My sense from reading Rich's writing on the subject is that 'contains? was named with the use of sets in mind. There is also a pairing logic involved whereby if 'contains? returns true, the the value returned by 'get is valid (this covers cases in maps where the value actually is nil).
As Meikel indicated, this is a well-worn path of discussion and isn't going to change. On Jun 25, 5:15 am, Peter Schuller <peter.schul...@infidyne.com> wrote: > > Explain me this, please: > > > user=> (def x (cons 'a nil)) > > #'user/x > > user=> x > > (a) > > user=> (contains? x 'a) > > false > > user=> > > contains? checks whether the collection contains the *key*, not the > value. So for example the list [:a :b] contains keys 0 and 1, but not > 2 or :a: > > user=> (contains? [:a :b] 0) > true > user=> (contains? [:a :b] 1) > true > user=> (contains? [:a :b] 2) > false > user=> (contains? [:a :b] :a) > false > > That said, it was not obvious from (doc contains?) to me what the > semantics were for operating on lists. Checking PersistentList, it > seems contains() always returns false - which makes sense if you > consider that lists are not functions of indexes (while vectors and > java arrays are). > > -- > / Peter Schuller -- 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
