项目一之友元函数实现功能

#include <iostream>using namespace std;class Complex{    public:Complex(){real=0;imag=0;}Complex(double r,double i){real=r;imag=i;}friend Complex operator+(Complex &c1,Complex &c2);friend Complex operator-(Complex &c1,Complex &c2);friend Complex operator*(Complex &c1,Complex &c2);friend Complex operator/(Complex &c1,Complex &c2);void display(); private:double real;double imag;};//下面定义成员函数Complex operator+(Complex &c1,Complex &c2){    Complex c;    c.real=c1.real+c2.real;    c.imag=c1.imag+c2.imag;    return c;}Complex operator-(Complex &c1,Complex &c2){    Complex c;    c.real=c1.real-c2.real;    c.imag=c1.imag-c2.imag;    return c;}Complex operator*(Complex &c1,Complex &c2){    Complex c;    c.real=c1.real*c2.real-c1.imag*c2.imag;    c.imag=c1.imag*c2.real+c1.real*c2.imag;    return c;}Complex operator/(Complex &c1,Complex &c2){    Complex c;    c.real=(c1.real*c2.real+c1.imag*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);    c.imag=(c1.imag*c2.real-c1.real*c2.imag)/(c2.real*c2.real+c2.imag*c2.imag);    return c;}void Complex::display(){    cout<<"("<<real<<","<<imag<<"i)"<<endl;}//下面是测试函数int main(){Complex c1(3,4),c2(5,-10),c3;cout<<"c1=";c1.display();cout<<"c2=";c2.display();c3=c1+c2;cout<<"c1+c2=";c3.display();c3=c1-c2;cout<<"c1-c2=";c3.display();c3=c1*c2;cout<<"c1*c2=";c3.display();c3=c1/c2;cout<<"c1/c2=";c3.display();return 0;}