What does “! []” Elm code syntax in Todomvc mean

Question

Coming from react, I am learning to understand Elm.

In the Todomvc example code, there is the following code snippet:

-- How we update our Model on a         


        

Answer 1

Note that this syntax is going away in the next version of Elm (0.19) so don't get into the habit of using it ;-)

You can use today, and with 0.19:

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
  case msg of
    NoOp ->
      (model, Cmd.none)

Answer 2

Update for Elm 0.19

Elm 0.19 has removed the exclamation point operator. You must now construct the tuple manually, as in (model, Cmd.none).

Original Answer for Elm 0.18

The exclamation point in model ! [] is just a short-hand function for (model, Cmd.batch []), which is the type returned from typical update statements. It is defined here