由點到面再到體

/** 程式的著作權和版本聲明部分* Copyright (c)2013, 煙台大學電腦學院學生.* All rightsreserved.* 作    者：   劉明亮* 完成日期： 2013 年 5 月 12 日* 版本號碼： v1.0* 輸入描述：* 問題描述：* 輸出：*/#include<iostream>#include<iomanip>#include <Cstring>#define PI 3.1415using namespace std;class Point{public:    Point(double xx,double yy):x(xx),y(yy){};    friend ostream &operator<<(ostream&output,Point&);    double x,y;};ostream& operator<<(ostream&output,Point& e){    output<<"("<<e.x<<","<<e.y<<")";    return output;}class Circle:public Point{private:    double r;public:    Circle(double a,double b,double R):Point(a,b),r(R) {}    double get_r() const {return r;}    friend ostream &operator<<(ostream &output,const Circle &c);    double area() const;};double Circle::area() const{    return r*r*PI;}ostream &operator<<(ostream &output,const Circle &c){    output<<"Center=["<<c.x<<", "<<c.y<<"], r="<<c.r<<", area="<<c.area()<<endl;    return output;}class Cylinder:public Circle{private:    double h;public:    Cylinder(double a,double b,double R,double H):Circle(a,b,R),h(H){}    friend ostream &operator<<(ostream &output,const Cylinder& cy);    double volume() const;    double Carea() const;};ostream &operator<<(ostream &output,const Cylinder& cy){    output<<"Center=["<<cy.x<<","<<cy.y<<"], r="<<cy.get_r()<<", h="<<cy.h    <<"\narea="<<cy.Carea( )<<", volume="<<cy.volume()<<endl;    return output;}double Cylinder::volume() const{    return area()*h;}double Cylinder::Carea() const{    return 2*area()+(2*PI*get_r())*h;}int main(){    Cylinder cy1(3.4,4.3,4.2,10);    cout<<cy1<<endl;    return 0;}