#include <iostream>
    using namespace std;
    class BoxExample
    {
        double W;
        public:
        friend void printW(BoxExample box );
        void setW( double width );
    };
    void BoxExample::setW( double width )
    {
        W = width;
    }
    void printW(BoxExample box )
    {
        box.W = box.W * 3;
        cout << "Width of box : " << box.W << endl;
    }
    int main( )
    {
        BoxExample box;
        box.setW(15.0);
        printW( box );
        return 0;
   }

#include <iostream>
    using namespace std;
    class Example 
    {
        int W, H;
        public:
        void set_values (int, int);
        int RectArea () {return (W * H);}
        friend Example duplicate (Example);
    };
    void Example::set_values (int p, int q) 
    {
        W = p;
        H = q;
    }
    Example duplicate (Example RectParameter)
    {
        Example Rect;
        Rect.W = RectParameter.W * 2;
        Rect.H = RectParameter.H * 3;
        return (Rect);
    }  
    int main ()  
    {
        Example Rectangle, RectangleB;
        Rectangle.set_values (2, 3);
        RectangleB = duplicate (Rectangle);
        cout << RectangleB.RectArea();
        return 0;
    }