Why GADTs matter for performance (2015)

I know Jane Street love OCaml, but you have to wonder how much it's cost them in velocity and maintenance. This is a quant firm blogging about a programming language they're the most famous user of.

It is thanks to the companies like Jane Street that believe there is something else beyond C, that we can have nice toys.

Remember if OCaml wasn't a mature programming language, maybe Rust would not have happened in first place.

Why do you assume it's a drag for them and not a competitive advantage? I don't know if it's such a terrible thing to use a slightly out of mainstream language, when the standard in the business is to accumulate tens of millions of lines of C++.

Agreed, indeed I believe they have mentioned that OCaml gets them to ship quicker because they are more confident with the correctness of changes.

But being outside of the mainstream may mean you need to occasionally debug more esoteric stuff: https://gallium.inria.fr/blog/intel-skylake-bug/ I'm sure Jane Street can afford doing that, but I'm not so sure if a small team can.

Concretely how do you think it’s holding them back? Just by being niche?

That was an interesting read, thanks. However I fail to see how it's an issue specific to ocaml. It was a bug in the Skylake processor triggered by a special pattern of instructions produced by gcc. Ocaml built with clang was ok because it doesn't used the same pattern. Did I miss something?

If the JVM encountered the same bug other people would have discovered it before me. Most probably I won't even know the bug exists.

> Why do you assume it's a drag for them and not a competitive advantage?

Because despite them being very open about it, no one else does it, and every distinguished engineer who pushes a weird tech choice will justify and defend it.

There are many things to say about this, but one of those things is that I think you are making the assumption that an (e.g.) C programmer who does not want (or even cannot) get into OCaml would somehow be better for this highly specialized, high-performance, and high-correctness-affine use case, than someone who does. And I'd question that assumption.

It's easier to reason in FP plus the python paradox [1] [2].

[1]: https://www.paulgraham.com/pypar.html

[2]: https://blog.janestreet.com/why-ocaml/

Jane Street has been one of the most successful financial firms of the last 10 years or so, going from a niche hedge fund to a big player. Sounds like OCaml has been working out for them. Certainly I know it's helped them hire a lot of excellent programmers.

For certain classes of programs, yes. I have a hunch finance is a pretty good fit.

I agree with your point about reasoning when employing Functional Programming (FP).

However, I very much disagree with Graham's 2004 assertion[0]:

  It's a lot of work to learn a new programming language. And 
  people don't learn Python because it will get them a job; 
  they learn it because they genuinely like to program and 
  aren't satisfied with the languages they already know.

It does not require "a lot of work to learn a new programming language" once a person has fluency with at least one. Actually, the difficulty of learning a new programming language is inversely proportional to how many programming languages the person has already learned. Especially if a new programming language is in the same paradigm category as those already known (Procedural, OOP, FP, etc.).

I was a professional software engineer in 2004, when the Graham post was written. To say, "people don't learn Python because it will get them a job ..." was bullshit then just as it is now. The remainder of the quoted sentence is unfounded extrapolation and has the value of same.

0 - https://www.paulgraham.com/pypar.html

People that haven’t used ocaml think it’s weird. I picked it up casually in 2020. It might not be popular, but it’s certainly not weird. It’s actually quite fantastic. These days I rarely ever use it, but I wish I did!