@@ -19,6 +19,14 @@ app : List a -> List a -> List a
19app [] xs = xs
19app [] xs = xs
20app (x :: xs) ys = x :: app xs ys
20app (x :: xs) ys = x :: app xs ys
22+head : List a -> Maybe a
24+head (x :: xs) = Just x
26+tail : List a -> List a
22length : List a -> Int
30length : List a -> Int
23length [] = 0
31length [] = 0
24length (x :: xs) = 1 + length xs
32length (x :: xs) = 1 + length xs