[Caml-list] Attn: Development Editor, Latest OCaml Weekly News

Alan Schmitt
2025-12-30T09:33:26Z

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Hello

Here is the latest OCaml Weekly News, for the week of December 23 to 30,
2025.

Table of Contents
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Release of pacomb 1.4
Raven Dev Meetings
Frontmatter_extractor.0.1
QCheck 0.90: The Great Renaming
Other OCaml News
Old CWN

Release of pacomb 1.4
═════════════════════

Archive: <https://discuss.ocaml.org/t/release-of-pacomb-1-4/17630/1>

Christophe Raffalli announced
─────────────────────────────

Dear camlers, I am pleased to announce the release of pacomb 1.4.

Pacomb is a library + ppx to write grammars. It support: self
extensible grammars, ambiguous grammars (with merge), late rejection
of rule via raising exception from action code, priority and
others. Is it relatively fast because it is compiled to efficient
combinators. More details are available in the [git page] and the
[documentation].

As teaser, the usual calculator example:

┌────
│ (* The three levels of priorities *)
│ type p = Atom | Prod | Sum
│
│ let%parser rec
│ (* This includes each priority level in the next one *)
│ expr p = Atom < Prod < Sum
│ (* all other rules are selected by their priority level *)
│ ; (p=Atom) (x::FLOAT) => x
│ ; (p=Atom) '(' (e::expr Sum) ')' => e
│ ; (p=Prod) (x::expr Prod) '*' (y::expr Atom) => x*.y
│ ; (p=Prod) (x::expr Prod) '/' (y::expr Atom) => x/.y
│ ; (p=Sum ) (x::expr Sum ) '+' (y::expr Prod) => x+.y
│ ; (p=Sum ) (x::expr Sum ) '-' (y::expr Prod) => x-.y
└────

Here is a list of the main changes from 1.3:

• Add a "not charset combinator" for regexp `\[!...\]', it is distinct
from `\[^...\]' as it parses nothing.
• File was not closed by Grammar.parse_file in case of parse error
• New Grammar.set_debug_merge to allow debugging ambiguous grammars
(report by Matthieu Lemerre)
• Compatibility with latest ocaml and ppxlib
• Travis action to check compilation
• Various documentation fix

Possible roadmap for future version:

• 1.5 : integrate a lexical entry for ocaml code with call back for
specific {xxx| … |xxx}. This is code existing in simple_httpd’s
chaml parser (equivalent to php but in cocaml), that I wish to
integrate in pacomb.
• 2.0 : rewrite the combinators with algebraic effects. The semantics
will be much better than the current implementation using
references.

Cheers,

Christophe

[git page] <https://github.com/craff/pacomb>

[documentation] <https://raffalli.eu/pacomb/pacomb>

Raven Dev Meetings
══════════════════

Archive: <https://discuss.ocaml.org/t/ann-raven-dev-meetings/17596/3>

Continuing this thread, Thibaut Mattio announced
────────────────────────────────────────────────

We'll be skipping the dev meeting on the 29th for the holidays, so the
next Raven dev meeting will be on *Monday, January 5, 2026, at 10:00
AM CET (2:30 PM IST)*.

Link: <https://meet.google.com/giw-bsdy-sjf>

Frontmatter_extractor.0.1
═════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-frontmatter-extractor-0-1/17634/1>

Mikhail announced
─────────────────

Hi there! :waving_hand:

I am writing again about my new library, which I must create, because
there is simply no alternative available.

[Frontmatter_extractor] is a small library that extracts the front
matter section of a text file. It is commonly used in static content
generators (blog engines, etc), such as those that convert Markdown
files into HTML or other formats.

*Example of usage*

┌────
│ let some_text = {|
│ ---
│ title: "My First Blog Post"
│ date: 2025-12-1
│ ---
│
│ Hello! It's just some text...
│ |};;
└────

Extract frontmatter as plain text.
┌────
│ # Frontmatter_extractor.of_string some_text;;
│
│ - : Frontmatter_extractor.extracted =
│ {Frontmatter_extractor.matter =
│ Some "\ntitle: \"My First Blog Post\"\ndate: 2025-12-1\n";
│ body = "\n\nHello! It's just some text...\n"}
└────

Extract the front matter as parsed YAML values. The yaml library needs
to be installed.

┌────
│ # Frontmatter_extractor_yaml.of_string_exn some_text;;
│
│ - : Frontmatter_extractor_yaml.extracted =
│ {Frontmatter_extractor_yaml.attrs =
│ Some
│ (`O [("title", `String "My First Blog Post"); ("date", `String "2025-12-1")]);
│ body = "\n\nHello! It's just some text...\n"}
└────

*P.S.*

It's not fully tested, but it's usable as a first version.

[Frontmatter_extractor]
<https://github.com/dx3mod/frontmatter_extractor>

QCheck 0.90: The Great Renaming
═══════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-qcheck-0-90-the-great-renaming/17613/2>

Continuing this thread, Jan Midtgaard announced
───────────────────────────────────────────────

Version 0.91 of the QCheck packages is now available:

<https://github.com/c-cube/qcheck/releases/tag/v0.91>

This release adds [ocamlmig] annotations to most of the renamed
combinators, in an attempt to ease migration for users. From my
experiments so far, these work pretty well and allowed me to port
[multicoretests] with little effort. Thanks to @raphael-proust for the
suggestion and @v-gb for a nice tool! :folded_hands:

Happy migration and testing! :smiley:

[ocamlmig] <https://github.com/v-gb/ocamlmig>

[multicoretests] <https://github.com/ocaml-multicore/multicoretests>

Other OCaml News
════════════════

>From the ocaml.org blog
───────────────────────

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

• [AoAH Day 25: Claude OCaml Marketplace for all your festive coding
needs]
• [AoAH Day 24: Tuatara, an evolving Atom aggregator that mutates]
• [AoAH Day 23: Unpac unifies git branching with package management]
• [AoAH Day 22: Assembling monorepos for agentic OCaml development]
• [AoAH Day 21: Complete dynamic HTML5 validation in OCaml and the
browser]

[the ocaml.org blog] <https://ocaml.org/blog/>

[AoAH Day 25: Claude OCaml Marketplace for all your festive coding
needs] <https://anil.recoil.org/notes/aoah-2025-25>

[AoAH Day 24: Tuatara, an evolving Atom aggregator that mutates]
<https://anil.recoil.org/notes/aoah-2025-24>

[AoAH Day 23: Unpac unifies git branching with package management]
<https://anil.recoil.org/notes/aoah-2025-23>

[AoAH Day 22: Assembling monorepos for agentic OCaml development]
<https://anil.recoil.org/notes/aoah-2025-22>

[AoAH Day 21: Complete dynamic HTML5 validation in OCaml and the
browser] <https://anil.recoil.org/notes/aoah-2025-21>

Old CWN
═══════

If you happen to miss a CWN, you can [send me a message] and I'll mail
it to you, or go take a look at [the archive] or the [RSS feed of the
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[Alan Schmitt]

[send me a message] <mailto:alan.schmitt@polytechnique.org>

[the archive] <https://alan.petitepomme.net/cwn/>

[RSS feed of the archives] <https://alan.petitepomme.net/cwn/cwn.rss>

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[Alan Schmitt] <https://alan.petitepomme.net/>

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