scotty VS dhall-lang

I would suggest checking out scotty for the http server - it uses warp by default, and is very beginner-friendly.

Here's the current commit I'm working with: https://github.com/scotty-web/scotty/commit/3ed8586c046b46dc42740e8ac2e7fe712e84191d

If you're not a fan of the ruby-on-rails / swiss army knife approach that IHP takes, check out Scotty. Add Lucid for Html rendering, and Selda for Postgres. (There are other options for any of these tools if you prefer)

- Scotty (simple web routing) https://hackage.haskell.org/package/scotty

Writing a Haskell webserver (maybe using scotty) and call it from node.

I've been looking for this as well, and found the globalstate.hs example in the scotty github repository. It uses a ReaderT of a TVar and shows how to update or read shared state in memory.

I've found htmx and hyperscript talking to scotty to be an easy way to get something like this going while retaining the joys of Haskell on the backend and avoiding the pains of Haskell on the frontend.

Finally, to add my opinion in the context of some other posts: I'd suggest Scotty (and probably other libraries I'm less familiar with) before Servant in particular, as Servant is a lot to absorb if you're also trying to build fluency in Haskell at the same time. Similarly, I'd advocate for Elmish (disclaimer, it's written by (very talented programmers other than myself at) my company) over Halogen, at least based on the last time I tried Halogen--I found it pretty complex as well. Don't get me wrong, I think Servant and Halogen are both great, just...complex.

This is an example of REST API built with Scotty a web framework of Haskell and PostgreSQL a relational database. It's a simple API to manage products.

Not that I'm much of an expert, but if you're talking about a very barebones static single-page-app, then you could very easily get by just using blaze-html to put your elements on the page, and then scotty is a basic web framework you could use to serve up your app.

Fail to see how this is any different than Dhall (https://dhall-lang.org/) other than it produces plists too.

Kubernetes config is a decent example. I had ChatGPT generate a representative silly example -- the content doesn't matter so much as the structure:

https://gist.github.com/cstrahan/528b00cd5c3a22e3d8f057bb1a7...

Now consider 100s (if not 1000s) of such files.

I haven't given Pkl an in depth look yet, but I can say that the Industry Standard™ of "simple YAML" + string substitution (with delicate, error prone indentation -- since YAML is indentation sensitive) is easily beat by any of:

- https://jsonnet.org/

- https://nickel-lang.org/

- https://nixos.org/manual/nix/stable/language/index.html

- https://dhall-lang.org/

- (insert many more here, probably including Pkl)

There are underpowered languages / tools, that can only solve a problem for which they are intended poorly. But not all limited tools are like that.

Say, eBPF is prominently not Turing-complete, which allows to guarantee that a eBPF program terminates, and even how soon. Still eBPF is hugely useful in its area.

Or, say, regular expressions are limited to regular languages; in particular, they famously [1] cannot process recursive structures, like trees. Still tools like grep / ag / rg are mightily useful.

Yes, I agree that YAML is underpowered for proper k8s configuration! But it's also too powerful for its own good in other aspects [2]. I wish Google used Dhall [3] or their own purely functional config language (FCL? I already forgot the name) instead of YAML; sadly, they did not.

[1]: https://stackoverflow.com/a/1732454/223424

[2]: https://ruudvanasseldonk.com/2023/01/11/the-yaml-document-fr...

[3]: https://dhall-lang.org/

Dhall: Dhall is a programmable configuration language that combines features like JSON, functions, types, and import capabilities. Its style leans towards functional programming, so if you're familiar with functional-style languages such as Haskell, you might find Dhall to be quite intuitive.

I've been thinking along these lines but more 'strongly validated' than statically typed in the sense that you'd be better off being able to load the entire config and then produce a list of problems (and should be able to offer good editor support if done correctly).

Though https://dhall-lang.org/ demonstrates that you can statically type quite a lot of configuration to great advantage, which appears to be programmatically embeddable in multiple languages per https://docs.dhall-lang.org/howtos/How-to-integrate-Dhall.ht...

> Where practical is in the sense of an engineer (or in their terms, a CS practitioner),

Configuration processing. E.g. I'd like my yamls to be decidable, though I'd settle for guaranteed to halt[1].

[1] https://dhall-lang.org/

Maybe you'd like jsonnet: https://jsonnet.org/

I find it particularly useful for configurations that often have repeated boilerplate, like ansible playbooks or deploying a bunch of "similar-but" services to kubernetes (with https://tanka.dev).

Dhall is also quite interesting, with some tradeoffs: https://dhall-lang.org/

A few years ago I did a small comparison by re-implementing one of my simpler ansible playbooks: https://github.com/retzkek/ansible-dhall-jsonnet

And to checkout Dhall: https://dhall-lang.org/