private _bulkInsert(tuples: RecordViewTuple[]): RecordViewTuple[] {
   tuples.sort((a, b) => a.record.currentIndex - b.record.currentIndex);
   for (var i = 0; i < tuples.length; i++) {
     var tuple = tuples[i];
     if (isPresent(tuple.view)) {
       this._viewContainer.insert(tuple.view, tuple.record.currentIndex);
     } else {
       tuple.view =
           this._viewContainer.createEmbeddedView(this._templateRef, tuple.record.currentIndex);
     }
   }
   return tuples;
 }

 private _bulkRemove(tuples: RecordViewTuple[]): RecordViewTuple[] {
   tuples.sort((a, b) => a.record.previousIndex - b.record.previousIndex);
   var movedTuples = [];
   for (var i = tuples.length - 1; i >= 0; i--) {
     var tuple = tuples[i];
     // separate moved views from removed views.
     if (isPresent(tuple.record.currentIndex)) {
       tuple.view = this._viewContainer.detach(tuple.record.previousIndex);
       movedTuples.push(tuple);
     } else {
       this._viewContainer.remove(tuple.record.previousIndex);
     }
   }
   return movedTuples;
 }

  private _applyChanges(changes) {
    // TODO(rado): check if change detection can produce a change record that is
    // easier to consume than current.
    var recordViewTuples = [];
    changes.forEachRemovedItem((removedRecord) =>
                                   recordViewTuples.push(new RecordViewTuple(removedRecord, null)));

    changes.forEachMovedItem((movedRecord) =>
                                 recordViewTuples.push(new RecordViewTuple(movedRecord, null)));

    var insertTuples = this._bulkRemove(recordViewTuples);

    changes.forEachAddedItem((addedRecord) =>
                                 insertTuples.push(new RecordViewTuple(addedRecord, null)));

    this._bulkInsert(insertTuples);

    for (var i = 0; i < insertTuples.length; i++) {
      this._perViewChange(insertTuples[i].view, insertTuples[i].record);
    }

    for (var i = 0, ilen = this._viewContainer.length; i < ilen; i++) {
      this._viewContainer.get(i).setLocal('last', i === ilen - 1);
    }
  }