gen test function reading from cli argumant

CliArg.gren

module TestMain exposing ( main )

import Node
import Node.Program as Program exposing ( Program )
import Stream exposing ( Stream )


main : Program Model Msg
main =
    Program.define
        { init = init
        , update =
            \msg model ->
                { model = model
                , command = Cmd.none
                }
        , subscriptions = \_ -> Sub.none
        }


type alias Model =
    { stdout : Stream
    , stderr : Stream
    }


type Msg
    = Log


init :
    Program.AppInitTask
        { model : Model
        , command : Cmd Msg
        }
init =
    Program.await Node.initialize
        <| (\nodeConfig ->
                Program.startProgram
                    { model =
                        { stdout = nodeConfig.stdout
                        , stderr = nodeConfig.stderr
                        }
                    , command =
                        case nodeConfig.args of
                            [ _, _, input ] ->
                                case String.toInt input of 
                                    Nothing ->
                                        Stream.sendLine nodeConfig.stderr <|
                                            "Exactly one argument is required: input should be integer"

                                    Just num -> 
                                        Stream.sendLine nodeConfig.stdout
                                            -- <| Debug.toString (unsafeToDigit 15)
                                            -- <| Debug.toString (Array.first [])
                                            <| Debug.toString (String.fromInt num)
                            _ ->
                                Stream.sendLine nodeConfig.stderr <|
                                    "Exactly one argument is required: the integer to convert"
                    }
            )

Main.gren

module Main exposing ( main )

import Node
import Node.Program as Program exposing ( Program )
import Stream exposing ( Stream )


main : Program Model Msg
main =
    Program.define
        { init = init
        , update =
            \msg model ->
                { model = model
                , command = Cmd.none
                }
        , subscriptions = \_ -> Sub.none
        }


type alias Model =
    { stdout : Stream
    , stderr : Stream
    }


type Msg
    = Log


init :
    Program.AppInitTask
        { model : Model
        , command : Cmd Msg
        }
init =
    Program.await Node.initialize
        <| (\nodeConfig ->
                Program.startProgram
                    { model =
                        { stdout = nodeConfig.stdout
                        , stderr = nodeConfig.stderr
                        }
                    , command =
                        Stream.sendLine nodeConfig.stdout
                            -- <| Debug.toString (unsafeToDigit 15)
                            -- <| Debug.toString (Array.first [])
                            <| Debug.toString (strTail "ABC")
                    }
            )

strTail : String -> Array Char
strTail str =
    case Array.popFirst (String.toArray str) of
        Nothing ->
            []

        Just { first = head, rest } ->
            if Array.isEmpty rest then
                []
            else
                  rest