From dennis.raddle at gmail.com  Mon Oct  2 01:15:58 2023
From: dennis.raddle at gmail.com (Dennis Raddle)
Date: Sun, 1 Oct 2023 18:15:58 -0700
Subject: [Haskell-cafe] two HLS processes with same name
In-Reply-To: <67E4C3EF-9E22-4584-8519-7D661E51B241@mac.com>
References: <CAKxLvopcXMLPPj12ab5H6oTr23qoFBZgBmBCxaZeaUc5uARUKQ@mail.gmail.com>
 <67E4C3EF-9E22-4584-8519-7D661E51B241@mac.com>
Message-ID: <CAKxLvorDBH8g=UjXZwd9LNqOp4QpMD7QPqV5LbGeqjE+htQ-LA@mail.gmail.com>

When I don't open that extra file, the one time I tested it, there was now
only one hls process, so I guess that was it! Easy to fix then.
D


On Sat, Sep 30, 2023 at 3:09 PM Jeff Clites <jclites at mac.com> wrote:

> Stack treats files outside a project as being in a default project (or at
> least, `stack ghci` sessions outside a project are treated that way), so
> that might be it.
>
> Jeff
>
> On Sep 30, 2023, at 6:01 PM, Dennis Raddle <dennis.raddle at gmail.com>
> wrote:
>
> 
> Thanks, Tom. I only have one stack project open, but I do have a single hs
> file open from outside that project, usually. That single hs file does not
> reside in a stack project tree. I'll try running VS Code with and without
> that single hs file.
>
> D
>
>
>
> On Sat, Sep 30, 2023 at 1:56 AM Tom Ellis <
> tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk> wrote:
>
>> On Sat, Sep 30, 2023 at 01:51:01AM -0700, Dennis Raddle wrote:
>> > When I first run VS Code on a Haskell workspace, there is one
>> > process called "haskell-language-server-9.2.8".  Eventually another
>> > process, taking an additional 1 GB, joins it. The two processes have
>> > the same name.
>> >
>> > Is it supposed to work like this?
>>
>> I use Emacs, not VS Code, but when I have two
>> "haskell-language-server" processes it's because I have opened a
>> second project.  Is it possible that's happened for you?
>>
>> For a hacky way to explore what's going on you could kill one of the
>> processes and see what complains.
>>
>> Tom
>> _______________________________________________
>> Haskell-Cafe mailing list
>> To (un)subscribe, modify options or view archives go to:
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>> Only members subscribed via the mailman list are allowed to post.
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
>
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From exarkun at twistedmatrix.com  Mon Oct  2 13:47:13 2023
From: exarkun at twistedmatrix.com (Jean-Paul Calderone)
Date: Mon, 2 Oct 2023 09:47:13 -0400
Subject: [Haskell-cafe] Taking over maintainership of `fec`
In-Reply-To: <CAEeXt4N7cRfYu+P0Ln2faxSGDqCe0_P9Y=8pmMzZ7H+2+H3zhA@mail.gmail.com>
References: <CAEeXt4MKmvoDo5uZByyMmrmRf=Czabj_Zpbz6rdXMKY4TtsTVQ@mail.gmail.com>
 <ZRLx3WxhXecr6weo@straasha.imrryr.org>
 <CAEeXt4P4k=jbi3XMNgBhcL-e=-krDJw_7=w4cuquDBdGZ1qW8w@mail.gmail.com>
 <ZRMb2i5xLdqwo6nW@straasha.imrryr.org>
 <CAEeXt4N7cRfYu+P0Ln2faxSGDqCe0_P9Y=8pmMzZ7H+2+H3zhA@mail.gmail.com>
Message-ID: <CAEeXt4MTiDOs=RhtCc7Mg0OvbSzm6tp3_rkoHtMa9mN6OPRbqw@mail.gmail.com>

On Wed, Sep 27, 2023 at 8:56 AM Jean-Paul Calderone <
exarkun at twistedmatrix.com> wrote:

> On Tue, Sep 26, 2023 at 1:59 PM Viktor Dukhovni <ietf-dane at dukhovni.org>
> wrote:
>
>> On Tue, Sep 26, 2023 at 01:05:05PM -0400, Jean-Paul Calderone wrote:
>>
>> > > On Tue, Sep 26, 2023 at 09:37:46AM -0400, Jean-Paul Calderone wrote:
>> > >
>> > > > I have emailed the current maintainer and original author of the
>> Haskell
>> > > > bindings, Adam Langley (cced), about becoming a maintainer but I
>> haven't
>> > > > yet heard back.
>> > >
>> > > I didn't know AGL was (in the past?) a Haskeller.  If he hasn't
>> > > responded in the meantime, I'll reach out via office email, to ask
>> > > whether he's inclined to continue to maintain the "fec" package.
>> > >
>> >
>> > Thanks Viktor, that would be wonderful.
>>
>> Adam's response:
>>
>>     Thanks. After 15 years they're welcome to take it over
>>
>>
> Great news, thanks Viktor.  According to
> https://wiki.haskell.org/Taking_over_a_package there are certain steps
> Adam should take to make this official, but I'll see if the Hackage admins
> are satisfied with this thread or not.
>

Viktor,

I would be grateful if I could impose on you to give this one more little
push.  Do you think you could ask Alex to email hackage-admin at haskell.org
saying "I would like jcalderone to take over the fec package"?  He could
probably even just forward this email.

Much appreciated,
Jean-Paul


>
>> --
>>     Viktor.
>> _______________________________________________
>> Haskell-Cafe mailing list
>> To (un)subscribe, modify options or view archives go to:
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>> Only members subscribed via the mailman list are allowed to post.
>
>
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From branimir.maksimovic at gmail.com  Tue Oct  3 04:46:02 2023
From: branimir.maksimovic at gmail.com (Branimir Maksimovic)
Date: Tue, 3 Oct 2023 06:46:02 +0200
Subject: [Haskell-cafe] two HLS processes with same name
In-Reply-To: <CAKxLvorxUtcxTDw47d2XEAOQvLufEPwsCsSo9H6ws66cr2ePQQ@mail.gmail.com>
References: <CAKxLvorxUtcxTDw47d2XEAOQvLufEPwsCsSo9H6ws66cr2ePQQ@mail.gmail.com>
Message-ID: <1243E146-1868-4DBC-9526-9BFB75C761C4@gmail.com>

macOS needs just 1-2GiB of wired RAM, don’t worry…

> On 30. 9. 2023., at 10:51, Dennis Raddle <dennis.raddle at gmail.com> wrote:
> 
> I'm running the HLS plugin in VS Code on MacOS, on an M2 Apple Silicon MacBook Pro. My computer is running low on RAM and the HLS process seems to be fairly large for me (over 1 GB).  When I first run VS Code on a Haskell workspace, there is one process called "haskell-language-server-9.2.8". Eventually another process, taking an additional 1 GB, joins it. The two processes have the same name.
> 
> Is it supposed to work like this?
> 
> Note about Apple Silicon FYI: I bought this computer in June with 16 GB Integrated RAM. RAM is very expensive in a SoC. I'm discovering that a lot of programs are memory hogs, not sure if it's the latest MacOS or M2, but between running software development stuff and music-related apps, I'm running out of RAM. I just bought a similar MacBook but with 32 GB RAM, and will sell the current one. So eventually I won't worry about an extra GB process or two.
> Dennis
> 
> 
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.


From capn.freako at gmail.com  Tue Oct  3 11:02:39 2023
From: capn.freako at gmail.com (David Banas)
Date: Tue, 3 Oct 2023 07:02:39 -0400
Subject: [Haskell-cafe] Meaning of fizzled sparks?
Message-ID: <B316A1BE-4578-4CE1-9BD3-C04A160A8C6B@gmail.com>

Hi all,

If this code:

  f5Rslts      = map (f5 (n-1) startingMinScore startingMaxScore (otherColor clr) 0) newBoards `using` parList rdeepseq
  totalMoves   = sum $ map snd f5Rslts  -- Attempt at parallelization yielded no perf. improvement.

is yielding a fizzled spark ratio of about 0.3,
does it imply that the sum begins pulling from the list, before the sparks have had a chance to compute the first third of the list elements?

Thanks,
-db

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From capn.freako at gmail.com  Tue Oct  3 11:07:51 2023
From: capn.freako at gmail.com (David Banas)
Date: Tue, 3 Oct 2023 07:07:51 -0400
Subject: [Haskell-cafe] Meaning of "GC waiting" in ThreadScope?
Message-ID: <BA31576A-DD4F-4B16-9B97-F984D589F6E1@gmail.com>

Hi all,

When viewing the result of my code execution in ThreadScope,
What does it imply when there’s a great amount of time spent in the “GC waiting” phase, but only short little blips of time spent in the “GC” phase?

Thanks,
-db

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From meng.wang at bristol.ac.uk  Tue Oct  3 21:42:01 2023
From: meng.wang at bristol.ac.uk (Meng Wang)
Date: Tue, 3 Oct 2023 21:42:01 +0000
Subject: [Haskell-cafe] CFP,
 PEPM 2024 ACM SIGPLAN Workshop on Partial Evaluation and Program
 Manipulation
In-Reply-To: <PAXPR06MB83573CFBB1A0124F32B5F77AABEEA@PAXPR06MB8357.eurprd06.prod.outlook.com>
References: <PAXPR06MB83573CFBB1A0124F32B5F77AABEEA@PAXPR06MB8357.eurprd06.prod.outlook.com>
Message-ID: <PAXPR06MB8357BA110819EC3C59C19D23ABC4A@PAXPR06MB8357.eurprd06.prod.outlook.com>

Dear Haskellers,

A gentle reminder that the submission deadline is in two weeks.

Best regards,
Gabriele Keller (Utrecht University, Netherlands)
Meng Wang (University of Bristol, UK)


From: Meng Wang <meng.wang at bristol.ac.uk>
Date: Thursday, 7 September 2023 at 08:52
To: haskell-cafe at haskell.org <haskell-cafe at haskell.org>, haskell at haskell.org <haskell at haskell.org>
Cc: g.k.keller at uu.nl <g.k.keller at uu.nl>
Subject: CFP, PEPM 2024 ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation
Dear Haskellers,

Gabriele and I are organising PEPM this year. Over the years, PEPM has grown into a conference of general PL topics and Haskell/FP is strongly represented. We look forward to receiving your submissions.

Best regards,
Gabriele Keller (Utrecht University, Netherlands)
Meng Wang (University of Bristol, UK)


----------------------------------------------------------------------------------------------------------
**
**    CALL FOR PAPERS
**
**    PEPM at POPL 2024
**    Workshop on PARTIAL EVALUATION AND PROGRAM MANIPULATION
**    16th of January 2024, London, United Kingdom
**
**    Submission Deadline:
**    18 October 2023
**
**    https://popl24.sigplan.org/home/pepm-2024
**    https://easychair.org/conferences/?conf=pepm24
**
-----------------------------------------------------------------------------------------------------------

ACM SIGPLAN Workshop on PARTIAL EVALUATION AND PROGRAM MANIPULATION (PEPM) 2024
===============================================================================

  * Website : https://popl24.sigplan.org/home/pepm-2024
  * Time    : 16th January 2024
  * Place   : London, United Kingdom
              (co-located with POPL 2024)

The ACM SIGPLAN Workshop on Partial Evaluation and Program
Manipulation (PEPM) has a history going back to 1991 and has been
co-located with POPL every year since 2006. It originated with the
discoveries of useful automated techniques for evaluating
programs with only partial input. Over the years, the scope of PEPM
has expanded to include a variety of research areas centred around the
theme of semantics-based program manipulation — the systematic
exploitation of treating programs not only as subjects to black-box
execution but also as data structures that can be generated,
analysed, and transformed while establishing or maintaining important
semantic properties.

Scope
-----

In addition to the traditional PEPM topics (see below), PEPM 2024
welcomes submissions in new domains, in particular:

  * Semantics based and machine-learning based program synthesis and
    program optimisation.

  * Modelling, analysis, and transformation techniques for distributed
    and concurrent protocols and programs, such as session types,
    linear types, and contract specifications.

More generally, topics of interest for PEPM 2024 include, but are not
limited to:

  * Program and model manipulation techniques such as:
    supercompilation, partial evaluation, fusion, on-the-fly program
    adaptation, active libraries, program inversion, slicing, symbolic
    execution, refactoring, decompilation, and obfuscation.

  * Techniques that treat programs/models as data objects including
    metaprogramming, generative programming, embedded domain-specific
    languages, program synthesis by sketching and inductive
    programming, staged computation, and model-driven program
    generation and transformation.

  * Program analysis techniques that are used to drive program/model
    manipulation such as: abstract interpretation, termination
    checking, binding-time analysis, constraint solving, type systems,
   automated testing and test case generation.

