Thank you very much to all for comprehensive explanations. As newcomer to Clojure dare to remark that this is not very consistent semantics of "contains" :)
On 25 июн, 21:25, ataggart <alex.tagg...@gmail.com> wrote: > 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
