Evolving the OCaml Programming Language (2025) [pdf]
1–10 of 52 posts
Re: Evolving the OCaml Programming Language (2025) [pdf]
#2I am the author of the talk here o/.
This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler.
Happy to answer questions, but also, more importantly, hear your comments and criticisms around the compiler development process, ideas to make it more approachable, etc.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#3I am the author of the talk here o/. This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler. Happy to answer questions, but also, more importantly,…
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
Re: Evolving the OCaml Programming Language (2025) [pdf]
#4I am the author of the talk here o/. This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler. Happy to answer questions, but also, more importantly,…
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
You are right that the dynamic arrays story does not read like a straightforward “how to inspire contributions.” But part of what I wanted to do in the talk was to show things as they actually unfolded. In OCaml compiler development, there is a very strong emphasis on correctness and long-term stability. That can make contributions, especially to core language features, feel harder than they might in faster-moving ecosystems.
The dynamic arrays case is a good illustration. What began as a small PR grew into years of design iterations, debates about representation, performance, and multicore safety, and eventually a couple of thousand lines of code and more than 500 comments before it landed. From one perspective, that looks discouraging. From another, it shows the weight we place on getting things right, because once a feature ships, it is very hard to undo.
That tension, between wanting to be open and encouraging contributions but also needing to protect stability, is something I think we should be talking about openly. My hope is that by making the process more visible we can demystify it and help contributors understand not just what happened, but why.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#5I am the author of the talk here o/. This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler. Happy to answer questions, but also, more importantly,…
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
Maybe what I read here is “this is how contributions go”…
Get the API right first. Make sure it’s correct, safe, and useful. Iterate on the performance afterwards.
IMO, a lot of contributions should take this shape.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#6Earlier quoted context omitted.
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
Maybe what I read here is “this is how contributions go”… Get the API right first. Make sure it’s correct, safe, and useful. Iterate on the performance afterwards. IMO, a lot of contributions should take this shape.
It is often hard to see the shape of these things before a serious PR attempt is made. Each of the PRs reveals more of the shape of the problem being solved. Hard to skip them in practice, especially for new contributors.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#7I am the author of the talk here o/. This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler. Happy to answer questions, but also, more importantly,…
I'm at a conference at the moment so can't give a lengthy answer, but I'm the maintainer of virt-v2v, one large open source OCaml project (large if you include all the dependencies) which generates actual multi-millions in annual revenue, but is often overlooked in all this discussion of the OCaml ecosystem. Glad to talk by email some time.
[BTW we currently have open positions for two developers]
Re: Evolving the OCaml Programming Language (2025) [pdf]
#8I am the author of the talk here o/. This talk is a _subjective_ take on how the OCaml programming language evolves, based on my observations over the last 10 years I've been involved with it. My aim/hope is to demystify the compiler development process and the tradeoffs involved and encourage more developers to take a shot at contributing to the OCaml compiler. Happy to answer questions, but also, more importantly,…
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
I think it's just the nature of the beast, in this case. Serious "industrial" implementations of a programming language might stick around for a long time, and breaking things a lot can mar the appeal; getting it right the first time pays off in that case.
I think the acceptance threshold can be much lower in other kinds of tooling. "It is what it is", so to speak.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#9Earlier quoted context omitted.
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
You are right that the dynamic arrays story does not read like a straightforward “how to inspire contributions.” But part of what I wanted to do in the talk was to show things as they actually unfolded. In OCaml compiler development, there is a very strong emphasis on correctness and long-term stability. That can make contributions, especially to core language features, feel harder than they might in faster-moving ec…
A point that I find missing in the timeline for dynamic array is that there have been implementation for dynamic arrays available in libraries for more than twenty years.
However, none of the authors of those libraries were really happy with their own implementation because those implementations had to choose between performance, API usability or thread safety.
When I closed the student pull request (which was a naive implementation with no unsafe features), it was with the idea that it was unfair to expect a beginner use to solve those issues.
The subsequent iterations explored different part of the design space before the final iteration which converged to safely using unsafe language features to reach a new local API optimum.
Re: Evolving the OCaml Programming Language (2025) [pdf]
#10Earlier quoted context omitted.
To be honest the story about the two closed PRs for dynamic arrays doesn't really inspire contributions :)
You are right that the dynamic arrays story does not read like a straightforward “how to inspire contributions.” But part of what I wanted to do in the talk was to show things as they actually unfolded. In OCaml compiler development, there is a very strong emphasis on correctness and long-term stability. That can make contributions, especially to core language features, feel harder than they might in faster-moving ec…
I think this is the tension in most software. If you want to have excellent and correct software it will take time.
And if you want more features with a "fix as you go approach" you will often have huge technical debt and get saddled with poor interfaces, often forever.
But, I think OCaml errs too much on the side of getting it right the first time. The result is that state of the art keeps moving far ahead. By the time OCaml "catches up" the field of programming languages has moved far ahead. So OCaml always remains the Jack of all trades and the master of none (IMHO).
I like the direction OxCaml is taking. But the problem is that no one has another 10 years to see its learnings get folded back into OCaml. There is a real chance that OxCaml may diverge so much that it becomes impractical to merge it into OCaml. Flambda2 is another great piece of software that may also take a long time to come into OCaml proper.
So I feel that things need to be "speeded up" if OCaml has to become a bigger ecosystem. You can see that some big projects are moving away from OCaml -- facebook for instance used to have their python typechecker in OCaml. Their new one, pyrefly is in Rust. This could be an isolated story, no doubt.