#include<iostream>
#include<Cmath>
using namespace std;
class Point //定义坐标点类
{
public:
    Point():x(0),y(0) {};
    Point(double x0, double y0):x(x0),y(y0){};
    void PrintPoint(); //输出点的信息
    double getx()
    {
        return x;
    }
    double gety()
    {
        return y;
    }
protected:
    double x,y;   //点的横坐标和纵坐标
};
void Point::PrintPoint()
{
    cout<<"Point: ("<<x<<","<<y<<")";    //输出点
}
class Line: public Point   //利用坐标点类定义直线类, 其基类的数据成员表示直线的中点
{
public:
    Line(Point pts, Point pte); //构造函数，用初始化直线的两个端点及由基类数据成员描述的中点
    double Length();    //计算并返回直线的长度
    void PrintLine();   //输出直线的两个端点和直线长度
private:
    class Point pts,pte;   //直线的两个端点，从Point类继承的数据成员表示直线的中点
};
double Line::Length()
{
    return sqrt(pow((pts.getx()-pte.getx()),2)+pow((pts.gety()-pte.gety()),2));
}

void Line::PrintLine()
{
    cout<<"1st ("<<pts.getx()<<","<<pts.gety()<<")"<<endl;
    cout<<"2nd ("<<pte.getx()<<","<<pte.gety()<<")"<<endl;
    cout<<"长度："<<Length()<<endl;
}
Line::Line(Point ps, Point pe):Point((ps.getx()+pe.getx())/2,(ps.gety()+pe.gety())/2)
{
    pts=ps;
    pte=pe;//这一段不是太懂
}
int main()
{
    Point ps(-2,5),pe(7,9);
    Line l(ps,pe);
    cout<<"About the Line: "<<endl;
    l.PrintLine();  //输出直线l的信息：两端点及长度
    cout<<"The middle point of Line is: "<<endl;
    l.PrintPoint(); //输出直线l中点的信息
    return 0;
}