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

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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of August 27 to
September 03, 2019.

Table of Contents
─────────────────

Ocaml-multicore: report on a June 2018 development meeting in 
Paris
Interesting OCaml Articles
Old CWN


Ocaml-multicore: report on a June 2018 development meeting in 
Paris
═══════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ocaml-multicore-report-on-a-june-2018-development-meeting-in-paris/2202/10>


Deep in this thread, sid announced
──────────────────────────────────

  As a small step towards multicore, its interesting to note that
  <https://github.com/ocaml/ocaml/pull/8713> just got merged to 
  master!


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

  Archive:
  <https://discuss.ocaml.org/t/interesting-ocaml-articles/1867/46>


Yotam Barnoy announced
──────────────────────

  <https://www.ocamlpro.com/2019/08/30/ocamlpros-compiler-team-work-update/>


Old CWN
═══════

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

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  subscribe
  [online].

  [Alan Schmitt]


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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of October 08 
to 15,
2019.

Table of Contents
─────────────────

capnp-rpc 0.4.0
Ocaml-protoc.plugin.1.0.0
Old CWN


capnp-rpc 0.4.0
═══════════════

  Archive: 
  <https://discuss.ocaml.org/t/ann-capnp-rpc-0-4-0/4524/1>


Thomas Leonard announced
────────────────────────

  I'm pleased to announce the release of [capnp-rpc 0.4.0], an 
  OCaml
  implementation of the Cap'n Proto RPC specification.

  If you haven't used the library before, please see the 
  [documentation
  and tutorial]. Cap'n Proto RPC aims to provide secure, 
  efficient,
  typed communications between multiple parties.

  This library is now being used to build [ocaml-ci], where it is 
  used
  for all communication between the web frontend and backend 
  services,
  and to provide a command-line client.


[capnp-rpc 0.4.0]
<https://github.com/mirage/capnp-rpc/releases/tag/v0.4.0>

[documentation and tutorial]
<https://github.com/mirage/capnp-rpc/blob/master/README.md>

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

Main changes since v0.3
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  Breaking changes:

  • Wrap errors with the ``Capnp' tag to make it easier to compose 
  with
    other types of error.

  • Prefix all command-line options with `capnp-'.
    e.g. `--listen-address' is now `--capnp-listen-address'.  The 
    old
    names were confusing for applications that supported other 
    protocols
    too (e.g. a web server).

  New features:

  • Add `Capability.with_ref' convenience function.  This 
  automatically
    calls `dec_ref' when done.

  • Add Unix `Cap_file' module to load and save `Sturdy_refs'.  In
    particular, this ensures that saved cap files get a mode of 
    `0o600',
    since they contain secrets.

  • Export cmdliner network address parsing.  This is useful if 
  you
    don't want to use the default option parsing.  For example, if 
    you
    want to make Cap'n Proto an optional feature of your program.

  • Upgrade from `uint' (which is deprecated) to the newer 
  `stdint'.
    The latest version of `uint' is just a wrapper around 
    `stdint', so
    this shouldn't break anything if you are using the latest 
    version.

  • Put cmdliner options in their own man-page section.  Use
    `Capnp_rpc_unix.manpage_capnp_options' to control where in 
    your
    man-page they appear.

  • Enable `SO_KEEPALIVE' for TCP connections.  For use with 
  Docker's
    libnetwork, try something like this in your `stack.yml':
    ┌────
    │ sysctls:
    │   - 'net.ipv4.tcp_keepalive_time=60'
    └────


Ocaml-protoc.plugin.1.0.0
═════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-ocaml-protoc-plugin-1-0-0/4535/1>


Anders Fugmann announced
────────────────────────

  I'm happy to announce the second release of 
  [ocaml-protoc-plugin].

  Ocaml-protoc-plugin is a plugin to googles `protoc' compiler 
  which
  generates type idiomatic to ocaml from `.proto' files including 
  full
  compliant serialization and deserialization functions.


[ocaml-protoc-plugin] 
<https://github.com/issuu/ocaml-protoc-plugin>

Most noteworthy changes in this release:
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • Full proto2 support.
  • The list of dependencies has been slimmed way down, and now 
  only
    depends on `conf-protoc' (the `protoc' compiler and googles 
    *well
    known types*).
  • Buckescript support.
  • Added options to change the ocaml (type for scalar types (int, 
  int64
    or int32).

  Many thanks to Wojtek Czekalski for helping trimming 
  dependencies and
  for Buclescript support.


Full changelog:
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • Support enum aliasing
  • Avoid name clash with on 'name'
  • Fix code generation when argument contains a path
  • Refactor internal types to make serialization and 
  deserialization
    type spec symmetrical.
  • Optimize deserialization for messages with max_id < 1024
  • Don't depend on Base in runtime
  • Slim runtime dependencies: Remove need for base, ocplib-endian 
  and
    ppx_let
  • Honor [packed=…] flag.
  • Make fixed scalar types default to int32 and int64
  • Support proto2 specification
  • Add options to switch between int64|int32 and int
  • Fix name clash problem with special enum names
  • Refactor serialization and deserialization to simplify emitted 
  code
  • Eagerly evaluate serialization (for speed).


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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

[Alan Schmitt]

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Here is the latest OCaml Weekly News, for the week of October 29 
to
November 05, 2019.

Table of Contents
─────────────────

vim-ocaml - new home
Old CWN


vim-ocaml - new home
════════════════════

  Archive: 
  <https://discuss.ocaml.org/t/ann-vim-ocaml-new-home/4615/1>


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

  Dear Vim & Neovim users,

  I would like to announce that I've officially moved the 
  [vim-ocaml]
  repository under the control of the OCaml organization on
  github. Please direct your bug reports and pull requests to this
  repository. This move is done not because vim-ocaml is being
  neglected, on the contrary, there's an active team of 
  maintainers that
  recently expanded. I simply want to take this opportunity to 
  draw more
  Vim & Noevim users to this project, as I suspect many users 
  aren't
  aware of recent efforts.


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


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of November 05 
to 12,
2019.

Table of Contents
─────────────────

Mirage 3.7.1 released
Old CWN


Mirage 3.7.1 released
═════════════════════

  Archive: 
  <https://discuss.ocaml.org/t/mirage-3-7-1-released/4634/1>


Hannes Mehnert announced
────────────────────────

  MirageOS 3.7.1 is released to opam repository now.

  Breaking change:
  • The hooks previously defined in
    OS.Main.at_enter/at_enter_iter/at_exit/at_exit_iter are now 
    part of
    Mirage_runtime (only used by mirage-entropy)
    <https://github.com/mirage/mirage/pull/1010>

  Behaviour changes of MirageOS unikernels:
  • A unikernel now always calls the Mirage_runtime.at_exit 
  registered
    hooks – once a unikernel succesfully executed its `start' in
    `Lwt_main.run', `exit 0' is called to ensure this behaviour
    <https://github.com/mirage/mirage/pull/1011>
  • Top-level exceptions are no longer caught (there used to be in
    mirage-unix/mirage-xen/mirage-solo5 custom handlers). The 
    OCaml
    runtime prints the exception and backtrace on stdout and calls 
    exit
    2 (from 4.10.0, abort() will be called).

