Class const_iterator

lib/swoc/include/swoc/IPRange.h:1222–1310

   * and @a p dangling references. If the return is by value the compiler takes care of it.
   */
  class const_iterator {
    using self_type = const_iterator; ///< Self reference type.
    friend class IPSpace;

  public:
    using value_type = detail::ip_space_const_value_type<PAYLOAD>; /// Import for API compliance.
    // STL algorithm compliance.
    using iterator_category = std::bidirectional_iterator_tag;
    using pointer           = value_type const *;
    using reference         = value_type const &;
    using difference_type   = int;

    /// Default constructor.
    const_iterator() = default;

    /// Copy constructor.
    const_iterator(self_type const &that) = default;

    /// Assignment.
    self_type &operator=(self_type const &that);

    /// Pre-increment.
    /// Move to the next element in the list.
    /// @return The iterator.
    self_type &operator++();

    /// Pre-decrement.
    /// Move to the previous element in the list.
    /// @return The iterator.
    self_type &operator--();

    /// Post-increment.
    /// Move to the next element in the list.
    /// @return The iterator value before the increment.
    self_type operator++(int);

    /// Post-decrement.
    /// Move to the previous element in the list.
    /// @return The iterator value before the decrement.
    self_type operator--(int);

    /// Dereference.
    /// @return A reference to the referent.
    reference operator*() const;

    /// Dereference.
    /// @return A pointer to the referent.
    pointer operator->() const;

    /// Equality
    bool operator==(self_type const &that) const;

    /// Inequality
    bool operator!=(self_type const &that) const;

  protected:
    // These are stored non-const to make implementing @c iterator easier. The containing class provides the
    // required @c const protection. Internally a tuple of iterators is stored for forward iteration. If