src/math/exp.c

   1 /*
   2  * exp: exponential function.
   3  * Copyright (C) 2010 Nick Bowler.
   4  *
   5  * License LGPLv3+: GNU LGPL version 3 or later.  See COPYING.LIB for terms.
   6  * See <http://www.gnu.org/licenses/lgpl.html> if you did not receive a copy.
   7  * This is free software: you are free to change and redistribute it.
   8  * There is NO WARRANTY, to the extent permitted by law.
   9  */
  10
  11 #include <cstd/mathcommon.h>
  12
  13 TYPE MF(exp)(TYPE x)
  14 {
  15         TYPE acc = 1, last = -1, curr = 1;
  16
  17         if (x != x)
  18                 return x;
  19         if (x < 0)
  20                 return 1/MF(exp)(-x);
  21
  22         for (TYPE i = 1; acc != last; i++) {
  23                 last  = acc;
  24                 curr *= x/i;
  25                 acc  += curr;
  26         }
  27
  28         return acc;
  29 }