重载成员函数只能有一个参数吗？

Question

重载成员函数只能有一个参数吗？我写的operator-中写一个参数是对的，写了两个参数就是说参数太多了

#include <iostream>
using namespace std;
class complex {
public:
    double real, imag;
    complex(double r=0.0,double i=0.0):real(r),imag(i){}
    complex operator-(complex& a,complex &e);
    
};
complex operator+(complex& b, complex& c) {
    return complex(b.real + c.real, b.imag + c.imag);
}
complex complex::operator-(complex& a,complex &e) {
    return complex(real - a.real+e.real, imag - a.imag+e.imag);
}
int main() {
    complex a(4.0, 6), b(5, 9), c,e(1,2);
    c = a - b-e;
    cout << c.real << "," << c.imag << endl;
    cout << (a + b).real << "," << (a + b).imag << endl;
}

Answer 1

二元运算符，作为成员函数，被自身对象调用，所以当括号有两个参数，加上自身就是3个参数了。如果非要用两个参数，请用友元函数。

Answer 2

#include <iostream>
using namespace std;
class complex {
public:
    double real, imag;
    complex(double r = 0.0, double i = 0.0) :real(r), imag(i) {}
    complex operator-(complex& a);

};
complex operator+(complex& b, complex& c) {
    return complex(b.real + c.real, b.imag + c.imag);
}
complex complex::operator-(complex& a) {
    return complex(this->real - a.real,this->imag - a.imag);
}
int main() {
    complex a(4.0, 6), b(5, 9), c, e(1, 2);
    c = a - b - e;
    cout << c.real << "," << c.imag << endl;
    cout << (a + b).real << "," << (a + b).imag << endl;
}