继承与多态

#include <iostream>using namespace std;//声明类Pointclass Point{public:    Point(float x = 0, float y = 0); //构造函数    void setPoint(float, float);//设置x\y坐标值    float getX() const { return x; }//getX是Point 类中的常成员函数,可以引用,但不能修改本类的数据成员    float getY() const { return y; }    friend ostream &operator << (ostream &, const Point &);//重载<<protected:    float x, y;};//定义point类的成员函数//Point 构造函数Point::Point(float a, float b){    x = a; y = b;}//设置x\y坐标值void Point::setPoint(float a, float b){    x = a; y = b;}//重载<<ostream& operator << (ostream &output, const Point &p){    output << "[" << p.x << "," <<p.y<< "]" << endl;    return output;}////分步调试//int main()//{//  Point p(2.5, 6.4);//  cout << "x=" << p.getX() << ".y=" << p.getY() << endl;//  p.setPoint(8.8, 6.6);//  cout << "p(new):" << p << endl;//}class Circle :public Point{public:    Circle(float x = 0, float y = 0, float r = 0);    void setRadius(float);    float getRadius() const;    float area() const;    friend ostream &operator <<(ostream &, const Circle &);protected:    float radius;};//定义构造函数,派生类函数初始化Circle::Circle(float a, float b, float r) :Point(a, b), radius(r){}void Circle::setRadius(float r){    radius = r;}float  Circle::getRadius()const { return radius; }float Circle::area() const { return 3.14158*radius*radius; }ostream &operator <<(ostream &output, const Circle &c){    output << "center = [" << c.x << "," << c.y << "] , r = " << c.radius << ", area = " << c.area() << endl;    return output;}//分步调试//int main()//{//  Circle c(2.5, 6.4, 5.2);//  cout << "original circle:\n x = " << c.getX() << ",y = " << c.getY() << ", r= " << c.getRadius() << ", area = " << c.area() << endl;//  c.setRadius(7.5);//  c.setPoint(5, 5);////  cout << "new circle:\n" << c;//  Point &pRef = c;//pRef 是point类的引用变量,被c初始化;//  cout << "pRef:" << pRef;//输出pRef//调用Point<<//  return 0;//}class Cylinder:public Circle{public:    Cylinder(float x = 0, float y = 0, float r = 0, float h = 0);    void setHeight(float);    float getHeight() const;    float area() const;//圆表面积    float volume() const;//圆柱体积    friend ostream &operator << (ostream &, const Cylinder&);protected:    float heigth;};Cylinder::Cylinder(float a, float b, float r, float h) :Circle(a, b, r), heigth(h){}void Cylinder::setHeight(float h){ heigth = h; } float Cylinder::getHeight() const { return heigth; }float Cylinder::area() const { return 2 * Circle::area() + 2 * 3.14159*radius*heigth; }float Cylinder::volume() const { return Circle::area()*heigth; }ostream &operator <<(ostream &output, const Cylinder & cy){    output << "center = [ " << cy.x << "," << cy.y << "],r = " << cy.radius << ".h = " << cy.heigth << "\n area = " << cy.area()        << ", volume = " << cy.volume() << endl;    return output;}int main(){    Cylinder  cy1(3.5, 6.4, 5.2, 10);    cy1.setHeight(15);    cy1.setRadius(7.5);    cy1.setPoint(5, 5);    cout << "\n new cylinder:\n" << cy1;    Point &pRef = cy1;    cout << "\npRef as a Point :" << pRef;    Circle &cRef = cy1;    cout << "\ncRef as a Circle:" << cRef;    return 0;}