实验3 类和对象_基础编程2 - Haruto

Task1

button.hpp

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <string>
 5 
 6 using std::string;
 7 using std::cout;
 8 
 9 // 按钮类
10 class Button {
11 public:
12     Button(const string& text);
13     string get_label() const;
14     void click();
15 
16 private:
17     string label;
18 };
19 
20 Button::Button(const string& text) : label{ text } {
21 }
22 
23 inline string Button::get_label() const {
24     return label;
25 }
26 
27 void Button::click() {
28     cout << "Button '" << label << "' clicked\n";
29 }

View Code

window.hpp

 1 #pragma once
 2 #include "button.hpp"
 3 #include <vector>
 4 #include <iostream>
 5 
 6 using std::vector;
 7 using std::cout;
 8 using std::endl;
 9 
10 // 窗口类
11 class Window {
12 public:
13     Window(const string& win_title);
14     void display() const;
15     void close();
16     void add_button(const string& label);
17 
18 private:
19     string title;
20     vector<Button> buttons;
21 };
22 
23 Window::Window(const string& win_title) : title{ win_title } {
24     buttons.push_back(Button("close"));
25 }
26 
27 inline void Window::display() const {
28     string s(40, '*');
29 
30     cout << s << endl;
31     cout << "window title: " << title << endl;
32     cout << "It has " << buttons.size() << " buttons: " << endl;
33     for (const auto& i : buttons)
34         cout << i.get_label() << " button" << endl;
35     cout << s << endl;
36 }
37 
38 void Window::close() {
39     cout << "close window '" << title << "'" << endl;
40     buttons.at(0).click();
41 }
42 
43 void Window::add_button(const string& label) {
44     buttons.push_back(Button(label));
45 }

View Code

task1.cpp

 1 #include "window.hpp"
 2 #include <iostream>
 3 
 4 using std::cout;
 5 using std::cin;
 6 
 7 void test() {
 8     Window w1("new window");
 9     w1.add_button("maximize");
10     w1.display();
11     w1.close();
12 }
13 
14 int main() {
15     cout << "用组合类模拟简单GUI:\n";
16     test();
17 }

View Code

result1

问题一　　这个模拟简单GUI的示例代码中，自定义了几个类？使用到了标准库的哪几个类？，哪些类和类之间存在组合关系？

代码中，自定义了两个类Window，Button。使用了标准库的vector，string类。Window和Button之间，Button和vector之间存在着组合关系

问题二　　在自定义类Button和Window中，有些成员函数定义时加了const, 有些设置成了inline。如果你是类的设计者，目前那些没有加const或没有设置成inline的，适合添加const，适合设置成inline吗？陈述你的答案和理由。

const用于保护数据，对于那些不需要改变值的成员函数都应该加上const。inline用于提高程序效率，适合修饰简单，常用的函数。

click也可以设置为inline或者const，因为它实际上只是显示了一行字符串。

问题三　　类Window的定义中，有这样一行代码，其功能是？

此代码的功能是构成图形界面的边框。

Task2

task2.cpp

 1 #include <iostream>
 2 #include <vector>
 3 
 4 using namespace std;
 5 
 6 void output1(const vector<int>& v) {
 7     for (auto& i : v)
 8         cout << i << ", ";
 9     cout << "\b\b \n";
10 }
11 
12 void output2(const vector<vector<int>> v) {
13     for (auto& i : v) {
14         for (auto& j : i)
15             cout << j << ", ";
16         cout << "\b\b \n";
17     }
18 }
19 
20 void test1() {
21     vector<int> v1(5, 42);
22     const vector<int> v2(v1);
23 
24     v1.at(0) = -999;
25     cout << "v1: "; output1(v1);
26     cout << "v2: "; output1(v2);
27     cout << "v1.at(0) = " << v1.at(0) << endl;
28     cout << "v2.at(0) = " << v2.at(0) << endl;
29 }
30 
31 void test2() {
32     vector<vector<int>> v1{ {1,2,3}, {4,5,6,7} };
33     const vector<vector<int>> v2(v1);
34 
35     v1.at(0).push_back(-999);
36     cout << "v1: \n"; output2(v1);
37     cout << "v2: \n"; output2(v2);
38 
39     vector<int> t1 = v1.at(0);
40     cout << t1.at(t1.size() - 1) << endl;
41 
42     const vector<int> t2 = v2.at(0);
43     cout << t2.at(t2.size() - 1) << endl;
44 }
45 
46 int main() {
47     cout << "测试1:\n";
48     test1();
49 
50     cout << "\n测试2:\n";
51     test2();
52 }

