#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
{
public:
	double radius;
	double area;
	double showArea()
	{
		area = 3.14159*radius*radius;
		return area;
	}
	string compare(Circle c2)
	{
		if(radius > c2.radius)
			return "大於";
		else if(radius < c2.radius)
			return "小於";
		else
			return "等於";
	} 
	Circle copy()
	{
		Circle c;
		c.radius = radius;
		c.area = area;
		return c;
	}
};
int main(int argc, char** argv) {
	//1.什麼是類別
		//像 int,double 一樣，是 C++的一種型別（自創型別） 
	//2.類別用來做什麼
		//o	宣告變數
		//o	宣告指標
		//o	宣告參考
		//o	物件轉型
		//o	物件識別
		//o	執行環境製做物件的說明書
	//3.
	Circle a1;
	a1.radius = 5;
	cout<<"a1 area = "<<a1.showArea()<<endl;
	
	//4.用excel講解object的記憶體配置
	//重點1：物件a1的值 = 第一個成員變數radius的記憶體位址
	//所以：物件a1的值，原來也是個記憶體位址
	
	//5.物件的指派：把成員的值，全部指派給對方 
	Circle a2;
	a2 = a1; 
	cout<<"\na2 radius = "<<a2.radius<<endl;
	cout<<"\na2 area = "<<a2.area<<endl;
	
	//6.物件的function有傳遞參數（傳遞物件）：a3.compare()
	Circle a3;
	a3.radius = 6;
	cout<<"\n a3半徑 "<< a3.compare(a1)<<" a1 "<<endl; 
	cout<<"\n a3半徑 "<< a3.compare(a2)<<" a2 "<<endl; 

	//7.物件的函數，return一個物件：a4.copy()
	Circle a4;
	a4 = a3.copy();
	cout<<"\na4 radius = "<<a4.radius<<endl;
	cout<<"\na4 area = "<<a4.area<<endl;
	
	 
	return 0;
}