4.22

#include<iostream>
#include<cmath>
using namespace std;
class location
{
public:
	location(double ,double);
    void show();
	friend double dist(location& d1,location& d2);
private:
	double x,y;
};
location::location(double X,double Y)
{
	x=X;
	y=Y;
}
void location::show()
{
	cout<<"点的坐标为：("<<x<<","<<y<<")"<<endl;
}
	
double dist(location& d1,location& d2)
{
	double L;
	L=sqrt((d1.x-d2.x)*(d1.x-d2.x)+(d1.y-d2.y)*(d1.y-d2.y));
	return L;
}
int main()
{
	location A(3,2),B(1,1);
	cout<<"A";A.show();
	cout<<"B";B.show();
	cout<<"俩点间的距离为"<<dist(A,B)<<endl;
	system("pause");
	return 0;
}