You might want to consider switching to agents (or something else) I don't think it's possible to do what you want with refs.
Timothy Baldridge On Wed, Jul 31, 2013 at 10:08 AM, Mike Drogalis <madrush...@gmail.com>wrote: > Thanks for the link. :) I understand that the behavior I'm seeing is > correct. Any idea how to achieve the desired behavior, though? > > > On Wed, Jul 31, 2013 at 12:06 PM, Timothy Baldridge > <tbaldri...@gmail.com>wrote: > >> The answer is here: >> >> >> https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/LockingTransaction.java#L361 >> >> Agents and watches are dispatched outside of the transaction locking. >> This means that multiple transactions could be executing watches in >> parallel, and hence execute out of order. >> >> Timothy Baldridge >> >> >> On Wed, Jul 31, 2013 at 9:43 AM, Michael Drogalis >> <madrush...@gmail.com>wrote: >> >>> I can precisely exemplify the behavior here: >>> >>> https://gist.github.com/MichaelDrogalis/6123177 >>> >>> >>> On Wednesday, July 31, 2013 11:13:17 AM UTC-4, Michael Drogalis wrote: >>>> >>>> Aaron: Yep, I'm aware - and am using the value provided by the last >>>> parameter. >>>> >>>> This is going to be tough to show the problem without bringing more >>>> details of my concurrency set up. >>>> I'm not sure if this will exhibit the problem, but this is what it >>>> boils down to: >>>> >>>> https://gist.github.com/**MichaelDrogalis/6122834<https://gist.github.com/MichaelDrogalis/6122834> >>>> >>>> When enough threads are trying to write to the queue, the watches >>>> triggered later can finish before watches triggered earlier. >>>> >>>> >>>> On Wednesday, July 31, 2013 11:05:16 AM UTC-4, Aaron Cohen wrote: >>>>> >>>>> A watcher fn has 4 parameters: key, reference, old-state, new-state >>>>> >>>>> If you use old-state and new-state rather than the reference, you >>>>> should not see your problem. >>>>> >>>>> --Aaron >>>>> >>>>> >>>>> On Wed, Jul 31, 2013 at 11:00 AM, Michael Drogalis <madru...@gmail.com >>>>> > wrote: >>>>> >>>>>> Problem: >>>>>> >>>>>> I have a ref representing a queue of people in line. >>>>>> I add a watch to the ref to print out the contents of the queue >>>>>> whenever it changes. >>>>>> Naturally, and expected, the following can happen if queuing happens >>>>>> in rapid succession: >>>>>> >>>>>> Queue: [] >>>>>> <add "Mike" to queue> >>>>>> <add "John" to queue> >>>>>> >>>>>> console: "Queue is Mike, John" >>>>>> console: "Queue is Mike" >>>>>> >>>>>> I'd like to write a UI for this program, but I clearly can't reliably >>>>>> render based on the result delivered >>>>>> by the add-watch hook. What's the solution for this problem? >>>>>> >>>>>> -- >>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "Clojure" group. >>>>>> To post to this group, send email to clo...@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+u...@googlegroups.com >>>>>> For more options, visit this group at >>>>>> http://groups.google.com/**group/clojure?hl=en<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+u...@googlegroups.com. >>>>>> For more options, visit >>>>>> https://groups.google.com/**groups/opt_out<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. >>> >>> >>> >> >> >> >> -- >> “One of the main causes of the fall of the Roman Empire was that–lacking >> zero–they had no way to indicate successful termination of their C >> programs.” >> (Robert Firth) >> >> -- >> -- >> 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/0b5HWJE6Jx4/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. > > > -- “One of the main causes of the fall of the Roman Empire was that–lacking zero–they had no way to indicate successful termination of their C programs.” (Robert Firth) -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. 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