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/* __gmpfr_ceil_exp2 - returns y >= 2^d
Copyright 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation.
This file is part of the MPFR Library.
The MPFR Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or (at your
option) any later version.
The MPFR Library 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 Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License
along with the MPFR Library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
#include "mpfr-impl.h"
/* returns y >= 2^d, assuming that d <= 1024
for d integer, returns exactly 2^d
*/
double
__gmpfr_ceil_exp2 (double d)
{
long exp;
#if _GMP_IEEE_FLOATS
union ieee_double_extract x;
#else
struct {double d;} x;
#endif
MPFR_ASSERTN(d <= 1024.0);
exp = (long) d;
if (d != (double) exp)
exp++;
/* now exp = ceil(d) */
x.d = 1.0;
#if _GMP_IEEE_FLOATS
x.s.exp = exp <= -1022 ? 1 : 1023 + exp;
#else
if (exp >= 0)
{
while (exp != 0)
{
x.d *= 2.0;
exp--;
}
}
else
{
while (exp != 0)
{
x.d *= (1.0 / 2.0);
exp++;
}
}
#endif
return x.d;
}
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