http://dev.clojure.org/jira This file is an XML representation of an issue en-us 4.4 649 25-07-2011 http://dev.clojure.org/jira/browse/CLJ-1059 Clojure <p>PersistentQueue implements Sequential but doesn't implement java.util.List. Lists form an equality partition, as do Sequentials. This means that you can end up with nontransitive equality:</p> <p>(def q (conj clojure.lang.PersistentQueue/EMPTY 1 2 3))<br/> ;=&gt; #user/q<br/> (def al (doto (java.util.ArrayList.) (.add 1) (.add 2) (.add 3)))<br/> ;=&gt; #user/al<br/> (def v <span class="error">&#91;1 2 3&#93;</span>)<br/> ;=&gt; #user/v<br/> (= al v)<br/> ;=&gt; true<br/> (= v q)<br/> ;=&gt; true<br/> (not= al q)<br/> ;=&gt; true</p> <p>This happens because PersistentQueue is a Sequential but not a List, ArrayList is a List but not a Sequential, and PersistentVector is both.</p> CLJ-1059

PersistentQueue doesn't implement java.util.List, causing nontransitive equality

Defect Major Open Unresolved Philip Potter Philip Potter Mon, 3 Sep 2012 04:23:59 -0500 Tue, 11 Dec 2012 13:58:01 -0600 Release 1.4 0 2 <p>Whoops, according to <a href="http://dev.clojure.org/display/design/JIRA+workflow">http://dev.clojure.org/display/design/JIRA+workflow</a> I should have emailed clojure-dev before filing this ticket. Here is the discussion:</p> <p><a href="https://groups.google.com/d/topic/clojure-dev/ME3-Ke-RbNk/discussion">https://groups.google.com/d/topic/clojure-dev/ME3-Ke-RbNk/discussion</a></p> <p>Attached 001-make-PersistentQueue-implement-List.diff, 15/Sep/12</p> <p>Note that this patch has a minor conflict with the one I added to <a href="http://dev.clojure.org/jira/browse/CLJ-1070" title="PersistentQueue&#39;s hash function does not match its equality"><del>CLJ-1070</del></a>, because both add an extra interface to PersistentQueue - List in this case, IHashEq in <a href="http://dev.clojure.org/jira/browse/CLJ-1070" title="PersistentQueue&#39;s hash function does not match its equality"><del>CLJ-1070</del></a>.</p> <p>Philip, patch looks pretty good &#8211; thanks for doing this. A couple notes:</p> <p>This is only my opinion, but I prefer imports be listed without wildcards, even if it means an extra couple lines at the top of a .java file.</p> <p>I noticed the "List stuff" code is a copy of what's in ASeq and EmptyList. I suppose this is copied because EmptyList and PersistentQueue extend Obj and therefore can't extend ASeq. Is this the only reason? It seems a shame to duplicate these method definitions, but I don't know of a better solution, do you?</p> <p>It would also be nice if the test check a couple of the List methods you've implemented.</p> <p>oh, also "git am" refused to apply the patch, but I'm not sure why. "patch -p 1" worked perfectly.</p> <p>did you use the --keep-cr option to git am?</p> <p>I struggled to know whether I should be adding CRs or not to line endings, because the files I was editing weren't consistent in their usage. If you open them in emacs, half the lines have ^M at the end.</p> <p>Will submit another patch, with the import changed. I'll have a think about the list implementation and see what ideas I can come up with.</p> <p>Attached 002-make-PersistentQueue-implement-Asequential.diff</p> <p>This patch is an alternative to 001-make-PersistentQueue-implement-List.diff</p> <p>So I took on board what you said about ASeq, but it didn't feel right making PersistentQueue directly implement ISeq, somehow.</p> <p>So I split ASeq into two parts &#8211; ASequential, which implements j.u.{Collection,List} and manages List-equality and hashcodes; and ASeq, which... doesn't seem to be doing much anymore, to be honest.</p> <p>As a bonus, this patch fixes <a href="http://dev.clojure.org/jira/browse/CLJ-1070" title="PersistentQueue&#39;s hash function does not match its equality"><del>CLJ-1070</del></a> too, so I went and added the tests from that ticket in to demonstrate this fact. It also tidies up PersistentQueue by removing all equals/hashcCode stuff and all Collection stuff.</p> <p>(It turns out that because ASeq was already implementing Obj, the fact that PersistentQueue was implementing Obj was no barrier to using it.)</p> <p>Would appreciate comments on this approach, and how it differs from the previous patch here and the patch on <a href="http://dev.clojure.org/jira/browse/CLJ-1070" title="PersistentQueue&#39;s hash function does not match its equality"><del>CLJ-1070</del></a>.</p> <p>Looking at EmptyList's implementation of List, it is a duplicate of the others, but it shouldn't be. I think its implementation of indexOf is the biggest culprit - it should just be 'return -1;' but it has a great big for loop! But this is beyond the scope of this ticket, so I won't patch that here.</p> <p>Philip, now that the patch for <a href="http://dev.clojure.org/jira/browse/CLJ-1070" title="PersistentQueue&#39;s hash function does not match its equality"><del>CLJ-1070</del></a> has been applied, these patches no longer apply cleanly. Would you be willing to update them? If so, please remove the obsolete patches.</p> <p>Andy, thanks so much for your efforts to make people aware of these things. I will indeed submit new patches, hopefully later this week.</p> <p>Replaced existing patches with new ones which apply cleanly to master.</p> <p>There are two patches:</p> <p>001-clj-1059-make-persistentqueue-implement-list.diff</p> <p>This fixes equality by making PersistentQueue implement List directly. I also took the opportunity to remove the wildcard import and to add tests for the List methods, as compared with the previous version of the patch.</p> <p>002-clj-1059-asequential.diff</p> <p>This fixes equality by creating a new abstract class ASequential, and making PersistentQueue extend this.</p> <p>My preferred solution is still the ASequential patch, but I'm leaving both here for comparison.</p> <p>Vetting. </p> <p>Philip, this time I think it was patches that were committed for <a href="http://dev.clojure.org/jira/browse/CLJ-1000" title="Performance drop in PersistentHashMap.valAt(...) in v.1.4 -- Util.hasheq(...) ?"><del>CLJ-1000</del></a> that make your patch 002-clj-1059-asequential.diff not apply cleanly. I often fix up stale patches where the change is straightforward and mechanical, but in this case you are moving some methods that <a href="http://dev.clojure.org/jira/browse/CLJ-1000" title="Performance drop in PersistentHashMap.valAt(...) in v.1.4 -- Util.hasheq(...) ?"><del>CLJ-1000</del></a>'s patch changed the implementation of, so it would be best if someone figured out a way to update this patch in a way that doesn't clobber the <a href="http://dev.clojure.org/jira/browse/CLJ-1000" title="Performance drop in PersistentHashMap.valAt(...) in v.1.4 -- Util.hasheq(...) ?"><del>CLJ-1000</del></a> changes.</p> <p>Thanks Andy. Submitted a new patch, 002-clj-1059-asequential-rebased-to-cached-hasheq.diff, which supersedes 002-clj-1059-asequential.diff.</p> <p>The patch 001-clj-1059-make-persistentqueue-implement-list.diff still applies cleanly, and is still an alternative to 002-clj-1059-asequential-rebased-to-cached-hasheq.diff.</p> Approval Vetted Global Rank Patch Code and Test