Add oop and supplementary C++ teaching material

cpp_oop/Makefile

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+# Makefile for C++ OOP Tutorial
+# Demonstrates header files, source files, enum, and extern
+
+CXX = g++
+CXXFLAGS = -Wall -Wextra -std=c++14 -I./include
+TARGET = vehicle_demo
+
+# Source files
+SRCS = src/Vehicle.cpp src/Car.cpp src/Airplane.cpp src/main.cpp
+
+# Object files
+OBJS = $(SRCS:.cpp=.o)
+
+# Default target
+all: $(TARGET)
+
+# Link object files to create executable
+$(TARGET): $(OBJS)
+	$(CXX) $(CXXFLAGS) -o $(TARGET) $(OBJS)
+	@echo "Build complete! Run with: ./$(TARGET)"
+
+# Compile source files to object files
+%.o: %.cpp
+	$(CXX) $(CXXFLAGS) -c $< -o $@
+
+# Run the program
+run: $(TARGET)
+	./$(TARGET)
+
+# Clean build files
+clean:
+	rm -f $(OBJS) $(TARGET)
+	@echo "Clean complete!"
+
+# Rebuild everything
+rebuild: clean all
+
+.PHONY: all run clean rebuild

cpp_oop/README.md

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+# C++ OOP Tutorial
+
+2025 Winter Turtorial Supplementary C++, OOP的範例程式
+
+## Topics Covered
+
+### 1. OOP (Object-Oriented Programming)
+- **Encapsulation**: Private members in `Car` and `Airplane` classes
+- **Inheritance**: `Car` and `Airplane` inherit from `Vehicle`
+- **Polymorphism**: Virtual function `move()` with different implementations
+
+### 2. Header File (.h) & Source File (.cpp)
+
+#### Header File (`.h`)
+- 放 declarations（宣告）、include、extern
+- 別人看 header file 就可以知道有什麼功能
+- 統一放在資料夾`include`
+
+例如: `Vehicle.h`, `Car.h`, `Airplane.h`
+
+#### Source File (`.cpp`)
+- 實際地把 header file 中的東西 implement 出來
+- 放在資料夾`src`
+- `main.cpp`是主程式，因為只有`main()`所以我沒寫`main.h`
+
+例如: `Vehicle.cpp`, `Car.cpp`, `Airplane.cpp`
+
+
+### 3. enum (Enumeration)
+
+enum 是一個 user-defined type，代表一組有限的命名整數。
+
+
+**用途:**
+- 劃分不同的類別或狀態
+- 讓程式碼更容易閱讀和維護
+- 範例 1: Color
+- 範例 2: VehicleStatus
+- 都在`Vehicle.h`
+
+
+### 4. Global Variable & extern
+
+**重要規則:**
+- extern 只要宣告一次
+- 接下來都用 include header file 的方式
+- **初始化只要一次**（多個程式嘗試初始化會造成問題！）
+
+**本專案範例:**
+- `Vehicle.h`: 宣告 `extern int global_vehicle_count;`
+- `Vehicle.cpp`: 初始化 `int global_vehicle_count = 0;`
+- `main.cpp`: 透過 include `Car.h` (which includes `Vehicle.h`) 使用這個變數
+
+## Project Structure
+
+```
+cpp_oop/
+├── include/
+│   ├── Vehicle.h    # base class + enum + extern 宣告(declaration)
+│   ├── Car.h        # Car class declaration
+│   └── Airplane.h   # Airplane declaration
+├── src/
+│   ├── Vehicle.cpp  # Vehicle 實作(implementation) + global 變數初始化
+│   ├── Car.cpp      # Car implementation
+│   ├── Airplane.cpp # Airplane implementation
+│   └── main.cpp     # 主程式
+├── Makefile         # 編譯腳本
+└── README.md        # 本檔案
+```
+
+## How to Build and Run
+
+- 由於有多個檔案需要編譯，我叫AI寫了`Makefile`
+- `Makefile`可以包含編譯的指令，給`make`工具使用
+- 學ROS時會有`CMakeLists.txt`，功能比Makefile更多，編譯過程中會自動生成`Makefile`
+- 不需要打開`Makefile`
+- 想要自己用`g++`之類的編譯請問AI
+
+### Entering the directory in docker container
+```bash
+# 以免有人本地端無法編譯C++，這邊的指令是在container裡編譯
+# 編譯管道與ROS無關，只是單純的 make工具 與 g++ compiler
+
+### Build docker environement(Same as the homepage READE.md)
+- `cd docker`
+- docker compose up -d
+- *Container ros2_tutorial Running* # expected o/p, dont type
+- docker exec -it ros2_tutorial bash
+
+### Enter cpp_oop directory
+cd cpp_oop
+```
+
+### Using Makefile
+```bash
+# type the command in terminal
+
+# Build the project
+make
+
+# Build and run
+make run
+
+# Clean build files
+make clean
+
+# Rebuild from scratch
+make rebuild
+```
+

cpp_oop/include/Airplane.h

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+// to avoid multiple include (include guard)
+#ifndef AIRPLANE_H
+#define AIRPLANE_H
+
+#include "Vehicle.h" 
+
+// Airplane is-a Vehicle, so Airplane inherits from Vehicle just like Car
+class Airplane : public Vehicle {
+private:
+    int altitude;
+
+public:
+    // Constructor of Airplane
+    Airplane(int fuel, int max_speed, int altitude, Color color = BLUE);
+
+    // 除了inherited from Vehicle的public getter/setter function，Airplane還有自己的函式
+    void climb(int meters);
+    int getAltitude() const;
+
+    std::string move() const override; // declare with override to enable polymorphism
+};
+
+#endif

