class Animal {
    virtual void bark ()=0;
    virtual void eat  ()=0;
};
class Brainy {
    virtual void act ()=0;
};

class Dog : public Animal, public Brainy {
    virtual void bark () {
        act_and_bark();
    }

    virtual void act () {
        act_and_bark();
    }

    virtual void eat  () {
        // Eat
    }
private:
    void act_and_bark () {
        // Bark
    }
};


class BrainyDog : public Dog
{
    virtual void act () {
        // Talk
    }
};