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/* @(#)s_frexp.c 5.1 93/09/24 */
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
/*
FUNCTION
<<frexp>>, <<frexpf>>---split floating-point number
INDEX
frexp
INDEX
frexpf
ANSI_SYNOPSIS
#include <math.h>
double frexp(double <[val]>, int *<[exp]>);
float frexpf(float <[val]>, int *<[exp]>);
TRAD_SYNOPSIS
#include <math.h>
double frexp(<[val]>, <[exp]>)
double <[val]>;
int *<[exp]>;
float frexpf(<[val]>, <[exp]>)
float <[val]>;
int *<[exp]>;
DESCRIPTION
All nonzero, normal numbers can be described as <[m]> * 2**<[p]>.
<<frexp>> represents the double <[val]> as a mantissa <[m]>
and a power of two <[p]>. The resulting mantissa will always
be greater than or equal to <<0.5>>, and less than <<1.0>> (as
long as <[val]> is nonzero). The power of two will be stored
in <<*>><[exp]>.
@ifnottex
<[m]> and <[p]> are calculated so that
<[val]> is <[m]> times <<2>> to the power <[p]>.
@end ifnottex
@tex
<[m]> and <[p]> are calculated so that
$ val = m \times 2^p $.
@end tex
<<frexpf>> is identical, other than taking and returning
floats rather than doubles.
RETURNS
<<frexp>> returns the mantissa <[m]>. If <[val]> is <<0>>, infinity,
or Nan, <<frexp>> will set <<*>><[exp]> to <<0>> and return <[val]>.
PORTABILITY
<<frexp>> is ANSI.
<<frexpf>> is an extension.
*/
/*
* for non-zero x
* x = frexp(arg,&exp);
* return a double fp quantity x such that 0.5 <= |x| <1.0
* and the corresponding binary exponent "exp". That is
* arg = x*2^exp.
* If arg is inf, 0.0, or NaN, then frexp(arg,&exp) returns arg
* with *exp=0.
*/
#include "fdlibm.h"
#ifndef _DOUBLE_IS_32BITS
#ifdef __STDC__
static const double
#else
static double
#endif
two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
#ifdef __STDC__
double frexp(double x, int *eptr)
#else
double frexp(x, eptr)
double x; int *eptr;
#endif
{
__int32_t hx, ix, lx;
EXTRACT_WORDS(hx,lx,x);
ix = 0x7fffffff&hx;
*eptr = 0;
if(ix>=0x7ff00000||((ix|lx)==0)) return x; /* 0,inf,nan */
if (ix<0x00100000) { /* subnormal */
x *= two54;
GET_HIGH_WORD(hx,x);
ix = hx&0x7fffffff;
*eptr = -54;
}
*eptr += (ix>>20)-1022;
hx = (hx&0x800fffff)|0x3fe00000;
SET_HIGH_WORD(x,hx);
return x;
}
#endif /* _DOUBLE_IS_32BITS */
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