Recursively Pass Template Template To a Template Template Function

Question

It seems to me, that since in C++ we can pass a template template, then a function accepting a template template should be able to pass a (its) template template into itself. However this appears not to be the case.

template< typename PREVIOUS_TYPE_T, typename TYPE_T >
struct Node
{
    typedef TYPE_T TYPE;
    typedef PREVIOUS_TYPE_T PREVIOUS_TYPE;
    PREVIOUS_TYPE_T* previous;
    template< template< typename... > typename FUNCTOR_T, typename... CURRENT_ARGUMENTS_T >
    void DoCall() {
        previous->DoCall< FUNCTOR_T, TYPE_T, CURRENT_ARGUMENTS_T... >();
    }
};

Is there anyway to pass FUNCTOR_T above, or any work around to doing so?

Answer 1

You cannot use ARGUMENTS_T. That name has no effect.

When you're passing a template template around, it's still a template with no parameters passed to it. There is no template parameter to extract from std::plus, as opposed to std::plus<int>.

Instead, use CURRENT_ARGUMENTS_T, which is what you intended to forward.

Also, you previous is a dependent type. You must desambiguate the template:

previous->template DoCall< FUNCTOR_T, TYPE_T, CURRENT_ARGUMENTS_T... >();