[cwn] Attn: Development Editor, Latest OCaml Weekly News
Alan Schmitt
alan.schmitt at polytechnique.org
Tue Nov 27 11:08:22 PST 2018
Hello
Here is the latest OCaml Weekly News, for the week of November 20 to 27,
2018.
Table of Contents
─────────────────
Published a post about what we are doing and going to do about BuckleScript development
Ocamlformat and the ocaml.org coding guidelines
Release of OCaml-R
Resources for Advanced Module Usage
Digestif 0.7.1
Xavier Leroy (and others) - On Computer Science
md2mld 0.3.0
Wanted: new maintainer for cppo
Build-/Installation-Tools - not enogh of them?
Ocaml Github Pull Requests
Other OCaml News
Old CWN
Published a post about what we are doing and going to do about BuckleScript development
═══════════════════════════════════════════════════════════════════════════════════════
Archive:
[https://discuss.ocaml.org/t/published-a-post-about-what-we-are-doing-and-going-to-do-about-bucklescript-development/2920/1]
Hongbo Zhang announced
──────────────────────
In case you are interested, here is the link:
[https://bucklescript.github.io/blog/2018/11/19/next-half]
Ocamlformat and the ocaml.org coding guidelines
═══════════════════════════════════════════════
Archive:
[https://discuss.ocaml.org/t/ocamlformat-and-the-ocaml-org-coding-guidelines/2922/1]
Anil Madhavapeddy announced
───────────────────────────
I just wanted to draw the community's attention to [ocamlformat#501],
which gathers together many of the coding guidelines for OCaml, with
the goal of ensuring that ocamlformat can automate the formatting
process.
As noted on the issue, the current coding guidelines are designed for
humans, but we are increasingly getting tools such as ocamlformat and
ocp-indent which mechanise the process. This is a good chance to get
involved at this point in ocamlformat's development with this,
especially if you have a large codebase which could benefit from
standardised formatting in the near future. Please weigh in at
[ocamlformat#501], especially with pointers to counterexamples to your
own codebases if applicable.
[ocamlformat#501] https://github.com/ocaml-ppx/ocamlformat/issues/501
Release of OCaml-R
══════════════════
Archive:
[https://sympa.inria.fr/sympa/arc/caml-list/2018-11/msg00028.html]
Philippe Veber announced
────────────────────────
I'd like to announce a preview release of ocaml-r, a library that
can be used to interact with the R language interpreter and write
clean wrappers to R functions and packages. This library was
developped a long time ago by Maxence Guesdon and Guillaume Yziquel,
and I've maintained it since then for my own needs. The library is
available on opam, under version 0.1.1, and on github [0].
The goal of this release is to see if other people could find it
useful, in which case I can spend a little more time writing
documentation on how to use it, and help write more wrappers. Please
get in touch via the issue tracker if interested.
Cheers,
Philippe.
[0] [https://github.com/pveber/ocaml-r]
Resources for Advanced Module Usage
═══════════════════════════════════
Archive:
[https://discuss.ocaml.org/t/resources-for-advanced-module-usage/1774/1]
robkuz asked
────────────
does anybody have links/tutorials etc. for usage of modules? I have
read the lightweight higher kinded types paper and I am searching for
other resources in that direction.
kantian replied
───────────────
You can have a look on the paper [ML module mania] which present a
type safe, separetly compiled and extensible interpreter for the Lua
language. In the same spirit, you have the work of Oleg Kiselyov on
[tagless-final embedded DSL]. Or from the same author than the paper
on ligthweight higher-kinded types, you have their proposal for
[modular implicit] which go further.
About the last paper, imagine that you want to write a function `show'
that works on mutliple data types but not uniformly. In a lot of
languages, this is done with dynamic dispatching. Since OCaml doesn't
have runtime type representation, we have to rely on something which
is closed to a static dispatching, and we can do this with
*first-class* modules.
┌────
│ module type Showable = sig
│ type t
│ val show : t -> string
│ end
│
│ let show (type a) (module M : Showable with type t = a) x = M.show x
└────
Now you can define a module for each type that you want to convert to
a `string`, and you have to *explicitly* pass it to your fonction
`show`.
