I want to create a vector (or array) of objects of different types but all sharing the same concept.  

similar to `Vec<Box<dyn trait>>` of Rust.

```
struct Dog {
    void talk() {
        std::cout << "guau guau" << std::endl;
    }
};

struct Cat {
    void talk() {
        std::cout << "miau miau" << std::endl;
    }
};

template <typename T>
concept Talk = requires(T a) {
    { a.talk() } -> std::convertible_to<void>;
};

int main() {
    auto x = Dog{};
    auto y = Cat{};

    ??? pets = {x, y};

    for(auto& pet: pets) {
        pet.talk();
    }

    return 0;
}

```