重载乘法运算符

我正在为我的 c++ 类做作业。我们不得不重载几个运算符，例如 +、-, !=、= 等。好吧，除了乘法之外，我已经弄清楚了所有这些。我尝试过的所有内容都会溢出或无法编译。不知道我需要什么。

这是保存我的重载的头文件。

#ifndef COMPLEXNUMBER_H
#define COMPLEXNUMBER_H
#include<iostream>
using namespace std;
class ComplexNumber{
public:
    double real, imaginary;
    ComplexNumber(){
        real = 0;
        imaginary = 0;
    }
    ComplexNumber(double a, double b){
        real = a;
        imaginary = b;
    }
    ComplexNumber(double a){
        real = a;
        imaginary = 0;
    }
    ComplexNumber & operator= (const ComplexNumber & rhs){
        if(this == &rhs){
            return *this;
        }
        else{
            real = rhs.imaginary;
            imaginary = rhs.imaginary;
        }
        return *this;
    }
    ComplexNumber & operator+= (const ComplexNumber &rhs){
        real += rhs.real;
        imaginary += rhs.imaginary;
        return *this;
    }
    ComplexNumber & operator-= (const ComplexNumber &rhs){
        real -= rhs.real;
        imaginary -= rhs.imaginary;
        return *this;
    }
    const ComplexNumber operator+ (const ComplexNumber &rhs){
        ComplexNumber result = *this;
        result += rhs;
        return result;
    }
    const ComplexNumber operator- (const ComplexNumber &rhs){
        ComplexNumber result = *this;
        result -= rhs;
        return result;
    }
    const ComplexNumber operator* (const ComplexNumber &rhs){
        return *this * rhs;
    }
    friend ostream & operator<< (ostream &out, const ComplexNumber &c){
        out << "(" << c.real << (c.imaginary<0?" - ":" + ") << abs(c.imaginary) << " i)";
        return out;
    }
    friend istream & operator>> (istream & in, ComplexNumber &c){
        in >> c.real >> c.imaginary;
        return in;
    }
    operator double(){
        return real;
    }
    bool operator== (const ComplexNumber & rhs) const {
        bool result = (this->real == rhs.real) && (this->imaginary == rhs.imaginary);
        return result;
    }
    bool operator!= (const ComplexNumber &rhs) const{
        return !(*this == rhs);
    }
};
#endif

我知道乘法运算符很遥远，但它只是我目前所拥有的。在这里，它靠自己。任何想法将不胜感激！！

const ComplexNumber operator* (const ComplexNumber &rhs){
            return *this * rhs;
        }