View Code

result2

问题一　　测试1模块中，这三行代码的功能分别是？

line21:创建一个储存int的vector对象，初始化有五个元素，每个元素初始化为42。

line22:用v1的数据初始化v2

line23:将v1第0个元素赋值为-999

问题二　　测试2模块中，这三行代码的功能分别是？

line32:创建一个二维vector，第一行1,2,3第二行4,5,6,7

line33:用v1的数据来创建v2

line34:在v1的第0行最后加入-999

问题三　　测试2模块中，这四行代码的功能分别是？

line39:用v1第0行的数据来创建一个一维vector

line40:输出其最后一个元素

line42:用v2第0行的数据来创建一个一维vector

line43:输出其最后一个元素

问题四　　

根据执行结果，反向分析、推断：
① 标准库模板类vector内部封装的复制构造函数，其实现机制是深复制还是浅复制？
② 模板类vector的接口at(), 是否至少需要提供一个const成员函数作为接口？

1.深复制

2.至少需要提供一个const成员函数作为接口。C++设计原则在于不去扩大权限而保证安全。应当先保证const的，再去重载非const的。

Task3

vectorInt.hpp

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <cassert>
 5 
 6 using std::cout;
 7 using std::endl;
 8 
 9 // 动态int数组对象类
10 class vectorInt {
11 public:
12     vectorInt(int n);
13     vectorInt(int n, int value);
14     vectorInt(const vectorInt& vi);
15     ~vectorInt();
16 
17     int& at(int index);
18     const int& at(int index) const;
19 
20     vectorInt& assign(const vectorInt& v);
21     int get_size() const;
22 
23 private:
24     int size;
25     int* ptr;   // ptr指向包含size个int的数组
26 };
27 
28 vectorInt::vectorInt(int n) : size{ n }, ptr{ new int[size] } {
29 }
30 
31 vectorInt::vectorInt(int n, int value) : size{ n }, ptr{ new int[size] } {
32     for (auto i = 0; i < size; ++i)
33         ptr[i] = value;
34 }
35 
36 vectorInt::vectorInt(const vectorInt& vi) :size{ vi.size }, ptr{ new int[size] } {
37     for (auto i = 0; i < size; ++i)
38         ptr[i] = vi.ptr[i];
39 }
40 
41 vectorInt::~vectorInt() {
42     delete[] ptr;
43 }
44 
45 const int& vectorInt::at(int index) const {
46     assert(index >= 0 && index < size);
47 
48     return ptr[index];
49 }
50 
51 int& vectorInt::at(int index) {
52     assert(index >= 0 && index < size);
53 
54     return ptr[index];
55 }
56 
57 vectorInt& vectorInt::assign(const vectorInt& v) {
58     delete[] ptr;      // 释放对象中ptr原来指向的资源
59 
60     size = v.size;
61     ptr = new int[size];
62 
63     for (int i = 0; i < size; ++i)
64         ptr[i] = v.ptr[i];
65 
66     return *this;
67 }
68 
69 int vectorInt::get_size() const {
70     return size;
71 }

View Code

task3.cpp

 1 #include "vectorInt.hpp"
 2 #include <iostream>
 3 
 4 using std::cin;
 5 using std::cout;
 6 
 7 void output(const vectorInt& vi) {
 8     for (auto i = 0; i < vi.get_size(); ++i)
 9         cout << vi.at(i) << ", ";
10     cout << "\b\b \n";
11 }
12 
13 
14 void test1() {
15     int n;
16     cout << "Enter n: ";
17     cin >> n;
18 
19     vectorInt x1(n);
20     for (auto i = 0; i < n; ++i)
21         x1.at(i) = i * i;
22     cout << "x1: "; output(x1);
23 
24     vectorInt x2(n, 42);
25     vectorInt x3(x2);
26     x2.at(0) = -999;
27     cout << "x2: "; output(x2);
28     cout << "x3: "; output(x3);
29 }
30 
31 void test2() {
32     const vectorInt x(5, 42);
33     vectorInt y(10, 0);
34 
35     cout << "y: "; output(y);
36     y.assign(x);
37     cout << "y: "; output(y);
38 
39     cout << "x.at(0) = " << x.at(0) << endl;
40     cout << "y.at(0) = " << y.at(0) << endl;
41 }
42 
43 int main() {
44     cout << "测试1: \n";
45     test1();
46     
47     cout << "\n测试2: \n";
48     test2();
49 }

