Thanks for looking this over! It's interesting how often I find myself trying to use an Atom because I'm not coordinating changes multiple things, just one, but the solution still requires using a Ref. I guess it's wrong to think of what I'm doing as coordinating one value. I'm really coordinating two, a map and a thing inside the map (the last value added).
On Sun, Mar 22, 2009 at 6:29 AM, Meikel Brandmeyer <m...@kotka.de> wrote: > Hi, > > Am 21.03.2009 um 23:26 schrieb Mark Volkmann: > >> I'm looking for a suggestion on how I can get new-struct. > > The other aspects aside, here an answer for this question. > > (defn get-new-struct > [the-new-map] > (the-new-map (last (keys the-new-map)))) > > Or, to be sure, > > (defn get-new-struct > [the-new-map] > (the-new-map (apply max (keys the-new-map)))) > > This is of course ugly and O(n) as the last indicates. > > You could however change your b to take the atom > instead of the map. > > (defn b > [the-atom your-data] > (let [new-id (get-new-id @the-atom) > new-struct (make-new-struct new-id your-data)] > (swap! the-atom assoc new-id new-struct) > new-struct)) > > But now the deref and the swap! are not coordinated > anymore. So one needs a Ref or an architecture, where > all other users are only readers of the atom and one > thread does sequentially add the new structs. Then > the value of the atom wouldn't change between the > deref and swap!. This maybe suggests an agent instead > of an atom, but then you cannot return the new struct. > And we would be back with the O(n) thing. > > So I agree with Laurent that you want a Ref here. > > Sincerely > Meikel -- R. Mark Volkmann Object Computing, Inc. --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
