On 04/30/2014 11:29 AM, Gilberto Melfe wrote:
Hello everybody !
Could someone explain me exactly how this function works?
elementAt_w'pf = (last .) . take . (+ 1)
It's a posted solution to: 99 Haskell problems, problem 3.
I'm having trouble with the "(last .) ." thing!
It's not your fault, that solution is retarded. Once you remove all of the intentional obfuscation, it looks like, elementAt_w'pf n xs = last (take (n + 1) xs) which is easy to understand. You can un-retard it step-by-step: elementAt_w'pf = (last .) . take . (+ 1) <=> elementAt_w'pf n = ((last .) . take . (+ 1)) n = (last .) ((take . (+ 1)) n) = (last .) (take (n + 1)) = last . (take (n + 1)) <=> elementAt_w'pf n xs = (last . (take (n + 1))) xs = last (take (n + 1) xs) All I've used above is the precedence of the function composition operator, and the fact that (f . g) x = f (g x).