fieldkit/lib/math/random.js

Basic building blocks for computational design projects. Written in CoffeeScript for browser and server environments.

// Generated by CoffeeScript 1.6.3
/*

 Random based on Jon Watte's mersenne twister package.
 Adds several utility methods under a unified interface, that'll allow to use
 different number generators at some point.
*/


(function() {
  var Random, mersenne, util;

  mersenne = require('mersenne');

  util = require('../util');

  Random = (function() {
    function Random(initialSeed) {
      if (initialSeed == null) {
        initialSeed = 0;
      }
      this.seed(initialSeed);
    }

    Random.prototype.seed = function(value) {
      this.seedValue = value;
      return mersenne.seed(this.seedValue);
    };

    Random.prototype.toString = function() {
      return "Random(" + this.seedValue + ")";
    };

    Random.prototype.random = function() {
      var k;
      k = 1000000;
      return mersenne.rand(k) / k;
    };

    Random.prototype.randi = function(min, max) {
      return Math.floor(this.random() * (max - min) + min);
    };

    Random.prototype.randf = function(min, max) {
      return this.random() * (max - min) + min;
    };

    Random.prototype.randn = function() {
      return this.random() * 2 - 1;
    };

    Random.prototype.flipCoin = function(chance) {
      if (chance == null) {
        chance = 0.5;
      }
      return this.random() < chance;
    };

    Random.prototype.shuffle = function(list) {
      return list.sort(function() {
        return 0.5 - this.random();
      });
    };

    Random.prototype.pick = function(list, count) {
      var i, indices, result, _i, _j, _ref;
      if (count == null) {
        count = 1;
      }
      switch (list.length) {
        case 0:
          return null;
        case 1:
          return list[0];
        default:
          if (count === 1) {
            return list[this.randi(0, list.length)];
          } else {
            indices = [];
            for (i = _i = 0, _ref = list.length; 0 <= _ref ? _i < _ref : _i > _ref; i = 0 <= _ref ? ++_i : --_i) {
              indices.push(i);
            }
            util.shuffle(indices);
            result = [];
            for (i = _j = 0; 0 <= count ? _j < count : _j > count; i = 0 <= count ? ++_j : --_j) {
              result.push(list[indices[i]]);
            }
            return result;
          }
      }
    };

    Random.prototype.pickAB = function(listA, listB, chance) {
      var list;
      list = this.next() < chance ? listA : listB;
      return this.pick(list);
    };

    return Random;

  })();

  module.exports.Random = Random;

}).call(this);