template <typename T>
std::list<T>
parallel_quick_sort(std::list<T> input)
{
  if (input.empty()) {
    return input;
  }
  std::list<T> result;
  result.splice(result.begin(), input, input.begin());
  T const& pivot    = *result.begin();
  auto divide_point = std::partition(
      input.begin(), input.end(), [&](T const& t) { return t < pivot; });
  std::list<T> lower_part;
  lower_part.splice(lower_part.end(), input, input.begin(), divide_point);
  std::future<std::list<T>> new_lower(
      std::async(&parallel_quick_sort<T>, std::move(lower_part)));
  auto new_higher(parallel_quick_sort(std::move(input)));
  result.splice(result.end(), new_higher);
  result.splice(result.begin(), new_lower.get());
  return result;
}