OCaml Weekly News

Hello

Here is the latest OCaml Weekly News, for the week of October 01 to 08, 202= 4.

Releases of fpath-sexplib0, fpath-base, loc, file-rewriter, se= xps-rewriter and provider

Archive: https://d= iscuss.ocaml.org/t/releases-of-fpath-sexplib0-fpath-base-loc-file-rewriter-= sexps-rewriter-and-provider/15364/1

Mathieu Barbin announced

I wanted to announce the initial release of 6 utility packages to the opam-= repository. They are dependencies to some other ongoing projects I have, pe= rhaps some will find them useful.

These are very early days for this software. Please feel welcome to opening= issues or discussions tickets if you are inclined.

Thank you @mseri , @avsm & @shonfeder for your help in making these lib= raries available!

Below you'll find short descriptions with links to the packages home pages.= Thank you!

Fpath_sexplib0 only d= epends on fpath and sexplib0. It defines a single= module, Fpath_sexplib0, which is designed to be opened to sha= dow the Fpath module to add small helpers and a sexp_of<= /code> serializer to it. The package also introduces three new modules to t= he scope: Fpart, Absolute_path and Relative= _path to increase type-safety when manipulating paths that are known= to be relative or absolute.




Fpath_base further ex=
tends fpath-sexplib0 and adds a dependency on base. It is desi=
gned to be compatible with Base-style containers such as Map, =
Set, Hashtbl, Hash_set.



Loc is an OCaml library to m=
anipulate code locations, which are ranges of lexing positions from a parse=
d file.



File_rewriter is a=
n OCaml library for applying small rewrites to tweak or refactor your files=
. It provides a convenient interface to apply surgical textual substitution=
s on the fly, while navigating the contents of a file through an abstract r=
epresentation containing code locations.



Sexps_rewriter is =
a specialized version of the file-rewriter library dedicated t=
o rewriting sexp files, such as dune config files.

Provider is an OCaml li= brary for creating Traits and Interfaces. It allows you to define the funct= ionality needed by a library without committing to a specific implementatio= n - in essence : dynamic dispatch. Provider is a pattern featured in the Eio project (Eio.Resource). I wanted to make it reu= sable in other projects - in particular I am currently using it as the para= metrization story of vcs. This package had already been availa= ble for a little while already but was still unannounced.

Build a project without Stdlib

Archive: https://discuss.ocaml.org/t/build-a-project-without-stdlib/153= 74/1

Mikhail announced

I decided to experiment with compiling a project without the standard libra= ry. Why? I don't know. But I could save ~50K. Just sharing my note about it.

You can find an example in my repository.

I found the -nostdlib and -nopervasives (undocume= nted) flags and after a lot of trying I was able to do what I wanted. It do= esn't disable absolutely everything (lists and other types like optio= n are available).

(flags
  :standard
  -nostdlib
  -nopervasives
  ; add runtime
  -cclib
  -lasmrun
  -ccopt
  "-L %{ocaml_where}"
  -ccopt
  "-lm -ldl")

(* stdlib.=
ml *)
external print_endline : string -> unit =3D "caml_print_endline" [@@noalloc]

(* main.ml *)
open Stdlib
let () =3D print_=
endline "hello from my stdlib"

Hello World program:

	with Stdlib	without Stdlib
size	349K	302K

obatcher: Framework for building efficient concurrent services=

Archive: https://discuss.ocaml.org/t= /ann-obatcher-framework-for-building-efficient-concurrent-services/15384/1<= /a>

Lee Koon Wen announced

Hot on the heels of the paper "Concurrent Data Structures Made= Easy" appearing at OOPSLA 2024= on the 24th October, I'm pleased to announce release of obatcher - = a picos compatible library for implementin= g efficient batched services in OCaml.

obatcher proposes a new way to approach the design and implem= entation of concurrent services. It's key benefits are:

Incremental optimization and parallelism of services
Easy to control and reason about concurrency
Retains atomic-style interface with your services while batching happen= s implicitly
Thread-safety for cheap!

Available on opam today, install with

opam install obatcher

For more details, check out the source and README on GitHub: obatcher.

Feedback, contributions, and discussions are welcome!

