Lisplog

Mammudeck

Submitted by Bill St. Clair on Tue, 22 Nov 2022 13:49:32 GMT

I retired in November of 2020, because my brain wasn't working. I sat in front of my computer, but nothing happened. Since I'm entirely reliant on my muse to write code, my mother had just died and left me some money, and my social security was enough to live on, I decided to retire.

Two years later, my brain has come back, and I'm writing code every day. Elm code, for my Mammudeck web application, a Tweet-Deck like multi-column interface to the Mastodon Client API. I still execute arithmetic in my Emacs *scratch* buffer, but my Lisp addiction is currently in remission (he said, while typing in a window put up by his Lisplog server).

Mammudeck is a Progressive Web App (PWA), meaning that you can save it to your home screen on a phone or tablet, and save it as a native desktop application from browsers that support that (I've confirmed that in Brave and Chrome).

I've been using Mammudeck for the Fediverse since shortly after it worked well enough for that. I started it on July 4, 2019. With all the new Fediverse denizens, fleeing from Twitter (which I find to be a lot more fun under Elon Musk), I'm finally working on the Account Dialog, so I can see new user profiles and easily follow them or add a column to track their posts.

Once I finish the account dialog, which still needs to display posts, followers, and following, I'll resume work on the DynamoDB backend.

Mammudeck stores state, including OAuth tokens, in the browser's LocalStorage database, but that is seen only by one browser. I use it on my iMac, iPhone, and iPad. The DynamoDB backend will enable sharing state between ALL of your browsers, so changes made in one will be automatically synchronized with the others.

My PWA philosophy is for my web servers to serve only as the source of the code. No other communication is done with them, except for games, which require a place to hold state and communicate between the players. I write those servers in Elm, and run them on the server under Node.JS. Hence, I will NOT be in the shared state database business. Users who want that feature can pay Amazon for the privilege.

Mammudeck is open source. There's a link at the bottom of its home page, to its GitHub repository. If you're interested in helping out, and can illustrate competence in writing Elm, let me know, via the email link at the bottom of this page.

The Web Apps section of my home page (billstclair.com) has a bunch more Web Apps that I've written over the years. All but "Two-Factor Authenticator" and "Conway's Life" are written in Elm. I haven't done the magic to turn most into PWAs. Ask if you want one packaged that way. It's not difficult.

I'm loving writing the code I want, and nothing else, in my retirement.

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Lisplog still works!

Submitted by Bill St. Clair on Tue, 15 Nov 2022 13:48:34 GMT

I haven't added a post here in a long time, nor have I frobbed the server that handles interactive use (the pages themselves are all static HTML, served by Apache). But I was able to log in today, and make this post. Yow! CCL rocks!

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Why Elm?

Submitted by Bill St. Clair on Fri, 19 Jul 2019 10:28:57 GMT

An AngularJS user in the Fediverse asked me to sell Elm to him. This is my first attempt.

I have never used AngularJS or any other JS framework besides jQuery, so I'm operating from a quick perusal of the Angular web site, making my comparisons mostly invalid.

Caveats

First off, you're going to miss a lot of Angular's features with Elm. Elm has a functional flavor to it, not the templatey feel of Angular. Your entire site, except for the initial HTML file that loads the elm-generated JS, is Elm. And Elm wants total control. With a couple of exceptions:

1. You may load Elm into only a single DIV of your larger site, and use regular HTML/JS for the rest of it. This, so I've read, can enable incremental conversion to Elm, but I've never done it.
2. Elm supports two ways to get to your own JavaScript code:
   1. Ports - a send/receive messaging mechanism to get JS data out of and back into Elm. Fully type-safe, since incoming JS data goes through decoders to bring it into Elm, and errors there must be handled by the functional Elm code.
   2. Custom HTML Elements - Since Elm's virtual DOM can support ANY HTML element, you can roll your own, to do anything you can dream up.

