[Caml-list] Attn: Development Editor, Latest OCaml Weekly News

Alan Schmitt
2022-02-22T12:43:17Z

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Hello

Here is the latest OCaml Weekly News, for the week of February 15 to 22,
2022.

Table of Contents
─────────────────

OCAML goes Quantum computing
Layout Parsing and Nicely Formatted Error Messages
ptime 1.0.0 and mtime 1.4.0
Timedesc 0.6.0
OCaml from the Very Beginning now free in PDF and HTML formats
Dune 3.0.0
Blog Post "2021 at OCamlPro"
Packstream 0.1
OCaml 4.14.0, first beta release
Old CWN

OCAML goes Quantum computing
════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ocaml-goes-quantum-computing/9333/1>

Florian said
────────────

It seems that silently OCAML is now entering the Quantum world. It
looks that the Interpreter for "Twist" [New programming language for
Quantum computing] is made with OCAML: [GitHub for Twist]

[New programming language for Quantum computing]
<https://scitechdaily.com/twist-mits-new-programming-language-for-quantum-computing/>

[GitHub for Twist] <https://github.com/psg-mit/twist-popl22>

Anton Kochkov then added
────────────────────────

Haskell has a nice package for quantum computing - Quipper. I
recommend to take a look to it for inspiration as well:
• <https://hackage.haskell.org/package/quipper-language>
• <http://www.mathstat.dal.ca/~selinger/quipper/>
• <https://arxiv.org/pdf/1304.3390.pdf>
• <https://arxiv.org/pdf/2105.03522.pdf> (a new language that reuses
linear types in the Haskell to represent quantum specifics during
the Quipper type check)

Layout Parsing and Nicely Formatted Error Messages
══════════════════════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-layout-parsing-and-nicely-formatted-error-messages/9343/1>

Hbr announced
─────────────

In a previous [post] I have described my way from LALR parsing to
combinator parsing. Now I am more and more convinced that combinator
parsing is really a good and flexible way to write parsers. The new
release 0.5.0 of `Fmlib` focuses on layout parsing and nicely
formatted error messages by using combinator parsing.

The library can be installed via opam by `opam install fmlib'. There
is a [github repository] hosting the source code. The [API] can be
found online. See also a [tutorial] on combinator parsing.

[post]
<https://discuss.ocaml.org/t/my-way-from-lalr-parsing-to-combinator-parsing/7377>

[github repository] <https://github.com/hbr/fmlib>

[API] <https://hbr.github.io/fmlib/odoc/index.html>

[tutorial] <https://hbr.github.io/fmlib/odoc/fmlib_parse/parse.html>

Layout Parsing
╌╌╌╌╌╌╌╌╌╌╌╌╌╌

Most programming languages express hierarchical structures by some
kind of parentheses. Algol like languages use `begin' `end', C like
languages use curly braces `{', `}' to enclose blocks of code. Since
blocks can be nested inside blocks, the hierarchical or tree structure
is well expressed by the syntax.

For the human reader blocks are usually indented to make the
hierarchical structure graphically visible. Programming languages like
*Haskell* and *Python* ommit the parentheses and express the
hierarchical structure by indentation. I.e. the indentation is part of
the grammar. This is pleasing to the eye, because many parentheses can
be ommitted.

The hierarchical structure in the following schematical source file is
immediately visible without the need of parentheses.

┌────
│ xxxxxxxxxxx
│ xxx
│ xxx
│ xxxxxxx
│ xxxxxxxx
│ xxx
└────

Lower level blocks are indented with respect to their parent block and
siblings at the same level are vertically aligned.

Because of this good readability configuration languages like yaml
have become very popular.

Unfortunately there are not many parsers available which support
indentation sensitivity. The library [Fmlib] has support to parse
languages whose grammar uses indentation to structure blocks
hierarchically.

There are only 3 combinators needed to introduce layout parsing in
combinator parsing. Suppose that `p' is a combinator parsing a certain
contruct. Then we have

• `indent 4 p': Parse the construct described by `p' indented at least
4 columns relative to its environment

• `align p': Parse the construct desribed by `p' aligned vertically
with its siblings

• `detach p': Parse the construct described by `p' without any
indentation or alignment restrictions

In order to parse a list of ~p~s vertically aligned and indented
relative to its environment by at least one column we just write

┌────
│ one_or_more (align p) |> indent 1
└────

and parse a structure with the schematic layout

┌────
│ xxxxxxxx
│
│ pppppppp
│
│ pppppp
│
│ pppp
│
│ xxxxx
└────

[Fmlib]
<https://hbr.github.io/fmlib/odoc/fmlib_parse/Fmlib_parse/index.html>

User Frienly Error Messages
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

It is important to for a parser writer to make syntax error messages
user friendly. [Fmlib] has some support to write friendly error
messages. There is the operator `<?>' copied from the Haskell library
`parsec' which helps to equip combinators with descriptive error
message in case they fail to parse the construct successfully.

