实验五

实验任务一：

#pragma once

#include <string>

// 发行/出版物类：Publisher （抽象类）
class Publisher {
public:
    Publisher(const std::string &name_ = "");            // 构造函数
    virtual ~Publisher() = default;

public:
    virtual void publish() const = 0;                 // 纯虚函数，作为接口继承
    virtual void use() const = 0;                     // 纯虚函数，作为接口继承

protected:
    std::string name;    // 发行/出版物名称
};

// 图书类: Book
class Book: public Publisher {
public:
    Book(const std::string &name_ = "", const std::string &author_ = "");  // 构造函数

public:
    void publish() const override;        // 接口
    void use() const override;            // 接口

private:
    std::string author;          // 作者
};

// 电影类: Film
class Film: public Publisher {
public:
    Film(const std::string &name_ = "", const std::string &director_ = "");   // 构造函数

public:
    void publish() const override;    // 接口
    void use() const override;        // 接口            

private:
    std::string director;        // 导演
};


// 音乐类：Music
class Music: public Publisher {
public:
    Music(const std::string &name_ = "", const std::string &artist_ = "");

public:
    void publish() const override;        // 接口
    void use() const override;            // 接口

private:
    std::string artist;      // 音乐艺术家名称
};

Publisher.hpp

#include <iostream>
#include <string>
#include "publisher.hpp"

// Publisher类：实现
Publisher::Publisher(const std::string &name_): name {name_} {
}


// Book类: 实现
Book::Book(const std::string &name_ , const std::string &author_ ): Publisher{name_}, author{author_} {
}

void Book::publish() const {
    std::cout << "Publishing book《" << name << "》 by " << author << '\n';
}

void Book::use() const {
    std::cout << "Reading book 《" << name << "》 by " << author << '\n';
}


// Film类：实现
Film::Film(const std::string &name_, const std::string &director_):Publisher{name_},director{director_} {
}

void Film::publish() const {
    std::cout << "Publishing film <" << name << "> directed by " << director << '\n';
}

void Film::use() const {
    std::cout << "Watching film <" << name << "> directed by " << director << '\n';
}


// Music类：实现
Music::Music(const std::string &name_, const std::string &artist_): Publisher{name_}, artist{artist_} {
}

void Music::publish() const {
    std::cout << "Publishing music <" << name << "> by " << artist << '\n';
}

void Music::use() const {
    std::cout << "Listening to music <" << name << "> by " << artist << '\n';
}

Publisher.cpp

#include <memory>
#include <iostream>
#include <vector>
#include "publisher.hpp"

void test1() {
   std::vector<Publisher *> v;

   v.push_back(new Book("Harry Potter", "J.K. Rowling"));
   v.push_back(new Film("The Godfather", "Francis Ford Coppola"));
   v.push_back(new Music("Blowing in the wind", "Bob Dylan"));

   for(Publisher *ptr: v) {
        ptr->publish();
        ptr->use();
        std::cout << '\n';
        delete ptr;
   }
}

void test2() {
    std::vector<std::unique_ptr<Publisher>> v;

    v.push_back(std::make_unique<Book>("Harry Potter", "J.K. Rowling"));
    v.push_back(std::make_unique<Film>("The Godfather", "Francis Ford Coppola"));
    v.push_back(std::make_unique<Music>("Blowing in the wind", "Bob Dylan"));

    for(const auto &ptr: v) {
        ptr->publish();
        ptr->use();
        std::cout << '\n';
    }
}

void test3() {
    Book book("A Philosophy of Software Design", "John Ousterhout");
    book.publish();
    book.use();
}

int main() {
    std::cout << "运行时多态：纯虚函数、抽象类\n";

    std::cout << "\n测试1: 使用原始指针\n";
    test1();

    std::cout << "\n测试2: 使用智能指针\n";
    test2();

    std::cout << "\n测试3: 直接使用类\n";
    test3();
}

Task1.cpp

运行结果为：

问题一：

（1）决定 Publisher 是抽象类的原因是它包含至少一个纯虚函数。具体依据是代码中的两个纯虚函数声明：virtual void publish() const = 0; 和 virtual void use() const = 0;（使用 = 0 语法标记为纯虚函数）。

