{-# htermination (foldl1 :: (a -> a -> a) -> (List a) -> a) #-} import qualified Prelude data MyBool = MyTrue | MyFalse data List a = Cons a (List a) | Nil foldl :: (a -> b -> a) -> a -> (List b) -> a; foldl f z Nil = z; foldl f z (Cons x xs) = foldl f (f z x) xs; foldl1 :: (a -> a -> a) -> (List a) -> a; foldl1 f (Cons x xs) = foldl f x xs;