第2章：課題の実装

はじめに

本章では、CPP Module 01の各演習を実装します。

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1. ex00: BraiiiiiiinnnzzzZ

1.1 課題の要件

  • Zombieクラスを作成
  • スタックとヒープでのオブジェクト生成を比較
  • newZombie関数でヒープに生成
  • randomChump関数でスタックに生成

    • 1.2 実装

    // Zombie.hpp
#ifndef ZOMBIE_HPP
#define ZOMBIE_HPP

#include <string>

class Zombie {
private:
    std::string _name;

public:
    Zombie();
    Zombie(const std::string& name);
    ~Zombie();
    void announce() const;
};

Zombie* newZombie(std::string name);
void randomChump(std::string name);

#endif

// Zombie.cpp
#include "Zombie.hpp"
#include <iostream>

Zombie::Zombie() : _name("Unnamed") {}

Zombie::Zombie(const std::string& name) : _name(name) {}

Zombie::~Zombie() {
    std::cout << _name << " is destroyed" << std::endl;
}

void Zombie::announce() const {
    std::cout << _name << ": BraiiiiiiinnnzzzZ..." << std::endl;
}

// newZombie.cpp
#include "Zombie.hpp"

Zombie* newZombie(std::string name) {
    return new Zombie(name);
}

// randomChump.cpp
#include "Zombie.hpp"

void randomChump(std::string name) {
    Zombie zombie(name);
    zombie.announce();
}

// main.cpp
#include "Zombie.hpp"

int main() {
    // ヒープに生成
    Zombie* heapZombie = newZombie("HeapZombie");
    heapZombie->announce();

    // スタックに生成
    randomChump("StackZombie");

    // ヒープのゾンビを削除
    delete heapZombie;

    return 0;
}

    ---

    2. ex01: Moar brainz!

    2.1 課題の要件

  • 複数のZombieを一度に生成
  • zombieHorde関数で配列を返す

    • 2.2 実装

    // Zombie.hpp
#ifndef ZOMBIE_HPP
#define ZOMBIE_HPP

#include <string>

class Zombie {
private:
    std::string _name;

public:
    Zombie();
    ~Zombie();
    void setName(const std::string& name);
    void announce() const;
};

Zombie* zombieHorde(int N, std::string name);

#endif

// zombieHorde.cpp
#include "Zombie.hpp"

Zombie* zombieHorde(int N, std::string name) {
    if (N <= 0)
        return NULL;

    Zombie* horde = new Zombie[N];
    for (int i = 0; i < N; i++) {
        horde[i].setName(name);
    }
    return horde;
}

// main.cpp
#include "Zombie.hpp"

int main() {
    int N = 5;
    Zombie* horde = zombieHorde(N, "Zombie");

    for (int i = 0; i < N; i++) {
        horde[i].announce();
    }

    delete[] horde;
    return 0;
}

    ---

    3. ex02: HI THIS IS BRAIN

    3.1 課題の要件

  • 文字列変数、ポインタ、参照のアドレスと値を表示

    • 3.2 実装

    #include <iostream>
#include <string>

int main() {
    std::string str = "HI THIS IS BRAIN";
    std::string* stringPTR = &str;
    std::string& stringREF = str;

    std::cout << "Address of str:       " << &str << std::endl;
    std::cout << "Address of stringPTR: " << stringPTR << std::endl;
    std::cout << "Address of stringREF: " << &stringREF << std::endl;

    std::cout << "Value of str:         " << str << std::endl;
    std::cout << "Value of stringPTR:   " << *stringPTR << std::endl;
    std::cout << "Value of stringREF:   " << stringREF << std::endl;

    return 0;
}

    ---

    4. ex03: Unnecessary violence

    4.1 課題の要件

  • Weaponクラスを作成
  • HumanAとHumanBクラスを作成
  • HumanAは参照で武器を持つ
  • HumanBはポインタで武器を持つ

    • 4.2 実装

    // Weapon.hpp
#ifndef WEAPON_HPP
#define WEAPON_HPP

#include <string>

class Weapon {
private:
    std::string _type;

public:
    Weapon(const std::string& type);
    const std::string& getType() const;
    void setType(const std::string& type);
};

#endif

// HumanA.hpp
#ifndef HUMANA_HPP
#define HUMANA_HPP

#include "Weapon.hpp"
#include <string>

class HumanA {
private:
    std::string _name;
    Weapon& _weapon;  // 参照：常に武器を持つ

public:
    HumanA(const std::string& name, Weapon& weapon);
    void attack() const;
};

#endif

// HumanB.hpp
#ifndef HUMANB_HPP
#define HUMANB_HPP

#include "Weapon.hpp"
#include <string>

class HumanB {
private:
    std::string _name;
    Weapon* _weapon;  // ポインタ：武器を持たない可能性

public:
    HumanB(const std::string& name);
    void setWeapon(Weapon& weapon);
    void attack() const;
};

#endif

// HumanA.cpp
#include "HumanA.hpp"
#include <iostream>

HumanA::HumanA(const std::string& name, Weapon& weapon)
    : _name(name), _weapon(weapon) {}

void HumanA::attack() const {
    std::cout << _name << " attacks with their " << _weapon.getType() << std::endl;
}

