@Override
 public <T> App<E, T> reduce(T identity, BinaryOperator<T> accumulator, App<Push.t, T> app) {
   return alg.reduce(identity, accumulator, app);
 }
 @Override
 public <T> App<E, Long> count(App<Push.t, T> app) {
   return alg.count(app);
 }