#include <iostream>
#include <typeinfo>

class NullType {};

template<typename T=NullType, typename ... U>
struct TypeList {
    using head = T;
    using tail = TypeList<U ...>;
};

template<typename T>
struct TypeList<T> {
    using head = T;
    using tail = NullType;
};

using CharList = TypeList<char, signed char, unsigned char>;
using EmptyList = TypeList<>;

// struct TypeAt<unsigned int i, class T>;

template<unsigned int i, typename T, typename ... U>
struct TypeAt<0, TypeList<T, U...>> {
    using Result = T;
};

template<unsigned int i, class T, class ... U>
struct TypeAt<i, TypeList<T, U ...>> {
    using Result = typename TypeAt<i - 1, U...>::Result;
};

// template <typename Head, typename Tail>
// struct Length<TypeList<Head, Tail>> {
//     enum { value = Length<Tail>::value + 1};
// };

// template <typename Head, typename Tail>
// struct Length<TypeList<NullType, NullType>> {
//     enum { value = 0};
// };

int main() {

    std::cout << typeid(EmptyList::head).name() << std::endl;
    std::cout << typeid(EmptyList::tail).name() << std::endl;
    // std::cout << Length<EmptyList>::value << std::endl;
    std::cout << typeid(TypeAt<0, CharList>::Result).name() << std::endl;

}