OCaml Weekly News

On behalf of the dune team, I'm pleased to announce the release of Dune 1.9.0. This release introduces a few exciting new features:

• A tagging mechanism for implementations called variants
• The ability to build libraries in the Coq proof assistant.
• A new dune init command to help users quickly generate boilerplate and get start with dune projects (contributed by @shonfeder)

I would like to thank Lucas Pluvinage and @ejgallego for contributing the first two features respectively. They've also collaborated on a blog post to describe these features in detail.

As usual, the change log is replicated here for your convenience:

We at Imandra just open sourced minisat-ml , a reimplementation of Minisat 2.2 in OCaml. The goal is to experiment with the performance difference between C++ and (low level) OCaml that stays as close as possible to the original.

The report provides more detailed explanations on the porting process, as well as some experimental results. Personally I think it'd also be an interesting sample point for flambda and other performance tools of the ecosystem, since minisat 2.2 is a fixed target in a field known to require very high performance.

I would like to run some continuous integration like travis ci on my opam package. Unfortunately ocaml is not supported directly by travis. But I have found the GitHub repository ocaml/ocaml-ci-scripts and some instructions on how to use it.

My questions:

• Is this a stable form on how to use travis with ocaml?
• Are there experiences and are they good?
• Why has this solution been chosen instead of integrating ocaml support directly into travis?
• Isn’t the solution an overkill, because it requires a complete opam and ocaml installation on the travis machines in order to test an opam package? Isn’t there the risk that travis might block this form of usage in the future?
• Is there a better method to use CI with ocaml?

I've had good experiences with travis recently, using the docker script (an example here: https://github.com/c-cube/iter/blob/master/.travis.yml).

if your package is opam 2-friendly it's just a matter of a local pin and a few switches. there are other options (variables, really) to install extra deps or deal with optional deps.

It's not particularly overkill since it just starts with a docker image with pre-installed opam switches.

> - Is this a stable form on how to use travis with ocaml?

There is auto-ci that can be used to generate travis configuration relying on ocaml-ci-scripts.

https://github.com/yomimono/autoci

> - Is this a stable form on how to use travis with ocaml?
>
> - Are there experiences and are they good?

Last I checked, there were over 400 repositories on GitHub using ocaml-ci-scripts. It's pretty stable.

> - Why has this solution been chosen instead of integrating ocaml support
> directly into travis?

Why do you need direct integration with Travis? The use of the Docker support has made the necessity for that essentially obsolete.

See, for example: https://github.com/mirage/ocaml-cohttp/blob/master/.travis.yml

in cohttp, which uses Travis and Docker to test the libraries on a variety of Linux distributions.

> - Isn’t the solution an overkill, because it requires a complete opam and
> ocaml installation on the travis machines in order to test an opam package?
> Isn’t there the risk that travis might block this form of usage in the future?
>
> - Is there a better method to use CI with ocaml?

This solution is pretty good for most people. I'd encourage you to give it a try, and to contribute back any improvements or feature requests you might have after trying it out for a while.

Thanks for all the hints. Some experiences:

I have used the .travis.yaml file from the repo ocaml/ocaml-ci-scripts, reduced the build matrix to a minimum (only 4.07) and it worked out of the box. However to took approx 8 min for linux and 12 min for osx.

Therefore I have changed in the travis file ‘.travis-opam.sh’ to ‘.travis-docker.sh’ and added ’services: -docker’, because docker has been recommended by many.

Now the build failed after some seconds. Maybe there is more to do than this trivial change to switch to docker.

Is there some documentation on how to use docker? Is it worth the effort i.e. will it run faster or has it more features?

We are pleased to announce the release of opam 2.0.4.

This new version contains mainly backported fixes, you can find more information in this blog post.

opam is a source-based package manager for OCaml. It supports multiple simultaneous compiler installations, flexible package constraints, and a Git-friendly development workflow.

And for those of you using the Ubuntu PPA, it has been updated to the 2.0.4 release: https://launchpad.net/~avsm/+archive/ubuntu/ppa

Similarly the macOS brew package.

MacPorts has been updated as well, though it might take an hour or two for all the mirrors to adjust.

Here are links from many OCaml blogs aggregated at OCaml Planet.

• The Mirage retreat: field trip report
• opam 2.0.4 release
• opam 2.0.4 release
• Dune 1.9.0