On Fri, Oct 21, 2011 at 11:50 AM, Mark Engelberg <mark.engelb...@gmail.com> wrote: > 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.
Yes: Was that a nil value for the key :foo in my map or did :foo not exist? In Common Lisp, some such functions return multiple values, de-multiplexing (deplecting?) the separate meanings of nil. Then, of course, you need a multiple-values-bind special form to handle those return values. Braids begetting braids. Curious, this, when Clojure already says (not (= nil ())). Mike -- 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
