lib/log.c

   1 /* Logarithm.
   2    Copyright (C) 2012-2019 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <math.h>
  21
  22 double
  23 log (double x)
  24 #undef log
  25 {
  26   if (x <= 0.0)
  27     {
  28       /* Work around the OSF/1 5.1 bug.  */
  29       if (x == 0.0)
  30         /* Return -Infinity.  */
  31         return -1.0 / 0.0;
  32       /* Work around the NetBSD 5.1, Solaris 11.0 bug.  */
  33       else /* x < 0.0 */
  34         /* Return NaN.  */
  35         return 0.0 / 0.0;
  36     }
  37   return log (x);
  38 }