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/* @(#)s_scalbn.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
<<scalbn>>, <<scalbnf>>, <<scalbln>>, <<scalblnf>>---scale by power of FLT_RADIX (=2)
INDEX
scalbn
INDEX
scalbnf
INDEX
scalbln
INDEX
scalblnf
SYNOPSIS
#include <math.h>
double scalbn(double <[x]>, int <[n]>);
float scalbnf(float <[x]>, int <[n]>);
double scalbln(double <[x]>, long int <[n]>);
float scalblnf(float <[x]>, long int <[n]>);
DESCRIPTION
The <<scalbn>> and <<scalbln>> functions compute
@ifnottex
<[x]> times FLT_RADIX to the power <[n]>.
@end ifnottex
@tex
$x \cdot FLT\_RADIX^n$.
@end tex
efficiently. The result is computed by manipulating the exponent, rather than
by actually performing an exponentiation or multiplication. In this
floating-point implementation FLT_RADIX=2, which makes the <<scalbn>>
functions equivalent to the <<ldexp>> functions.
RETURNS
<[x]> times 2 to the power <[n]>. A range error may occur.
PORTABILITY
ANSI C, POSIX
SEEALSO
<<ldexp>>
*/
/*
* scalbn (double x, int n)
* scalbn(x,n) returns x* 2**n computed by exponent
* manipulation rather than by actually performing an
* exponentiation or a multiplication.
*/
#include "fdlibm.h"
#ifdef _NEED_FLOAT64
static const __float64
two54 = _F_64(1.80143985094819840000e+16), /* 0x43500000, 0x00000000 */
twom54 = _F_64(5.55111512312578270212e-17); /* 0x3C900000, 0x00000000 */
__float64
scalbn64(__float64 x, int n)
{
__int32_t k,hx,lx;
EXTRACT_WORDS(hx,lx,x);
k = (hx&0x7ff00000)>>20; /* extract exponent */
if (k==0) { /* 0 or subnormal x */
if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
x *= two54;
GET_HIGH_WORD(hx,x);
k = ((hx&0x7ff00000)>>20) - 54;
#if __SIZEOF_INT__ > 2
if (n< -50000) return __math_uflow(hx<0); /*underflow*/
#endif
}
if (k==0x7ff) return x+x; /* NaN or Inf */
#if __SIZEOF_INT__ > 2
if (n > 50000) /* in case integer overflow in n+k */
return __math_oflow(hx<0); /*overflow*/
#endif
k = k+n;
if (k > 0x7fe) return __math_oflow(hx<0); /* overflow */
if (k > 0) /* normal result */
{SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
if (k <= -54)
return __math_uflow(hx<0); /*underflow*/
k += 54; /* subnormal result */
SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
return check_uflow(x*twom54);
}
#if defined(_HAVE_ALIAS_ATTRIBUTE)
#ifndef __clang__
#pragma GCC diagnostic ignored "-Wmissing-attributes"
#endif
__strong_reference(scalbn64, ldexp64);
#else
__float64
ldexp64(__float64 value, int exp)
{
return scalbn64(value, exp);
}
#endif
_MATH_ALIAS_d_di(scalbn)
_MATH_ALIAS_d_di(ldexp)
#endif /* _NEED_FLOAT64 */
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