继承Circle类

/*
 Copyright(c)2016,烟台大学计算机与控制工程学院
 All rights reserced
 文件名称：test.cpp
 作    者：高玉杰
 完成日期：2016年6月8日
 版 本 号：v1.0
 问题描述：增加半径R，求表面积
 输入描述：半径
 程序输出：表面积

*/

#include <iostream>
using namespace std;
class Point
{
public:
    Point(double x=0,double y=0);                   
    void setPoint(double,double);                 
    double getX( ) const
    {
        return x;   //读x坐标
    }
    double getY( ) const
    {
        return y;   //读y坐标
    }
    void show();
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;
}

void Point::show()
{
    cout<<"["<<x<<","<<y<<"]"<<endl;
}

class Circle:public Point   

<span style="font-family: Arial, Helvetica, sans-serif;">{</span>

public:
    Circle(double x=0,double y=0,double r=0);  
    void setRadius(double);                  
    double getRadius( ) const;               
    double area ( ) const;                  
    void show();
protected:
    double radius;
};


Circle::Circle(double a,double b,double r):Point(a,b),radius(r) { }


void Circle::setRadius(double r)
{
    radius=r;
}


double Circle::getRadius( ) const
{
    return radius;
}


double Circle::area( ) const
{
    return 3.14159*radius*radius;
}


void Circle::show()
{
    cout<<"Center=["<<x<<", "<<y<<"], r="<<radius<<", area="<<area( )<<endl;
}

int main( )
{
    Circle c(3.5,6.4,5.2);
    cout<<"original circle:\n";
    c.show();
    c.setPoint(5,5);
    cout<<"new circle:\n";
    c.show();
    return 0;
}