At the end of a failed parsing, the syntax (or semantic) errors have
to be presented to the user. Suppose there is a combinator parser for
a yaml like structure. The library writes by default for you error
messages in the form

┌────
│ 1 |
│ 2 | names:
│ 3 | - Alice
│ 3 | - Bob
│ 4 |
│ 5 | category: encryption
│ ^
│
│ I have encountered something unexpected. I was
│ expecting one of
│
│ - at 3 columns after
│
│ - sequence element: "- <yaml value>"
│
│ - at 2 columns before
│
│ - key value pair: "<key>: <yaml value>"
│
│ - end of input
└────

The raw information (line and column numbers, individual expectations,
failed indentation or alignment expectation) is available as well so
that you can present the error messages to the user in any different
form.

There is also a component [Fmlib_pretty] in the library for pretty
printing any ascii text.

[Fmlib]
<https://hbr.github.io/fmlib/odoc/fmlib_pretty/Fmlib_pretty/index.html>

[Fmlib_pretty]
<https://hbr.github.io/fmlib/odoc/fmlib_pretty/Fmlib_pretty/index.html>

ptime 1.0.0 and mtime 1.4.0
═══════════════════════════

Archive:
<https://discuss.ocaml.org/t/ann-ptime-1-0-0-and-mtime-1-4-0/9344/1>

Daniel Bünzli announced
───────────────────────

It's my pleasure to announce new releases of ptime and mtime. Ptime
and mtime provide types and clocks for POSIX and monotonic time.

These releases change the JavaScript support strategy for clocks by
implementing the primitives in pure JavaScript and linking them via
`js_of_ocaml'.

This means that both the `ptime.clock.jsoo' and `mtime.clock.jsoo'
libraries no longer exist[^1]. Instead simply use the `ptime.clock.os'
or `mtime.clock.os' libraries like you would do for your regular
programs.

By side effect, the packages also no longer depend on any of
`js_of_ocaml''s packages.

Thanks to Hugo Heuzard (@hhugo) for suggesting and implementing these
changes. Thanks also to Jonah Beckford for his Windows build patches.

Other changes are described in the release notes for [`ptime'] and
[`mtime'].

Home pages: [ptime], [mtime]

Docs & manuals: [ptime], [mtime] or `odig doc ptime mtime'

Install: `opam install ptime mtime'

[^1]: I had intended to only deprecate these libraries by `warning' in
the `META' files and requiring the replacement library but it seems
the warning won't show up in many contexts including `dune' builds. So
a breaking change it is.

[`ptime']
<https://github.com/dbuenzli/ptime/blob/master/CHANGES.md#v100-2022-02-16-la-forclaz>

[`mtime']
<https://github.com/dbuenzli/mtime/blob/master/CHANGES.md#v140-2022-02-17-la-forclaz-vs>

[ptime] <https://erratique.ch/software/ptime>

[mtime] <https://erratique.ch/software/mtime>

[ptime] <https://erratique.ch/software/ptime/doc>

[mtime] <https://erratique.ch/software/mtime/doc>

Timedesc 0.6.0
══════════════

Archive: <https://discuss.ocaml.org/t/ann-timedesc-0-6-0/9349/1>

Darren announced
────────────────

I am pleased to announce the release of [Timedesc] 0.6.0.

Timedesc is a very comprehensive date time handling library with good
support of time zone.

[Timedesc] <https://github.com/daypack-dev/timere>

Features:
╌╌╌╌╌╌╌╌╌

• Timestamp and date time handling with platform independent time zone
support
• Subset of the IANA time zone database is built into this library
• Supports Gregorian calendar date, ISO week date, and ISO ordinal
date
• Supports nanosecond precision
• ISO8601 parsing and RFC3339 printing

Changes
╌╌╌╌╌╌╌

This release adds a fair number of quality of life improvements and
additional features. Many thanks to @glennsl for the suggestions and
feedback!

