- Haskell-Cafe - Haskell.org

[ANN] Copilot 4.6.1
by Ivan Perez 12 Feb '26

12 Feb '26

Hi café! We are really excited to announce Copilot 4.6.1 [1, 2]. Copilot is a stream-based EDSL in Haskell for writing and monitoring embedded systems, with an emphasis on correctness and hard realtime requirements. Copilot is typically used as a high-level runtime verification framework, and supports temporal logic (LTL, PTLTL and MTL), clocks and voting algorithms. Compilation to Bluespec, to target FPGAs, is also supported. Copilot is NASA Class D open-source software, and is being used at NASA in drone test flights. Through the NASA tool Ogma [3] (also written in Haskell), Copilot also serves as a programming language and runtime framework for NASA's Core Flight System, Robot Operating System (ROS 2) and FPrime (the software framework used in the Mars Helicopter). Ogma now supports producing flight and robotics applications directly in Copilot, not just for monitoring, but for implementing the logic of the applications themselves. This release improves the Bluespec backend, fixing corner cases related to the generation of Bluespec (and thus Verilog). The release also introduces some general maintenance improvements. Copilot is compatible with versions of GHC from 8.6 to 9.12. This release has been made possible thanks to Chris Hathhorn (Galois) and Trevor Kann (Galois). The team also benefited from discussions with Ryan Scott (Galois). We are grateful to all of them for their contributions, and for making Copilot better every day. For details on this release, see [1]. As always, we're releasing exactly 2 months since the last release. Our next release is scheduled for Mar 7th, 2026. We want to remind the community that Copilot is now accepting code contributions from external participants again. Please see the discussions and the issues in our Github repo [4] to learn how to participate. Current emphasis is on using Copilot for full data processing applications (e.g, system control, arduinos, rovers, drones), improving usability, performance, and stability, increasing test coverage, removing unnecessary dependencies, hiding internal definitions, and formatting the code to meet our coding standards. Users are encouraged to participate by opening issues, asking questions, extending the implementation, and sending bug fixes. Happy Haskelling! Ivan -- [1] https://github.com/Copilot-Language/copilot/releases/tag/v4.6.1 [2] https://hackage.haskell.org/package/copilot [3] https://github.com/nasa/ogma [4] https://github.com/Copilot-Language/copilot

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CLC Elections January 2026
by Teo Camarasu 06 Feb '26

06 Feb '26

Happy new year! The Core Libraries Committee seeks nominations for three seats. ## What is CLC? CLC is a volunteer body, primarily tasked with management of the API of [`base`](https://hackage.haskell.org/package/base) package, but also owning so-called Core Libraries and responsible for [PVP](https://pvp.haskell.org/). You can find more at [our home page](https://github.com/haskell/core-libraries-committee/?tab=readme-ov-fi…. ## Who should apply? Anyone who meets the following criteria should apply: * Candidates should have enough bandwidth to review merge requests to `base` on a semi-frequent basis (~3-4 per month), and sustain this for their 3 years term in a healthy manner. * Candidates should be able to contribute opinions and analysis to issues raised by the community as a part of the CLC proposal process on a semi-frequent basis (~7 per month). * Candidates should be good communicators, and at least be able to articulate to the CLC team when they will be available vs. unavailable. * Candidates should be productive, and be able to follow through on merge requests and conversations to their completion in a diligent and timely manner. We encourage any and all who satisfy these requirements to apply. Please note that we are not looking for the biggest galaxy brain in the room – quite the opposite. We are looking for productive, motivated individuals who want to help support the ecosystem that we love. As such, we hope to build a broad sample of the community. ## How can I apply? To apply for one of these positions, send an email to [clc.nominations.2026@fastmail.com](mailto:clc.nominations.2026@fastmail.com) with: * The subject “CLC Election January 2026 - {your name}”. * Why you think you’re a good fit given the above criteria. * If applicable, please point us to some code you’ve written. Please apply before Feb 2. Cheers, Teo

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NEU: Festschrift and Workshop in Honor of David Basin (Deadline: 21st May 2026)
by Achim D. Brucker 26 Jan '26

