Hi Cameron, On Jul 7, 9:49 am, Cameron <cpuls...@gmail.com> wrote: > Hello all! Today, I've either discovered a bug, or I've discovered a > flaw in my understanding of macros. Most likely the latter :-) Could > anyone set me straight? > > While this is not the macro I was trying to write, it falls over in > the same place. > > (user=> (defmacro foo [& xs] `(map identity ~xs)) > #'user/foo > user=> (foo 1 2) > java.lang.ClassCastException: java.lang.Integer cannot be cast to > clojure.lang.IFn (NO_SOURCE_FILE:0)
Well, let's look at the macroexpansion: user> (macroexpand '(foo 1 2)) (clojure.core/map clojure.core/identity (1 2)) As you can see, this tries to call 1 with an argument of 2, which gives the exception you see. If you want your arguments evaluated, I think your solution is as good as any. If you want them unevaluated, you can do: user> (defmacro foo2 [& xs] `(map identity '~xs)) #'user/foo2 user> (foo2 1 2) (1 2) The difference: user> (foo2 1 (+ 1 1)) (1 (+ 1 1)) -Jason -- 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