  * Application of the above techniques including case studies of
    program manipulation in real-world (industrial, open-source)
    projects and software development processes, descriptions of
    robust tools capable of effectively handling realistic
    applications, benchmarking. Examples of application domains
    include legacy program understanding and transformation, DSL
    implementations, visual languages and end-user programming,
    scientific computing, middleware frameworks and infrastructure
    needed for distributed and web-based applications, embedded and
    resource-limited computation, and security.

This list of categories is not exhaustive, and we encourage
submissions describing new theories and applications related to
semantics-based program manipulation in general. If you have a
question as to whether a potential submission is within the scope of
the workshop, please contact the programme co-chairs, Gabriele Keller
(g.k.keller at uu.nl<mailto:g.k.keller at uu.nl>) and Meng Wang (meng.wang at bristol.ac.uk<mailto:meng.wang at bristol.ac.uk>).

Submission categories and guidelines
------------------------------------

Three kinds of submissions will be accepted:

  * Regular Research Papers should describe new results, and will be
    judged on originality, correctness, significance, and clarity.
    Regular research papers must not exceed 12 pages.

  * Short Papers may include tool demonstrations and presentations of
    exciting if not fully polished research, and of interesting
    academic, industrial, and open-source applications that are new or
    unfamiliar. Short papers must not exceed 6 pages.

  * Talk Proposals may propose lectures about topics of interest for PEPM,
    existing work representing relevant contributions, or promising
    contributions that are not mature enough to be proposed as papers of
    the other categories. Talk Proposals must not exceed 2 pages.


References and appendices are not included in page limits. Appendices
may not necessarily be read by reviewers. Both kinds of submissions should
be typeset using the two-column ‘sigplan’ sub-format of the new ‘acmart’
format available at:

  http://sigplan.org/Resources/Author/

and submitted electronically via EasyChair:

  https://easychair.org/conferences/?conf=pepm24

Reviewing will be single-blind.

Submissions are welcome from PC members (except the two co-chairs).

Accepted regular research papers will appear in formal proceedings
published by ACM, and be included in the ACM Digital Library.
Accepted short papers do not constitute formal publications and will
not appear in the proceedings.

At least one author of each accepted contribution must attend the
workshop (physically or virtually) and present the work. In the case
of tool demonstration papers, a live demonstration of the described
tool is expected.

Important dates
---------------

  * Paper submission deadline : **Wednesday 18th October 2023 (AoE)**
  * Author notification       : **Wednesday 15th November 2023 (AoE)**
  * Workshop                  : **Tuesday 16th January 2024**

Best paper award
----------------

PEPM 2024 continues the tradition of a Best Paper award. The winner will be
announced at the workshop.

Programme committee
-------------------

* Chairs: Gabriele Keller (Utrecht University, Netherlands)
                Meng Wang (University of Bristol, UK)

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From benl at ouroborus.net  Wed Oct  4 11:50:35 2023
From: benl at ouroborus.net (Ben Lippmeier)
Date: Wed, 4 Oct 2023 22:50:35 +1100
Subject: [Haskell-cafe] Meaning of fizzled sparks?
In-Reply-To: <B316A1BE-4578-4CE1-9BD3-C04A160A8C6B@gmail.com>
References: <B316A1BE-4578-4CE1-9BD3-C04A160A8C6B@gmail.com>
Message-ID: <5B946939-570A-44C7-A894-0BFFBBEEAF95@ouroborus.net>



> On 3 Oct 2023, at 10:02 pm, David Banas <capn.freako at gmail.com> wrote:
> 
> Hi all,
> 
> If this code:
> 
>   f5Rslts      = map (f5 (n-1) startingMinScore startingMaxScore (otherColor clr) 0) newBoards `using` parList rdeepseq
>   totalMoves   = sum $ map snd f5Rslts  -- Attempt at parallelization yielded no perf. improvement.
> 
> is yielding a fizzled spark ratio of about 0.3,
> does it imply that the sum begins pulling from the list, before the sparks have had a chance to compute the first third of the list elements?

A fizzed spark is when the user code indicated that some thunk could be run in parallel, but it didn’t end up being run in parallel because by the time it was inspected it was already evaluated. Fizzed sparks are described in “Runtime Support for Multicore Haskell”, Marlow, Peyton Jones, Singh, ICFP 2009.

It’s hard to tell what is happening without the code for ‘f5’, though probably 30% of results produced by ‘f5’ are already values (not thunks) so they cannot be evaluated in parallel by the ‘parList’ strategy.

Ben.
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From abela at chalmers.se  Fri Oct  6 13:53:39 2023
From: abela at chalmers.se (Andreas Abel)
Date: Fri, 6 Oct 2023 15:53:39 +0200
Subject: [Haskell-cafe] [ANNOUNCE] Agda 2.6.4
In-Reply-To: <CAOUWSGAVBiFYvOAjG+XqQWxJFARbt8mHC4Mk74x0ogU4FeFHuw@mail.gmail.com>
References: <CAOUWSGAVBiFYvOAjG+XqQWxJFARbt8mHC4Mk74x0ogU4FeFHuw@mail.gmail.com>
Message-ID: <d0fe3a4c-f460-4396-bc1c-3c8ce659d244@chalmers.se>

Dear all,

The Agda Team is very pleased to announce the release of Agda 2.6.4.

Thanks to everyone who gave us feedback on the release candidates!

# Highlights of Agda 2.6.4

* Cubical Agda now displays boundary conditions in interactive mode
       (PR [#6529](https://github.com/agda/agda/pull/6529)).

* An inconsistency in the treatment of large indices has been fixed
       (Issue [#6654](https://github.com/agda/agda/issues/6654)).

* Unfolding of definitions can now be fine-controlled via `opaque` 
definitions.

* Additions to the sort system: `LevelUniv` and `Propω`.

* New flag `--erasure` with several improvements to erasure (declared 
run-time irrelevance).

* New reflection primitives for meta-programming.

# GHC supported versions

Agda 2.6.4 has been tested with GHC 9.6.3, 9.4.7, 9.2.8, 9.0.2, 8.10.7, 
8.8.4 and 8.6.5 on Linux, macOS and Windows.

# Installation

Agda 2.6.4 can be installed using cabal-install or stack:

1. Getting the tarball

         $ cabal update
         $ cabal get Agda-2.6.4
         $ cd Agda-2.6.4

2. a. Using cabal-install

         $ cabal install -f +optimise-heavily -f +enable-cluster-counting

2. b. Using stack

         $ stack --stack-yaml stack-a.b.c.yaml install --flag 
Agda:optimise-heavily --flag Agda:enable-cluster-counting

replacing `a.b.c` with your version of GHC.

The flags mean:

     - optimise-heavily:
       Turn on extra optimisation for a faster Agda.
       Takes large resources during compilation of Agda.

     - enable-cluster-counting:
       Enable unicode clusters for alignment in the LaTeX backend.
       Requires the ICU lib to be installed and known to pkg-config.

These flags can be dropped from the install if causing trouble.

# Standard library

You can use standard library v1.7.2 or the `master` branch of the
standard library with Agda 2.6.4.  This branch is available at

         https://github.com/agda/agda-stdlib/

# Fixed issues over Agda 2.6.3

   https://hackage.haskell.org/package/Agda-2.6.4/changelog


Enjoy Agda!

Andreas, on behalf of the Agda Team
_______________________________________________
Agda mailing list
Agda at lists.chalmers.se
https://lists.chalmers.se/mailman/listinfo/agda

From allbery.b at gmail.com  Sun Oct  8 15:17:49 2023
From: allbery.b at gmail.com (Brandon Allbery)
Date: Sun, 8 Oct 2023 11:17:49 -0400
Subject: [Haskell-cafe] =?utf-8?q?XMonad_for_Wayland_=E2=80=94_seeking_hel?=
	=?utf-8?q?p?=
Message-ID: <CAKFCL4Uorbn_XrR0OcHyVcrH_-mMkaiVbMZ9VtcxFnCPuSVH3g@mail.gmail.com>

We on the XMonad devteam (Tomáš, Tony, Yecine, and myself) have been
collecting contributions for the past two years with an eye toward paying
someone to work on a port of XMonad to Wayland, since none of us is up to
the task. We think we now have enough contributions coming in monthly to
pay for someone to work with us on it.

Problem is, we have no idea who can do this. So this is a call for help,
looking for someone who can write it. There is an existing project
<https://github.com/L-as/waymonad> but it’s badly bitrotted, including
using a very old and buggy version of wlroots
<https://gitlab.freedesktop.org/wlroots>, and L-as has had little time to
revisit it. It’s not clear that it’s worth revisiting.

One problem that’s unlikely to be solvable is that Wayland programs don’t
set distinct identifiers that a manageHook could use, so the appName and
className hooks can’t be ported. We welcome information to the contrary,
though.

So, help? Comments and especially proposals welcome on the Discourse thread
<https://discourse.haskell.org/t/xmonad-for-wayland-call-for-help/7812>.

-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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From ben at well-typed.com  Mon Oct  9 22:18:24 2023
From: ben at well-typed.com (Ben Gamari)
Date: Mon, 09 Oct 2023 18:18:24 -0400
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
Message-ID: <87ttqzignm.fsf@smart-cactus.org>


The GHC developers are very pleased to announce the availability of the
final release of GHC 9.8.1. Binary distributions, source
distributions, and documentation are available at downloads.haskell.org:

    https://downloads.haskell.org/ghc/9.8.1

GHC 9.8 brings a number of new features and improvements, including:

 * Preliminary support the `TypeAbstractions` language extension,
   allowing types to be bound in type declarations [TypeAbstractions].

 * Support for the `ExtendedLiterals` extension, providing syntax for
   non-word-sized numeric literals in the surface language
   [extended-literals]

 * Improved rewrite rule matching behavior, allowing limited matching of
   higher-order patterns

 * Better support for user-defined warnings by way of the `WARNING`
   pragma [warnings]

 * The introduction of the new `GHC.TypeError.Unsatisfiable`
   constraint, allowing more predictable user-defined type errors
   [unsatisfiable]

 * Implementation of the export deprecation proposal, allowing module
   exports to be marked with `DEPRECATE` pragmas [deprecated-exports]

 * The addition of build semaphore support for parallel compilation;
   with coming support in `cabal-install` this will allow better use of
   parallelism in multi-package builds [jsem]

 * More efficient representation of info table provenance information,
   reducing binary sizes by over 50% in some cases when
   `-finfo-table-map` is in use

A full accounting of changes can be found in the [release notes][].
Plans for GHC's future releases can be found on the [GHC Wiki][status].

We would like to thank GitHub, IOG, the Zw3rk stake pool,
Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell
Foundation, and other anonymous contributors whose on-going financial
and in-kind support has facilitated GHC maintenance and release
management over the years. Finally, this release would not have been
possible without the hundreds of open-source contributors whose work
comprise this release.

Happy compiling,

~ Ben


[TypeAbstractions]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-decl-invis-binders.rst
[extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst
[unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-unsatisfiable.rst
[warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst
[deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-deprecating-exports-proposal.rst
[jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-jsem.rst
[release notes]: https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html
[status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status
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From hecate at glitchbra.in  Mon Oct  9 22:59:14 2023
From: hecate at glitchbra.in (hecate at glitchbra.in)
Date: Mon, 09 Oct 2023 22:59:14 +0000
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <87ttqzignm.fsf@smart-cactus.org>
References: <87ttqzignm.fsf@smart-cactus.org>
Message-ID: <1e3c2c825d38b7312a5452bc3a367227af41a580@glitchbra.in>

Congratulations, this is a very exciting release! 

