On Sun, Jan 9, 2011 at 9:23 AM, Stuart Halloway <stuart.hallo...@gmail.com> wrote: > Additional corner cases to consider: > > * nil
Tricky one. It's clearly atomic in the usual sense; at the same time it can stand in for an empty coll in many cases. I'd call it atomic. > * arrays Nonatomic. Is there an #(instance? X %) test, with some substitute for X, to detect them though? > * poorly-designed Java classes that are clearly collection-like but don't > implement collection interfaces. There's no theoretical way to detect all of these automatically, even with heavy use of reflection and debug-inspectors. There are surely ways to disguise collections such that the general case of recognizing them is equivalent to the halting problem. In practice, you might want to either just treat anything that's not an array or a java.util collection as atomic, or else provide a hook for the caller to supply exceptions: (defn atom? ([x] (atom? x (constantly false))) ([x exception?] (not (or (instance? java.util.Collection x) (instance? java.util.Map x) (.isArray (.getClass x)) (exception? x))))) (atom? [1 2 3]) => false (atom? {:a 1 :b 2}) => false (atom? (make-array String 3)) => false (atom? (java.util.HashMap.)) => false (atom? 3) => true (atom? 3 #(instance? Number %)) => false I'd also say that String is a slightly tricky one, having collection-like behavior (it's a freaking list of characters!) but being very commonly used as an atomic thing more than as a collection. Symbols and keywords should definitely be regarded as atomic. -- 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