26 Jan '26

Dear Fellow Researchers! Our dear colleague and friend David Basin is turning 65 in December 2026 and this has to be celebrated! We therefore organize a Festschrift and a Fest to celebrate his birthday and his extensive research contributions! The Fest/celebration itself will be held as a one-day event on the 15th of January 2027 at ETH Zürich. We have already checked that David is available. You do not have to keep it a secret - on the contrary, it is great if you share this message with anybody who might like to contribute! We hereby cordially invite you to contribute an article to the Festschrift and present it at the Fest. We welcome contributions in all areas close to David's research and interests, including but not limited to security, privacy, formal methods, logic, automated reasoning, model checking, theorem proving, software engineering, bridge, juggling, biking and more. The articles will be lightly reviewed by the Festschrift committee, and the proceedings will be published by Springer Heidelberg in the LNCS series. David will of course love to receive a research article from you, but also short personal articles that celebrate the history and friendship with David will be very much appreciated. We would like to set a deadline for submissions at the 21st of May 2026 via our submission site <https://easychair.org/conferences/?conf=feschi2027>. Articles should be formatted in Springer’s LNCS style and not exceed 5 pages for personal articles and 16 pages for scientific articles. If you have a work that you would like to contribute that does not fit into this page limit, it might be possible, but please reach out to us first. There will be no participation fee for the Fest and coffee breaks, lunch, and dinner will be included. Travel and accommodation costs are at the expense of the participants. We are happy to provide hotel suggestions for Zürich. Submission Information: * Format: 16 pages in LNCS format, templates available at: <https://www.springer.com/gp/computer-science/lncs/conference-proceedings-gu…> * Submission: <https://easychair.org/conferences/?conf=feschi2027> * Website (under construction) with updates and further information: <https://feschi2027.github.io/> * Timeline: * Submission: 21 May 2026 * Notification: end of June 2026 (to be confirmed) * Camera Ready Copy: early September 2026 (to be confirmed) Please let us know if you have any questions! Best wishes Achim D. Brucker (University of Exeter) Sebastian Mödersheim (Danmarks Tekniske Universitet) Christoph Sprenger (ETH Zürich) Luca Viganò (King’s College London)

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Can I coerce type constructors to Any?
by Tom Ellis 23 Jan '26

23 Jan '26

The documentation for Any says: > The type constructor Any is type to which you can unsafely coerce > any lifted type, and back. More concretely, for a lifted type t and > value x :: t, unsafeCoerce (unsafeCoerce x :: Any) :: t is > equivalent to x. https://www.stackage.org/haddock/lts-24.28/base-4.20.2.0/GHC-Base.html#t:Any Is this also true of type constructors? For example, could I coerce `f x` to `Any x`? (assuming f maps lifted types to lifted types) In particular I'm interested in things like data C f where MkC :: (forall a. Monad (f a)) => C newtype CD f = MkCD (C Any) putCD :: C f -> CD f putCD c = MkCD (unsafeCoerce c) getCD :: CD f -> C f getCD (MkCD cd) = unsafeCoerce cd Is that sound? Thanks, Tom

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GSoC 2026 Call for Ideas
by Aaron Allen 12 Jan '26

12 Jan '26

Dear Haskellers, Google Summer of Code is a long-running program by Google that supports Open Source projects. Haskell has been involved in the Google Summer of Code program almost since its inception and we are hoping to participate again in 2026! In order to do this we need a collection of ideas for participants to select from. In the past this has included significant improvements to Haskell projects such as GHC, Cabal, and HLS - and it can include your project as well! This is a great opportunity to find new contributors for your project and many past participants have become involved long-term. You can find more info and instructions on how to participate here: https://summer.haskell.org/ideas.html.

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2nd Call for Participation: BOB 2026 (Berlin, Mar 13)
by Michael Sperber 12 Jan '26

12 Jan '26

Note the early-bird discount runs out on Friday! ========================================================================= BOB 2026 Conference “What happens if we simply use what’s best?” March 13, 2026, Berlin https://bobkonf.de/2026/ Program: https://bobkonf.de/2026/program.html Registration: https://bobkonf.de/2026/registration.html ========================================================================= BOB conference is a place for developers, architects, and decision-makers to explore technologies beyond the mainstream in software development and to find the best tools available to software developers today. Our goal is for all participants of BOB to return home with new insights that enable them to improve their own software development experience. The program features 16 talks and 8 tutorials on current topics: https://bobkonf.de/2026/program.html Talk subjects includes functional programming, software architecture, formal methods, accessibility, UI programming, reactive systems, and domain-driven design. BOB tutorial include sessions on TypeScript, OCaml, Haskell, Agda, accessibility, and reactive systems. Stefan Kaufmann will give the keynote talk on digital sovereignty. Registration is open - many discount options - including limited early-bird discounts - are available, as are grants for members of groups underrepresented in tech. https://bobkonf.de/2026/registration.html

