src/math/scalb.c

   1 /* origin: FreeBSD /usr/src/lib/msun/src/e_scalb.c */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunSoft, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12 /*
  13  * scalb(x, fn) is provide for
  14  * passing various standard test suite. One
  15  * should use scalbn() instead.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <math.h>
  20
  21 double scalb(double x, double fn)
  22 {
  23         if (isnan(x) || isnan(fn))
  24                 return x*fn;
  25         if (!isfinite(fn)) {
  26                 if (fn > 0.0)
  27                         return x*fn;
  28                 else
  29                         return x/(-fn);
  30         }
  31         if (rint(fn) != fn) return (fn-fn)/(fn-fn);
  32         if ( fn > 65000.0) return scalbn(x, 65000);
  33         if (-fn > 65000.0) return scalbn(x,-65000);
  34         return scalbn(x,(int)fn);
  35 }