newlib/libm/math/s_ldexp.c

   1
   2 /* @(#)s_ldexp.c 5.1 93/09/24 */
   3 /*
   4  * ====================================================
   5  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   6  *
   7  * Developed at SunPro, a Sun Microsystems, Inc. business.
   8  * Permission to use, copy, modify, and distribute this
   9  * software is freely granted, provided that this notice
  10  * is preserved.
  11  * ====================================================
  12  */
  13
  14 /*
  15 FUNCTION
  16        <<ldexp>>, <<ldexpf>>---load exponent
  17
  18 INDEX
  19         ldexp
  20 INDEX
  21         ldexpf
  22
  23 SYNOPSIS
  24        #include <math.h>
  25        double ldexp(double <[val]>, int <[exp]>);
  26        float ldexpf(float <[val]>, int <[exp]>);
  27
  28 DESCRIPTION
  29 <<ldexp>> calculates the value
  30 @ifnottex
  31 <[val]> times 2 to the power <[exp]>.
  32 @end ifnottex
  33 @tex
  34 $val\times 2^{exp}$.
  35 @end tex
  36 <<ldexpf>> is identical, save that it takes and returns <<float>>
  37 rather than <<double>> values.
  38
  39 RETURNS
  40 <<ldexp>> returns the calculated value.
  41
  42 Underflow and overflow both set <<errno>> to <<ERANGE>>.
  43 On underflow, <<ldexp>> and <<ldexpf>> return 0.0.
  44 On overflow, <<ldexp>> returns plus or minus <<HUGE_VAL>>.
  45
  46 PORTABILITY
  47 <<ldexp>> is ANSI. <<ldexpf>> is an extension.
  48
  49 */
  50
  51 #include "fdlibm.h"
  52 #include <errno.h>
  53
  54 #ifndef _DOUBLE_IS_32BITS
  55
  56 #ifdef __STDC__
  57         double ldexp(double value, int exp)
  58 #else
  59         double ldexp(value, exp)
  60         double value; int exp;
  61 #endif
  62 {
  63         if(!finite(value)||value==0.0) return value;
  64         value = scalbn(value,exp);
  65         if(!finite(value)||value==0.0) errno = ERANGE;
  66         return value;
  67 }
  68
  69 #endif /* _DOUBLE_IS_32BITS */