class Circle : Point {Because it is derived from a base class (Point), Circle inherits all the class members.
Point(int atx,int aty ) ; // Constructor
inline virtual ~Point() ; // Destructor
virtual void Draw() ;
Circle(int atx,int aty,int theRadius) ;Think of the Circle class as the Point class with an extra member (radius). It inherits the base class Member functions and private variables x and y.
inline virtual ~Circle() ;
virtual void Draw() ;
It cannot assign or use these except implicitly because they are private, so it has to do it through the Circle constructor's Initialiazer list. This is something you should accept for now, I'll come back to initializer lists in a future tutorial.
In the Circle Constructor, before theRadius is assigned to radius, the Point part of Circle is constructed through a call to Point's constructor in the initializer list. This list is everything between the : and the { below.
Circle::Circle(int atx,int aty,int theRadius) : Point(atx,aty)Incidentally, constructor type initialization can be used for all built-in types.
int a1(10) ;Both do the same.
int a2=10 ;
On the next page : What is Polymorphism?