View Code

result3

问题一vectorInt类中，复制构造函数（line14)的实现，是深复制还是浅复制？

深复制

问题二vectorInt类中，这两个at()接口，如果返回值类型改成int而非int&（相应地，实现部分也同步修改），测试代码还能正确运行吗？如果把line18返回值类型前面的const掉，针对这个测试代码，是否有潜在安全隐患？尝试分析说明。

修改后程序无法运行，expression must be a modifiable lvalue，变成了一个不可修改的左值。

如果把返回值的const去掉的话，会让const对象调用时，变得可以修改值，且在一些低级的编译器中，可能会无法识别出这个错误。

问题三vectorInt类中，assign()接口，返回值类型可以改成vectorInt吗？你的结论，及，原因分析。

在理论上是可以的，程序可以执行。但是，这样会产生额外开销，特别是vector这样的大对象，需要拷贝构造，生成一个临时的对象。

Task4

matrix.hpp

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <cassert>
 5 
 6 using std::cout;
 7 using std::endl;
 8 
 9 // 类Matrix的声明
10 class Matrix {
11 public:
12     Matrix(int n, int m); // 构造函数，构造一个n*m的矩阵, 初始值为value
13     Matrix(int n); // 构造函数，构造一个n*n的矩阵, 初始值为value
14     Matrix(const Matrix& x); // 复制构造函数， 使用已有的矩阵X构造
15     ~Matrix();
16 
17     void set(const double* pvalue); // 用pvalue指向的连续内存块数据按行为矩阵赋值
18     void clear(); // 把矩阵对象的值置0
19 
20     const double& at(int i, int j) const; // 返回矩阵对象索引(i,j)的元素const引用
21     double& at(int i, int j); // 返回矩阵对象索引(i,j)的元素引用
22 
23     int get_lines() const; // 返回矩阵对象行数
24     int get_cols() const; // 返回矩阵对象列数
25 
26     void display() const; // 按行显示矩阵对象元素值
27 
28 private:
29     int lines; // 矩阵对象内元素行数
30     int cols; // 矩阵对象内元素列数
31     double* ptr;
32 };
33 
34 Matrix::Matrix(int n, int m) : lines{ n }, cols{ m }, ptr{ new double[lines * cols] } {
35 }
36 
37 Matrix::Matrix(int n) : Matrix(n, n) {
38 }
39 
40 Matrix::Matrix(const Matrix& x) : lines{ x.lines }, cols{ x.cols }, ptr{ new double[x.lines * x.cols] } {
41     for (auto i = 0; i < lines * cols; ++i)
42         ptr[i] = x.ptr[i];
43 }
44 
45 Matrix::~Matrix() {
46     delete[] ptr;
47 }
48 
49 void Matrix::set(const double* pvalue) {
50     for (auto i = 0; i < lines * cols; ++i)
51         ptr[i] = pvalue[i];
52 }
53 
54 void Matrix::clear() {
55     for (auto i = 0; i < lines * cols; ++i)
56         ptr[i] = 0;
57 }
58 
59 const double& Matrix::at(int i, int j) const {
60     assert(i >= 0 && i < lines && j >= 0 && j < cols);
61     return ptr[i * cols + j];
62 }
63 
64 double& Matrix::at(int i, int j) {
65     assert(i >= 0 && i < lines && j >= 0 && j < cols);
66     return ptr[i * cols + j];
67 }
68 
69 inline int Matrix::get_lines() const {
70     return lines;
71 }
72 
73 inline int Matrix::get_cols() const {
74     return cols;
75 }
76 
77 void Matrix::display() const {
78     for (auto newline = 0; newline < lines; ++newline) {
79         for (int i = 0; i < cols;++i)
80             cout << ptr[newline * cols + i] << " ";
81         cout << endl;
82     }
83 }

