friend_class.cpp

#include <iostream>
using namespace std;

class Square;

class Rectangle {
	int width, height;

public:
	Rectangle(int w = 1, int h = 1):width(w),height(h){} 
	void display() {
		cout << "Rectangle: " << width * height << endl;
	};
	void morph(Square &);
};

class Square {
	int side;

public:
	Square(int s = 1):side(s){} 
	void display() {
		cout << "Square: " << side * side << endl;
	};
	friend class Rectangle;
};

void Rectangle::morph(Square &s) {
	width = s.side;
	height = s.side;
}

int main () {
	Rectangle rec(5,10);
	Square sq(5);
	cout << "Before:" << endl;
	rec.display();
	sq.display();

	rec.morph(sq);
	cout << "\nAfter:" << endl;
	rec.display();
	sq.display();
	return 0;
}