OCaml Weekly News

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Here is the latest OCaml Weekly News, for the week of August 13 to 20, 2024.

MlFront - A Java-like package system for OCaml

Archive: https://discuss.ocaml.org/t/ann-mlfront-a-ja= va-like-package-system-for-ocaml/15072/8

jbeckford announced

There is now a new library MlFront_Top with a build tool mlfront-top that will generate self-contained OCaml toplevel script= files with parallelism based on @c-cube's moonpool library:

.
=E2=94=9C=E2=94=80=E2=94=80 AcmeWidgets_Std/
=E2=94=82   =E2=94=9C=E2=94=80=E2=94=80 JobsA1.ml
=E2=94=82   =E2=94=94=E2=94=80=E2=94=80 JobsA2.ml
=E2=94=94=E2=94=80=E2=94=80 BobBuilder_Std/
    =E2=94=94=E2=94=80=E2=94=80 JobsB.ml

$ mlfront-top -o buildscript.ml

$ ocaml buildscript.ml -j 2 -native
  legend: -> start | <- finish
     directory create: target/
     file create: target/AcmeWidgets_Std.ml
     link create: AcmeWidgets_Std/JobsA1.ml -> target/AcmeWidgets_Std__J=
obsA1.ml
     link create: AcmeWidgets_Std/JobsA2.ml -> target/AcmeWidgets_Std__J=
obsA2.ml
     link create: BobBuilder_Std/JobsB.ml -> target/BobBuilder_Std__Jobs=
B.ml
  -> compile: AcmeWidgets_Std.JobsA1
  -> compile: AcmeWidgets_Std.JobsA2
  <- compile: AcmeWidgets_Std.JobsA1
  <- compile: AcmeWidgets_Std.JobsA2
  -> compile: AcmeWidgets_Std
  <- compile: AcmeWidgets_Std
  -> compile: BobBuilder_Std.JobsB
  <- compile: BobBuilder_Std.JobsB
  -> executable create: BobBuilder_Std.JobsB
  <- executable create: BobBuilder_Std.JobsB
  done.

$ target/BobBuilder_Std.JobsB
I am an A1!
I am an A2!
I am a B!

It requires the ocaml binary and ocamlc or = ocamlopt. The complete example is at http= s://gitlab.com/dkml/build-tools/MlFront/-/blob/0.4.0-6/tests/MlFront_Top/jo= bs.t/run.t.

Rpmfile library v0.3.0 with new Eio-based reader

Archive: https://discuss.ocaml.org/t/rpmfile-library-= v0-3-0-with-new-eio-based-reader/15149/1

Mikhail announced

Today I want to tell you about new version of Rpmfile library. Rpmfile is a library for reading meta= data from RPM= packages. Originally Rpmfile's parser (reader) used Angstrom for parsing. And in the ne= w release added new modern Eio-based reader.=20

Globally, the project is now split into four packages: rpmfile= , which contains signatures and implementation-independent functions, rpmfile-unix with the original Angstrom parser, and rpmfile-e= io (with rpmfile-cli) written using Eio.

My experience porting to Eio

Eio is a fantastic effect-based I/O library for a more modern age in multic= ore OCaml. I think it takes the best ideas from the ecosystem. So built-in = Buf_read and Buf_write modules implement ideas fr= om Angstrom and Faraday libraries. Almost API one-to-one, allowing porting = via copy-paste.=20

But, of course, not everything is so perfect. Unlike the Angstrom.par= se_ function, the Buf_read.parse function thinks I want= to read a whole stream to end of input.

A snippet of the source code:

let parse ?initial_size ~m=
ax_size p flow =3D
  let buf =3D of_flow flow ?initial_size ~max_size in
  format_errors (p <* end_of_input) buf
  (*               ^^^^^^^^^^^^^^^     =
      
                    0_0=
 nice (not)     =
   *)

So I had to rewrite this function myself in a form similar to Angstro= m.Consume.Prefix.

Is it a signed or unsigned integer?

BE.uint16 and other similar functions are signed int ev= en though they have the prefix u in the name for some reason.
And a few other differences
- Angstrom.advance is skip
- Angstrom.pos is consumed_bytes

P.S.

Thanks for your attention!

GitHub - meta-introspector/ocaml-libppx-import-yojson-introspe= ctor: Using libppx, ppx_import, reflect over ast using

Archive: https://discuss.ocaml.org/t/github-meta-introspector-oca= ml-libppx-import-yojson-introspector-using-libppx-ppx-import-reflect-over-a= st-using/15151/1

Jim Dupont announced

Here is a working first version (with warts) of a ppxlib to yojson converte= r, am still testing it but the hello world is working, I have tried multiple t= imes to get this to work,=20 and finally settled on the import route to override the type system. code here: https://github.com/meta-introspector/ocaml-libppx-import-yojs= on-introspector

example snippet

{
  "pexp_desc": [
    "Pexp_constant",
    [
      "Pconst_string",
      "Hello, World!"
    ]
  ]
}

Dune Developer Preview Updates

Archive: https://discuss.ocaml.org/t/ann-dune-developer-preview-upd= ates/15160/1

ostera announced

Just wanted to share some of the work the Dune has been up to lately re: th= e Developer Preview we announced here :) =E2=80=93 we'll be= using this thread to share more updates as things go.

