I've always felt that Clojure's treatment of nil was somehow inconsistent with the elegance of many other features of Clojure. Now I can finally articulate why: nil complects non-existence, false, and empty.
The choice to make nil represent so many concepts was an "easy" choice, because it saves a few characters when you can write things like (when seq ....) vs. (when (empty? seq) ...) and Clojure implements sequences in a way that the former expression is also a bit more performant. It is also easy in the sense that it is more similar to what Lisp users (as opposed to Scheme) are used to from past experience. But it is decidedly less simple to have these ideas complected. Over the past couple of years, I've seen numerous bugs along the lines of "Your function usually works great, but it breaks when the list/map/vector you pass in contains nil values." It seems clear to me that nil's complexity makes programs harder to analyze, because when you're writing your code, you might be thinking of nil as only representing non-existence or emptiness, for example, and forgetting that the system will treat nil as a false value as well. -- 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
