How do I strip a tuple<> back into a variadic template list of types?

Question

Is there a way to strip a std::tuple in order to get it back to T...?

Example

Suppose

Answer 1

Using c++17 std::apply.

using U = std::tuple;
using X = vct;
using Y = vct>; // should be same as X

auto my_y = std::apply(
        [](auto... ts) {
            using Y = vct;
            return Y{};
        },
        U{});