（2）不能编译通过。因为 Publisher 是抽象类，它包含纯虚函数，编译器不允许直接创建抽象类的实例对象。要使用 Publisher 必须通过指针或引用指向其具体派生类的对象。

问题二：

（1）这三个派生类必须实现 Publisher 中声明的两个纯虚函数，完整函数声明为：void publish() const override; 和 void use() const override;。这两个函数在基类中是纯虚函数，派生类必须提供具体实现才能成为具体类，否则派生类也会成为抽象类

(2)编译会报错，错误信息大致是："函数签名不匹配，不是对基类虚函数的重写" 或 "不能覆盖基类的虚函数"。具体而言，编译器会指出 Film::publish() 和 Film::use() 没有正确覆盖基类的 Publisher::publish() const 和 Publisher::use() const，因为函数签名中的 const 限定符不一致，导致这是两个不同的函数，而不是有效的重写（override）。

问题三：

（1）ptr 的声明类型是 Publisher*，即指向 Publisher 基类的指针类型。这个声明类型是编译器在编译时看到的类型。

（2）按循环顺序，ptr 实际指向的对象类型分别是：第一次循环指向 Book 类型（《Harry Potter》），第二次循环指向 Film 类型（《The Godfather》），第三次循环指向 Music 类型（《Blowing in the wind》）。这些实际类型在运行时通过虚函数表动态确定。

（3）基类析构函数声明为 virtual 是为了确保通过基类指针删除派生类对象时，能够正确调用派生类的析构函数。如果删除 virtual，执行 delete ptr 时只会调用基类 Publisher 的析构函数，而不会调用 Book、Film、Music 等派生类的析构函数，导致派生类特有的资源（如 std::string 成员）无法正确释放，造成资源泄漏。这是一种典型的内存管理错误。

实验任务二：

#pragma once
#include <string>

// 图书描述信息类Book: 声明
class Book {
public:
    Book(const std::string &name_, 
         const std::string &author_, 
         const std::string &translator_, 
         const std::string &isbn_, 
         double price_);

    friend std::ostream& operator<<(std::ostream &out, const Book &book);

private:
    std::string name;        // 书名
    std::string author;      // 作者
    std::string translator;  // 译者
    std::string isbn;        // isbn号
    double price;        // 定价
};

book.hpp

#include <iomanip>
#include <iostream>
#include <string>
#include "book.hpp"


// 图书描述信息类Book: 实现
Book::Book(const std::string &name_, 
          const std::string &author_, 
          const std::string &translator_, 
          const std::string &isbn_, 
          double price_):name{name_}, author{author_}, translator{translator_}, isbn{isbn_}, price{price_} {
}

// 运算符<<重载实现
std::ostream& operator<<(std::ostream &out, const Book &book) {
    using std::left;
    using std::setw;
    
    out << left;
    out << setw(15) << "书名:" << book.name << '\n'
        << setw(15) << "作者:" << book.author << '\n'
        << setw(15) << "译者:" << book.translator << '\n'
        << setw(15) << "ISBN:" << book.isbn << '\n'
        << setw(15) << "定价:" << book.price;

    return out;
}

book.cpp

#pragma once

#include <string>
#include "book.hpp"

// 图书销售记录类BookSales：声明
class BookSale {
public:
    BookSale(const Book &rb_, double sales_price_, int sales_amount_);
    int get_amount() const;   // 返回销售数量
    double get_revenue() const;   // 返回营收
    
    friend std::ostream& operator<<(std::ostream &out, const BookSale &item);

private:
    Book rb;         
    double sales_price;      // 售价
    int sales_amount;       // 销售数量
};

booksale.hpp

#include <iomanip>
#include <iostream>
#include <string>
#include "booksale.hpp"