10 octobre 2023 à 00:18 "Ben Gamari" <ben at well-typed.com> a écrit:


> 
> The GHC developers are very pleased to announce the availability of the
> final release of GHC 9.8.1. Binary distributions, source
> distributions, and documentation are available at downloads.haskell.org:
> 
>  https://downloads.haskell.org/ghc/9.8.1
> 
> GHC 9.8 brings a number of new features and improvements, including:
> 
>  * Preliminary support the `TypeAbstractions` language extension,
>  allowing types to be bound in type declarations [TypeAbstractions].
> 
>  * Support for the `ExtendedLiterals` extension, providing syntax for
>  non-word-sized numeric literals in the surface language
>  [extended-literals]
> 
>  * Improved rewrite rule matching behavior, allowing limited matching of
>  higher-order patterns
> 
>  * Better support for user-defined warnings by way of the `WARNING`
>  pragma [warnings]
> 
>  * The introduction of the new `GHC.TypeError.Unsatisfiable`
>  constraint, allowing more predictable user-defined type errors
>  [unsatisfiable]
> 
>  * Implementation of the export deprecation proposal, allowing module
>  exports to be marked with `DEPRECATE` pragmas [deprecated-exports]
> 
>  * The addition of build semaphore support for parallel compilation;
>  with coming support in `cabal-install` this will allow better use of
>  parallelism in multi-package builds [jsem]
> 
>  * More efficient representation of info table provenance information,
>  reducing binary sizes by over 50% in some cases when
>  `-finfo-table-map` is in use
> 
> A full accounting of changes can be found in the [release notes][].
> Plans for GHC's future releases can be found on the [GHC Wiki][status].
> 
> We would like to thank GitHub, IOG, the Zw3rk stake pool,
> Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell
> Foundation, and other anonymous contributors whose on-going financial
> and in-kind support has facilitated GHC maintenance and release
> management over the years. Finally, this release would not have been
> possible without the hundreds of open-source contributors whose work
> comprise this release.
> 
> Happy compiling,
> 
> ~ Ben
> 
> [TypeAbstractions]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-decl-invis-binders.rst
> [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst
> [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-unsatisfiable.rst
> [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst
> [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-deprecating-exports-proposal.rst
> [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-jsem.rst
> [release notes]: https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html
> [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status
> 
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>

From zoran.bosnjak at via.si  Tue Oct 10 10:45:00 2023
From: zoran.bosnjak at via.si (Zoran =?utf-8?Q?Bo=C5=A1njak?=)
Date: Tue, 10 Oct 2023 10:45:00 +0000 (UTC)
Subject: [Haskell-cafe] ambiguous type variable question
Message-ID: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>

Hi all,
I want to convert a type level structure to the value level structure of the same shape.
This is the simplified example:

{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE UndecidableInstances #-}

module Test where

import GHC.TypeLits
import Data.Kind
import Data.Proxy

-- This data structure serves both for 'type level' and 'value level'.
data Content n s b
    = ContentRaw
    | ContentTable [(n, s)]
    | ContentBool b

deriving instance (Show n, Show s, Show b) => Show (Content n s b)

-- Convert from types to values.
class IsSchema s where
    type SchemaVal s :: Type
    schema :: SchemaVal s

instance IsSchema 'ContentRaw where
    type (SchemaVal 'ContentRaw) = Content Integer String Bool
    schema = ContentRaw

instance IsSchema ('ContentTable '[]) where
    type (SchemaVal ('ContentTable '[])) = Content Integer String Bool
    schema = ContentTable []

instance
    ( IsSchema ('ContentTable ts)
    , t ~ '(n, s), KnownNat n, KnownSymbol s
    , SchemaVal ('ContentTable ts) ~ Content Integer String Bool
    ) => IsSchema ('ContentTable (t ': ts)) where
    type SchemaVal ('ContentTable (t ': ts)) = Content Integer String Bool
    schema = case schema @('ContentTable ts) of
        ContentTable lst ->
            let n = natVal (Proxy @n)
                s = symbolVal (Proxy @s)
            in ContentTable ((n,s) : lst)
        _ -> error "internal error"

If I remove the type parameter 'b', 'ContentBool b' and coresponding 'Bool' from the sample, the conversion works as expected.

>>> schema @'ContentRaw
ContentRaw

>>> schema @('ContentTable ( '(1,"test1") ': '(2,"test2") ': '[]))
ContentTable [(1,"test1"),(2,"test2")]

But for some reason, as soon as I extend the example with 'b' and 'Bool' as shown above, it results in the following error:

    * Could not deduce (SchemaVal ('ContentTable ts)
                        ~ Content Integer String b0)
      from the context: (IsSchema ('ContentTable ts), t ~ '(n, s),
                         KnownNat n, KnownSymbol s,
                         SchemaVal ('ContentTable ts) ~ Content Integer String Bool)
        bound by the instance declaration at test2.hs:(34,5)-(37,43)
      The type variable `b1' is ambiguous

How do I fix it or how do I rewrite it to get the intended result?

regards,
Zoran

From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Tue Oct 10 11:34:36 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Tue, 10 Oct 2023 12:34:36 +0100
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
Message-ID: <ZSU2zCPDYmeJBV6n@cloudinit-builder>

On Tue, Oct 10, 2023 at 10:45:00AM +0000, Zoran Bošnjak wrote:
> I want to convert a type level structure to the value level structure of the same shape.
> This is the simplified example:
[...]
> If I remove the type parameter 'b', 'ContentBool b' and coresponding 'Bool' from the sample, the conversion works as expected.

The problem is that you have constraints

    IsSchema ('ContentTable ts)  and  SchemaVal ('ContentTable ts)

but `ContentTable ts` is of kind `Content n s b` , for some `n` , `s`
and `b`.  The instance is claiming that it works for all `b` , but it
doesn't!  Your instance only works when the `ContentTable ts` is of
kind `Content Nat Symbol Bool`.  The `b` is invisible in the type
siganture so it's hard to see that it is the problem!

In fact it's really weird because you'll get errors like

    Could not deduce SchemaVal (ContentTable ts) ~ Content Integer String Bool
    from the context: SchemaVal (ContentTable ts) ~ Content Integer String Bool
      
which look like they should immediately be satisfied!  Instead what it
means is

    Could not deduce SchemaVal (ContentTable ts :: Content n s b) ~ Content Integer String Bool
    from the context: SchemaVal (ContentTable ts :: Content Nat Symbol Bool) ~ Content Integer String Bool

Fixing `b` solves the problem, for example:

instance
  ( IsSchema ('ContentTable ts :: Content Nat Symbol Bool),
    t ~ '(n, s),
    KnownNat n,
    KnownSymbol s,
    SchemaVal ('ContentTable ts :: Content Nat Symbol Bool) ~ Content Integer String Bool
  ) =>
  IsSchema ('ContentTable (t ': ts))
  where
  type SchemaVal ('ContentTable (t ': ts)) = Content Integer String Bool
  schema = case schema @('ContentTable ts :: Content Nat Symbol Bool) of
    ContentTable lst ->
      let n = natVal (Proxy @n)
          s = symbolVal (Proxy @s)
      in ContentTable ((n, s) : lst)
    _ -> error "internal error"
				 
Tom

From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Tue Oct 10 17:40:14 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Tue, 10 Oct 2023 18:40:14 +0100
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <ZSU2zCPDYmeJBV6n@cloudinit-builder>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
 <ZSU2zCPDYmeJBV6n@cloudinit-builder>
Message-ID: <ZSWMfjaTV1Kr410V@cloudinit-builder>

On Tue, Oct 10, 2023 at 12:34:36PM +0100, Tom Ellis wrote:
> On Tue, Oct 10, 2023 at 10:45:00AM +0000, Zoran Bošnjak wrote:
> > I want to convert a type level structure to the value level structure of the same shape.
> > This is the simplified example:
> [...]
> > If I remove the type parameter 'b', 'ContentBool b' and coresponding 'Bool' from the sample, the conversion works as expected.
> 
> The problem is that you have constraints
> 
>     IsSchema ('ContentTable ts)  and  SchemaVal ('ContentTable ts)
> 
> but `ContentTable ts` is of kind `Content n s b` , for some `n` , `s`
> and `b`.  The instance is claiming that it works for all `b` , but it
> doesn't!  Your instance only works when the `ContentTable ts` is of
> kind `Content Nat Symbol Bool`.  The `b` is invisible in the type
> siganture so it's hard to see that it is the problem!
[...]
> Fixing `b` solves the problem, for example:

In fact, my favourite way of dealing with it would be as follows (I
don't know why we seemingly have to indirect through SchemaVal')

-- This data structure serves both for 'type level' and 'value level'.
data Content n s b
  = ContentRaw
  | ContentTable [(n, s)]
  | ContentBool b

deriving instance (Show n, Show s, Show b) => Show (Content n s b)

-- Convert from types to values.
type IsSchema :: forall n s' b. Content n s' b -> Constraint
class IsSchema s where
  type SchemaVal s :: Type
  schema :: SchemaVal s

type SchemaVal' :: forall n s b. Content n s b -> Type
type SchemaVal' s = SchemaVal s

instance IsSchema 'ContentRaw where
  type SchemaVal 'ContentRaw = Content Integer String Bool
  schema = ContentRaw

instance IsSchema ('ContentTable '[]) where
  type SchemaVal ('ContentTable '[]) = Content Integer String Bool
  schema = ContentTable []

instance
  ( IsSchema @Nat @Symbol @Bool ('ContentTable ts),
    t ~ '(n, s),
    KnownNat n,
    KnownSymbol s,
    SchemaVal' @Nat @Symbol @Bool ('ContentTable ts) ~ Content Integer
  String Bool
  ) =>
  IsSchema ('ContentTable (t ': ts))
  where
  type SchemaVal ('ContentTable (t ': ts)) = Content Integer String
  Bool
  schema = case schema @Nat @Symbol @Bool @('ContentTable ts) of
    ContentTable lst ->
      let n = natVal (Proxy @n)
          s = symbolVal (Proxy @s)
       in ContentTable ((n, s) : lst)
    _ -> error "internal error"

From zubin at well-typed.com  Tue Oct 10 18:02:39 2023
From: zubin at well-typed.com (Zubin Duggal)
Date: Tue, 10 Oct 2023 23:32:39 +0530
Subject: [Haskell-cafe] [Haskell] [ANNOUNCE] Haskell Language Server 2.4.0.0
	released
Message-ID: <zkmtoxq7ohseroxigv5wxkypv4mwjd4ynynk36dxyi6felm6l4@j2am2oghnr4g>

Binaries for this release are available at
https://downloads.haskell.org/~hls/haskell-language-server-2.4.0.0/.

These binaries can be installed using
[GHCup](https://www.haskell.org/ghcup/) or the Haskell VSCode extension.

All of these tarballs have associated GPG signatures. The signature
should be from `Zubin Duggal <zubin at well-typed.com>` (key ID
[588764FBE22D19C4](https://keys.openpgp.org/search?q=588764FBE22D19C4)).

The prebuilt binaries in this release support the following GHC
versions:

- 9.0.2
- 9.2.8
- 9.4.7
- 9.6.3
- 9.8.1

# Changelog

* Initial support for GHC 9.8.1, without plugins dependent on
   `ghc-exactprint`
* Fix broken Windows binaries (#3822)

Happy editing!
- Zubin
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From zoran.bosnjak at via.si  Wed Oct 11 08:32:42 2023
From: zoran.bosnjak at via.si (Zoran =?utf-8?Q?Bo=C5=A1njak?=)
Date: Wed, 11 Oct 2023 08:32:42 +0000 (UTC)
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
Message-ID: <2034719846.6554.1697013162021.JavaMail.zimbra@via.si>

Hi Tom,
thanks a lot for your answers. It works as expected. I am building on this proposal, but I am again stuck on the following problems:

- The second proposal introduces 'Content' to the 'IsSchema' type signature. Is it necessary? The problem is when I try to extend it to other types, like 'Variation' and 'Item' (see below).

- I was able to implement instances (using the first proposed solution), but I am getting error on the call site (that is: on the 'main' function. The error says: ‘SchemaVal’ is a non-injective type family. I don't know how to get around it. I would appreciate if you have another look.

Here is an updated example:

{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

module Test where

import Data.Kind
import Data.Proxy
import GHC.TypeLits

data Content n s b
  = ContentRaw
  | ContentTable [(n, s)]
  | ContentBool b

deriving instance (Show n, Show s, Show b) => Show (Content n s b)

data Variation n s b
  = Element n (Content n s b)
  | Group [Item n s b]

deriving instance (Show n, Show s, Show b) => Show (Variation n s b)

data Item n s b
  = Spare n
  | Item s (Variation n s b)

deriving instance (Show n, Show s, Show b) => Show (Item n s b)

-- Convert from types to values.
class IsSchema t where
  type SchemaVal t :: Type
  schema :: SchemaVal t

-- Instances implementation...
-- to be defined...

-- Test
type V1 = 'Element 1 'ContentRaw
type I1 = 'Item "title1" V1
type I2 = 'Item "title2" V1

type G0 = 'Group '[]
type G1 = 'Group (I1 ': '[])
type G2 = 'Group (I1 ': I2 ': '[])

main :: IO ()
main = do
  print $ schema @V1
  print $ schema @I1
  print $ schema @I2
  print $ schema @G0
  print $ schema @G1
  print $ schema @G2
  print (schema @G1 /= schema @G2)

From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Wed Oct 11 09:09:41 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Wed, 11 Oct 2023 10:09:41 +0100
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <2034719846.6554.1697013162021.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
 <2034719846.6554.1697013162021.JavaMail.zimbra@via.si>
Message-ID: <ZSZmVaUpgJDJhev7@cloudinit-builder>

On Wed, Oct 11, 2023 at 08:32:42AM +0000, Zoran Bošnjak wrote:
> I was able to implement instances (using the first proposed
> solution), but I am getting error on the call site (that is: on the
> 'main' function. The error says: ‘SchemaVal’ is a non-injective type
> family. I don't know how to get around it. I would appreciate if you
> have another look.

