[cwn] Attn: Development Editor, Latest OCaml Weekly News

Alan Schmitt Mon, 16 Sep 2019 23:47:14 -0700

Hello

Here is the latest OCaml Weekly News, for the week of September 10 to

17, 2019.


Table of Contents
─────────────────

OCaml 4.09.0+beta2
chartjs: OCaml bindings for Chart.js charting library
How does one print any type?
Interesting OCaml Articles
Dune 2.0.0 coming soon!
Old CWN


OCaml 4.09.0+beta2
══════════════════

 Archive:
 <https://sympa.inria.fr/sympa/arc/caml-list/2019-09/msg00010.html>


Florian Angeletti announced
───────────────────────────

The release of OCaml 4.09.0 is approaching. We have created a second beta version to help you adapt your softwares to the new features

 ahead of the release.

This new beta integrates in particular the fixes from 4.08.1 that were not yet part of the first beta due to the overlap between the release

 of 4.08.1 and the first beta.

If you tried to test the first beta, and were stopped by the lack of

 working dune and ocamlfind, those issues has been fixed.

 The source code is available at these addresses:

 • <https://github.com/ocaml/ocaml/archive/4.09.0+beta2.tar.gz>

• <https://caml.inria.fr/pub/distrib/ocaml-4.09/ocaml-4.09.0+beta2.tar.gz>

The compiler can also be installed as an OPAM switch with one of the

 following commands.

 ┌────

│ opam switch create ocaml-variants.4.09.0+beta2 --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git

 └────

 or

 ┌────

│ opam switch create ocaml-variants.4.09.0+beta2+<VARIANT> --repositories=default,beta=git+https://github.com/ocaml/ocaml-beta-repository.git

 └────

 where you replace <VARIANT> with one of these:
 • afl
 • default-unsafe-string
 • flambda
 • fp
 • fp+flambda

 We want to know about all bugs. Please report them here:
 <https://github.com/ocaml/ocaml/issues>

 Happy hacking

 — Florian "octachron" Angeletti, for the OCaml team


OCaml 4.09.0
╌╌╌╌╌╌╌╌╌╌╌╌

 (Changes that can break existing programs are marked with a "*")


◊ Code generation and optimizations:

• #2278: Remove native code generation support for 32-bit Intel macOS, iOS and other Darwin targets. (Mark Shinwell, review by Nicolas

   Ojeda Bar and Xavier Leroy)

• #8507: Shorten symbol names of anonymous functions in Flambda mode (the directory portions are now hidden) (Mark Shinwell, review by

   Nicolás Ojeda Bär)

 • #7931, #1904: Add FreeBSD/aarch64 support (Greg V, review by

Sébastien Hinderer, Stephen Dolan, Damien Doligez and Xavier Leroy)

• #8547: Optimize matches that are an affine function of the input.

   (Stefan Muenzel, review by Alain Frisch, Gabriel Scherer)

• #8681, #8699, #8712: Fix code generation with nested let rec of functions. (Stephen Dolan, Leo White, Gabriel Scherer and Pierre Chambart, review by Gabriel Scherer, reports by Alexey Solovyev and

   Jonathan French)


◊ Compiler user-interface and warnings:

• * #2276: Remove support for compiler plugins and hooks (also adds [Dynlink.unsafe_get_global_value]) (Mark Shinwell, Xavier Clerc, review by Nicolás Ojeda Bär, Florian Angeletti, David Allsopp and

   Xavier Leroy)

• #2301: Hint on type error on int literal (Jules Aguillon, review by Nicolás Ojeda Bär , Florian Angeletti, Gabriel Scherer and Armaël

   Guéneau)

 • #2309: New options -with-runtime and -without-runtime in

ocamlopt/ocamlc that control the inclusion of the runtime system in the generated program. (Lucas Pluvinage, review by Daniel Bünzli,

   Damien Doligez, David Allsopp and Florian Angeletti)

