#include <tuple>

template <typename... types1_t, typename... types2_t, typename cmp>
class tuple_merge<std::tuple<types1_t...>, std::tuple<types2_t...>, cmp> {
  template <typename T1, typename T2, typename... Args>
  struct merge_helper {
    using type = typename merge_helper<T1, typename std::tuple<Args...>, Args...>::type;
  };

  template <typename... Args>
  struct merge_helper<std::tuple<>, std::tuple<Args...>> {
    using type = std::tuple<Args...>;
  };

  template <typename T1, typename T2, typename... Args>
  struct merge_helper<std::tuple<T1, types1_t...>, std::tuple<T2, types2_t...>, Args...> {
    using next_type = typename std::conditional_t<cmp::template cmp<T1, T2>(), std::tuple<T1>, std::tuple<T2>>;
    using type = typename merge_helper<std::tuple<types1_t...>, std::tuple<types2_t...>, Args..., next_type>::type;
  };

 public:
  using type = typename merge_helper<std::tuple<types1_t...>, std::tuple<types2_t...>>::type;
};