实验五
任务一
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'; }
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 };
task1.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(); }
运行结果
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。
含纯虚函数的类是抽象类
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
（2）如果在 main.cpp 里直接写 Publisher p; 能否编译通过？为什么？
不能 不能定义抽象类对象
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。
virtual void publish() const override;
virtual 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？
Film中重载函数定义与基类函数不匹配
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？
基类指针
（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）
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？
可删除派生类对象
仅调用基类析构函数 派生类无法释放 内存泄漏
任务二
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; }
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 };
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; }
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 };
task2.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(); }
运行结果
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？
两处 Book和BookSale
（2）找出使用重载 << 输出对象的代码，写在下面。
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();
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？
sort(sales_records.begin(), sales_records.end(), compare_by_amount);
bool compare_by_amount(const BookSale &x1, const BookSale &x2) {
return x1.get_amount() > x2.get_amount();
}
（2）拓展（选答*）：如果使用lambda表达式，如何实现"按销售数量降序排序"？
任务三
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(); }
运行结果
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(); }
运行结果
任务四
pet.hpp
#pragma once #include <string> class MachinePet{ public: MachinePet(const std::string& nickname_):nickname(nickname_) {} virtual ~MachinePet()=default; std::string get_nickname()const{return nickname; } virtual std::string talk()const=0; protected: std::string nickname; }; class PetCat:public MachinePet{ public: PetCat(const std::string& nickname_):MachinePet(nickname_){} std::string talk()const override{return "miao wu~"; } }; class PetDog:public MachinePet { public: PetDog(const std::string& nickname_) : MachinePet(nickname_){} std::string talk()const override{return "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(); }
运行结果
任务五
Complex.hpp
#pragma once #include <iostream> template <typename T> class Complex{ public: Complex():real(0),imag(0){} Complex(T r,T i):real(r),imag(i){} 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){ this->real+=other.real; this->imag+=other.imag; return *this; } friend Complex<T>operator+(Complex<T> lhs,const Complex<T>& rhs){ lhs+=rhs; return lhs; } bool operator==(const Complex<T>& other)const{ return(this->real==other.real)&&(this->imag==other.imag); } friend std::istream& operator>>(std::istream& in, Complex<T>& c){ in>>c.real>>c.imag; return in; } friend std::ostream& operator<<(std::ostream& out,const Complex<T>& c){ out<<c.real; if(c.imag>=0)out<<"+"; out<<c.imag<<"i"; return out; } private: T real; T imag; };
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(); }
运行结果
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