┌────
│ module Int_show = struct
│ type t = int
│ let show = string_of_int
│ end
│
│ module Float_show = struct
│ type t = float
│ let show = string_of_float
│ end
│
│ # show (module Int_show) 3;;
│ - : string = "3"
│
│ # show (module Float_show) 3.4;;
│ - : string = "3.4"
└────
The idea behind modular implicit is that in this situation, the module
to use to show your value is *automatically infered* by the compiler
in such a way that you don't have to *explicitly* pass it to your
function. This will be very useful, especially when the module in
question is the result of a functor application. Indeed, imagine that
you know how to show values of two types `a' and `b', then you know
how to show a pair of type `a * b'. To encode this you have to write a
*functor*:
┌────
│ module Pair_show (A : Showable) (B : Showable):
│ Showable with type t = A.t * B.t = struct
│ type t = A.t * B.t
│ let show (x,y) = Printf.sprintf "(%s, %s)" (A.show x) (B.show y)
│ end
│
│ # show (module Pair_show (Int_show) (Float_show)) (1, 2.5);;
│ - : string = "(1, 2.5)"
└────
[ML module mania]
https://www.cs.tufts.edu/~nr/pubs/maniaws-abstract.html
[tagless-final embedded DSL]
http://okmij.org/ftp/tagless-final/course/optimizations.html
[modular implicit]
https://www.cl.cam.ac.uk/~jdy22/papers/modular-implicits.pdf
Michael Thomas asked and Daniel Bünzli replied
──────────────────────────────────────────────
> This looks really interesting - do you know if the complete source
code is available anywhere?
It's [here].
[here] https://github.com/lindig/lua-ml
Ivan Gotovchits also replied
────────────────────────────
The [Modules][1] section is a prerequisite must read. All advance
papers more or less are based on these papers. The [F-ing modules][2]
paper is a very interesting read, albeit being a little bit
fictional. I also found [this thesis][3] to be an interesting
compilation, although it is focusing more on SML.
[1]: [https://ocaml.org/docs/papers.html#Modules]
[2]: [https://people.mpi-sws.org/~rossberg/f-ing/f-ing-jfp.pdf]
[3]: [https://people.mpi-sws.org/~dreyer/thesis/old/thesis050405.pdf]
Digestif 0.7.1
══════════════
Archive: [https://discuss.ocaml.org/t/ann-digestif-0-7-1/2941/1]
Charles Edouard Lecat announced
───────────────────────────────
I’m happy to announce a new release of [digestif 0.7.1], available for
installation via OPAM.
Digestif is a library which contains some hashes function like:
• MD5
• SHA1
• SHA224
• SHA256
• SHA384
• SHA512
• BLAKE2B
• BLAKE2S
• RIPEMD160
And the recently added
• WHIRLPOOL
Particularities of digestif:
Linking trick: This project provides 2 implementations of the hash
algorithms: one written in C (digestif.c) and the other in OCaml
(digestif.ocaml), each one fulfilling the same interface. In order to
choose your implementation, you can simply use the linking trick, by
selecting at link time the implementation you wish to use. The C
implementation will provide a smaller execution time, while the OCaml
one will bring more portability to your project (ex: to JavaScript
with js_of_ocaml).
Constant time: Some applications require that secret values are
compared in constant time. This Functions like String.equal do not
have this property, so we provide a small package — eqaf — providing a
constant-time equal function. Digestif uses it to check equality of
hashes — it also exposes unsafe_compare if you don’t care about timing
attacks in your application.
Run-time lock: When calling C code from the OCaml environment, the
garbage collector states needs to be saved as C code may need
allocated values, which the GC could move or change. This is why we
implemented the hash algorithms with bigarrays, which are contained in
a specific area of the GC, and never will be moved. This way, we were
able to remove the run-time lock when calling the others C functions,
improving the speed of the computations. A behavior even more useful
as the GC is global in a multi-threaded environment, locking it pauses
every threads: With digestif you can compute the hash in parallel of
others operations without affecting your performances.
[digestif 0.7.1] https://github.com/mirage/digestif/releases/tag/v0.7.1
Xavier Leroy (and others) - On Computer Science
═══════════════════════════════════════════════
Archive:
[https://discuss.ocaml.org/t/xavier-leroy-and-others-on-computer-science/2942/1]
Jp R announced
──────────────
For those of you who understand French, I invite you to follow a serie
of courses on computer science at the College de France.
Xavier Leroy a mis son beau costume, sa chemise blanche et sa cravate
pour nous parler des sciences du logiciel.
A must see!
[https://www.college-de-france.fr/site/xavier-leroy/inaugural-lecture-2018-11-15-18h00.htm]
md2mld 0.3.0
════════════
Archive: [https://discuss.ocaml.org/t/ann-md2mld-0-3-0/2948/1]
Marcello Seri announced
───────────────────────
I am happy to announce the first release of [md2mld], available now
from OPAM.
`md2mld' converts a Markdown-format file into the `mld' format used by
[odoc] to render HTML documentation or OCaml libraries. You can use
this script to automatically embed a `README.md' file into API
documentation for an OCaml library.
