@Kevin, yes, I did just that to test coll-reduce, thanks for helping me out!
@Alex, thanks for the detailed response, it sure demystified this error and gave a bunch of different solutions, awesome! On Monday, March 7, 2016 at 5:17:45 PM UTC-8, Alex Miller wrote: > > Iterator, seqs, and chunking is indeed the key to this issue. The change > in question is http://dev.clojure.org/jira/browse/CLJ-1669, which made > iterator-seq's chunked. In general, this should not be problematic with > most Java iterators, however there is a iterator implementation pattern > where the identical object is returned (and mutated) on every call to > next() on the iterator. This is done in Java for performance reasons > (reuses a single mutable object rather than creating N objects). Because > iterator-seq now chunks, it will obtain 32 elements at a time, but they > will all be the identical object, so you'll see the state of the 32'nd > object for all of them. > > iterator-seq intentionally does not handle this iterator pattern (this is > in the docstring and was introduced via > http://dev.clojure.org/jira/browse/CLJ-1738). > > If you need to control iteration to one at a time (non-chunked), then > there are several options: > > 1. Use loop/recur and explicitly handle each object one at a time. Sounds > like you've got that one. > > 2. Implement your own lazy-seq that does not chunk. > > (defn iter-seq [iter f] > (if (.hasNext iter) > (lazy-seq > (cons (f (.next iter)) > (iter-seq iter f))))) > > 3. Use transducers which will also pull a single element at a time in > current transducible contexts. If you want to use it as a seq, this means > invoking > > (defn transform [^ArchiveRecord r] > (let [header (.getHeader r) > mime (.getMimetype header)] > (if (plain-text? mime) > (println "got " (.available r))))) > > (defn mapper-map [this ^Text key warc-value ^MapContext context] > (sequence (map transform) warc-value)) > > 4. In this particular case, since you're only doing side effects, > something like dorun would maybe be better. > > 5. (WARNING - may be removed!) You can still access the old iterator-seq > impementation in the Java impl for now: > > (clojure.lang.IteratorSeq/create iter) > > > -- 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/d/optout.
