ghc_precedent.hs

Prelude> (fmap . const)  1  [1..5]
[1,1,1,1,1]
Prelude> fmap . const  1  [1..5]

<interactive>:29:1: error:
    • Non type-variable argument in the constraint: Num (a1 -> a -> b)
      (Use FlexibleContexts to permit this)
    • When checking the inferred type
        it :: forall b a (f :: * -> *) a1.
              (Num (a1 -> a -> b), Functor f) =>
              a1 -> f a -> f b

Prelude> (fmap . const ) 2 Just 3
2
Prelude> 2 <$ Just 3
Just 2
Prelude> :t (<$)
(<$) :: Functor f => a -> f b -> f a
Prelude> :t fmap . const
fmap . const :: Functor f => b -> f a -> f b