1. 运算符重载为成员函数（单目运算符重载）

#include<iostream>
using  namespace  std;
class  complex
{
public:
        complex(double  r  =  0.0,  double  i  =  0.0)  {  real  =  r;  imag  =  i;  }
        complex  operator  +  (complex  c2);        //+重载为成员函数
        complex  operator  -  (complex  c2);          //-重载为成员函数
        void  display();        //输出复数
private:
        double  real;        //复数实部
        double  imag;        //复数虚部
};
//重载函数实现
complex  complex::operator  +(complex  c2)
{
  complex tmp;
    tmp.real = c2.real + real;
    tmp.imag = c2.imag + imag;
    return tmp;

}
//重载函数实现
complex  complex::operator  -(complex  c2)
{
 complex tmp;
    tmp.real =  real- c2.real ;
    tmp.imag =  imag - c2.imag;
    return tmp;

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

int  main()
{
        complex  c1(5,  4),  c2(2,  10),  c3;
        cout  <<  "c1=";  c1.display();
        cout  <<  "c2=";  c2.display();
        c3  =  c1  -  c2;        //使用重载运算符完成复数减法
        cout  <<  "c3=c1-c2=";
        c3.display();
        c3  =  c1  +  c2;        //使用重载运算符完成复数加法
        cout  <<  "c3=c1+c2=";
        c3.display();
}