tuple impl

ink_tuple.cpp

#include <iostream>
#include <tuple>

// 获取第N个元素的类型
template <int N, typename ...S>
class tuple_item;

template <int N, typename TS, typename ...S>
class tuple_item<N, TS, S...>: public tuple_item<N, S...> {};

template <typename TS, typename ...S>
class tuple_item<sizeof...(S) + 1, TS, S...> {
public:
    typedef TS type;
};

template<int N, typename TS, typename ...S>
class tuple_work : public tuple_work<N, S...>{};

template<typename TS, typename ...S>
class tuple_work <sizeof...(S) + 1, TS, S...> : public tuple_work<sizeof...(S), S...> {
public:
    tuple_work(TS &&arg1, S&& ...args) : 
        _data(std::forward<TS>(arg1)),
        tuple_work<sizeof...(S), S...>(std::forward<S>(args) ...) {
    }

    static TS get(tuple_work<sizeof...(S) + 1, TS, S...> &&t) {
        return std::forward<tuple_work<sizeof...(S) + 1, TS, S...>>(t)._get();
    }

    TS _get() {
        return _data;
    }

private:
    TS &&_data;
};

template<typename TS>
class tuple_work<1, TS> {
public:
    tuple_work(TS &&arg1) : _data(std::forward<TS>(arg1)) {}

    static TS get(tuple_work<1, TS> &&t) {
        return std::forward<tuple_work<1, TS>>(t)._get();
    }

    TS _get() {
        return _data;
    }
private:
    TS &&_data;
};

template<typename ...S>
class tuple : public tuple_work<sizeof...(S), S...>{
public:
    tuple(S&& ...args) : tuple_work<sizeof...(S), S...>(std::forward<S>(args)...) {}
};


template<int N, typename S>
class tuple_get_work;

template<int N, typename ...S>
class tuple_get_work<N, tuple<S...>> {
public:
    static typename tuple_item<N, S...>::type get(tuple<S...> &&data) {
        return tuple_work<N, S...>::get(std::forward<tuple<S...>>(data));
    }
};

template<int N, typename ...S>
typename tuple_item<sizeof...(S) - N, S...>::type get(tuple<S...> &&data) {
    return tuple_get_work<sizeof...(S) - N, tuple<S...>>::get(std::forward<tuple<S...>>(data));
}

int main() {
    auto data = tuple<int, int, int>(123, 234, 1234);
    std::cout << get<0>(tuple<double, int, std::string>(123.1, 234, "1234")) << std::endl;
}