[cwn] Attn: Development Editor, Latest OCaml Weekly News
Alan Schmitt
alan.schmitt at polytechnique.org
Tue Nov 1 04:55:59 PDT 2022
Hello
Here is the latest OCaml Weekly News, for the week of October 25 to
November 01, 2022.
Table of Contents
─────────────────
What are pros and cons of Eliom web framework?
Domain-shims: an implementation of `Domain` for OCaml 4 (beta version)
OCaml Platform Installer alpha release
geojson and geojsone
Other OCaml News
Old CWN
What are pros and cons of Eliom web framework?
══════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/what-are-pros-and-cons-of-eliom-web-framework/10658/7>
Deep in the thread, ZAN DoYe said
─────────────────────────────────
I’ve made a cjkv info app with eliom, the old demo version is
here(most of its functions are turned off and hidden):
<https://cjkv.smaji.org/> It collects variation, source info, input
method code of characters among China, Japan, Korea, Vietnam,
Hongkong, Taiwan, ethnic minorities and ancient books. e.g.
<https://cjkv.smaji.org/search/4ee4>
<https://cjkv.smaji.org/char_list?step=16&offset=184032&stop=191471&start=183984>
Overall, eliom framework is fantastic. All the links are
eliom_service, its parameters and itself are typed. Session manage is
powerful and flexible. Components are reactive with each other,
seamlessly between server and client. An app written in eliom is
intrinsically an SSR SPA, an integral whole.
Writing an eliom app, all I want to say is: damn! it’s too good!
Cons:
╌╌╌╌╌
• dune support
• merlin, ocaml-language-server
Your project is built by a manually managed Makefile and merln/lsp
support is broken when you mix client/server code together in the
same folder.
You only get these supports when you write standalone server and
client separately.
But these flaws can be overcome. I wrote a custom code translator,
which generates server code and client code from an eliom file into
separate folder and make them still work together seamlessly. And in
this case, I don’t need a Makefile, dune and ocaml-lsp works as
normal projects.
• ocsigenserver
It’s good. But it updates infrequently and doesn’t keep pace with
other libraries closely. Because eliom depends on it and its
dependence constraint sometimes requires old libraries, better
create a separate opam switch when working with an eliom project.
Wart
╌╌╌╌
In fact, it’s not a wart of eliom. It’s lwt
<https://github.com/mirage/ocaml-cohttp/issues/545> That’s why I stop
working on the old demo and now rewriting it again with another tec
stack.
…
╌
If only eliom depended on lwt/async optionally and came with an
official code translator to overcome the dune/lsp integration issue.
Domain-shims: an implementation of `Domain` for OCaml 4 (beta version)
══════════════════════════════════════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/domain-shims-an-implementation-of-domain-for-ocaml-4-beta-version/10706/1>
gasche announced
────────────────
I just wrote a small package, `domain-shims', that provides a
non-multicore implementation of the new `Domain' module of the OCaml 5
standard library:
repository: <https://gitlab.com/gasche/domain-shims>
the one source file:
<https://gitlab.com/gasche/domain-shims/-/blob/trunk/lib/domain.ml>
This is a fun hack, but it may also be useful for people who write
some code using `Domain' to test it under OCaml 5, but still want to
be able to build and run their project using their normal OCaml 4
setup.
I haven’t put a version number and made a formal release yet.
The main limitation of the library is that it does not implement the
`Effect' module providing effect handlers, so it is not true that all
OCaml 5 code will be compatible. I discuss this in more details in the
[README # no effect support], quoted below:
OCaml 5 also provides effect handlers as a new `Effect'
module of the standard library. We do not provide an
implementation of `Effect', which is much harder to
emulate using regular OCaml 4.
Someone could experiment with an implementation using the
[delimcc] library for delimited control. (Please do this
and report! It is probably fun.) We expect that the result
would be much slower than the OCaml 5 implementation,
probably by an order of magnitude. This would be okay for
toy experiments. But it would not be good enough to
seriously run libraries relying on effect handlers for
performance-sensitive operations, such as Domainslib or
Eio.
The other option would be to implement shim versions of
Effect-using libraries. We are considering providing a
shim for Domainslib in particular, which is very easy to
do without emulating effects at all. This general approach
sounds scary (no limit to the number of programs you need
to provide shims for), but remember that OCaml 5 users are
not supposed to use effect handlers too much yet, it was
only made available for lightweight concurrent schedulers.
