variadic+templates.cpp

#include <iostream>
#include <tuple>

template <size_t I, bool at_end, typename... ARGS>
struct IterOverTypesImpl;

template <size_t I, typename... ARGS>
struct IterOverTypesImpl<I, false, ARGS...> {
    void operator()() {
        using T = typename std::tuple_element<I, std::tuple<ARGS...>>::type;
        T().hello();

        constexpr auto size = std::tuple_size<std::tuple<ARGS...>>::value;
        IterOverTypesImpl<I + 1, I + 1 == size, ARGS...> func;
        func();
    }
};

template <size_t I, typename... ARGS>
struct IterOverTypesImpl<I, true, ARGS...> {
    void operator()() {
        std::cout << "end of iter" << std::endl;
    }
};

template <typename... ARGS>
struct IterOverTypes {
    void operator()() {
        static_assert(sizeof...(ARGS) != 0,
                      "IterOverTypes should be invoked by at least one type");
        IterOverTypesImpl<0, false, ARGS...> func;
        func();
    }
};

struct Foo {
    void hello() {
        std::cout << "Foo said hello" << std::endl;
    }
};

struct Bar {
    void hello() {
        std::cout << "Bar said hello" << std::endl;
    }
};

int main() {
    IterOverTypes<Foo, Bar>()();
}