  /**
   *  Returns a specified number of contiguous elements from the end of an observable sequence.
   * @description
   *  This operator accumulates a buffer with a length enough to store elements count elements. Upon completion of
   *  the source sequence, this buffer is drained on the result sequence. This causes the elements to be delayed.
   * @param {Number} count Number of elements to take from the end of the source sequence.
   * @returns {Observable} An observable sequence containing the specified number of elements from the end of the source sequence.
   */
  observableProto.takeLast = function (count) {
    if (count < 0) { throw new ArgumentOutOfRangeError(); }
    var source = this;
    return new AnonymousObservable(function (o) {
      var q = [];
      return source.subscribe(function (x) {
        q.push(x);
        q.length > count && q.shift();
      }, function (e) { o.onError(e); }, function () {
        while (q.length > 0) { o.onNext(q.shift()); }
        o.onCompleted();
      });
    }, source);
  };