  Deprecations (being removed from Mirage 4.0)
  • All Mirage_YYY_lwt are deprecated, Mirage_YYY interfaces are 
  no
    longer astracted over 'a io and buffer. This reduces the 
    amount of
    opam packages - mirage-yyy-lwt are no longer part of the 
    release
    (each mirage-yyy package provides a Mirage_yyy_lwt module for
    backwards compatibility). Motivation was discussed in
    <https://github.com/mirage/mirage/issues/1004>
  • mirage-types and mirage-types-lwt are deprecated, please use 
  the
    Mirage_YYY signatures directly instead.

  Other observable changes
  • `mirage configure' now deletes all exising opam files

  Most reverse dependencies are already released to opam, have a 
  look at
  <https://github.com/mirage/mirage/issues/1012> for progress (and 
  the
  temporary <https://github.com/mirage/mirage-dev.git#easy> opam
  overlay).


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of November 19 
to 26,
2019.

Table of Contents
─────────────────

tiny_httpd 0.1
printbox.0.3
v0.13 release of Jane Street packages
opam2nix (v1)
GitHub Actions for OCaml / opam now available
OCurrent 0.1 (CI/CD pipeline eDSL)
New pages for OCaml API
Irmin 2.0.0 release
Tail cascade: a new indentation style for some OCaml constructs
Old CWN


tiny_httpd 0.1
══════════════

  Archive: <https://discuss.ocaml.org/t/ann-tiny-httpd-0-1/4727/1>


Simon Cruanes announced
───────────────────────

  Hello and good morning, I'm pleased to announce that 
  [tiny_httpd] 0.1
  has been released and is on opam.

  The goal is to emulate python's standard `http.server' by 
  providing a
  0-dependencies, minimalist, simple HTTP server for embedding in
  applications that are not primarily a website, with very basic 
  routing
  (thanks to `Scanf'). A binary `http_of_dir' is also distributed 
  and
  can be used to serve a directory, with optional upload of files.


[tiny_httpd] <https://github.com/c-cube/tiny_httpd>


printbox.0.3
════════════

  Archive: <https://discuss.ocaml.org/t/ann-printbox-0-3/4731/1>


Simon Cruanes announced
───────────────────────

  <https://aws1.discourse-cdn.com/standard11/uploads/ocaml/original/2X/8/8e7c55c5ab69c12f53a7862d2f84dd6e0cfc0dc0.png>

  ┌────
  │ let b =
  │   let open PrintBox in
  │   PrintBox_unicode.setup();
  │   frame @@ grid_l [
  │     [text "subject"; text_with_style Style.bold "announce: 
  printbox 0.3"];
  │     [text "explanation";
  │     frame @@ text {|PrintBox is a library for rendering nested 
  tables,
  │     trees, and similar structures in monospace text or 
  HTML.|}];
  │     [text "github";
  │     text_with_style Style.(bg_color Blue) 
  "https://github.com/c-cube/printbox/releases/tag/0.3"];
  │     [text "contributors";
  │      vlist_map (text_with_style Style.(fg_color Green)) 
  ["Simon"; "Guillaume"; "Matt"]];
  │     [text "dependencies";
  │     tree empty
  │       [tree (text "mandatory")
  │ 	 [text "dune"; text "bytes"];
  │        tree (text "optional")
  │ 	 [text "uutf"; text "uucp"; text "tyxml"]]];
  │     [text "expected reaction"; text "🎉"];
  │   ]
  │
  │ let () = print_endline @@ PrintBox_text.to_string b
  └────

  ([actual link to the release])


[actual link to the release]
<https://github.com/c-cube/printbox/releases/tag/0.3>


v0.13 release of Jane Street packages
═════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-v0-13-release-of-jane-street-packages/4735/1>


Xavier Clerc announced
──────────────────────

  We are pleased to announce the v0.13 release of Jane Street 
  packages!

  This release comes with 14 new packages, and a number of fixes 
  and
  enhancements. The documentation for this release is available on 
  our
  website:

  <https://ocaml.janestreet.com/ocaml-core/v0.13/doc/>

  The remainder of this mail highlights the main changes since the 
  v0.12
  release; we hope it will be useful to developers in the process 
  of
  migrating to the new version. A comprehensive changelog is 
  available
  at the end.


Notable changes
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  • Changed `Base', `Core_kernel', and `Core' functions to raise
    `Not_found_s' instead of `Not_found'.  `Hashtbl.find_exn' and
    `Map.find_exn' now include the key in their error message.

  • Changed `Core' and `Core_kernel' to export `int' comparison 
  rather
    than polymorphic comparison.

  • Removed the "robust" float comparison operators (`>.', `=.', 
  …)
    from the default namespace.

  • Replaced `sexp_*' types (`sexp_list', `sexp_option', 
  `sexp_opaque',
    …) with preprocessor attributes (`[@sexp.list]', 
    `[@sexp.option]',
    `[@sexp.opaque]', …).

  • Changed `let%map' syntax from `let%map.Foo.Let_syntax' to
    `let%map.Foo'.

  • Added to `match%optional' support for specifying a path, so 
  you can
    write `match%optional.Foo foo_option' rather than `let open
    Foo.Optional_syntax in match%optional foo_option'.

  • Improved `Base.Backtrace' so that it enables recording of 
  backtraces
    in more situations, specifically when `OCAMLRUNPARAM' is 
    defined but
    doesn't mention the backtrace flag, `b'.

  • Added javascript support for `Zarith', `Bigint', `Bignum', and
    `Bigdecimal'.

  • Changed `Hashtbl.create''s default `size' from 128 to 0.

  • Changed `Core_kernel.Command' so that all commands accept 
  double
    dash flags: `--help', `--version', and `--build-info'.


New packages
╌╌╌╌╌╌╌╌╌╌╌╌

  • async_udp (<https://github.com/janestreet/async_udp>): UDP 
  support
    for Async.

  • async_websocket 
  (<https://github.com/janestreet/async_websocket>): A
    library that implements the websocket protocol on top of 
    Async.

  • bonsai (<https://github.com/janestreet/bonsai>): A library for
    building dynamic webapps, using Js_of_ocaml.

  • postgres_async 
  (<https://github.com/janestreet/postgres_async>):
    OCaml/async implementation of the postgres protocol (i.e., 
    does not
    use C-bindings to libpq).

  • ppx_cold (<https://github.com/janestreet/ppx_cold>): Expands
    `[@cold]' into `[@inline never][@specialise never][@local 
    never]'.

  • ppx_pattern_bind 
  (<https://github.com/janestreet/ppx_pattern_bind>):
    A ppx for writing fast incremental bind nodes in a pattern 
    match.

  • ppx_python (<https://github.com/janestreet/ppx_python>):
    `[@@deriving]' plugin to generate Python conversion functions.

