9-3-1.cpp

学习c++的ppt

#include <iostream.h>
class Point {
    private:
        float mX, mY;
	public:
        Point() { }
        Point(float x, float y)  {mX=x; mY=y;}
        float area() 
		{ cout << "Point fun is call !"<< endl; return 0.0;}
};
const float Pi = (float)3.141593;
class Circle:public Point  {  
    private:
         float  mRadius;
    public:
         Circle(float x, float y, float r):Point(x, y)
         { mRadius = r; }
         float area() 
         { cout << "Circle fun is call !"<< endl; 
             return Pi * mRadius * mRadius;
         }
};
int main()
{   Point  *pp; Circle c(10, 10, 6.4321);
    pp = &c;
    cout << pp->area() << endl;
    return 0;
}