重载单目运算符前置后置问题

#include<iostream>
using namespace std;
class complex
{
public:
	complex(int a = 0, int b = 0) :real(a), imag(b) {}
	complex operator++();//前置
	complex operator++(int);//后置
	friend ostream&operator << (ostream&, complex&);
	friend istream& operator >>(istream&, complex&);
private:
	int real, imag;
};
complex complex::operator++(int) {
	return complex(real++, imag++);

}
complex complex::operator++() {
	/*real++;
	imag++;
	return *this;*/
	return complex(++real, ++imag);
}
	ostream& operator<<(ostream& output, complex& c){
	output << c.real << "." << c.imag << endl;
	return output;
	}
	istream& operator>>(istream& input, complex& c) {
		input >> c.real >> c.imag;
		return input;
	
	}
	int main() {
		complex c1,c2;
		cin >> c1;
		cout << c1;
		c2 = ++c1;
		cout<<c2<<endl;
		cout << c1;
		c1++;
		cout << c1;
		return 0;
	
	}

输入

1
2

输出：

1.2
2.3

2.3
3.4