扩展std :: tuple

#include<iostream>
#include<tuple>

template<typename T, typename... Args>
struct tuple_extender {
    using type = decltype(std::tuple_cat(std::declval<std::tuple<T>>(), std::declval<typename tuple_extender<Args...>::type>()));
};

template<typename T>
struct tuple_extender<T> {
    using type = std::tuple<T>;
};

template<typename... Args>
using tuple_extender_t = typename tuple_extender<Args...>::type;

int main() {
    tuple_extender_t<int, double, std::string> extended_tuple{42, 3.14, "hello"};
    std::cout<< std::get<0>(extended_tuple)<< std::endl;
    std::cout<< std::get<1>(extended_tuple)<< std::endl;
    std::cout<< std::get<2>(extended_tuple)<< std::endl;
    return 0;
}