• #2314: Remove support for gprof profiling. (Mark Shinwell, review

   by Xavier Clerc and Stephen Dolan)

• #3819, #8546 more explanations and tests for illegal permutation

   (Florian Angeletti, review by Gabriel Scherer)

• #8537: fix the -runtime-variant option for bytecode (Damien Doligez,

   review by David Allsopp)

• #8541: Correctly print multi-lines locations (Louis Roché, review by

   Gabriel Scherer)

 • #8579: Better error message for private constructors of an

extensible variant type (Guillaume Bury, review by many fine eyes)



◊ Compiler distribution build system:

• #2267: merge generation of header programs, also fixing parallel build on Cygwin. (David Allsopp, review by Sébastien Hinderer)

• #8514: Use boot/ocamlc.opt for building, if available. (Stephen

   Dolan, review by Gabriel Scherer)


◊ Internal/compiler-libs changes:

• #1579: Add a separate types for clambda primitives (Pierre Chambart,

   review by Vincent Laviron and Mark Shinwell)

• #1965: remove loop constructors in Cmm and Mach (Vincent Laviron)

• #1973: fix compilation of catches with multiple handlers (Vincent

   Laviron)

• #2190: fix pretty printing (using Pprintast) of "lazy …" patterns and "fun (type t) -> …" expressions. (Nicolás Ojeda Bär, review by

   Gabriel Scherer)

• #2228, #8545: refactoring the handling of .cmi files by moving the logic from Env to a new module Persistent_env (Gabriel Scherer,

   review by Jérémie Dimino and Thomas Refis)

• #2229: Env: remove prefix_idents cache (Thomas Refis, review by

   Frédéric Bour and Gabriel Scherer)

 • #2237, #8582: Reorder linearisation of Trywith to avoid a call

instruction (Vincent Laviron and Greta Yorsh, additional review by Mark Shinwell; fix in #8582 by Mark Shinwell, Xavier Leroy and Anil

   Madhavapeddy)

• #2265: Add bytecomp/opcodes.mli (Mark Shinwell, review by Nicolas

   Ojeda Bar)

• #2268: Improve packing mechanism used for building compilerlibs modules into the Dynlink libraries (Mark Shinwell, Stephen Dolan,

   review by David Allsopp)

 • #2277: Use newtype names as type variable names (Matthew Ryan)

• #2280: Don't make more Clambda constants after starting Cmmgen (Mark

   Shinwell, review by Vincent Laviron)

 • #2281: Move some middle-end files around (Mark Shinwell)

• #2283: Add [is_prefix] and [find_and_chop_longest_common_prefix] to

   [Misc.Stdlib.List] (Mark Shinwell, review by Alain Frisch and
   Stephen Dolan)

• #2284: Add various utility functions to [Misc] and remove functions from [Misc.Stdlib.Option] that are now in [Stdlib.Option] (Mark

   Shinwell, review by Thomas Refis)

• #2286: Functorise [Consistbl] (Mark Shinwell, review by Gabriel

   Radanne)

• #2291: Add [Compute_ranges] pass (Mark Shinwell, review by Vincent

   Laviron)

• #2292: Add [Proc.frame_required] and [Proc.prologue_required]. Move tail recursion label creation to [Linearize]. Correctly position [Lprologue] relative to [Iname_for_debugger] operations. (Mark

   Shinwell, review by Vincent Laviron)

• #2308: More debugging information on [Cmm] terms (Mark Shinwell,

   review by Stephen Dolan)

 • #7878, #8542: Replaced TypedtreeIter with tast_iterator (Isaac
   "Izzy" Avram, review by Gabriel Scherer and Nicolás Ojeda Bär)

• #8598: Replace "not is_nonexpansive" by "maybe_expansive". (Thomas Refis, review by David Allsopp, Florian Angeletti, Gabriel Radanne,

   Gabriel Scherer and Xavier Leroy)


◊ Runtime system:

