]> I prefer this: (* Why in the world aren't these included in the standard library? *) let string_foldr f init s = let rec aux i x = if i < 0 then x else aux (i-1) (f (String.get s i) x) in aux (String.length s - 1) init let explode = string_foldr (fun c acc -> c :: acc) [] (* End "Why in the world?" comment *) let digitToInt c = match c with | '0' -> 0 | '1' -> 1 | '2' -> 2 | '3' -> 3 | '4' -> 4 | '5' -> 5 | '6' -> 6 | '7' -> 7 | '8' -> 8 | '9' -> 9 | _ -> failwith "invalid digit" let f l = List.map digitToInt (List.flatten (List.map explode l)) (* Or, to be more efficient, without constructing the intermediate lists via explode. *) let f' l = List.fold_right (fun s l1 -> string_foldr (fun c l2 -> digitToInt c :: l2) l1 s) l [] (* Out of curiosity, why does fold_right take the initial value after the list it operates on? *) I don't think users would be as tempted to write imperative, possibly inefficient code working with strings if the String module included better iterators such a fold_right and fold_left (and maybe even map, since strings are mutable in O'Caml and it could thus be done efficiently). Jeremy _________________________________________________________________ Protect your PC - get McAfee.com VirusScan Online http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963 ------------------- To unsubscribe, mail caml-list-request@inria.fr Archives: http://caml.inria.fr Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ: http://caml.inria.fr/FAQ/ Beginner's list: http://groups.yahoo.com/group/ocaml_beginners