[Haskell-cafe] xs not in scope

Hello, Im trying to find several answers to problem1 of the 99 haskell problems. Find the last item in a list. Now im trying to find a guarded solution. So far I have this: last3::[a]-> Maybe a; last3 a | [] = Nothing | ([a]) = Just a | (_:xs) = last3 xs But I see this error messages : src/Main.hs@10:8-10:10Not in scope: xs How to solve this ? Roelof