On Mar 1, 2013, at 13:36 , AtKaaZ <atk...@gmail.com> wrote: > I don't think I understand what you mean (could you rephrase/example?), I > cannot think of a case when I wouldn't want it to throw when I'm passing a > non-number (contains? [:a :b :c] :a), I mean, rather than just silently > ignoring.
I'm talking about a case where you have one or more associative containers of unknown types, and you want to be able to generically ask them whether they contain a particular key. E.g.: (defn has-foo? [c] ;; c is only known to be Associative (contains? c :foo)) Insofar as a vector can be viewed as a kind of associative container, one might expect/desire this code to just return false if c happens to be a vector. One could see this as a question about the contract promised by the Associative interface: is is always OK to ask an Associative container whether it contains a given key, or are implementations free to accept only certain kinds of keys? I could go either way on that personally, but I can't find any docs that support one interpretation or the other. > It;s not unlike this: > => (contains? '(:a :b :c) :a) > IllegalArgumentException contains? not supported on type: > clojure.lang.PersistentList clojure.lang.RT.contains (RT.java:724) > > it throws because, it's similarly better than just ignoring it and > propagating the bug somewhere else. Different case, because lists aren't Associative. > In a way, it's already so for String: > => (contains? "aaa" 1) > true > => (contains? "aaa" 3) > false > => (contains? "aaa" "a") > IllegalArgumentException contains? not supported on type: java.lang.String > clojure.lang.RT.contains (RT.java:724) > => (contains? "aaa" 'a) > IllegalArgumentException contains? not supported on type: java.lang.String > clojure.lang.RT.contains (RT.java:724) This one's actually quite surprising to me. I don't know why 'contains? throws when given a String and a non-numeric argument, since that's inconsistent with its behavior on vectors (and the exception's description seems inaccurate, since 'contains? *is* supported on Strings). Even more strangely: user=> (contains? "abc" 1.5) true I have no explanation for this. -- -- 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.
