Hi Nipra, 2009/11/27 nipra <prabhakar.nik...@gmail.com>: > Hi, > (rest *v1) is equal to *v2 in the below mentioned example. Then why > `conj' operation on them is returning different things. > > user> (def *v1 [1 2 3 4 5]) > #'user/*v1 > user> (def *v2 [2 3 4 5]) > #'user/*v2 > user> (= (rest *v1) *v2) > true > user> (def *v3 (conj (rest *v1) 0)) > #'user/*v3 > user> *v3 > (0 2 3 4 5) > user> (def *v4 (conj *v2 0)) > #'user/*v4 > user> *v4 > [2 3 4 5 0] > user> (map #(class %) (list *v1 *v2 *v3 *v4)) > (clojure.lang.PersistentVector clojure.lang.PersistentVector > clojure.lang.Cons clojure.lang.PersistentVector) > user>
(rest) returns a seq rather than a vector: user> (class (rest *v1)) clojure.lang.PersistentVector$ChunkedSeq and (conj) does different thing on seqs and vectors: user> (conj '(1 2 3) 0) (0 1 2 3) user> (conj [1 2 3] 0) [1 2 3 0] namely, conj on a vector appends the new element to the vector, and conj on a seq (or a list) prepends the new element. So, in effect you are testing the equality of (0 2 3 4 5) and [2 3 4 5 0] which are not the same, as you found out. Finally, the equality check on (rest *v1) and *v2 succeeds, because (=) treats both (rest *v1) and *v2 as seqs and traverses both checking each element for equality, i.e. it does not care that the containers are of different types. > Regards, > nipra -- ! Lauri -- 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
