C++运行符重载、友元函数

Complex.h

 #pragma once
 #include <iostream>

 using namespace std;
 //表示一个复数
 class Complex
 {
 private:
     double x, y;
 public:
     Complex();    //默认构造函数
     Complex(double x, double y); //构造函数重载
     Complex operator+(Complex & cmx) const; //'+'号运算符重载
     Complex operator-(Complex & cmx) const;    //'-'号运算符重载
     Complex operator*(Complex & cmx) const;    //'*'号运算符重载
     Complex operator/(Complex & cmx) const;    //'/'号运算符重载
     Complex operator~() const;    //'~'号运算符重载
     Complex operator*(double & n) const; //'*'号运算符重载
     friend Complex operator*(double & n, Complex & cmx); //友元函数,可用于表示[4.0*Complex类型]
     friend ostream & operator<<(ostream & os, Complex & cmx); //友元函数,可用于表示[cout << Complex类型]
 ~Complex();
 };

Complex.cpp

 #include "Complex.h"

 Complex::Complex()
 {
 }

 Complex::Complex(double x, double y)
 {
     this->x = x;
     this->y = y;
 }

 Complex Complex::operator+(Complex & cmx) const
 {
     return Complex(x + cmx.x, y + cmx.y);
 }

 Complex Complex::operator-(Complex & cmx) const
 {
     return Complex(x - cmx.x, y - cmx.y);
 }

 Complex Complex::operator*(Complex & cmx) const
 {
     return Complex(x*cmx.x, y*cmx.y);
 }

 Complex Complex::operator/(Complex & cmx) const
 {
     return Complex(x / cmx.x, y / cmx.y);
 }

 Complex Complex::operator~() const
 {
     return Complex(x, -y);
 }

 Complex Complex::operator*(double & n) const
 {
     return Complex(x*n, y*n);
 }

 Complex operator*(double & n, Complex & cmx)
 {
     return cmx*n;
 }

 ostream & operator<<(ostream & os, Complex & cmx)
 {
     os << cmx.x << "," << cmx.y << endl;
     return os;
 }

 Complex::~Complex()
 {
 }