实验四

1.car

#ifndef BATTERY_H
#define BATTERY_H

class Battery{
    public:
        Battery(int batterySize0=70);
        int show();
        int batterySize;
};
#endif

#include "battery.h"

Battery::Battery(int batterySize0){
    batterySize=batterySize0;
}

int Battery::show(){
    return batterySize;
}

#ifndef CAR_H
#define CAR_H
#include <string>
#include <iostream>
using namespace std;

class Car{
    public:
        Car(string maker0,string model0,int year0,int odometer0=0):maker(maker0),model(model0),year(year0),odometer(odometer0){};
        friend ostream& operator<<(ostream &out,const Car &c);
        void updateOdometer(int newodometer);
        string maker,model;
        int year,odometer;
};
#endif

#include "car.h"
#include <string>
#include <iostream>
using namespace std;

ostream& operator<<(ostream &out,const Car &c){
    out<<"maker:"<<c.maker<<endl<<"model:"<<c.model<<endl<<"year:"<<c.year<<endl<<"odometer:"<<c.odometer<<endl;
    return out;
}

void Car::updateOdometer(int newodometer){
    if(newodometer<odometer)
        cout<<"Error updating"<<endl;
    else
        odometer=newodometer;
}

#ifndef ELECTRICCAR_H
#define ELECTRICCAR_H
#include "battery.h"
#include "car.h"
#include <string>
#include <iostream>

class ElectricCar:public Car,public Battery{
    public:
        ElectricCar(string maker1,string model1,int year1,int odometer1=0,int batterySize1=70):Car(maker1,model1,year1,odometer1),Battery(batterySize1){};
        friend ostream& operator<<(ostream &outCar,const ElectricCar &e);
        void updateOdometer(int newodometer1);
};
#endif

#include "electriccar.h"
#include "car.h"
#include "battery.h"
#include <iostream>
using namespace std;

ostream& operator<<(ostream &out,const ElectricCar &e){
    out << "maker:" << e.maker << endl << "model:" << e.model << endl << "year:" << e.year << endl << "odometer:" << e.odometer << endl << "batterySize:" << e.batterySize <<"-kWh" <<endl;
    return out;
}

void ElectricCar::updateOdometer(int newodometer1){
    if(newodometer1<odometer)
        cout<<"Error updating"<<endl;
    else
        odometer=newodometer1;
}

#include <iostream>
using namespace std;

#include "car.h"
#include "electriccar.h" 

int main() {
    // 测试Car类 
    Car oldcar("Audi","a4",2016);
    cout << "--------oldcar's info--------" << endl;
    oldcar.updateOdometer(25000);
    cout << oldcar << endl;

    // 测试ElectricCar类 
    ElectricCar newcar("Tesla","model s",2016);
    newcar.updateOdometer(2500);
    cout << "\n--------newcar's info--------\n"; 
    cout << newcar << endl;

    system("pause");
    
    return 0;
}

 

2.array

#ifndef ARRAY_INT_H
#define ARRAY_INT_H

class ArrayInt{
    public:
        ArrayInt(int n, int value=0);
        ~ArrayInt();
        // 补足:将运算符[]重载为成员函数的声明
        // ×××
        int & operator[](int a);
        void print(); 
    private:
        int *p;
        int size;
};

#endif

#include "arrayInt.h"
#include <iostream>
#include <cstdlib>
using std::cout;
using std::endl;

ArrayInt::ArrayInt(int n, int value): size(n) {
    p = new int[size];
    
    if (p == NULL) {
        cout << "fail to mallocate memory" << endl;
        exit(0); 
    } 
    
    for(int i=0; i<size; i++)
        p[i] = value;
}

ArrayInt::~ArrayInt() {
    delete[] p;
}

void ArrayInt::print() {
    for(int i=0; i<size; i++)
        cout << p[i] << " ";
    cout << endl;
}

// 补足:将运算符[]重载为成员函数的实现
// ×××
int & ArrayInt:: operator[](int a){
    return p[a];
}

#include <iostream>
using namespace std;

#include "arrayInt.h"

int main() {
    // 定义动态整型数组对象a，包含2个元素，初始值为0
    ArrayInt a(2);
    a.print();
    
    // 定义动态整型数组对象b，包含3个元素，初始值为6
    ArrayInt b(3, 6);
    b.print();

    // 通过对象名和下标方式访问并修改对象元素
    b[0] = 2;
    cout << b[0] << endl;
    b.print();

    system("pause");

    return 0;
}

 

第一题对于运算符“<<”的重载是按照书上的模仿写出来的，自己上手写还是有点困难。在car类声明中我将制造商，型号，生产年份和行车里程数声明为私有成员时，派生类还是不能访问，设为公有成员后程序编译是没问题，但不知道会不会带来问题。

第二题和上课老师讲的自增类似，运算符重载分为两类：重载为成员函数/非成员函数，需要注意的就是重载为成员函数时，函数的参数个数比原来的操作数个数少一个（后置++，--除外），而重载为非成员函数时，参数个数与原操作个数相同。

 

https://www.cnblogs.com/lovecpp/p/10854382.html

https://www.cnblogs.com/qiuqiuwr/p/10883165.html

https://www.cnblogs.com/zuiyankh/p/10884276.html