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Ask HN: What Is OCaml Used For?

10 points by _fol8 ↗ HN
It looks like an interesting programming language (and the support for multiprocessing looks exciting). However I haven't heard of it used in any large projects that I'm aware of. Some of the packages that would be useful for the projects I might want to work on are years of date, although that could just be selection bias. (But, gtk bindings? Am I missing something?)

Is it more of a research language as opposed to a "making applications" developer language? Can someone provide a little background?

15 comments

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mdaniel
Semgrep is the most famous one I could think of offhand: https://github.com/returntocorp/semgrep/blob/v1.2.1/Dockerfi...

Hyperkit from the docker/moby folks is another: https://github.com/moby/hyperkit/tree/v0.20210107

And while niche, Coq is not exactly unheard of: https://github.com/coq/coq/tree/V8.16.1

If you weren't already aware, GitHub supports searching by the repo's more prominent language: https://github.com/search?o=desc&q=language%3Aocaml&s=stars&...

iforgotpassword
I remember it from mldonkey from back in the day... Afaik the first ed2k capable client for Linux.
kratom_sandwich
Secretive trading firm Jane Street uses OCAML: https://www.janestreet.com/technology/
b20000
i’m curious how they get the low latency performance they need when using a language like ocaml.
nequo
One answer is FPGAs:

https://signalsandthreads.com/programmable-hardware/

Also, OCaml’s garbage collector tries to minimize GC pauses. Here is a slide deck from a somewhat old talk about the now-released multicore GC:

https://kcsrk.info/multicore/gc/2017/07/06/multicore-ocaml-g...

b20000
yeah ok, no interest in a language with a GC. i’ll stick to c++.

are they generating fpga code from ocaml?

nequo
> yeah ok, no interest in a language with a GC. i’ll stick to c++.

If you have already made your mind up, there is hardly a point to your question.

> are they generating fpga code from ocaml?

Yes, they have built a library called Hardcaml to design FPGAs:

https://github.com/janestreet/hardcaml

giraffe_lady
Not every language has a point, really, some of them just exist. You can always find a reason why they continue to. But that doesn't mean it's going to be the best or even a good choice for anything in particular, necessarily.

Many of the core language fundamentals are incredibly sound, and it has a very good performance profile for the features you get. The type system is top notch and and the module system is afaik the only one of its kind and sophistication in a mature language. These all offer benefits that accrue over time, and I think ocaml systems age particularly well and remain easy to maintain. The syntax is french and bad but you get over that in the first year and truly it doesn't matter in the long run.

But yeah the libraries! It's good for when you weren't going to use them anyway because they don't exist. Which is why I think you see it used for research and complex internal finance shit, stuff you couldn't or wouldn't want to use external code for. But it's not as much as a struggle as you'd think, the type system basically feels like a PEG system to start with so it's easy to build robust interfaces to outside systems when you need to.

Personally I mostly use it for things other people use Go for. It has most of the same strengths but not the main weaknesses. But yeah I would kill for a solid modern TUI framework like charm. If I'm writing throwaway code I use something else because there is an overhead to starting new projects in it. If I'm writing a tool I hope or expect to use for years it's my go to though.

mdaniel
> Personally I mostly use it for things other people use Go for. It has most of the same strengths but not the main weaknesses.

So is there the equivalent of `for GOOS in linux windows macos; do for GOARCH in arm64 amd64; do go build ./...; done; done` in ocaml? And, perhaps most important in your comparison, are those resulting binaries statically linked so it's "scp deploy"?

> there is an overhead to starting new projects in it.

I'm guessing that's tightly linked to your "but the libraries don't exist" so one has to roll their own $everything?

giraffe_lady
I don't know, I know multiplatform binaries are truly important for some groups but in my entire career I've never actually needed that a single time on any project. Static linking isn't automatic but you can do it. People tend to always assume you can't? idk why though maybe it used to be a thing.

You don't have to roll your own everything. If you need a library especially something low level or very common like a db driver it'll probably exist. And the libraries that do exist are very solid in my experience. If you need a few libraries it's pretty good odds one will be missing though.

mdaniel
Our team is for sure heterogeneous, and it used to be all 3 OSes before we finally convinced the Microsofty to stop being a snowflake. But regardless, unless it's a very, very specialized team who all run Linux on the desktop, it's almost certainly going to deploy on different OS than one used on the desktop. Now with the M1 debacle, it's multi-arch, too

Anyway, I wasn't trying to lobby you but you said you used it for things you would have used golang for, and that's one of golang's major selling points in my circles, so it seemed like a reasonable question to ask someone who is in that ecosystem

JoeyBananas
> Is it more of a research language as opposed to a "making applications" developer language?

You will never get any OCaml fans to admit it, but yes.

belmont_sup
I admit it. I enjoy it but can’t reasonably suggest it to an employer. F# in the other hand.
jonjacky
"MirageOS is a library operating system that constructs unikernels for secure, high-performance network applications across a variety of cloud computing and mobile platforms. ...

MirageOS uses the OCaml language, with libraries that provide networking, storage and concurrency support that work under Unix during development, but become operating system drivers when being compiled for production deployment. ...

MirageOS 4.0 was released in March 2022, preceded by ... MirageOS 1.0 in December 2013. All the infrastructure you see here is self-hosted. ..."

https://mirage.io/

So this has been going on for 9 years, I presume someone is using it.