Lab examples

#include <string>
#include <vector>
#include <iostream>

using namespace std;

class Mammal {
private:
    string name;

public:
    virtual string voice() const {
        return "Not implemented yet\n";
    }
};

class Cat : public Mammal {
public:
    string murmur() const {
        return "murmur\n";
    }

    string voice() const override {
        return "meow\n";
    }
};

class Dog : public Mammal {
public:
    string voice() const override {
        return "Waff!\n";
    }
};

int main() {
    Cat c;
    Dog d;
    vector<Mammal> zoo;
    zoo.push_back(c);
    zoo.push_back(d);
    cout << zoo[0].voice() << endl;

    vector<Mammal*> zoo2;
    zoo2.push_back(&c);
    zoo2.push_back(&d);
    cout << zoo2[0]->voice() << endl;
}
======================================================
#include <iostream>
#include <string>

using namespace std;

class Old {
protected:
    int x = 3;
};

class New: public Old {
protected:
    int x = 4;
public:
    New() {
        cout << x << " " << Old::x << endl;
    }
};

class Newest: New {
protected:
    string x = "5";
public:
    Newest() {
        cout << this->x << " " << New::x << " " << Old::x << endl;
    }
};

int main() {
    Old();
    New();
    Newest();
}
=============================================
#include <iostream>
#include <string>
using namespace std;

enum {
    FOO = 1, BAR = 2, BUZZ = 4
};

enum Colors {
    RED, BLUE
};

enum Numbers {
    // можно переопределять начал значения
    ONE = 1, TWO, SEVEN = 7, EIGHT
};

enum class TheColors {
    THE_RED, THE_BLUE, THE_VIOLET
};

enum class TheColors2 : int {
    THE_RED = 1, THE_BLUE = 4, THE_VIOLET = 5
};

int main() {
    cout << sizeof(Colors) << " " << sizeof(RED) << " " << Colors::BLUE << endl;
    // это константы, которые экспортируют свои имена в пространство имён
    int x = 2 + RED;
    Colors y = RED; // y++; хотя они и защищены явно от арифметики
    y = static_cast<Colors>(
            static_cast<int>(y) + 1
        );
    cout << (y == BLUE ? "DA": "NET") << endl;

    cout << ONE << TWO << SEVEN << EIGHT << endl;
    // часто использовались в C как множества (настроек, ключей, ...)
    auto some = FOO | BUZZ;
    if ((some & BUZZ) == BUZZ) {
        cout << "We have BUZZ" << endl;
    }

    //===========================================

    TheColors color = TheColors::THE_RED; // просто THE_RED не сработает

    TheColors2 color2 = static_cast<TheColors2>(
                                static_cast<int>(TheColors2::THE_RED) |
                                static_cast<int>(TheColors2::THE_BLUE)
                        );
    if (color2 == TheColors2::THE_VIOLET) {
        cout << "WOW" << endl;
    }
}