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01: /* `NAN' constant for IEEE 754 machines.
02:    Copyright (C) 1992,1996,1997,1999,2004,2006 Free Software Foundation, Inc.
03:    This file is part of the GNU C Library.
04: 
05:    The GNU C Library is free software; you can redistribute it and/or
06:    modify it under the terms of the GNU Lesser General Public
07:    License as published by the Free Software Foundation; either
08:    version 2.1 of the License, or (at your option) any later version.
09: 
10:    The GNU C Library is distributed in the hope that it will be useful,
11:    but WITHOUT ANY WARRANTY; without even the implied warranty of
12:    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13:    Lesser General Public License for more details.
14: 
15:    You should have received a copy of the GNU Lesser General Public
16:    License along with the GNU C Library; if not, write to the Free
17:    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
18:    02111-1307 USA.  */
19: 
20: #ifndef _MATH_H
21: # error "Never use <bits/nan.h> directly; include <math.h> instead."
22: #endif
23: 
24: 
25: /* IEEE Not A Number.  */
26: 
27: #if __GNUC_PREREQ(3,3)
28: 
29: # define NAN    (__builtin_nanf (""))
30: 
31: #elif defined __GNUC__
32: 
33: # define NAN \
34:   (__extension__                                                              \
35:    ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
36:     { __l: 0x7fc00000UL }).__d)
37: 
38: #else
39: 
40: # include <endian.h>
41: 
42: # if __BYTE_ORDER == __BIG_ENDIAN
43: #  define __nan_bytes           { 0x7f, 0xc0, 0, 0 }
44: # endif
45: # if __BYTE_ORDER == __LITTLE_ENDIAN
46: #  define __nan_bytes           { 0, 0, 0xc0, 0x7f }
47: # endif
48: 
49: static union { unsigned char __c[4]; float __d; } __nan_union
50:     __attribute_used__ = { __nan_bytes };
51: # define NAN    (__nan_union.__d)
52: 
53: #endif  /* GCC.  */
54: 

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