Command Line Flags in Elm

Here’s the translation of the Go code to Elm, formatted in Markdown suitable for Hugo:

import Html exposing (text)

main =
    text "hello world"

Our first program will print the classic “hello world” message. Here’s the full source code.

In Elm, we don’t have the concept of command-line flags as we do in other languages. Instead, Elm is primarily used for web applications, and its programs are typically run in a browser environment.

To create a simple “Hello World” program in Elm, we import the Html module and use its text function to display our message.

To run this program, you would typically:

Save it in a file, for example, HelloWorld.elm.
Use the Elm compiler to compile it to JavaScript:

$ elm make HelloWorld.elm --output=hello.js

Create an HTML file that includes this JavaScript:

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>Hello World</title>
</head>
<body>
    <div id="elm-app"></div>
    <script src="hello.js"></script>
    <script>
        var app = Elm.HelloWorld.init({
            node: document.getElementById("elm-app")
        });
    </script>
</body>
</html>

Open this HTML file in a web browser to see the “hello world” message.

Elm doesn’t have a direct equivalent to command-line flags or a built-in way to parse them. If you need to pass configuration to an Elm application, it’s typically done through flags when initializing the Elm program from JavaScript:

var app = Elm.HelloWorld.init({
    node: document.getElementById("elm-app"),
    flags: {
        word: "opt",
        numb: 42,
        fork: false,
        svar: "bar"
    }
});

Then in your Elm program, you would define a Flags type and use it in your main function:

import Browser

type alias Flags =
    { word : String
    , numb : Int
    , fork : Bool
    , svar : String
    }

main : Program Flags Model Msg
main =
    Browser.element
        { init = init
        , update = update
        , subscriptions = subscriptions
        , view = view
        }

init : Flags -> (Model, Cmd Msg)
init flags =
    -- Use flags to initialize your model
    ...

This approach allows you to pass configuration to your Elm application when it starts up, which is the closest equivalent to command-line flags in the Elm ecosystem.

Command Line Arguments in Elm

Context in Elm

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Command Line Flags in Elm