I made it because multiple repositories have their most interesting
short examples in their README, and I wanted an easy way to integrate
them in the generated documentation without duplicating too much the
efforts.
You can see an example of use in the documentation of [the tool
itself] and in the new documentation of [ocaml-rpc].
[md2mld] https://github.com/mseri/md2mld
[odoc] https://github.com/ocaml/odoc
[the tool itself] https://github.com/mseri/md2mld
[ocaml-rpc] http://mirage.github.io/ocaml-rpc/rpclib/rpc/index.html
Wanted: new maintainer for cppo
═══════════════════════════════
Archive:
[https://discuss.ocaml.org/t/wanted-new-maintainer-for-cppo/2959/1]
Martin Jambon announced
───────────────────────
[Cppo] is a C-style preprocessor for OCaml. I started the project in
2009, when I was working on yojson and didn't want to be tied to
camlp4 for simple things like `#include' and conditional
compilation. Since then, other projects have used it, typically as a
last resort to manage version incompatibilities. Today, 57 packages in
opam depend directly on cppo.
The project was recently handed off to [ocaml-community] in an effort
to benefit from a wider community. I no longer wish to be in charge of
supervising the project because it's too much for me, when combined
with other projects. Ideally, we're looking for a person maintaining
cppo with the support of their employer. The project is very
stable. There are no new features in sight and very few bug
reports. Maintenance would consist in roughly one day a month,
generally spent answering incoming questions and working with users to
solve their problems or review patches.
Let us know if you're interested!
[Cppo] https://github.com/ocaml-community/cppo
[ocaml-community] https://github.com/ocaml-community/meta
Build-/Installation-Tools - not enogh of them?
══════════════════════════════════════════════
Archive:
[https://sympa.inria.fr/sympa/arc/caml-list/2018-11/msg00059.html]
Anil Madhavapeddy announced
───────────────────────────
Julia Lawall said:
Personally, I was in the end forced to install opam. But
I don't want to force my users to install it (to figure
out how to get it to work, I had to contact a member of
Gallium - and my users don't have that opportunity). I
would prefer that they can just use the ocaml that comes
with their system package manager.
Since opam is the recommended method of installation,
couldn't there at least be provided understandable
instructions? That really seems like a tougher time than
what is necessary.
Dear Julia, dear all,
Thanks for the helpful reminder that the opam and ocaml documentation
needs a refresh. We’ve just gone through a fairly major release cycle
with opam2 and dune1, and it’s to be expected that there are some
inconsistencies.
To clear up one misconception on this thread — opam is *not* the only
recommended mechanism to get the OCaml compiler. We go to some
trouble to ensure that OCaml is packaged up natively on the OS package
managers where possible, and there is a list on the ocaml.org
installation page with popular distributions.
The problems begin when the user needs a particular version of OCaml,
which is a common requirement for teaching. The system package
managers typically lag in their versions (again, listed on the
ocaml.org installation page). At this point, opam is indeed the
simplest tool to bootstrap the precise version of the compiler and
packages that you require, but at the expense of requiring an
OCaml-specific tool.
Now, I recognise the need for improving the installation instructions,
and particularly so with step-by-step guides to getting things
installed. However, I would implore those with complaints to register
the inaccuracies on the opam issue tracker [1], so that we can at
least learn about them and fix them just as we do with any software
bug.
[1] [https://github.com/ocaml/opam/issues]
It’s particularly frustrating to see these threads erupt with pent up
(and valid) annoyances from users that we could have addressed if
someone had reported it. Even better, please do send in PRs with some
suggested text for the website, and take some load off our overworked
maintainers :-)
For whoever said that my Ubuntu opam2 PPA is hard to Google, the
process of creating it was roughly:
• spend a few hours fighting with the Debian packaging scripts
• get x86_64/i386/arm32/arm64/ppc64le all working in Launchpad
• post on
[https://discuss.ocaml.org/t/opam-2-0-experimental-ppas/2446] to get
no feedback whatsoever
• eventually just push it live after one user gets back with feedback
• wait for complaints to show up that its hard to find
Without feedback, it’s very difficult to know what to prioritise, and
Ubuntu is just one of many, many Linux distributions that we have to
worry about.
Japp Boender also wrote:
I'd like to chime in here - as the person responsible for
doing most of the OCaml packaging for pkgsrc, I've noticed
that I can hardly ever just update a package to a new
version anymore - I'll generally also need to update the
infrastructure as some sort of new build tool will have
become involved, with all its attendant quirks, or someone
will have decided to change the name of packages, or some
other change will have occurred. Things seem to be in a
constant state of flux, and thus packaging becomes quite
time-consuming.
