class Human;
class Cat;

class Animal
{
public:
virtual void face(Animal & animal) = 0;
virtual void face(Human & human) = 0;
virtual void face(Cat & cat) = 0;
};

class Human : public Animal
{
public:
virtual void face(Animal & animal);
virtual void face(Human & human);
virtual void face(Cat & cat);
};

class Cat : public Animal
{
public:
virtual void face(Animal& animal);
virtual void face(Human & human);
virtual void face(Cat & cat);
};

///////////////////////////////////////////

void Human::face(Animal & animal)
{
animal.face(*this);
}

void Human::face(Human & human)
{
std::cout << “Human faces Human: Shakehand\n”;
}

void Human::face(Cat & cat)
{
std::cout << “Cat faces Human : eat?\n”;
}

void Cat::face(Animal & animal)
{
animal.face(*this);
}

void Cat::face(Human & human)
{
std::cout << “Human faces Cat: run?\n”;
}

void Cat::face(Cat & cat)
{
std::cout << “Cat faces Cat: shakehand\n”;
}

///////////////////////////////////////////

int main()
{
Animal & acat = * new Cat();
Animal & ahuman = * new Human();
ahuman.face(acat);
return 0;
}