  • ppx_yojson_conv 
  (<https://github.com/janestreet/ppx_yojson_conv>):
    `[@@deriving]' plugin to generate Yojson conversion functions.

  • ppx_yojson_conv_lib
    (<https://github.com/janestreet/ppx_yojson_conv_lib>): Runtime 
    lib
    for `ppx_yojson_conv'.

  • pythonlib (<https://github.com/janestreet/pythonlib>): A 
  library to
    help writing wrappers around OCaml code for python.

  • sexp_select (<https://github.com/janestreet/sexp_select>): A 
  library
    to use CSS-style selectors to traverse sexp trees.

  • timezone (<https://github.com/janestreet/timezone>): Time-zone
    handling.

  • toplevel_backend 
  (<https://github.com/janestreet/toplevel_backend>):
    Shared backend for setting up toplevels.

  • zarith_stubs_js 
  (<https://github.com/janestreet/zarith_stubs_js>):
    Javascript stubs for the Zarith library.


Deprecations / Removals
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  `Async_kernel':

  • Deprecated monadic `ignore' functions in favor of `ignore_m'.

  `Base':

  • Deleted `Array.replace' and `replace_all' functions, which 
  have been
    deprecated since before the last public release.

  • Deprecated `Result.ok_unit'; use `Ok ()'.

  • Removed the `Monad' and `Applicative' interfaces' `all_ignore'
    function; it was previously deprecated and replaced by 
    `all_unit'.

  • Removed `List.dedup', which has been deprecated since 2017-04.

  • Removed `String' mutation functions, which have been 
  deprecated in
    favor of `Bytes' since 2017-10.

  • Deprecated `Array.truncate', `Obj_array.unsafe_truncate', and
    `Uniform_array.unsafe_truncate'.

  • Deprecated `Sys.argv', which has been superseded by 
  `get_argv',
    which is a function, reflecting the fact that `argv' can 
    change (as
    of OCaml 4.09).

  `Core_kernel':

  • Removed `Core_kernel.Std', which had been deprecated for a 
  year.

  • Deprecated type `Command.Spec.param' in favor of 
  `Command.Param.t'.

  • Removed `Hashtbl' functions that had been deprecated for 
  years.

  • Removed `Float.to_string_round_trippable', which has been 
  deprecated
    in favor of `to_string' since 2017-04.

  • Deprecated `Fqueue' functions where one should use `Fdeque' 
  instead:
    `bot', `bot_exn', and `enqueue_top'.

  • Deleted `Bus.unsubscribes', which will be obviated by a 
  performance
    improvement to `Bus.unsubscribe'.

  `Timing_wheel':

  • Removed the `alarm_upper_bound' function, which has been 
  deprecated
    for 6 months, and superseded by `max_allowed_alarm_time'.


Moves
╌╌╌╌╌

  `Core_kernel':

  • Moved `Bounded_int_table' to a standalone library.

  • Moved the `Pool' and `Tuple_type' modules to a standalone 
  library,
    `Tuple_pool'.

  `Async_unix':

  • Moved `Unix.Fd.replace' into a `Private' submodule.


Changelog
╌╌╌╌╌╌╌╌╌

  Please visit
  <https://discuss.ocaml.org/t/ann-v0-13-release-of-jane-street-packages/4735>


opam2nix (v1)
═════════════

  Archive: <https://discuss.ocaml.org/t/ann-opam2nix-v1/4741/1>


Tim Cuthbertson announced
─────────────────────────

  Anouncing opam2nix (v1)

  [opam2nix] generates [nix] expressions from the [opam] OCaml 
  package
  repository. It works similarly to [bundix], [node2nix], etc:

  You run an (impure) command to resolve all transitive dependency
  versions using the current opam repository, generating a .nix 
  file
  that locks down the exact package sources and versions. Then 
  this file
  can be imported to provide `buildInputs' for building your ocaml
  project in nix.

  *What is nix and why would I care?* Well, that's a long story 
  but the
   headline benefits of nix are:

  • reproducible builds (if it builds for me, it builds for you)
  • stateless (you don't set up switches and then install 
  packages, each
    expression specifies everything it needs, and anything you 
    don't
    have is fetched/built on demand)
  • language agnostic (takes care of non-ocaml dependencies)

  It's sadly not a shallow learning curve, but those benefits are 
  hard
  to find elsewhere, so I obviously think it's worthwhile. So if 
  you use
  nix (or would like to), please give it a try and provide
  feedback. I'll (slowly) start working on upstreaming it into 
  nixpkgs.


[opam2nix] <https://github.com/timbertson/opam2nix>

[nix] <https://nixos.org/>

[opam] <https://opam.ocaml.org/>

[bundix] <https://github.com/nix-community/bundix>

[node2nix] <https://github.com/svanderburg/node2nix>


GitHub Actions for OCaml / opam now available
═════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/github-actions-for-ocaml-opam-now-available/4745/1>


Anil Madhavapeddy announced
───────────────────────────

  I was in the [GitHub Actions] beta program and forward ported my 
  code
  to the latest version that just went public.  It's a pretty 
  simple way
  to get your OCaml code tested on Linux, macOS and Windows, 
  without
  requiring an external CI service.  The action attempts to 
  provide a
  homogenous interface across all three operating systems, so 
  invoking
  'opam' from subsequent actions should "just work".

  You can find it here:
  • In the GitHub Marketplace at
    <https://github.com/marketplace/actions/setup-ocaml>
  • Source code on <https://github.com/avsm/setup-ocaml/>
  • Hello World usage on
    <https://github.com/avsm/hello-world-action-ocaml>
  • Usage in ocaml-yaml:
    • 
    <https://github.com/avsm/ocaml-yaml/blob/master/.github/workflows/test.yml>
    • An [example ocaml-yaml run]

  This should be considered fairly experimental as GH Actions is 
  so new.
  If you do use it, then consider [updating this issue with your 
  usage].
  It does not current supporting caching yet, but is pretty fast 
  to
  bootstrap (~4minutes).

  It also doesn't have any higher level purpose other than to set 
  up an
  opam environment, since most of the additional functionality 
  such as
  revdeps testing is planned for addition to the [ocurrent DSL].
  Nevertheless, this GH feature will hopefully be useful for 
  smaller
  projects without a lot of computational requirements.  Let me 
  know how
  it goes!

  Windows is currently supported through @fdopen's excellent fork 
  that
  uses Cygwin.  As Windows support is being mainlined into opam 
  itself
  at the moment, I'm hoping that we will gradually move over to 
  that.
  That should eventually remove the need for two separate
  opam-repositories, so I won't be adding any features that are 
  Linux or
  macOS-specific and do not work on the Cygwin version.


[GitHub Actions] <https://github.com/actions>

[example ocaml-yaml run]
<https://github.com/avsm/ocaml-yaml/runs/314055554>

[updating this issue with your usage]
<https://github.com/avsm/setup-ocaml/issues/4>

[ocurrent DSL]
<https://discuss.ocaml.org/t/ann-ocurrent-0-1-ci-cd-pipeline-edsl/4742/2>


OCurrent 0.1 (CI/CD pipeline eDSL)
══════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/ann-ocurrent-0-1-ci-cd-pipeline-edsl/4742/1>


Thomas Leonard announced
────────────────────────

  [OCurrent] 0.1 has just been released to opam-repository.