// 图书销售记录类BookSales：实现
BookSale::BookSale(const Book &rb_, 
                   double sales_price_, 
                   int sales_amount_): rb{rb_}, sales_price{sales_price_}, sales_amount{sales_amount_} {
}

int BookSale::get_amount() const {
    return sales_amount;
}

double BookSale::get_revenue() const {
    return sales_amount * sales_price;
}

// 运算符<<重载实现
std::ostream& operator<<(std::ostream &out, const BookSale &item) {
    using std::left;
    using std::setw;
    
    out << left;
    out << item.rb << '\n'
        << setw(15) << "售价:" << item.sales_price << '\n'
        << setw(15) << "销售数量:" << item.sales_amount << '\n'
        << setw(15) << "营收:" << item.get_revenue();

    return out;
}

booksale.cpp

#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string>
#include <vector>
#include "booksale.hpp"

// 按图书销售数量比较
bool compare_by_amount(const BookSale &x1, const BookSale &x2) {
    return x1.get_amount() > x2.get_amount();
}

void test() {
    using std::cin;
    using std::cout;
    using std::getline;
    using std::sort;
    using std::string;
    using std::vector;
    using std::ws;

    vector<BookSale> sales_records;         // 图书销售记录表

    int books_number;
    cout << "录入图书数量: ";
    cin >> books_number;

    cout << "录入图书销售记录\n";
    for(int i = 0; i < books_number; ++i) {
        string name, author, translator, isbn;
        double price;
        cout << string(20, '-') << "第" << i+1 << "本图书信息录入" << string(20, '-') << '\n';
        cout << "录入书名: "; getline(cin>>ws, name);
        cout << "录入作者: "; getline(cin>>ws, author);
        cout << "录入译者: "; getline(cin>>ws, translator);
        cout << "录入isbn: "; getline(cin>>ws, isbn);
        cout << "录入定价: "; cin >> price;

        Book book(name, author, translator, isbn, price);

        double sales_price;
        int sales_amount;

        cout << "录入售价: "; cin >> sales_price;
        cout << "录入销售数量: "; cin >> sales_amount;

        BookSale record(book, sales_price, sales_amount);
        sales_records.push_back(record);
    }

    // 按销售册数排序
    sort(sales_records.begin(), sales_records.end(), compare_by_amount);

    // 按销售册数降序输出图书销售信息
    cout << string(20, '=') <<  "图书销售统计" << string(20, '=') << '\n';
    for(auto &record: sales_records) {
        cout << record << '\n';
        cout << string(40, '-') << '\n';
    }
}

int main() {
    test();
}

task2.cpp

运行结果为：

问题一：

（1）两处，第一处用于BOOK类型，第二处用于booksale类型

（2）在 booksale.cpp 的 operator<< 重载中：out << item.rb << '\n'（输出 Book 对象）；在 test.cpp 的 test() 函数中：cout << record << '\n'（输出 BookSale 对象）；另外在 booksale.cpp 的 operator<< 重载实现中，通过调用 Book 的 << 重载来输出图书基本信息。

问题二：

（1）定义比较函数 compare_by_amount：返回 x1.get_amount() > x2.get_amount()，使用 std::sort 算法：sort(sales_records.begin(), sales_records.end(), compare_by_amount)，比较函数返回 true 时，第一个参数排在第二个参数前面，由于是 > 比较，实现了降序排列

实验任务三：

无需写入实验博客文档

实验任务四：

#pragma once
#include <string>

// 机器宠物抽象类 MachinePet
class MachinePet {
public:
    MachinePet(const std::string &nickname_ = "") : nickname(nickname_) {}
    virtual ~MachinePet() = default;
    
    std::string get_nickname() const {
        return nickname;
    }
    
    // 纯虚函数，支持运行时多态
    virtual std::string talk() const = 0;

protected:
    std::string nickname;    // 昵称
};

// 电子宠物猫类 PetCat
class PetCat : public MachinePet {
public:
    PetCat(const std::string &nickname_ = "") : MachinePet(nickname_) {}
    
    std::string talk() const override {
        return "miao";
    }
};

