  // Shim in iterator support
  var $iterator$ = (typeof Symbol === 'function' && Symbol.iterator) ||
    '_es6shim_iterator_';
  // Bug for mozilla version
  if (root.Set && typeof new root.Set()['@@iterator'] === 'function') {
    $iterator$ = '@@iterator';
  }

  var doneEnumerator = Rx.doneEnumerator = { done: true, value: undefined };

  var isIterable = Rx.helpers.isIterable = function (o) {
    return o[$iterator$] !== undefined;
  }

  var isArrayLike = Rx.helpers.isArrayLike = function (o) {
    return o && o.length !== undefined;
  }

  Rx.helpers.iterator = $iterator$;
