41 lines
1.3 KiB
C
41 lines
1.3 KiB
C
/* Copyright (C) 1991, 1992, 1995 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If
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not, write to the Free Software Foundation, Inc., 675 Mass Ave,
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Cambridge, MA 02139, USA. */
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#include <ansidecl.h>
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#include <math.h>
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#include "ieee754.h"
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/* Return 0 if VALUE is finite or NaN, +1 if it
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is +Infinity, -1 if it is -Infinity. */
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int
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DEFUN(__isinf, (value), double value)
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{
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union ieee754_double u;
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u.d = value;
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/* An IEEE 754 infinity has an exponent with the
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maximum possible value and a zero mantissa. */
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if ((u.ieee.exponent & 0x7ff) == 0x7ff &&
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u.ieee.mantissa0 == 0 && u.ieee.mantissa1 == 0)
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return u.ieee.negative ? -1 : 1;
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return 0;
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}
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weak_alias (__isinf, isinf)
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