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

[Alan Schmitt <alan.schmitt@polytechnique.org>]

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Hello

Here is the latest OCaml Weekly News, for the week of August 02 to 09,
2022.

Table of Contents
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pyml_bindgen: a CLI app to generate Python bindings directly from OCaml value specifications
Interesting OCaml Articles
Logs to a file (a primitive way)
Timedesc 0.8.0 - modern date time handling
OCaml website: Owl book not listed
Application-specific Improvements to the Ecosystem
Other OCaml News
Old CWN


pyml_bindgen: a CLI app to generate Python bindings directly from OCaml value specifications
════════════════════════════════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-pyml-bindgen-a-cli-app-to-generate-python-bindings-directly-from-ocaml-value-specifications/8786/8>


Ryan Moore announced
────────────────────

New release
╌╌╌╌╌╌╌╌╌╌╌

  Version 0.4.1 is now available from [GitHub] and [Opam].  The [change
  log] has more details.


[GitHub]
<https://github.com/mooreryan/ocaml_python_bindgen/releases/tag/0.4.1>

[Opam] <https://opam.ocaml.org/packages/pyml_bindgen/>

[change log]
<https://github.com/mooreryan/ocaml_python_bindgen/blob/main/CHANGELOG.md>


New stuff
╌╌╌╌╌╌╌╌╌

New attributes
┄┄┄┄┄┄┄┄┄┄┄┄┄┄

  There is a new attribute you can use: `py_arg_name'. It allows you to
  use different argument names on the OCaml side from those that are
  used on the Python side.

  One use case is for Python functions that have an argument name that
  is the same as some reserved OCaml keyword. In this case, you can use
  `py_arg_name' to map it to something else on the OCaml side.

  ┌────
  │ val f : t -> method_:string -> unit -> string
  │ [@@py_arg_name method_ method]
  └────

  The attribute is followed by two items, the first is the argument name
  on the OCaml side, and the second is the argument name on the Python
  side.

  See the [attributes example] on GitHub for more info.


[attributes example]
<https://github.com/mooreryan/ocaml_python_bindgen/tree/main/examples/attributes>


Helper scripts
┄┄┄┄┄┄┄┄┄┄┄┄┄┄

  I added a couple of scripts to help in cases where you need to run
  `pyml_bindgen' on a lot of different input files in one go.  I have
  been using them when writing bindings for bigger Python libraries, and
  in cases where there are a lot of cyclic python classes to bind.

  [This] example has more info about using the helper scripts.


[This]
<https://github.com/mooreryan/ocaml_python_bindgen/tree/main/examples/recursive_modules>


Other stuff
┄┄┄┄┄┄┄┄┄┄┄

  • Added an option to split generated modules into `ml' and `mli'
    files.
  • Added a dev package for (hopefully) easier installation of
    development dependencies.


Interesting OCaml Articles
══════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/interesting-ocaml-articles/1867/99>


Calascibetta Romain announced
─────────────────────────────

  Hi, I would like to share my recent article about GADTs and state
  machines: [GADTs and state machine]

  It's another introduction about GADTs and it explains a bit what I did
  for [robur.io]. Eenjoy it and happy hacking!


[GADTs and state machine]
<https://blog.osau.re/articles/gadt_and_state_machine.html>

[robur.io] <https://robur.io>


Logs to a file (a primitive way)
════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/logs-to-a-file-a-primitive-way/10262/1>


🌍 Marcus Rohrmoser asked
─────────────────────────

  I found
  <https://github.com/oxidizing/sihl/blob/c6786f25424c1b9f40ce656e908bd31515f1cd09/sihl/src/core_log.ml#L18>
  and wonder what a primitive way to log to a file would be.

  I need to keep `stdout' clean and not show any log message under all
  circumstances.


🌍 Marcus Rohrmoser later added
───────────────────────────────

  I do a cgi and `stdout' is the response – logging has to go to a
  separate file. Not even `stderr' as I want debug logs not to taint the
  webserver error log in case. And I would like to funnel logging
  through `Logs'.


Yawar Amin suggested and 🌍 Marcus Rohrmoser replied
────────────────────────────────────────────────────

        I don't know about `logs' but it should be relatively easy
        to keep an open file handle and print log messages there.

  <https://opam.ocaml.org/packages/logs/> - I like the loglevel
  approach. But maybe I will do without and pass around the channel,
  yes.


Jean Michel suggested
─────────────────────

  I believe logs support logging to a file via Format. See
  <https://erratique.ch/software/logs/doc/Logs/index.html#val-format_reporter>


Shon also suggested
───────────────────

  I’ve found logs very ergonomic and easy to work with. I tend to pull
  it in via [Bos], which has a very nice interface to OS
  interactions. Opening the `Bos_setup' module also does default logs
  configuration, and I find all quite painless and pleasant.


[Bos] <https://erratique.ch/software/bos>


🌍 Marcus Rohrmoser said
────────────────────────

  thanks @yawaramin @beajeanm @shonfeder, I took a [middle ground] and
  went along the lines of <https://opam.ocaml.org/packages/logs/> (using
  the loglevels and logging call style) but base writing almost directly
  on [out_channel]. (I need a log rotation on top)

  I was struggling with lost messages however – the logfile remained
  empty until I flushed after each log message.

  Is that known behaviour that writing to a channel (with
  [Printf.fprintf]) doesn't necessarily end up in the file? Even when
  closed quickly.


