实验3 类和对象-基础编程2

实验任务1：

Button.hpp，Window.hpp，task1.cpp，源码，运行测试结果如下

#pragma once

#include <iostream>
#include <string>

using std::string;
using std::cout;

// 按钮类
class Button {
public:
    Button(const string &text);
    string get_label() const;
    void click();

private:
    string label;
};

Button::Button(const string &text): label{text} {
}

inline string Button::get_label() const {
    return label;
}

void Button::click() {
    cout << "Button '" << label << "' clicked\n";
}

#pragma once
#include "button.hpp"
#include <vector>
#include <iostream>

using std::vector;
using std::cout;
using std::endl;

// 窗口类
class Window{
public:
    Window(const string &win_title);
    void display() const;
    void close();
    void add_button(const string &label);

private:
    string title;
    vector<Button> buttons;
};

Window::Window(const string &win_title): title{win_title} {
    buttons.push_back(Button("close"));
}

inline void Window::display() const {
    string s(40, '*');

    cout << s << endl;
    cout << "window title: " << title << endl;
    cout << "It has " << buttons.size() << " buttons: " << endl;
    for(const auto &i: buttons)
        cout << i.get_label() << " button" << endl;
    cout << s << endl;
}

void Window::close() {
    cout << "close window '" << title << "'" << endl;
    buttons.at(0).click();
}

void Window::add_button(const string &label) {
    buttons.push_back(Button(label));
}

#include "window.hpp"
#include <iostream>

using std::cout;
using std::cin;

void test() {
    Window w1("new window");
    w1.add_button("maximize");
    w1.display();
    w1.close();
}

int main() {
    cout << "用组合类模拟简单GUI:\n";
    test();
}

问题1：

定义了Button和Window两个类；使用到标准库中的string,vector；sting定义了Button中label且在Window中有输出，vector定义了Window中的Buttons，是一个string的vector

问题2：

click（）和close（）都没必要加const，因为其没有参数传入；它们也没必要加inline，因为只在开头和结尾使用一次。

问题3：

使用string构造一个字符串，第一个参数是字符串长度int，第二个参数是每个位置应填充的字符；代码将创造含四十个连续*的字符串

 

实验任务2：

task2.cpp，源码，运行测试结果如下

#include <iostream>
#include <vector>

using namespace std;

void output1(const vector<int> &v) {
    for(auto &i: v)
        cout << i << ", ";
    cout << "\b\b \n";
}

void output2(const vector<vector<int>> v) {
    for(auto &i: v) {
        for(auto &j: i)
            cout << j << ", ";
        cout << "\b\b \n";
    }
}

void test1() {
    vector<int> v1(5, 42);
    const vector<int> v2(v1);

    v1.at(0) = -999;
    cout << "v1: ";  output1(v1);
    cout << "v2: ";  output1(v2);
    cout << "v1.at(0) = " << v1.at(0) << endl;
    cout << "v2.at(0) = " << v2.at(0) << endl;
}

void test2() {
    vector<vector<int>> v1{{1, 2, 3}, {4, 5, 6, 7}};
    const vector<vector<int>> v2(v1);

    v1.at(0).push_back(-999);
    cout << "v1: \n";  output2(v1);
    cout << "v2: \n";  output2(v2);

    vector<int> t1 = v1.at(0);
    cout << t1.at(t1.size()-1) << endl;
    
    const vector<int> t2 = v2.at(0);
    cout << t2.at(t2.size()-1) << endl;
}

int main() {
    cout << "    1:\n";
    test1();

    cout << "\n    2:\n";
    test2();
}

问题1：

vector<int>v1(5, 42);创造名为v1的一维向量，用五个42填充，const vector<int>v2(v1);创造一个名为v2的一维向量，用v2初始化它，有const修饰不可修改，v1.at(0) = -999;用at成员函数访问v1的第一个元素并将它改为-999

问题2：

vector<vector<int>>v1{ {1,2,3},{4,5,6,7} };创造一个名为v1的二维向量，它包含两个一维向量，分别是{1，2，3}和{4，5，6，7}，const vector<vector<int>>v2(v1);创造一个名为v2的二维向量，用v1初始化它，用const修饰不可修改，v1.at(0).push_back(-999);用at成员函数访问v1的第一个一维向量，并向末尾添加-999

 问题3：

line39定义了vector类型的t1，用v1的第一个成员给t1赋初值 line40输出了t1的最后一个元素 line42定义了const修饰的vector类型的t2，用v2的第一个成员给t2赋初值 line43输出了t1的最后一个元素