DBLP query program and library

Archive: https://discuss.ocaml.org/t/ann-dblp-query-program-and-lib= rary/15385/1

Samuel Mimram announced

I am happy to announce the first realease of ocaml-dblp, which provides both a program and a lib= rary to query the DBLP bibliographic data= base. In practice, it is mostly useful for retrieving bibtex entries with c= ommands such as

dblp bibtex girard locus solum

which will spit out

@article{DBLP:journals/mscs/Girard01,
  author       =3D {Jean{-}Yves Gira=
rd},
  title        =3D {Locus Solum: Fro=
m the rules of logic to the logic of rules},
  journal      =3D {Math. Struct. Co=
mput. Sci.},
  volume       =3D {11},
  number       =3D {3},
  pages        =3D {301--506},
  year         =3D {2001},
  url          =3D {https://doi.org/10.1017/S096012=
950100336X},
  doi          =3D {10.1017/S096012950100336X},
  timestamp    =3D {Wed, 01 Apr 2020=
 08:48:47 +0200},
  biburl       =3D {https://dblp.org=
/rec/journals/mscs/Girard01.bib},
  bibsource    =3D {dblp computer sc=
ience bibliography, https://dblp.org}
}

(or, even better, use dblp bib to directly add this at the end= of the .bib file in the current directory).

It might still need some polishing, feel free to reach out if you encounter= some problems.

cudajit: Bindings to the `cuda` and `nvrtc libraries`




Archive: https://discuss.ocaml.org/t/ann-cudajit-=
bindings-to-the-cuda-and-nvrtc-libraries/15010/2




Lukasz Stafiniak announced


cudajit 0.5.0 is now available in the opam repository. It's organized into =
modules, and it adds support for CUDA events.







YOCaml, a framework for static site generator


Archive: https://discuss.ocaml.org/t/ann-yocaml-a-fra=
mework-for-static-site-generator/15393/1




Xavier Van de Woestyne announced


:wave: Hello everyone! We, the YOCaml development team, are very pleased to=
 announce the release of version 2, freshly merged into opam-repository :champagne:!=20



YOCaml is a framework for describing static site generators (a very =
small applicative build-system whose API is tailor-made for creating web pa=
ges ) and its internal model is very similar to Hakyll (the 3th version), another Haskell framework. (a p=
resentation was given to the OCaml user Group in Paris and you can find the=
 video, in French, here).




Changes with 1.0.0


Historically, YOCaml was written very, very quickly to give examples of sli=
ghtly exotic uses of the library Preface. Due to its experimental nature, the API was a bit laborious, =
but we did find some users! We took advantage of the redesign to stop relyi=
ng on Preface (and yes, YOCaml was already more widely used than Preface), =
move to OCaml 5.x and take advantage of user-defi=
ned-effects and support dynamic dependencies. In other words, YOCaml=
 2.0.0 is not at all compatible with version 1…





Plugins and runtimes


The aim of YOCaml is to be very generic and to allow users to bring their o=
wn dependencies, but we've taken the opportunity to release it with several=
 plugins and runtimes so that it can be used directly.




Runtimes



A Runtime is an =E2=80=98execution context=E2=80=99 and generally exposes t=
he primitive used to execute a YOCaml program. YOCaml 2 is bundled with 3 R=
untimes:



Yocaml_unix: the default runtime, whose preview server is implem=
ented on top of the brand new httpcats!

Yocaml_eio: a runtime iso to Unix but based on eio and whose preview server is descr=
ibed by cohttp_eio.<=
/li>

Yocaml_git: a parameterised runtime for generating a site direct=
ly in a git repository, which can be served, for example, by a Mirage (unipi), very well documented in this excellent article by @dinosaure!




Plugins



Yocaml_cmarkit provides a convenient API (via YOCaml) for conver=
ting Markdown files to HTML via the excellent cmarkit library.

Yocaml_omd provides a convenient API (via YOCaml) for converting=
 Markdown files to HTML via the excellent OMD library (but we recommend yocaml_cmarkit).

yocaml_yaml provides a convenient API (via YOCaml) for reading Y=
aml via the excellent library ocaml-yaml

yocaml_otoml provides a convenient API (for YOCaml) for reading =
TOML via the excellent library Otoml

yocaml_mustache provides a convenient API (via YOCaml) for using=
 Mustache as a template languag=
e via the excellent library ocaml-mustache

yocaml_jingoo provides a convenient API (via YOCaml) for using <=
a href=3D"http://tategakibunko.github.io/jingoo/">Jingoo as a template =
language via the excellent library jingoo

yocaml_syndication that gives tool to generate feeds ([Atom](https://en.wikip=
edia.org/wiki/Atom_(web_standard)), RSS 1 and 2 and OPML). The=
 library is inspired by Syndi=
c but does not depend directly on it.







