effective way to select last parameter of variadic template

Question

I know how to select first parameter of variadic template:

template< class...Args> struct select_first;
template< class A, class ...Args> struct          


        

Answer 1

A pretty dumb approach would be to write a helper class and specialize for each number of parameters (up to some limit of your choice). You could use preprocessor for that.

template
struct select_last_helper;

template
struct select_last_helper {
    using type = T1;
};

template
struct select_last_helper {
    using type = T2;
};

template
struct select_last_helper {
    using type = T3;
};

template
struct select_last {
    using type = typename select_last_helper::type;
};

O(1) template instantiations :)