簡単な練習

using std::forward;

using std::tuple;

using std::get;
template<size_t ...Seq>

struct counting_sequence {};
template<size_t N, size_t ...Seq>

struct make_counting_sequence_impl {

    typedef typename make_counting_sequence_impl<N - 1, N, Seq...>::type type;

};
template<size_t ...Seq>

struct make_counting_sequence_impl<0, Seq...> {

    typedef counting_sequence<(Seq - 1)...> type;

};
template<size_t Max>

struct make_counting_sequence {

    typedef typename make_counting_sequence_impl<Max>::type type;

};


template<typename F, typename ...Params, size_t ...IntSeq>

auto apply_impl(F && f, tuple<Params...> && params, counting_sequence<IntSeq...> count)

    ->decltype(f(get<IntSeq>(forward<tuple<Params...>>(params))...))

{

    return f(get<IntSeq>(forward<tuple<Params...>>(params))...);

}
template<typename F, typename ...Params>

auto apply(F && f, tuple<Params...> && params)

    ->decltype(apply_impl(forward<F>(f),

                          forward<tuple<Params...>>(params),

                          typename make_counting_sequence<sizeof...(Params)>::type()))

{

    return apply_impl(forward<F>(f),

                      forward<tuple<Params...>>(params),

                      typename make_counting_sequence<sizeof...(Params)>::type());

}
void f() {

    apply([](int, double){}, { 1, 42.0 });

    apply([](){},{});

}

これと同じようなことをするコードがどこかにあったと思うのだが。ってそうそう、id:Cryoliteさんのところにあったと思う。