This is indeed the result of progress on the tooling side. There’s
been a lot of work in the last few years on deprecating older tools
(camlp4, ocamlbuild) and moving towards modern alternatives such as
dune for build and opam2 for publishing.
Things are settling down now: dune is emerging as a well-maintained
and portable alternative to the myriad of build systems that have been
proposed in the past. The bootstrapping problems you mention should
also have become a *lot* easier with opam2, since the solver is linked
into the binary and no external aspcud is needed. If you do still run
into any problems with fakeroots and such, please report them on the
dune or opam issue tracker and we’ll take a look.
Behind the scenes, there are other benefits from a consistent build
system: cross compilation and Windows support are greatly improved
now.
Malcolm Matalka also wrote:
Is there a reasonable workflow for how to turn opam
packages into packages for existing OS's though?
Currently it does seem like users need to know about Ocaml
to use things written in Ocaml, if only because most of
the focus has been on opam. Other OSs tend to have old
packages.
Our goal (with my dune and opam developer hat on) is to provide
sufficient metadata within a dune description of a project to
automatically generate opam *and* upstreamable OS packages (from
templates). This will look something like “dune @package” and really
reduce the burden on developers and OS maintainers. I’d like, for
example, the native OpenBSD packages to be able to be replaced by a
mechanically generated version.
See this issue for more: [https://github.com/ocaml/dune/issues/1498]
Julia Lawall also wrote:
The question is what to do after installing opam. Even if
there is nothing to do after installing opam, it would be
helpful to say that. If there is something to do after
installing opam to get the ocaml compiler for example, as
opposed to just the runtime system, it would be helpful to
say that too. The documentation should be designed from
the point of view of the person who has never used ocaml
or opam, never wants to use them again, and has no contact
with the ocaml community. Otherwise, people who want to
try some ocaml software, but are not actually forced to
use it, will just give up.
I completely agree with this sentiment. I’m personally motivated to
make sure ocaml/opam meet these standards, as we are moving to
teaching using OCaml in the Cambridge University Computer Lab from
next year, so I’ll definitely be proposing some changes myself :-)
I’d love to hear from other teachers about the sort of environments
you have to work in — we’ve been considering shifting to a combination
of browser-based IDEs (for homogeneity across student laptops) and
other systems.
Finally, this thread might seem like it is full of complaints, but the
tooling is steadily improving and leaving behind silent and satisfied
users. Dune in particular has made as big a difference to our
community as opam did when it was first released five years ago. At
ICFP this year, the OCaml Workshop was full of industrial users who
were thankful for Dune improving their day-to-day development, as well
as the ecosystem of new tools such as ocamlformat, merlin, odoc and so
on, and the Coq project is moving to adopt it now as well! I’m not
suggesting we rest on our laurels, but as the year end holiday
approaches, I would be delighted if users to email their favourite
tool developer a note of encouragement to continue to work on it. And
then file an issue to get the docs fixed :-)
Ocaml Github Pull Requests
══════════════════════════
Gabriel Scherer and the editor compiled this list
─────────────────────────────────────────────────
Here is a sneak peek at some potential future features of the Ocaml
compiler, discussed by their implementers in these Github Pull
Requests.
• [Typed PPX]
[Typed PPX] https://github.com/ocaml/ocaml/pull/2161
Other OCaml News
════════════════
From the ocamlcore planet blog
──────────────────────────────
Here are links from many OCaml blogs aggregated at [OCaml Planet].
• [Senior Haskell / Full Stack Developer at PRODA Ltd (Full-time)]
• [Safely typing algebraic effects]
• [Front End Developer (ReactJS & Purescript)]
• [An Introduction to Tezos RPCs: Signing Operations]
[OCaml Planet] http://ocaml.org/community/planet/
[Senior Haskell / Full Stack Developer at PRODA Ltd (Full-time)]
https://functionaljobs.com/jobs/9117-senior-haskell-full-stack-developer-at-proda-ltd
[Safely typing algebraic effects]
http://gallium.inria.fr/blog/safely-typing-algebraic-effects
[Front End Developer (ReactJS & Purescript)]
https://jobs.github.com/positions/fbceb632-fbda-430e-b537-733ef5a8b298
[An Introduction to Tezos RPCs: Signing Operations]
http://www.ocamlpro.com/2018/11/21/an-introduction-to-tezos-rpcs-signing-operations/
Old CWN
═══════
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[Alan Schmitt]
[send me a message] mailto:alan.schmitt at polytechnique.org
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[Alan Schmitt] http://alan.petitepomme.net/
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