Lisplog

Trouble with text inputs and double update roundtrips

via Elm - Latest posts by @lazurski Tad Lispy on Thu, 08 Oct 2020 08:18:01 GMT

I’ve run into strange behavior of text input elements in combination with “double update” - i.e. process Msg from input, issue a Cmd Msg and update model in the subsequent update, like this:

| user input | -- Msg1 value --> | update (model unchanged yet) | -- Cmd (Msg2 value) --> | update (model changed) |

Following is some background.

In my app I have a complex type representing a document. There are many possible transformations that can be applied to it. For versioning purposes every time any transformation is applied I need to capture and store the current time. I want my type to be opaque and transformations to be atomic. But to get time I need to perform a Time.now task and get another Msg with time. I can’t think about any other way than having two updates for every input event.

I came up with something like this:

apply : (Doc -> Doc) -> Doc -> Task Never Doc
apply transform doc =
    Task.map (\time -> transform { doc | version = time }) Time.now

Now when user types in an input I issue an InputChanged message and in the update I return a Cmd constructed with the above apply function. This works, except when the user types in the middle of the text the cursor jumps to the end of the input. Also undo is not working anymore.

Here is a reduced example: https://ellie-app.com/bbLDGML6PbFa1

In writing this I have two goals:

1. I suppose I should open an issue somewhere, but I’m not sure where.

   In the elm/virtual-dom, elm/html or somewhere else? Or am I just doing it wrong?

2. I’d like to find a nice way to structure this flow. Any suggestions?

Zach Beane: Non-symbols as keyword arguments

via Planet Lisp by on Wed, 07 Oct 2020 13:05:25 GMT

Sometimes I like to have a short function call to make a lookup table with arbitrary keys and values. Something like this:

(table "name" "Alice" "age" 42) => #<TABLE ...>

This is easy enough to define like so:

(defun table (&rest keys-and-values)
   ;;; loop over keys and values to construct a table
   ...)

But there’s another option that works:

(defun table (&rest keys-and-values &key &allow-other-keys)
  ...)

This version has the advantage that missing arguments (e.g. (table "name")) are caught at compile-time!

I’ve been using this construct for a few years, but recently found out about 3.5.1.5, which says:

It is not permitted to supply a keyword argument to a function using a name that is not a symbol.

Yikes! That seems simple and straightforward: what I’m doing is not permitted. However! Every implementation I’ve tried (only three, admittedly) actually allows my not-symbol keywords without complaint!

I’m too old to think that “it works everywhere today” means “it will continue to work in SBCL tomorrow”, so I’m trying to figure out where I stand. 3.5.1.5 also says this:

If this situation occurs in a safe call, an error of type program-error must be signaled unless keyword argument checking is suppressed as described in Section 3.4.1.4.1 (Suppressing Keyword Argument Checking); and in an unsafe call the situation has undefined consequences.

So does that mean my code is:

• a safe call with suppressed keyword argument checking?
• …and is that good to use now and forever?
• an unsafe call with undefined consequences?
• something else?

I know the same effect could be achieved with a compiler macro, but I’d like to know if I can use this simpler option safely.

Non-symbols as keyword arguments

via Zach Beane Common Lisp by on Wed, 07 Oct 2020 13:05:25 GMT

Sometimes I like to have a short function call to make a lookup table with arbitrary keys and values. Something like this:

(table "name" "Alice" "age" 42) => #<TABLE ...>

This is easy enough to define like so:

(defun table (&rest keys-and-values)
   ;;; loop over keys and values to construct a table
   ...)

But there’s another option that works:

(defun table (&rest keys-and-values &key &allow-other-keys)
  ...)

This version has the advantage that missing arguments (e.g. (table "name")) are caught at compile-time!

I’ve been using this construct for a few years, but recently found out about 3.5.1.5, which says:

It is not permitted to supply a keyword argument to a function using a name that is not a symbol.

Yikes! That seems simple and straightforward: what I’m doing is not permitted. However! Every implementation I’ve tried (only three, admittedly) actually allows my not-symbol keywords without complaint!

I’m too old to think that “it works everywhere today” means “it will continue to work in SBCL tomorrow”, so I’m trying to figure out where I stand. 3.5.1.5 also says this:

If this situation occurs in a safe call, an error of type program-error must be signaled unless keyword argument checking is suppressed as described in Section 3.4.1.4.1 (Suppressing Keyword Argument Checking); and in an unsafe call the situation has undefined consequences.

So does that mean my code is:

• a safe call with suppressed keyword argument checking?
• …and is that good to use now and forever?
• an unsafe call with undefined consequences?
• something else?

I know the same effect could be achieved with a compiler macro, but I’d like to know if I can use this simpler option safely.

Can we create Mobile apps in elm?

via Elm - Latest posts by @Noob_Programmer Noob Programmer on Wed, 07 Oct 2020 09:20:17 GMT

thanks then flutter is the thing i’m looking for.

Can we create Mobile apps in elm?

via Elm - Latest posts by @opvasger Asger Nielsen on Wed, 07 Oct 2020 09:06:30 GMT

You can get pretty far with progressive-web-apps, but you’ll have some “wiring” written in Elm. Also, if you have major features that rely on stuff Elm can do on it’s own, it might get hairy if you don’t like JavaScript/TypeScript.

My approach has been:

1. build the Elm-project, where only the little bit of JavaScript required to initialize the app and setup ports is written
2. Build typescript-modules for specific features, ensure they have nice autocomplete in VS-Code, and deploy them to NPM for import into the main project.

In my mind, Elm is being really ambitious about what our APIs should look like, and for that reason, we’re taking our sweet time getting support for a lot of stuff. Ports are nice once you get the hang of it

Elm in a nutshell

via Elm - Latest posts by @system system on Wed, 07 Oct 2020 07:56:25 GMT

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.

Can we create Mobile apps in elm?

via Elm - Latest posts by @Noob_Programmer Noob Programmer on Wed, 07 Oct 2020 04:58:00 GMT

Im about to start a startup , so we want to build mobile apps that’s our targeted audience .
So heres the thing i dont like JS and especially react.js and flutter is some bunch of widgets . So im wondering can we make our front end of our mobile apps in elm i dont know much about front end .
any advice would be greatful.

Need to hire Elm developer

via Elm - Latest posts by @CrewNew Kaspar L. Palgi on Tue, 06 Oct 2020 10:50:47 GMT

Hey guys! Hope it’s allowed to post here but as it’s pretty hard to find Elm devs in other usual freelance sites from where we have got all the great Vue/Rect devs then trying here. Pls email me kaspar@crewnew.com if you’re Elm dev and want to work with cool startup built in Elm and Node. Thanks.

New Elm Language Server and VS Code plugin versions

via Elm - Latest posts by @opvasger Asger Nielsen on Tue, 06 Oct 2020 02:04:20 GMT

Amazing work Thank you so much

New Elm Language Server and VS Code plugin versions

via Elm - Latest posts by @razze Kolja Lampe on Mon, 05 Oct 2020 22:52:57 GMT

inference completions800×433 511 KB

make declaration from usage800×433 407 KB