Actually, swap! doesn't seem to work in my case. I should state what I'm trying to do. I'm writing a graphics editing program where I want the user to be able to choose and save color values. I start out with a vector containing blank and white. When the user selects a new color and wants to save it I add the new color to the vector.
(def savedColors [black, white]) ..... (defn saveColor [color panel] (swap! savedColors (conj savedColors color)) <-- this does not work ..... also show the colors in the editor )) I get the following error: Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: clojure.lang.PersistentVector cannot be cast to clojure.lang.Atom I assume I'm using swap! correctly, but may not be. Bill On Mar 23, 9:57 am, Per Vognsen <per.vogn...@gmail.com> wrote: > By definition, persistent data structures are never mutable. But there > are various kinds of mutable references (vars, refs, atoms, agents) > that can _refer_ to persistent (hence unchanging) data structures. > > While David has given you an answer to your immediate query, I would > ask you to step back and consider whether you're sure you really need > references. You haven't supplied enough context for us to make that > call. > > -Per > > On Tue, Mar 23, 2010 at 8:35 PM, WoodHacker <ramsa...@comcast.net> wrote: > > I understand howconjworks. But how do you add a value to a > > persistent vector? You have to add the new item to the vector with > > (conjvector item), but how do you assign the return value to the > > persistent vector. So far I have it working with a def -- (def > > vector (conjvector item)) -- but I'm not sure this is 'pure' > > Clojure. Is there a better way, functionally, or am I there? > > Functional programming is the best way to go, but very few programs > > can exist without mutable persistent data. > > > Bill > > > -- > > 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 > > > To unsubscribe from this group, send email to > > clojure+unsubscribegooglegroups.com or reply to this email with the words > > "REMOVE ME" as the subject. -- 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 To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words "REMOVE ME" as the subject.
