实验3 类和对象_基础编程2
实验任务1：
task1.cpp:
#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(); }
button.hpp:
#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"; }
window.hpp:
#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)); }
运行结果：
问题1：
自定义了Window类、Button类，使用到了标准库中的vector、string类；vector和Button、Window和Button之间存在组合关系。
问题2：
不能随意得对函数添加const,如果添加const，代表只能对元素进行访问操作，如：add_button()操作，添加const会报错；但是对于click和close,可以加const,在添加const时，也要注意相应函数中元素和函数是否可以调用，以免报错。在我看来，一些简单的显示和单纯的数据输出可以加const，以保护数据；至于inline，可以在简单以及需要多次调用的函数前添加，以减少函数调用的开销。
问题3：
初始化字符串s为40个' * '。
实验任务2：
task2.cpp:
#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 << "测试1:\n"; test1(); cout << "\n测试2:\n"; test2(); }
运行结果：
问题一：
vector<int> v1(5, 42)的作用是初始化v1为int类型，有5个元素，5个元素都是42的容器； const vector<int> v2(v1) 这行代码表示创建了一个名为v2的 vector 对象，其类型为 const vector<int> ，即一个不可修改的 int 类型的 vector ；
实验任务3：
vectorlnt.hpp:
#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; }
task3.cpp:
#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(); }
运行结果：
问题一：深复制。
问题二:
(1)不可以。
如果没有返回的不是引用类型，那么得到的结果是一个数，数不能为另一个数赋值，如果加了&符号，那么就可以改变之前的数值。
（2）代码可以运行，存在重载的隐患。
问题三：不可以，因为this指针指向的变量的值可以被修改，如果没有应用，那么该值就不可以被修改了。
实验任务4：
matrix.hpp:
#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; }; // 类Matrix的实现：待补足 // xxx Matrix::Matrix(int m,int n):lines(m),cols(n){ ptr = new double[m*n]; } Matrix::Matrix(int n):lines(n), cols(n) { ptr = new double[n * n]; } Matrix::Matrix(const Matrix& x) { lines = x.lines; cols = x.cols; ptr = new double[lines * cols]; for (int i = 0; i < lines * cols; i++) { ptr[i] = x.ptr[i]; } } Matrix::~Matrix(){ delete [] ptr; } void Matrix:: set(const double* pvalue) { for (int i = 0; i < lines * cols; i++) { *(ptr + i) = *(pvalue + i); } } void Matrix::clear() { for (int i = 0; i < lines * cols; i++) { ptr[i] = 0; } } const double & Matrix::at(int i, int j) const { return ptr[i * cols + j]; } double& Matrix::at(int i, int j) { return ptr[i * cols + j]; } int Matrix::get_lines() const { return lines; } int Matrix::get_cols() const { return cols; } void Matrix::display()const { for (int i = 0; i < lines; i++) { for (int j = 0; j < cols; j++) { cout << ptr[i * cols + j] <<(j<cols-1? ",":" "); } cout << endl; } }
task4.cpp:
#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(); }
运行结果：
实验任务5：
User.hpp:
#pragma once #include <iostream> #include <string> using namespace std; class User { private: string name; string password; string email; public: User(string name_s, string password_s = "123456", string email_s = " ") :name(name_s), password(password_s), email(email_s) {} void set_email() { string email_s; cout << "Enter email address:"; cin >> email_s; if (email_s.find('@') == string::npos) { cout << "illegal email.Please re-enter email:"; cin >> email_s; } email = email_s; cout << "email is set successfully..." << endl; } void change_password() { string password_s; cout << "Enter old password:"; cin >> password_s; int i = 1; if (password != password_s) { while (i <= 2) { cout << "password input error.Please re-enter again:"; cin >> password_s; i++; if (password == password_s) { cout << "Enter new password:"; cin >> password_s; password = password_s; cout << "new password is set successfully..." << endl; return; } } if (i > 2) { cout << "password input error.Please try after a while." << endl; return; } } else { cout << "Enter new password:"; cin >> password_s; password = password_s; cout << "new password is set successfully..." << endl; return; } } void display() { cout << "name: " << name << endl; cout << "pass: "; for (int i = 0; i < password.length(); i++) { cout << "*"; } cout << endl; cout << "email: " << email << endl; } ~User() {} };
