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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
 
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 + 1023))
         {
           errno = ERANGE;
           d = z_infinity.d;
         }
        else if (exp < DBL_MIN_EXP)
         { 
           errno = ERANGE;
           d = -z_infinity.d;
         }
        else
         {
           hd &= 0x800fffff;
           hd |= exp << 20;
           SET_HIGH_WORD (d, hd);
         }
    }
 
    return (d);
}
 
#endif /* _DOUBLE_IS_32BITS */