The most important sections of the changelog are as follows:

• Main breaking changes:
• Changes in ISO week date functions (shorting label for arguments,
quality of life changes)
• Removed `_date' suffix in names of `Date.Ymd_date' and
`Date.ISO_ord_date'
• Added "partial date" modules with ISO8601 parsing and printing
facilities
• `ISO_week'
• `Ym'
• Added additional ISO8601 printing facilities for all three calendar
systems
• `Date.Ymd.pp/to_iso8601' (these are just aliases to the RFC3339
printers)
• `Date.ISO_week_date.pp/to_iso8601'
• `Date.ISO_ord.pp/to_iso8601'
• Added additional ISO8601 parsing facilities for all three calendar
systems
• `Date.Ymd.of_iso8601[_exn]'
• `Date.ISO_week_date.of_iso8601[_exn]'
• `Date.ISO_ord.of_iso8601[_exn]'
• Added additional comparison functions to `Date'
• `lt', `le', `gt', `ge', `compare'
• Added arithemtic functions to `Date'
• Added `pp/to_iso8601' functions as aliases to the rfc3339 functions
to `Timedesc'
• Patched ISO8601 parsers and RFC3339/ISO8601 printers to handle
second level time zone offset
• Rare occurrence in tzdb but picked up by some new tests

OCaml from the Very Beginning now free in PDF and HTML formats
══════════════════════════════════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ocaml-from-the-very-beginning-now-free-in-pdf-and-html-formats/9361/1>

John Whitington announced
─────────────────────────

Thanks to a grant from the [OCaml Software Foundation], I am able to
release my book [OCaml from the Very Beginning] at no cost in its
existing PDF format, and in a new HTML format too.

You can find it here:
[https://johnwhitington.net/ocamlfromtheverybeginning/].

The paperback and Kindle versions continue to be available from Amazon
as before.

The book has recently been updated to make it ready for OCaml 4.14
which involved only minor changes to error handling and warnings. I
have also opened the [source].

[OCaml Software Foundation] <https://ocaml-sf.org/>

[OCaml from the Very Beginning] <https://ocaml-book.com>

[https://johnwhitington.net/ocamlfromtheverybeginning/]
<https://johnwhitington.net/ocamlfromtheverybeginning/>

[source] <https://github.com/johnwhitington/mlbook>

Dune 3.0.0
══════════

Archive: <https://discuss.ocaml.org/t/ann-dune-3-0-0/9374/1>

Rudi Grinberg announced
───────────────────────

On behalf of the dune team, I’m delighted to announce the availability
of dune 3.0.

The team has been working on this release for over 6 months, and
there’s a bunch of new work to report. I’ll only highlight the some of
the interesting new developments:

• The watch mode has been rewritten from scratch to be faster and more
scalable. We also no longer rely on any 3rd party tools such as
fswatch. If any of you still have a dune workspace dune is still
struggling with, we cannot wait to hear from you.

• The watch mode now also starts an RPC server in the background. This
RPC protocol is going to be the basis for other tools to interact
with dune. Watch out for announcement on the LSP side to see how
we’ll be making use of it to improve the editing experience.

• The dune cache has been rewritten as well. It is now simpler and
more reliable. There are still some components missing, such as
distribution of the artifacts on the network. Nevertheless, we
welcome you all to experiment with this feature and give us
feedback.

• We’ve addressed one of our oldest feature requests: high level rules
for ctypes projects. This feature is still experimental, so we need
feedback from real world projects before declaring it as mature.

Of course, there are many other fixes, enhancements, and only a few
breaking changes in this release. We hope you have an easy time
upgrading.

Happy Hacking.

/Editor’s note: for the full changelog, please follow the archive link
above./

Blog Post "2021 at OCamlPro"
════════════════════════════

Archive:
<https://discuss.ocaml.org/t/blog-post-2021-at-ocamlpro/9390/1>

Fabrice Le Fessant announced
────────────────────────────

We just published a review of what OCamlPro did in 2021:

<https://www.ocamlpro.com/blog/2022_01_31_2021_at_ocamlpro>

A lot of OCaml, but also some Rust, Cobol, Solidity, and a lot of
Formal Verification! OCamlPro is always looking for skilled OCaml
developers to hire, so if you are interested, contact us at
contact@ocamlpro.com

Packstream 0.1
══════════════

Archive: <https://discuss.ocaml.org/t/ann-packstream-0-1/9392/1>

Tomasz Barański announced
─────────────────────────

I have a pleasure to announce the release of [Packstream] 0.1.

Packstream is a library to parse/serialize [Packstream binary format].

This is the initial release. It is functional but very very limited in
scope. It allows parsing a binary stream into a Packstream datatype
and serializing the datatype into a binary stream.

[Packstream] <https://github.com/tomob/packstream>

[Packstream binary format]
<https://7687.org/packstream/packstream-specification-1.html>

OCaml 4.14.0, first beta release
════════════════════════════════

Archive:
<https://discuss.ocaml.org/t/ocaml-4-14-0-first-beta-release/9396/1>

octachron announced
───────────────────

The release of OCaml 4.14.0 is close.

The set of new features has been stabilized, and most opam packages
already work with this release. After two alpha releases, we have
created a first beta version to help you update your softwares and
libraries ahead of the release.

