Iterators and Const Correctness

Ensuring const-correctness when working with iterators is important to prevent unintended modifications and to express intent clearly. Here are some guidelines:

Use const iterators when you don't need to modify the underlying data:

1std::vector<int> numbers{1, 2, 3, 4, 5};
2std::vector<int>::const_iterator cit =
3  numbers.cbegin();

Use cbegin() and cend() to get const iterators:

1std::vector<int> numbers{1, 2, 3, 4, 5};
2auto cit = numbers.cbegin();
3auto cend = numbers.cend();

Use const references when passing iterators to functions that don't modify the data:

1void printValues(
2  std::vector<int>::const_iterator begin,
3  std::vector<int>::const_iterator end
4) {
5  for (auto it = begin; it != end; ++it) {
6    std::cout << *it << " ";
7  }
8}

Use const member functions when implementing container classes:

1class MyContainer {
2 public:
3  using const_iterator = MyConstIterator<T>;
4
5  const_iterator begin() const {
6    return const_iterator(&m_data[0]); }
7
8  const_iterator end() const {
9    return const_iterator(&m_data[m_size]); }
10};

Use auto and const auto& when iterating over containers in loops:

1std::vector<int> numbers{1, 2, 3, 4, 5};
2for (const auto& num : numbers) {
3  std::cout << num << " ";
4}

By following these guidelines, you can ensure that const-correctness is maintained when working with iterators, making your code more robust and self-explanatory.

Remember, const-correctness is not just about preventing modifications, but also about expressing intent and catching potential bugs at compile-time.