Hussein,

The println inside (recur) will return nil.

Take care,
Moe

On Fri, Aug 21, 2015 at 4:35 PM, Hussein B. <hubaghd...@gmail.com> wrote:
> Hi,
>
> I have this structure:
>
> (def s [{"n" {"id" "a"} "d" 2 "children" [{"n" {"id" "c"} "d" 4 "children"
> []}]} {"n" {"id" "b"} "d" 3 "children" []}])
>
>
>
> And I wrote a function with zippers to traverse it:
>
>  (defn traverse [col]
>   (loop [z col]
>     (if (= (z/next z) z)
>     z
>     (if (z/branch? z)
>       (recur (z/next z))
>       (recur (-> z println z/next))))))
>
>
> But I'm getting: NullPointerException   clojure.zip/next (zip.clj:236)
>
> Any ideas?
>
> Thanks for help.
>
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