Sure, I'm happy to take another look, but ...

> -- Instances implementation...
> -- to be defined...

won't I need these instances in order to see how to make it work?

From stefan.wehr at gmail.com  Wed Oct 11 09:27:03 2023
From: stefan.wehr at gmail.com (Stefan Wehr)
Date: Wed, 11 Oct 2023 11:27:03 +0200
Subject: [Haskell-cafe] Call for Contributions: BOB 2024 [March 15,
	Deadline Nov 17]
Message-ID: <CAJAdMdG24rmes1d3xkudB522SGpyCxpkt7NH3dYocthoam=i0g@mail.gmail.com>

================================================================================
                         BOB Conference 2024
         "What happens when we use what's best for a change?"
                  https://bobkonf.de/2024/cfc.html
                         Berlin, Mar 17
                        Call for Contributions
                     Deadline: November 17, 2023
================================================================================

You are actively engaged in advanced software engineering methods,
solve ambitious problem with software and are open to cutting-edge
innovation? Attend this conference, meet people that share your goals,
and get to know the best software tools and technologies available
today. We strive to offer a day full of new experiences and
impressions that you can use to immediately improve your daily life as
a software developer.

If you share our vision and want to contribute, submit a proposal for
a talk or tutorial!

NOTE: The conference fee will be waived for presenters. Travel
expenses will not be covered (for exceptions see "Speaker Grants").

Shepherding
-----------

The program committee offers shepherding to all speakers. Shepherding
provides speakers assistance with preparing their
sessions. Specifically:

- advice on structure and presentation
- review of talk slides
- assistance with recording
- review of recording, if applicable

Speaker Grants
--------------

BOB has Speaker Grants available to support speakers from groups
under-represented in technology. We specifically seek women speakers,
speakers of color, and speakers who are not able to attend the
conference for financial reasons.

Topics
------

We are looking for talks about best-of-breed software technology, e.g.:

- functional programming
- persistent data structures and databases
- event-based modelling and architecture
- "fancy types" (dependent types, gradual typing, linear types, ...)
- formal methods for correctness and robustness
- abstractions for concurrency and parallelism
- metaprogramming
- probabilistic programming
- math and programming
- controlled side effects
- program synthesis
- next-generation IDEs
- effective abstractions for data analytics
- … everything really that isn’t mainstream, but you think should be
- … includeing rough ideas worth discussing.

Presenters should provide the audience with information that is
practically useful for software developers.

Challenges
----------

Furthermore, we seek contributions on successful approaches for
solving hard problems, for example:

- bias in machine-learning systems
- digital transformation in difficult settings
- accessibiltity
- systems with critical reliability requirements
- ecologically sustainable software development

We're especially interested in experience reports.
Other topics are also relevant, e.g.:

- introductory talks on technical background
- overviews of a given field
- demos and how-tos

Requirements
------------

We accept proposals for presentations of 45 minutes (40 minutes talk +
5 minutes questions), as well as 90 minute tutorials for
beginners. The language of presentation should be either English or
German.

Your proposal should include (in your presentation language of choice):

- An abstract of max. 1500 characters.
- A short bio/cv
- Contact information (including at least email address)
- A list of 3-5 concrete ideas of how your work can be applied in a
developer's daily life
- additional material (websites, blogs, slides, videos of past presentations, …)

Organisation
------------

- Direct questions to konferenz at bobkonf dot de
- Proposal deadline: November 17, 2023
- Notification: December 5, 2023
- Program: December 12, 2023

Submit here:
https://pretalx.com/bob-2024/submit/

Program Committee
-----------------

(more information here: https://bobkonf.de/2024/programmkomitee.html)

- Matthias Fischmann, Wire
- Matthias Neubauer, SICK AG
- Nicole Rauch, Softwareentwicklung und Entwicklungscoaching
- Michael Sperber, Active Group
- Stefan Wehr, Hochschule Offenburg

Scientific Advisory Board

- Annette Bieniusa, TU Kaiserslautern
- Torsten Grust, Uni Tübingen
- Peter Thiemann, Uni Freiburg
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From zoran.bosnjak at via.si  Wed Oct 11 10:23:31 2023
From: zoran.bosnjak at via.si (Zoran =?utf-8?Q?Bo=C5=A1njak?=)
Date: Wed, 11 Oct 2023 10:23:31 +0000 (UTC)
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
Message-ID: <1428787314.6577.1697019811709.JavaMail.zimbra@via.si>

I am including the instances. The error is:

    • Couldn't match expected type: SchemaVal G1
                  with actual type: SchemaVal G2
      NB: ‘SchemaVal’ is a non-injective type family
      The type variables ‘b3’, ‘b2’ are ambiguous
    • In the second argument of ‘(/=)’, namely ‘schema @G2’
      In the first argument of ‘print’, namely
        ‘(schema @G1 /= schema @G2)’
      In a stmt of a 'do' block: print (schema @G1 /= schema @G2)

{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE UndecidableInstances #-}

module Test where

import Data.Kind
import Data.Proxy
import GHC.TypeLits

data Content n s b
  = ContentRaw
  | ContentTable [(n, s)]
  | ContentBool b

deriving instance (Show n, Show s, Show b) => Show (Content n s b)

data Variation n s b
  = Element n (Content n s b)
  | Group [Item n s b]

deriving instance (Show n, Show s, Show b) => Show (Variation n s b)

data Item n s b
  = Spare n
  | Item s (Variation n s b)

deriving instance (Show n, Show s, Show b) => Show (Item n s b)

-- Convert from types to values.
class IsSchema t where
  type SchemaVal t :: Type
  schema :: SchemaVal t

instance IsSchema 'ContentRaw where
  type SchemaVal ContentRaw = Content Integer String Bool
  schema = ContentRaw

instance IsSchema ('ContentTable '[]) where
  type SchemaVal (ContentTable '[]) = Content Integer String Bool
  schema = ContentTable []

instance
  ( IsSchema ('ContentTable ts :: Content Nat Symbol Bool)
  , t ~ '(n, s)
  , KnownNat n
  , KnownSymbol s
  , SchemaVal ('ContentTable ts :: Content Nat Symbol Bool) ~ Content Integer String Bool
  )
  => IsSchema ('ContentTable (t ': ts))
  where
  type SchemaVal ('ContentTable (t ': ts)) = Content Integer String Bool
  schema = case schema @('ContentTable ts :: Content Nat Symbol Bool) of
    ContentTable lst ->
      let n = natVal (Proxy @n)
          s = symbolVal (Proxy @s)
       in ContentTable ((n, s) : lst)
    _ -> error "internal error"

instance IsSchema 'True where
  type SchemaVal 'True = Bool
  schema = True

instance IsSchema 'False where
  type SchemaVal 'False = Bool
  schema = False

instance
  ( IsSchema b
  , SchemaVal b ~ Bool
  )
  => IsSchema ('ContentBool b)
  where
  type SchemaVal ('ContentBool b) = Content Integer String Bool
  schema = ContentBool (schema @b)

instance
  ( KnownNat n
  , SchemaVal c ~ Content Integer String Bool
  , IsSchema c
  )
  => IsSchema ('Element n c)
  where
  type SchemaVal ('Element n c) = Variation Integer String Bool
  schema = Element (natVal (Proxy @n)) (schema @c)

instance IsSchema ('Group '[]) where
  type SchemaVal ('Group '[]) = Variation Integer String Bool
  schema = Group []

instance
  ( IsSchema t
  , IsSchema ('Group ts)
  , SchemaVal t ~ Item Integer String Bool
  , SchemaVal ('Group ts :: Variation Nat Symbol Bool) ~ Variation Integer String Bool
  )
  => IsSchema ('Group (t ': ts))
  where
  type SchemaVal ('Group (t ': ts)) = Variation Integer String Bool
  schema = case schema @('Group ts) of
    Group lst -> Group (schema @t : lst)
    _ -> error "internal error"

instance (KnownNat n) => IsSchema ('Spare n) where
  type SchemaVal ('Spare n) = Item Integer String Bool
  schema = Spare (natVal $ Proxy @n)

instance
  ( KnownSymbol s
  , IsSchema v
  , SchemaVal v ~ Variation Integer String Bool
  )
  => IsSchema ('Item s v)
  where
  type SchemaVal ('Item s v) = Item Integer String Bool
  schema = Item (symbolVal $ Proxy @s) (schema @v)

-- Test
type C = 'ContentRaw
type V1 = 'Element 1 C
type I1 = 'Item "title1" V1
type I2 = 'Item "title2" V1

type G0 = 'Group '[]
type G1 = 'Group (I1 ': '[])
type G2 = 'Group (I1 ': I2 ': '[])

main :: IO ()
main = do
  print $ schema @C
  print $ schema @('ContentBool 'True)
  print $ schema @V1
  print $ schema @I1
  print $ schema @I2
  print $ schema @G0
  print $ schema @G1
  print $ schema @G2
  print (schema @G1 /= schema @G2)

From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Wed Oct 11 13:07:54 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Wed, 11 Oct 2023 14:07:54 +0100
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <1428787314.6577.1697019811709.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
 <1428787314.6577.1697019811709.JavaMail.zimbra@via.si>
Message-ID: <ZSaeKkN0iocTqwrF@cloudinit-builder>

On Wed, Oct 11, 2023 at 10:23:31AM +0000, Zoran Bošnjak wrote:
> I am including the instances. The error is:
> 
>     • Couldn't match expected type: SchemaVal G1
>                   with actual type: SchemaVal G2
>       NB: ‘SchemaVal’ is a non-injective type family
>       The type variables ‘b3’, ‘b2’ are ambiguous
>     • In the second argument of ‘(/=)’, namely ‘schema @G2’

Try:

    type C = 'ContentRaw :: Content Nat Symbol Bool

If that doesn't work I'll have a look later.

Tom







From zoran.bosnjak at via.si  Wed Oct 11 13:24:06 2023
From: zoran.bosnjak at via.si (Zoran =?utf-8?Q?Bo=C5=A1njak?=)
Date: Wed, 11 Oct 2023 13:24:06 +0000 (UTC)
Subject: [Haskell-cafe] ambiguous type variable question
In-Reply-To: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
References: <443791954.6309.1696934700989.JavaMail.zimbra@via.si>
Message-ID: <551331534.6601.1697030646912.JavaMail.zimbra@via.si>


> type C = 'ContentRaw :: Content Nat Symbol Bool

This works. Thanks for your help.

From kazu at iij.ad.jp  Thu Oct 12 03:07:58 2023
From: kazu at iij.ad.jp (Kazu Yamamoto (=?iso-2022-jp?B?GyRCOzNLXE9CSScbKEI=?=))
Date: Thu, 12 Oct 2023 12:07:58 +0900 (JST)
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <87ttqzignm.fsf@smart-cactus.org>
References: <87ttqzignm.fsf@smart-cactus.org>
Message-ID: <20231012.120758.761285182974050466.kazu@iij.ad.jp>

Hi,
# The destination is only to haskell-cafe.

Thank you for releasing GHC 9.8.1.

I realized that "unzip" conflicts if Data.List and Data.Functor are
imported.

If this is intentional, please tell me which "unzip" we should use.

