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48 lines
1.7 KiB
C
48 lines
1.7 KiB
C
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/* Return quiet nan.
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Copyright (C) 1997 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
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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 not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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/* XXX The ISO C 9X standard mentions a `n-char-sequence' which is provided
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as the argument to this function but I have no clue what this means.
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Perhaps it is a description of the bits set in the mantissa. */
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#include <math.h>
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#ifdef HANDLE_TAGP
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# include <stdlib.h>
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# include <string.h>
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#else
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# include <ieee754.h>
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#endif
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double
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nan (const char *tagp)
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{
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#ifdef HANDLE_TAGP
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/* If we ever should have use of the TAGP parameter we will use the
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strtod function to analyze it. */
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char buf[6 + strlen (tagp)];
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sprintf (buf, "NAN(%s)", tagp);
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return strtod (buf, NULL);
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#else
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static const union ieee754_double nan_value =
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{ ieee: { mantissa1: 0x1, mantissa0: 0x0, exponent: 0x7ff, negative: 0 } };
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return nan_value.d;
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#endif
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}
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