math/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 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 __clog (__complex__ double x)
  29 {
  30   __complex__ double result;
  31   int rcls = fpclassify (__real__ x);
  32   int icls = fpclassify (__imag__ x);
  33
  34   if (rcls == FP_ZERO && icls == FP_ZERO)
  35     {
  36       /* Real and imaginary part are 0.0.  */
  37       __imag__ result = signbit (__real__ x) ? M_PI : 0.0;
  38       __imag__ result = __copysign (__imag__ result, __imag__ x);
  39       /* Yes, the following line raises an exception.  */
  40       __real__ result = -1.0 / fabs (__real__ x);
  41     }
  42   else if (rcls != FP_NAN && icls != FP_NAN)
  43     {
  44       /* Neither real nor imaginary part is NaN.  */
  45       __real__ result = __ieee754_log (__ieee754_hypot (__real__ x,
  46                                                         __imag__ x));
  47       __imag__ result = __ieee754_atan2 (__imag__ x, __real__ x);
  48     }
  49   else
  50     {
  51       __imag__ result = __nan ("");
  52       if (rcls == FP_INFINITE || icls == FP_INFINITE)
  53         /* Real or imaginary part is infinite.  */
  54         __real__ result = HUGE_VAL;
  55       else
  56         __real__ result = __nan ("");
  57     }
  58
  59   return result;
  60 }
  61 weak_alias (__clog, clog)
  62 #ifdef NO_LONG_DOUBLE
  63 strong_alias (__clog, __clogl)
  64 weak_alias (__clog, clogl)
  65 #endif