定义Point(点)类，由Point类派生出Circle(圆)类，再由Circle类派生出Cylinder(圆柱体)类。将类的定义部分分别作为3个头文件，对它们的成员函数的声明部分分别作为3个源文件(.cpp文件)，在主函数中用#include命令把它们包含进来，形成一个完整的程序，并上机运行。
头文件1：
#ifndef POINT_H
#define POINT_H
#include <iostream>
using namespace std;
class Point
{
public:
Point(float =0,float =0);
void setPoint(float,float);
float getX() const{return x;}
float getY() const{return y;}
friend ostream &operator<<(ostream &,const Point &);
protected:
float x,y;
};
#endif头文件2：
#ifndef CIRCLE_H
#define CIRCLE_H
#include"point.h"
using namespace std;
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;
};
#endif
头文件3：
#ifndef CYLINDER_H
#define CYLINDER_H
#include<iostream>
#include"circle.h"
using namespace std;
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;
float volume() const;
friend ostream&operator<<(ostream&,const Cylinder&);
protected:
float height;
};
#endif
源文件1：
#include"point.h"
Point::Point(float a,float b)
{
x=a;
y=b;
}
void Point::setPoint(float a,float b)
{
x=a;
y=b;
}
ostream &operator<<(ostream &output,const Point &p)
{
output<<"["<<p.x<<","<<p.y<<"]"<<endl;
return output;
}源文件2
#include"circle.h"
#include<iostream>
using namespace std;
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 3.14159*radius*radius;
}
ostream &operator<<(ostream &output,const Circle &c)
{
output<<"Center=["<<c.x<<","<<c.y<<"],r="<<c.radius<<",area="<<c.area()<<endl;
return output;
}
源文件3：
#include"cylinder.h"
#include<iostream>
Cylinder::Cylinder(float a,float b,float r,float h)
:Circle(a,b,r),height(h){
}
void Cylinder::setHeight(float h)
{
height=h;
}
float Cylinder:: getHeight() const{return height;}
float Cylinder::area() const{
return 2*Circle::area()+2*3.14159*radius*height;};
float Cylinder::volume() const
{
return Circle::area()*height;
};
ostream&operator<<(ostream&output,const Cylinder&cy)
{
output<<"Center=["<<cy.x<<","<<cy.y<<"],r="<<cy.radius<<",h="<<cy.height
<<"\narea="<<cy.area()<<",volume="<<cy.volume()<<endl;
return output;
}主函数：
#include <iostream>
#include"point.h"
#include"circle.h"
#include"cylinder.h"
using namespace std;
int main()
{
Cylinder cy1(3.5,6.4,5.2,10);
cout<<"original cylinder:\nx="<<cy1.getX()<<",y="<<cy1.getY()<<",r="<<cy1.getRadius()<<",h="
<<cy1.getHeight()<<"\narea="<<cy1.area()<<",volume="<<cy1.volume()<<endl;
cy1.setHeight(15);
cy1.setRadius(7.5);
cy1.setPoint(5.5,6.4);
cout<<"\nnew cylinder:\n"<<cy1;
Point &pRef=cy1;
cout<<"\npRef as a point:"<<pRef;
Circle &cRef=cy1;
cout<<"\ncRef as a Circle:"<<cRef;
return 0;
}
original cylinder: x=3.5,y=6.4,r=5.2,h=10 area=496.623,volume=849.486 new cylinder: Center=[5.5,6.4],r=7.5,h=15 area=1060.29,volume=2650.72 pRef as a point:[5.5,6.4] cRef as a Circle:Center=[5.5,6.4],r=7.5,area=176.714 -------------------------------- Process exited after 0.1994 seconds with return value 0 请按任意键继续. . .