How about a cast variant that doesn't throw an exception but returns nil? user=> (cast java.lang.Boolean false) false user=> (cast java.lang.Integer false) java.lang.ClassCastException (NO_SOURCE_FILE:0) user=> (defn instance [c i] (try (cast c i) (catch Exception e))) #'user/instance user=> (instance java.lang.Boolean false) false user=> (instance java.lang.Integer false) nil
Regards, Tim. On Mar 10, 7:15 pm, Christian Vest Hansen <karmazi...@gmail.com> wrote: > On Mon, Mar 9, 2009 at 11:10 PM, Laurent PETIT <laurent.pe...@gmail.com> > wrote: > > Hello, > > > I have the use case for calling instance? where, once instance? returns > > true, I want to do something with the successful instance, such as binding > > it, or directly calling something on it. > > > For instance, I have in my code : > > > (let [console (.getConsole v)] > > (when (instance? org.eclipse.debug.ui.console.IConsole console) > > ... ...) > > > Where I would like to really use when-let : > > (when-let [console (instance? org.eclipse.debug.ui.console.IConsole > > (.getConsole v))] > > ... ...) > > > For this to work, instance? would have to return logical true instead of > > real true. > > > Do you think it could be an interesting idea to change instance? in such a > > way ? Or maybe there's already something similar in clojure-contrib I > > haven't seen ? > > What about this case: > > (when-let [x (instance? java.lang.Boolean false)] (println x)) > > I think that should print 'true', and therefor I am against this proposal. > > > > > Thanks in advance, > > > -- > > Laurent > > -- > Venlig hilsen / Kind regards, > Christian Vest Hansen. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
