15 void move (double dx, double dy);
16 virtual double area (void) const = 0;
17 virtual double perimeter (void) const = 0;
22 class Circle:public Shape
27 Circle (double r):radius (r)
30 virtual double area (void) const;
31 virtual double perimeter (void) const;
34 class Square:public Shape
39 Square (double w):width (w)
42 virtual double area (void) const;
43 virtual double perimeter (void) const;