#include <iostream>
using namespace std;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */

int main(int argc, char** argv) {
	//1.自動轉型(Implicit conversions)
	//計算圓面積
	int r,area;
	cout<<"輸入變數r=？";
	cin>>r;
	area = r*r*3.14159;
	cout<<"半徑r="<<r<<"，的圓面積="<<area<<endl;
	//結果：圓面積area=int，就會被刪除小數點，自動轉型成int 
	double area2 = 	r*r*3.14159;
	cout<<"半徑r="<<r<<"，的圓面積="<<area2<<endl;
	
	//2.指定轉型(Casting)
	cout<<"\n輸入變數r=？";
	cin>>r;
	double a1,a2,a3,a4;
	a1 = r*r*3.14159;
	a2 = r*r*(int)3.14159;
	a3 = (int)r*r*3.14159;
	a4 = (int)(r*r*3.14159);
	cout<<"的圓面積a1 = r*r*3.14159="<<a1<<endl; 
	cout<<"的圓面積a2 = r*r*(int)3.14159="<<a2<<endl; 
	cout<<"的圓面積a3 = (int)r*r*3.14159="<<a3<<endl; 
	cout<<"的圓面積a4 = (int)(r*r*3.14159)="<<a4<<endl; 
	 
	
	
	
	
	 
	return 0;
}