A final word


YOCaml 2 was mainly written by xhtm=
lboi, helped by gr-im, mspwn and dinosaure with occasional support from maiste. It has already been used experimentally in a nu=
mber of small projects:



Ring.muhokama a very small we=
bring - sources
Maiste.fr - sources
gr-im.github.io - sources



You will also find extensively documented examples in the examples directory.



To conclude, we find (not very objectively) that YOCaml is a lot of fun to =
use, and it's very cool to make your site using as much OCaml as possible.=
=20



Happy Hacking!



Yocaml on OPAM
Dev repository










oepub 0.1.0 : A library to parse epub files


Archive: https://discuss.ocaml.org/t/ann-oepub-0-1-0-a-l=
ibrary-to-parse-epub-files/15394/1




EruEri announced


I humbly announce oepub a small library to parse epub files and to some ext=
end create a list of chapters from the epub archive.



You can find the repository at Codeberg - Oepub









ppx_deriving_router =E2=80=94 type safe routing for Dream and =
Melange


Archive: https://discuss.ocaml.org/t/a=
nn-ppx-deriving-router-type-safe-routing-for-dream-and-melange/15401/1




Andrey Popp announced


It's my pleasure to announce a new ppx for deriving Dream routers based on variant type declarations,=
 ppx_deriving=
_router.



A small example. First we define routes (the signature showcases the genera=
ted code):


module Pages : sig
  ...

  val href : t -> string
  (** generate URL from=
 the route *)

  val http_method : t -> [ `DELETE | `GET | `POST | `PUT ]
  (** HTTP method for t=
he route *)

  val handle : (t -> Dream.handler) -> Dream.handler
  (** create a route ha=
ndler *)
end =3D struct
  open Ppx_deriving_router_runtime.Primitives

  type t =3D
    | Home [@GET "/"]
    | About
    | Hello of { name : st=
ring; repeat : int option } [@GET "/hello/:name"]
    [@@deriving router]
end




Then we describe how we handle each route:


let handle =3D
  Pages.handle (fun r=
oute _req ->
      match route=
 with
      | Home -> Dream.respond "Home page!"
      | About -> Dream.respond "About page!"
      | Hello { name; repeat } ->
          let name =3D
            match=
 repeat with
            | So=
me repeat ->
                List.init repeat (fun _ -> name) |>=
 String.concat ", "
            | No=
ne -> name
          in
          Dream.respond (Printf.sprintf =
"Hello, %s" name))

let () =3D Dream.run =
~interface:"127.0.0.1" ~port:8080 handle




Using generated Pages.href function we can generate URLs for r=
outes:


let () =3D
  assert (Pages.href Home =3D =
"/");
  assert (Pages.href About =3D "/about");
  assert (Pages.href (Hello { name =3D "world"; repeat =3D None }) =3D "/he=
llo/world");
  assert (Pages.href (Hello { name =3D "world"; repeat =3D Some 3 }) =3D "/=
hello/world?repeat=3D3")




The URL matching is done by routes library.



There's also support for routes that track their response ty=
pes and the ppx automatically derives JSON encoders and decoders for th=
em (by using melange-json.ppx).



On top of that a separate ppx is provided for Melange which allows to construct type safe HTTP clients (=
route defintions are shared between server and client).



Happy hacking!









Mica, a PPX that automates differential testing for OCaml modu=
les


Archive: https://discuss.ocaml.or=
g/t/ann-mica-a-ppx-that-automates-differential-testing-for-ocaml-modules/15=
406/1




Ernest Ng announced


I'm delighted to announce the initial release of Mica, a PPX deriver that automates differential test=
ing for a pair of OCaml modules implementing the same signature. Users anno=
tate module signatures with the directive [@@deriving mica], a=
nd at compile-time, Mica derives specialized property-based testing (PBT) code that chec=
ks if two modules implementing the signature are observationally equivalent=
. (Under the hood, Mica uses Jane Street's Core.Quickcheck PBT library.)



