void func(double, double) { std::cout << "func" << std::endl; }

template<std::size_t I = 0, typename... Tp>
inline typename std::enable_if<I == sizeof...(Tp), void>::type
    for_each(pack<Tp...> &)
{
}

template<std::size_t I = 0, typename... Tp>
inline typename std::enable_if<I < sizeof...(Tp), void>::type
    for_each(pack<Tp...>& t)
{
    std::cout << I << ',';
    for_each<I + 1, Tp...>(t);
}

int main() {
    parameters<decltype(func)> pack;
    for_each(pack);
}