2010/8/5 Meikel Brandmeyer <m...@kotka.de> > Hi, > > On Aug 5, 2:14 pm, Laurent PETIT <laurent.pe...@gmail.com> wrote: > > > (ns delay.util) > > > > (defprotocol Cancellable (isCancelled [this]) (cancel [this])) > > > > (defn timed-delay [pause fun] > > (let [d (delay (fun)) > > f (future (Thread/sleep pause) @d)] > > (reify > > clojure.lang.IDeref > > (deref [_] @d) > > delay.util.Cancellable > > (isCancelled [_] (future-cancelled? f)) > > (cancel [_] (future-cancel f))))) > > > > What about this ? > > This looks ok, I think. At least better than "hijacking" the future. > > However, I'm still the opinion, that you mix up concerns here. > "Cancellable" somehow implies that it stops whatever the thing is > doing. But it has no influence on the deref. To me this would be > surprising. > > For me the whole future thing is a side-effect which is not relevant > to the consumer of the parsed code. It is a convenience which can be > tracked separately from the actual delay. >
Yes, maybe I'm putting too much ... will need to think about it again But I don't understand your usage of the expression "side-effect". e.g. the instance given will play well in any situation. Even if you call cancel on it, this will not prevent following calls to deref to succeed. So holders of a reference to it can use it without knowing at all that the instance also implements the Cancellable interface. Maybe it's the names that must be adjusted. After all I was wrong, it's not a delayed delay I've written. How to rename things ? timed-delay -> ? delay.util.Cancellable -> ? isCancelled -> ? cancel -> ? -- 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
