Meikel Brandmeyer <[email protected]> writes:
> Hi,
>
> On Aug 21, 12:05 pm, Jan Rychter <[email protected]> wrote:
>
>> It isn't what I want. But that's because I misspecified what I actually
>> wanted. I didn't think about the problem enough. I need something more
>> akin to a splice function:
>>
>> (splice tree1 index tree2)
>>
>> (splice '(1 2 (3 4 5) 6) 4 '(7 8 (9 10)))
>> should produce => '(1 2 (3 7 8 (9 10) 6))
>
> (defn zip-splice
> [loc node new-node]
> (loop [loc loc]
> (cond
> (zip/end? loc)
> (throw (Exception. "Node not found"))
>
> (= (zip/node loc) node)
> (let [childs (zip/children new-node)
> loc (reduce #(zip/insert-left %1 %2) loc
> childs)]
> (zip/remove loc))
>
> :else (recur (zip/next loc)))))
>
> user=> (def z (zip/vector-zip [1 2 [3 4 5] 6]))
> #'user/z
> user=> (def s (zip/vector-zip [7 8 [9 10]]))
> #'user/s
> user=> (zip/root (zip-splice z 4 s))
> [1 2 [3 7 8 [9 10] 5] 6]
>
> Be aware of the '=' there. This you might want to replace with some
> smarter function to check for the identity of a node. I stumpled over
> that in this thread:
> http://groups.google.com/group/clojure/browse_thread/thread/bfd6539ec367a95b
> I'm not really a tree expert. So if you have solved this problem,
> please let me know. I'm still interested in this.
Thanks -- this is good stuff. I appreciate the help.
I meant the "index" as a numeric index into the tree (depth-first
traversal), unrelated to the actual tree contents -- I used natural
numbers in the tree only as an example. My real trees contain mostly
symbols. So your function isn't applicable to my stuff.
In the meantime, I came up with this (nothing like a piece of paper and
some thinking to work things out):
(defn zip-splice [zipped-tree index loc2]
(let [splice-site (goto-node zipped-tree index)]
(zip/root
(zip/replace (zip/up splice-site)
(concat (zip/lefts splice-site)
(list (zip/node loc2))
(zip/rights loc2))))))
where goto-node is defined as:
(defn goto-node [zipped-code n]
(loop [counter 0
loc (zip/next zipped-code)]
(if (or (= counter n) (zip/end? loc))
loc
(recur (inc counter) (zip/next loc)))))
This seems to do exactly what I wanted.
--J.
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