// 电子宠物狗类 PetDog
class PetDog : public MachinePet {
public:
    PetDog(const std::string &nickname_ = "") : MachinePet(nickname_) {}
    
    std::string talk() const override {
        return "wang";
    }
};

#include <iostream>
#include <memory>
#include <vector>
#include "pet.hpp"

void test1() {
    std::vector<MachinePet *> pets;

    pets.push_back(new PetCat("miku"));
    pets.push_back(new PetDog("da huang"));

    for(MachinePet *ptr: pets) {
        std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n';
        delete ptr;  // 须手动释放资源
    }   
}

void test2() {
    std::vector<std::unique_ptr<MachinePet>> pets;

    pets.push_back(std::make_unique<PetCat>("miku"));
    pets.push_back(std::make_unique<PetDog>("da huang"));

    for(auto const &ptr: pets)
        std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n';
}

void test3() {
    // MachinePet pet("little cutie");   // 编译报错：无法定义抽象类对象

    const PetCat cat("miku");
    std::cout << cat.get_nickname() << " says " << cat.talk() << '\n';

    const PetDog dog("da huang");
    std::cout << dog.get_nickname() << " says " << dog.talk() << '\n';
}

int main() {
    std::cout << "测试1: 使用原始指针\n";
    test1();

    std::cout << "\n测试2: 使用智能指针\n";
    test2();

    std::cout << "\n测试3: 直接使用类\n";
    test3();
}
task4.cpp

运行结果为：

实验任务五：

#pragma once
#include <iostream>

template<typename T>
class Complex {
private:
    T real;      // 实部
    T imag;      // 虚部
    
public:
    // 构造函数
    Complex() : real(0), imag(0) {}
    Complex(T r, T i = 0) : real(r), imag(i) {}
    
    // 拷贝构造函数
    Complex(const Complex& other) : real(other.real), imag(other.imag) {}
    
    // 获取实部和虚部
    T get_real() const { return real; }
    T get_imag() const { return imag; }
    
    // 运算符重载
    Complex& operator+=(const Complex& other) {
        real += other.real;
        imag += other.imag;
        return *this;
    }
    
    Complex operator+(const Complex& other) const {
        return Complex(real + other.real, imag + other.imag);
    }
    
    bool operator==(const Complex& other) const {
        return (real == other.real) && (imag == other.imag);
    }
    
    // 友元函数重载输入输出运算符
    template<typename U>
    friend std::ostream& operator<<(std::ostream& out, const Complex<U>& c);
    
    template<typename U>
    friend std::istream& operator>>(std::istream& in, Complex<U>& c);
};

// 输出运算符重载
template<typename T>
std::ostream& operator<<(std::ostream& out, const Complex<T>& c) {
    out << "(" << c.real << ", " << c.imag << ")";
    return out;
}

// 输入运算符重载
template<typename T>
std::istream& operator>>(std::istream& in, Complex<T>& c) {
    in >> c.real >> c.imag;
    return in;
}

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

void test1() {
    using std::cout;
    using std::boolalpha;
    
    Complex<int> c1(2, -5), c2(c1);

    cout << "c1 = " << c1 << '\n';
    cout << "c2 = " << c2 << '\n';
    cout << "c1 + c2 = " << c1 + c2 << '\n';
    
    c1 += c2;
    cout << "c1 = " << c1 << '\n';
    cout << boolalpha << (c1 == c2) << '\n';
}

void test2() {
    using std::cin;
    using std::cout;

    Complex<double> c1, c2;
    cout << "Enter c1 and c2: ";
    cin >> c1 >> c2;
    cout << "c1 = " << c1 << '\n';
    cout << "c2 = " << c2 << '\n';

    const Complex<double> c3(c1);
    cout << "c3.real = " << c3.get_real() << '\n';
    cout << "c3.imag = " << c3.get_imag() << '\n';
}

int main() {
    std::cout << "自定义类模板Complex测试1: \n";
    test1();

    std::cout << "\n自定义类模板Complex测试2: \n";
    test2();
}
task5.cpp

运行结果为：