What I was getting at there was that it seems like nil could mean a leaf node with the value nil or the absence of leaf nodes, and the two situations can't be distinguished. On Dec 22, 2013 12:26 PM, "Lee Spector" <lspec...@hampshire.edu> wrote:
> > On Dec 22, 2013, at 12:02 PM, Micha Niskin wrote: > > > Also, what about this: > > > > (loop [z (zip/seq-zip '((nil) 0))] > > (if (zip/end? z) > > :done > > (do (println (zip/node z)) > > (recur (zip/next z))))) > > > > Which produces: > > > > ((nil) 0) > > (nil) > > nil > > 0 > > :done > > I think that's actually fine. The nil is visited and printed as any other > element would be. Maybe you expect nil to be handled specially? I'm not > sure why, but in any event this is not the issue that I raised. > > The issue I was rasing is that, when traversing '(() 0) with zip/next, one > should first visit the root, then (), and then 0. But what actually happens > is that between then () and the 0 one lands on a non-existent nil node. So > one ends up visiting 4 nodes when there are only 3, and the extra one is a > nil. > > As I mentioned previously this leads to null pointer exceptions in my > application, and the only ways around it that I see are recoding everything > without zippers or some nasty special case hackery. > > It's also possible that I just don't understand something fundamental > about zippers and that this is supposed to happen. But if that's not true > -- if it's really a bug -- then it'd be great if this could be fixed. > > Thanks, > > -Lee > > -- > -- > 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 > Note that posts from new members are moderated - please be patient with > your first post. > 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 > --- > You received this message because you are subscribed to a topic in the > Google Groups "Clojure" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/clojure/8TL7IGmE7N0/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > -- -- 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 Note that posts from new members are moderated - please be patient with your first post. 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 --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