Mica was presented at the OCaml Workshop '24 (paper) and the ICFP '23 Student Research Competition (<=
a href=3D"https://ngernest.github.io/pdfs/mica_icfp23src_poster.pdf">poster=
).=20



Note: Mica is currently a research tool and should not be used in pr=
oduction code, although contributions are very welcome!



Mica is available on Opam:=20

opam update=20
opam install ppx_mica


(OCaml 5.1 or newer is required.)



Docs are available here, and a simple web app demo-ing Mica is available here.









Simplified Android cross-compiler with DkML


Archive: https://discuss.ocaml.org/t/ann-simplified-an=
droid-cross-compiler-with-dkml/15407/1




jbeckford announced


DkML has had a cross-compiler for years, but I have cleaned it up so that i=
t is much easier to use for Android developers. It now works with a regu=
lar opam installation in a custom repository. Also included are patches=
 to the OCaml compiler to work with Android NDK 21+ (currently Google is at=
 NDK 27).



Try it out if you do Android development … just copy-and-paste the i=
nstructions below … but please read the notes and cautions below. An=
d if you are still interested in Android development, tell me so I can deci=
de if I'll merge the packages into the regular opam repository.



Trimmed slightly from the dkml-compiler Quick Start:



Docker container is used below for Windows and macOS users, and because=
 it is easy to get the Android NDK from CircleCI.
Apple Silicon does not support 32-bit. The net effect is that Apple Sil=
icon users cannot cross-compile android_arm32v7a.


$ docker run -it --rm cimg/android:2024.10.1-ndk

# Install opam if you don't have it
~/project$ sudo apt-get update && sudo apt-get install build-essent=
ial curl git patch rsync unzip -y
~/project$ echo /usr/local/bin | sudo bash -c "sh <(curl -fsSL https://o=
pam.ocaml.org/install.sh) --version 2.2.1"

# Initialize opam if you haven't already. No sandboxing is needed in contai=
ners.
~/project$ opam init --cli=3D2.1 --no-setup --bare --disable-sandboxing

# Two Android options to set. ANDROID_PLATFORM is the minimum API level ("t=
argetSdkVersion" in the Android manifest)
~/project$ opam var --cli=3D2.1 --global ANDROID_NDK=3D/home/circleci/andro=
id-sdk/ndk/27.1.12297006
~/project$ opam var --cli=3D2.1 --global ANDROID_PLATFORM=3Dandroid-34

# PICK ONE: Android arm64-v8a switch
~/project$ opam switch create android34-ndk27-arm64-v8a --cli=3D2.1 \
  --packages dkml-base-compiler,dkml-host-abi-linux_x86_64,dkml-target-abi-=
android_arm64v8a,ocamlfind,conf-dkml-cross-toolchain \
  --repos default,diskuv-4d79e732=3Dgit+https://github.com/diskuv/diskuv-op=
am-repository.git#4d79e732

# PICK ONE: Android armeabi-v7a switch. You will need a 32-bit C/C++ compil=
er.
~/project$ sudo apt-get install gcc-multilib g++-multilib -y
~/project$ opam switch create android34-ndk27-armeabi-v7a --cli=3D2.1 \
  --packages dkml-base-compiler,dkml-host-abi-linux_x86,dkml-target-abi-and=
roid_arm32v7a,ocamlfind,conf-dkml-cross-toolchain \
  --repos default,diskuv-4d79e732=3Dgit+https://github.com/diskuv/diskuv-op=
am-repository.git#4d79e732

# PICK ONE: Android x86_64 switch
~/project$ opam switch create android34-ndk27-x86_64 --cli=3D2.1 \
  --packages dkml-base-compiler,dkml-host-abi-linux_x86_64,dkml-target-abi-=
android_x86_64,ocamlfind,conf-dkml-cross-toolchain \
  --repos default,diskuv-4d79e732=3Dgit+https://github.com/diskuv/diskuv-op=
am-repository.git#4d79e732

