运算符重载++

#include <iostream>
using namespace std ;
class coplex
{
public:
coplex(int x=0,int y=0);
coplex(coplex& tem);
coplex& operator ++();
coplex& operator ++(int);
friend ostream& operator<< (ostream& os, coplex& cp);//这种只能重在为友元函数
private:
int a;
int b;
};


coplex::coplex(int x, int y)
{
a = x;
b = y;
}
coplex::coplex(coplex& tem){
a = tem.a;
b = tem.b;
}
coplex& coplex::operator++(){
this->a++;
this->b++;
return *this;
}
coplex& coplex::operator++(int){
//多了一个int型占位符（只能是int型，不能是别的，如float)，用来区分前置++，
//系统已经定义好：带int型占位符的是后置++，不带的是前置++，要顺从，不要多想。
coplex *tem = new coplex(*this);
++(*this); //利用已经定义的前置++函数实现
return *tem;
}
ostream& operator<< (ostream& os, coplex& cp){
os << cp.a<<"  "<<cp.b << endl;
return os;
}
int main(){
coplex a(1, 2);
coplex b(2, 3);
cout << a << b<<endl;
cout << a++<< endl;
cout <<++b << endl;
cout << a << b << endl;
system("pause");
return 0;
}