Jane Street Open Source (opens in new tab)

Speaking broadly about not only Jane street, but adjacent firms like Jump and Citadel: In my experience (working with and getting coached by a recruiter in the space), these finance companies really want you to love the space, not just the technology. I wasn't able to drink the kool-aid or fake enough die-hard passion for trading to get far in the their interview process, despite having extremely relevant technical capabilities Some are also very elitist with respect to your pedigree, so even amazing experience but no degree from a top US school can make it difficult (yes, even a decade later..)

Apply, like anywhere else. Most quant firms expect you to be pretty strong with C++, but since they use OCaml (and don't expect you to know that) I think you can get away with low-level systems experience more broadly.

No direct experience but I would imagine you would need solid intermediate skills at OCaml, probably being a nerd enough to make your own extensions or the ecosystem for benchmarking and debugging, not just coding. Then a liberal dose of projects about OCaml, game theory, and financial markets. That ought to get their attention at least.

Sure, but Jane Street, as mentioned here, is probably the largest user of it that I'm aware of. It is a great language, but F# is the more pragmatic choice these days. OCaml doesn't have a huge ecosystem where as F# inherits all the .NET libraries.

I've dipped my toes into machine-readable mathematical proofs. The theorem proving software called Coq [1] is written in OCaml.

[1] https://en.wikipedia.org/wiki/Coq_(software)

I've barely touched OCaml but having worked professionally in Haskell for a few years I thought that OCaml was terrible. However, Jane Street has invested heavily in it and maybe their codebase is better than the glimpse I got of the language.

Years ago when I was more active in the OCaml community there were lots of talks of Jane Street programmers (including those who first introduced OCaml there) about why they specifically chose OCaml.

FP provide type system that are really hard to emulate in other languages. Static type interference is easy to use and at the same time extremely powerful. Static type interference with algebraic types is even more powerful.

In addition OCaml has an absolutely pedantic type system. While ints may be implicetly coerced to a double in other languages, this kind of conversion will be rejected by the OCaml compiler.

Since Jane Street uses their code on the stock market for trading, they don't want to have tests showing their code is correct, they want definite proof. And OCaml can in fact provide that. If you write the libraries correctly, the compiler will prove the correctness of the code.

At the same time OCaml isn't as pedantic about coding paradigms as e.g. Haskell, allowing imperative and object oriented code as well. You could do similar proofs in Haskell but a lot of stuff is much harder to do in a language that is pure FP and not multiparadigm.

Jane Street leadership have said that programming languages matter. I think they just really believe in FP.

I think this was the speech 15 years ago when they were just starting. I suspect OCaml isn't relevant in their recruitment strategy, apart from specialized profiles.

Good to know. Thanks!

It was a while ago but Bloomberg FOSSed ComDB which was cool of them:

https://bloomberg.github.io/comdb2/overview_home.html