You have an extra set of parens around a, treating it as a function call. Try:
(defn if-a [a b] (if a (str a) (str b))) Hope that helps, Dave On Tue, Aug 23, 2011 at 4:37 PM, Andrew Xue <and...@lumoslabs.com> wrote: > this doesn't work: > > user=> (defn if-a [a b] (if (a) (str a) (str b))) > #'user/if-a > user=> (if-a nil "b") > java.lang.NullPointerException (NO_SOURCE_FILE:0) > user=> (if-a "a" nil) > user=> java.lang.ClassCastException: java.lang.String cannot be cast > to clojure.lang.IFn (NO_SOURCE_FILE:0) > > this does work: > > user=> (defn if-a [a b] (if (identity a) (str a) (str b))) > #'user/if-a > user=> (if-a nil "b") > "b" > user=> (if-a "a" nil) > "a" > > > why is the identity function is needed? thanks > > -- > 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 -- 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
