实验05

1.实验任务1

publisher.hpp

#pragma once
#include<string>

class Publisher{
public:
    Publisher(const std::string &name_="");
    virtual ~Publisher()=default;

public:
    virtual void publish() const=0;
    virtual void use() const=0;

protected:
    std::string name;
};

class Book:public Publisher{
public:
    Book(const std::string &name_="",const std::string &author_="");

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

private:
    std::string author;
};

class Film:public Publisher{
public:
    Film(const std::string &name_="",const std::string &director_="");

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

private:
    std::string director;
};

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

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

private:
    std::string artist;
};

publisher.cpp

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

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

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::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::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';
}

源代码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();
}

运行结果截图：

问题一：1.Publisher 类中包含了两个纯虚函数，所以它是抽象类。

2.不能；因为Publisher是抽象类，不允许实例化对象。抽象类只能作为基类被继承。

问题二：

1.void publish() const override;void use() const override;

2.会引发编译错误，error: cannot initialize virtual function 'virtual void Publisher::publish() const' with non-const version。

问题三：

1.ptr 的声明类型是 指向Publisher的指针。

2.Book 对象（"Harry Potter"）Film对象（"The Godfather"）Music对象（"Blowing in the wind"）

3.声明为 virtual是为了支持多态销毁。若删除 virtual，则只会调用基类析构函数，造成资源泄漏。

2.实验任务2

book.hpp

#pragma once
#include<string>

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;
    std::string author;
    std::string translator;
    std::string isbn;
    double price;
};

book.cpp

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

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_} {
}

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"

class BookSale{
public:
    BookSale(const Book &rb_, double sales_price_, int sales_amount_);
    int get_amount() const;
    double get_revenue() const;

    friend std::ostream& operator<<(std::ostream &out,const BookSale &item);

private:
    Book rb;
    double sales_price;
    int sales_amount;
};

booksale.cpp

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

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;
}

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>

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;

    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);
    }

    sort(sales_lst.begin(), sales_lst.end(), compare_by_amount);
    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();
}

运行结果截图：

 

问题1：

（1）两处，用于Book类型和BookSale类型

（2）for(auto &t: sales_lst) { cout << t << endl; cout << string(40, '-') << endl; }

问题2：

（1）先定义存储BookSale对象的容器，然后调用std::sort函数，自定义比较函数compare_by_amount实现按销售数量降序排序。

（2） std::sort(sales_lst.begin(), sales_lst.end(),

                       [](const BookSale& a, const BookSale& b) -> bool {

　　　　　　　　return a.get_amount() > b.get_amount(); 

});

3.实验任务3

task3_1.cpp

#include <iostream>

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';
}

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();
}

#include <iostream>

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';
}

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>

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();
}

 4.实验任务4

Pet.hpp

#pragma once
#include <string>

class MachinePet {
public:
    explicit MachinePet(const std::string& nickname) : nickname(nickname) {}
    virtual ~MachinePet() = default;

    const std::string& get_nickname() const {
        return nickname;
    }

    virtual std::string talk() const = 0;

protected:
    std::string nickname;
};

class PetCat : public MachinePet {
public:
    explicit PetCat(const std::string& nickname) : MachinePet(nickname) {}
    std::string talk() const override {
        return "Meow!";
    }
};

class PetDog : public MachinePet {
public:
    explicit PetDog(const std::string& nickname) : MachinePet(nickname) {}
    std::string talk() const override {
        return "Woof!";
    }
};

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;
    }
}

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() {
    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();
}

运行结果截图：

5.实验任务5

Complex.hpp

#pragma once
#include <iostream>

template<typename T = double>
class Complex {
public:
    Complex() : real(0), imag(0) {}
    Complex(T r, T i = 0) : real(r), imag(i) {}

    T get_real() const {
        return real;
    }

    T get_imag() const {
        return imag;
    }

    Complex& operator+=(const Complex& rhs) {
        real += rhs.real;
        imag += rhs.imag;
        return *this;
    }

    bool operator==(const Complex& rhs) const {
        return real == rhs.real && imag == rhs.imag;
    }

    bool operator!=(const Complex& rhs) const {
        return !(*this == rhs);
    }

private:
    T real;
    T imag;
};

template<typename T>
Complex<T> operator+(const Complex<T>& lhs, const Complex<T>& rhs) {
    return Complex<T>(lhs.get_real() + rhs.get_real(), lhs.get_imag() + rhs.get_imag());
}

template<typename T>
std::ostream& operator<<(std::ostream& out, const Complex<T>& c) {
    out << "(" << c.get_real() << "," << c.get_imag() << ")";
    return out;
}

template<typename T>
std::istream& operator>>(std::istream& in, Complex<T>& c) {
    T r, i;
    char ch;
    in >> ch;
    if (ch == '(') {
        in >> r >> ch >> i >> ch;
    } else {
        in.putback(ch);
        in >> r >> i;
    }
    c = Complex<T>(r, i);
    return in;
}

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();
}

运行结果截图：