3-7 类的友元函数的应用

5 6 2 3

The first point is the coordinate:X=5,Y=6
The second point is the coordinate:X=2,Y=3
The distance between the two points is:4.24264
#include <iostream>
#include <cmath >
using namespace std;
class point
{
private:
    double x;
    double y;
    double x1;
    double y1;
public:
    friend void distance(point &);
    void setpoint()
    {
        cin>>x>>y>>x1>>y1;
    }
    void showpoint()
    {
        cout<<"The first point is the coordinate:X="<<x<<",Y="<<y<<endl;
        cout<<"The second point is the coordinate:X="<<x1<<",Y="<<y1<<endl;
    }
};
void distance(point &a)
{
    double k,j;
    j=(a.x-a.x1)*(a.x-a.x1)+(a.y-a.y1)*(a.y-a.y1);
    k=sqrt(j);
    cout<<"The distance between the two points is:"<<k<<endl;
}
int main()
{
    point d;
    d.setpoint();
    d.showpoint();
    distance(d);
    return 0;
}