Ah, sorry. You could use a map-tree instead. It is a bit more verbose,
but I believe it does what you want.
(defn map-tree [root]
(z/zipper
map?
#(seq (:cs %))
(fn [node children]
(assoc node :cs (and children (apply vector children))))
root))
(let [mt (map-tree {:v 1 :cs [{:v 2} {:v 3 :cs [{:v 4} {:v 5}]}]})]
(loop [loc mt]
(if (z/end? loc)
(z/root loc)
(recur (z/next (let [n (:v (z/node loc))]
(if (and (integer? n) (odd? n))
(z/replace loc {:v(* 2 (:v (z/node loc))) :cs
(z/children loc)})
loc)))))))
On Wed, Nov 27, 2013 at 8:35 AM, dabd <dario.reh...@gmail.com> wrote:
> The problem is that your vector-zip is not representing the tree I pictured.
>
>
> On Wednesday, November 27, 2013 6:26:12 AM UTC, martin_clausen wrote:
>>
>> Yes, for instance like this:
>>
>> (let [vz (z/vector-zip [1 [2] [3 [4 5]]])]
>> (loop [loc vz]
>> (if (z/end? loc)
>> (z/root loc)
>> (recur (z/next (if (and (integer? (z/node loc)) (odd? (z/node
>> loc)))
>> (z/replace loc (* 2 (z/node loc)))
>> loc))))))
>>
>> Which lets you avoid writing half the infrastructure yourself.
>>
>> On Wed, Nov 27, 2013 at 6:19 AM, dabd <dario....@gmail.com> wrote:
>> > I'm not sure what you mean by not being able to provide a meaningful
>> > branch?.
>> >
>> > I would like to represent a tree such a this:
>> >
>> > 1
>> >
>> > / \
>> > 2 3
>> > / \
>> > 4 5
>> >
>> >
>> > How can I achieve this using zippers?
>> >
>> > On Wednesday, November 27, 2013 4:30:15 AM UTC, martin_clausen wrote:
>> >>
>> >> To use the zipper library you have to be able to provide branch?
>> >> children
>> >> and make-node functions that apply to your data structure.
>> >>
>> >> I don't see a way to provide a meaningful branch? or children function
>> >> for
>> >> the structure you describe. Vector? will not work as branch? as it will
>> >> not
>> >> return true if passed the first element in a vector, and next will not
>> >> work
>> >> as it will not return the children if passed the first element of a
>> >> vector.
>> >>
>> >> It looks to me like you don't get past the first element because the
>> >> call
>> >> to z/next fails both (and (branch? loc) (down loc)), (right loc) and
>> >> (up
>> >> loc) and therefore marks the first element as the end of the of the
>> >> structure.
>> >>
>> >> Is there a compelling reason for not using the vector-zip structure for
>> >> your specific use-case?
>> >>
>> >>
>> >> On Wednesday, November 27, 2013 2:59:40 AM UTC+1, dabd wrote:
>> >>>
>> >>> The built-in vector-zip will build a tree with a different structure
>> >>> than
>> >>> what I need.
>> >>> I want build a tree as described in the first post: the node value is
>> >>> the
>> >>> first element of the vector and the children the rest of the elements.
>> >>>
>> >>>
>> >>> zipper.core> (loop [loc (tree-zipper [1 2 [3 4 5]])]
>> >>> (if (z/end? loc)
>> >>> (z/root loc)
>> >>> (do (println (z/node loc))
>> >>> (recur (z/next loc)))))
>> >>> [1 2 [3 4 5]]
>> >>>
>> >>> 2
>> >>>
>> >>> [3 4 5]
>> >>>
>> >>> 4
>> >>>
>> >>> 5
>> >>>
>> >>> [1 2 [3 4 5]]
>> >>> zipper.core> (loop [loc (z/vector-zip [1 2 [3 4 5]])]
>> >>> (if (z/end? loc)
>> >>> (z/root loc)
>> >>> (do (println (z/node loc))
>> >>> (recur (z/next loc)))))
>> >>> [1 2 [3 4 5]]
>> >>>
>> >>> 1
>> >>>
>> >>> 2
>> >>>
>> >>> [3 4 5]
>> >>>
>> >>> 3
>> >>>
>> >>> 4
>> >>>
>> >>> 5
>> >>>
>> >>> [1 2 [3 4 5]]
>> >>>
>> >>>
>> >>> On Tuesday, November 26, 2013 11:56:45 PM UTC, martin_clausen wrote:
>> >>>>
>> >>>> With a nested vector tree you can use the built in vector-zip
>> >>>> function
>> >>>> to create your zipper.
>> >>>>
>> >>>> As to the editing, the source code contains a very similar use-case,
>> >>>> which can be adapted to something like the following:
>> >>>>
>> >>>> (let [vz (vector-zip [1 2 [3 4 5]])]
>> >>>> (loop [loc vz]
>> >>>> (if (end? loc)
>> >>>> (root loc)
>> >>>> (recur (next (if (and (integer? (node loc)) (odd? (node
>> >>>> loc)))
>> >>>> (replace loc (* 2 (node loc)))
>> >>>> loc))))))
>> >>>>
>> >>>> > [2 2 [6 4 10]]
>> >>>>
>> >>>> On Tuesday, November 26, 2013 10:50:34 PM UTC+1, dabd wrote:
>> >>>>>
>> >>>>> I am trying to work with a tree representation using vectors where
>> >>>>> the
>> >>>>> first element is the node value and the rest are the children as
>> >>>>> suggested
>> >>>>> here:
>> >>>>>
>> >>>>>
>> >>>>> http://grokbase.com/t/gg/clojure/12afy2cz9p/how-to-represent-trees-for-use-with-zippers
>> >>>>>
>> >>>>> However I am having trouble using clojure.zip/edit to change a
>> >>>>> simple
>> >>>>> tree. I'd like to multiply the odd numbers by 2 in this case.
>> >>>>> https://gist.github.com/dabd/7666778
>> >>>>>
>> >>>>> It looks like after editing the first (branch) node clojure.zip/next
>> >>>>> will get to the end of the tree.
>> >>>>> How can I correct this code?
>> >>>>>
>> >>>>> Thanks.
>> >>>>>
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