c++ 形状类Shape(派生出圆类Circle和矩形类Rectangle)

#include "stdafx.h"
#include<iostream>
using namespace std;
#define PI 3.14
class Shape
{
public:
	Shape(){}
	Shape(double _x,double _y):x(_x),y(_y){}
	double GetArea();
protected:
	double x,y;
 
};
double Shape::GetArea()
{
	return 0.0;
}
class Circle:public Shape
{
public:
	Circle(){}
	Circle(double r){ x=r;}//构造函数，并用r构造基类的x和y。
  double GetArea();//求圆的面积。
  double GetRadius();//获取圆的半径。
};
 
double Circle::GetArea()
{
	return PI*x*x;
}
double Circle::GetRadius()
{
	return x;
}
 
class Rectangle:public Shape
{
public:
	Rectangle(){}
	Rectangle(double l,double w){x = l;y=w;}//构造函数，并用l和w构造基类的x和y。
  double GetArea();//求矩形的面积。
  double GetLength();//获取矩形的长。
  double GetWidth();//获取矩形的宽
 
};
 double Rectangle::GetArea()
 {
	 return x*y;
 }
 double Rectangle::GetLength()
 {
	 return y;
 }
 double Rectangle::GetWidth()
 {
	 return x;
 }
int main(int argc, _TCHAR* argv[])
{
	
	Circle circle(1);
	
	cout<<" Radius="<<circle.GetRadius()<<" area="<<circle.GetArea()<<endl;
	Rectangle rectangle(3,4);
 
	cout<<" Length="<<rectangle.GetLength()<<" Width="<<rectangle.GetWidth()<<" area="<<rectangle.GetArea()<<endl;
	return 0;
}