# THEN: Get and cross-compile your source code. Here we use Dune and assume=
 'android34-ndk27-arm64-v8a'
~/project$ opam install --cli=3D2.1 --switch android34-ndk27-arm64-v8a dune
~/project$ git clone https://github.com/avsm/hello-world-action-ocaml hello
~/project$ cd hello
~/project/hello$ opam exec --cli=3D2.1 --switch android34-ndk27-arm64-v8a -=
- \
  dune build -x android_arm64v8a world.exe

~/project/hello$ file _build/default*/world.exe
_build/default.android_arm64v8a/world.exe: ELF 64-bit LSB pie executable, A=
RM aarch64, version 1 (SYSV), dynamically linked, interpreter /system/bin/l=
inker64, with debug_info, not stripped
_build/default/world.exe:                  ELF 64-bit LSB pie executable, x=
86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x8=
6-64.so.2, BuildID[sha1]=3D1731ad9ce0fdeff69df28af0b1217e843eabe26e, for GN=
U/Linux 3.2.0, with debug_info, not stripped

# You can also directly use the ocamlfind -toolchain

~/project$ opam exec --cli=3D2.1 --switch android34-ndk27-arm64-v8a -- \
  ocamlfind ocamlc -config-var native_c_compiler
gcc -O2 -fno-strict-aliasing -fwrapv -pthread -fPIC  -D_FILE_OFFSET_BITS=3D=
64

~/project$ opam exec --cli=3D2.1 --switch android34-ndk27-arm64-v8a -- \
  ocamlfind -toolchain android_arm64v8a ocamlc -config-var native_c_compiler
/home/circleci/android-sdk/ndk/27.1.12297006/toolchains/llvm/prebuilt/linux=
-x86_64/bin/aarch64-linux-android34-clang -O2 -fno-strict-aliasing -fwrapv =
-pthread -fPIC  -D_FILE_OFFSET_BITS=3D64



DkML supports three out of the four supported Android ABIs. The three ABIs =
(all but x86) were chosen based on statistics for a large =
game on Aug 29, 2023:












Arch
Percent




arm64-v8a
68.66



armeabi-v7a
30.38



x86_64
0.71



x86
0.26





and also Google's recommendation:



Note: While 64-bit-only devices will grow in popularity with phones =
joining Android Auto in this group, 32-bit-only devices will continue to be=
 important for Android Go, Android TV, and Android Wear. Please continue su=
pporting 32-bit ABIs; Google Play will continue serving 32-bit apps to 32-b=
it-only devices.



Finally, a word of CAUTION. The Android cross-compiler can never<=
/i> use OCaml 5+ because OCaml 5 will never brin=
g back the 32-bit instruction set. That means if you don't want to drop=
 a large percent of your users or drop new Android categories over the next=
 five (?) years, you will have a critical dependency on DkML.









Other OCaml News



From the ocaml.org blog


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



Developer education at Jane Street
Solving Puzzles in Product=
ion with Liora Friedberg
MetAcsl v0.7 fo=
r Frama-C 29.0~ Copper
Introducing the Dune Develo=
per Preview: A New Era for OCaml Development
Unlock your Team=E2=80=99s Potential with Expert Traini=
ng in OCaml, Cybersecurity Fundamentals, Functional Programming, and More

Alt-Ergo 2.6 is Out!
Happy eye=
balls?!









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

OCaml Weekly News

Table of Contents

Releases of fpath-sexplib0, fpath-base, loc, file-rewriter, se= xps-rewriter and provider

Mathieu Barbin announced

Build a project without Stdlib

Mikhail announced

obatcher: Framework for building efficient concurrent services=

Lee Koon Wen announced

DBLP query program and library

Samuel Mimram announced

cudajit: Bindings to the cuda and nvrtc libraries

Lukasz Stafiniak announced

YOCaml, a framework for static site generator

Xavier Van de Woestyne announced

Changes with 1.0.0

Plugins and runtimes

A final word

oepub 0.1.0 : A library to parse epub files

EruEri announced

ppx_deriving_router =E2=80=94 type safe routing for Dream and = Melange

Andrey Popp announced

Mica, a PPX that automates differential testing for OCaml modu= les

Ernest Ng announced

Simplified Android cross-compiler with DkML

jbeckford announced

Other OCaml News

From the ocaml.org blog

Old CWN

cudajit: Bindings to the `cuda` and `nvrtc libraries`