[middle ground]
<https://codeberg.org/mro/seppo/src/branch/develop/lib/logr.ml>

[out_channel] <https://ocaml.org/api/Stdlib.html#TYPEout_channel>

[Printf.fprintf] <https://ocaml.org/api/Printf.html>


UnixJunkie replied
──────────────────

  You must Printf.printf with "%!" at the end of your format string, to
   be sure that the log is flushed to file.

  That's what I do in dolog: <https://github.com/UnixJunkie/dolog>


Timedesc 0.8.0 - modern date time handling
══════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-timedesc-0-8-0-modern-date-time-handling/10138/2>


Darren announced
────────────────

  Tiny update: Timedesc 0.9.0 has been released, moving `sexplib'
  dependency into `timedesc-sexp' and moved from `mparser' to `angstrom'
  for some date time text parsers since angstrom is a strict necessity
  for some binary (de)serialization already.

  This overall means Timedesc is about as slim as it can get as a date
  time handling lib, depending only on: `seq', `angstrom', `result', and
  `ptime' (`ptime' is not a strict dependency, but it's nice to have
  timedesc <-> ptime convertors).


Florent Monnier asked
─────────────────────

  Is this a lib that targets to process dates and time in a
  programmatically way?  (this is what the provided example make me
  think) Or is it also supposed to be used to print something readable
  for a user else than a programmer?

  If there is no end-user goal in this lib, please just ignore my
  message, and sorry to make you lose some time.

  In the other case if you consider printing for end users, it's maybe
  worth to mention that there is the [DateLocale-ocaml] module that is
  available and which provides the name for the months, and days for
  more than 200 languages. It also provides abbreviated versions for
  both months and days, which are often used.

  The [ocaml-community/calendar] was not designed with localisation in
  mind, it just does `String.sub d 0 3' to provide short names, which
  will not work with languages that need UTF8.

  There is this PR that is still waiting for some review since 2 years
  to make it compatible with localisation:
  [ocaml-community/calendar/pull/33].

  (At least the patch is available there for someone who could be
  interested.)

  I don't know if it could interest some one but I see that the example
  outputs a list of dates, that look like some kind of logs. In case
  some one would like to visualise it in a way similar than the unix
  command `cal' you can just create empty files where the file name
  follows the pattern YYYY-MM-DD like for example "dir/2022-08-06.txt",
  you will then be able to visualise it in the console with [detri].


[DateLocale-ocaml] <https://github.com/fccm/DateLocale-ocaml>

[ocaml-community/calendar] <https://github.com/ocaml-community/calendar>

[ocaml-community/calendar/pull/33]
<https://github.com/ocaml-community/calendar/pull/33/commits/9fcd7386e287f8841e503fb1d1e0547295aeb0c9>

[detri] <https://github.com/fccm/detri>


Darren replied
──────────────

        Is this a lib that targets to process dates and time in a
        programmatically way?  (this is what the provided example
        make me think) Or is it also supposed to be used to print
        something readable for a user else than a programmer?
  Development has been primarily focused on former, mostly because
  solving it properly was already (very) involved.

  Now that Timedesc has stabilised, the latter reads like a very nice
  next TODO to match feature parity of other date time libs.

        In the other case if you consider printing for end users,
        it’s maybe worth to mention that there is the
        [DateLocale-ocaml] module that is available and which
        provides the name for the months, and days for more than
        200 languages. It also provides abbreviated versions for
        both months and days, which are often used.

  Looks neat! I believe there have been requests of locale sensitive
  pretty printing/conversion functions, so I definitely would be
  interested in incorporating your work (if that was the intention).

        I don’t know if it could interest some one but I see that
        the example outputs a list of dates, that look like some
        kind of logs. In case some one would like to visualise it
        in a way similar than the unix command `cal` you can just
        create empty files where the file name follows the pattern
        YYYY-MM-DD like for example “dir/2022-08-06.txt”, you will
        then be able to visualise it in the console with [detri].

  I was interested in something like this for another small utility cmd
  I've written, neat!


[DateLocale-ocaml] <https://github.com/fccm/DateLocale-ocaml>

[detri] <https://github.com/fccm/detri>


OCaml website: Owl book not listed
══════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ocaml-website-owl-book-not-listed/10274/1>


Andreas Poisel said
───────────────────

  It would be nice to add [OCaml Scientific Computing] to the list on
  <https://ocaml.org/books>.

  This is a great book and it would be a shame not to promote it.  Maybe
  anyone responsible for the website reads this or can point me in the
  right direction.

  I'm not in any way affiliated with the authors of this book.


[OCaml Scientific Computing]
<https://link.springer.com/book/10.1007/978-3-030-97645-3>


Application-specific Improvements to the Ecosystem
══════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/application-specific-improvements-to-the-ecosystem/10223/49>


Deep in this thread, Kay-Uwe Kirstein said
──────────────────────────────────────────

  Personally, I often use the monadic Result type together with a
  polymorphic variant for the actual errors. This makes dealing with
  errors from different "levels" of my software (library, command-line
  tool, and GUI) quite comfortable (and type-safe!).  @keleshev has
  written a nice blog post on this:
  <https://keleshev.com/composable-error-handling-in-ocaml> with a
  recent follow up:
  <https://keleshev.com/advanced-error-handling-in-ocaml>


Other OCaml News
════════════════

From the ocaml.org blog
───────────────────────

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

  • [Irmin in the Browser]


[the ocaml.org blog] <https://ocaml.org/blog/>

[Irmin in the Browser]
<https://tarides.com/blog/2022-08-02-irmin-in-the-browser>


Old CWN
═══════

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  [Alan Schmitt]


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