#include <iostream>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
//class
class Circle
{
private:
	double area;
public:
	double radius;
	double showArea()
	{
		return 3.14159*radius*radius;
	}
	string compare(Circle & a1)
	{
		if(radius > a1.radius)return "大於";
		else if(radius < a1.radius)return "小於";
		else return "等於";
	 } 
	 Circle & copy(Circle & a1)
	 {
	 	a1.radius = radius;
	 	return a1;
	 }
};
int main(int argc, char** argv) {
	//1.
	Circle a1;
	a1.radius = 5;
	
	//2.物件參考變數
	//注意：參考變數宣告時，就要立即指派(=a1) 
	Circle & a2 = a1;
	cout<<"a2 半徑 = "<<a2.radius<<endl;
	
	//3.物件函數傳遞的變數 = 物件參考變數
	Circle a3, a4;
	a3.radius = 3;
	a4.radius = 5;
	cout<<"\na3 半徑 "<<a3.compare(a4)<<" a4"<<endl;
	
	//4.物件函數return 值 = 物件參考變數
	Circle a5,a6,a7;
	a5.radius = 3;
	a6.radius = 5;	
	cout<<"\na5 半徑 "<<a5.compare(a6.copy(a7))<<" a4"<<endl;
	
	 
	return 0;
}