实验三 类与对象
#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)); }
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(); }
测试结果：
问题1：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？
答：自定义了两个类。使用了string和vector标准库中的函数，两个类。window和button存在组合关系。
问题2：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。
答：我觉得无需再加。const用于函数中是为了不改变类中数据成员的值，inline定义内联函数。在上述代码中，没有大段重复且逻辑简单的操作，没必要加inline。而const，上述代码中会对类的数据成员进行修改，所以也不用加。
问题3：类Window的定义中，有这样一行代码，其功能是？
答：调用string类的构造函数，一行元素全为“*”的字符串
2、实验任务二
task2
#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(); }
测试结果：
问题1：测试1模块中，这三行代码的功能分别是？
答：构造v1，长度为5，值为42。构造v2传入形参v1。将v1第一个值改成-999。
问题2：测试2模块中，这三行代码的功能分别是？
答：初始化v1。v2复制v1，而v2不可被修改。将v1末尾添加-999
问题3：测试2模块中，这四行代码的功能分别是
答：定义t1为v1的第0行，输出t1的最后一个数；t2同理。
问题4：1、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
答：1、深复制。2、需要
3、实验任务三
vectorint.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(); }
测试结果截图：
问题1：vectorInt类中，复制构造函数（line14)的实现，是深复制还是浅复制
答：深复制。
问题2：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
答：不能正常运行会报错，存在安全隐患。
问题3：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。
答：不能。返回值类型不对。
4、实验任务四
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 double value; Matrix::Matrix(int n, int m) :lines{ n }, cols{ m } { ptr = new double[n * m]; for (int i = 0;i < n * m;i++) { ptr[i] = value; } } Matrix::Matrix(int n) : Matrix(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 { assert(i >= 0 && i < lines && j >= 0 && j < cols); return ptr[i * cols + j]; } double& Matrix:: at(int i, int j) { assert(i >= 0 && i < lines && j >= 0 && j < cols); 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] << ", "; } cout <<"\b\b \n"; } }
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(); }
测试结果：
5、实验任务五
User.hpp
#pragma once #include<iostream> #include<cassert> #include<string> using namespace std; class User{ private: string name,password,email; public: User (string n,string p="123456",string e=""); void set_email(); void change_password(); void display(); }; User::User(string n,string p,string e):name(n),password(p),email(e){ } void User::set_email(){ string input; bool vaild = false; do{ cout<<"请输入邮箱："; cin>>input; if(input.find('@')) { email=input; vaild=true; } else cout<<"输入有误"<<endl; }while(!vaild); } void User::change_password() { int trycount=0; string oldpassword; do{ if(trycount>=3) { cout<<"用户稍后再试"<<endl; } cout<<"请输入旧密码："; cin>>oldpassword; trycount++; }while(oldpassword!=password); string newpassword; cout<<"请输入新密码："; cin>>newpassword; password=newpassword; } void User::display() { string printpassword; for(int i=0;i<password.length();i++) printpassword+='*'; cout<<"用户名："<<name<<"密码："<<printpassword<<"邮箱："<<email<<endl; }
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(); }
测试结果：
6、实验任务六
#include"account.h" #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; }
account.cpp
#include"account.h" #include<cmath> #include<iostream> using namespace std; 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; } void SavingsAccount::record(const Date& 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; }
account.h
#ifndef _ _ACCOUNT_H_ _ #define _ _ACCOUNT_H_ _ #include"date.h" #include<string> class SavingsAccount { private: std::string id; double balance; double rate; Date lastDate; double accumulation; static double total; void record(const Date& date, double amount, const std::string& desc); void error(const std::string& msg) const; double accumulate(const Date& date)const { return accumulation + balance * date.distance(lastDate); } public: 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; } void deposit(const Date& date, double amount, const std::string& desc); void withdraw(const Date& date, double amount, const std::string& desc); void settle(const Date& date); void show()const; }; #endif //_ _ACCOUNT_H_ _
data.cpp
#include"date.h" #include<iostream> #include<cstdlib> using namespace std; 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(); }
data.h
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; } };
运行结果：
