友元函数编写运算符重载

/*
*烟台大学计算机学院
*文件名称：main.cpp
*作    者：王者健
*完成日期：2016年6月15日
*版 本 号：codeblocks 16.01
*问题描述：
*输入描述：
*程序输出：
*/
#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);
void display();
private:
double real;
double imag;
};
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;
}

void Complex::display()
{
cout<<real<<","<<imag<<"i"<<endl;
}

int main()
{
Complex c1(3,4),c2(5,-10),c3;
cout<<"c1=";
c1.display();
cout<<"c2=";
c2.display();
cout<<"c1+c2=";
c3=c1+c2;
c3.display();
cout<<"c1-c2=";
c3=c1-c2;
c3.display();
return 0;
}