class rac {
	public:
		virtual void m() { cout << "rac" << endl; }
};
class c: public rac {
	public:
		void m() { cout << "c" << endl;
};

rac *p = new c;
p -> m();       // Résultat: "c"
p = new rac;
p -> m();       // Résultat: "rac"