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/******************************** -*- C -*- ****************************
*
* Emulation for frexpl
*
*
***********************************************************************/
/***********************************************************************
*
* Copyright 2002, 2006 Free Software Foundation, Inc.
* Written by Paolo Bonzini.
*
* This file is part of GNU Smalltalk.
*
* GNU Smalltalk 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.
*
* Linking GNU Smalltalk statically or dynamically with other modules is
* making a combined work based on GNU Smalltalk. Thus, the terms and
* conditions of the GNU General Public License cover the whole
* combination.
*
* In addition, as a special exception, the Free Software Foundation
* give you permission to combine GNU Smalltalk with free software
* programs or libraries that are released under the GNU LGPL and with
* independent programs running under the GNU Smalltalk virtual machine.
*
* You may copy and distribute such a system following the terms of the
* GNU GPL for GNU Smalltalk and the licenses of the other code
* concerned, provided that you include the source code of that other
* code when and as the GNU GPL requires distribution of source code.
*
* Note that people who make modified versions of GNU Smalltalk are not
* obligated to grant this special exception for their modified
* versions; it is their choice whether to do so. The GNU General
* Public License gives permission to release a modified version without
* this exception; this exception also makes it possible to release a
* modified version which carries forward this exception.
*
* GNU Smalltalk 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
* GNU Smalltalk; see the file COPYING. If not, write to the Free Software
* Foundation, 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()
{
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