Is the dollar operator ($) supported in elm?

Question

In Haskell, you can use the $ operator to clean up bits of code, removing the need for parens.

Does elm support this operator, or something like it?

I can define it myself but I was hoping that this was something built-in.

Here's how it works:

import Html
import List exposing (map, foldr)

datas = [("a", 1), ("b", 2), ("c", 3)]

{--}
($) : (a -> b) -> (a -> b)
($) a b = a b
infixr 0 $
--}

main =
  {-- replace all these parens
  Html.text (toString (foldr (++) "" (map fst datas)))
  --}
  Html.text $ toString $ foldr (++) "" $ map fst datas

Answer 1

Yes, we use <| instead of $. We borrowed it from F# along with the flipped version |> and << for composition . and the flipped version >>.
Once these were introduced, people naturally gravitated towards a style dubbed 'pipelining', where you take some data and transform it in a couple of steps using the |> operator. These days this is a more common code pattern in Elm code than using <|.

For example:

update : (Float, Keys) -> Model -> Model
update (dt, keys) mario =
  mario
  |> gravity dt
  |> jump keys
  |> walk keys
  |> physics dt

(Taken from the Mario example on the website)