Ejemplo 2 del post "Un sorbo de TEA"

tea.elm

module Counter exposing (..)

import Html exposing (..)
import Html.Attributes exposing (..)
import Html.Events exposing (..)


programParams =
    { model = modelo
    , view = vista
    , update = actualizar
    }


main =
    Html.beginnerProgram programParams



-- MODEL


modelo =
    { cont = 0
    }



-- UPDATE


type Msg
    = Incrementar
    | Decrementar


actualizar mensaje miModelo =
    case mensaje of
        Incrementar ->
            { miModelo | cont = miModelo.cont + 1 }

        Decrementar ->
            { miModelo | cont = miModelo.cont - 1 }



-- VIEW


vista miModelo =
    div []
        [ span [ style [ ( "padding", "5px" ) ] ] [ text (toString miModelo.cont) ]
        , button [ onClick Incrementar ] [ text "+1" ]
        , button [ onClick Decrementar ] [ text "-1" ]
        ]