C++ Coding Standards

// F.16: Cheap types by value, others by const&
void print(int x);                           // cheap: by value
void analyze(const std::string& data);       // expensive: by const&
void transform(std::string s);               // sink: by value (will move)

// F.20 + F.21: Return values, not output parameters
struct ParseResult {
    std::string token;
    int position;
};

ParseResult parse(std::string_view input);   // GOOD: return struct

// BAD: output parameters
void parse(std::string_view input,
           std::string& token, int& pos);    // avoid this

// F.4 + F.8: Pure, constexpr where possible
constexpr int factorial(int n) noexcept {
    return (n <= 1) ? 1 : n * factorial(n - 1);
}

static_assert(factorial(5) == 120);

// C.20: Let the compiler generate special members
struct Employee {
    std::string name;
    std::string department;
    int id;
    // No destructor, copy/move constructors, or assignment operators needed
};

// C.21: If you must manage a resource, define all five
class Buffer {
public:
    explicit Buffer(std::size_t size)
        : data_(std::make_unique<char[]>(size)), size_(size) {}

    ~Buffer() = default;

    Buffer(const Buffer& other)
        : data_(std::make_unique<char[]>(other.size_)), size_(other.size_) {
        std::copy_n(other.data_.get(), size_, data_.get());
    }

    Buffer& operator=(const Buffer& other) {
        if (this != &other) {
            auto new_data = std::make_unique<char[]>(other.size_);
            std::copy_n(other.data_.get(), other.size_, new_data.get());
            data_ = std::move(new_data);
            size_ = other.size_;
        }
        return *this;
    }

    Buffer(Buffer&&) noexcept = default;
    Buffer& operator=(Buffer&&) noexcept = default;

private:
    std::unique_ptr<char[]> data_;
    std::size_t size_;
};

// R.11 + R.20 + R.21: RAII with smart pointers
auto widget = std::make_unique<Widget>("config");  // unique ownership
auto cache  = std::make_shared<Cache>(1024);        // shared ownership

// R.3: Raw pointer = non-owning observer
void render(const Widget* w) {  // does NOT own w
    if (w) w->draw();
}

render(widget.get());

// R.1: Resource acquisition is initialization
class FileHandle {
public:
    explicit FileHandle(const std::string& path)
        : handle_(std::fopen(path.c_str(), "r")) {
        if (!handle_) throw std::runtime_error("Failed to open: " + path);
    }

    ~FileHandle() {
        if (handle_) std::fclose(handle_);
    }

    FileHandle(const FileHandle&) = delete;
    FileHandle& operator=(const FileHandle&) = delete;
    FileHandle(FileHandle&& other) noexcept
        : handle_(std::exchange(other.handle_, nullptr)) {}
    FileHandle& operator=(FileHandle&& other) noexcept {
        if (this != &other) {
            if (handle_) std::fclose(handle_);
            handle_ = std::exchange(other.handle_, nullptr);
        }
        return *this;
    }

private:
    std::FILE* handle_;
};

// Con.1 through Con.5: Immutability by default
class Sensor {
public:
    explicit Sensor(std::string id) : id_(std::move(id)) {}

    // Con.2: const member functions by default
    const std::string& id() const { return id_; }
    double last_reading() const { return reading_; }

    // Only non-const when mutation is required
    void record(double value) { reading_ = value; }

private:
    const std::string id_;  // Con.4: never changes after construction
    double reading_{0.0};
};

// Con.3: Pass by const reference
void display(const Sensor& s) {
    std::cout << s.id() << ": " << s.last_reading() << '\n';
}

// Con.5: Compile-time constants
constexpr double PI = 3.14159265358979;
constexpr int MAX_SENSORS = 256;

// Enum.3 + Enum.5: Scoped enum, no ALL_CAPS
enum class Color { red, green, blue };
enum class LogLevel { debug, info, warning, error };

// BAD: plain enum leaks names, ALL_CAPS clashes with macros
enum { RED, GREEN, BLUE };           // Violation
#define MAX_SIZE 100                  // Use constexpr instead