I should have been more clear when I said to use (disj ...); I meant sending that via an alter.
On Jul 5, 6:05 pm, ataggart <alex.tagg...@gmail.com> wrote: > A set might be better to hold the player-refs, then you can just call > (disj player-refs player-ref) without doing any extra checking. > > Also you can access ref values without needing to be in a dosync. > Things being immutable, the value you get from, say, @team-ref won't > change once you have it. > > On Jul 5, 5:12 pm, Mark Volkmann <r.mark.volkm...@gmail.com> wrote: > > > > > I wrote some fairly simple code to demonstrate use of StructMaps and > > Refs. It's 80 lines including comments. I'd appreciate it if someone > > could look it over and let me know if I've done anything that isn't > > very idiomatic. > > > The program models sports teams and players. The main functionality is > > the ability to trade sets of players between teams. Both teams and > > players are held by Refs. Players have a reference to their team. > > Teams have references to their players. > > > The output from the code follows: > > > Before trade: > > Oilers roster: > > Wayne Gretzky > > Mike Krushelnyski > > Marty McSorley > > Kings roster: > > Jimmy Carson > > Martin Gelinas > > > After trade: > > Oilers roster: > > Martin Gelinas > > Jimmy Carson > > Kings roster: > > Wayne Gretzky > > Mike Krushelnyski > > Marty McSorley > > > Here's the code: > > > ; A player knows his team, if any. > > (defstruct player-struct :name :team-ref) > > > ; A team knows its players. > > (defstruct team-struct :name :player-refs) > > > ; Makes a new Ref to a player-struct that isn't on any team. > > (defn make-player [name] > > (ref (struct player-struct name))) > > > ; Makes a new Ref to a team-struct that contains no players. > > (defn make-team [name] > > (ref (struct team-struct name []))) > > > (defn assign-player-to-team [player-ref new-team-ref] > > (dosync > > ; If the player has a former team, remove them from it. > > (if-let [old-team-ref (@player-ref :team-ref)] > > (let [old-player-refs (@old-team-ref :player-refs) > > new-player-refs (remove #(= % player-ref) old-player-refs)] > > (alter old-team-ref assoc :player-refs new-player-refs))) > > > ; Add the player to their new team. > > (let [old-player-refs (@new-team-ref :player-refs) > > new-player-refs (conj old-player-refs player-ref)] > > (alter player-ref assoc :team-ref new-team-ref) > > (alter new-team-ref assoc :player-refs new-player-refs)))) > > > ; Returns a string describing a given player. > > (defn player-to-string [player-ref] > > (dosync > > (str (@player-ref :name) " plays for " > > (if-let [team-ref (@player-ref :team-ref)] > > (str "the " (@team-ref :name)) > > "nobody") > > "."))) > > > ; Returns a string describing a given team. > > (defn team-to-string [team-ref] > > (dosync > > (apply str > > (@team-ref :name) " roster:" > > (map > > (fn [player-ref] (str "\n " (@player-ref :name))) > > (@team-ref :player-refs))))) > > > ; players1 and players2 are collections of Refs to player StructMaps. > > ; Neither can be empty. > > ; All players in a collection must be on the same team. > > (defn trade [players1 players2] > > (dosync > > (let [team1 ((first players1) :team-ref) > > team2 ((first players2) :team-ref)] > > (doseq [p players1] > > (assign-player-to-team p team2)) > > (doseq [p players2] > > (assign-player-to-team p team1))))) > > > (let [oilers (make-team "Oilers") > > kings (make-team "Kings") > > p1 (make-player "Wayne Gretzky") > > p2 (make-player "Mike Krushelnyski") > > p3 (make-player "Marty McSorley") > > p4 (make-player "Jimmy Carson") > > p5 (make-player "Martin Gelinas")] > > > (doseq [p [p1 p2 p3]] > > (assign-player-to-team p oilers)) > > (doseq [p [p4 p5]] > > (assign-player-to-team p kings)) > > > (println "Before trade:") > > (println (team-to-string oilers)) > > (println (team-to-string kings)) > > > (trade [p1 p2 p3] [p4 p5]) > > > (println "\nAfter trade:") > > (println (team-to-string oilers)) > > (println (team-to-string kings))) > > > -- > > 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 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 -~----------~----~----~----~------~----~------~--~---