If you find any bugs, please report them at:

<https://github.com/ocaml/ocaml/issues>

The full release of OCaml 4.14.0 is currently expected for the middle
of March.

Compared to the last alpha, we have a last minute correction for one
of the new function in the Seq module, some documentation
improvements, few configuration and internal tweaks.

Installation instructions
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

The base compiler can be installed as an opam switch with the
following commands

┌────
│ opam update
│ opam switch create 4.14.0~beta1 --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git
└────
With opam 2.1, the previous command line can be simplified to
┌────
│ opam update
│ opam switch create 4.14.0~beta1
└────
If you want to tweak the configuration of the compiler, you can switch
to the option variant with:

┌────
│ opam update
│ opam switch create <switch_name> --packages=ocaml-variants.4.14.0~beta1+options,<option_list>
│ --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git
└────
or with opam 2.1:
┌────
│ opam update
│ opam switch create <switch_name> ocaml-variants.4.14.0~beta1+options <option_list>
└────

where `<option_list>' is a comma separated list of `ocaml-option-*'
packages. For instance, for a flambda and no-flat-float-array switch:
┌────
│ opam switch create 4.14.0~beta1+flambda+nffa ocaml-variants.4.14.0~beta1+options ocaml-option-flambda
│ ocaml-option-no-flat-float-array
└────
All available options can be listed with `opam search ocaml-option'.

The source code for the beta is also available at these addresses:

• <https://github.com/ocaml/ocaml/archive/4.14.0-beta1.tar.gz>
• <https://caml.inria.fr/pub/distrib/ocaml-4.14/ocaml-4.14.0~beta1.tar.gz>

Changes compared to the last alpha
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

The full list of changes for OCaml 4.14 is available at
<https://github.com/ocaml/ocaml/blob/4.14/Changes>

Standard library
┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄

• *additional fixes* [10583], +[10998]: Add over 40 new functions in
Seq. (François Pottier and Simon Cruanes, review by Nicolás Ojeda
Bär, Daniel Bünzli, Naëla Courant, Craig Ferguson, Wiktor Kuchta,
Xavier Leroy, Guillaume Munch-Maccagnoni, Raphaël Proust, Gabriel
Scherer and Thierry Martinez)

[10583] <https://github.com/ocaml/ocaml/issues/10583>

[10998] <https://github.com/ocaml/ocaml/issues/10998>

Documentation
┄┄┄┄┄┄┄┄┄┄┄┄┄

• [10397]: Document exceptions raised by Unix module functions on
Windows (Martin Jambon, review by Daniel Bünzli, David Alsopp,
Damien Doligez, Xavier Leroy, and Florian Angeletti)

• [10794]: Clarify warning 57 (Ambiguous or-pattern variables under
guard) (Wiktor Kuchta, review by Gabriel Scherer)

[10397] <https://github.com/ocaml/ocaml/issues/10397>

[10794] <https://github.com/ocaml/ocaml/issues/10794>

Build system
┄┄┄┄┄┄┄┄┄┄┄┄

• [10828] Build native-code compilers on OpenBSD/aarch64 (Christopher
Zimmermann)

• [10835] Disable DT_TEXTREL warnings on x86 32 bit architecture by
passing -Wl,-z,notext in mksharedlib and mkmaindll. Fixes relocation
issues, reported in [9800], making local patches in Debian, Alpine,
and FreeBSD superfluous. (Hannes Mehnert with Kate Deplaix and
Stéphane Glondu, review by Xavier Leroy)

[10828] <https://github.com/ocaml/ocaml/issues/10828>

[10835] <https://github.com/ocaml/ocaml/issues/10835>

[9800] <https://github.com/ocaml/ocaml/issues/9800>

Code generation
┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄

• [10719]: Ensure that build_apply respects Lambda.max_arity (Stephen
Dolan, review by Xavier Leroy)

[10719] <https://github.com/ocaml/ocaml/issues/10719>

Internal/compiler-libs
┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄┄

• *additional fixes* [10718], +[11012]: Add "Shape" information to the
cmt files. Shapes are an abstraction of modules that can be used by
external tooling to perform definition-aware operations. (Ulysse
Gérard, Thomas Refis and Leo White, review by Florian Angeletti)

[10718] <https://github.com/ocaml/ocaml/issues/10718>

[11012] <https://github.com/ocaml/ocaml/issues/11012>

Old CWN
═══════

If you happen to miss a CWN, you can [send me a message] and I'll mail
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[online].

[Alan Schmitt]

[send me a message] <mailto:alan.schmitt@polytechnique.org>

[the archive] <https://alan.petitepomme.net/cwn/>

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[online] <http://lists.idyll.org/listinfo/caml-news-weekly/>

[Alan Schmitt] <https://alan.petitepomme.net/>

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