git.r.bdr.sh - rbdr/dotfiles/blob

   1 'use strict';
   2
   3 var exp = Math.exp;
   4
   5 module.exports = function (x) {
   6         var a, b;
   7         if (isNaN(x)) return NaN;
   8         x = Number(x);
   9         if (x === 0) return x;
  10         if (x === Infinity) return 1;
  11         if (x === -Infinity) return -1;
  12         a = exp(x);
  13         if (a === Infinity) return 1;
  14         b = exp(-x);
  15         if (b === Infinity) return -1;
  16         return (a - b) / (a + b);
  17 };