On Thu, Jan 22, 2009 at 2:18 PM, Rich Hickey <richhic...@gmail.com> wrote: > > Those are important things to think about. > > There are, in fact, thread semantics for the streams mechanism, as for > the rest of Clojure. Currently, I've made it such that the stream/iter/ > seq combination ensures serialized access to the generator, allowing > use of generators over otherwise unsynchronized multi-step activities. > > Obviously, stream-backed seqs are safe, being persistent and > immutable. but it is also currently the case that the stream iter is > MT safe as well. All calls to next! on an iter are atomic re: its > generator, i.e. no 2 threads can be in the generator code at once. > That means that, within a private consumer, you could fire up multiple > threads that share the same iter and coordinate to produce a result, > and return the result or a stream upon it. > > Used correctly, this is a powerful feature. However, I'm reluctant to > expose/guarantee it, lest people start using iters as connection > points and invalidating the whole stream protection model. A well- > written API should take/return streams/seqs, never iters, so MT use of > an iter should always be an implementation detail of a single stream > step. But I can't enforce that.
Hmm... could we imagine a (synced-iter an-iter) that returned a wrapped iter that _did_ guarantee MT safety? Ofcourse this only makes sense if you end up not guaranteing MT safety of ordinary iters, and I don't know enough to prefer one approach over the other. > > For those looking to experiment with such things, feel free to try it > now and provide feedback. > > Thanks, > > Rich > > > > -- Venlig hilsen / Kind regards, Christian Vest Hansen. --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
