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

You can not directly "return" a parameter pack, so what you need is something like this:

template< typename... Ts >
struct vct
{ ... };

template< typename T >
struct make_vct;

template< typename... Ts >
struct make_vct< std::tuple< Ts... > >
{
    typedef vct< Ts... > type;
};

and use

using Y = make_vct< U >::type;