Function is_null

src/laybasic/laybasic/layLayerProperties.h:1346–1349

* @brief "is null" predicate * * This predicate is true if the iterator is "null". Such an iterator can be * created with the default constructor or by moving a top-level iterator up. */

   *  created with the default constructor or by moving a top-level iterator up.
   */
  bool is_null () const
  {
    return m_uint == 0;
  }

  /**
   *  @brief Increment operator