点类派生直线类

定义点类Point，并以点类为基类，派生出直线类Line，从基类中继承的点的信息表示直线的中点。

#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();double gety();protected:double x,y;   //点的横坐标和纵坐标};void Point::PrintPoint(){cout<<"Point: ("<<x<<","<<y<<")";    //输出点}double Point::getx(){return x;}double Point::gety(){return y;}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 pt1, Point pt2); //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};Line::Line(Point pt1, Point pt2):Point((pt1.getx()+pt2.getx())/2,(pt1.gety()+pt2.gety())/2)  //中点信息{      pts=pt1;      pte=pt2;  }double Line::Length(){double a=(pts.getx()-pte.getx())*(pts.getx()-pte.getx());double b=(pts.gety()-pte.gety())*(pts.gety()-pte.gety());return sqrt(a+b);}void Line::PrintLine(){cout<<"点1：";pts.PrintPoint();cout<<endl;cout<<"点2：";pte.PrintPoint();cout<<endl;cout<<"线长："<<Length()<<endl;}int main(){Point ps(-2,5),pe(7,9);Line l(ps,pe);cout<<"关于直线："<<endl;l.PrintLine();  //输出直线l的信息：两端点及长度cout<<"中点是：";l.PrintPoint(); //输出直线l中点的信息cout<<endl;return 0;}

运行结果：