实验作业5

实验任务1

代码

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();
}

 

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问题回答

问题1：抽象类机制 

(1) Publisher 是抽象类，因为它包含纯虚函数。依据：publisher.hpp 中的 

virtual void publish() const = 0; 

virtual void use() const = 0;

(2) 在 main.cpp 中写 Publisher p; 不能编译通过，因为抽象类不能实例化。

问题2：纯虚函数与接口继承 

(1) Book、Film、Music 必须实现这两个函数： 

void publish() const override; 

void use() const override;

(2) 若在 Film 的实现中去掉 const，则会出现“没有与基类虚函数匹配的成员函数”之类的报错

error: ‘void Film::publish()’ marked ‘override’, but does not override 

error: ‘void Film::use()’ marked ‘override’, but does not override

问题3：运行时多态与虚析构

(1) test1() 中 ptr 的声明类型是 Publisher*。

(2) ptr->publish() 时实际对象类型依次是：Book、Film、Music。

(3) Publisher 的析构函数需要是 virtual，以便 delete ptr 时正确调用派生类析构函数；若删除 virtual，则会导致派生类析构函数不被调用，出现资源未释放或行为未定义的问题。

实验任务2

代码

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();
}

 

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>// 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
};

 

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问题回答

问题1

(1) 共重载了2处，分别用于类型Book和类型BookSale。

(2) 使用重载<<输出对象的代码：

cout << t << endl;

out << item.rb << '\n'

问题2

(1) 先定义比较函数compare_by_amount，再调用sort并把该比较函数作为第三个参数，从而实现按销售数量降序排序。

(2) 使用lambda可写为 sort(sales_lst.begin(), sales_lst.end(), [](const BookSale &a, const BookSale &b){ return a.get_amount() > b.get_amount(); });

实验任务4

代码

pet.hpp

#ifndef PET_HPP
#define PET_HPP#include <string>class MachinePet {
protected:std::string nickname;public:explicit MachinePet(const std::string &name) : nickname(name) {}virtual ~MachinePet() = default;std::string get_nickname() const {return nickname;}virtual std::string talk() const = 0;
};class PetCat : public MachinePet {
public:explicit PetCat(const std::string &name) : MachinePet(name) {}std::string talk() const override {return "miao wu~";}
};class PetDog : public MachinePet {
public:explicit PetDog(const std::string &name) : MachinePet(name) {}std::string talk() const override {return "wang wang~";}
};#endif

 

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();
}

 

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实验任务5

代码

Complex.hpp

#ifndef COMPLEX_HPP
#define COMPLEX_HPP#include <iostream>template<typename T>
class Complex {
private:T real;T imag;public:Complex() : real(0), imag(0) {}Complex(T r, T i = 0) : real(r), imag(i) {}Complex(const Complex& other) : real(other.real), imag(other.imag) {}T get_real() const { return real; }T get_imag() const { return imag; }// c1 + c2Complex operator+(const Complex& rhs) const {return Complex(real + rhs.real, imag + rhs.imag);}// c1 += c2Complex& operator+=(const Complex& rhs) {real += rhs.real;imag += rhs.imag;return *this;}// c1 == c2bool operator==(const Complex& rhs) const {return (real == rhs.real) && (imag == rhs.imag);}template<typename U>friend std::ostream& operator<<(std::ostream& os, const Complex<U>& c);template<typename U>friend std::istream& operator>>(std::istream& is, Complex<U>& c);
};template<typename T>
std::ostream& operator<<(std::ostream& os, const Complex<T>& c) {os << c.real;if (c.imag < 0) os << " - ";else os << " + ";os << abs(c.imag) << 'i';return os;
}template<typename T>
std::istream& operator>>(std::istream& is, Complex<T>& c) {is >> c.real >> c.imag;return is;
}#endif

 

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();
}

 

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