实验五
任务1：
任务1代码：
1 #pragma once 2 3 #include <string> 4 5 // 发行/出版物类：Publisher （抽象类） 6 class Publisher { 7 public: 8 Publisher(const std::string &name_ = ""); // 构造函数 9 virtual ~Publisher() = default; 10 11 public: 12 virtual void publish() const = 0; // 纯虚函数，作为接口继承 13 virtual void use() const = 0; // 纯虚函数，作为接口继承 14 15 protected: 16 std::string name; // 发行/出版物名称 17 }; 18 19 // 图书类: Book 20 class Book: public Publisher { 21 public: 22 Book(const std::string &name_ = "", const std::string &author_ = ""); // 构造函数 23 24 public: 25 void publish() const override; // 接口 26 void use() const override; // 接口 27 28 private: 29 std::string author; // 作者 30 }; 31 32 // 电影类: Film 33 class Film: public Publisher { 34 public: 35 Film(const std::string &name_ = "", const std::string &director_ = ""); // 构造函数 36 37 public: 38 void publish() const override; // 接口 39 void use() const override; // 接口 40 41 private: 42 std::string director; // 导演 43 }; 44 45 46 // 音乐类：Music 47 class Music: public Publisher { 48 public: 49 Music(const std::string &name_ = "", const std::string &artist_ = ""); 50 51 public: 52 void publish() const override; // 接口 53 void use() const override; // 接口 54 55 private: 56 std::string artist; // 音乐艺术家名称 57 };
1 #include <iostream> 2 #include <string> 3 #include "publisher.hpp" 4 5 // Publisher类：实现 6 Publisher::Publisher(const std::string &name_): name {name_} { 7 } 8 9 10 // Book类: 实现 11 Book::Book(const std::string &name_ , const std::string &author_ ): Publisher{name_}, author{author_} { 12 } 13 14 void Book::publish() const { 15 std::cout << "Publishing book《" << name << "》 by " << author << '\n'; 16 } 17 18 void Book::use() const { 19 std::cout << "Reading book 《" << name << "》 by " << author << '\n'; 20 } 21 22 23 // Film类：实现 24 Film::Film(const std::string &name_, const std::string &director_):Publisher{name_},director{director_} { 25 } 26 27 void Film::publish() const { 28 std::cout << "Publishing film <" << name << "> directed by " << director << '\n'; 29 } 30 31 void Film::use() const { 32 std::cout << "Watching film <" << name << "> directed by " << director << '\n'; 33 } 34 35 36 // Music类：实现 37 Music::Music(const std::string &name_, const std::string &artist_): Publisher{name_}, artist{artist_} { 38 } 39 40 void Music::publish() const { 41 std::cout << "Publishing music <" << name << "> by " << artist << '\n'; 42 } 43 44 void Music::use() const { 45 std::cout << "Listening to music <" << name << "> by " << artist << '\n'; 46 }
1 #include <memory> 2 #include <iostream> 3 #include <vector> 4 #include "publisher.hpp" 5 6 void test1() { 7 std::vector<Publisher *> v; 8 9 v.push_back(new Book("Harry Potter", "J.K. Rowling")); 10 v.push_back(new Film("The Godfather", "Francis Ford Coppola")); 11 v.push_back(new Music("Blowing in the wind", "Bob Dylan")); 12 13 for(Publisher *ptr: v) { 14 ptr->publish(); 15 ptr->use(); 16 std::cout << '\n'; 17 delete ptr; 18 } 19 } 20 21 void test2() { 22 std::vector<std::unique_ptr<Publisher>> v; 23 24 v.push_back(std::make_unique<Book>("Harry Potter", "J.K. Rowling")); 25 v.push_back(std::make_unique<Film>("The Godfather", "Francis Ford Coppola")); 26 v.push_back(std::make_unique<Music>("Blowing in the wind", "Bob Dylan")); 27 28 for(const auto &ptr: v) { 29 ptr->publish(); 30 ptr->use(); 31 std::cout << '\n'; 32 } 33 } 34 35 void test3() { 36 Book book("A Philosophy of Software Design", "John Ousterhout"); 37 book.publish(); 38 book.use(); 39 } 40 41 int main() { 42 std::cout << "运行时多态：纯虚函数、抽象类\n"; 43 44 std::cout << "\n测试1: 使用原始指针\n"; 45 test1(); 46 47 std::cout << "\n测试2: 使用智能指针\n"; 48 test2(); 49 50 std::cout << "\n测试3: 直接使用类\n"; 51 test3(); 52 }
任务1截图：
任务1问题：
1. 1）声明了纯虚函数。依据：virtual void publish() const = 0;virtual void use() const = 0;
2）不能通过，因为Publisher类是抽象类，抽象类不能实例化
2.