  OCurrent is an OCaml eDSL intended for writing build/test/deploy
  pipelines. It is being used as the engine for [ocaml-ci] and the
  [docker-base-images] builder (used to build the OCaml Docker 
  images,
  such as `ocurrent/opam:alpine-3.10-ocaml-4.08'). Other good uses 
  might
  be building and redeploying a Docker service or a unikernel 
  whenever
  its source repository changes. It can be run locally as a single 
  Unix
  process.

  An OCurrent pipeline is written as an OCaml program, but the 
  OCurrent
  engine ensures that it is kept up-to-date by re-running stages 
  when
  their inputs change. A web UI is available so you can view your
  pipeline and see its current state.

  OCurrent can statically analyse the pipelines before they have 
  run,
  allowing it to run steps in parallel automatically and to 
  display the
  whole pipeline. It does this using a light-weight alternative to
  arrows, which doesn't require programming in an awkward 
  point-free
  style. See [CI/CD Pipelines: Monad, Arrow or Dart?] for more 
  about
  that.

  The basic functionality can be extended using "plugins" (just 
  normal
  OCaml libraries). Plugins are available for interacting with 
  Docker,
  Git, GitHub and Slack. These are in separate packages
  (e.g. `current_github') to avoid having the base package pull in 
  too
  many dependencies).

  There is also an optional Cap'n Proto RPC interface, in the
  `current_rpc' opam package. This is used, for example, by 
  [citty] to
  provide a TTY interface to ocaml-ci.

  [The OCurrent wiki] contains examples, and documentation on the
  various plugins.

  Here's an example pipeline (from the base image builder):

  <https://roscidus.com/blog/images/cicd/docker-base-images-thumb.png>


[OCurrent] <https://github.com/ocurrent/ocurrent>

[ocaml-ci] <https://github.com/ocurrent/ocaml-ci/>

[docker-base-images] 
<https://github.com/ocurrent/docker-base-images>

[CI/CD Pipelines: Monad, Arrow or Dart?]
<https://roscidus.com/blog/blog/2019/11/14/cicd-pipelines/>

[citty] <https://github.com/ocurrent/citty>

[The OCurrent wiki] <https://github.com/ocurrent/ocurrent/wiki>


Anil Madhavapeddy then added
────────────────────────────

  For those curious about the relation to the existing CI used in
  opam-repository, then it is no coincidence that @talex5 is the 
  author
  of both :-)

  This DSL is the next iteration of the [datakit-ci], but 
  specialised to
  be faster and simpler for extending with OCaml and more complex
  workflows that our OCaml Platform tools need these days (like
  ocamlformat linting, or dune expect promotion, or odoc
  cross-referenced doc generation).  We are planning a smooth 
  migration
  next year over to the new system, but wanted to release this 
  early to
  show you some of the pieces going into this new iteration.  I am
  particularly excited about the new tty-based interface that 
  saves an
  awful lot of clicking around on web UIs for CI results…


[datakit-ci] <https://github.com/moby/datakit>


New pages for OCaml API
═══════════════════════

  Archive: 
  <https://discuss.ocaml.org/t/new-pages-for-ocaml-api/4720/13>


Continuing this thread, sanette announced
─────────────────────────────────────────

  I have uploaded a new version (same link
  <https://sanette.github.io/ocaml-api/>)
  • background color for links in the TOC @Maelan
  • more indentation for value descriptions @Maelan, @grayswandyr
  • word wrapping long `<pre>' codes @grayswandyr
  • type table: remove `(*' and `*)', give more space to code wrt
    comments, diminish comment's color @grayswandyr

  searching is not ready yet… please wait suggestions for dark 
  theme
  welcome


sanette later added
───────────────────

  I have just uploaded a new version with a basic search engine.
  • for each page, you can search values/modules
  • in the general index page, the search includes also the 
  descriptions
  • search results are ranked by relevance

  the downside is that each page now comes with an index of about 
  570Kb
  in the form of an index.js file. I'm kind of hoping that the 
  browser
  will cache this, but I'm not sure. It would be maybe better to 
  only
  load the index file on demand.


Irmin 2.0.0 release
═══════════════════

  Archive: 
  <https://discuss.ocaml.org/t/ann-irmin-2-0-0-release/4746/1>


Thomas Gazagnaire announced
───────────────────────────

  On behalf of the Irmin development team, I am very happy to 
  announce
  the release of Irmin 2.0.0, a major release of the Git-like
  distributed branching and storage substrate that underpins
  [MirageOS]. We began the release process for all the components 
  that
  make up Irmin [back in May 2019], and there have been close to 
  1000
  commits since Irmin 1.4.0 released back in June 2018. To 
  celebrate
  this milestone, we have a new logo and opened a dedicated 
  website:
  [irmin.org].

  More details here: 
  <https://tarides.com/blog/2019-11-21-irmin-v2>


[MirageOS] <https://mirage.io/>

[back in May 2019]
<https://tarides.com/blog/2019-05-13-on-the-road-to-irmin-v2>

[irmin.org] <https://irmin.org/>


Tail cascade: a new indentation style for some OCaml constructs
═══════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/tail-cascade-a-new-indentation-style-for-some-ocaml-constructs/4736/1>


gasche announced
────────────────

  I recently decided to change my indentation style for certain 
  OCaml
  constructs in a way that I'm going to describe below. I just 
  coined a
  name for this approach, "tail cascade". I'm creating this topic 
  to
  convince everyone that this is a cool idea you should adopt as
  well. Or at least tolerate it when you review other people's 
  code.


Problem
╌╌╌╌╌╌╌

  Programs that heavily use `match' often see a shift to the right 
  due
  to nested indentation.

  ┌────
  │ match foo with
  │ | Foo -> ...
  │ | Bar x ->
  │   match bar x with
  │   | FooBar -> ...
  │   | Blah y ->
  │     match f y with
  │     | Some z ->
  │       ...
  └────

  Another problem with this style is that it suffers from the 
  "dangling
  bar" issue: if you try to add a new case for one of the exterior
  `match', it is parsed as belonging to the innermost `match'. 
  People
  have been recommending (rightly) to use `begin match .. end' for 
  all
  nested match constructs to avoid this issue.

  ┌────
  │ match foo with
  │ | Foo -> ...
  │ | Bar x ->
  │   begin match bar x with
  │   | FooBar -> ...
  │   | Blah y ->
  │     begin match f y with
  │     | None -> ...
  │     | Some z ->
  │       ...
  │     end
  │   (* now this is safe *)
  │   | FooBlah -> ...
  │   end
  └────

  But still the unpleasant shift to the right remains.


