namespace details {
template<class Functor, class Arg>
decltype(auto) try_invoke(Functor &&f, Arg &&arg) {
   if constexpr (std::is_invocable_v<Functor, Arg>) {
       return std::forward<Functor>(f)(std::forward<Arg>(arg));
   } /* else { */
       return std::forward<Arg>(arg);
   /* } */
}

template<class Tuple, class Functor, std::size_t... Is>
decltype(auto) transformElementsImpl(Tuple &&t, Functor &&f, std::index_sequence<Is...> &&) {
   return std::make_tuple(try_invoke(f, (std::get<Is>(std::forward<Tuple>(t)))) ...);
}
}

template<class Tuple, class Functor>
decltype(auto) transformElements(Tuple &&t, Functor &&f) {
   constexpr std::size_t tuple_size = std::tuple_size_v<std::decay_t<Tuple>>;
   return details::transformElementsImpl(std::forward<Tuple>(t),
                                         std::forward<Functor>(f),
                                         std::make_index_sequence<tuple_size> {});
}

struct Transformator {
   template <typename T>
   decltype(auto) operator()(T& t) const…