1）void publish() const override;void use() const override;
2）error: invalid covariant return type for 'virtual void Film::publish()' error: overriding 'virtual void Publisher::publish() const' error: invalid covariant return type for 'virtual void Film::use()' error: overriding 'virtual void Publisher::use() const'
3.
1）声明类型是指向Publisher类的指针
2)1.Book类对象 2.Film类对象 3.Music类对象
3)为了能够正确调用子类的析构函数；如果基类析构函数不声明为virtual，那么无法通过基类指针调用子类析构函数删除子类，会导致内存泄露
任务2：
任务2代码：
1 #pragma once 2 #include <string> 3 4 // 图书描述信息类Book: 声明 5 class Book { 6 public: 7 Book(const std::string &name_, 8 const std::string &author_, 9 const std::string &translator_, 10 const std::string &isbn_, 11 double price_); 12 13 friend std::ostream& operator<<(std::ostream &out, const Book &book); 14 15 private: 16 std::string name; // 书名 17 std::string author; // 作者 18 std::string translator; // 译者 19 std::string isbn; // isbn号 20 double price; // 定价 21 };
1 #pragma once 2 3 #include <string> 4 #include "book.hpp" 5 6 // 图书销售记录类BookSales：声明 7 class BookSale { 8 public: 9 BookSale(const Book &rb_, double sales_price_, int sales_amount_); 10 int get_amount() const; // 返回销售数量 11 double get_revenue() const; // 返回营收 12 13 friend std::ostream& operator<<(std::ostream &out, const BookSale &item); 14 15 private: 16 Book rb; 17 double sales_price; // 售价 18 int sales_amount; // 销售数量 19 };
1 #include <iomanip> 2 #include <iostream> 3 #include <string> 4 #include "book.hpp" 5 6 7 // 图书描述信息类Book: 实现 8 Book::Book(const std::string &name_, 9 const std::string &author_, 10 const std::string &translator_, 11 const std::string &isbn_, 12 double price_):name{name_}, author{author_}, translator{translator_}, isbn{isbn_}, price{price_} { 13 } 14 15 // 运算符<<重载实现 16 std::ostream& operator<<(std::ostream &out, const Book &book) { 17 using std::left; 18 using std::setw; 19 20 out << left; 21 out << setw(15) << "书名:" << book.name << '\n' 22 << setw(15) << "作者:" << book.author << '\n' 23 << setw(15) << "译者:" << book.translator << '\n' 24 << setw(15) << "ISBN:" << book.isbn << '\n' 25 << setw(15) << "定价:" << book.price; 26 27 return out; 28 }
1 #include <iomanip> 2 #include <iostream> 3 #include <string> 4 #include "booksale.hpp" 5 6 // 图书销售记录类BookSales：实现 7 BookSale::BookSale(const Book &rb_, 8 double sales_price_, 9 int sales_amount_): rb{rb_}, sales_price{sales_price_}, sales_amount{sales_amount_} { 10 } 11 12 int BookSale::get_amount() const { 13 return sales_amount; 14 } 15 16 double BookSale::get_revenue() const { 17 return sales_amount * sales_price; 18 } 19 20 // 运算符<<重载实现 21 std::ostream& operator<<(std::ostream &out, const BookSale &item) { 22 using std::left; 23 using std::setw; 24 25 out << left; 26 out << item.rb << '\n' 27 << setw(15) << "售价:" << item.sales_price << '\n' 28 << setw(15) << "销售数量:" << item.sales_amount << '\n' 29 << setw(15) << "营收:" << item.get_revenue(); 30 31 return out; 32 }