问题4：

是浅复制，需要

 

实验任务3：

vectorInt.hpp，task3.cpp，源码，运行测试结果如下

#pragma once

#include <iostream>
#include <cassert>

using std::cout;
using std::endl;

// 动态int数组对象类
class vectorInt{
public:
    vectorInt(int n);
    vectorInt(int n, int value);
    vectorInt(const vectorInt &vi);
    ~vectorInt();

    int& at(int index);
    const int& at(int index) const;

    vectorInt& assign(const vectorInt &v);
    int get_size() const;

private:
    int size;
    int *ptr;       // ptr指向包含size个int的数组
};

vectorInt::vectorInt(int n): size{n}, ptr{new int[size]} {
}

vectorInt::vectorInt(int n, int value): size{n}, ptr{new int[size]} {
    for(auto i = 0; i < size; ++i)
        ptr[i] = value;
}

vectorInt::vectorInt(const vectorInt &vi): size{vi.size}, ptr{new int[size]} {
    for(auto i = 0; i < size; ++i)
        ptr[i] = vi.ptr[i];
}

vectorInt::~vectorInt() {
    delete [] ptr;
}

const int& vectorInt::at(int index) const {
    assert(index >= 0 && index < size);

    return ptr[index];
}

int& vectorInt::at(int index) {
    assert(index >= 0 && index < size);

    return ptr[index];
}

vectorInt& vectorInt::assign(const vectorInt &v) {  
    delete[] ptr;       // 释放对象中ptr原来指向的资源

    size = v.size;
    ptr = new int[size];

    for(int i = 0; i < size; ++i)
        ptr[i] = v.ptr[i];

    return *this;
}

int vectorInt::get_size() const {
    return size;
}

#include "vectorInt.hpp"
#include <iostream>

using std::cin;
using std::cout;

void output(const vectorInt &vi) {
    for(auto i = 0; i < vi.get_size(); ++i)
        cout << vi.at(i) << ", ";
    cout << "\b\b \n";
}


void test1() {
    int n;
    cout << "Enter n: ";
    cin >> n;

    vectorInt x1(n);
    for(auto i = 0; i < n; ++i)
        x1.at(i) = i*i;
    cout << "x1: ";  output(x1);

    vectorInt x2(n, 42);
    vectorInt x3(x2);
    x2.at(0) = -999;
    cout << "x2: ";  output(x2);
    cout << "x3: ";  output(x3);
}

void test2() {
    const vectorInt  x(5, 42);
    vectorInt y(10, 0);

    cout << "y: ";  output(y);
    y.assign(x);
    cout << "y: ";  output(y);
    
    cout << "x.at(0) = " << x.at(0) << endl;
    cout << "y.at(0) = " << y.at(0) << endl;
}

int main() {
    cout << "测试1: \n";
    test1();

    cout << "\n测试2: \n";
    test2();
}

问题1：

深复制，因为释放了原有资源并且分配了新内存

问题2：

不能。

如果去掉第一个const，那么返回的引用将不再是对常量的引用，调用者可以通过这个引用来修改整数值。这可能会破坏类的封装性，特别是如果这个函数返回的是类的内部数据结构的直接引用的话。如果去掉第二个const，那么该函数将不再是一个常量成员函数，它将能够修改调用它的对象的状态。这可能会导致在不应该修改对象状态的情况下意外地修改了对象，从而引入难以追踪的错误。

问题3：

不可以？运行结果没有出错，但是返回对象会带来不必要的复制，而且如果错误返回对象的引用会导致未定义行为

 

实验任务4：

Matrix.hpp，task4.cpp，源码，运行测试结果如下

#pragma once

#include <iostream>
#include <cassert>

using std::cout;
using std::endl;

// 类Matrix的声明
class Matrix {
public:
    Matrix(int n, int m);           // 构造函数，构造一个n*m的矩阵, 初始值为value
    Matrix(int n);                  // 构造函数，构造一个n*n的矩阵, 初始值为value
    Matrix(const Matrix &x);        // 复制构造函数， 使用已有的矩阵X构造
    ~Matrix();

    void set(const double *pvalue);         // 用pvalue指向的连续内存块数据按行为矩阵赋值
    void clear();                           // 把矩阵对象的值置0
    
    const double& at(int i, int j) const;   // 返回矩阵对象索引(i,j)的元素const引用
    double& at(int i, int j);               // 返回矩阵对象索引(i,j)的元素引用
    
    int get_lines() const;                  // 返回矩阵对象行数
    int get_cols() const;                   // 返回矩阵对象列数

    void display() const;                    // 按行显示矩阵对象元素值

private:
    int lines;      // 矩阵对象内元素行数
    int cols;       // 矩阵对象内元素列数
    double *ptr;
};

