c++primer plus 第11章 编程题第7题

#pragma once
#ifndef COMPLEX0_H_
#define COMPLEX0_H_
#include<iostream>

class Complex
{
private:
    double real;
    double imgn;
public:
    Complex();
    Complex(double a, double b);
    ~Complex();
    Complex operator+(const Complex & a) const;
    Complex operator-(const Complex & a) const;
    Complex operator~();
    Complex operator*(double c);
    Complex operator*(const Complex & a) const;

    //friend
    friend Complex operator*(const double c, const Complex & a);
    friend std::ostream & operator<<(std::ostream & os, const Complex &a);//operator后面别打空格
    friend std::istream & operator>>(std::istream & os, Complex &a);//cin是在istream里

};

#endif // !COMPLEX0_H_

//总结，如果在第二个构造函数里写了double n =0， double b = 0；就不用写complex（），两个是等价的，会存在歧义
//所以尽量不要在构造函数参数里写 = 0；因为会产生歧义，老实用complex（）和第二个构造函数就好
//凡是不用改变的都设成const---------------------------------

#include"complex0.h"

Complex::Complex()
{
    real = imgn = 0;
}

Complex::Complex(double n1, double n2)
{
    real = n1;
    imgn = n2;
}

Complex Complex::operator+(const Complex & a) const
{
    Complex temp;
    temp.real = real + a.real;
    temp.imgn = imgn + a.imgn;
    return temp;
    /*return Complex(real + a.real, imgn + a.imgn);*///直接调用构造函数//要习惯于用这个简化语句
    //一般就用最后一条语句，等价于前面三条，调用构造函数会产生一个临时对象，赋值给左边
}

Complex Complex::operator-(const Complex & a) const
{
    Complex temp;
    temp.real = real - a.real;
    temp.imgn = imgn - a.imgn;
    return temp;
}

Complex Complex::operator*(const Complex & a) const
{
    Complex temp;
    temp.real = real * a.real + imgn * a.imgn;
    temp.imgn = real * a.imgn + imgn * a.real;
    return temp;
}

Complex Complex::operator~()
{
    imgn = 0 - imgn;
    return *this;
}

Complex Complex::operator*(double c)
{
    return Complex(c * real, c * imgn);
}
//friend
Complex operator*(const double c, const Complex & a)//别打：：因为友元不在类里面，虽然是在类里面声明
{
    return Complex(c * a.real, c * a.imgn);
}

std::ostream & operator<< (std::ostream & os, const Complex &a)
{
    os << "is " << "( " << a.real << ", " << a.imgn << "i )";
    return os;
}
std::istream & operator >> (std::istream & os, Complex & a)//cin在istream里
{
    std::cout << "real: ";
    os >> a.real;
    std::cout << "imaginary: ";
    os >> a.imgn;
    return os;

}
Complex::~Complex()
{

}

原文地址：https://www.cnblogs.com/syne-cllf/p/9240615.html