I agree with your sentiment. This has been discussed before here: http://groups.google.com/group/clojure-dev/browse_frm/thread/fb3a0b03bf3ef8ca
That discussion pretty quickly wandered into the weeds of whether this sort of usage of protocols was intended or not, fundamentally programmer error or not. There is as yet no input from clojure/core on either question. Maybe someone would like to weigh in on the issue here? - Chas On Feb 28, 2011, at 6:28 AM, Chris Perkins wrote: > I am wondering whether this is a known issue. I made the mistake of > extending a protocol to two interfaces, and then calling it with an > object that implements both. > > (defprotocol Foo > (foo [x])) > > (extend-protocol Foo > clojure.lang.Sequential > (foo [x] "sequential") > clojure.lang.Associative > (foo [x] "associative") > ) > > (dotimes [_ 10] > (println (foo []))) > > You might expect this to print "sequential", or you might expect it to > print "associative", or you might expect an exception. Any of the > these behaviors would seem reasonable to me. > > However, what it actually does is behind door number 4 :) It randomly > chooses one of "sequential" or "associative" for each run of the JVM. > Within a JVM, once it has chosen, it continues to choose the same > value forever, but in a new JVM process it chooses randomly again. > > This caused me a long debugging / hair-pulling-out session because > within my slime repl, my code consistently behaved one way (which, by > luck, happened to match with my mistaken expectations at the time), > but at the same time my unit tests seemed to be passing or failing > without rhyme or reason as I frantically tweaked my code over and > over. > > I don't know, or particularly care, which behavior clojure chooses in > the case of ambiguity like this, but it sure would be nice if it was > predictable. > > - Chris > > -- > 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 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