#include "matrix.hpp"
#include <iostream>
#include <cassert>

using std::cin;
using std::cout;
using std::endl;


const int N = 1000;

// 输出矩阵对象索引为index所在行的所有元素
void output(const Matrix &m, int index) {
    assert(index >= 0 && index < m.get_lines());

    for(auto j = 0; j < m.get_cols(); ++j)
        cout << m.at(index, j) << ", ";
    cout << "\b\b \n";
}


void test1() {
    double x[1000] = {1, 2, 3, 4, 5, 6, 7, 8, 9};

    int n, m;
    cout << "Enter n and m: ";
    cin >> n >> m;

    Matrix m1(n, m);    // 创建矩阵对象m1, 大小n×m
    m1.set(x);          // 用一维数组x的值按行为矩阵m1赋值

    Matrix m2(m, n);    // 创建矩阵对象m1, 大小m×n
    m2.set(x);          // 用一维数组x的值按行为矩阵m1赋值

    Matrix m3(2);       // 创建一个2×2矩阵对象
    m3.set(x);          // 用一维数组x的值按行为矩阵m4赋值

    cout << "矩阵对象m1: \n";   m1.display();  cout << endl;
    cout << "矩阵对象m2: \n";   m2.display();  cout << endl;
    cout << "矩阵对象m3: \n";   m3.display();  cout << endl;
}

void test2() {
    Matrix m1(2, 3);
    m1.clear();
    
    const Matrix m2(m1);
    m1.at(0, 0) = -999;

    cout << "m1.at(0, 0) = " << m1.at(0, 0) << endl;
    cout << "m2.at(0, 0) = " << m2.at(0, 0) << endl;
    cout << "矩阵对象m1第0行: "; output(m1, 0);
    cout << "矩阵对象m2第0行: "; output(m2, 0);
}

int main() {
    cout << "测试1: \n";
    test1();

    cout << "测试2: \n";
    test2();
}

 

实验任务5：

user.hpp，task5.cpp，源码，运行测试结果如下

#include<iostream>
#include<vector>
#include<string>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::string;

class User{
public:
    User(string n,string p="123456",string e="NULL");
    
    void set_email();
    
    void change_password();
    
    void display() const;
    
private:
    string name;
    string password;
    string email;

};

User::User(string n,string p,string e){
    name=n;
    password=p;
    email=e;
}

void User::set_email(){
    string em;
    cout<<"Enter email address:";
    while(cin>>em){
        int count=0;
        for(int i=0;i<em.size();i++){
            if(em[i]=='@'){
                count++;
            }
        }
        if(count){
            email=em;
            cout<<"email is set successfully..."<<endl;
            break;
        }
        else{
            cout<<"illegal email.Please re-enter email:";
        }
    }
    
}

void User::change_password(){
    string oe,ne;
    int count=0;
    cout<<"Enter old password:";
    cin>>oe;
    for(int i=0;i<3;i++){
        if(oe==password){
            cout<<"Enter new password:";
            cin>>ne;
            email=ne;
            cout<<"new password is set succesfully"<<endl;
            break;
        }
        else{
            count++;
            if(count==3){
                cout<<"password input error.Please try after a while."<<endl;
                break;
            }
            cout<<"password input error.Please re-enter again:";
            cin>>oe;
        }
        
    }
        
}

void User::display() const{
    cout<<"name:"<<name<<endl;
    int i=password.size();
    for(int j=0;j<i;j++){
        cout<<"*";
    }
    cout<<endl;
    cout<<"email:"<<email<<endl;
}

#include "user.hpp"
#include <iostream>
#include <vector>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::string;

void test() {
    vector<User> user_lst;

    User u1("Alice", "2024113", "Alice@hotmail.com");
    user_lst.push_back(u1);
    cout << endl;

    User u2("Bob");
    u2.set_email();
    u2.change_password();
    user_lst.push_back(u2);
    cout << endl;

