Iterators

Iterators and Const Correctness

How do I ensure const-correctness when working with iterators?

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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:

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

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

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

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

void printValues(
  std::vector<int>::const_iterator begin,
  std::vector<int>::const_iterator end
) {
  for (auto it = begin; it != end; ++it) {
    std::cout << *it << " ";
  }
}

Use const member functions when implementing container classes:

class MyContainer {
 public:
  using const_iterator = MyConstIterator<T>;

  const_iterator begin() const {
    return const_iterator(&m_data[0]); }

  const_iterator end() const {
    return const_iterator(&m_data[m_size]); }
};

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

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

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.

Answers to questions are automatically generated and may not have been reviewed.

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