task4.cpp

 1 #include "matrix.hpp"
 2 #include <iostream>
 3 #include <cassert>
 4 
 5 using std::cin;
 6 using std::cout;
 7 using std::endl;
 8 
 9 
10 const int N = 1000;
11 
12 // 输出矩阵对象索引为index所在行的所有元素
13 void output(const Matrix& m, int index) {
14     assert(index >= 0 && index < m.get_lines());
15 
16     for (auto j = 0; j < m.get_cols(); ++j)
17         cout << m.at(index, j) << ", ";
18     cout << "\b\b \n";
19 }
20 
21 void test1() {
22     double x[1000] = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
23 
24     int n, m;
25     cout << "Enter n and m: ";
26     cin >> n >> m;
27 
28     Matrix m1(n, m); // 创建矩阵对象m1, 大小n×m
29     m1.set(x); // 用一维数组x的值按行为矩阵m1赋值
30 
31     Matrix m2(m, n); // 创建矩阵对象m1, 大小m×n
32     m2.set(x); // 用一维数组x的值按行为矩阵m1赋值
33 
34     Matrix m3(2); // 创建一个2×2矩阵对象
35     m3.set(x); // 用一维数组x的值按行为矩阵m4赋值
36 
37     cout << "矩阵对象m1: \n"; m1.display(); cout << endl;
38     cout << "矩阵对象m2: \n"; m2.display(); cout << endl;
39     cout << "矩阵对象m3: \n"; m3.display(); cout << endl;
40 }
41 
42 void test2() {
43     Matrix m1(2, 3);
44     m1.clear();
45 
46     const Matrix m2(m1);
47     m1.at(0, 0) = -999;
48 
49     cout << "m1.at(0, 0) = " << m1.at(0, 0) << endl;
50     cout << "m2.at(0, 0) = " << m2.at(0, 0) << endl;
51     cout << "矩阵对象m1第0行: "; output(m1, 0);
52     cout << "矩阵对象m2第0行: "; output(m2, 0);
53 }
54 
55 int main() {
56     cout << "测试1: \n";
57     test1();
58     
59     cout << "测试2: \n";
60     test2();
61 }

View Code

result4

Task5

User.hpp

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <vector>
 5 #include <iomanip>
 6 
 7 using std::string;
 8 using std::cout;
 9 using std::cin;
10 using std::endl;
11 using std::setw;
12 using std::left;
13 
14 class User {
15 public:
16     User(string user_name, string user_password = "123456", string user_email = "");
17     ~User() = default;
18 
19     void set_email();
20     void change_password();
21     void display() const;
22 
23 private:
24     string name;
25     string password;
26     string email;
27 };
28 
29 User::User(string user_name, string user_password, string user_email) {
30     name = user_name;
31     password = user_password;
32     email = user_email;
33 }
34 
35 void User::set_email() {
36     string temp;
37     cout << "Enter email address: ";
38 
39     while (cin >> temp) {
40         if (temp.find('@') != std::string::npos) {
41             cout << "email is set successfully..." << endl;
42             email = temp;
43             break;
44         }
45         else {
46             cout << "illegal email. Please re-enter email: ";
47         }
48     }
49 }
50 
51 void User::change_password() {
52     string temp;
53     int count = 0;
54 
55     cout << "Enter old password: ";
56     while (cin >> temp) {
57 
58 
59         if (temp == password) {
60             cout << "Enter new password: ";
61             cin >> temp;
62             password = temp;
63             cout << "new password is set successfully..." << endl;
64             break;
65         }
66         else {
67             cout << "password input error. Please re-enter again ";
68             count++;
69             if (count >= 3) {
70                 cout << "password input error. Please try after a while." << endl;
71                 break;
72             }
73         }
74     }
75 }
76 
77 void User::display() const {
78     cout << setw(8) << left << "name: " << name << endl;
79 
80     string show_password;
81     for (auto i = 0; i < password.size(); ++i) show_password += '*';
82     cout << setw(8) << left << "pass: " << show_password << endl;
83 
84     cout << setw(8) << left << "email: " << email << endl;
85 
86 }

task5.cpp

 1 #include "user.hpp"
 2 #include <iostream>
 3 #include <vector>
 4 #include <string>
 5 
 6 using std::cin;
 7 using std::cout;
 8 using std::endl;
 9 using std::vector;
10 using std::string;
11 
12 void test() {
13     vector<User> user_lst;
14 
15     User u1("Alice", "2024113", "Alice@hotmail.com");
16     user_lst.push_back(u1);
17     cout << endl;
18 
19     User u2("Bob");
20     u2.set_email();
21     u2.change_password();
22     user_lst.push_back(u2);
23     cout << endl;
24 
25     User u3("Hellen");
26     u3.set_email();
27     u3.change_password();
28     user_lst.push_back(u3);
29     cout << endl;
30     
31     cout << "There are " << user_lst.size() << " users. they are: " << endl;
32     for (auto& i : user_lst) {
33         i.display();
34         cout << endl;
35     }
36 }
37 int main() {
38     test();
39 }