// HumanB.cpp
#include "HumanB.hpp"
#include <iostream>

HumanB::HumanB(const std::string& name) : _name(name), _weapon(NULL) {}

void HumanB::setWeapon(Weapon& weapon) {
    _weapon = &weapon;
}

void HumanB::attack() const {
    if (_weapon) {
        std::cout << _name << " attacks with their " << _weapon->getType() << std::endl;
    } else {
        std::cout << _name << " has no weapon" << std::endl;
    }
}

    ---

    5. ex04: Sed is for losers

    5.1 課題の要件

  • ファイル内の文字列を置換
  • std::string::replaceは使用禁止

    • 5.2 実装

    #include <iostream>
#include <fstream>
#include <string>

std::string replaceAll(const std::string& content,
                       const std::string& s1,
                       const std::string& s2) {
    std::string result;
    size_t pos = 0;
    size_t prevPos = 0;

    while ((pos = content.find(s1, prevPos)) != std::string::npos) {
        result += content.substr(prevPos, pos - prevPos);
        result += s2;
        prevPos = pos + s1.length();
    }
    result += content.substr(prevPos);

    return result;
}

int main(int argc, char** argv) {
    if (argc != 4) {
        std::cerr << "Usage: " << argv[0] << " <filename> <s1> <s2>" << std::endl;
        return 1;
    }

    std::string filename = argv[1];
    std::string s1 = argv[2];
    std::string s2 = argv[3];

    if (s1.empty()) {
        std::cerr << "Error: s1 cannot be empty" << std::endl;
        return 1;
    }

    std::ifstream inFile(filename.c_str());
    if (!inFile) {
        std::cerr << "Error: Cannot open file" << std::endl;
        return 1;
    }

    std::string content;
    std::string line;
    while (std::getline(inFile, line)) {
        if (!content.empty())
            content += '\n';
        content += line;
    }
    inFile.close();

    std::string replaced = replaceAll(content, s1, s2);

    std::ofstream outFile((filename + ".replace").c_str());
    if (!outFile) {
        std::cerr << "Error: Cannot create output file" << std::endl;
        return 1;
    }
    outFile << replaced;
    outFile.close();

    return 0;
}

    ---

    6. ex05: Harl 2.0

    6.1 課題の要件

  • Harlクラスにポインタtoメンバ関数を使用
  • 4つのログレベル: DEBUG, INFO, WARNING, ERROR

    • 6.2 実装

    // Harl.hpp
#ifndef HARL_HPP
#define HARL_HPP

#include <string>

class Harl {
private:
    void debug();
    void info();
    void warning();
    void error();

public:
    void complain(std::string level);
};

#endif

// Harl.cpp
#include "Harl.hpp"
#include <iostream>

void Harl::debug() {
    std::cout << "[ DEBUG ]" << std::endl;
    std::cout << "I love having extra bacon..." << std::endl;
}

void Harl::info() {
    std::cout << "[ INFO ]" << std::endl;
    std::cout << "I cannot believe adding extra bacon costs more money..." << std::endl;
}

void Harl::warning() {
    std::cout << "[ WARNING ]" << std::endl;
    std::cout << "I think I deserve to have some extra bacon for free..." << std::endl;
}

void Harl::error() {
    std::cout << "[ ERROR ]" << std::endl;
    std::cout << "This is unacceptable! I want to speak to the manager now." << std::endl;
}

void Harl::complain(std::string level) {
    void (Harl::*functions[4])() = {
        &Harl::debug,
        &Harl::info,
        &Harl::warning,
        &Harl::error
    };
    std::string levels[4] = {"DEBUG", "INFO", "WARNING", "ERROR"};

    for (int i = 0; i < 4; i++) {
        if (levels[i] == level) {
            (this->*functions[i])();
            return;
        }
    }
    std::cout << "Unknown level: " << level << std::endl;
}

    ---

    7. ex06: Harl filter

    7.1 課題の要件

  • switch文を使用
  • 指定レベル以上のログを表示（fall-through）

    • 7.2 実装

    // harlFilter.cpp
#include "Harl.hpp"
#include <iostream>

int main(int argc, char** argv) {
    if (argc != 2) {
        std::cerr << "Usage: " << argv[0] << " <level>" << std::endl;
        return 1;
    }

    Harl harl;
    std::string level = argv[1];
    int levelIndex = -1;

    if (level == "DEBUG") levelIndex = 0;
    else if (level == "INFO") levelIndex = 1;
    else if (level == "WARNING") levelIndex = 2;
    else if (level == "ERROR") levelIndex = 3;

    switch (levelIndex) {
        case 0:
            harl.debug();
            // fall through
        case 1:
            harl.info();
            // fall through
        case 2:
            harl.warning();
            // fall through
        case 3:
            harl.error();
            break;
        default:
            std::cout << "[ Probably complaining about insignificant problems ]" << std::endl;
    }

    return 0;
}

    ---

    まとめ

    本章で実装した内容：

  • ex00-01: 動的メモリ割り当て
  • ex02: ポインタと参照の違い
  • ex03: 参照とポインタの使い分け
  • ex04: ファイル入出力
  • ex05-06: ポインタtoメンバ関数とswitch文

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