template<class T, class R, class... Args>
struct mem_fn_wrap {
    R (T::* pm)(Args...);
    T& t;

    mem_fn_wrap(R (T::* pm)(Args...), T& t) : pm(pm), t(t) {}

    R operator()(Args&&... args) {
        return (t.*pm)(std::forward<Args>(args)...);
    }
};

template<class T, class R, class... Args>
mem_fn_wrap(R (T::*)(Args...), T&) -> mem_fn_wrap<T, R, Args...>;