OCaml Weekly News

I’m excited to share that Jane Street has opened up a visiting position to work with our type systems team to improve and formalize various aspects of our extensions to OCaml. This position is envisioned to sit between graduation from a PhD program and the start of a tenure-track professorship at a research institution. Candidates might already have a faculty offer in hand and be taking a gap year, or they might be seeking a more traditional postdoc. The visit can last one or two years. It will be research-focused, with a goal of publishing several papers in top venues. The visitor will be able to see firsthand how language improvements affect the users all around us in our office. This will be a great opportunity at combining the theoretical and practical aspects of research in our field.

Full details and next steps are at https://www.janestreet.com/join-jane-street/programs-and-events/visiting-researcher-prefaculty/

I’ll be supervising this position. Happy to answer any questions over email at reisenberg@janestreet.com.

Hello,

It’s my pleasure to announce the release 0.9.5 of Vg:

Vg is a declarative 2D vector graphics library. Images are values that denote functions mapping points of the cartesian plane to colors and combinators are provided to define and compose them.

Renderers for PDF, SVG, Cairo and the HTML canvas are distributed with the library. An API allows to implement new renderers.

Vg is distributed under the ISC license.

Except for the addition of combinators to smoothly stitch Bézier paths by François Thiré, this is mostly a bureaucratic and maintenance release.

At the library level, the Vgr_svg module is now part of the vg library and the vg.svg library is deprecated. The Vgr_htmlc canvas renderer has been rewritten with brr which becomes an optional dependency of the package while the dependencies on js_of_ocaml and js_of_ocaml-ppx are dropped for good.

Ten years ago neither dark themes nor .mld files did exist so the tutorial, the semantics and the image howto have been slightly reworked and moved out of the Vg module documentation to their own pages and the doc images have been fixed to work in dark themes.

Read the release notes for all the other changes.

• Homepage: https://erratique.ch/software/vg
• API docs & manuals: https://erratique.ch/software/vg/doc/
• Install: opam install vg (opam pr)

Best,

Daniel

A big thanks to my donators.

Welcome to the eighth edition of the OCaml Platform newsletter!

In this November and December edition, we are excited to bring you the latest on the OCaml Platform, continuing our tradition of highlighting recent developments as seen in previous editions. To understand the direction we’re headed, especially regarding development workflows and user experience improvements, check out our roadmap.

Highlights:

• The odoc team is starting work on improving odoc performances. After shipping important features, including a link to source code, syntax for tables, and recent support for search, they are turning their focus on consolidating the full documentation generation stack (including Dune rules and integration with OCaml.org package docs) and improving performances.
• opam 2.2~alpha3 is out! It is the last alpha release, and the opam team plans to start the beta release next cycle.
• Anticipating on the January update, the compiler PR necessary for Merlin project-wide references has been merged! This will be part of OCaml 5.2, meaning that starting with the next compiler version, OCaml developers will be able to query for project-wide references (and limited support for project-wide rename!) in their projects. Read more here to know how you can test the feature.

Releases:

• Odoc 2.4.0
• OCaml LSP 1.17.0
• Merlin 4.13
• Dune 3.12.1
• opam 2.2.0~alpha3

The next Caqti release is almost ready if I proceed as planned, though I would like to lift plans in advance in case anyone has feedback.

While Caqti 2 brought support for MirageOS (using PGX), it is missing TLS, which limits its usability in practise. Patching that hole will be the main delivery for the upcoming release. This involved a revision of the network abstraction and better performance under EIO.

Some more minor changes can be seen in the preliminary change log.

Here is a (re-)recording of a talk I gave a few weeks ago at Tarides, about Ocsigen and Be Sport.

Abstract:

This presentation gives an overview of the Ocsigen framework, which is used in particular to develop the Be Sport social network. Ocsigen is a set a tools to develop Web sites and applications. Amongst other things, it contains js_of_ocaml, a compiler to Javascript, and Eliom, a powerful Web framework that can be used for traditional server-side Web programming, but also to develop client-server Web and mobile distributed applications, entirely in OCaml, using multi-tier programming. We will try to show how this programming style can save a huge amount of time.

