(.g) us a field selector, is (. g) then a function :: (a -> b) -> c -> b?

giraj · on Sept 21, 2020

Yep! You could check this in GHCi (the repl), for example:

  > :t (. id)
  > (. id) :: (b -> c) -> b -> c

(:t prints the type of an expression, and id is the "identity function" that's b -> b here.)

(EDIT: Maybe you know the above and you're asking if it's being changed in the proposal. It doesn't seem so to me.)

thomasahle · on Sept 21, 2020

I'm just pointing out that the difference between (.g) and (. g) is potentially easy to miss.