p9_7.cpp

来自「相当丰富的C++源码」· C++ 代码 · 共 44 行

#include<iostream>
using namespace std;
class Point
{
private:
	int X,Y;
public:
	Point(int X=0,int Y=0)
	{    
       this->X=X,this->Y=Y;  
	}
    virtual double area()   //求面积
	{
		return 0.0; 
    }
};
const double PI=3.14159;
class Circle :public Point
{
private:
	double radius;   //半径
public:
	Circle(int X, int Y, double R):Point(X,Y)
	{	
		radius=R;   
	}
	double area()   //求面积
	{
		return PI*radius*radius; 
    }
};
void main()
{
  Point P1(10,10);
  cout<<"P1.area()="<<P1.area()<<endl;
  Circle C1(10,10,20);
  cout<<"C1.area()="<<C1.area()<<endl;
  Point *Pp;
  Pp=&C1;
  cout<<"Pp->area()="<<Pp->area()<<endl;
  Point *Rp=&C1;
  cout<<"Rp->area()="<<Rp->area()<<endl;
}