Documentation

https://watch.ocaml.org/w/qQzb94X9WM7zLif7FynPyN

[ANN] dream-html 2.1.0

• Deprecate Hx.on and introduce new Hx.on_ event handler attribute style used by htmx
• Add form [method_ `dialog] new attribute value for pure HTML modals

Along with other volunteers, we have taken notes during the meeting. They are available on the github issue.

TL;DR:

• There was a general consensus to create an “archive” repository where we can move broken, unmaintained, obsolete packages (specific characterisation still to be defined)
• There is another meeting planned on 2024-02-07 to discuss the specifics further

If this topic is important to you: Please leave comments on the github thread. Please attend the meeting.

Give us Feedback on the Improved OCaml Learning Experience!

Over the past six months, our team has been hard at work refining the OCaml learning area. Through an UX process, including surveys, user interview calls, video sessions, and in-depth analysis to identify pain points and user needs, we have created a brand-new user experience and interface.

Now, we are looking for your feedback on our work. Your perspective is invaluable as we strive to improve OCaml.org.

What we have done:

• Enhanced UX: Updated navigation based on user surveys with interviews and analysis.
• Revamped UI: A fresh interface designed with your needs in mind.
• Better Landing Page on the Learn Area: We provide a window into the documentation, from beginner to expert. This should make the content more discoverable.

Why Your Feedback Matters: Your insights are critical in shaping the future of OCaml’s learning area. We use your feedback to prioritize and implement improvements.

How to Share Your Thoughts: Explore the new design at https://ocaml.org/docs and share your feedback with us here

https://forms.gle/b2BS5NEiFaUVScJTA

Thank you for being a part of the OCaml community.

Hey folks!

I’m happy to announce the first release of middleware, a utility for composing functions which need to respond to inner calls.

See our GitHub for examples and more details: https://github.com/skolemlabs/middleware

This package was developed internally at Skolem Technologies, and we’ve decided to open-source it. More such packages are coming soon!

Hello OCaml Community!

I’m excited to share the release of validate version 1.0.0 with you all! This version is a significant milestone in my journey to provide a robust data validation library for OCaml.

In this release, I’ve introduced some exciting features. Variant support is now available, enabling more complex data types to be handled with ease. I’ve also implemented support for recursive and circular recursive types, allowing validation of nested and interconnected data structures. Here’s a quick peek at how it works:

type tree =
  | Leaf of (int[@greater_than 0])
  | Node of {
    (*Annotation can be on type or label declaration, both works*)
    left : tree; [@dive]
    right : (tree[@dive])
  } [@@deriving validate, show, eq]

let my_tree = Node { left = Leaf 1; right = Leaf 2 }
let validation_result = validate_tree my_tree

I’m also excited to announce that the validate API is now stable. While I plan to keep enhancing the library by adding new annotations for different validators over time, I assure you of consistent and reliable functionality in future updates.

If you have suggestions for new validators or features, we’d love to hear them. Your feedback is crucial in shaping the future of validate .

To dive deeper into validate 1.0.0, check out our GitHub page: https://github.com/Axot017/validate

Happy Coding!

To follow up on @spdegabrielle’s nice message: the SIGPLAN PL Software Award 2023 was formally given to the OCaml development team last week at POPL 2024 in London, and I was very pleased and honored to give the reception speech on behalf of the team. For the record, I’ll post the speech next.

It’s an honor for the whole OCaml development team to receive such a prestigious award. Some of us are here tonight: Gabriel Scherer, Damien Doligez, Florian Angeletti, Luc Maranget, David Allsopp, Stephen Dolan, Nicolas Ojeda Bär, and I’m Xavier Leroy. It’s two, almost three generations of computer scientists and developers that are being honored…

There is no denying that OCaml has been a long-term project. I released the first version of OCaml, then called Objective Caml, in 1996, almost 28 years ago. But it was already the consolidation of much earlier work, going back more than 50 years from now:

• Robin Milner’s work on “ML”, the Meta Language (scripting language) of his LCF proof assistant, which introduced the lovely type system and type inference algorithm we all know.
• Then Gérard Huet brought LCF ML back home to Rocquencourt on a magnetic tape, and liked it so much that with Guy Cousineau and their students, they developed CAML, an implementation of Milner’s ML using the CAM (the Categorical Abstract Machine) as intermediate language – hence the CAML name. And they used it as the implementation language for what was to become the Coq proof assistant.
• Then, two students of Cousineau at ENS, Damien Doligez and I, fell in love with the CAML language and developed Caml Light, a lightweight, open-source implementation of CAML suitable for teaching and popularizing the language.

