Lazy cartesian product

lazy_product.js

// From http://jsperf.com/lazy-cartesian-product/33 and http://stackoverflow.com/questions/9422386/lazy-cartesian-product-of-arrays-arbitrary-nested-loops

function lazyProductMZ2(sets, block, _context) {
  var n = sets.length,
    carets = [],
    args = [];

  function init() {
    for (var i = 0; i < n; i++) {
      carets[i] = 0;
      args[i] = sets[i][0];
    }
  }

  function next() {
    if (!args.length) {
      init();
      return true;
    }
    var i = n - 1;
    carets[i]++;
    while (carets[i] == sets[i].length) {
      if (i == 0) {
        return false;
      }
      carets[i] = 0;
      args[i] = sets[i][0];
      carets[--i]++;
    }
    args[i] = sets[i][carets[i]];
    return true;
  }

  while (next()) {
    block.apply(_context, args);
  }
}

function CrossProduct(sets) {
  this.sets = sets;
  this.carets = [];
  this.args = [];
}

CrossProduct.prototype = {
  init: function() {
    for (var i = 0, n = this.sets.length; i < n; i++) {
      this.carets[i] = 0;
      this.args[i] = this.sets[i][0];
    }
  },

  next: function() {
    if (!this.args.length) {
      this.init();
      return true;
    }
    var i = this.sets.length - 1;
    this.carets[i]++;
    if (this.carets[i] < this.sets[i].length) {
      this.args[i] = this.sets[i][this.carets[i]];
      return true;
    }
    while (this.carets[i] == this.sets[i].length) {
      if (i == 0) {
        return false;
      }
      this.carets[i] = 0;
      this.args[i] = this.sets[i][0];
      this.carets[--i]++;
    }
    this.args[i] = this.sets[i][this.carets[i]];
    return true;
  },

  do: function(block, _context) {
    return block.apply(_context, this.args);
  }
}


function callback() {}