On Thursday, October 1, 2015 at 2:31:46 PM UTC-5, Dave Tenny wrote: > > So I understand that 'seq' is the idiomatic way to see if a > collection/sequence is empty. > > I'm not sure where you got this from. I personally use empty? to check whether a collection is empty. It is true that (not (empty c)) is not encouraged. I believe the main rationale for this this is that (empty c) is (not (seq c)), so (not (empty c)) is (not (not (seq c)).
> Logically I'm looking for an O(1) predicate with which I can determine if > a seq/collection is empty, and a well behaved > one that is idempotent and side effect free (for general performance > reasons). > I believe all the implementations of seq in Clojure core are O(1), although some (most?) allocate objects. I'm not sure if it's explicitly spelled out anywhere, but I would consider it a bug it was anything other than O(1) (or perhaps O(log n) at most). In what ways is the current implementation of empty not well behaved and idempotent? With regards to side effects, if you can find a completely generic, side-effect-free way of determining whether a lazy sequence is empty without potentially realizing its head, please let the Clojure community know! I'm not saying having an explicit 'empty' method is a bad idea, but I'm not sure the current situation is as bad as you think. Nathan Davis -- 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/d/optout.
