Лабораторная работа. Классы. Передача объекта в качестве аргумента.

#include <iostream>
class Complex {
public:
constexpr Complex(const double& real = 0, const double& imag = 0) : real_(real), imag_(imag) {}
Complex add(const Complex& c) {
return Complex(real_ + c.real_, imag_ + c.imag_);
}
Complex sub(const Complex& c) {
return Complex(real_ - c.real_, imag_ - c.imag_);
}
Complex mul(const Complex& c) {
return Complex(real_ * c.real_ - imag_ * c.imag_, real_* c.imag_ + c.real_ * imag_);
}
Complex div(const Complex& c) {
auto aa = real_ * real_;
auto bb = imag_ * imag_;
auto cc = c.real_ * c.real_;
auto dd = c.imag_ * c.imag_;
auto ac = real_ * c.real_;
auto bd = imag_ * c.imag_;
auto bc = imag_ * c.real_;
auto ad = real_ * c.imag_;
return Complex((ac + bd) / (cc + dd), (bc - ad) / (cc + dd));
}
bool equ(const Complex& c) {
return real_ == c.real_ && imag_ == c.imag_;
}
bool conj(const Complex& c) {
int a = imag_ < 0 ? -1 : 0;
int b = c.imag_ < 0 ? -1 : 0;
return equ(c) && a != b;
}
void read() {
std::cout << "a: ";
std::cin >> real_;
std::cout << "b: ";
std::cin >> imag_;
}
void display() {
std::cout << real_ << (imag_ < 0 ? " - " : " + ") << imag_ << 'i';
}
private:
double real_;
double imag_;
};

P.S. Внешние функции сами придумаете.