第十三周项目1--点、圆的关系

/*Copyright(C) 烟台大学计算机与控制工程学院作者：刘慧艳完成日期：2014.05.24版本号：V1.1项目名：点、圆的关系问题描述：（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)，基类的成员表示圆心；（3）编写上述两类中的构造、析构函数及必要运算符重载函数     （本项目主要是输入输出）；（4）定义友元函数int locate，判断点p与圆的位置关系     （返回值<0圆内，==0圆上，>0 圆外）；*/#include <iostream>#include<Cmath>using namespace std;class Point{    public :    Point(double a=0,double b=0):x(a),y(b){}//构造函数    double distance(const Point &p)const;//计算距离    friend ostream & operator <<(ostream &,const Point &);//重载运算符“<<"    protected :     double x,y;};double Point ::distance (const Point &p)const//求距离{    double dx=x-p.x;    double dy=y-p.y;    return sqrt(dx*dx+dy*dy);}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 a=0,double b=0,double r=0):Point(a,b),radius(r){};//构造函数    friend ostream &operator<<(ostream &,const Circle &);//重载运算符“<<”    friend int locate(const Point &p, const Circle &c); //判断点p在圆上、圆内或圆外，返回值：<0圆内，==0圆上，>0 圆外protected:    double radius;};ostream &operator<<(ostream &output,const Circle &c){    output<<"Center=["<<c.x<<", "<<c.y<<"], r="<<c.radius<<endl;    return output;}//判断点p在圆内、圆c内或圆c外int locate(const Point &p, const Circle &c){    const Point cp(c.x,c.y); //圆心    double d = cp.distance(p);    if (abs(d - c.radius) < 1e-7)        return 0;  //相等    else if (d < c.radius)        return -1;  //圆内    else        return 1;  //圆外}int main( ){    Circle c1(3,2,4);    Point p1(1,1),p2(3,-2),p3(7,3);  //分别位于c1内、上、外    cout<<"圆c1: "<<c1;    cout<<"点p1: "<<p1;    cout<<"点p1在圆c1之"<<((locate(p1, c1)>0)?"外":((locate(p1, c1)<0)?"内":"上"))<<endl;    cout<<"点p2: "<<p2;    cout<<"点p2在圆c1之"<<((locate(p2, c1)>0)?"外":((locate(p2, c1)<0)?"内":"上"))<<endl;    cout<<"点p3: "<<p3;    cout<<"点p3在圆c1之"<<((locate(p3, c1)>0)?"外":((locate(p3, c1)<0)?"内":"上"))<<endl;    return 0;}