You are right, but why is this a problem? The zipper works as intended
and if you need to detect leaf nodes, that kan be done by checking for
the presence of a non-empty value of the children key.
On Wed, Nov 27, 2013 at 2:18 PM, dabd <dario.reh...@gmail.com> wrote:
> Your map-tree is exactly like an xml-zip.
> The problem I find with it is that now branch? also returns true for leaf
> nodes:
>
> (def m (map-tree {:v 1 :cs [{:v 2} {:v 3 :cs [{:v 4} {:v 5}]}]}))
>
>> (-> m z/down)
> [{:v 2} {:l [], :pnodes [{:v 1, :cs [{:v 2} {:v 3, :cs [{:v 4} {:v 5}]}]}],
> :ppath nil, :r ({:v 3, :cs [{:v 4} {:v 5}]})}]
>
>> (-> m z/down z/branch?)
> true
>
> (def t (tree-zip [1 2 [3 4 5]]))
>
>> (-> t z/down z/branch?)
> false
>
> On Wednesday, November 27, 2013 9:26:53 AM UTC, martin_clausen wrote:
>>
>> 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....@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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