       __real__ result = -1.0 / fabs (__real__ x);
  39     }
  40   else if (!__isnan (__real__ x) && !__isnan (__imag__ x))
  41     {
  42       __real__ result = __ieee754_log (__ieee754_hypot (__real__ x,
  43                                                         __imag__ x));
  44       __imag__ result = __ieee754_atan2 (__imag__ x, __real__ x);
  45     }
  46   else
  47     {
  48       __imag__ result = __nan ("");
  49       if (__isinf (__real__ x) || __isinf (__imag__ x))
  50         __real__ result = HUGE_VAL;
  51       else
  52         __real__ result = __nan ("");
  53     }
  54
  55   return result;
  56 }
  57 weak_alias (__clog, clog)
  58 #ifdef NO_LONG_DOUBLE
  59 strong_alias (__clog, __clogl)
  60 weak_alias (__clog, clogl)
  61 #endif