Nice research - so is it then the reader that doesn't allow us to escape the "[B" such that we can write it such that it can be interpreted as a symbol [B ?
-Frank. On Mar 24, 2010, at 7:27 PM, ataggart wrote: > Ok, after looking into how clojure resolves class literal symbols, it > turns out it is already smart enough to recognize symbol names that > start with "["; the problem is it's a pain to type such symbols into > code. > > Your code can work this way: > user=> (defmethod mm (resolve (symbol "[B")) [b] (println "bytes")) > #<MultiFn clojure.lang.mult...@6ee3849c> > user=> (mm (.getBytes "a")) > bytes > nil > > In the end though, it turns out to be just another way to call (Class/ > forName "[B"). > > > On Mar 24, 6:54 pm, ataggart <alex.tagg...@gmail.com> wrote: >> The java version would look like: >> Class c = byte[].class; >> >> But since the clojure way to obtain a class is simply to use its name >> literal, e.g.: >> user=> (type String) >> java.lang.Class >> the only way to get the class of an array would involve either a >> function call or a change to the reader. And java doesn't make it >> easy since all array-class stuff, such as Class.isArray(), is native >> code. The best I've come up with is: >> user=> >> (defn #^Class array-class >> "Returns the Class of an array of component type c" >> [#^Class c] >> (when c (class (java.lang.reflect.Array/newInstance c 0)))) >> user=> (array-class String) >> [Ljava.lang.String; >> which appears faster than using Class/forName with a created string. >> But since one *can* type a literal byte array class in java, I'd >> imagine there's some way to implement this with bytecode magic, rather >> than going through java.lang.reflect.Array. >> >> On Mar 24, 3:39 pm, Frank Siebenlist <frank.siebenl...@gmail.com> >> wrote: >> >> >> >>> Right - not very different from the (class (byte-array 1)) that I came up >>> with in the mean time... all not very clojuresque. >> >>> -FS. >> >>> On Mar 24, 2010, at 3:03 PM, ataggart wrote: >> >>>> For type-hinting #^"[B" works, but for obtaining and passing the class >>>> to defmethod, the best I can come up with is (Class/forName "[B"). >> >>>> On Mar 24, 11:02 am, Frank Siebenlist <frank.siebenl...@gmail.com> >>>> wrote: >>>>> The following repl session shows my attempt to dispatch a multimethod on >>>>> "type": >> >>>>> ... >>>>> user> (defmulti mm type) >>>>> #'user/mm >>>>> user> (type "a") >>>>> java.lang.String >>>>> user> (defmethod mm java.lang.String [s] (println "string")) >>>>> #<MultiFn clojure.lang.mult...@41e3a0ec> >>>>> user> (mm "a") >>>>> string >>>>> nil >>>>> user> (type (.getBytes "a")) >>>>> [B >>>>> user> (defmethod mm [B [b] (println "bytes")) >>>>> ; Evaluation aborted. >>>>> user> (def ba-type (type (.getBytes "a"))) >>>>> #'user/ba-type >>>>> user> (defmethod mm ba-type [b] (println "bytes")) >>>>> #<MultiFn clojure.lang.mult...@41e3a0ec> >>>>> user> (mm (.getBytes "a")) >>>>> bytes >>>>> nil >>>>> user> >>>>> ... >> >>>>> It works easily for the string, but for a native java byte array, type >>>>> (or class) gives me back this "[B", which I'm unable to use as a dispatch >>>>> value for the defmethod. >>>>> I can, however, assign the value to a reference and us that to dispatch >>>>> on successfully - but that feels like a hack. >> >>>>> Is there a way to express the byte array type in a different way than >>>>> "[B" that would work? >> >>>>> Thanks, Frank. >> >>>> -- >>>> 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. -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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