On Wed, Apr 28, 2010 at 10:49 PM, Douglas Philips <d...@mac.com> wrote: > What is the purpose, goal, design-rationale of not making seq-contains? fast > on maps or sets?
I think Rich's point is that if seq-contains? is sometimes fast and sometimes slow, then it makes it harder to reason about a program that uses seq-contains?. Is this one of the "slow" usages, or one of the "fast" usages? On the other hand, with the current plan, you know exactly what performance you're getting. contains? will always be fast on sets and maps (albeit returning meaningless results for lists, and counterintuitive results for vectors). seq-contains? always does a linear search. So if you see seq-contains? in your code, this serves as a big red flag that either you should be using a set data structure and contains?, or you better be sure your sequence is relatively small. If seq-contains? sometimes had good performance, then people would start using a mixture of seq-contains? and contains? for sets and maps, and it would be less clear when you were using seq-contains? "improperly". > I generally agree with the design Clojure embodies as an outlook :). > As to contains? ... I agree with Mark Engelberg's detailed analysis and > conclusions. Thanks. But I definitely see the logic of Rich's approach as well. As a side note, maybe contains? should return an error message when used on a non-keyed collection like a list. With the confusion that's sure to result from having both contains? and seq-contains? in the core with slightly different semantics, applicable inputs, and performance, an error message for inappropriate uses of contains? would be very valuable, I think. -- 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