cpp_oop/include/Car.h

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+// to avoid multiple include (include guard)
+#ifndef CAR_H
+#define CAR_H
+
+#include "Vehicle.h" // to use class declaration of Vehicle
+
+
+// Car is-a Vehicle, so Car inherits from Vehicle
+class Car : public Vehicle {
+private:
+    int seat_count;    // encapsulated
+
+public:
+    // Constructor with color parameter
+    Car(int fuel, int max_speed, int seat_count, Color color = RED);
+
+    // 除了inherited from Vehicle的public getter/setter function，Car還有自己的函式
+    void drive();
+    int getSeatCount() const;
+
+    std::string move() const override; // declare with override to enable polymorphism
+};
+
+#endif

cpp_oop/include/Vehicle.h

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+// to avoid multiple include (include guard)
+#ifndef VEHICLE_H
+#define VEHICLE_H
+
+#include <string>
+
+// enum: a user-defined type that represents a finite set of named integer
+enum Color {
+    RED,      // 預設 RED==0
+    GREEN,    // GREEN==1
+    BLUE,     // BLUE==2
+    YELLOW,
+    BLACK,
+    WHITE
+};
+
+// 用來表示交通工具的狀態
+enum VehicleStatus {
+    IDLE = 0,
+    MOVING = 1,
+    REFUELING = 2,
+    MAINTENANCE = 3
+};
+
+// 在.h宣告變數extern但不初始化
+extern int global_vehicle_count;
+
+// 交通工具（抽象概念）
+class Vehicle {
+protected:
+    int fuel;          // 燃料
+    int max_speed;     // 最大速度
+    Color color;       // 顏色 (使用 enum)
+    VehicleStatus status;  // 狀態 (使用 enum)
+
+public:
+    Vehicle(int fuel, int max_speed, Color color = WHITE);
+    virtual ~Vehicle();               // destructor
+
+    void refuel(int amount);
+
+    // getter function (get the values of these variables but not directly accessing them)
+    int getFuel() const; // const -> this function should not modify the variable in the class
+    int getMaxSpeed() const;
+    Color getColor() const;
+    VehicleStatus getStatus() const;
+
+    // setter function (set the values of specified varaible)
+    void setStatus(VehicleStatus new_status);
+
+    // demo how to use enum for if-statement
+    std::string getColorName() const;
+
+    // Polymorphism interface, declared virtual
+    // this is pure virtual function(so the child of Vehicle must declare own move function)
+    // pure virtual function does not need function definition here
+    virtual std::string move() const = 0;
+};
+
+#endif

cpp_oop/src/Airplane.cpp

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+#include "Airplane.h"
+
+Airplane::Airplane(int fuel, int max_speed, int altitude, Color color)
+    : Vehicle(fuel, max_speed, color), altitude(altitude) {}
+
+void Airplane::climb(int meters) {
+    if (fuel > 0) {
+        status = MOVING;  // 使用 enum 設定狀態
+        altitude += meters;
+        fuel--;
+    }
+    else {
+        status = IDLE;
+    }
+}
+
+int Airplane::getAltitude() const {
+    return altitude;
+}
+
+std::string Airplane::move() const {
+    return "Airplane flies in the sky";
+}

cpp_oop/src/Car.cpp

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+#include "Car.h"
+// no need to include Vehicle.h, since Car.h has included Vehicle.h
+
+Car::Car(int fuel, int max_speed, int seat_count, Color color)
+    : Vehicle(fuel, max_speed, color), seat_count(seat_count) {}
+    // Car's constructor must call the constructor of the parent(Vehicle)
+
+void Car::drive() {
+    if (fuel > 0) {
+        status = MOVING;  // 使用 enum 設定狀態
+        fuel--;           // protected member
+    }
+    else {
+        status = IDLE;
+    }
+}
+
+int Car::getSeatCount() const {
+    return seat_count;
+}
+
+std::string Car::move() const {
+    return "Car drives on the road";
+}

cpp_oop/src/Vehicle.cpp

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+#include "Vehicle.h"
+// Vehicle.cpp hava the function definition
+// and variable initialization
+// corresponding to Vehicle.h
+
+// 初始化extern過的variable
+int global_vehicle_count = 0;
+
+Vehicle::Vehicle(int fuel, int max_speed, Color color)
+    : fuel(fuel), max_speed(max_speed), color(color), status(IDLE) {
+    global_vehicle_count++;  // 每創建一個交通工具，總數+1
+}
+
+Vehicle::~Vehicle() {
+    global_vehicle_count--;  // 交通工具被刪除時，總數-1
+}
+
+void Vehicle::refuel(int amount) {
+    status = REFUELING;
+    fuel += amount;
+    status = IDLE;
+}
+
+int Vehicle::getFuel() const {
+    return fuel;
+}
+
+int Vehicle::getMaxSpeed() const {
+    return max_speed;
+}
+
+Color Vehicle::getColor() const {
+    return color;
+}
+
+VehicleStatus Vehicle::getStatus() const {
+    return status;
+}
+
+void Vehicle::setStatus(VehicleStatus new_status) {
+    status = new_status;
+}
+
+// ===== 使用 enum 來判斷 =====
+std::string Vehicle::getColorName() const {
+    if (color == Color::RED) {
+        return "Red";
+    }
+    else if (color == Color::GREEN) {
+        return "Green";
+    }
+    else if (color == Color::BLUE) {
+        return "Blue";
+    }
+    else if (color == Color::YELLOW) {
+        return "Yellow";
+    }
+    else if (color == Color::BLACK) {
+        return "Black";
+    }
+    else if (color == Color::WHITE) {
+        return "White";
+    }
+    return "Unknown";
+}