    User u3("Hellen");
    u3.set_email();
    u3.change_password();
    user_lst.push_back(u3);
    cout << endl;

    cout << "There are " << user_lst.size() << " users. they are: " << endl;
    for(auto &i: user_lst) {
        i.display();
        cout << endl;
    }
}

int main() {
    test();
}

 

实验任务6：

data.hpp，account.cpp，task6.cpp，源码，运行测试结果如下

#pragma once 
#include <iostream>  
#include <cstdlib>  
using namespace std;
 
 class Date {
 private:
     int year;
int month;
 int day;
 int totalDays;
public:
Date(int year, int month, int day);
int getYear() const { return year; }
  int getMonth() const { return month; }
int getDay() const { return day; }
  int getMaxDay() const;
bool isLeapYear() const {
      return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
  }
   void show() const;
   int distance(const Date& date) const {
     return totalDays - date.totalDays;
   }
 };
 
namespace {
   const int DAYS_BEFORE_MONTH[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 };
}
 Date::Date(int year, int month, int day) : year(year), month(month), day(day) {
     if (day <= 0 || day > getMaxDay()) {
     cout << "Invalid date: ";
      show();
     cout << endl;
       exit(1);
    }
   int years = year - 1;
     totalDays = years * 365 + years / 4 - years / 100 + years / 400 +DAYS_BEFORE_MONTH[month - 1] + day;
   if (isLeapYear() && month > 2) totalDays++;
 }

 int Date::getMaxDay() const {
   if (isLeapYear() && month == 2)
       return 29;
    else
    return DAYS_BEFORE_MONTH[month] - DAYS_BEFORE_MONTH[month - 1];
 }

 void Date::show() const {
     cout << getYear() << "-" << getMonth() << "-" << getDay();
 }

date.hpp

#pragma once  
#include "date.hpp"  
#include <string>  
#include <cmath>  
#include <iostream>  
using namespace std;

 class SavingsAccount {
private:
string id;
  double balance;
double rate;
   Date lastDate;
  double accumulation;
  static double total;
  void record(const Date& date, double amount, const string& desc);
    void error(const string& msg) const;
   double accumulate(const Date& date) const {
       return accumulation + balance * date.distance(lastDate);
    }
 public:
   SavingsAccount(const Date& date, const string& id, double rate);
   const string& getId() const { return id; }
    double getRate() const { return rate; }
 static double getTotal() { return total; }
   void deposit(const Date& date, double amount, const string& desc);
    void withdraw(const Date& date, double amount, const string& desc);
    void settle(const Date& date);
    void show() const;
 };
 
 double SavingsAccount::total = 0;
 
SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate) :
     id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {
    date.show();
    cout << "\t#" << id << " created" << endl;
 }
 
date, double amount, const string& desc) {
     accumulation = accumulate(date);
   lastDate = date;
     amount = floor(amount * 100 + 0.5) / 100;
     balance += amount;
     total += amount;
    date.show();
     cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
 }
 
 void SavingsAccount::error(const string& msg) const {
     cout << "Error(#" << id << "):" << msg << endl;
 }

 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) {
   record(date, amount, desc);
 }
 
 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) {
   if (amount > getBalance())
       error("not enough money");
     else
       record(date, -amount, desc);
 }

void SavingsAccount::settle(const Date& date) {
    double interest = accumulate(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1));
   if (interest != 0) record(date, interest, "interest");
   accumulation = 0;
 }
 
 void SavingsAccount::show() const {
cout << id << "\tBalance: " << balance;
 }

#include "account.hpp"  
#include <iostream>  
 using namespace std;

int main() {
Date date{ 2008, 11, 1 };
  SavingsAccount accounts[] = {
  SavingsAccount(date, "03755217", 0.015),
 SavingsAccount(date, "02342342", 0.015)
    };
  const int n = sizeof(accounts) / sizeof(SavingsAccount);
   accounts[0].deposit(Date(2008, 11, 5), 5000, "salary");
    accounts[1].deposit(Date(2008, 11, 25), 10000, "sell stock 0323");
   accounts[0].deposit(Date(2008, 12, 5), 5500, "salary");
   accounts[1].withdraw(Date(2008, 12, 20), 4000, "buy a laptop");
    cout << endl;
    for (int i = 0; i < n; i++) {
       accounts[i].settle(Date(2009, 1, 1));
     accounts[i].show();
      cout << endl;
    }
    cout << "Total: " << SavingsAccount::getTotal() << endl;
   return 0;
}

task6.cpp