C语言相关程序

#include<iostream.h>
class vector
{
	int x,y;
public:
	vector(){};
	vector(int x1,int y1){x=x1;y=y1;}
   friend vector operator +=(vector v1,vector v2)
	{
		v1.x+=v2.x;
		v1.y+=v2.y;
		return v1;
	}
	vector operator-=(vector v)
	{
		vector tmp;
		tmp.x=x-v.x;
		tmp.y=y-v.y;
		return tmp;
	}
	void display()
	{
		cout<<"("<<x<<","<<y<<")"<<endl;
	}
};
void main()
{
	vector v1(6,8),v2(3,4),v3,v4;
	cout<<"v1=";
	v1.display();
	cout<<"v2=";
	v2.display();
	v3=v1+=v2;
	cout<<"v3=";
	v3.display();
	v4=v1-=v2;
	cout<<"v4=";
	v4.display();
}