Proposal: cascading tail case
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  We should in general use `begin match .. end' for nested 
  matches. But
  the "cascading tail case" proposal is to *not* do it for the 
  *last*
  case of the pattern-matching, and instead *de-indent* (dedent) 
  this
  last case – tail case.

  ┌────
  │ match foo with
  │ | Foo -> ...
  │ | Bar x ->
  │ match bar x with
  │ | FooBar -> ...
  │ | Blah y ->
  │ match f y with
  │ | None -> ...
  │ | Some z ->
  │ ...
  └────

  Note that with this indentation style, the "dangling match" 
  problem is
  also avoided: unlike with the original, non `end'-protected 
  program,
  the indentation makes it immediately obvious that any further 
  case
  will be attached to the innermost match, and not any of the 
  exterior
  ones.

  A program using this "cascading tail" approach should always use
  `begin match .. end' for nested matches, except for a nested 
  match
  returned within the last branch of an outer match, which can
  (optionally) be dedented instead.

  The choice to dedent the last case corresponds to encouraging a
  sequential reading of the program, where the other cases are
  "auxiliary cases" checked first and dispatched quickly, and the 
  last
  case is the "main part" where the "rest" of the logic of the 
  program
  lies. This pattern is typical of nested pattern-matching on the
  `option' or `result' type for example:

  ┌────
  │ match foo x with
  │ | Error err ->
  │   fail_foo_error err
  │ | Ok y ->
  │ match bar y with
  │ | Error err ->
  │   fail_bar_error err
  │ | Ok () ->
  │ ...
  └────

  Remark: it is *not* always the case that the `Error' constructor 
  is
  the auxiliary case, and the `Ok' constructor is the main case;
  sometimes we implement fallback logic like "if `foo' work then 
  we are
  good, but otherwise we have to do this and that", and the error 
  case
  is the most salient (and longer) part of the program logic. I 
  would
  recommend being mindful, when you write code, of whether there 
  is a
  most convincing way to "sequentialize" it (distinguish auxiliary 
  and
  main/tail case), and avoid using cascading tails when there is 
  no
  clear sequentialization choice.

  Remark: some cases of tail cascades can be linearized by using a 
  good
  definition of "bind" and a monadic style. This tends to be very
  limited however: it fixes one of the constructors to always be 
  the
  "tail" constructor (always `Some', always `Ok'), and it only 
  works
  when the handling of the other constructors is very homogeneous
  (typically: return directly). In real code, many situations 
  occur
  where the monadic style doesn't fit the problem, but tail 
  cascade does
  help writing a readable program.


Generalization: tail cascade
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌

  While I have never seen cascading tail cases in real-world OCaml 
  code
  before (I'm happy to be given pointers; I think that the idea is 
  not
  new, but I'm not aware of previous attempts to give it a catchy 
  name
  and spread the cascade love), this is in fact a new (to me) 
  instance
  of a common technique that is used for other OCaml constructs:

  ┌────
  │ if foo x then ...
  │ else if bar x then ...
  │ else ... (* this `tail else` was dedented *)
  │
  │ let x = foo in
  │ let y = bar in (* this `tail let` was dedented *)
  │ ...            (* and the rest as well *)
  │
  │ bind foo @@ fun x ->
  │ bind bar @@ fun y -> (* this "tail function body" was dedented 
  *)
  │ ...                  (* and the rest as well *)
  └────

  I would call "tail cascade" (or maybe: "cascading tail") the 
  idea of
  dedenting the "rest" of an OCaml expression (compared to a 
  strict
  tree-nesting-based approach) when it morally describes the 
  "rest" of
  the expression. I use the name "tail" because those expressions 
  are
  almost always in tail-position in the sense of tail-calls.

  This general approach legitimizes some styles that I have seen, 
  and
  sometimes used, in the wild, while at the same time considering 
  that I
  may have been doing something improper, for example:

  ┌────
  │ if foo then blah else
  │ ... (* dedented *)
  │
  │
  │ Fun.protect
  │   ~finally:(...)
  │ @@ fun () ->
  │ ... (* dedented *)
  │
  │
  │ try simple_approach with exn ->
  │ ... (* dedented *)
  │
  │
  │ 1 +
  │ 2 + (* dedented *)
  │ ... (* dedented *)
  └────

  Remark: after a `then' or `else', many people share the 
  reasonable
  view that any expression containing imperative constructs (`foo; 
  bar')
  should be enclosed in a `begin .. end' block to avoid
  surprising-precedence issue. Just as for nested `match', this
  recommendation should be lifted for "tail else" constructs.

  Remark: The last example is a case where the dedented 
  expressions are
  *not* in tail-position from a runtime-evaluation point of view. 
  I am
  not sure as whether the two notions should be made to coincide 
  more
  strongly, but in any case I'm not fond of the style in this 
  particular
  example, I prefer to move the infix operator to the beginning of 
  the
  next line instead, following a different style and 
  justification.

  The possibility this "cascading tail" style today crucially 
  relies on
  the nesting properties of open-ended syntactic constructs, 
  notably
  `let' (commonly cascaded), and now `match' and `if
  ... else'. Proposals to transition to a syntax where `match' and
  `else' are forced to take a closing marker are incompatible with 
  the
  cascading style. I have not made my mind on whether this should 
  be
  considered a blocker for those proposals, but at least it shows 
  that
  having the open-ended form available has value for certain 
  programs.


Louis Gesbert then said
───────────────────────

  @gasche I prototyped a dedicated option in `ocp-indent', if 
  you're
  interested in trying it out :)
  ┌────
  │ opam pin 
  git+https://github.com/OCamlPro/ocp-indent#match-tail-cascade
  │ echo "match_tail_cascade=true" >> ~/.ocp-indent
  └────


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of November 26 
to
December 03, 2019.

Table of Contents
─────────────────

Irmin 2.0.0 release
How viable is delivering binaries linked to Cygwin to Windows 
customers?
Dune 2.0.0
Advanced C binding using ocaml-ctypes and dune
Upcoming breaking change in Base/Core v0.14
CI/CD Pipelines: Monad, Arrow or Dart?
Use of functors to approximate F# statically resolved type 
parameters
Old CWN


Irmin 2.0.0 release
═══════════════════

  Archive: 
  <https://discuss.ocaml.org/t/ann-irmin-2-0-0-release/4746/5>


Continuing this thread, samoht announced
────────────────────────────────────────

  And there is now a follow-up blog post, explaining how to use 
  the new
  GraphQL API available in Irmin2:
  <https://tarides.com/blog/2019-11-27-introducing-irmin-graphql>.


How viable is delivering binaries linked to Cygwin to Windows 
customers?
════════════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/how-viable-is-delivering-binaries-linked-to-cygwin-to-windows-customers/4775>


mbacarella asked
────────────────

  I’m in the early stages of planning a deliverable binary product 
  that
  will run on Linux, Mac and Windows.

  My brief sniff of the air around the OCaml ecosystem says I 
  should
  expect to target Cygwin to get Windows going (although there’s
  impressive work to get native Windows stuff done that can become 
  the
  preferred approach in a few years).

