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/* Emulation for frexpl.
Contributed by Paolo Bonzini
Copyright 2002, 2003 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 2, 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, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <float.h>
#include <math.h>
#include "mathl.h"
/* Binary search. Quite inefficient but portable. */
long double
frexpl(long double x, int *exp)
{
long double exponents[20], *next;
int exponent, bit;
/* Check for zero, nan and infinity. */
if (x != x || x + x == x )
{
*exp = 0;
return x;
}
if (x < 0)
return -frexpl(-x, exp);
exponent = 0;
if (x > 1.0)
{
for (next = exponents, exponents[0] = 2.0L, bit = 1;
*next <= x + x;
bit <<= 1, next[1] = next[0] * next[0], next++);
for (; next >= exponents; bit >>= 1, next--)
if (x + x >= *next)
{
x /= *next;
exponent |= bit;
}
}
else if (x < 0.5)
{
for (next = exponents, exponents[0] = 0.5L, bit = 1;
*next > x;
bit <<= 1, next[1] = next[0] * next[0], next++);
for (; next >= exponents; bit >>= 1, next--)
if (x < *next)
{
x /= *next;
exponent |= bit;
}
exponent = -exponent;
}
*exp = exponent;
return x;
}
#if 0
int
main (void)
{
long double x;
int y;
x = frexpl(0.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(1.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(-1.0L / 0.0L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.5L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.75L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(3.6L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(17.8L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(8.0L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.3L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.49L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.049L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.0245L, &y); printf ("%.6Lg %d\n", x, y);
x = frexpl(0.0625L, &y); printf ("%.6Lg %d\n", x, y);
}
#endif
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