Elm's package manager is centered on open source, stored at GitHub. I've proposed a simple mechanism to open this up, so that you can easily define your own package plugins, or not use Microsoft's repository system, but Evan Czaplicki, Elm's creator, has not been open to the idea.

A normal way around this for organizations that need their code to be proprietary is a mono-repo for your code, and just include ths whole thing in every project. Elm's compiler is so fast, and so good at rebuilding only what needs to be rebuilt, and including in the output only what is actually used, that this isn't as bad a solution as it sounds.

Or, if you have Haskell chops, you could fork the Elm source, and add the package manager plugin yourself.

Advantages

Now that I've highlighted some caveats, on to Elm's advantages.

No run-time errors. Ever. If it compiles, the JS generated by the Elm compiler will contain logic errors that you need to find and fix, but it will NEVER mistakenly reference a null value or call an undefined function. This is remarkable to experience, for one accustomed to the runtime-error-prone JS environment. And it really works.

The same kind of type-checking that C programmers have had for decades, but without the necessity to say everything twice, and with a much friendlier compiler, and no way to get around the type safety (except in your own custom JS, as mentioned above). JS linters may give you a lot of this, but they don't do a complete job. The Elm compiler does.

As a long-time lisper, accustomed to run-time type checking, but compile-time laxity, I was surprised to find that I really like this. It takes a little longer to get your code to compile, but once you do, you know it won't fail because of a runtime error.

Refactorings, even large refactorings, are a joy, and usually "just work" once you get the refactored code to compile. In Elm, I'm not afraid to make radical changes to pieces of my code. This causes a large list of compiler errors early in the process, but you fix them one at a time until it builds, and then it usually works.

The generated JavaScript is not difficult to read, and is pretty good, performant code. You definitely lost a little in efficiency over hand-coded JS, but you can always move inner loops into ports if necessary, and it is rarely necessary.

Elm webapps behave pretty much like native apps. With all the JS frameworks available, this isn't as much of a sell as it used to be.

Conclusion

I wish I knew how to express my sheer joy when I program in Elm. If I had Shakespeare's skill, I'd write a sonnet. "Shall I compare thee to a summer's day?"

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ZAP Meme

Submitted by Bill St. Clair on Thu, 18 Apr 2019 05:25:32 GMT

https://zapmeme.com is a meme maker written in Elm.

It's open source, with a link at the bottom of the page. It uses <svg> to layout the meme, and converts to JPEG or PNG for saving.

It stores meme and images (as data:// URLs) in your browser's localStorage database. They may be exported as JSON and imported into another browser.

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Image Sizing in elm-ui

Submitted by Bill St. Clair on Thu, 06 Dec 2018 03:53:36 GMT

I've been using Matthew Griffith's wonderful elm-ui package to make the user interface for GabDecker, a TweetDeck-like web app I'm building for Gab.com. I've had inline images since the beginning, scaled to fit the column width. Today I made clicking on one of those image open a dialog with the full-size version, scaled down if necessary to fit the available space.

elm-ui eschews CSS in the source code, usually making it much easier to get what you want. But in this case, I was NOT getting what I wanted, so I wrote my own CSS, and learned about the object-fit property in the process.

Here's the code that's now running:

imageDialog : String -> Model -> Element Msg
imageDialog url model =
    let
        maxw =
            9 * model.windowWidth // 10

        maxws =
            String.fromInt maxw ++ "px"

        maxh =
            9 * model.windowHeight // 10

        maxhs =
            String.fromInt (9 * model.windowHeight // 10) ++ "px"
    in
    column
        -- This is black magic.
        -- It took much play with the CSS to get it right.
        [ centerX
        , centerY
        ]
        [ standardButton "" CloseDialog <|
            (Html.img
                [ Attributes.style "object-fit" "contain"
                , Attributes.style "max-width" maxws
                , Attributes.style "max-height" maxhs
                , Attributes.style "border" "2px solid black"
                , Attributes.style "width" "auto"
                , Attributes.style "height" "auto"
                , Attributes.src url
                ]
                []
                |> Element.html
            )
        ]

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