Variadic to Head/Tail Generator

#include <cstring>

namespace my_types
{

struct nil {};

template <typename T, typename U>
struct chain
{
    typedef T first_type;
    typedef U second_type;
};

}

template <template <typename, typename> class Chain, typename Nil>
struct chain_generator
{
    template <typename T, typename... Args>
    struct gen
    {
    private:
        template <size_t S = sizeof...(Args), typename Dummy = void>
        struct inner
        {
            typedef Chain<T, typename gen<Args...>::type > type;
        };

        template <typename Dummy>
        struct inner<0, Dummy>
        {
            typedef Chain<T, Nil> type;
        };
    public:
        typedef typename inner<sizeof...(Args)>::type type;
    };
};


int main( /* int argc, char* argv[] */ )
{
    using my_types::chain;
    using my_types::nil;

    typedef chain<int, chain<float, chain<char, nil>>> t0;

    typedef chain_generator<chain, nil> my_gen;

    typedef my_gen::gen<int, float, char>::type t1;

    return 0;
}