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[ANNOUNCE] GHC 9.8.1 is now available
by Ben Gamari 13 Oct '23

13 Oct '23

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-d… [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-s… [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-u… [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-w… [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-d… [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-j… [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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ambiguous type variable question
by Zoran Bošnjak 11 Oct '23

11 Oct '23

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

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Call for Contributions: BOB 2024 [March 15, Deadline Nov 17]
by Stefan Wehr 11 Oct '23

11 Oct '23

================================================================================ 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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[Haskell] [ANNOUNCE] Haskell Language Server 2.4.0.0 released
by Zubin Duggal 10 Oct '23

10 Oct '23

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(a)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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XMonad for Wayland — seeking help
by Brandon Allbery 08 Oct '23

08 Oct '23

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(a)gmail.com

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[ANNOUNCE] Agda 2.6.4
by Andreas Abel 06 Oct '23

06 Oct '23

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(a)lists.chalmers.se https://lists.chalmers.se/mailman/listinfo/agda

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Meaning of fizzled sparks?
by David Banas 04 Oct '23

04 Oct '23

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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CFP, PEPM 2024 ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation
by Meng Wang 03 Oct '23

03 Oct '23

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(a)uu.nl<mailto:g.k.keller@uu.nl>) and Meng Wang (meng.wang(a)bristol.ac.uk<mailto:meng.wang@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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Meaning of "GC waiting" in ThreadScope?
by David Banas 03 Oct '23

03 Oct '23

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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two HLS processes with same name
by Dennis Raddle 03 Oct '23

03 Oct '23

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

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