View Code

result5

Task6

date.hpp

 1 #pragma once
 2 
 3 #include<iostream>
 4 #include<cstdlib>
 5 
 6 using namespace std;
 7 class Date {
 8 private:
 9     int year;
10     int month;
11     int day;
12     int totalDays;
13 public:
14     Date(int year, int month, int day);
15     int getYear()const {
16         return year;
17     }
18     int getMonth()const {
19         return month;
20     }
21     int getDay()const {
22         return day;
23     }
24     int getMaxDay()const;
25     bool isLeapYear()const {
26         return year % 4 == 0 && year % 100 != 0 || year % 400 == 0;
27     }
28     void show() const;
29     int distance(const Date& date)const {
30         return totalDays - date.totalDays;
31     }
32 };
33 namespace {
34     const int DAYS_BEFIRE_MONTH[] = { 0,31,59,90,120,151,181,212,243,273,304 ,334,365 };
35 }
36 Date::Date(int year, int month, int day) :year(year), month(month), day(day) {
37     if (day <= 0 || day > getMaxDay()) {
38         cout << "Invalid date: ";
39         show();
40         cout << endl;
41         exit(1);
42     }
43     int years = year - 1;
44     totalDays = years * 365 + years / 4 - years / 100 + years / 400 + DAYS_BEFIRE_MONTH[month - 1] + day;
45     if (isLeapYear() && month > 2) totalDays++;
46 }
47 int Date::getMaxDay()const {
48     if (isLeapYear() && month == 2)
49         return 29;
50     else return DAYS_BEFIRE_MONTH[month] - DAYS_BEFIRE_MONTH[month - 1];
51 }
52 void Date::show()const {
53     cout << getYear() << "-" << getMonth() << "-" << getDay();
54 }

View Code

account.hpp

 1 #pragma once
 2 
 3 #include"date.hpp"
 4 #include<string>
 5 #include<cmath>
 6 #include<iostream>
 7 
 8 using namespace std;
 9 
10 class SavingsAccount {
11     private:
12         string id;
13         double balance;
14         double rate;
15         Date lastDate;
16         double accumulation;
17         static double total;
18         void record(const Date& date, double amount, const string& desc);
19         void error(const string& msg) const;
20         double accumulate(const Date& date)const {
21             return accumulation + balance * date.distance(lastDate);
22         }
23     public:
24         SavingsAccount(const Date& date, const string& id, double rate);
25         const string& getId()const {
26             return id;
27         }
28         double getBalance()const {
29             return balance;
30         }
31         double getRate()const {
32             return rate;
33         }
34         static double getTotal() {
35             return total;
36         }
37         void deposit(const Date& date, double amount, const string& desc);
38         void withdraw(const Date& date, double amount, const string& desc);
39         void settle(const Date& date);
40         void show() const;
41 };
42 double SavingsAccount::total = 0;
43 SavingsAccount::SavingsAccount(const Date& date, const string& id, double rate) :
44     id(id), balance(0), rate(rate), lastDate(date), accumulation(0) {
45     date.show();
46     cout << "\t#" << id << "created" << endl;
47 }
48 void SavingsAccount::record(const Date& date, double amount, const string& desc) {
49     accumulation = accumulate(date);
50     lastDate = date;
51     amount = floor(amount * 100 + 0.5) / 100;
52     balance += amount;
53     total += amount;
54     date.show();
55     cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl;
56 }
57 void SavingsAccount::error(const string& msg) const {
58     cout << "Error(#" << id << "):" << msg << endl;
59 }
60 void SavingsAccount::deposit(const Date& date, double amount, const string& desc) {
61     record(date, amount, desc);
62 }
63 void SavingsAccount::withdraw(const Date& date, double amount, const string& desc) {
64     if (amount > getBalance())
65         error("not enough money");
66     else
67         record(date, -amount, desc);
68 }
69 void SavingsAccount::settle(const Date& date) {
70     double interest = accumulate(date) * rate / date.distance(Date(date.getYear() - 1, 1, 1));
71     if (interest != 0) record( date,interest,"interest" );
72     accumulation = 0;
73 }
74 void SavingsAccount::show()const {
75     cout << id << "\tBalance: " << balance;
76 }

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result6

posted on 2024-11-05 20:14 Haruto 阅读(7) 评论(0) 编辑收藏举报

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