Sounds good. The one hitch is that I'm passing around a "visited" hash (I'm actually traversing a graph looking for spanning trees), so I end up calling (reduce XX [visited acc] (get-children node)) on the children, which (I think) kills the laziness.
On Thu, Feb 12, 2009 at 10:18 PM, Jason Wolfe <jawo...@berkeley.edu> wrote: > > > > 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 > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en -~----------~----~----~----~------~----~------~--~---