task5.cpp:
#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(); }
运行结果：
实验任务6：
date.h:
#ifndef __DATE_H__ #define __DATE_H__ class Date { private: int year; //年 int month; //月 int day; //日 int totalDays; //该日期是从公元元年1月1日开始的第几天 public: Date(int year, int month, int day); //用年、月、日构造日期 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; //计算两个日期之间相差多少天 int distance(const Date& date) const { return totalDays - date.totalDays; } }; #endif
data.cpp:
#include "date.h" #include <iostream> #include <cstdlib> using namespace std; //命名空间使下面的定义只在当前文件中有效 namespace { //存储平年中的某个月1日之前有多少天，为便于getMaxDay函数的实现，该数组多出一项 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(); }
account.h:
#ifndef __ACCOUNT_H__ #define __ACCOUNT_H__ #include "date.h" #include <string> class SavingsAccount { private: std::string id; //账号 double balance; //余额 double rate; //存款的年利率 Date lastDate; //上次变更余额的日期 double accumulation; //余额按日累加之和 static double total; //所有账户的总金额 //记录一笔帐，date为日期，amount为金额，desc为说明 void record(const Date& date, double amount, const std::string& desc); //报告错误信息 void error(const std::string& msg) const; //获得指定日期为止的存款金额按日累积值 double accumulate(const Date& date) const { return accumulation + balance * date.distance(lastDate); } public: //构造函数 SavingsAccount(const Date& date, const std::string& id, double rate); const std::string& getId() const { return id; } double getBalance() const { return balance; } double getRate() const { return rate; } static double getTotal() { return total; } //存入现金 void deposit(const Date& date, double amount, const std::string& desc); //取出现金 void withdraw(const Date& date, double amount, const std::string& desc); //结算利息，每年1月1日调用一次该函数 void settle(const Date& date); //显示账户信息 void show() const; }; #endif // ACCOUNT_H
account.cpp:
#include "account.h" #include <cmath> #include <iostream> using namespace std; double SavingsAccount::total = 0; SavingsAccount::SavingsAccount(const Date& date, const std::string& id, double rate):id(id), balance(0), rate(rate), lastDate(date), accumulation(0){ date.show(); cout<< "\t#" << id << " created" << endl; } void SavingsAccount::record(const Date& date, double amount, const std::string& desc) { accumulation = accumulate(date); lastDate = date; amount = floor(amount * 100 + 0.5) / 100; //保留小数点后两位 balance += amount; total += amount; date.show(); cout << "\t#" << id << "\t" << amount << "\t" << balance << "\t" << desc << endl; } void SavingsAccount::error(const std::string& msg) const { cout << "Error(#" << id << "): " << msg << endl; } void SavingsAccount::deposit(const Date& date, double amount, const std::string& desc) { record(date, amount, desc); } void SavingsAccount::withdraw(const Date& date, double amount, const std::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; }
6_25.cpp:
#include "account.h" #include <iostream> using namespace std; int main() { Date date(2008, 11, 1); //起始日期 //建立账户 SavingsAccount accounts[] = { SavingsAccount(date, "03755217", 0.015), SavingsAccount(date, "02342342", 0.015) }; const int n = sizeof(accounts) / sizeof(SavingsAccount); //账户总数 //11月份的几笔账目 accounts[0].deposit(Date(2008, 11, 5), 5000, "salary"); accounts[1].deposit(Date(2008, 11, 25), 10000, "sell stock 0323"); //12月份的几笔账目 accounts[0].deposit(Date(2008, 12, 5), 5500, "salary"); accounts[1].withdraw(Date(2008, 12, 20), 4000, "buy a laptop"); //结算所有账户并输出各个账户信息 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; }
运行结果：