• #1725, #2279: Deprecate Obj.set_tag and Obj.truncate (Stephen Dolan,

   review by Gabriel Scherer, Damien Doligez and Xavier Leroy)

 • #2075, #7729: rename _T macro used to support Unicode in the

(Windows) runtime in order to avoid compiler warning (Nicolás Ojeda

   Bär, review by Gabriel Scherer and David Allsopp)

• * #2240: Constify "identifier" in struct custom_operations (Cedric

   Cellier, review by Xavier Leroy)

• #2250: Remove extra integer sign-extension in compare functions

   (Stefan Muenzel, review by Xavier Leroy)

 • * #2293: Constify "caml_named_value" (Stephen Dolan, review by
   Xavier Leroy)

• #8607: Remove obsolete macros for pre-2002 MSVC support (Stephen

   Dolan, review by Nicolás Ojeda Bär and David Allsopp)

 • #8656: Fix a bug in [caml_modify_generational_global_root]
   (Jacques-Henri Jourdan, review by Gabriel Scherer)

• #8787, #8788: avoid integer overflow in caml_output_value_to_bytes

   (Jeremy Yallop, report by Marcello Seri)


◊ Standard library:

• #2262: take precision (.<n>) and flags ('+' and ' ') into account in

   printf %F (Pierre Roux, review by Gabriel Scherer)

 • #6148, #8596: optimize some buffer operations (Damien Doligez,

reports by John Whitington and Alain Frisch, review by Jeremy Yallop

   and Gabriel Scherer)


◊ Other libraries:

• #2112: Fix Thread.yield unfairness with busy threads yielding to each other. (Andrew Hunter, review by Jacques-Henri Jourdan, Spiros

   Eliopoulos, Stephen Weeks, & Mark Shinwell)

 • #7903, #2306: Make Thread.delay interruptible by signals again

(Xavier Leroy, review by Jacques-Henri Jourdan and Edwin Török)

• #2248: Unix alloc_sockaddr: Fix read of uninitialized memory for an unbound Unix socket. Add support for receiving abstract (Linux) socket paths. (Tim Cuthbertson, review by Sébastien Hinderer and

   Jérémie Dimino)

• #2289: Delete the vmthreads library. This library was deprecated in

   4.08.0.  (Jérémie Dimino)

• #2318: Delete the graphics library. This library is now available as

   a separate "graphics" package in opam. Its new home is:
   <https://github.com/ocaml/graphics> (Jérémie Dimino, review by
   Nicolas Ojeda Bar, Xavier Leroy and Sébastien Hinderer)


◊ Tools:

• #2221: ocamldep will now correctly allow a .ml file in an include directory that appears first in the search order to shadow a .mli appearing in a later include directory. (Nicolás Ojeda Bär, review

   by Florian Angeletti)


◊ Manual and documentation:

• #8757: Rename Pervasives to Stdlib in core library documentation.

   (Ian Zimmerman, review by David Allsopp)

• #7584, #8538: Document .cmt* files in the "overview" of ocaml{c,opt}

   (Oxana Kostikova, rewiew by Florian Angeletti)

• #8515: manual, precise constraints on reexported types (Florian

   Angeletti, review by Gabriel Scherer)


◊ Bug fixes:

 • #7156, #8594: make top level use custom printers if they are
   available (Andrew Litteken, report by Martin Jambon, review by

Nicolás Ojeda Bär, Thomas Refis, Armaël Guéneau, Gabriel Scherer,

   David Allsopp)
 • #3249: ocamlmklib should reject .cmxa files (Xavier Leroy)

• #7937, #2287: fix uncaught Unify exception when looking for type

   declaration (Florian Angeletti, review by Jacques Garrigue)

• #2296: Fix parsing of hexadecimal floats with underscores in the

   exponent.  (Hugo Heuzard and Xavier Leroy, review by Gabriel
   Scherer)

