The author is not saying that ordering needs to be added to the _current_ map implementation. He suggests adding an additional map implementation that has order

The author is not saying that ordering needs to be added to the _current_ map implementation. He suggests adding an additional map implementation that has ordering built in. That way, you can choose between functionality and (hypothetical) better performance The author does not seem to require iterating over a sorted list. Sorting is not the same as ordering. An ordered map is a map in which the insertion order is preserved when iterating over the elements. A sorted map outputs the elements in an order defined by a comparison function when iterating, regardless of their insertion order. You can for example sort alphabetical in case of string keys.