elm-find-by-type-and-value

Main.elm

module Main exposing (main)

import Browser
import Html exposing (Html, div, text)


type alias Model =
    {}


type Msg
    = NoOp


type Component
    = Name String
    | Speed Float


update : Msg -> Model -> Model
update msg model =
    model


find1 : Component -> List Component -> Maybe Component
find1 component list =
    let
        go cur acc =
            case acc of
                Just comp ->
                    Just comp

                Nothing ->
                    case ( cur, component ) of
                        ( Name curName, Name componentName ) ->
                            if curName == componentName then
                                Just (Name curName)

                            else
                                Nothing

                        ( Speed curSpeed, Speed componentSpeed ) ->
                            if curSpeed == componentSpeed then
                                Just (Speed curSpeed)

                            else
                                Nothing

                        ( _, _ ) ->
                            Nothing
    in
    List.foldl go Nothing list


find2 : Component -> List Component -> Maybe Component
find2 component list =
    let
        go cur =
            case ( cur, component ) of
                ( Name curName, Name componentName ) ->
                    curName == componentName

                ( Speed curSpeed, Speed componentSpeed ) ->
                    curSpeed == componentSpeed

                ( _, _ ) ->
                    False
    in
    list
        |> List.filter go
        |> List.head


toString : Maybe Component -> String
toString comp =
    case comp of
        Nothing ->
            "not found"

        Just c ->
            case c of
                Name name ->
                    name

                Speed speed ->
                    String.fromFloat speed


view : Model -> Html Msg
view model =
    let
        list =
            [ Name "Foo", Speed 1.0, Name "Yoda" ]
    in
    list
        |> find2 (Name "Yoda")
        |> toString
        |> text


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