• #8610, #8613: toplevel printing, consistent deduplicated name for

   types (Florian Angeletti, review by Thomas Refis and Gabriel
   Scherer, reported by Xavier Clerc)

• #8635, #8636: Fix a bad side-effect of the -allow-approx option of

   ocamldep. It used to turn some errors into successes (Jérémie
   Dimino)

• #8701, #8725: Variance of constrained parameters causes principality issues (Jacques Garrigue, report by Leo White, review by Gabriel

   Scherer)

• #8777(partial): fix position information in some polymorphic variant error messages about missing tags (Florian Angeletti, review by

   Thomas Refis)

• #8779, more cautious variance computation to avoid missing cmis (Florian Angeletti, report by Antonio Nuno Monteiro, review by Leo

   White)

• #8800: Fix soundness bug in extension constructor inclusion (Leo

   White, review by Jacques Garrigue)

• #8810: Env.lookup_module: don't allow creating loops (Thomas Refis,

   report by Leo White, review by Jacques Garrigue)

 • #8848: Fix x86 stack probe CFI information in caml_c_call and
   caml_call_gc (Tom Kelly, review by Xavier Leroy)

• #8864, #8865: Fix native compilation of left shift by (word_size - 1) (Vincent Laviron, report by Murilo Giacometti Rocha, review by

   Xavier Leroy)

• #8862, #8871: subst: preserve scopes (Thomas Refis, report by Leo

   White, review by Jacques Garrigue)

• #8921, #8924: Fix stack overflow with Flambda (Vincent Laviron,

   review by Pierre Chambart and Leo White, report by Aleksandr
   Kuzmenko)


chartjs: OCaml bindings for Chart.js charting library
═════════════════════════════════════════════════════

 Archive:
 
<https://discuss.ocaml.org/t/ann-chartjs-ocaml-bindings-for-chart-js-charting-library/4363/1>


Alex announced
──────────────

 I'm pleased to announce `chartjs', OCaml bindings for [Chart.js]

charting library and its popular extensions. The library relies on

 `js_of_ocaml' bindings for browser API and follows `js_of_ocaml'
 [guides] for binding a JavaScript library.

 Line, bar, horizontal bar, pie and doughnut charts are currently
 supported.  The bindings are not full yet, some chart types and
 plugins are to be added later.

 • Installation: `opam install chartjs'.
 • Repository: <https://github.com/monstasat/chartjs-ocaml>
 • Library sage examples:
   <https://github.com/monstasat/chartjs-ocaml/tree/master/examples>
 • Online documentation and examples:
   <https://monstasat.github.io/chartjs-ocaml>

Some auxiliary libraries are available providing bindings for popular

 Chart.js plugins:
 • `chartjs-annotation'
 • `chartjs-streaming'
 • `chartjs-datalabels'
 • `chartjs-colorschemes'

 These libraries are also available via opam.

 Any feedback is highly appreciated.


[Chart.js] <http://chartjs.org>

[guides] <https://ocsigen.org/js_of_ocaml/dev/manual/bindings>


How does one print any type?
════════════════════════════

 Archive:
 <https://discuss.ocaml.org/t/how-does-one-print-any-type/4362/1>


Pinocchio asked
───────────────

I just want to print any type (like a print statement in python). I am just learning ocaml using the ocaml command interactively with my

 script basically. How do I do this?


Alex replied
────────────

 You may also use the [ppx_deriving.show] plugin from the

[ppx_deriving] library. This plugin is able to generate `'a -> string' and `Format.formatter -> 'a -> unit' (where `'a' is the type you want

 to print) functions which can then be used for value printing.

 ┌────
 │ type t =
 │ {  number : int
 │ ;  text : string
 │ }[@@deriving show]
 └────

This will produce a `show' and `pp' functions of type `t -> string'

 and `Format.formatter -> t -> unit', which can then be used as

 ┌────
 │ let v = { number = 2; text = "Hello world"} in
 │ print_endline (show v)
 └────

 or

 ┌────
 │ let v = { number = 2; text = "Hello world"} in
 │ let s = Format.asprintf "%a" pp v in
 │ print_endline s
 └────

Of course, you can always define such functions for the needed types

 by yourself.