--Kazu

> The GHC developers are very pleased to announce the availability of 
> the
> final release of GHC 9.8.1. Binary distributions, source
> distributions, and documentation are available at 
> downloads.haskell.org:
>
>     https://downloads.haskell.org/ghc/9.8.1
>
> GHC 9.8 brings a number of new features and improvements, including:
>
>  * Preliminary support the `TypeAbstractions` language extension,
>    allowing types to be bound in type declarations 
> [TypeAbstractions].
>
>  * Support for the `ExtendedLiterals` extension, providing syntax 
> for
>    non-word-sized numeric literals in the surface language
>    [extended-literals]
>
>  * Improved rewrite rule matching behavior, allowing limited 
> matching of
>    higher-order patterns
>
>  * Better support for user-defined warnings by way of the `WARNING`
>    pragma [warnings]
>
>  * The introduction of the new `GHC.TypeError.Unsatisfiable`
>    constraint, allowing more predictable user-defined type errors
>    [unsatisfiable]
>
>  * Implementation of the export deprecation proposal, allowing 
> module
>    exports to be marked with `DEPRECATE` pragmas 
> [deprecated-exports]
>
>  * The addition of build semaphore support for parallel compilation;
>    with coming support in `cabal-install` this will allow better 
> use of
>    parallelism in multi-package builds [jsem]
>
>  * More efficient representation of info table provenance 
> information,
>    reducing binary sizes by over 50% in some cases when
>    `-finfo-table-map` is in use
>
> A full accounting of changes can be found in the [release notes][].
> Plans for GHC's future releases can be found on the [GHC 
> Wiki][status].
>
> We would like to thank GitHub, IOG, the Zw3rk stake pool,
> Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell
> Foundation, and other anonymous contributors whose on-going 
> financial
> and in-kind support has facilitated GHC maintenance and release
> management over the years. Finally, this release would not have been
> possible without the hundreds of open-source contributors whose work
> comprise this release.
>
> Happy compiling,
>
> ~ Ben
>
>
> [TypeAbstractions]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-decl-invis-binders.rst
> [extended-literals]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst
> [unsatisfiable]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-unsatisfiable.rst
> [warnings]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst
> [deprecated-exports]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-deprecating-exports-proposal.rst
> [jsem]: 
> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-jsem.rst
> [release notes]: 
> https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html
> [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status



From haskellcafe at dandart.co.uk  Thu Oct 12 10:27:19 2023
From: haskellcafe at dandart.co.uk (Dan Dart)
Date: Thu, 12 Oct 2023 11:27:19 +0100
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <20231012.120758.761285182974050466.kazu@iij.ad.jp>
References: <87ttqzignm.fsf@smart-cactus.org>
 <20231012.120758.761285182974050466.kazu@iij.ad.jp>
Message-ID: <CADNJRYELRjDZ6corK+ObaLJyS8W6aXVTC=DoWJ3rLWRmOf7hwQ@mail.gmail.com>

 I saw that Data.List was starting to be recommended to be imported
qualified anyway... hence I always do:

import Data.List qualified as L

these days.

From lemming at henning-thielemann.de  Thu Oct 12 10:34:59 2023
From: lemming at henning-thielemann.de (Henning Thielemann)
Date: Thu, 12 Oct 2023 12:34:59 +0200 (CEST)
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <CADNJRYELRjDZ6corK+ObaLJyS8W6aXVTC=DoWJ3rLWRmOf7hwQ@mail.gmail.com>
References: <87ttqzignm.fsf@smart-cactus.org>
 <20231012.120758.761285182974050466.kazu@iij.ad.jp>
 <CADNJRYELRjDZ6corK+ObaLJyS8W6aXVTC=DoWJ3rLWRmOf7hwQ@mail.gmail.com>
Message-ID: <65010e9-6e9c-c54-7f50-d8ef8a5fc37@henning-thielemann.de>


On Thu, 12 Oct 2023, Dan Dart wrote:

> I saw that Data.List was starting to be recommended to be imported
> qualified anyway... hence I always do:
>
> import Data.List qualified as L
>
> these days.

Why not
   import qualified Data.List as List
  ?

List.zip is pretty self-explanatory.

From haskellcafe at dandart.co.uk  Thu Oct 12 11:51:05 2023
From: haskellcafe at dandart.co.uk (Dan Dart)
Date: Thu, 12 Oct 2023 12:51:05 +0100
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <65010e9-6e9c-c54-7f50-d8ef8a5fc37@henning-thielemann.de>
References: <87ttqzignm.fsf@smart-cactus.org>
 <20231012.120758.761285182974050466.kazu@iij.ad.jp>
 <CADNJRYELRjDZ6corK+ObaLJyS8W6aXVTC=DoWJ3rLWRmOf7hwQ@mail.gmail.com>
 <65010e9-6e9c-c54-7f50-d8ef8a5fc37@henning-thielemann.de>
Message-ID: <CADNJRYGVTcb5Zqq0ar9nU_gw1jKcCn=pNSrNtjNp2t+jbc6SBg@mail.gmail.com>

> Why not
>    import qualified Data.List as List
>   ?

Yeah, that's way better. I don't know what's with me and having single
letter import qualifications. Guess I'm just used to it.

From jaro.reinders at gmail.com  Thu Oct 12 11:57:50 2023
From: jaro.reinders at gmail.com (J. Reinders)
Date: Thu, 12 Oct 2023 13:57:50 +0200
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <20231012.120758.761285182974050466.kazu@iij.ad.jp>
References: <87ttqzignm.fsf@smart-cactus.org>
 <20231012.120758.761285182974050466.kazu@iij.ad.jp>
Message-ID: <7FF6FD1B-4944-41CD-8BC4-E43C01FB6B7B@gmail.com>

Hi Kazu,

In addition to the other answers, I’d like to note that Data.List.unzip can be
much more efficient than Data.Functor.unzip. In particular, Data.List.unzip
only does a single traversal over the list and it can be fused with good
producers. Whereas Data.Functor.unzip does two traversals and cannot fuse.
The documentation should really be changed to mention that.

So, I’d say use Data.List.unzip when possible.

Cheers,

Jaro

> On 12 Oct 2023, at 05:07, Kazu Yamamoto (山本和彦) via Haskell-Cafe <haskell-cafe at haskell.org> wrote:
> 
> Hi,
> # The destination is only to haskell-cafe.
> 
> Thank you for releasing GHC 9.8.1.
> 
> I realized that "unzip" conflicts if Data.List and Data.Functor are
> imported.
> 
> If this is intentional, please tell me which "unzip" we should use.
> 
> --Kazu
> 
>> The GHC developers are very pleased to announce the availability of the
>> final release of GHC 9.8.1. Binary distributions, source
>> distributions, and documentation are available at downloads.haskell.org:
>> 
>>    https://downloads.haskell.org/ghc/9.8.1
>> 
>> GHC 9.8 brings a number of new features and improvements, including:
>> 
>> * Preliminary support the `TypeAbstractions` language extension,
>>   allowing types to be bound in type declarations [TypeAbstractions].
>> 
>> * Support for the `ExtendedLiterals` extension, providing syntax for
>>   non-word-sized numeric literals in the surface language
>>   [extended-literals]
>> 
>> * Improved rewrite rule matching behavior, allowing limited matching of
>>   higher-order patterns
>> 
>> * Better support for user-defined warnings by way of the `WARNING`
>>   pragma [warnings]
>> 
>> * The introduction of the new `GHC.TypeError.Unsatisfiable`
>>   constraint, allowing more predictable user-defined type errors
>>   [unsatisfiable]
>> 
>> * Implementation of the export deprecation proposal, allowing module
>>   exports to be marked with `DEPRECATE` pragmas [deprecated-exports]
>> 
>> * The addition of build semaphore support for parallel compilation;
>>   with coming support in `cabal-install` this will allow better use of
>>   parallelism in multi-package builds [jsem]
>> 
>> * More efficient representation of info table provenance information,
>>   reducing binary sizes by over 50% in some cases when
>>   `-finfo-table-map` is in use
>> 
>> A full accounting of changes can be found in the [release notes][].
>> Plans for GHC's future releases can be found on the [GHC Wiki][status].
>> 
>> We would like to thank GitHub, IOG, the Zw3rk stake pool,
>> Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell
>> Foundation, and other anonymous contributors whose on-going financial
>> and in-kind support has facilitated GHC maintenance and release
>> management over the years. Finally, this release would not have been
>> possible without the hundreds of open-source contributors whose work
>> comprise this release.
>> 
>> Happy compiling,
>> 
>> ~ Ben
>> 
>> 
>> [TypeAbstractions]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-decl-invis-binders.rst
>> [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst
>> [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-unsatisfiable.rst
>> [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst
>> [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-deprecating-exports-proposal.rst
>> [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-jsem.rst
>> [release notes]: https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html
>> [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status
> 
> 
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.



From kazu at iij.ad.jp  Fri Oct 13 02:42:07 2023
From: kazu at iij.ad.jp (Kazu Yamamoto (=?iso-2022-jp?B?GyRCOzNLXE9CSScbKEI=?=))
Date: Fri, 13 Oct 2023 11:42:07 +0900 (JST)
Subject: [Haskell-cafe] [ANNOUNCE] GHC 9.8.1 is now available
In-Reply-To: <7FF6FD1B-4944-41CD-8BC4-E43C01FB6B7B@gmail.com>
References: <87ttqzignm.fsf@smart-cactus.org>
 <20231012.120758.761285182974050466.kazu@iij.ad.jp>
 <7FF6FD1B-4944-41CD-8BC4-E43C01FB6B7B@gmail.com>
Message-ID: <20231013.114207.1607352107743863334.kazu@iij.ad.jp>

Hi Jaro,

Thanks.

I also noticed that Prelude exports "unzip" which is identical to
Data.List. So, I should use it.

--Kazu

> Hi Kazu,
>
> In addition to the other answers, I’d like to note that 
> Data.List.unzip can be
> much more efficient than Data.Functor.unzip. In particular, 
> Data.List.unzip
> only does a single traversal over the list and it can be fused with 
> good
> producers. Whereas Data.Functor.unzip does two traversals and 
> cannot fuse.
> The documentation should really be changed to mention that.
>
> So, I’d say use Data.List.unzip when possible.
>
> Cheers,
>
> Jaro
>
>> On 12 Oct 2023, at 05:07, Kazu Yamamoto (山本和彦) via 
>> Haskell-Cafe <haskell-cafe at haskell.org> wrote:
>>
>> Hi,
>> # The destination is only to haskell-cafe.
>>
>> Thank you for releasing GHC 9.8.1.
>>
>> I realized that "unzip" conflicts if Data.List and Data.Functor are
>> imported.
>>
>> If this is intentional, please tell me which "unzip" we should use.
>>
>> --Kazu
>>
>>> The GHC developers are very pleased to announce the availability 
>>> of the
>>> final release of GHC 9.8.1. Binary distributions, source
>>> distributions, and documentation are available at 
>>> downloads.haskell.org:
>>>
>>>    https://downloads.haskell.org/ghc/9.8.1
>>>
>>> GHC 9.8 brings a number of new features and improvements, 
>>> including:
>>>
>>> * Preliminary support the `TypeAbstractions` language extension,
>>>   allowing types to be bound in type declarations 
>>> [TypeAbstractions].
>>>
>>> * Support for the `ExtendedLiterals` extension, providing syntax 
>>> for
>>>   non-word-sized numeric literals in the surface language
>>>   [extended-literals]
>>>
>>> * Improved rewrite rule matching behavior, allowing limited 
>>> matching of
>>>   higher-order patterns
>>>
>>> * Better support for user-defined warnings by way of the `WARNING`
>>>   pragma [warnings]
>>>
>>> * The introduction of the new `GHC.TypeError.Unsatisfiable`
>>>   constraint, allowing more predictable user-defined type errors
>>>   [unsatisfiable]
>>>
>>> * Implementation of the export deprecation proposal, allowing 
>>> module
>>>   exports to be marked with `DEPRECATE` pragmas 
>>> [deprecated-exports]
>>>
>>> * The addition of build semaphore support for parallel 
>>> compilation;
>>>   with coming support in `cabal-install` this will allow better 
>>> use of
>>>   parallelism in multi-package builds [jsem]
>>>
>>> * More efficient representation of info table provenance 
>>> information,
>>>   reducing binary sizes by over 50% in some cases when
>>>   `-finfo-table-map` is in use
>>>
>>> A full accounting of changes can be found in the [release 
>>> notes][].
>>> Plans for GHC's future releases can be found on the [GHC 
>>> Wiki][status].
>>>
>>> We would like to thank GitHub, IOG, the Zw3rk stake pool,
>>> Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, the Haskell
>>> Foundation, and other anonymous contributors whose on-going 
>>> financial
>>> and in-kind support has facilitated GHC maintenance and release
>>> management over the years. Finally, this release would not have 
>>> been
>>> possible without the hundreds of open-source contributors whose 
>>> work
>>> comprise this release.
>>>
>>> Happy compiling,
>>>
>>> ~ Ben
>>>
>>>
>>> [TypeAbstractions]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-decl-invis-binders.rst
>>> [extended-literals]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-sized-literals.rst
>>> [unsatisfiable]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-unsatisfiable.rst
>>> [warnings]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-warning-pragmas-with-categories.rst
>>> [deprecated-exports]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-deprecating-exports-proposal.rst
>>> [jsem]: 
>>> https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-jsem.rst
>>> [release notes]: 
>>> https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html
>>> [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status
>>
>>
>> _______________________________________________
>> Haskell-Cafe mailing list
>> To (un)subscribe, modify options or view archives go to:
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>> Only members subscribed via the mailman list are allowed to post.
>
>



From lists at richarde.dev  Fri Oct 13 10:01:34 2023
From: lists at richarde.dev (Richard Eisenberg)
Date: Fri, 13 Oct 2023 10:01:34 +0000
Subject: [Haskell-cafe] CFP: Workshop on the Implementation of Type Systems
	(WITS) '24
Message-ID: <010f018b287bf553-bd521008-480f-4b4b-9bba-8d1ef23231ff-000000@us-east-2.amazonses.com>


----------------------------------------------------------------------

                        CALL FOR CONTRIBUTIONS

          3rd Workshop on the Implementation of Type Systems

                             WITS 2024

                          January 20, 2024
                       London, United Kingdom

              https://popl24.sigplan.org/home/wits-2024 <https://popl24.sigplan.org/home/wits-2024>

----------------------------------------------------------------------

WITS 2024 is the third Workshop on the Implementation of Type Systems. The
workshop will be held on January 20, 2024, in London, United Kingdom, co-located
with POPL. The goal of this workshop is to bring together the implementors of a
variety of languages with advanced type systems. The main focus is on the
practical issues that come up in the implementation of these systems, rather
than the theoretical frameworks that underlie them. In particular, we want to
encourage exchanging ideas between the communities around specific systems that
would otherwise be accessible to only a very select group.

