simple-counter-1.elm

import Html
import Html.Events as HtmlEvt


main =
  Html.beginnerProgram
    { model = init
    , view = view
    , update = update
    }


-- Model


type alias Model = Int


init : Model
init =
  0


-- UPDATE


type Msg = Increment | Decrement


update : Msg -> Model -> Model
update msg model =
  case msg of
    Increment ->
      model + 1
      
    Decrement ->
      model - 1


-- VIEW


view : Model -> Html.Html Msg
view model =
  Html.div []
    [ Html.button [ HtmlEvt.onClick Decrement ] [ Html.text "-" ]
    , Html.div [] [ Html.text (toString model) ]
    , Html.button [ HtmlEvt.onClick Increment ] [ Html.text "+" ]
    ]