#include <cstdint>
#include <type_traits>
#include <utility>

namespace detail
{
    template <std::size_t Index, typename ...Ts>
    struct get
    {
        static_assert(Index < sizeof...(Ts), "types_list::get index out of bounds");

    private:
        template <std::size_t CurrentIndex, typename ...Us>
        struct helper
        {
            using type = void;
        };

        template <std::size_t CurrentIndex, typename U, typename ...Us>
        struct helper<CurrentIndex, U, Us...>
        {
            using type = std::conditional_t<CurrentIndex == Index, U, typename helper<CurrentIndex + 1, Us...>::type>;
        };

    public:
        using type = typename helper<0, Ts...>::type;
    };

    template <template <typename...> typename TL, typename ...Ts>
    struct list_impl
    {
        using unpack = TL<Ts...>;

        inline static constexpr std::size_t size = sizeof...(Ts);

        template <std::size_t Index>
        using get = typename detail::get<Index, Ts...>::type;

        template <typename ...Us>
        using push_back = typename list_impl<TL, Ts..., Us...>::unpack;
    };
}

template <typename ...Ts>
struct types_list : public detail::list_impl<types_list, Ts...>
{
};

template <typename T, typename ...Ts>
struct types_list<T, Ts...> : public detail::list_impl<types_list, T, Ts...>
{
private:
    using impl = detail::list_impl<types_list, T, Ts...>;

public:
    using front = typename impl:: template get<0>;
    using back = typename impl:: template get<impl::size - 1>;
};

using t = types_list<int, double>::front;
using t2 = types_list<int, double>::back;
using t3 = types_list<int, char, double>::get<1>;
using t4 = types_list<>::push_back<int>::push_back<std::pair<int,int>>::back;

int main()
{
    t x = 10;
    t2 y = 1.4;
    t3 z = 'a';
    t4 v = {1,1};
}