 As I can see, almost every library introducing a new type also

provides pretty-printing (kinda `pp' in this example) functions out of

 the box.


[ppx_deriving.show]
<https://github.com/ocaml-ppx/ppx_deriving#plugin-show>

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


progman also replied
────────────────────

 The same basic printing as the toplevel can be had with:

[http://github.com/progman1/genprintlib ] (general value printing in

 compiled code)

Available through the official opam repository: opam install genprint



[http://github.com/progman1/genprintlib ]
<http://github.com/progman1/genprintlib>


Ivan Gotovchits also replied
────────────────────────────

 There is no such facility in OCaml. OCaml is not an interpreted

language with a dynamic type system. When a program is compiled all types are erased, so it is impossible in runtime to reflect a value to its type. And yes, as you've already pointed out, when you interact with OCaml using interactive toplevel there is some generic printing facility, but this is a very special case because you're not really

 running a program, but interactively compile it.

So, you have to accept this fact and learn how to program in OCaml using OCaml ways of doing things. First of all, learn how to use the `Format.printf' function. This is a generic function that takes the

 `format' specification and arguments and prints them, e.g.,

 ┌────
 │ open Format
 │
 │ let () =
 │   printf "Hello, %s world\n%!" "cruel";
 │   printf "Hello, %d times!\n%!" 42
 └────

 As you can see, the special format specifiers, like `%s' or `%d'

specify the type of an argument. So `%d' expects one argument of type `int', and `%s' expects one of `string', there is also `%c' for `char'

 , `%b' for `bool' and so on.

 There is also a generic `%a' specifier, which expects not one
 argument, but two – a function, that will tell how to print the
 argument, and the argument itself. It is used to print values of
 abstract types, hence the name `%a'. There is a convention, that

modules that define abstract types also provide a function called `pp'

 which specifies how this value should be printed, e.g.,

 ┌────
 │ let () = printf "Hello, abstract student %a\n%!" Student.pp s
 └────

 Where the `Student' module might be defined as

 ┌────
 │ struct Student : sig
 │    type t
 │    val create : string -> int -> t
 │    val pp : Format.formatter -> t -> unit
 │ end = struct
 │    type t = {name : string; cls : int}
 │    let create name cls  = {name; cls}
 │    let pp ppf {name; cls} =
 │       Format.fprintf ppf "%s of %d" name cls
 │ end
 └────

 That is roughly how we print everything in OCaml :)


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

 Archive:
 <https://discuss.ocaml.org/t/interesting-ocaml-articles/1867/50>


Yotam Barnoy said
─────────────────

 
<https://tarides.com/blog/2019-09-13-decompress-experiences-with-ocaml-optimization.html>


Ryan Slade also said
────────────────────

Interesting performance comparison with quite a few languages when

 writing a user space network driver:

 <https://github.com/ixy-languages/ixy-languages>


Dune 2.0.0 coming soon!
═══════════════════════

Archive: <https://discuss.ocaml.org/t/dune-2-0-0-coming-soon/4102/2>



Jérémie Dimino announced
────────────────────────

 Update: after thinking about this more and working more towards

preparing Dune 2.0.0, we made the following changes compared to this

 post:

• The source code of Dune itself will remain compatible with the last 3 released versions of OCaml rather than just the last one. i.e. if

   4.08 is the last released version of OCaml when Dune 2.0.0 is

released then Dune 2.0.0 will be guaranteed to build with OCaml 4.06, 4.07 and 4.08. We still plan to provide an easy way to install

   Dune 2.0.0 in older opam switches

• Dune 2.0.0 will not be able to read jbuild files at all. Only `dune upgrade' will still be able to read them in order to upgrade them



Old CWN
═══════

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 [Alan Schmitt]


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