wherein i learn about my first monad.

marvelous_monadic_mischief.elm

module Main exposing (main)

import Browser
import Html exposing (Html, button, div, text)
import Html.Events exposing (onClick)


type alias Model =
    { count : Int }


initialModel : Model
initialModel =
    { count = 0 }


type Msg
    = Increment
    | Decrement


update : Msg -> Model -> Model
update msg model =
    case msg of
        Increment ->
            { model | count = model.count + 1 }

        Decrement ->
            { model | count = model.count - 1 }


view : Model -> Html Msg
view model =
    div []
        [ button [ onClick Increment ] [ text "+1" ]
        , div [] [ text <| String.fromInt model.count ]
        , button [ onClick Decrement ] [ text "-1" ]
        ]


main : Program () Model Msg
main =
    Browser.sandbox
        { init = initialModel
        , view = view
        , update = update
        }
        
        
mappy : (a -> b) -> Maybe.Maybe a -> Maybe.Maybe b
mappy f m =
  case m of
      Nothing -> Nothing
      Just x -> Just (f x)
      
flatMappy : (a -> Maybe.Maybe b) -> Maybe.Maybe a -> Maybe.Maybe b
flatMappy f m =
  case m of
      Nothing -> Nothing
      Just x -> f x
      
functionPipeline value f g h =
  value
  |> f
  |> g
  |> h
      
monadicPipeline m f g h =
  m
  |> (Maybe.andThen f)
  |> Maybe.andThen g
  |> Maybe.andThen h