It seems that when i get messages saying that "You tripped the alarm! last is bad!" or "You tripped the alarm! nth is bad!", I'm merely being told not to use last or nth as the candidate solutions but instead to write my own functions that achieve the same goal. So the messages "last is bad!" or "nth is bad!" probably just meant "last is forbidden!' or "nth is forbidden!".
My bad! Sorry ... On Jun 9, 10:50 pm, clojurefanxx <neuzhou...@gmail.com> wrote: > i'm a newbie working thru 4clojure.com's problems #19 thru #21 where > i'm asked to write a function, which when given a list or vector, > returns the last, penultimate, or an arbitrary nth element, > respectively. > > for problem #19 (return last element), using the function last was not > accepted as a good solution for both lists and vectors, but the > following was accepted: > > user=> (#(nth % (- (count %) 1)) '(5 4 3)) > 3 > user=> (#(nth % (- (count %) 1)) '[1 2 3 4 5]) > 5 > > for problem #21, (return arbitrary element) , using the function nth > or get was not accepted. > --------------------------------------------------------------------------- > ------------------ > Write a function which returns the Nth element from a sequence. > > (= (__ '(4 5 6 7) 2) 6) > > (= (__ [:a :b :c] 0) :a) > > (= (__ [1 2 3 4] 1) 2) > > (= (__ '([1 2] [3 4] [5 6]) 2) [5 6]) > --------------------------------------------------------------------------- > --------------------- > > i think using the nth or get functions on vectors to return an element > at index position n should be fine performance-wise, > but what's a general solution for lists that will perform better than > O(n)? (i 'm assuming that's the reason why > last, nth, and get were rejected when I tried them out as candidate > solutions??) > > thanks for any help! -- 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