The workshop will have a mix of invited and contributed talks, organized
discussion times, and informal collaboration time.

*Scope*

We invite participants to share their experiences, study differences among the
implementations, and generalize lessons from those. We also want to promote the
creation of a shared vocabulary and set of best practices for implementing type
systems.

Here are a few examples of topics we are interested to discuss:

 * syntax with binders and substitution
 * conversion modulo beta and eta
 * implicit arguments and metavariables
 * unification and constraint solving
 * metaprogramming and tactic languages
 * editor integration and automation
 * discoverability of language features
 * pretty printing and error messages

This list is not exhaustive, so please contact the PC chairs in case you are
unsure if a topic falls within the scope of the workshop.

*Submissions*

WITS solicits two kinds of submissions:

* Contributed talks on the basis of an abstract. This can be on recently
  published or submitted work, work in progress, or a project that is still in
  the idea phase.

* Proposals for roundtable discussions. This can be on any topic within the
  scope of the workshop, but should have a broader scope than a contributed
  talk. If accepted, you will be in charge of leading a discussion of 45 minutes
  around the proposed topic together with other interested attendees.

Both kinds of proposals should be accompanied by an abstract of max. 1 page
(exclusive of references), formatted according to the guidelines for SIGPLAN
conferences: use the `sigplan` option to the `acmart` LaTeX document class. WITS
will have no published proceedings, so submitting to WITS does not interfere
with submission (before, after, or simultaneously) with other
venues. Submissions are handled via https://wits24.hotcrp.com/ <https://wits24.hotcrp.com/>.

*Important Dates*

- Abstract submission deadline: 10 November, 2023 (AoE)
- Notification: 1 December, 2023
- Workshop in London: 20 January, 2024

*Attendance and registration*

WITS 2024 is colocated with POPL 2024 in London, UK. Information
on registration and attendance will be posted on the POPL website
at https://popl24.sigplan.org/ <https://popl24.sigplan.org/>.

*Program Committee*

Lennart Augustsson      Epic Games, Sweden
Edwin Brady             St. Andrews, UK
Jesper Cockx            TU Delft, Netherlands   co-chair
Richard Eisenberg       Jane Street, USA        co-chair
Jacques-Henri Jourdan   CRNS, France
Matthieu Sozeau         INRIA, France
Ningning Xie            U. of Toronto, Canada

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From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Fri Oct 13 13:06:29 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Fri, 13 Oct 2023 14:06:29 +0100
Subject: [Haskell-cafe] Release: stan, supporting GHCs 8.8-9.4
Message-ID: <ZSlA1Svayk9j8ZfG@cloudinit-builder>

I'm pleased to announce a new release of `stan`, a static analysis
tool for Haskell. `stan` now supports GHCs in the range 8.8-9.4[1].

### About `stan`

Stan is a command-line tool for analysing Haskell projects. It
discovers which parts of the code can potentially be improved, and
offers suggestions on how to do so. Read more about  `stan` in its
[`README`](https://github.com/kowainik/stan/#what-this-tool-is-about).

### Installation

I recommend obtaining `stan` from Hackage by following [the
installation instructions in the
README](https://github.com/kowainik/stan/#hackage).

https://hackage.haskell.org/package/stan-0.1.0.0

### Help wanted

`stan` lacks active maintainers and is currently in essential
maintainance only mode. I am helping out to make sure `stan` can
continue to build with newer GHCs. I would welcome assistance,
particularly on the following issues:

* Supporting GHC 9.6
* Supporting GHC 9.8
* Prospective support for GHC 9.10
* Fixing caching on Github Actions

If you would like to contribute to Stan please [create an
issue](https://github.com/kowainik/stan/issues) on the Github
repository.

### Credits

Thanks to the Kowainik team for creating `stan` in the first
place. Thanks to Veronika Romashkina for accepting me as a new
maintainer for the project.

----

[1] Some point releases are excluded because the GHC API doesn't seem
to provide enough type information, notably the later releases in the
9.2 series.

From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Sun Oct 15 19:32:13 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Sun, 15 Oct 2023 20:32:13 +0100
Subject: [Haskell-cafe] Release: stan, extending support to GHC 9.6
In-Reply-To: <ZSlA1Svayk9j8ZfG@cloudinit-builder>
References: <ZSlA1Svayk9j8ZfG@cloudinit-builder>
Message-ID: <ZSw+PSJXcLrNw2Ha@cloudinit-builder>

I'm pleased to announce an even newer release of `stan`, a static
analysis tool for Haskell. This release extends last week's release by
adding support for 9.6, extending the supported range to 8.8-9.6.

### About `stan`

Stan is a command-line tool for analysing Haskell projects. It
discovers which parts of the code can potentially be improved, and
offers suggestions on how to do so. Read more about  `stan` in its
[`README`](https://github.com/kowainik/stan/#what-this-tool-is-about).

### Installation

I recommend obtaining `stan` from Hackage by following [the
installation instructions in the
README](https://github.com/kowainik/stan/#hackage).

https://hackage.haskell.org/package/stan-0.1.0.0

### Help wanted

`stan` lacks active maintainers and is currently in essential
maintainance only mode. I am helping out to make sure `stan` can
continue to build with newer GHCs. I would welcome assistance,
particularly on the following issues:

* Supporting GHC 9.8
* Prospective support for GHC 9.10
* Fixing caching on Github Actions

If you would like to contribute to Stan please [create an
issue](https://github.com/kowainik/stan/issues) on the Github
repository.

----

[1] Some point releases are excluded because the GHC API doesn't seem
to provide enough type information, notably the later releases in the
9.2 series.

From robstewart57 at gmail.com  Tue Oct 17 14:50:50 2023
From: robstewart57 at gmail.com (Rob Stewart)
Date: Tue, 17 Oct 2023 15:50:50 +0100
Subject: [Haskell-cafe] CFP: Workshop on Hardware Acceleration of Functional
	and Declarative Languages
Message-ID: <CA+ZOasKm0n276bctyv9R5L5SUBg0hmvWrzzCcDkkqr1g6uiSsg@mail.gmail.com>

Hi haskell-cafe,

Call for participation: HAFDAL 2024

The 1st Workshop on Hardware Acceleration of Functional and Declarative
Languages (HAFDAL) will be co-located with HPCA, Edinburgh on March 2nd or
3rd 2024. This workshop will bring together computer architects and
programming language implementers to explore software/hardware co-designs
of high level execution models.

We invite two forms of participation: (1) full paper submissions for 30
minute talks, (2) 5-10 minute lightning talks about related projects and
early results. For full papers, we are looking for submissions that cover
the motivation, design, or real-world application of hardware technology
for functional/declarative languages, their compilers and runtime systems.

Submission deadline: 20 November 2023.

The call for participation and all key dates are here:

https://haflang.github.io/images/hafdal24_cfp.pdf

The workshop's website is:

https://haflang.github.io/workshops/hafdal24.html

Best wishes,

Rob Stewart
Associate Professor
Mathematical and Computer Sciences
Heriot-Watt University
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From msantolu at barnard.edu  Tue Oct 17 20:20:00 2023
From: msantolu at barnard.edu (Mark Santolucito)
Date: Tue, 17 Oct 2023 16:20:00 -0400
Subject: [Haskell-cafe] Assistant Prof at Barnard College, Columbia U
Message-ID: <CAFivCSovJf5PHBO7FC3j-U95O=rndgGbS6TNz=j39jL3XcDb_g@mail.gmail.com>

Hi all,

Barnard College, Columbia University has an opening for an Assistant
Professor: https://cs.barnard.edu/assistant-professor-computer-science-2024

The deadline is Oct 27 for full consideration. Barnard is the women's
college of Columbia and has a 2-2 teaching load (typically with additional
reductions). If you are interested, please feel free to reach out to me
directly to discuss more. This is a unique place that I have really enjoyed
the past few years!

Mark
https://www.marksantolucito.com/
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From daniel.casanueva at proton.me  Wed Oct 18 11:04:43 2023
From: daniel.casanueva at proton.me (Daniel Casanueva)
Date: Wed, 18 Oct 2023 11:04:43 +0000
Subject: [Haskell-cafe] Request for take over: graphviz
Message-ID: <D9aV-Tbs8uhnr5FuBSE5loMA1-1CCN8qA9oxOvsTJc68c2P2g6waB5fGbh2YqO75vRwizGjwUTCjxZgmM0_XLWZMinKf7aVdXt-LJ4zNzyk=@proton.me>

Hello,

graphviz [1] maintenance has been inactive for a long time now. Revisions have been published, but the maintainer seems unresponsive. Last year, Bodigrim suggested the package needs a new maintainer in a GitHub thread [2] that one month ago I found while looking if someone had already done the fix I needed.

I'm happy to help keeping the package alive so, about a month ago, I emailed Ivan (graphviz's author) to the e-mail address from his GitHub profile, offering my assistance with graphviz. I haven't gotten any answer yet, so I thought I should be making my offer public, as indicated by the "Taking over a package" wikipage [3].

I don't have big change plans for graphviz. Most likely I will just be patching it to keep it working with future GHC releases and reviewing/accepting PRs.

Thank you,
Daniel

[1] https://hackage.haskell.org/package/graphviz
[2] https://github.com/ivan-m/graphviz/pull/53#issuecomment-1261496914
[3] https://wiki.haskell.org/Taking_over_a_package

From noonsilk at gmail.com  Thu Oct 19 08:23:59 2023
From: noonsilk at gmail.com (Noon van der Silk)
Date: Thu, 19 Oct 2023 09:23:59 +0100
Subject: [Haskell-cafe] Where did pem-0.2.4 come from? a.k.a. is anyone
 compelled to take-over this project?
Message-ID: <CAKBUzA0tzP3xKJH62A1d+zzA3UnN7eT25X0S8rDDs99_TNMwNw@mail.gmail.com>

Glancing at hackage, I happened to noticed that pem is at 0.2.4 -
https://hackage.haskell.org/package/pem-0.2.4

Glancing at the repo, I notice that pem is at 0.2.3 -
https://github.com/vincenthz/hs-pem

It seems there _is_ a tag for 0.2.4, but `master` has not been updated
<https://github.com/vincenthz/hs-pem/compare/master..pem-v0.2.4>.

Is there anyone out there that feels compelled or excited to fix this?

And perhaps relatedly, given vincent has archived all these repos; perhaps
there could be a kind of "global takeover" by the HF cryptography working
group of these projects?

-- 
Noon van der Silk, ن

http://silky.github.io/

"My programming language is kindness."
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From haskellcafe at dandart.co.uk  Thu Oct 19 11:09:12 2023
From: haskellcafe at dandart.co.uk (Dan Dart)
Date: Thu, 19 Oct 2023 12:09:12 +0100
Subject: [Haskell-cafe] Where did pem-0.2.4 come from? a.k.a. is anyone
 compelled to take-over this project?
In-Reply-To: <CAKBUzA0tzP3xKJH62A1d+zzA3UnN7eT25X0S8rDDs99_TNMwNw@mail.gmail.com>
References: <CAKBUzA0tzP3xKJH62A1d+zzA3UnN7eT25X0S8rDDs99_TNMwNw@mail.gmail.com>
Message-ID: <CADNJRYFGP5=Lq=bavEqA4BLLfknFM+mnO+d4RXqupwEUDDCj2Q@mail.gmail.com>

That's an odd one, I noticed that on postgrest as well (11.2.1 in tag,
11.2.0 in main branch), guess some people just don't use their main
branch to have their latest features for some reason.

From ivanperezdominguez at gmail.com  Mon Oct 23 00:30:53 2023
From: ivanperezdominguez at gmail.com (Ivan Perez)
Date: Sun, 22 Oct 2023 17:30:53 -0700
Subject: [Haskell-cafe] Hackage not building package
Message-ID: <CACZKWEK26OZL2Z7Qc29m-d5VJ7uS3v7C8ZW1ja1Vwn5-_b-65g@mail.gmail.com>

Hi,

I recently uploaded a package (
https://hackage.haskell.org/package/dunai-0.12.0) and hackage is not
building it.

