On Feb 12, 4:01 pm, Jeffrey Straszheim <straszheimjeff...@gmail.com>
wrote:
> It is easy to do a lazy preorder walk of a tree (in psuedo-clojure):
>
> (fn visit [node]
> (lazy-cons node (map visit (get-children node))))
>
> So, that much is obvious. However, I cannot think of an obvious way to do a
> post-order traversal lazily. I sort of assume it cannot be done, as the
> whole point -- more or less -- of a post ordered walk is you've visited the
> children already.
I think
(defn visit [node]
(lazy-cat (map visit (get-children node)) [node]))
should do more or less what you want. It won't be quite as lazy as
the preorder, since it has to walk all the way to a leaf before it can
start producing values, but I think it will evaluate just what's
needed to produce each value (perhaps plus a little bit).
-Jason
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