1 #include <algorithm> 2 #include <iomanip> 3 #include <iostream> 4 #include <string> 5 #include <vector> 6 #include "booksale.hpp" 7 8 // 按图书销售数量比较 9 bool compare_by_amount(const BookSale &x1, const BookSale &x2) { 10 return x1.get_amount() > x2.get_amount(); 11 } 12 13 void test() { 14 using std::cin; 15 using std::cout; 16 using std::getline; 17 using std::sort; 18 using std::string; 19 using std::vector; 20 using std::ws; 21 22 vector<BookSale> sales_records; // 图书销售记录表 23 24 int books_number; 25 cout << "录入图书数量: "; 26 cin >> books_number; 27 28 cout << "录入图书销售记录\n"; 29 for(int i = 0; i < books_number; ++i) { 30 string name, author, translator, isbn; 31 double price; 32 cout << string(20, '-') << "第" << i+1 << "本图书信息录入" << string(20, '-') << '\n'; 33 cout << "录入书名: "; getline(cin>>ws, name); 34 cout << "录入作者: "; getline(cin>>ws, author); 35 cout << "录入译者: "; getline(cin>>ws, translator); 36 cout << "录入isbn: "; getline(cin>>ws, isbn); 37 cout << "录入定价: "; cin >> price; 38 39 Book book(name, author, translator, isbn, price); 40 41 double sales_price; 42 int sales_amount; 43 44 cout << "录入售价: "; cin >> sales_price; 45 cout << "录入销售数量: "; cin >> sales_amount; 46 47 BookSale record(book, sales_price, sales_amount); 48 sales_records.push_back(record); 49 } 50 51 // 按销售册数排序 52 sort(sales_records.begin(), sales_records.end(), compare_by_amount); 53 54 // 按销售册数降序输出图书销售信息 55 cout << string(20, '=') << "图书销售统计" << string(20, '=') << '\n'; 56 for(auto &record: sales_records) { 57 cout << record << '\n'; 58 cout << string(40, '-') << '\n'; 59 } 60 } 61 62 int main() { 63 test(); 64 }
任务2截图：
任务2问题：
1.
1）两处，第一处用于Book类型（std::ostream& operator<<(std::ostream &out, const Book &book);）第二处用于BookSale类型（std::ostream& operator<<(std::ostream &out, const BookSale &item);）
2）out << item.rb << '\n'; cout << t << endl;
2.
1）通过compare_by_amount函数和标准库函数std::sort
2)lambda表达式： sort(sales_lst.begin(), sales_lst.end(), [](const BookSale &x1, const BookSale &x2) { return x1.get_amount() > x2.get_amount(); });
任务4：
任务4代码：
1 #pragma once 2 #include<iostream> 3 #include<string> 4 5 class MachinePet { 6 public: 7 MachinePet(const std::string& nickname):_nickname(nickname){} 8 virtual ~MachinePet() = default; 9 virtual std::string get_nickname()const; 10 virtual std::string talk()const = 0; 11 12 13 14 protected: 15 std::string _nickname; 16 }; 17 18 std::string MachinePet::get_nickname() const 19 { 20 return _nickname; 21 } 22 23 class PetCat :public MachinePet { 24 public: 25 PetCat(const std::string& nickname) :MachinePet(nickname) {} 26 27 std::string talk() const override 28 { 29 return "miao wu~"; 30 } 31 }; 32 33 34 class PetDog :public MachinePet 35 { 36 public: 37 PetDog(const std::string& nickname) :MachinePet(nickname) {} 38 39 std::string talk() const override 40 { 41 return "wang wang~"; 42 } 43 };
