-With this encoding scheme, each list would be represented by a somewhat more complex function than before. On the other hand, it would now become as easy to query the list's tail as it is to query its head.
+With this encoding scheme, each list would be represented by a somewhat more complex function than before. On the other hand, it would now become as easy to query the list's tail as it is to query its head. Before the refinement, querying the tail of a list required us to *build up* the tail afresh each time we wanted to extract it. Whereas this refinement *saves a copy* of the tail *for direct access*, as a new middle argument to the fold function, when the list is first constructed.