C++多态性

概述一、运算符重载 将双目运算符重载为成员函数： #include <iostream>using namespace std;class Complex {public: Complex(double r = 0.0, double i = 0.0) : real(r), imag(i) { } //运算符+重载成员函数 Complex operator

一、运算符重载

将双目运算符重载为成员函数：

#include <iostream>using namespace std;class Complex {public:    Complex(double r = 0.0,double i = 0.0) : real(r),imag(i) { }    //运算符+重载成员函数    Complex operator + (const Complex &c2) const;    //运算符-重载成员函数    Complex operator - (const Complex &c2) const;    voID display() const;   //输出复数private:    double real;    //复数实部    double imag;    //复数虚部};Complex Complex::operator+(const Complex &c2) const{    //创建一个临时无名对象作为返回值     return Complex(real + c2.real,imag + c2.imag);}Complex Complex::operator-(const Complex &c2) const{    //创建一个临时无名对象作为返回值    return Complex(real - c2.real,imag - c2.imag);}voID Complex::display() const {    cout << "(" << real << "," << imag << ")" << endl;}int main() {    Complex c1(5,4),c2(2,10),c3;    cout << "c1 = "; c1.display();    cout << "c2 = "; c2.display();    c3 = c1 - c2;   //使用重载运算符完成复数减法    cout << "c3 = c1 - c2 = "; c3.display();    c3 = c1 + c2;   //使用重载运算符完成复数加法    cout << "c3 = c1 + c2 = "; c3.display();    return 0;}

将单目运算符重载为成员函数：

为了在程序中区分前置运算符（前置++）和后置++，需要在后置++的参数列表里面加东西来区分。

#include <iostream>using namespace std;class Clock {//时钟类定义public:    Clock(int hour = 0,int minute = 0,int second = 0);    voID showTime() const;    //前置单目运算符重载    Clock& operator ++ ();    //后置单目运算符重载    Clock operator ++ (int);private:    int hour,minute,second;};Clock::Clock(int hour,int minute,int second) {    if (0 <= hour && hour < 24 && 0 <= minute && minute < 60        && 0 <= second && second < 60) {        this->hour = hour;        this->minute = minute;        this->second = second;    }    else        cout << "Time error!" << endl;}voID Clock::showTime() const {  //显示时间    cout << hour << ":" << minute << ":" << second << endl;}Clock & Clock::operator ++ () {    second++;    if (second >= 60) {        second -= 60;  minute++;        if (minute >= 60) {            minute -= 60; hour = (hour + 1) % 24;        }    }    return *this;}Clock Clock::operator ++ (int) {    //注意形参表中的整型参数    Clock old = *this;    ++(*this);  //调用前置“++”运算符    return old;}int main() {    Clock myClock(23,59,59);    cout << "First time output: ";    myClock.showTime();    cout << "Show myClock++:    ";    (myClock++).showTime();    cout << "Show ++myClock:    ";    (++myClock).showTime();    return 0;}

 运算符重载为非成员函数：

#include <iostream>using namespace std;class Complex {public:    Complex(double r = 0.0,imag(i) { }    frIEnd Complex operator+(const Complex &c1,const Complex &c2);    frIEnd Complex operator-(const Complex &c1,const Complex &c2);    frIEnd ostream & operator<<(ostream &out,const Complex &c);private:    double real;  //复数实部    double imag;  //复数虚部};Complex operator+(const Complex &c1,const Complex &c2){    return Complex(c1.real + c2.real,c1.imag + c2.imag);}Complex operator-(const Complex &c1,const Complex &c2){    return Complex(c1.real - c2.real,c1.imag - c2.imag);}ostream & operator<<(ostream &out,const Complex &c){    out << "(" << c.real << "," << c.imag << ")";    return out;}int main() {    Complex c1(5,c3;    cout << "c1 = " << c1 << endl;    cout << "c2 = " << c2 << endl;    c3 = c1 - c2;   //使用重载运算符完成复数减法    cout << "c3 = c1 - c2 = " << c3 << endl;    c3 = c1 + c2;   //使用重载运算符完成复数加法    cout << "c3 = c1 + c2 = " << c3 << endl;    return 0;}

 

二、虚函数

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