I don't see info anywhere and I cannot re-trigger a build: attempting to do
so shows the message "Report not found -Build report does not exist"

Is everything ok with hackage?

Thanks

Ivan
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From bryan at haskell.foundation  Mon Oct 23 12:27:18 2023
From: bryan at haskell.foundation (Bryan Richter)
Date: Mon, 23 Oct 2023 15:27:18 +0300
Subject: [Haskell-cafe] Hackage not building package
In-Reply-To: <CACZKWEK26OZL2Z7Qc29m-d5VJ7uS3v7C8ZW1ja1Vwn5-_b-65g@mail.gmail.com>
References: <CACZKWEK26OZL2Z7Qc29m-d5VJ7uS3v7C8ZW1ja1Vwn5-_b-65g@mail.gmail.com>
Message-ID: <CACUTo6y4jyD4OHCyyV9KnZ18XGZw4vZ+gTVaUpOJds1gxZvKOg@mail.gmail.com>

I'm afraid that whatever happened may have been transitory. I see a build
log at https://hackage.haskell.org/package/dunai-0.12.0/reports/1 from
2023-10-23 07:29:30 UTC.

I wonder if there's any sort of status page for the doc builder?

On Mon, 23 Oct 2023 at 03:31, Ivan Perez <ivanperezdominguez at gmail.com>
wrote:

> Hi,
>
> I recently uploaded a package (
> https://hackage.haskell.org/package/dunai-0.12.0) and hackage is not
> building it.
>
> I don't see info anywhere and I cannot re-trigger a build: attempting to
> do so shows the message "Report not found -Build report does not exist"
>
> Is everything ok with hackage?
>
> Thanks
>
> Ivan
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
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From johannes.waldmann at htwk-leipzig.de  Wed Oct 25 16:37:18 2023
From: johannes.waldmann at htwk-leipzig.de (Johannes Waldmann)
Date: Wed, 25 Oct 2023 18:37:18 +0200
Subject: [Haskell-cafe] when does ghc(i) expand type synonyms?
Message-ID: <3c5d4f2f-bb90-4f3c-b8bf-95bfee3975ac@htwk-leipzig.de>

Dear cafe,

my students were asking:
why are types printed differently here?

ghci> :set +t

ghci> "foo"
"foo"
it :: String

ghci> reverse "foo"
"oof"
it :: [Char]

... and I add

ghci> fst ("foo", 42)
"foo"
it :: String

compiler docs do not really explain the difference
https://downloads.haskell.org/ghc/latest/docs/users_guide/ghci.html#ghci-cmd-:set%20+t
(it says "display the type of .." while technically it is
"display some representation of the type of ..."?)

I found this explanation of a somewhat related issue
https://gitlab.haskell.org/ghc/ghc/-/issues/9183#note_83743


While playing around with this, I noticed:

ghci> let x = "foo" in (x <> reverse x)
"foooof"
it :: String

ghci> let x = "foo" in (x ++ reverse x)
"foooof"
it :: [Char]


Well, it's just optics: when I extract the type programmatically,
the synonym necessarily does get expanded

ghci> import Data.Data
ghci> typeOf (let x = "foo" in (x <> reverse x))
[Char]
it :: TypeRep

- Johannes


From haskellcafe at dandart.co.uk  Wed Oct 25 17:06:36 2023
From: haskellcafe at dandart.co.uk (Dan Dart)
Date: Wed, 25 Oct 2023 18:06:36 +0100
Subject: [Haskell-cafe] when does ghc(i) expand type synonyms?
In-Reply-To: <3c5d4f2f-bb90-4f3c-b8bf-95bfee3975ac@htwk-leipzig.de>
References: <3c5d4f2f-bb90-4f3c-b8bf-95bfee3975ac@htwk-leipzig.de>
Message-ID: <CADNJRYFFh8GWY6F0CntEGWeJayiYF_uvgzJKfTjXcJzOn4_yRQ@mail.gmail.com>

Adjacently, I think a valuable question to ask is "how can you set
type alias defaults in things like :t and in errors?"

From olf at aatal-apotheke.de  Thu Oct 26 19:38:21 2023
From: olf at aatal-apotheke.de (Olaf Klinke)
Date: Thu, 26 Oct 2023 21:38:21 +0200
Subject: [Haskell-cafe] when does ghc(i) expand type synonyms?
Message-ID: <4e89e0cfc0ba6a82fa08990cfd91bbd7559f3696.camel@aatal-apotheke.de>

> ghci> :set +t
> 
> ghci> "foo"
> "foo"
> it :: String
> 
> ghci> reverse "foo"
> "oof"
> it :: [Char]

I'm not a GHC expert, but my guess is:
It must have something to do with unifying the argument types with the
type signature of the function.
In (<>), the two argument and the result types are identical. Hence it
can be safely said that 
    x <> whatever
as long as this expression is valid, has the same type as x. In
contrast, the result type of (++) is always of the shape [a]. Hence
String gets unified with [a] which forces expansion of the type
synonym. Consider:
    class Foo a where {rev :: a -> a; conc :: a -> a -> a}
    instance Foo [a] where {rev = reverse; conc = (++)}
    revconc :: Foo a => a -> a; revconc a = conc a (rev a)
    :t revconc ("foo" :: String)
    revconc ("foo" :: String) :: String
So as long has you hide (++) in a type signature that proves input and
output are the same, synonyms don't get expanded. 

Olaf


From capn.freako at gmail.com  Fri Oct 27 18:36:53 2023
From: capn.freako at gmail.com (David Banas)
Date: Fri, 27 Oct 2023 11:36:53 -0700
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into the
	IO monad?
Message-ID: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>

Hi all,

What is the simplest way to translate a non-monadic line of Haskell code, such as:

res = map foo xs `using` parList rseq

For use in the IO monad?

This doesn’t work:

res <- mapM fooM xs `using` parTraversable rseq

complaining:

No Traversable instance for IO.

Thanks,
-db

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From tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk  Fri Oct 27 18:43:07 2023
From: tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk (Tom Ellis)
Date: Fri, 27 Oct 2023 19:43:07 +0100
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
 the IO monad?
In-Reply-To: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
Message-ID: <ZTwEu9N6x85yD3pD@cloudinit-builder>

On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
> What is the simplest way to translate a non-monadic line of Haskell code, such as:
> 
> res = map foo xs `using` parList rseq
> 
> For use in the IO monad?
> 
> This doesn’t work:
> 
> res <- mapM fooM xs `using` parTraversable rseq

The docs for Control.Parallel.Strategies say "The parallel tasks
evaluated by a Strategy may have no side effects. For
non-deterministic parallel programming, see Control.Concurrent."[1].
So I guess you should look into Control.Concurrent[2].

Tom

[1] https://www.stackage.org/haddock/lts-21.17/parallel-3.2.2.0/Control-Parallel-Strategies.html#v:using

[2] https://www.stackage.org/haddock/lts-21.17/base-4.17.2.0/Control-Concurrent.html

From allbery.b at gmail.com  Fri Oct 27 18:48:29 2023
From: allbery.b at gmail.com (Brandon Allbery)
Date: Fri, 27 Oct 2023 18:48:29 +0000
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
 the IO monad?
In-Reply-To: <ZTwEu9N6x85yD3pD@cloudinit-builder>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
 <ZTwEu9N6x85yD3pD@cloudinit-builder>
Message-ID: <CAKFCL4WC3DXuy2bdMz6C5mPo7V_HB3srFOMQ2MNwYxjuqjoS1w@mail.gmail.com>

Doesn't `async` have things for this?

On Fri, Oct 27, 2023 at 6:43 PM Tom Ellis <
tom-lists-haskell-cafe-2023 at jaguarpaw.co.uk> wrote:

> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
> > What is the simplest way to translate a non-monadic line of Haskell
> code, such as:
> >
> > res = map foo xs `using` parList rseq
> >
> > For use in the IO monad?
> >
> > This doesn’t work:
> >
> > res <- mapM fooM xs `using` parTraversable rseq
>
> The docs for Control.Parallel.Strategies say "The parallel tasks
> evaluated by a Strategy may have no side effects. For
> non-deterministic parallel programming, see Control.Concurrent."[1].
> So I guess you should look into Control.Concurrent[2].
>
> Tom
>
> [1]
> https://www.stackage.org/haddock/lts-21.17/parallel-3.2.2.0/Control-Parallel-Strategies.html#v:using
>
> [2]
> https://www.stackage.org/haddock/lts-21.17/base-4.17.2.0/Control-Concurrent.html
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.



-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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From ietf-dane at dukhovni.org  Fri Oct 27 18:51:52 2023
From: ietf-dane at dukhovni.org (Viktor Dukhovni)
Date: Fri, 27 Oct 2023 14:51:52 -0400
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
 the IO monad?
In-Reply-To: <ZTwEu9N6x85yD3pD@cloudinit-builder>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
 <ZTwEu9N6x85yD3pD@cloudinit-builder>
Message-ID: <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>

On Fri, Oct 27, 2023 at 07:43:07PM +0100, Tom Ellis wrote:
> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
> > What is the simplest way to translate a non-monadic line of Haskell code, such as:
> > 
> > res = map foo xs `using` parList rseq
> > 
> > For use in the IO monad?
> > 
> > This doesn’t work:
> > 
> > res <- mapM fooM xs `using` parTraversable rseq
> 
> The docs for Control.Parallel.Strategies say "The parallel tasks
> evaluated by a Strategy may have no side effects. For
> non-deterministic parallel programming, see Control.Concurrent."[1].
> So I guess you should look into Control.Concurrent[2].

For a more friendly interface:

    https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html

If the number of concurrent tasks is reasonably modest, a good fit could
be `mapConcurrently`.

For much larger numbers of tasks, it is best to run the jobs at a
bounded concurrency, which may bring a BoundedChan to which the items to
process are written, another to which results are written and a set of
threads that do the processing, repeatedly reading more data until the
channel is drained. 

*The* book on subject is: https://simonmar.github.io/pages/pcph.html

--
    Viktor.

From capn.freako at gmail.com  Fri Oct 27 19:04:36 2023
From: capn.freako at gmail.com (David Banas)
Date: Fri, 27 Oct 2023 12:04:36 -0700
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
	the IO monad?
In-Reply-To: <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
 <ZTwEu9N6x85yD3pD@cloudinit-builder> <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>
Message-ID: <F6DE02E0-F094-46F7-9D0F-65A3F8A5E255@gmail.com>

Thank you all for the quick replies!
`mapConcurrently` was exactly what I needed. :)
-db


> On Oct 27, 2023, at 11:51 AM, Viktor Dukhovni <ietf-dane at dukhovni.org> wrote:
> 
> On Fri, Oct 27, 2023 at 07:43:07PM +0100, Tom Ellis wrote:
>> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
>>> What is the simplest way to translate a non-monadic line of Haskell code, such as:
>>> 
>>> res = map foo xs `using` parList rseq
>>> 
>>> For use in the IO monad?
>>> 
>>> This doesn’t work:
>>> 
>>> res <- mapM fooM xs `using` parTraversable rseq
>> 
>> The docs for Control.Parallel.Strategies say "The parallel tasks
>> evaluated by a Strategy may have no side effects. For
>> non-deterministic parallel programming, see Control.Concurrent."[1].
>> So I guess you should look into Control.Concurrent[2].
> 
> For a more friendly interface:
> 
>    https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html <https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html>
> 
> If the number of concurrent tasks is reasonably modest, a good fit could
> be `mapConcurrently`.
> 
> For much larger numbers of tasks, it is best to run the jobs at a
> bounded concurrency, which may bring a BoundedChan to which the items to
> process are written, another to which results are written and a set of
> threads that do the processing, repeatedly reading more data until the
> channel is drained. 
> 
> *The* book on subject is: https://simonmar.github.io/pages/pcph.html <https://simonmar.github.io/pages/pcph.html>
> 
> --
>    Viktor.
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe <http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe>
> Only members subscribed via the mailman list are allowed to post.

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From capn.freako at gmail.com  Fri Oct 27 19:14:30 2023
From: capn.freako at gmail.com (David Banas)
Date: Fri, 27 Oct 2023 12:14:30 -0700
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
	the IO monad?
In-Reply-To: <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
 <ZTwEu9N6x85yD3pD@cloudinit-builder> <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>
Message-ID: <28F88A7A-BCEE-4C4A-931C-A101FE7162C4@gmail.com>

After switching to `mapConcurrently` I’m getting this:

  SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)

Is that to be expected?

