recursive nodes in Elm

recursive_nodes.elm

module Main exposing (main)

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

-- The node value and a list of child nodes
type Node a
    = Node a (List (Node a))


type alias Model =
    { root : Node Int }


initTree : Node Int
initTree =
    Node -22
        [ Node 42 []
        , Node 100 []
        , Node 43
            [ Node 87 []
            , Node 88
                [ Node 77 []
                , Node 69 []
                ]
            , Node 33 []
            ]
        , Node 10 []
        ]


initialModel : Model
initialModel =
    { root = initTree
    }


viewNode : Node Int -> Html msg
viewNode (Node value nodes) =
    li []
        (List.append
            [ text (String.fromInt value) ]
            [ ul [] (List.map viewNode nodes) ]
        )


view : Model -> Html Msg
view model =
    ul [] [ viewNode model.root ]


type Msg
    = NoOp


update : Msg -> Model -> Model
update msg model =
    case msg of
        NoOp ->
            model


main : Program () Model Msg
main =
    Browser.sandbox
        { init = initialModel
        , view = view
        , update = update
        }