math/s_fdim.c

   1 /* Return positive difference between arguments.
   2    Copyright (C) 1997-2015 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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <math.h>
  22
  23 double
  24 __fdim (double x, double y)
  25 {
  26   int clsx = fpclassify (x);
  27   int clsy = fpclassify (y);
  28
  29   if (clsx == FP_NAN || clsy == FP_NAN)
  30     /* Raise invalid flag for signaling but not quiet NaN.  */
  31     return x - y;
  32
  33   if (x <= y)
  34     return 0.0;
  35
  36   double r = x - y;
  37   if (fpclassify (r) == FP_INFINITE
  38       && clsx != FP_INFINITE && clsy != FP_INFINITE)
  39     __set_errno (ERANGE);
  40
  41   return r;
  42 }
  43 weak_alias (__fdim, fdim)
  44 #ifdef NO_LONG_DOUBLE
  45 strong_alias (__fdim, __fdiml)
  46 weak_alias (__fdim, fdiml)
  47 #endif