Hello, I've implemented Chris Okasaki's random-access list[1] which provides typical list operations (cons, head, tail) in O(1) and yet offers indexed random-access in O(log n). It's uploaded on hackage[2]. It's still an early version which I'll extend, but especially at this eary stage I'd appreciate your feedback concerning what's still missing / to be fixed / to be improved. Regards, Stephan [1] Chris Okasaki: "Purely Functional Data Structures" [2] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/random-access-lis... -- Früher hieß es ja: Ich denke, also bin ich. Heute weiß man: Es geht auch so. - Dieter Nuhr