  My experience using Cygwin as an operating environment is that 
  it’s
  pretty darn sluggish compared to Linux on the same computer.

  Why is this? There’s an anecdote that says Cygwin can only fork 
  at
  about 30-50x a second on Windows, due to how it has to adapt it 
  to
  work within Windows’ task spawning model. (For contrast, Linux 
  can
  achieve thousands of forks per second if you play around with 
  it).

  I understand from another product developer that when they build
  binaries to deliver to Windows/Cygwin, they actually 
  cross-compile on
  Linux because of how slowly the toolchain runs on Cygwin.

  That sounds like bad news if you want to do UNIXy things, but 
  for a
  single standalone application this might not be so bad? I assume 
  if I
  ship a deliverable to Windows/Cygwin, the end user may enjoy 
  good
  performance, so long as I’m not spawning tons of processes or 
  relying
  on fork for multi-programming. Is this a safe assumptions?

  Any other gotchas when it comes to OCaml on Cygwin w.r.t. 
  performance?

  The app pretty much has real-time gaming requirements (though 
  it’s not
  a game so can side-step worrying about access to GPUs and
  what-not). Stated another way, although my application will 
  depend on
  the POSIX layer offered by Cygwin, I expect it not to crunch 
  POSIX
  related stuff in the main loop.

  How has your experience gone?


John Whitington replied
───────────────────────

  I have been shipping commercial binaries for Linux (32 and 64 
  bit),
  Windows (32 and 64bit) and OS X for years. For example:
  <https://github.com/coherentgraphics/cpdf-binaries>

  And even static or shared libraries in binary form:
  <https://github.com/coherentgraphics/cpdflib-binary>

  On OS X, you need to use MACOSX_DEPLOYMENT_TARGET or similar to 
  make
  sure your builds will run on older systems. And, in fact, you 
  need to
  use MACOSX_DEPLOYMENT_TARGET when asking OPAM to compile the 
  OCaml
  compiler itself. And, you will need to deal with codesigning and
  notarization. But it’s all doable.

  For linux, you may need to build under older linux versions, to 
  make
  sure that the glibc in use is old enough. This is not an
  ocaml-specific problem. I have a 64 bit and 32 bit VM with 
  old-ish
  glibc versions for this purpose.

  Under Windows, there are no such backward-compatibility 
  problems. I
  use the new OCaml for windows system, which comes with OPAM, and 
  is
  mingw-based. No cygwin remains in the final binary.

  For more obscure systems (AIX, HPUX, Sparc etc) customers 
  compile from
  source (with help from me). Not once in more than ten years has 
  anyone
  cared that it was written in OCaml.


dbuenzli also replied
─────────────────────

  remember that on the Windows native port, the Unix module 
  distributed
  with OCaml is your POSIX compatibility layer. There are a few 
  entry
  points to avoid though, the list is at the bottom of [this 
  page].


[this page] 
<https://caml.inria.fr/pub/docs/manual-ocaml/libunix.html>


nojb also replied
─────────────────

  At LexiFi our main application is developed and shipped on 
  Windows. We
  use the msvc port of OCaml. This means that you need Cygwin to
  develop, but the resulting application is fully native and does 
  not
  depend on the Cygwin DLL. As @dbuenzli mentioned, the Unix 
  module *is*
  the POSIX compatibility layer.

  Compilation speed is slower on Windows because process creation 
  is
  slower on Windows as a general rule, but it is manageable (our
  application has around 2000 modules + Js_of_ocaml + C bindings + 
  C#
  component).

  We don’t have any issues with runtime performance. The `Unix' 
  library
  mentioned above implements Windows support directly without 
  going
  through any compatibility layer and is quite efficient.


BikalGurung also replied
────────────────────────

  There is an editor being built in ocaml/reasonml which currently
  targets windows, linux and macos -
  <https://github.com/onivim/oni2>. However, the binary is native
  windows rather than cygwin derivative. So if you don’t have to 
  use
  cygwin dependencies then native windows binary could be the way 
  to go.

  Also esy - <https://github.com/esy/esy> makes developing
  ocaml/reasonml on windows viable.


keleshev also replied
─────────────────────

  *TLDR*: Install the [Mingw port of OCaml 4], freely use most 
  opam
   libraries, and compile to native Windows binaries, without 
   licensing
   issues.

  I recommend you read the “Release notes for Windows”:
  <https://github.com/ocaml/ocaml/blob/trunk/README.win32.adoc>

  To summarise, there are three Windows ports:

  • Native Microsoft port,
  • Native Mingw port,
  • Cygwin port.

  All three require Cygwin for development purposes. I recommend 
  using
  the Native Mingw, as:

  • it *doesn’t* require Visual Studio (it uses a mingw fork of 
  GCC that
    “cross-compiles” native Windows executables),
  • it *doesn’t* rely on the dreaded cygwin.dll
  • it has good opam support with opam-repository-mingw:
    <https://github.com/fdopen/opam-repository-mingw>
  • it has a convenient installer:
    <https://fdopen.github.io/opam-repository-mingw/> 5.

  To contrast, Native Microsoft requires Visual Studio, and 
  doesn’t have
  opam. You can still vendor pure OCaml packages, but as soon as 
  you
  want to use some C bindings you’re in trouble, because of the 
  “minor”
  differences between Visual C and GCC. And everything assumes GCC
  nowadays.

  Cygwin port is the one I don’t have experience with, but 
  re-reading
  the “Release notes for Windows” above it strikes me that it 
  mentions
  that Cygwin was re-licensed from GPL to LGPL with static linking
  exception. So it looks like the Cygwin port could be viable for
  commercial use, but I never tried to statically linked 
  `cygwin.dll',
  and I’m not sure what are the benefits of Cygwin port over the 
  Mingw
  port.


[Mingw port of OCaml 4]
<https://fdopen.github.io/opam-repository-mingw/>


dmbaturin also replied
──────────────────────

  With [soupault 4], I decided to ship prebuilt binaries for all
  platforms including Windows. Mostly to see if I can, all its 
  users I
  know of are on UNIX-like systems and know how to build from 
  source,
  but that’s beside the point. :wink:

  I can confirm everything @keleshev says: fdopen’s package just 
  works,
  opam works exactly like it does on UNIX, pure OCaml libraries 
  are
  trivial to install, and the binaries don’t depend on cygwin. 
  Note
  that “opam switch create” also just works, you can install 
  either
  MinGW or MSVC compiler versions as opam switches.  I only ever 
  start
  the Windows VM to make release builds, and the workflow is 
  exactly the
  same as on Linux where I’m actually writing code.

  My only obstacle on that path was that FileUtils lost its 
  Windows
  compatibility, but I wanted to use it, so I worked with 
  @gildor478 to
  make it cross-platform again. Uncovered a bug in the 
  implementation of
  Unix.utimes in the process, but it’s hardly a commonly used 
  function.

  You can also setup AppVeyor builds. It’s not as simple as I wish 
  it
  would be, but there are projects doing it that you can steal the 
  setup
  from.

