math/s_clog10.c

   1 /* Compute complex base 10 logarithm.
   2    Copyright (C) 1997, 2011 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 #include <math_private.h>
  24
  25
  26 __complex__ double
  27 __clog10 (__complex__ double x)
  28 {
  29   __complex__ double result;
  30   int rcls = fpclassify (__real__ x);
  31   int icls = fpclassify (__imag__ x);
  32
  33   if (__builtin_expect (rcls == FP_ZERO && icls == FP_ZERO, 0))
  34     {
  35       /* Real and imaginary part are 0.0.  */
  36       __imag__ result = signbit (__real__ x) ? M_PI : 0.0;
  37       __imag__ result = __copysign (__imag__ result, __imag__ x);
  38       /* Yes, the following line raises an exception.  */
  39       __real__ result = -1.0 / fabs (__real__ x);
  40     }
  41   else if (__builtin_expect (rcls != FP_NAN && icls != FP_NAN, 1))
  42     {
  43       /* Neither real nor imaginary part is NaN.  */
  44       __real__ result = __ieee754_log10 (__ieee754_hypot (__real__ x,
  45                                                           __imag__ x));
  46       __imag__ result = M_LOG10E * __ieee754_atan2 (__imag__ x, __real__ x);
  47     }
  48   else
  49     {
  50       __imag__ result = __nan ("");
  51       if (rcls == FP_INFINITE || icls == FP_INFINITE)
  52         /* Real or imaginary part is infinite.  */
  53         __real__ result = HUGE_VAL;
  54       else
  55         __real__ result = __nan ("");
  56     }
  57
  58   return result;
  59 }
  60 weak_alias (__clog10, clog10)
  61 #ifdef NO_LONG_DOUBLE
  62 strong_alias (__clog10, __clog10l)
  63 weak_alias (__clog10, clog10l)
  64 #endif