haskell - 如何访问 Data.Functor.Of？

Answer 1

The constructor of Of is called (:>):

-- | A left-strict pair; the base functor for streams of individual elements.
data Of a b = !a :> b
    deriving (Data, Eq, Foldable, Ord,
              Read, Show, Traversable, Typeable, Generic, Generic1)
infixr 5 :>

so you should be able to do something like

n :> _ <- length bs