生成一个多阶的vector template <typename T, int N> struct get_vec_by_rank; template <typename T> struct get_vec_by_rank<T, 0> { using Type = T; }; template <typename T, int N> struct get_vec_by_rank { using Type = std::vector<typename get_vec_by_rank<T, N - 1>::Type>; }; ...