Cpp Coding Standards

// P.10 + I.4: Immutable, strongly typed interface
struct Temperature {
    double kelvin;
};

Temperature boil(const Temperature& water);

// Weak interface: unclear ownership, unclear units
double boil(double* temp);

// Non-const global variable
int g_counter = 0;  // I.2 violation

// 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_;
};

// C.35 + C.128: Virtual destructor, use override
class Shape {
public:
    virtual ~Shape() = default;
    virtual double area() const = 0;  // C.121: pure interface
};

class Circle : public Shape {
public:
    explicit Circle(double r) : radius_(r) {}
    double area() const override { return 3.14159 * radius_ * radius_; }

private:
    double radius_;
};

// 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_;
};

// ES.20 + ES.23 + ES.25: Always initialize, prefer {}, default to const
const int max_retries{3};
const std::string name{"widget"};
const std::vector<int> primes{2, 3, 5, 7, 11};

// ES.28: Lambda for complex const initialization
const auto config = [&] {
    Config c;
    c.timeout = std::chrono::seconds{30};
    c.retries = max_retries;
    c.verbose = debug_mode;
    return c;
}();

// E.14 + E.15: Custom exception types, throw by value, catch by reference
class AppError : public std::runtime_error {
public:
    using std::runtime_error::runtime_error;
};

class NetworkError : public AppError {
public:
    NetworkError(const std::string& msg, int code)
        : AppError(msg), status_code(code) {}
    int status_code;
};

void fetch_data(const std::string& url) {
    // E.2: Throw to signal failure
    throw NetworkError("connection refused", 503);
}

void run() {
    try {
        fetch_data("https://api.example.com");
    } catch (const NetworkError& e) {
        log_error(e.what(), e.status_code);
    } catch (const AppError& e) {
        log_error(e.what());
    }
    // E.17: Don't catch everything here -- let unexpected errors propagate
}

// 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;