  There’s also opam-cross-windows, but it’s very incomplete and 
  needs
  work to be practical. There are no big obstacles, it just needs
  work. While files in opam-repository-mingw are normally 
  identical to
  the default opam repository, the cross one needs small 
  adjustments in
  every package to specify the toolchain to use, so the required 
  work is
  mostly a lot of trivial but manual actions. I hope eventually it
  reaches parity with fdopen’s one and we’ll be able to easily 
  build for
  Windows without ever touching Windows.

  As of static Linux builds, @JohnWhitington’s approach can work, 
  but
  there’s a better option if you don’t need anything from glibc
  specifically and don’t link against any C libs: build statically 
  with
  musl. There’s a `+musl+static+flambda' compiler flavour. You 
  need musl
  and gcc-musl to install it, but after that, just build with 
  `-ccopt
  -static' flag and you get a binary that doesn’t depend on 
  anything.


[soupault 4] <https://soupault.neocities.org/>


Dune 2.0.0
══════════

  Archive: <https://discuss.ocaml.org/t/ann-dune-2-0-0/4758>


rgrinberg announced
───────────────────

  On behalf of the dune team, I’m delighted to announce the 
  release of
  dune 2.0. This release is the culmination of 4 months of hard 
  work by
  the dune team and contains new features, bug fixes, and 
  performance
  improvements . Here’s a selection of new features that I 
  personally
  find interesting:

  • New boostrap procedure that works in low memory environments
  • (`deprecated_library_name' ..) stanza to properly deprecate 
  old
    library names
  • (`foreign_library' ..) stanza to define C/C++ libraries.
  • C stubs directly in OCaml executables

  Refer to the change log for an exhaustive list.

  We strive for a good out of the box experience that requires no
  configuration, so we’ve also tweaked a few defaults. In 
  particular, `$
  dune build' will now build `@all' instead of `@install', and
  ocamlformat rules are setup by default.

  Lastly, dune 2.0 sheds all the legacy related to jbuilder and 
  will no
  longer build jbuilder projects. This change is necessary to ease
  maintenance and make it easier to add new features down the
  line. There are a few other minor breaking changes. Refer to the
  change log for the full list. We apologize in advance for any
  convenience this might cause.

  [Changelog]


[Changelog] <https://discuss.ocaml.org/t/ann-dune-2-0-0/4758>


Advanced C binding using ocaml-ctypes and dune
══════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/advanced-c-binding-using-ocaml-ctypes-and-dune/4805>


toots announced
───────────────

  I worked on a socket.h binding last summer and had a great 
  experience
  integrating ocaml-ctypes with dune, I thought that might be of
  interest to other developers so I wrote about it:
  <https://medium.com/@romain.beauxis/advanced-c-binding-using-ocaml-ctypes-and-dune-cc3f4cbab302>


rgrinberg replied
─────────────────

  This is a good article. I encourage anyone who writes C bindings 
  with
  ctypes to study it carefully.

  A little bit of advice to shorten your dune files:

  ┌────
  │ (deps    (:gen ./gen_constants_c.exe))
  └────

  This line isn’t necessary. Dune is smart enough to know that 
  running a
  binary in a rule incurs a dependency on it.

        dune has a truly amazing [support for cross-compiling],
        which we do not cover here, but, unfortunately, its
        primitives for building and executing binaries do not yet
        cover this use case.

  Indeed, we don’t have any primitives for running binaries on the
  target platform. Perhaps we should add some. However, we do in 
  fact
  have some features in dune to solve this concrete cross 
  compilation
  problem. As far as I understand, the goal is to obtain some 
  compile
  time values such as #define constants and field offsets for the 
  target
  platform. This does not in fact require to run anything on the 
  cross
  compilation target. In configurator, we have a primitive
  `C_define.import' to extract this information. The end result is 
  that
  these configurator scripts are completely compatible with cross
  compilation.

  Perhaps this could be generalized to work with ctypes generators 
  as
  well?

  Funny bit of trivia: The hack in configurator required to do 
  this is
  in fact something I extracted from ctypes itself. The original 
  author
  is [whitequark], who in turn wrote it to make ctypes itself 
  amendable
  to cross compilation.


[support for cross-compiling]
<https://dune.readthedocs.io/en/latest/cross-compilation.html>

[whitequark] <https://github.com/whitequark>


emillon then added
──────────────────

        This does not in fact require to run anything on the cross
        compilation target. In configurator, we have a primitive
        `C_define.import' to extract this information. The end
        result is that these configurator scripts are completely
        compatible with cross compilation.

  If anybody wants to know more about this bit, I wrote an article 
  about
  this last year: 
  <https://dune.build/blog/configurator-constants/>


Upcoming breaking change in Base/Core v0.14
═══════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/upcoming-breaking-change-in-base-core-v0-14/4806>


bcc32 announced
───────────────

  We’re changing functions in Base that used to use the 
  polymorphic
  variant type `[ `Fst of 'a | `Snd of 'b ]' to use `('a, 'b) 
  Either.t'
  instead. As well as enabling the use of all of the functions in 
  the
  Either module, this makes the functions consistent with other
  functions that already use `Either.t', (currently just
  `Set.symmetric_diff')

  The following functions’ types will change:
  • `Result.ok_fst'
  • `List.partition_map'
  • `Map.partition_map', `Map.partition_mapi'
  • `Hashtbl.partition_map', `Hashtbl.partition_mapi'

  The type of List.partition3_map will not change:

  ┌────
  │ val partition3_map
  │   :  'a t
  │   -> f:('a -> [ `Fst of 'b | `Snd of 'c | `Trd of 'd ])
  │   -> 'b t * 'c t * 'd t
  └────

  We don’t have a generic ternary variant, and it doesn’t seem 
  worth it
  to mint one just for this purpose.

  Since this change is pretty straightforward, we expect that a 
  simple
  find/replace will be sufficient to update any affected call 
  sites.


CI/CD Pipelines: Monad, Arrow or Dart?
══════════════════════════════════════

  Archive: 
  <https://roscidus.com/blog/blog/2019/11/14/cicd-pipelines/>


Thomas Leonard announced
────────────────────────

  In this post I describe three approaches to building a language 
  for
  writing CI/CD pipelines. My first attempt used a monad, but this
  prevented static analysis of the pipelines. I then tried using 
  an
  arrow, but found the syntax very difficult to use. Finally, I 
  ended up
  using a light-weight alternative to arrows that I will refer to 
  here
  as a dart (I don’t know if this has a name already). This allows 
  for
  static analysis like an arrow, but has a syntax even simpler 
  than a
  monad.

