OCaml Weekly News

You got me curious: what’s the reason for using a first-class module here instead of a record or an object?

Of course!

• compared to records, I find first-class modules to be a lot more convenient for this use case. I still use records for data, but a record-of-function is often less convenient. For example, modules allow you to use include, they directly handle down-casting as a way to hide internal state (whereas for modules you need to close over values created before the record); module types are structural, so I don't need to worry about disambiguation, whereas records need more care there. In terms of performance both seem exactly the same, from my toy benchmarks.
• compared to objects, first-class modules are a bit less convenient (no runtime-free cast, no true inheritance/mixin), but LSP and other tools are fragile. In addition, invoking an object method seems to be roughly twice as slow as a record/module field access — I suppose it's because the latter is just an access via offset. That's on a micro benchmark so in reality it might be worse.

just implemented key generation https://codeberg.org/mro/seppo/src/branch/develop/lib/as2.ml#L95

We're looking to hire someone to join our build-systems team with a focus on open-source tooling. We currently release almost a million lines of code of our internal libraries and tools, including things like Sexplib, Base, Core, Async, Incremental, Bonsai, Hardcaml, memtrace-viewer, and patdiff.

We have internal tooling for moving code from our internal repositories to Github and for publishing to opam, and for ferrying information back from Github to our internal tools, so that developers can more easily and promptly respond to PRs and issues coming from the outside.

We want to make open-sourcing our code better and faster, so it's easier for us to work with outside contributors, and improvements can get out to the community more quickly. Your work would be to make our releases delightfully easy and reliable!

I wrote a bit more about it here:

https://twitter.com/yminsky/status/1536766031313739776?s=20&t=sCyUlHGHO1y3znBh4pl0Xw

If you're interested, go ahead and make an ordinary application to our software engineering role, and mention that you're interested in "open-source tooling". We're happy to hire for this role in both London and New York.

dune has very powerful extensions, but the documentation doesn't tell you directly. Today I'll share a specific example of how we can make dune do many things with a dune configuration.

For example

• Publish compiled documents to our documentation server
• Sending email notifications to email groups
• Sending SMS notifications to administrators
• Build a document and open a browser to preview the document page

Let's start with an example, we create a dune file in the root directory of our project, which you may not have originally, you have to create a new one, we enter the following

; now we tell you how to define a custom rule
; rule start with (rule )
(rule
; (alias is point  the command name , so you can run this rule by call  dune build @docopen
 (alias docopen)
 ; following line is very important, it tell dune do not cache this build command, so it will running every call
without any cache
 (deps (universe))
 ; action  (system  to told system run command by `sh` in your Linux/MacOS, windows user may running cmd.exe
 ; cd ../.. is change the base directory of the running command ,or the default directory will be _build/default
 (action (system "cd ../.. && pwd &&  dune build @doc && open _build/default/_doc/_html/index.html" ))
)
; end of one piece of rule

; and we define more and more rule as we want
(rule
  (alias whoami)
  (deps (universe))
  (action (system "uname -a;whoami"))
)

In this example, we define two rules, the rules are the tasks that dune can recognize, in dune, it is called rules

Because it is a custom build command, we use alias to take a unique and non-repeating alias.

The first build command is to build the document and open the browser preview.

Our alias is docopen

Then deps we add universe to tell dune that you don't want to cache and give me a new build every time. If you don't add this line, dune will only give you one build, and then because of the cache, you won't be able to execute it later.

action following by system here, action is the command to start, system means to use the system shell (windows is cmd, linux macos is sh) to give you the execution of the code you specify.

You can see the first we are first change the directory to the project root directory [because the default directory is _build/default], and then we perform the build document generation, and then open open the generated html page.

The first build command is this, if you want to perform the first build task, you can type

dune build @docopen

Then our second build command, relatively simple, with reference to the first, we can add a lot of build commands we want to add inside this dune configuration file.

We just need to specify different alias aliases for them, no duplication.

The official documentation also specifies some other available commands, I won't go into them one by one. Since I prefer to use shell scripts, I really only need the system to execute my shell scripts for me.

The 0.4.0 release of Diskuv OCaml for Windows users is available! It is usable enough that I've let my school-age kids (elementary through high school) install it and go through some tutorials.

https://github.com/diskuv/dkml-installer-ocaml#readme

The links to the documentation are available from the above link as well.

Here are the one-time inconveniences if you install this release:

1. The built-in antivirus Windows Defender treats newly signed binaries like spam. There needs to be enough people who "Report this file as safe" before the binaries are trusted. If you do nothing but mark it safe or install it on Windows, you are helping others!
2. The installer will automatically install the Visual Studio compiler if needed. But Visual Studio sometimes requires a reboot. The instructions will tell you if you need the reboot.
3. The Visual Studio Code OCaml plugin defaults to expecting a legacy ocamlenv program on Windows. You have to search for ocamlenv in Visual Studio Code Settings and disable it. This should have a fix, but not in time for this release.

It is my pleasure to share with you the ocamlformat configurator as a web page.

Ocamlformat is a great tool that really makes editing code a more pleasant experience. It has a bunch of different built in profiles and many additional options to fine tune how the code should look like. While I would encourage most people and new projects to use one of the default profiles, the many options are helpful when transitioning an existing codebase. Unfortunately it is not super easy to figure out which options to use and how to combine them. There are 58 parameters! I've spent a long time trying different combinations by changing an option in my .ocamlformat, running `dune build @fmt`, checking the code, going back to the first step… It is a tedious work. So I decided to make a simple web interface with all of the options available and a faster feedback loop.

Thanks to js_of_ocaml the task was not too complicated. Ocamlformat can be compiled to javascript, there is nothing special to do. Which means everything can be done in the browser, the code won't leak to anyone, there is no need to maintain a server, and the result will be guaranteed to be identical as a formatting with the cli tool.

The configuration can be set through text (just put the content of your `.ocamlformat` in the text box) and through a bunch of dropdown. They will be combined together. The dropdown takes precedence over the textual configuration if an option is set in both.

The project has been started as part of the "open source day" at Ahrefs (we try to dedicate some time to open source projects that we use internally). It is still in its infancy. Please pardon the terrible style, I am not a web developer and didn't have time to make it look nicer yet. There are some annoying things to fix (no feedback when the code is invalid and can't be formatted), and many improvements to come (a way to download the configuration for example). But I think that it is already working well enough to be used by others.

You can find the configurator at https://ahrefs.github.io/ocamlformat/
The source code is on github at https://github.com/ahrefs/ocamlformat/tree/ahrefs/web-ui/bin/web-ui

If you like ocaml and want to look for a job, we have some positions available

Hi! optiml-transport was just released on opam. This library binds C++ primitives to solve the [optimal transportation](https://en.wikipedia.org/wiki/Transportation_theory_(mathematics)) problem between finite weighted point clouds (i.e. finite measures). Concretely, this allows to lift any metric on a base space to a metric on finitely supported probability measures over that base space. (In fact, the library works with cost functions more general than that satisfying the metric axioms.) The library also outputs an optimal coupling between any two such measures. Optimal transportation has many applications in statistics, graphics, optimization, etc.

The library consists in bindings to https://github.com/nbonneel/network_simplex