wtf haskell 2

newtype Box a = Box { getMaybe :: Maybe a }
    deriving (Eq,Show)

instance Monoid a => Monoid (Box a) where
    mempty = Box $ Just mempty
    mappend (Box Nothing) a = Box Nothing
    mappend a (Box Nothing) = Box Nothing
    mappend (Box a) (Box b) = Box $ mappend a b