Happy hacking :-)
[README # no effect support]
<https://gitlab.com/gasche/domain-shims#no-effect-support>
[delimcc] <https://opam.ocaml.org/packages/delimcc/>
OCaml Platform Installer alpha release
══════════════════════════════════════
Archive:
<https://discuss.ocaml.org/t/ann-ocaml-platform-installer-alpha-release/10652/5>
Deep in this thread, Hannes Mehnert asked and Paul-Elliot replied
─────────────────────────────────────────────────────────────────
Hello Hannes and thanks for your interest!
do you have machine-readable data what went into the
binaries that are being downloaded (i.e. which version of
what) [nowadays the buzzword is “Software Bill of
Materials] – NB: and opam switch export –full –freeze is a
good start for the opam packages
In fact, currently only the `ocaml-platform' binary is being
downloaded. The tools are then compiled in a sandbox switch on the
local machine, and cached in a local opam repository. Only the version
of OCaml and of the tool is kept as info in the local cache.
do you have security in mind? the curl | sudo bash is not
very nice from a security perspective, since that may do
any harm.
We do have security in mind! We wanted a one line copy-paste
installation for new users. So, we went for an install script,
although we will consider your advice on setting up a package
repository!
is there an update path? when I run your installer, how to
upgrade to the latest version of “platform installer” (can
I check whether an update is available and what will
change?)?
Currently, the update path is simply to re-run the install script:
┌────
│ bash < <(curl -sL https://github.com/tarides/ocaml-platform-installer/releases/latest/download/installer.sh)
└────
But there is no way to know if there is a new release, apart from
checking the github releases page. Thanks a lot for the inputs! I’ll
reach out to you soon by private message, as your work and experience
on reproducible builds might help for the ongoing remote repo!
geojson and geojsone
════════════════════
Archive:
<https://discuss.ocaml.org/t/ann-geojson-and-geojsone/10738/1>
Patrick Ferris announced
────────────────────────
On behalf of the [geocaml] org, I’m happy to announce the first
release of [geojson and geojsone].
[geocaml] <https://github.com/geocaml>
[geojson and geojsone] <https://github.com/geocaml/ocaml-geojson>
What is GeoJSON?
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
GeoJSON is defined in [RFC7946] as
…a geospatial data interchange format based on JavaScript
Object Notation (JSON).
It is a schema for writing geospatial information in JSON often as
some combination of “geometries” (e.g. a Point or a Polygon). These
are all using the [World Geodetic System 1984 (WGS84)] coordinate
reference system.
[RFC7946] <https://www.rfc-editor.org/rfc/rfc7946>
[World Geodetic System 1984 (WGS84)]
<https://en.wikipedia.org/wiki/World_Geodetic_System#1984_version>
An example
╌╌╌╌╌╌╌╌╌╌
A collections of features where the first feature contains a single
point.
┌────
│ {
│ "type": "FeatureCollection",
│ "features": [
│ {
│ "type": "Feature",
│ "properties": {
│ "name": "Place du Capitole"
│ },
│ "geometry": {
│ "coordinates": [
│ 1.4433418775990958,
│ 43.60443107383625
│ ],
│ "type": "Point"
│ }
│ }
│ ]
│ }
└────
Geojson Library
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
The `geojson' library provides functions for reading and writing
GeoJSON objects. You must, however, provide a simple interface for the
JSON library of your choosing. This was a design decision made to
offer better support for using the library in the browser. You can
[read more about it in the documentation].
[read more about it in the documentation]
<https://github.com/geocaml/ocaml-geojson#geojson>
Geojsone Library
╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
The `geojsone' library is inspired by the [jsonm] library. It vendors
jsonm and ports it to a non-blocking implementation provided using
effects. Internally it then reconstructs [ezjsonm] using [eio] dubbed
`ezjsone'. The purpose of this library is to deal with the fact that
GeoJSON documents can be quite big. It should be considered quite
experimental. I did a [little bit of benchmarking] and it seemed to
suggest that effects helps lower the memory usage (sometimes…).
[jsonm] <https://erratique.ch/software/jsonm>
[ezjsonm] <https://github.com/mirage/ezjsonm>
[eio] <https://github.com/ocaml-multicore/eio>
[little bit of benchmarking]
<https://github.com/geocaml/ocaml-geojson/pull/49#issuecomment-1242945412>
Thanks
╌╌╌╌╌╌
Thanks to all of the Outreachy applicants that helped with this
library and in particular @IIITM-Jay who did some work at the start of
his Outreachy internship on the library.
Other OCaml News
════════════════
>From the ocaml.org blog
───────────────────────
Here are links from many OCaml blogs aggregated at [the ocaml.org
blog].
• [The MirageOS Retreat: A Journey of Food, Cats, and Unikernels]
[the ocaml.org blog] <https://ocaml.org/blog/>
[The MirageOS Retreat: A Journey of Food, Cats, and Unikernels]
<https://tarides.com/blog/2022-10-28-the-mirageos-retreat-a-journey-of-food-cats-and-unikernels>
Old CWN
═══════
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[Alan Schmitt]
[send me a message] <mailto:alan.schmitt at polytechnique.org>
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[Alan Schmitt] <https://alan.petitepomme.net/>
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