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Critical code generation bug with GHC 9.12.3
by Zubin Duggal 08 Jan '26

08 Jan '26

Hello all, Unfortunately we discovered a major code generation regression in GHC 9.12.3 that results in incorrect runtime results for certain operations involving sub-word divisions. We recommend avoiding upgrading to this minor release at this time. See https://gitlab.haskell.org/ghc/ghc/-/issues/26711 for more details. This is the same bug that affected GHC 9.12.1. A patch re-introducing this bug was accidently backported onto the 9.12.3 branch and went unnoticed throughout the testing period. We are taking steps to ensure similar situations are less likely to occur again, including looking at ways to improve our testing procedure for minor GHC release, potentially using the Stackage infrastructure to run the testsuites of a broad range of packages to detect such issues. We are also starting to prepare GHC 9.12.4 with a fix, which we hope to release soon. However, a significant amount of time has passed since the initial set of backports to GHC 9.12.3 were completed, which means that a number of merge requests addressing issues of various severities has been marked for backporting to the GHC 9.12 branch. We are in the process of triaging this list and preparing a robust and reliable GHC 9.12.4 release. Thanks, Zubin.

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GHC 9.14.1 is now available
by Zubin Duggal 27 Dec '25

27 Dec '25

The GHC developers are very pleased to announce the release of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. GHC 9.14 brings a number of new features and improvements, including: * Significant improvements in specialisation: * The `SPECIALISE` pragma now allows use of type application syntax * The `SPECIALISE` pragma can be used to specialise for expression arguments as well as type arguments. * Specialisation is now considerably more reliable in the presence of `newtype`s * Significant GHCi improvements including: * Correctness and performance improvements in the bytecode interpreter * Features in the GHCi debugger * Support for multiple home units in GHCi * Implementation of the [Explicit Level Imports proposal][levels] * `RequiredTypeArguments` can now be used in more contexts * Greatly improved [SSE/AVX2 support][sse] in the x86 native code generator backend * Initial native code generator support for LoongArch * The WebAssembly backend now supports [evaluation via the interpreter][wasm-ghci], allowing GHCi and TemplateHaskell evaluation, including `foreign import javascript` usage from within the browser * A new primop [`annotateStack#`][annotate-stack] for pushing arbitrary data onto the call stack for later extraction when decoding stack traces * [`-Wincomplete-record-selectors`][incomplete-selectors] is now part of `-Wall`. Libraries compiled with `-Werror` may need adjustment. * A major update of the Windows toolchain * Improved compatibility with [macOS Tahoe][macos] * ... and many more A full accounting of changes can be found in the [release notes][]. See the [migration guide][] for guidance on migrating programs to this release. Note that while this release makes many improvements in the specialisation optimisation, polymorphic specialisation remains disabled by default in the release due to concern over regressions of the sort identified in [#26329][T26329]. Users needing more aggressive specialisation can explicitly enable this feature with the `-fpolymorphic-specialisation` flag. Depending upon our experience with 9.14.1, we may enable this feature by default in a later minor release. GHC development is sponsored by: * [Juspay](https://juspay.com/) * [QBayLogic](https://qbaylogic.com/) * [Channable](https://www.channable.com/) * [Haskell Foundation](https://haskell.foundation/) * [Serokell](https://serokell.io/) * [Well-Typed](https://well-typed.com/) * [Tweag](https://www.tweag.io/) * [Dotcom-Monitor](https://www.dotcom-monitor.com/) * [LoadView](https://www.loadview-testing.com/) * [Web Hosting Buddy](https://webhostingbuddy.com/) * [Find My Electric](https://www.findmyelectric.com/) * [Standard Chartered](https://www.sc.com) * [UpCloud](https://upcloud.com) We would like to thank these sponsors 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 comprises this release. As always, do give this release a try and open a [ticket][] if you see anything amiss. [downloads.haskell.org] https://downloads.haskell.org/ghc/9.14.1 [release notes]: https://downloads.haskell.org/ghc/9.14.1/docs/users_guide/9.14.1-notes.html [ticket]: https://gitlab.haskell.org/ghc/homepage/-/issues/new [macos]: https://gitlab.haskell.org/ghc/ghc/-/issues/26166 [T26329]: https://gitlab.haskell.org/ghc/ghc/-/issues/26329 [levels]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0682-e… [wasm-ghci]: https://www.tweag.io/blog/2025-04-17-wasm-ghci-browser/ [incomplete-selectors]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0516-i… [annotate-stack]: https://gitlab.haskell.org/ghc/ghc/-/issues/26218 [migration guide]: https://gitlab.haskell.org/ghc/ghc/-/wikis/migration/9.14 [sse]: https://gitlab.haskell.org/ghc/ghc/-/issues/25030

