tuple

my_tuple.cpp

#include <iostream>
#include <type_traits>

template <typename ... > struct my_tuple {};

template <typename T, typename ... Ts>
struct my_tuple<T, Ts...> : my_tuple<Ts...> {
	typedef T type;
	type value;
	my_tuple(T t, Ts ... ts) : value(t), my_tuple<Ts...>(ts...)
	{
	}
};


template <bool B, typename ... Ts> 
using eit = std::enable_if_t<B, typename my_tuple<Ts...>::type>;

template <unsigned N, typename T, typename ... Ts >
eit<N!=0, Ts...> my_tuple_get(my_tuple<T,Ts...>& t) {
	my_tuple<Ts...>& t2 = t;
	return my_tuple_get<N - 1, Ts ... >(t2);
}

template <unsigned N, typename ... Ts >
eit<N==0, Ts...> my_tuple_get(my_tuple<Ts...>& t) {
	return t.value;
}


int main(int argc, char *argv[])
{
	my_tuple<int> mt1 {123};
	my_tuple<int, std::string> mt2 {123, "test"};

	std::cout << "mt1" << std::endl;
	std::cout << my_tuple_get<0>(mt1) << std::endl;

	std::cout << "mt2" << std::endl;
	std::cout << my_tuple_get<0>(mt2) << std::endl;
	std::cout << my_tuple_get<1>(mt2) << std::endl;

	return 0;
}

output.txt

$ g++ -std=c++14 my_tuple.cpp
$ ./a.out 
mt1
123
mt2
123
test