As always, we hold our Dune Developer meetings in public and you're more th= an welcome to subscribe to our public Calendar (Google, iCal)

Getting ready for the Public Beta

As we prepare for the public beta, we're ramping up the DX interviews and e= nsuring the first few users will have a fun, productive experience with the= developer preview.

:inbox_tray: If you signed up for the Dev Preview back in May, check your i= nbox for a link and instructions to schedule your DX interview with us.

Here's a sample video (Mastodon or X) where you can see me building the Riot project on a mach= ine that does not have OCaml installed. It is pretty neat!

Seriously, big shoutout to the Dune team at Tarides[0] who have been doing = a phenomenal job :clap: :sparkles: :camel:=20

So here's what getting started with OCaml looks like today with the Dune De= veloper Preview as of today (August 19 2024):

get dune from our binary distribution =E2=80=93 we'll soon= make this public!
run dune pkg lock in your favorite project
run dune build

That's it. No need to install anything else, Dune will see that lock file, = fetch, and build all necessary dependencies.

:world_map: These are some strong step towards the OCaml Platform vision for 2026, that we ar= e actively working towards. If you have any thoughts or feedback please let= me know!

There are more improvements coming that will help remove friction to get st= arted and creating a delightful experience. Both of these things we strongl= y believe will help onboard new users to the OCaml world.

Here's a few in the works:

Various DX improvements =E2=80=93 from new outputs to simplified= workflows, we want to make using Dune just delightful.
Bundled support for dev tools (ocalmformat, odoc, lsp) =E2=80=93= the default toolset will be available without any extra steps! just call <= code>dune fmt, and it works. No need to manually install anything el= se.
Automatic dependency locking =E2=80=93 when building, and even o= n watch mode, Dune will lock your dependencies by default and keep the lock= up to date.
Cross-project Caching =E2=80=93 by default we'll enabled a local= Dune cache that across the system, so you never rebuild the same dependenc= y even across projects.
Signed binaries with certificates of origin =E2=80=93 we care de= eply about security and want to make sure that any binary we ship will be e= asily verified and tracked back to its sources.

Stay tuned! :wave:=20

PS: here's a longer video (Mastodon, X) showing you the setup for OCaml from zero, creating a = new project, and adding a dependency, all within ~5 minutes

[0] @emillon @Leonidas @gridbugs @tmattio. Ambre Shumay, Alpha Diallo, Etie= nne Marais

Ppxlib dev meetings

Archive: https://discuss.ocaml.org/t/ppxlib-dev-meetings/12441/29

Nathan Rebours announced

This month's meeting is scheduled for tomorrow, [date=3D2024-08-20 time=3D1= 7:00:00 timezone=3D"Europe/London"]!

The meeting agenda thus far is to discuss the following:

5.2 Bump Progess
- Auto-generate AST pattern code and labelled arguments (e.g. value= _binding ~constraint_:none but no positional argument?)
- Ast_helper.Exp.function_ deprecation
- opa= m-repository overlay for 5.2 AST bump
Issues in migrations
- Bumping the AST has uncovered issues in migrating code up and down the = internal ppxlib ASTs – would be good to discuss this and also how to= mitigate this going forward.
Documentation
- Great user feedback from Ppxlib: Getting the original definition of typ_constr like type_declaration from core_ty= pe of ptyp_constr which we should take onboard and = work into https:= //github.com/ocaml-ppx/ppxlib/issues/324
Some carry over items from last month
- In general what is the medium term goals for ppxlib? Mostly maintenance= and bumping the AST/keeping up with compiler releases?

The meeting will be hosted on google meet here: https://meet.google.com/yxw-ejnu-cju

Everyone is very welcome to join! :camel:

Pragmatic Category Theory: Part 2 published!

Archive: https://discuss.ocaml.org/t/new-part-prag= matic-category-theory-part-2-published/15056/6

Dmitrii Kovanikov announced

I just published the second part of my series, so I u= pdated the topic.

Let me know when notifications become too noisy :slight_smile:

Dune dev meeting on 2024-08-21, 10am CEST

Archive: https://discuss.ocaml.org/t/ann-dune-dev-meeting= -on-2024-08-21-10am-cest/15166/1

Steve Sherratt announced

Hi! The next public dune dev meeting will be held on 2024-08-21, 10am CEST.= Please feel free to let me know any topics you'd like us to discuss and I'= ll update the meeting notes. The zoom link for the meeting is: https://us06web.zoom.us/j/85096877776?pwd=3DcWNhU1dHQ1ZNSjZuOUZCQ0h2by9Udz= 09

Other OCaml News

From the ocaml.org blog

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

The new T= ar release, a retrospective

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 loo= k at the archive or the <= a href=3D"https://alan.petitepomme.net/cwn/cwn.rss">RSS feed of the archive= s.

If you also wish to receive it every week by mail, you may subscribe to the= caml-list.

Alan Schmitt