On Tue, Mar 10, 2009 at 9:40 AM, Timothy Pratley <timothyprat...@gmail.com> wrote: > > 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
That's a better idea. You might want to consider calling it 'coerce' instead of 'instance' - I think that name is clearer and fits the intent better. > > > 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. > > > -- 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 -~----------~----~----~----~------~----~------~--~---