-db


> On Oct 27, 2023, at 11:51 AM, Viktor Dukhovni <ietf-dane at dukhovni.org> wrote:
> 
> On Fri, Oct 27, 2023 at 07:43:07PM +0100, Tom Ellis wrote:
>> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
>>> What is the simplest way to translate a non-monadic line of Haskell code, such as:
>>> 
>>> res = map foo xs `using` parList rseq
>>> 
>>> For use in the IO monad?
>>> 
>>> This doesn’t work:
>>> 
>>> res <- mapM fooM xs `using` parTraversable rseq
>> 
>> The docs for Control.Parallel.Strategies say "The parallel tasks
>> evaluated by a Strategy may have no side effects. For
>> non-deterministic parallel programming, see Control.Concurrent."[1].
>> So I guess you should look into Control.Concurrent[2].
> 
> For a more friendly interface:
> 
>    https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html <https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html>
> 
> If the number of concurrent tasks is reasonably modest, a good fit could
> be `mapConcurrently`.
> 
> For much larger numbers of tasks, it is best to run the jobs at a
> bounded concurrency, which may bring a BoundedChan to which the items to
> process are written, another to which results are written and a set of
> threads that do the processing, repeatedly reading more data until the
> channel is drained. 
> 
> *The* book on subject is: https://simonmar.github.io/pages/pcph.html <https://simonmar.github.io/pages/pcph.html>
> 
> --
>    Viktor.
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe <http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe>
> Only members subscribed via the mailman list are allowed to post.

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From allbery.b at gmail.com  Fri Oct 27 19:23:25 2023
From: allbery.b at gmail.com (Brandon Allbery)
Date: Fri, 27 Oct 2023 19:23:25 +0000
Subject: [Haskell-cafe] Simplest way to move a ... `using` ... line into
 the IO monad?
In-Reply-To: <28F88A7A-BCEE-4C4A-931C-A101FE7162C4@gmail.com>
References: <E2C923F8-60E0-4F77-9B3C-1E92029DA67F@gmail.com>
 <ZTwEu9N6x85yD3pD@cloudinit-builder> <ZTwGyJ9kWtLqO6yP@straasha.imrryr.org>
 <28F88A7A-BCEE-4C4A-931C-A101FE7162C4@gmail.com>
Message-ID: <CAKFCL4XsGErs1V=gsdayg6VGcSoRZHOpdAqEZzm09u2z49k71Q@mail.gmail.com>

Yes, because `async` uses actual threads, not sparks like
`Control.Parallel.Strategies`.

On Fri, Oct 27, 2023 at 7:14 PM David Banas <capn.freako at gmail.com> wrote:

> After switching to `mapConcurrently` I’m getting this:
>
>   SPARKS: 0 (0 converted, 0 overflowed, 0 dud, 0 GC'd, 0 fizzled)
>
> Is that to be expected?
>
> -db
>
>
> On Oct 27, 2023, at 11:51 AM, Viktor Dukhovni <ietf-dane at dukhovni.org>
> wrote:
>
> On Fri, Oct 27, 2023 at 07:43:07PM +0100, Tom Ellis wrote:
>
> On Fri, Oct 27, 2023 at 11:36:53AM -0700, David Banas wrote:
>
> What is the simplest way to translate a non-monadic line of Haskell code,
> such as:
>
> res = map foo xs `using` parList rseq
>
> For use in the IO monad?
>
> This doesn’t work:
>
> res <- mapM fooM xs `using` parTraversable rseq
>
>
> The docs for Control.Parallel.Strategies say "The parallel tasks
> evaluated by a Strategy may have no side effects. For
> non-deterministic parallel programming, see Control.Concurrent."[1].
> So I guess you should look into Control.Concurrent[2].
>
>
> For a more friendly interface:
>
>
> https://hackage.haskell.org/package/async-2.2.4/docs/Control-Concurrent-Async.html
>
> If the number of concurrent tasks is reasonably modest, a good fit could
> be `mapConcurrently`.
>
> For much larger numbers of tasks, it is best to run the jobs at a
> bounded concurrency, which may bring a BoundedChan to which the items to
> process are written, another to which results are written and a set of
> threads that do the processing, repeatedly reading more data until the
> channel is drained.
>
> *The* book on subject is: https://simonmar.github.io/pages/pcph.html
>
> --
>    Viktor.
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
>
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.



-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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From capn.freako at gmail.com  Sat Oct 28 00:11:33 2023
From: capn.freako at gmail.com (David Banas)
Date: Fri, 27 Oct 2023 17:11:33 -0700
Subject: [Haskell-cafe] How to use the GPU in Apple M2 from Haskell?
Message-ID: <A9D9E60F-B3F5-41AC-83C9-86FA1D00F872@gmail.com>

Does anyone have a good reference for explicitly accessing the GPU in the new Apple M2 chip from a user Haskell program?


From capn.freako at gmail.com  Sat Oct 28 18:36:17 2023
From: capn.freako at gmail.com (David Banas)
Date: Sat, 28 Oct 2023 11:36:17 -0700
Subject: [Haskell-cafe] Should GHC 9.4.7 be native on MacBook Air M2?
Message-ID: <E56BB5B1-8B53-4B4F-98CD-AEACCE10D97E@gmail.com>

I’m working on a new MacBook Air M2.
I just bumped my current Haskell project to stack LTS-21.17, after catching up on the GHC porting effort news.
I did a stack clean / stack build and saw GHC 9.4.7 being installed, as expected, but still to the x86_64-osx directory:

% l ~/.stack/programs
x86_64-osx

% l ~/.stack/programs/x86_64-osx
ghc-8.10.3           ghc-8.10.4.tar.bz2   ghc-8.6.3.installed  ghc-9.0.2            ghc-9.2.2.tar.bz2    ghc-9.2.7.installed
ghc-8.10.3.installed ghc-8.4.3            ghc-8.6.3.tar.bz2    ghc-9.0.2.installed  ghc-9.2.5            ghc-9.2.7.tar.bz2
ghc-8.10.3.tar.bz2   ghc-8.4.3.installed  ghc-8.6.5            ghc-9.0.2.tar.bz2    ghc-9.2.5.installed  ghc-9.4.7
ghc-8.10.4           ghc-8.4.3.tar.bz2    ghc-8.6.5.installed  ghc-9.2.2            ghc-9.2.5.tar.bz2    ghc-9.4.7.installed
ghc-8.10.4.installed ghc-8.6.3            ghc-8.6.5.tar.bz2    ghc-9.2.2.installed  ghc-9.2.7            ghc-9.4.7.tar.bz2

I was expecting a native version; do I misunderstand something?

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From leah at vuxu.org  Sat Oct 28 18:56:07 2023
From: leah at vuxu.org (Leah Neukirchen)
Date: Sat, 28 Oct 2023 20:56:07 +0200
Subject: [Haskell-cafe] Munich Haskell Meeting, 2023-10-31 @ 19:30
Message-ID: <87zg02shiw.fsf@vuxu.org>

Dear all,

Next week, our monthly Munich Haskell Meeting will take place again on
Tuesday, October 31 at Iveria (Lindwurmstraße 159A) at 19h30.
For details see here:

http://muenchen.haskell.bayern/dates.html

If you plan to join, please add yourself to this nuudel so we can
reserve enough seats!  It is OK to add yourself to the nuudel
anonymously or pseudonymously.

https://nuudel.digitalcourage.de/7ST4pxNRVj3rGLdO

Everybody is welcome!

cu,
-- 
Leah Neukirchen  <leah at vuxu.org>  https://leahneukirchen.org/

From capn.freako at gmail.com  Sat Oct 28 19:09:42 2023
From: capn.freako at gmail.com (David Banas)
Date: Sat, 28 Oct 2023 12:09:42 -0700
Subject: [Haskell-cafe] Should GHC 9.4.7 be native on MacBook Air M2?
Message-ID: <DDAE02C3-8D9C-463F-935F-4439A72E1926@gmail.com>

Ah, I needed this line in my stack.yaml file:

arch: aarch64

Why is that?
Shouldn’t it use the native architecture if it can support it?

-db

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From carter.schonwald at gmail.com  Sat Oct 28 22:17:53 2023
From: carter.schonwald at gmail.com (Carter Schonwald)
Date: Sat, 28 Oct 2023 18:17:53 -0400
Subject: [Haskell-cafe] Should GHC 9.4.7 be native on MacBook Air M2?
In-Reply-To: <DDAE02C3-8D9C-463F-935F-4439A72E1926@gmail.com>
References: <DDAE02C3-8D9C-463F-935F-4439A72E1926@gmail.com>
Message-ID: <CAHYVw0z-rXt6g1xcZh6o6zwrYu4oXBNkkKnyqAzDNsyLGYRVgQ@mail.gmail.com>

Sounds like a Ux issue in stack….

On Sat, Oct 28, 2023 at 3:09 PM David Banas <capn.freako at gmail.com> wrote:

> Ah, I needed this line in my stack.yaml file:
>
> arch: aarch64
>
> Why is that?
> Shouldn’t it use the native architecture if it can support it?
>
> -db
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
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From carter.schonwald at gmail.com  Sat Oct 28 22:19:09 2023
From: carter.schonwald at gmail.com (Carter Schonwald)
Date: Sat, 28 Oct 2023 18:19:09 -0400
Subject: [Haskell-cafe] How to use the GPU in Apple M2 from Haskell?
In-Reply-To: <A9D9E60F-B3F5-41AC-83C9-86FA1D00F872@gmail.com>
References: <A9D9E60F-B3F5-41AC-83C9-86FA1D00F872@gmail.com>
Message-ID: <CAHYVw0yMur22EBPjrvYFVQ-y4uqSMUqnrycpVx8=J1aXMZK1_w@mail.gmail.com>

Write a program in metal shaders and link a c wrapper for the c++ wrapper
of metal api into Haskell via the ffi. Or use opencl / OpenGL APIs that
still work despite being deprecated.

On Fri, Oct 27, 2023 at 8:11 PM David Banas <capn.freako at gmail.com> wrote:

> Does anyone have a good reference for explicitly accessing the GPU in the
> new Apple M2 chip from a user Haskell program?
>
> _______________________________________________
> Haskell-Cafe mailing list
> To (un)subscribe, modify options or view archives go to:
> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
> Only members subscribed via the mailman list are allowed to post.
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From f.occhipinti at gmail.com  Mon Oct 30 19:19:57 2023
From: f.occhipinti at gmail.com (fran)
Date: Mon, 30 Oct 2023 20:19:57 +0100
Subject: [Haskell-cafe] Munich Haskell Meeting, 2023-10-31 @ 19:30
In-Reply-To: <87zg02shiw.fsf@vuxu.org>
References: <87zg02shiw.fsf@vuxu.org>
Message-ID: <17b8bc13-2ce5-5503-595e-0f3af76b8811@gmail.com>

Nice! Of course, like most participants to this mailing list, i don't 
live in Munich and i would not take a flight to participate to a meetup 
so... where is the link to follow the event remotely?

On 28.10.23 20:56, Leah Neukirchen wrote:
> Dear all,
>
> Next week, our monthly Munich Haskell Meeting will take place again on
> Tuesday, October 31 at Iveria (Lindwurmstraße 159A) at 19h30.
> For details see here:
>
> http://muenchen.haskell.bayern/dates.html
>
> If you plan to join, please add yourself to this nuudel so we can
> reserve enough seats!  It is OK to add yourself to the nuudel
> anonymously or pseudonymously.
>
> https://nuudel.digitalcourage.de/7ST4pxNRVj3rGLdO
>
> Everybody is welcome!
>
> cu,
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From travis at athougies.net  Tue Oct 31 22:31:34 2023
From: travis at athougies.net (Travis Athougies)
Date: Tue, 31 Oct 2023 15:31:34 -0700
Subject: [Haskell-cafe] Question on Lexing Haskell syntax
Message-ID: <ba7f4670193e0f80848e75c6630af3916e7a2de8.camel@athougies.net>

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Hash: SHA512

According to the Haskell report [1] (See Note 5), a virtual `}` token
is inserted if parsing the next token would cause a parse error and the
indentation stack is non-empty.

I'm trying to lex and parse Haskell source and this sort of interplay
(which requires two-way communication between lexer and parser) makes
it very difficult to write a conformant implementation.

I can't change the standard (obviously), but I'm wondering if this is
actually what GHC (de facto the only Haskell compiler) does, or if it
applies some other rule. If so, does anyone know the exact mechanism of
its implementation?

I've been programming Haskell for more than a decade, and while I have
an intuitive understanding of the indentation rules, I would have
assumed the source could be lexed without also having a parser. In
particular, the note seems to imply that the main purpose of this is to
properly lex `let`/`in` bindings. Perhaps there's an alternate
equivalent rule?

Curious to hear other's thoughts.

Travis

[1]
https://www.haskell.org/onlinereport/haskell2010/haskellch10.html#x17-17800010.3
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