Perhaps this is well known to others, but on the chance that maybe it isn't I
thought I'd share.
In clojure.walk both prewalk and postwalk use recursion in ways that will blow
the stack for sufficiently deep nested structures. We had been using them
happily until recently when things got too big, and then we had problems.
For our application I was able to replace my previous walking with a call to
prewalkseq as defined below (which is only for seqs and uses zippers to avoid
the recursion -- and note that I'm using Michał Marczyk's recently patched
version of seq-zip so that it doesn't do the wrong thing with embedded
instances of ().)
(defn prewalkseq
"Like prewalk but only for seqs and uses zippers."
[f s]
(loop [z (seq-zip s)]
(if (zip/end? z)
(zip/root z)
(recur (zip/next (zip/replace z (f (zip/node z))))))))
That's all I need at the moment, but it's not immediately obvious to me how
this would be done for postwalk, and it would be nice if all of clojure.walk
could be made safe for large structures.
-Lee
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