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GHC 9.12.3 is now available
by Zubin Duggal 27 Dec '25

27 Dec '25

The GHC developers are very pleased to announce the release of GHC 9.12.3. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. GHC 9.12.3 is a bug-fix release fixing many issues of a variety of severities and scopes, including: * Fix a number of crashes and miscompilations in the compiler frontend (#25004, #25960, #26256) * Improvements to efficiency of the runtime linker (#26009) * Fixes for several bugs in bytecode generation and the bytecode interpreter (#23210, #25975, #25750) * Fixes for bugs in the handling of WHITEHOLEs in the RTS (#26204, #26205) * Fix incorrect code generation for SSE vector operations (#25859) * Fix a use-after-free in the Windows runtime linker (#26613) * Support for synchronous JSFFI exports for the wasm backend * And many more! A full accounting of these fixes can be found in the [release notes][]. As always, GHC's release status, including planned future releases, can be found on the GHC Wiki [status][]. GHC development is sponsored by: * [Juspay](https://juspay.com/) * [QBayLogic](https://qbaylogic.com/) * [Channable](https://www.channable.com/) * [Haskell Foundation](https://haskell.foundation/) * [Serokell](https://serokell.io/) * [Well-Typed](https://well-typed.com/) * [Tweag](https://www.tweag.io/) * [Dotcom-Monitor](https://www.dotcom-monitor.com/) * [LoadView](https://www.loadview-testing.com/) * [Web Hosting Buddy](https://webhostingbuddy.com/) * [Find My Electric](https://www.findmyelectric.com/) * [Standard Chartered](https://www.sc.com) * [UpCloud](https://upcloud.com) * [Mercury](https://mercury.com) We would like to thank these sponsors 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. As always, do give this release a try and open a [ticket][] if you see anything amiss. [release notes]: https://downloads.haskell.org/~ghc/9.12.3/docs/users_guide/9.12.3-notes.html [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.3 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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[TFP 2026] 1st Call for Participation for the 27th International Symposium on Trends in Functional Programming, Odense, Denmark, January 27-29 2026 - TFPiE Jan 26
by Peter Achten 24 Dec '25

24 Dec '25

TFP 2026 -- Call For Participation (trendsfp.github.io [1]) Venue TFPiE and TFP will take place in-person in Odense, Denmark, at the University of Southern Denmark. Dates Early registration: 31 December, 2025 Late registration: 20 January , 2026 TFPiE Workshop: Monday 26 January, 2026 TFP Symposium: Tuesday 27 - Thursday 29 January, 2026 The Symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming, taking a broad view of current and future trends in the area. It aspires to be a lively environment for presenting the latest research results, and other contributions. Keynote speakers We are happy to have the following keynotes in the programme: Alex Gerdes (TFPiE), Gothenburg University and Chalmers: "Generating Feedback from Rewrite Strategies for Interactive Exercises" Joachim Breitner, Lean Focused Research Organization: "Lean Highlights" Ohad Kammar, University of Edinburgh: "Synthetic Convolution" András Kovács, Gothenburg University and Chalmers: TBA Programme We have 13 paper presentations, as well as invited talks. A preliminary programme schedule can be found here: trendsfp.github.io/schedule.html [2] Excursion and banquet In the afternoon and evening of Wednesday January 28th we have an excursion to H.C. Andersen Museum, followed by a break before heading to Madklubben for the conference banquet. Travel Scholarship Thanks to the generous support from the Carlsberg Foundation, we are able to offer travel scholarships (DKK 3000 ~ USD 470 ~ EUR 400) to young researchers traveling to attend TFP 2026 in Odense, Denmark. Information on how to apply can be found here: https://trendsfp.github.io/scholarship.html Links: ------ [1] https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftrendsfp.g… [2] https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Ftrendsfp.g…

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