**#include <iostream> #include <strings.h> #include <cstring>using namespace std; class Point { public:Point(float x=0,float y=0); //輸入帶有默認參數的構造函數void setPoint(float,float); //設置坐標值float getX()const{return x;} //讀入xfloat getY()const{return y;} //定義讀入y值的常函數friend ostream & operator<<(ostream &,const Point &); //重載運算符“<<” protected:float x,y; };//下面定義Point類的成員函數 Point::Point(float a, float b) // 對x,y進行初始化{x=a;y=b;} void Point::setPoint(float a, float b) { //對x,y賦新值x=a;y=b; } ostream & operator <<(ostream &output,const Point &p) {output <<"["<<p.x<<","<<p.y<<"]"<<endl;return output; }int main() {Point p(3.5,6.4);cout<<"x="<<p.getX()<<",y="<<p.getY()<<endl;p.setPoint(8.5,6.8);cout<<"p(new):"<<p<<endl; }** **/home/andrew/文檔/Clion/untitled5/cmake-build-debug/untitled5 x=3.5,y=6.4 p(new):[8.5,6.8]Process finished with exit code 0 **

函數說明，建立一個典型的例子；
一步一步的增加內容以免調試程序出現錯誤無法糾正

**#include <iostream> #include <strings.h> #include <cstring>using namespace std; class Point { public:Point(float x=0,float y=0); //輸入帶有默認參數的構造函數void setPoint(float,float); //設置坐標值float getX()const{return x;} //讀入xfloat getY()const{return y;} //定義讀入y值的常函數friend ostream & operator<<(ostream &,const Point &); //重載運算符“<<” protected:float x,y; };//下面定義Point類的成員函數 Point::Point(float a, float b) // 對x,y進行初始化{x=a;y=b;} void Point::setPoint(float a, float b) { //對x,y賦新值x=a;y=b; }class Circle:public Point { public:Circle(float x=0,float y=0,float r=0);void setRadius(float); //設置半徑值float getRadius()const; //定義常成員函數float area()const;friend ostream &operator<<(ostream &,const Circle &); private:float radius;}; Circle::Circle(float a, float b, float r):Point(a,b),radius(r) {} //設置半徑 void Circle::setRadius(float r) {radius=r; } float Circle::getRadius() const {return radius;} float Circle::area() const {return 3.1415926*radius*radius; } ostream & operator <<(ostream &output,const Circle &c) {output <<"Center=["<<c.x<<","<<c.y<<"],r="<<c.radius<<",area="<<c.area()<<endl;return output; }int main() {Circle c(3.5,6.4,5.2);cout<<"original circle :\nx="<<c.getX()<<",y="<<c.getY()<<",r="<<c.area()<<endl;return 0; }** **/home/andrew/文檔/Clion/untitled5/cmake-build-debug/untitled5 original circle : x=3.5,y=6.4,r=84.9487Process finished with exit code 0 **

總結

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