单目运算符能不能用友元重载

void operator ++();前置
void operator ++(int);后置
我觉得没必要重载为友元。。

#include"iostream.h"
//using namespace std;
class Complex
{
private:
    float real;
    float imag;
public:
    Complex(){}
    Complex(float r,float t)
    {
        this->real=r;
        this->imag=t;
    }
    void print();
    friend Complex operator ++(Complex&);
};
void Complex::print()
{
    cout<<"c ="<<real<<"+"<<imag<<"i"<<endl;
}
Complex operator ++(Complex&a)
{
    return Complex (a.real++,a.imag++);
}
int main()
{
    Complex a(1,1),d(0,0);
    d=a++;
    a.print();
    d.print();
    d=++a;
    d.print();
    a.print();    
    return 0;
    
}
不知道它是怎么重载的 但是 前置后置可以。。