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/* @(#)z_ldexp.c 1.0 98/08/13 */
/*
FUNCTION
<<ldexp>>, <<ldexpf>>---load exponent
INDEX
ldexp
INDEX
ldexpf
ANSI_SYNOPSIS
#include <math.h>
double ldexp(double <[val]>, int <[exp]>);
float ldexpf(float <[val]>, int <[exp]>);
TRAD_SYNOPSIS
#include <math.h>
double ldexp(<[val]>, <[exp]>)
double <[val]>;
int <[exp]>;
float ldexpf(<[val]>, <[exp]>)
float <[val]>;
int <[exp]>;
DESCRIPTION
<<ldexp>> calculates the value
@ifinfo
<[val]> times 2 to the power <[exp]>.
@end ifinfo
@tex
$val\times 2^{exp}$.
@end tex
<<ldexpf>> is identical, save that it takes and returns <<float>>
rather than <<double>> values.
RETURNS
<<ldexp>> returns the calculated value.
Underflow and overflow both set <<errno>> to <<ERANGE>>.
On underflow, <<ldexp>> and <<ldexpf>> return 0.0.
On overflow, <<ldexp>> returns plus or minus <<HUGE_VAL>>.
PORTABILITY
<<ldexp>> is ANSI, <<ldexpf>> is an extension.
*/
/******************************************************************
* ldexp
*
* Input:
* d - a floating point value
* e - an exponent value
*
* Output:
* A floating point value f such that f = d * 2 ^ e.
*
* Description:
* This function creates a floating point number f such that
* f = d * 2 ^ e.
*
*****************************************************************/
#include <float.h>
#include "fdlibm.h"
#include "zmath.h"
#ifndef _DOUBLE_IS_32BITS
#define DOUBLE_EXP_OFFS 1023
double
_DEFUN (ldexp, (double, int),
double d _AND
int e)
{
int exp;
__uint32_t hd;
GET_HIGH_WORD (hd, d);
/* Check for special values and then scale d by e. */
switch (numtest (d))
{
case NAN:
errno = EDOM;
break;
case INF:
errno = ERANGE;
break;
case 0:
break;
default:
exp = (hd & 0x7ff00000) >> 20;
exp += e;
if (exp > DBL_MAX_EXP + DOUBLE_EXP_OFFS)
{
errno = ERANGE;
d = z_infinity.d;
}
else if (exp < DBL_MIN_EXP + DOUBLE_EXP_OFFS)
{
errno = ERANGE;
d = -z_infinity.d;
}
else
{
hd &= 0x800fffff;
hd |= exp << 20;
SET_HIGH_WORD (d, hd);
}
}
return (d);
}
#endif /* _DOUBLE_IS_32BITS */
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