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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [mathfp/] [s_ldexp.c] - Blame information for rev 262

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1 207 jeremybenn
 
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/* @(#)z_ldexp.c 1.0 98/08/13 */
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/*
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FUNCTION
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       <<ldexp>>, <<ldexpf>>---load exponent
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INDEX
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        ldexp
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INDEX
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        ldexpf
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ANSI_SYNOPSIS
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       #include <math.h>
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       double ldexp(double <[val]>, int <[exp]>);
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       float ldexpf(float <[val]>, int <[exp]>);
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TRAD_SYNOPSIS
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       #include <math.h>
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       double ldexp(<[val]>, <[exp]>)
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              double <[val]>;
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              int <[exp]>;
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       float ldexpf(<[val]>, <[exp]>)
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              float <[val]>;
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              int <[exp]>;
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DESCRIPTION
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<<ldexp>> calculates the value
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@ifnottex
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<[val]> times 2 to the power <[exp]>.
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@end ifnottex
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@tex
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$val\times 2^{exp}$.
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@end tex
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<<ldexpf>> is identical, save that it takes and returns <<float>>
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rather than <<double>> values.
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RETURNS
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<<ldexp>> returns the calculated value.
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Underflow and overflow both set <<errno>> to <<ERANGE>>.
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On underflow, <<ldexp>> and <<ldexpf>> return 0.0.
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On overflow, <<ldexp>> returns plus or minus <<HUGE_VAL>>.
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PORTABILITY
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<<ldexp>> is ANSI. <<ldexpf>> is an extension.
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*/
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/******************************************************************
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 * ldexp
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 *
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 * Input:
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 *   d - a floating point value
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 *   e - an exponent value
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 *
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 * Output:
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 *   A floating point value f such that f = d * 2 ^ e.
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 *
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 * Description:
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 *   This function creates a floating point number f such that
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 *   f = d * 2 ^ e.
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 *
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 *****************************************************************/
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#include <float.h>
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#include "fdlibm.h"
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#include "zmath.h"
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#ifndef _DOUBLE_IS_32BITS
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#define DOUBLE_EXP_OFFS 1023
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double
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_DEFUN (ldexp, (double, int),
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        double d _AND
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        int e)
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{
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  int exp;
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  __uint32_t hd;
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  GET_HIGH_WORD (hd, d);
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  /* Check for special values and then scale d by e. */
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  switch (numtest (d))
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    {
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      case NAN:
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        errno = EDOM;
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        break;
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      case INF:
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        errno = ERANGE;
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        break;
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      case 0:
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        break;
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      default:
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        exp = (hd & 0x7ff00000) >> 20;
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        exp += e;
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        if (exp > DBL_MAX_EXP + DOUBLE_EXP_OFFS)
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         {
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           errno = ERANGE;
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           d = z_infinity.d;
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         }
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        else if (exp < DBL_MIN_EXP + DOUBLE_EXP_OFFS)
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         {
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           errno = ERANGE;
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           d = -z_infinity.d;
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         }
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        else
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         {
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           hd &= 0x800fffff;
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           hd |= exp << 20;
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           SET_HIGH_WORD (d, hd);
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         }
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    }
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    return (d);
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}
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#endif /* _DOUBLE_IS_32BITS */

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