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/* Emulation for ldexpl.
Contributed by Paolo Bonzini
Copyright 2002-2003, 2007-2019 Free Software Foundation, Inc.
This file is part of gnulib.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
#include <config.h>
/* Specification. */
#include <math.h>
#if HAVE_SAME_LONG_DOUBLE_AS_DOUBLE
long double
ldexpl (long double x, int exp)
{
return ldexp (x, exp);
}
#else
# include <float.h>
# include "fpucw.h"
long double
ldexpl (long double x, int exp)
{
long double factor;
int bit;
DECL_LONG_DOUBLE_ROUNDING
BEGIN_LONG_DOUBLE_ROUNDING ();
/* Check for zero, nan and infinity. */
if (!(isnanl (x) || x + x == x))
{
if (exp < 0)
{
exp = -exp;
factor = 0.5L;
}
else
factor = 2.0L;
if (exp > 0)
for (bit = 1;;)
{
/* Invariant: Here bit = 2^i, factor = 2^-2^i or = 2^2^i,
and bit <= exp. */
if (exp & bit)
x *= factor;
bit <<= 1;
if (bit > exp)
break;
factor = factor * factor;
}
}
END_LONG_DOUBLE_ROUNDING ();
return x;
}
#endif
#if 0
int
main (void)
{
long double x;
int y;
for (y = 0; y < 29; y++)
printf ("%5d %.16Lg %.16Lg\n", y, ldexpl (0.8L, y), ldexpl (0.8L, -y) * ldexpl (0.8L, y));
}
#endif
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