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

   1 'use strict';
   2
   3 var log = Math.log;
   4
   5 module.exports = function (x) {
   6         if (isNaN(x)) return NaN;
   7         x = Number(x);
   8         if (x < -1) return NaN;
   9         if (x > 1) return NaN;
  10         if (x === -1) return -Infinity;
  11         if (x === 1) return Infinity;
  12         if (x === 0) return x;
  13         return 0.5 * log((1 + x) / (1 - x));
  14 };