edn VS dhall-lang

> was utterly surprised how no one ever apparently has thought to create a configuration/templating system that's basically a fancy library on top of Scheme.

There's Clojure's extensible data notation: https://github.com/edn-format/edn

A thin language layer around edn/datalog, the query language

EDN (Extensible Data Notation) is a subset of Clojure: https://github.com/edn-format/edn

It is:

- Streamable

- Extensible

- Whitespace-insensitive, but there are formatting conventions for readability

To begin with, EDN is somewhat like the JSON of Clojure. And regarding the code is data/data is code nature of Clojure, it is Clojure. It doesn't have some of the vagaries of JSON, and it is also extensible.

Alien is not a reason something is bad, just that's it's unusual. JSON was a bit alien when it first arrived as well, as everyone was used to XML at the time.

`{num 5, val 4}` looks fine to me, but we can do even better! We already know objects/maps are always in pairs, so we don't really need that comma either. Just do `{num 5 val 4}` and we save yet another unnecessary characters.

Of course, I didn't come up with this format myself, what I actually want JSON to be is EDN (https://github.com/edn-format/edn) which is a standalone format but also directly used in Clojure, so it already exists inside a programming language and works very well. There keys are strings though, so you example would end up being `{"num" 5 "val" 5 "person" var}`, where commas are optional.

I just checked out the spec, and it gets pretty ugly in the Table section. A lot of the json examples are both shorter and IMO more precise. Stuff that’s not allowed with [table] is allowed with [[table]], and it’s confusing to understand what level of depth I’m at.

I’ll take edn over any of “em. https://github.com/edn-format/edn

As XT is written in Clojure and it natively supports Clojure’s data types, we were not satisfied with available JSON types and decided to give EDN a try - that way we would have way more supported types:

Compare the nightmare that is pickling with how simple it is to serialize pure data with edn in clojure. What ends up happening is people passing around JSONs or whatever and writing parsing/encoding code at each end, which makes things unnecessarily more complex, and dangerous, and error prone, and boring, etc...

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/