newtype CustomList a = CustomList [a] deriving Show

instance Functor CustomList where
    fmap f (CustomList lst) = CustomList $ fmap f lst

instance Applicative CustomList where
    pure x = CustomList $ repeat x 
    {-
    -- default implementation
    pure x = CustomList [x]
    (CustomList fs) <*> (CustomList xs) = CustomList $ [f x | f <- fs, x <- xs] 
    -}
    (CustomList fs) <*> (CustomList xs) = CustomList $ zipWith ($) fs xs