sysdeps/ieee754/isnan.c

   1 /* Copyright (C) 1991, 1992, 1995 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library 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 GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <math.h>
  21 #include "ieee754.h"
  22
  23 /* Return nonzero if VALUE is not a number.  */
  24 int
  25 DEFUN(__isnan, (value), double value)
  26 {
  27   union ieee754_double u;
  28
  29   u.d = value;
  30
  31   /* IEEE 754 NaN's have the maximum possible
  32      exponent and a nonzero mantissa.  */
  33   return ((u.ieee.exponent & 0x7ff) == 0x7ff &&
  34           (u.ieee.mantissa0 != 0 || u.ieee.mantissa1 != 0));
  35 }
  36
  37 weak_alias (__isnan, isnan)