OCaml Weekly News

Summer and ICFP has passed since we announced the ocaml-wasm organization in July. Here we provide an update from the wasocaml and wasm_of_ocaml compiler projects since then.

I had fun reading Playing with Caml Light on DOS, published today (it is not obvious from the title).

Dear community,

Batteries is a community-maintained extended standard library for OCaml.

The latest version of batteries is now available in opam: v3.7.1.

This version mostly adds compatibility with ocaml-5.1.0 (thanks to @kit-ty-kate). Now, batteries relies on dune for compilation (thanks to Simmo Saan and Gabriel Scherer).

Many thanks to all contributors for this release!

Happy hacking, The batteries maintainers.

Here is the change log for v3.7.1:

Yours truly is delighted to announce the release of Uri 4.4.0. ocaml-uri is a library for manipulating URIs in accordance with RFC 3986. This announcement allows us to clarify a breaking change in the interpretation of IPv6. Previous versions did not interpret IPv6 in the host part of the URI - we simply escaped the special characters. This version of uri now interprets IPv6 addresses in the host part. This implies a change in the library’s behaviour which may have some impact on software using this library. This announcement clarifies this “breaking change”.

The library is available from OPAM: opam install uri.4.4.0. From what we have been able to observe, this breaking-change does not have a direct impact on the ecosystem. The release went ahead without any software being broken. However, we would like to warn you of such a change. The issues are open if you notice any unwanted behaviour in the library.

@nikochiko and I have proposed a project to develop a geometric creative coding library for OCaml. This is heavily inspired by joy – we had loads of fun hacking with it at Lambda Retreat (in Scheme) and want to pass it on to OCaml programmers, and learn a bit about creative coding in the process. Really excited to work on this. Outreachy applicants: Please don’t hesitate to get in touch with us if you’re interested to contribute. :)

Huge thanks to @pitag, @patricoferris and everyone involved, for their efforts to keep this thriving!

As promised, here is the update/summary on this round’s projects. Just like last round, the OCaml community has signed up with four super cool projects again. Here are this round’s projects:

• Implement R*-tree in OCaml An R*-tree is a data structure designed for geospatial use, particularly to be queried for geospatial objects contained in a given box. It’s super nice to see the Geospatial ecosystem for OCaml thrive. Mentors: @patricoferris , @AryanGodara
• Implement a dark mode for OCaml.org It’s a very nice idea to have a common feature request as an Outreachy project! That makes the internship very gratifying for the intern. Mentors: @SaySayo , @punchagan
• Improve the GUI experience for OCaml users Together with trying out and possibly improving different GUI libraries in OCaml, that will entail writing a “Are we GUI yet” page on ocaml.org, similar to Are we web yet?. Those pages are super important, both to understand the current OCaml ecosystem ourselves and to give an overview to newcomers. Mentors: @gpetiot, @moazzammoriani
• Develop a geometric creative coding library in OCaml Such a cool idea, @sudha ! It combines functional programming with creativity and basic geometry. The idea is to encode and draw 2-dimensional geometric shapes in a functional style. It’s inspired by Python’s joy. Mentors: @sudha, @nikochiko

Even at the small risk of being annoying: This is a good time for everyone who might possibly be interested in mentoring to start thinking about a project for next round :)

Just because I could, it doesn’t mean I should have; and yet I did write an entirely unnecessary generator for names of British pubs.

$ opam install queenshead
…
$ queenshead
The horse and goats

More details on this short blog post.

It was a good excuse to experiment with crunch as a way to embed some data files in an OCaml program. Turned out to be easy.

To celebrate this talk now being publicly available, I’ve added a chapter that was not part of the original presentation!

This Backtraces section aims to explain how backtraces are constructed for exceptions, so that exceptions can be linked to the code location that raised them. It also gives enough details about the implementation to justify the claims in Takeaway #5 about backtrace collection and raise_notrace.

It’s a bit technical, so I didn’t dive in all the details, but there’s certainly plenty to understand the technique used.

The updated slides can be found in the release page of the repository: https://github.com/fabbing/obts_exn/releases Feel free to ask me any questions if anything isn’t clear enough. :slightly_smiling_face:

Added some new features to my hobby compiler project, Pholyglot. :) Maybe nothing interesting from an OCaml perspective, it’s a pretty basic amateur home-made compiler system, nothing fancy. The weirdest aspect of it is that it outputs C-code that is also valid PHP-code, so called polyglot code (semi-readable).

Since I’m career-locked into PHP, I’m writing myself out of it with my own compiler.

Another motivation is a slight disappointment in recent languages, like Rust, which does not, according to me, adhere to the 80/20-rule - that the most common use-case should be easy, and that in 80% of cases, you don’t have to be fast, but you should be able to be fast (instead of forced to be fast). Hence the opt-out-of-GC experiment.

The current GC is just Boehm. Might be interesting to try with ref-count too. Proper tracing is out-of-scope for the project (too hard… and requires headers etc, can’t combine it with manual memory, afaik).

Main OCaml src is here: https://github.com/olleharstedt/pholyglot/tree/main/src/lib

Most recent blog post: http://olleharstedt.github.io/programming/2023/03/19/memory-polymorphic-spldoublylinkedlist-pholyglot.html

We are excited to announce the first release of asai 浅い on OPAM, along with new versions of algaeff and yuujinchou 友人帳. We also released bwd and mugen 無限 on OPAM earlier but didn’t make an announcement.

All these packages are part of our research project to dissect a typical proof assistant into composable components so that everyone can easily build a high-quality, usable prototype out of their type checker. It turns out that many components are useful for writing compilers, too. Here are our packages: (✅ means it’s on OPAM.)

• ✅ asai 浅い for compiler diagnostics.
• ✅ yuujinchou 友人帳 for namespaces and lexical scoping. See my TYPES 2022 talk for its design principles.
• bantorra for library management (still under heavy development and revisions)
• ✅ mugen 無限 for universe levels. See our POPL 2023 paper for a theoretic analysis of its design.
• kado カド for handling cofibrations in Cartesian Cubical Type Theory. This was also used for implementing unfolding control.

together with these more general-purpose packages:

• ✅ algaeff for well-known composable effects-based gadgets (e.g., state, reader, etc.)
• ✅ bwd for backward lists

We have a prototype system showing how these packages may be used together. Many packages have been used in our proof assistant cooltt, @jonsterling’s ✅ forester tool and Topos Institute’s polytt. We invite you to try out our packages the next time you want to build a proof assistant or compiler!