Тестовые примеры / ch2 / virtual

	// source module: virtual.C

 	#include <iostream.h>

	class date {

   		int year, month, day;

 		public:

		date(int y, int m, int d)   {  year=y; month=m; day=d; };

   		virtual ~date() {};

   		virtual void print() {			cerr << year << '/' << month << '/' << 			day << "\n";};

		virtual void set (int a, int b, int c) 	{ year=a;  month=b;  day=c; };

  	};



 	class derived : public date {

   		 int x;

   		public:

    		derived (int a,int b,int c,int d): date(a,b,c), x(d) {};

    		~derived() {};

    		void print() { date::print(); cout << "derived: x=" << x << "\n"; };

    		virtual void set(int a, int b, int c) {x=a;};

	};



	int main() 

	{

		date foo(1991,5,4);

		derived y(1,2,3,4);

		date* p = &y;

		p->print();  		 	// derived::print()

		p = & foo;

		p->print();   			// date::print()

		return 0;

 	}