  <https://roscidus.com/blog/blog/2019/11/14/cicd-pipelines/>


Use of functors to approximate F# statically resolved type 
parameters
═════════════════════════════════════════════════════════════════════

  Archive:
  <https://discuss.ocaml.org/t/use-of-functors-to-approximate-f-statically-resolved-type-parameters/4782>


cmxa asked
──────────

  I am learning OCaml coming from F#. In F#, to calculate the 
  average of
  an array whose element type supports addition and division, one 
  can
  write

  ┌────
  │ let inline average (arr: 'a[]) : 'a
  │     when ^a : (static member DivideByInt : ^a * int -> ^a)
  │     and  ^a : (static member (+) : ^a * ^a -> ^a)
  │     and  ^a : (static member Zero : ^a)
  │     =
  │     if Array.length arr = 0 then 
  (LanguagePrimitives.GenericZero) else
  │     LanguagePrimitives.DivideByInt (Array.fold (+) 
  (LanguagePrimitives.GenericZero) arr) (Array.length arr)
  └────

  My understanding is that in OCaml, one would have a module type 
  like
  so:

  ┌────
  │ module type Averagable = sig
  │   type 'a t
  │
  │   val divide_by_int : 'a -> int -> 'a
  │   val plus : 'a -> 'a -> 'a
  │   val zero : 'a
  │ end
  └────

  My question is how the corresponding function would be written:

  ┌────
  │ let average arr =
  │   ???
  └────


smolkaj replied
───────────────

  First, `Averagable' should look like this:

  ┌────
  │ module type Averagable = sig
  │   type t
  │   val divide_by_int : t -> int -> t
  │   val plus : t -> t -> t
  │   val zero : t
  │ end
  └────

  Then average will look something like this:

  ┌────
  │ let average (type t) (module A : Averagable with type t = t) 
  (arr : t array) : t =
  │   Array.fold ~init:A.zero ~f:A.plus arr
  └────

  (The code above uses Jane Street’s Base/Core library.)


ivg then added
──────────────

  While @smolkaj’s answer is a correct and direct implementation 
  of your
  F# code, it might be nicer if your code can interplay with 
  existing
  abstractions in the OCaml infrastructure. For example,

  ┌────
  │ open Base
  │
  │ let average (type a) (module T : Floatable.S with type t = a) 
  xs =
  │   Array.fold ~init:0. ~f:(fun s x -> s +. T.to_float x) xs /.
  │   Float.of_int (Array.length xs)
  └────

  and now it could be used with any existing numeric data in 
  Base/Core

  ┌────
  │ average (module Int) [|1;2;3;4|];;
  │ - : Base.Float.t = 2.5
  └────

  and even adapted to non-numbers,

  ┌────
  │ let average_length = average (module struct
  │     include String
  │     let to_float x = Float.of_int (String.length x)
  │     let of_float _ = assert false
  │   end)
  └────

  The latter example shows that we requested more interface than 
  need, a
  cost that we have to pay for using an existing definition. In 
  cases
  when it matters, you can specify the specific interface, e.g.,

  ┌────
  │ module type Floatable = sig
  │   type t
  │   val to_float : t -> float
  │ end
  │
  │ let average (type a) (module T : Floatable with type t = a) xs 
  =
  │   Array.fold ~init:0. ~f:(fun s x -> s +. T.to_float x) xs /.
  │   Float.of_int (Array.length xs)
  └────

  But we reached the point where using first class modules is 
  totally
  unnecessary. Our interface has only one function, so the 
  following
  definition of average, is much more natural

  ┌────
  │ let average xs ~f =
  │   Array.fold ~init:0. ~f:(fun s x -> s +. f x) xs /.
  │   Float.of_int (Array.length xs)
  └────

  it has type `'a array -> f:('a -> float) -> float' and computes 
  an
  average of `f x_i' for all elements in the array.


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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

[Alan Schmitt]

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Hello

Here is the latest OCaml Weekly News, for the week of December 03 
to 10,
2019.

Table of Contents
─────────────────

Internships at Nomadic-labs
Interesting OCaml Articles
Next OUPS meetup December 18th 2019
Old CWN


Internships at Nomadic-labs
═══════════════════════════

  Archive: 
  <https://discuss.ocaml.org/t/internship-at-nomadic-labs/4819>


Julien Tesson announced
───────────────────────

  Nomadic Labs is currently looking for students with an interest 
  in
  functional programming for internships that would take place in 
  our
  offices in Paris or Grenoble.

  We have a catalog of internships topics available at [1] The
  internships topics are mainly addressed to master student but 
  other
  well motivated application will be considered.

  A first selection phase on received résumé will occur on 
  december
  15th.  Please contact us at contact@nomadic-labs.com by 
  specifying
  which topics in the catalog you're interested in.

  [1]: <https://nomadic-labs.com/download/internship_catalog.pdf>

  Please, feel free to redistribute widely.


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

  Archive:
  <https://discuss.ocaml.org/t/interesting-ocaml-articles/1867/57>


james woodyatt announced
────────────────────────

  Found on *Lobste.rs*: Mark Karpov writes yet another [Haskell
  vs. OCaml] for old time's sake. I found it worth a read and a 
  mention
  here.

  p.s. He spends a bit of time in the intro lamenting the lack of 
  a
  conventional Unicode string library for OCaml, and I feel that 
  pain
  acutely, especially since I'm the author of an *unconventional* 
  one,
  i.e. the [Ucs_text] module in my [Orsetto] project.


[Haskell vs. OCaml] 
<https://markkarpov.com/post/haskell-vs-ocaml.html>

[Ucs_text]
<https://bitbucket.org/jhw/orsetto/src/default/src/ucs/ucs_text.mli>

[Orsetto] <https://bitbucket.org/jhw/orsetto>


Next OUPS meetup December 18th 2019
═══════════════════════════════════

  Archive:
  <https://sympa.inria.fr/sympa/arc/caml-list/2019-12/msg00009.html>


Bruno Bernardo announced
────────────────────────

  The OUPS meetup is back. The next one will take place on 
  Wednesday,
  December 18, 7pm at IRILL on the Jussieu campus. As usual, we 
  will
  have a few talks, followed by pizzas and drinks.

  The talks will be the following:

  • Nathan Rebours, The future of OCaml-PPX

  • Guillaume Claret, coq-of-ocaml
    (<https://clarus.github.io/coq-of-ocaml/>)

  And possibly a third talk. Contact us if you want to present
  something, especially if you have a small project you want to 
  show in
  10-15min.

  To register, or for more information, go here:
  <https://www.meetup.com/ocaml-paris/events/267019458>

  *Registration is required! Access is not guaranteed after 7pm if
  you're not registered.* (It also helps us to order the right 
  amount of
  food.)

  Access map:
  IRILL - Université Pierre et Marie Curie (Paris VI)
  Barre 15-16 1er étage
  4 Place Jussieu
  75005 Paris
  <https://www.irill.org/pages/access.html>


Old CWN
═══════

  If you happen to miss a CWN, you can [send me a message] and 
  I'll mail
  it to you, or go take a look at [the archive] or the [RSS feed 
  of the
  archives].

  If you also wish to receive it every week by mail, you may 
  subscribe
  [online].

  [Alan Schmitt]


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

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

[RSS feed of the archives] 
<http://alan.petitepomme.net/cwn/cwn.rss>

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

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


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