Function foreach

3rdparty/libprocess/include/process/future.hpp:980–984

      lambda::bind(&internal::discarded<Future<T>>, promise->future()));

  foreach (const Future<T>& future, futures) {
    future.onAny([=](const Future<T>& f) {
      internal::select(f, promise);
    });
  }

  return promise->future();
}