Ah that was what I was missing. You are right, I misunderstood the recur form.
For some reason I thought in recur you have to specify the name of the variable that it's bound to. so when I wrote (recur (newlist (cons (first x) newlist)) I thought I was saying in recur, rebind (cons (first x) newlist) to newlist. Thanks for the info! On Mon, Nov 9, 2009 at 2:47 PM, Meikel Brandmeyer <m...@kotka.de> wrote: > Hi, > > Am 09.11.2009 um 20:08 schrieb Wilson MacGyver: > >> (defn group [x] >> (loop [newlist [] currlist x] >> (if (not (empty? x)) >> (recur (newlist (cons (first x) newlist)) >> (currlist (drop-while #(= (first currlist) %) currlist)) >> )))) >> >> >> It seems logical to me, but when I tried it with >> (group [1 1 2 2 3 3 ]) >> >> I get >> CompilerException java.lang.IllegalArgumentException: Key must be >> integer >> >> what am I missing? > > I think there is a misunderstanding how recur works. What you actually > do, is to call newlist (a vector, acting as a function in this case). > This is possible to retrieve the value at that index. ([1 2 3] 2) => > 3. However you pass a Cons. Hence the exception. > > A non-lazy implementation with loop/recur is surprisingly ugly. You > need two different loops: one to traverse the input list, one to count > the number of occurrences of an item. > > Sincerely > Meikel > > -- Omnem crede diem tibi diluxisse supremum. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
