template<class T>
std::future<std::decay_t<T>> make_ready_future( T&& t ) {
  std::promise<std::decay_t<T>> pr;
  auto r = pr.get_future();
  pr.set_value(std::forward<T>(t));
  return r;
}

template<class T>
struct promise_pipe {
  std::future<T> out;
  std::function<void(T)> in;
  promise_pipe() {
    auto pr = std::make_shared<std::promise<T>>();
    out = pr->get_future();
    in = [pr](T t)mutable{
      if (pr) pr->set_value(std::forward<T>(t));
      pr = {};
    };
  }
};