实验5

任务1

publisher.hpp

 

#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.cpp

#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';
}

task1.cpp

#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();
}

问题1：抽象类机制

（1）是什么决定了 Publisher 是抽象类？用一句话说明，并指出代码中的具体依据。

　　答：纯虚函数。virtual void publish() const = 0

 

（2）如果在 main.cpp 里直接写 Publisher p; 能否编译通过？为什么？

　　答：不能。因为抽象类不能实例化对象

 

问题2：纯虚函数与接口继承

（1） Book 、 Film 、 Music 必须实现哪两个函数才能通过编译？请写出其完整函数声明。

　　答：publish()和use()。void publish() const override;   void use() const override;

（2） 在 publisher.cpp 的 Film 类实现中，把两个成员函数实现里的 const 去掉（保持函数体不变），重新 编译，报错信息是什么？

　　答：匹配错误

 

问题3：运行时多态与虚析构 （1）在 test1() 里， for (Publisher *ptr : v) 中 ptr 的声明类型是什么？

　　答：Publisher*

（2）当循环执行到 ptr->publish(); 时， ptr 实际指向的对象类型分别有哪些？（按循环顺序写出）

　　答：Book,Film,Music

（3）基类 Publisher 的析构函数为何声明为 virtual ？若删除 virtual ，执行 delete ptr; 会出现什么 问题？

　　答：实现多态析构。只调用Publisher的析构函数，不会调用子类的析构函数

 

任务2

book.hpp

#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.cpp

#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;
　　}

booksale.hpp

#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.cpp

#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;
}

task2.cpp

#include "booksale.hpp"
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
// 按图书销售数额比较
bool compare_by_amount(const BookSale &x1, const BookSale &x2) {
    return x1.get_amount() > x2.get_amount();
}
void test() {
    using namespace std;
    vector<BookSale> sales_lst; // 存放图书销售记录
    int books_number;
    cout << "录入图书数量: ";
    cin >> books_number;
    cout << "录入图书销售记录" << endl;
    for(int i = 0; i < books_number; ++i) {
    string name, author, translator, isbn;
    float price;
    cout << string(20, '-') << "第" << i+1 << "本图书信息录入" << string(20, '-') <<endl;
    cout << "录入书名: "; cin >> name;
    cout << "录入作者: "; cin >> author;
    cout << "录入译者: "; cin >> translator;
    cout << "录入isbn: "; cin >> isbn;
    cout << "录入定价: "; cin >> price;
    Book book(name, author, translator, isbn, price);
    float 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_lst.push_back(record);
}
// 按销售册数排序
    sort(sales_lst.begin(), sales_lst.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, '=') << endl;
    for(auto &t: sales_lst) {
        cout << t << endl;
        cout << string(40, '-') << endl;
    }
}
int main() {
    test();
}

问题1：重载运算符<<

（1）找出运算符 << 被重载了几处？分别用于什么类型？

　　答：两次。Book和BookSale类型

（2）找出使用重载 << 输出对象的代码，写在下面。

　　答：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;

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;

问题2：图书销售统计

（1）图书销售记录"按销售数量降序排序"，代码是如何实现的？

　　答：通过compare_by_amount（）函数将大的排在前面

 

任务3

task3_1.cpp

 

#include <iostream>
// 类A的定义
class A {
public:
    A(int x0, int y0);
    void display() const;
private:
    int x, y;
};
A::A(int x0, int y0): x{x0}, y{y0} {
}
void A::display() const {
    std::cout << x << ", " << y << '\n';
}
// 类B的定义
class B {
public:
    B(double x0, double y0);
    void display() const;
private:
    double x, y;
};
B::B(double x0, double y0): x{x0}, y{y0} {
}
void B::display() const {
    std::cout << x << ", " << y << '\n';
}
void test() {
    std::cout << "测试类A: " << '\n';
    A a(3, 4);
    a.display();
    std::cout << "\n测试类B: " << '\n';
    B b(3.2, 5.6);
    b.display();
}
int main() {
    test();
}

 

 task3_2.cpp

#include <iostream>
#include <string>
// 定义类模板
template<typename T>
class X{
public:
    X(T x0, T y0);
    void display();
private:
    T x, y;
};
template<typename T>
X<T>::X(T x0, T y0): x{x0}, y{y0} {
}
template<typename T>
void X<T>::display() {
    std::cout << x << ", " << y << '\n';
}
void test() {
    std::cout << "测试1: 用int实例化类模板X" << '\n';
    X<int> x1(3, 4);
    x1.display();
    std::cout << "\n测试2: 用double实例化类模板X" << '\n';
    X<double> x2(3.2, 5.6);
    x2.display();
    std::cout << "\n测试3: 用string实例化类模板X" << '\n';
    X<std::string> x3("hello", "oop");
    x3.display();
}
int main() {
    test();
}

任务4

pet.hpp

#include<iostream> 
#include<vector>
#include<string>
class MachinePet{
public:
    MachinePet(const std::string &name_ = ""); 
    virtual ~MachinePet() = default;
    std::string get_nickname() const;
    virtual std::string talk() const =0;
protected:
    std::string name;
};
class PetCat: public MachinePet{
public:
    PetCat(const std::string &name_= ""):MachinePet(name_){
    };
    std::string talk() const override;
};

class PetDog: public MachinePet {
public:
    PetDog(const std::string &name_= ""):MachinePet(name_){
    }; 
    std::string talk() const override;
};

pet.cpp

#include<iostream> 
#include<vector>
#include<string>
#include "pet.hpp"
MachinePet::MachinePet(const std::string &name_):name(name_){}
std::string MachinePet::get_nickname()const{
    return name;
} 

std::string PetCat::talk()const{
    return "miao wu~";
}
std::string PetDog::talk()const{
    return "wang wang wang~";
}

task4.cpp

#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();
}

任务5

Complex.hpp

#include <iostream>
using namespace std;

template <typename T>
class Complex {
private:
    T real_;
    T imag_;

public:

    Complex(T real = 0, T imag = 0) : real_(real), imag_(imag) {}
    Complex(const Complex<T>& other) : real_(other.real_), imag_(other.imag_) {}

    T get_real() const { return real_; }
    T get_imag() const { return imag_; }

    Complex<T> operator+(const Complex<T>& other) const {
        return Complex<T>(real_ + other.real_, imag_ + other.imag_);
    }

    Complex<T>& operator+=(const Complex<T>& other) {
        real_ += other.real_;
        imag_ += other.imag_;
        return *this;
    }

    bool operator==(const Complex<T>& other) const {
        return (real_ == other.real_) && (imag_ == other.imag_);
    }

    friend ostream& operator<<(ostream& os, const Complex<T>& c) {
        os << c.real_ << " + " << c.imag_ << "i";
        return os;
    }

    friend istream& operator>>(istream& is, Complex<T>& c) {
        is >> c.real_ >> c.imag_;
        return is;
    }
};

task5.cpp

#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();
}