1 #include <iostream> 2 #include <memory> 3 #include <vector> 4 #include "pet.hpp" 5 6 void test1() { 7 std::vector<MachinePet*> pets; 8 9 pets.push_back(new PetCat("miku")); 10 pets.push_back(new PetDog("da huang")); 11 12 for (MachinePet* ptr : pets) { 13 std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n'; 14 delete ptr; // 须手动释放资源 15 } 16 } 17 18 void test2() { 19 std::vector<std::unique_ptr<MachinePet>> pets; 20 21 pets.push_back(std::make_unique<PetCat>("miku")); 22 pets.push_back(std::make_unique<PetDog>("da huang")); 23 24 for (auto const& ptr : pets) 25 std::cout << ptr->get_nickname() << " says " << ptr->talk() << '\n'; 26 } 27 28 void test3() { 29 // MachinePet pet("little cutie"); // 编译报错：无法定义抽象类对象 30 31 const PetCat cat("miku"); 32 std::cout << cat.get_nickname() << " says " << cat.talk() << '\n'; 33 34 const PetDog dog("da huang"); 35 std::cout << dog.get_nickname() << " says " << dog.talk() << '\n'; 36 } 37 38 int main() { 39 std::cout << "测试1: 使用原始指针\n"; 40 test1(); 41 42 std::cout << "\n测试2: 使用智能指针\n"; 43 test2(); 44 45 std::cout << "\n测试3: 直接使用类\n"; 46 test3(); 47 }
任务4截图：
任务5：
任务5代码：
1 #include<iostream> 2 #include<string> 3 #include<string> 4 5 template<typename T> 6 7 class Complex { 8 private: 9 T _real; 10 T _imag; 11 public: 12 Complex():_real(0),_imag(0){} 13 Complex(T real,T imag):_real(real),_imag(imag){} 14 Complex(const Complex<T>& other) 15 { 16 _real = other._real; 17 _imag = other._imag; 18 } 19 20 T get_real() const 21 { 22 return _real; 23 } 24 T get_imag() const 25 { 26 return _imag; 27 } 28 //重载运算符+= 29 Complex<T>& operator+=(const Complex<T>& other) 30 { 31 _real += other._real; 32 _imag += other._imag; 33 return *this; 34 } 35 36 //重载运算符+ 37 38 Complex<T> operator+(const Complex<T>& other) 39 { 40 return Complex(_real + other._real,_imag+other._imag); 41 } 42 43 //重载运算符== 44 bool operator==(const Complex<T>& other)const 45 { 46 return (_real == other._real && _imag == other._imag); 47 } 48 49 //重载运算符<< 50 friend std::ostream& operator << (std::ostream & out, const Complex<T>& c) 51 { 52 out << c._real; 53 if (c._imag >= 0) out << " + "; 54 if (c._imag < 0) 55 { 56 out << " - "; 57 } 58 out << (c._imag > 0 ? c._imag : -c._imag) << "i"; 59 return out; 60 } 61 62 //重载运算符>> 63 friend std::istream& operator>>(std::istream& in, Complex<T>& c) 64 { 65 in >> c._real >> c._imag; 66 return in; 67 } 68 69 };
1 #include <iostream> 2 #include "Complex.hpp" 3 4 void test1() { 5 using std::cout; 6 using std::boolalpha; 7 8 Complex<int> c1(2, -5), c2(c1); 9 10 cout << "c1 = " << c1 << '\n'; 11 cout << "c2 = " << c2 << '\n'; 12 cout << "c1 + c2 = " << c1 + c2 << '\n'; 13 14 c1 += c2; 15 cout << "c1 = " << c1 << '\n'; 16 cout << boolalpha << (c1 == c2) << '\n'; 17 } 18 19 void test2() { 20 using std::cin; 21 using std::cout; 22 23 Complex<double> c1, c2; 24 cout << "Enter c1 and c2: "; 25 cin >> c1 >> c2; 26 cout << "c1 = " << c1 << '\n'; 27 cout << "c2 = " << c2 << '\n'; 28 29 const Complex<double> c3(c1); 30 cout << "c3.real = " << c3.get_real() << '\n'; 31 cout << "c3.imag = " << c3.get_imag() << '\n'; 32 } 33 34 int main() { 35 std::cout << "自定义类模板Complex测试1: \n"; 36 test1(); 37 38 std::cout << "\n自定义类模板Complex测试2: \n"; 39 test2(); 40 }
任务5截图：
总结：
在实验五中用模板类重载运算符时，参数需要显式绑定T，不然会出现编译错误。
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