If this is not the right forum for these kinds of questions, please point
me to the right place.
Anyway, I try to work my way the The Elm Architecture.
As an exercise, I tried to enhance the Random Dice example by adding a
second die. My idea is to add a second Int to the Model and use the
Random.pair generator to produce random pairs.
This is what I can come up with:
import Html exposing (..)
import Html.App as Html
import Html.Events exposing (..)
import Random
main =
Html.program
{ init = init
, view = view
, update = update
, subscriptions = subscriptions
}
-- MODEL
type alias Model =
{ dieFace1 : Int
, dieFace2 : Int
}
init : (Model, Cmd Msg)
init =
(Model 1 1, Cmd.none)
-- UPDATE
type Msg
= Roll
| NewFace (Int, Int)
update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
case msg of
Roll ->
(model, Random.generate NewFace (Random.pair (Random.int 1 6) (Random.
int 1 6)))
NewFace newFace ->
(newModel, Cmd.none)
newModel : (Int, Int) -> Model
newModel (a, b) =
Model a b
-- SUBSCRIPTIONS
subscriptions : Model -> Sub Msg
subscriptions model =
Sub.none
-- VIEW
view : Model -> Html Msg
view model =
div []
[ h1 [] [ text (toString model.dieFace1) ]
, h1 [] [ text (toString model.dieFace2) ]
, button [ onClick Roll ] [ text "Roll" ]
]
This fails compiling with the following message:
Detected errors in 1 module. -- TYPE MISMATCH
--------------------------------------------------------------- The type
annotation for `update` does not match its definition. 42| update : Msg ->
Model -> (Model, Cmd Msg)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The type annotation is saying: Msg
-> { dieFace1 : Int, dieFace2 : Int }
-> ( { dieFace1 : Int, dieFace2 : Int }, Cmd Msg ) But I am inferring that
the definition has this type: Msg -> (( Int, Int ) -> Model) -> ( ( Int,
Int ) -> Model, Cmd Msg )
I guess what I'm missing is how to create a new Model out of the (Int, Int)
tuple. Maybe this is, however, fundamentally wrong?
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