Basic Elm App

counter.elm

import Html exposing (..)
import Html.Events exposing (onClick)

main: Program Never Model Msg
main =
  Html.program
    { init = init
    , view = view
    , update = update
    , subscriptions = subscriptions
    }
    
init : ( Model, Cmd Msg )
init =
  (initialModel, Cmd.none )

-- MODEL

type alias Model =
  {count: Float}

initialModel: Model
initialModel =
  {count = 0}

-- VIEW

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

type Msg = Increment | Decrement

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
  case msg of
    Increment ->
      ( { model | count = model.count + 1 }, Cmd.none )
    Decrement ->
      ( { model | count = model.count - 1 }, Cmd.none )
      
subscriptions : Model -> Sub Msg
subscriptions model =
    Sub.none