So, the 1996 1.0 release of OCaml was already a consolidation of the CAML language, the memory management and virtual machine from Caml Light, my early 1990’s work on native compilation and Standard ML-style module systems, and Jérôme Vouillon’s PhD work on type systems and type inference for objects.

Since then, OCaml has continued to pick up new features arising from PL research, such as Generalized Algebraic Data Types in the late 2000’s, or very recently user-defined effects and effect handlers, making OCaml one of the first non-experimental languages to support effects. This arose from the Multicore OCaml project, along with support for shared-memory parallelism, at long last!, and a new relaxed memory model.

But that’s not the only way in which OCaml has served and continues to serve research in programming languages. If you look at previous recipients for this SIGPLAN software system award, you’ll find the Coq proof assistant, which is implemented in OCaml; the CompCert C compiler, which also uses OCaml for its non-verified parts; as well as WebAssembly, whose reference interpreter is written in OCaml. And looking at possible future recipients, you’ll find Rust, whose first compiler was written in OCaml; STAN, the probabilistic programming language whose compiler was recently rewritten in OCaml; and JSCert, the Javascript formalization that also uses OCaml for its reference interpreter.

Of course, these are not the only uses of OCaml! For something completely different: how many of you took the Eurostar train to come here? or flew an Airbus plane? Chances are that a good chunk of the software embedded in your plane or in your train was generated from SCADE block diagrams by an OCaml program, the SCADE KCG 6 compiler.

So, we’re very proud of our greater user community and all they do with OCaml, both in classic application areas for ML languages such as theorem provers, proof assistants, static analyzers, verification tools, compilers, code generators, etc.; and in more unusual areas such as systems programming.

When Damien and I were hacking Caml Light in 1990, we had no idea that 10 years later the Ensemble people at Cornell and IBM would reimplement a whole network and protocol stack for distributed applications in OCaml and get better latency than their previous C++ implementation. Then came real-time trading, web radios and audio streaming, the Irmin distributed database, Mirage unikernels that boot on a bare hypervisor, and more.

What made that possible? Not just fancy types and nice modules – even though systems programmers value type safety and modularity highly – but also basic properties of OCaml:

• a language with a simple cost model, where it’s easy to track how much time and how much space is used;
• a compiler that produces efficient code that looks like the source code, with only predictable optimizations;
• a low-latency garbage collector, usable for soft real-time applications. To us PL folks, this doesn’t sound like much. Good luck getting a paper accepted at POPL or PLDI based on these ideas! Yet, that’s crucial to open the way to many exciting applications.

Will there be other chance encounters with new application areas like this for OCaml in the future? I have no idea – and that’s what makes PL research exciting, even after all these years!

At any rate, we, the recipients of this award, are proud of the achievements of the OCaml user community, and deeply honored to see our efforts recognized by this award. Thank you!

We need some help with usability testing on the OCaml.org Learn area!

What’s it all about?

We’re conducting user testing sessions to enhance the UX/UI and content of the OCaml.org learning area. This is an opportunity for individuals with no prior knowledge of OCaml.

We will do a 1:1 video call with you where we present you with a GitHub codespace that gives you a set of programming tasks to solve. We want to learn from you solving (or trying to solve) the tasks in order to improve the documentation.

We will share relevant documents or materials before the session.

Key Criteria for Participants:

• No previous experience with OCaml
• Interested in learning OCaml
• Be available for a 1 hour video call

How to Participate: Simply express your interest through this Google Form. Spots are limited!

Obviously, most people here reading this will not meet the criteria (because of previous OCaml knowledge), however, in this case, we ask you to reach out and share this invitation with friends or acquaintances who might be willing and qualified to participate.

Here are links from many OCaml blogs aggregated at the ocaml.org blog.

• MirageOS: Designing a More Resilient Networking Stack With µTCP
• opam 101: the first steps