126 lines
2.3 KiB
C
126 lines
2.3 KiB
C
|
|
||
|
|
/* @(#)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 */
|