On 3/26/06, Ross Paterson <ross at soi.city.ac.uk> wrote: > > So, head . reverse is . . . O(1)? > > Certainly. The middle subtree, containing all but 2 to 8 of the elements, > is unused. Ah, of course. Let me try to ask a better question: How about (flip index i) . reverse Is that O(i)? Jim