第十周实验报告（三.1）

1）先建立一个Point(点)类，包含数据成员x,y(坐标点)；
（2）以Point为基类，派生出一个Circle(圆)类，增加数据成员 (半径)；
（3）再以Circle类为直接基类，派生出一个Cylinder(圆柱体)类，再增加数据成员h(高)。
要求编写程序，设计出各类中基本的成员函数（包括构造函数、析构函数、修改数据成员和获取数据成员的公共接口、用于输出的重载运算符“<<”函数等），使之能用于处理以上类对象，最后求出圆格柱体的表面积、体积并输出。

（提示：此任务可以分为三个子任务分成若干步骤进行。先声明基类，再声明派生类，逐级进行，分步调试。——这种方法适用于做任何的项目）

#include <iostream>
using namespace std;
double const pi=3.1415926;
class Point
{
public:
	Point(double x=0,double y=0);
	void setPoint(double , double);
	double getX() const {return x;}
	double getY() const {return y;}
	friend ostream & operator << (ostream &,const Point &);
protected:
	double x,y;
};
Point::Point(double a, double b)
{
	x=a;
	y=b;
}
void Point::setPoint(double a, double b)
{
	x=a;
	y=b;
}
ostream & operator << (ostream &output,const Point &p)
{
	output<<"["<<p.x<<","<<p.y<<"]"<<endl;
	return output;
}
class Circle:public Point   //circle是Point类的公用派生类  
{  
public:  
    Circle(double x=0,double y=0,double r=0);  //构造函数  
    void setRadius(double);                  //设置半径值  
    double getRadius( ) const;               //读取半径值  
    double area ( ) const;                   //计算圆面积  
    friend ostream &operator<< (ostream &,const Circle &);//重载运算符“<<”  
protected:  
    double radius;  
};  
  
//定义构造函数，对圆心坐标和半径初始化  
Circle::Circle(double a,double b,double r):Point(a,b),radius(r){ }  
  
//设置半径值  
void Circle::setRadius(double r)  
{  
    radius=r;  
}  
  
//读取半径值  
double Circle::getRadius( ) const  
{  
    return radius;  
}  
  
//计算圆面积  
double Circle::area( ) const  
{  
    return pi*radius*radius;  
}  
  
//重载运算符“<<”，使之按规定的形式输出圆的信息  
ostream &operator<<(ostream &output,const Circle &c)  
{  
    output<<"Center=["<<c.x<<", "<<c.y<<"], r="<<c.radius<<", area="<<c.area( )<<endl;  
    return output;  
}  
class Cylinder:public Circle
{
public:Cylinder(double a=0,double b=0,double r=0,double h=0);
	   void setHigh(double);
	   double getHigh() const;
	   double volume() const;
	   friend ostream &operator<< (ostream &,const Cylinder &);//重载运算符“<<”
protected:
	double high;
};
Cylinder::Cylinder(double a,double b,double r,double h):Circle(a,b,r),high(h){ }
void Cylinder::setHigh(double h)
{
	high=h;
}
double Cylinder::getHigh() const
{
	return high;
}
double Cylinder::volume() const
{
	return pi*radius*radius*high;
}
ostream &operator<<(ostream &output,const Cylinder &d)  
{  
	output<<"Center=["<<d.x<<", "<<d.y<<"], r="<<d.radius<<", area="<<d.area( )<<",volume="<<d.volume( )<<endl;  
    return output;  
}   
int main( )  
{  
    Circle c(3.5,6.4,5.2);  
    cout<<"original circle:\nx="<<c.getX()<<", y="<<c.getY()<<", r="<<c.getRadius( ) <<", area="<<c.area( )<<endl;    
    c.setPoint(3.5,6.4);         
	cout<<"new circle:\n"<<c;
	Cylinder d(3.5,6.4,5.2,4.6);
	cout<<"original circle:\nx="<<d.getX()<<", y="<<d.getY()<<", r="<<d.getRadius( ) <<", area="<<d.area( )<<",volume="<<d.volume()<<endl;
	cout<<"new circle:\n"<<d;
	system("pause");  
    return 0;  
}  

original circle:
x=3.5, y=6.4, r=5.2, area=84.9487
new circle:
Center=[3.5, 6.4], r=5.2, area=84.9487
original circle:
x=3.5, y=6.4, r=5.2, area=84.9487,volume=390.764
new circle:
Center=[3.5, 6.4], r=5.2, area=84.9487,volume=390.764
请按任意键继续. . .