c++知识复习

1.类

在C++中，一般将类的声明放在头文件，将类的实现放在源程序文件中

//rectangle.h#ifndef __RECTANGLE_H__   #define __RECTANGLE_H__//上两句话意思是若未定义__RECTANGLE_H__,则定义class Rectangle{private:    int length, width,height;public:    //构造函数    Rectangle(int len, int wd, int ht) :length(len), width(wd), height(ht){}    //析构函数    virtual ~Rectangle(){}    int Volume() const;};#endif//rectangle.cpp#include"rectangle.h"int Rectangle::Volume() const{    return length*width*height;}//main.cpp#include<iostream>using namespace std;#include"rectangle.h"//提供类Rectangle的声明int main(){    Rectangle thisRectangle(6, 8, 9);    int volume = 0;    volume = thisRectangle.Volume();    cout << volume << endl;    return 0;}

2.运算符重载

运算符重载有两种方式
①将运算符重载为全局函数，这种情况下可声明为友元，以便引用类的私有成员，如+重载如下

friend Complex operator+(const Complex&a,const Complex &b)

②将运算符重载为类的成员函数，此时对象自己成了左侧的参数，所以单目运算符没有参数，双目运算符只有一个右侧参数，如-重载

friend Complex operator-(const Complex&a)

实例如下

//complex.h#ifndef __COMPLEX_H__   #define __COMPLEX_H__class Complex{private:    double realPart,imagePart;//复数的实部与虚部public:    //构造函数    Complex(double rp=0,double ip=0) :realPart(rp), imagePart(ip){}    //析构函数    virtual ~Complex(void){};    double GetRealPart() const { return realPart; }    double GetImagePart() const { return imagePart; }    void SetRealPart(double rp) { realPart = rp; }    void SetImagePart(double ip){ imagePart = ip; }    void Show() const;    Complex operator -(const Complex &a);//重载为成员函数};void Complex::Show() const{    cout << realPart;    if (imagePart < 0 && imagePart != -1)cout << imagePart << "i" << endl;    else if (imagePart == -1) cout << "-i" << endl;    else if (imagePart > 0 && imagePart != -1)cout << "+" << imagePart << "i" << endl;    else if (imagePart == 1) cout << "+i" << endl;}Complex operator+(const Complex &a, const Complex &b){//作为全局函数的加法重载    Complex c;    c.SetRealPart(a.GetRealPart() + b.GetRealPart());    c.SetImagePart(a.GetImagePart() + b.GetImagePart());    return c;}Complex Complex::operator-(const Complex &a){//作为成员函数重载    Complex c;    c.realPart=realPart-a.realPart;    c.imagePart=imagePart-a.imagePart;    return c;}#endif//main.cpp#include<iostream>using namespace std;#include"complex.h"int main(){    Complex z1(6, 8);    z1.Show();    Complex z2(8, 9);    z2.Show();    Complex z3;    z3 = z1 + z2;    z3.Show();    Complex z4;    z4 = z2 - z1;    z4.Show();    return 0;}