利用友元函数，重载运算符

上机目的：练习友元函数，重载运算符

我的程序：

/*  
* 程序的版权和版本声明部分:   
* 作    者：烟台大学计算机学院学生：段元晋
* 完成日期：2013年4月19日
* 版 本 号：vc++6.0
* 对任务及求解方法的描述部分: 
* 输入描述：无
* 问题描述：略
* 程序输出：略
* 问题分析：略 
* 算法设计：略  
*/    
#include<iostream.h>
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;  
};
Complex operator+(Complex &c1,Complex &c2)
{
	return Complex(c1.real+c2.real,c1.imag+c2.imag);
}
Complex operator-(Complex &c1,Complex &c2)
{
	return Complex(c1.real-c2.real,c1.imag-c2.imag);
}
Complex operator*(Complex &c1,Complex &c2)
{
	return Complex(c1.real*c2.real,c1.imag*c2.imag);
}
Complex operator/(Complex &c1,Complex &c2)
{
	return Complex(c1.real/c2.real,c1.imag/c2.imag);
}

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();  
    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;  
}

运行结果：