实验3 类和对象_基础编程2

标签：std const cout 对象 编程 int 实验 include string

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;
    }
}

View Code

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();
}

View Code

 

 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() {}
};

View Code

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", "[email protected]");
    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();
}

View Code

 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 

View Code

 

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();
}

View Code

 

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

View Code

 

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;
}

View Code

 

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;
}

View Code

 

 运行结果：

 

标签：std,const,cout,对象,编程,int,实验,include,string
From： https://www.cnblogs.com/wxdyyds/p/18525518