89 lines
1.9 KiB
C
89 lines
1.9 KiB
C
/* Emulation for ldexpl.
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Contributed by Paolo Bonzini
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Copyright 2002-2003, 2007-2012 Free Software Foundation, Inc.
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This file is part of gnulib.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#include <config.h>
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/* Specification. */
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#include <math.h>
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#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
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long double
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ldexpl (long double x, int exp)
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{
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return ldexp (x, exp);
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}
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#else
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# include <float.h>
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# include "fpucw.h"
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long double
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ldexpl (long double x, int exp)
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{
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long double factor;
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int bit;
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DECL_LONG_DOUBLE_ROUNDING
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BEGIN_LONG_DOUBLE_ROUNDING ();
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/* Check for zero, nan and infinity. */
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if (!(isnanl (x) || x + x == x))
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{
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if (exp < 0)
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{
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exp = -exp;
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factor = 0.5L;
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}
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else
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factor = 2.0L;
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if (exp > 0)
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for (bit = 1;;)
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{
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/* Invariant: Here bit = 2^i, factor = 2^-2^i or = 2^2^i,
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and bit <= exp. */
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if (exp & bit)
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x *= factor;
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bit <<= 1;
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if (bit > exp)
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break;
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factor = factor * factor;
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}
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}
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END_LONG_DOUBLE_ROUNDING ();
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return x;
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}
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#endif
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#if 0
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int
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main (void)
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{
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long double x;
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int y;
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for (y = 0; y < 29; y++)
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printf ("%5d %.16Lg %.16Lg\n", y, ldexpl (0.8L, y), ldexpl (0.8L, -y) * ldexpl (0.8L, y));
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}
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#endif
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