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Two Haskell Talks from Bellroy at Melbourne Compose Group May Meetup
by theghostjw＠gmail.com 02 May '26

02 May '26

We're thrilled to have two Bellroy Haskellers presenting a double-feature at Melbourne Compose Group. Michael Webb (CTO) will share how Bellroy built and scaled a $120M+ brand with a tiny Haskell team. Jack Kelly (Staff Engineer) will walk through deploying Haskell in the cloud with an opinionated guide to Haskell on AWS Lambda. Whether you're using Haskell in production, curious about serverless, or just want to see how a small team moves fast without fear, come along! The Talks Michael Webb - CTO Maximum Agency, Minimum Footguns Lessons from scaling a $120M+ carry brand with a tiny engineering team At Bellroy, we've built a small engineering team that moves fast, ships confidently, and hands real power to the people closest to the work - content editors, ops staff, marketers - without lying awake worrying about what they might break. The secret isn't process, approval chains, or change management theatre. It's that we've encoded the constraints that actually matter directly into our tools - many of them built in Haskell - and trusted our people with everything else. This talk is about the philosophy behind that approach: what it means to design for agency rather than safety, what cultural practices make such an approach practical and why a type system is the most underrated management tool in a company's arsenal. Jack Kelly - Staff Engineer Lambda on Lambda: Running Serverless Haskell Functions on AWS [AWS Lambda]([https://aws.amazon.com/lambda/](https://aws.amazon.com/lambda/)) is AWS's "function-as-a-service" offering, where your code runs in an isolated "microVM" on AWS-managed infrastructure and you pay only for the resources used while your code runs. Fitting your binaries into this model means making your code talk to some internal AWS APIs, and luckily the Haskell ecosystem has some good tools for doing this. In this talk, I'll explain at a high level what AWS Lambda is, how it executes your code, and then provide an opinionated guide and demo for getting your Haskell functions into the cloud. When and Where Format: Strictly IRL When: Thursday 21 May 2026, 6:00pm – 8:00pm Where: Kathleen Syme Centre, Activity Room 2, Carlton (Melbourne Victoria, Australia) RSVP: [luma](https://luma.com/uhdgct1v) About Melbourne Compose Group Melbourne Compose Group is the monthly in-person meetup for functional programmers in Melbourne, every 3rd Thursday of the month in Carlton. As always, newcomers welcome.

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Third CfP: Festschrift and Workshop in Honor of David Basin (Deadline extended to 11 June 2026)
by Achim D. Brucker 27 Apr '26

27 Apr '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: 11 June 2026 (extended) * 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) -- Prof. Achim Brucker | Chair in Cybersecurity & Head of Group | University of Exeter https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Storing a Haskellwiki-page fails
by X Y 24 Apr '26

24 Apr '26

L.S., After editing a page at wiki.haskell.org, I tried to store the page and got the following error message: Database error A database query error has occurred. This may indicate a bug in the software. [274dd5bf9e736eea1c9a5c34] 2026-04-23 13:41:25: Fatal exception of type "Wikimedia\Rdbms\DBQueryError" Can someone solve this please? Regards, ಹೆಂಕ್-ಜಾನ್ ವ್ಯಾನ್ ಟುಯ್ಲ್ Henk-Jan van Tuyl

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Wiki account creation
by Vanessa McHale 07 Apr '26

07 Apr '26

Would it be possible for me to get a Wiki account? I sent something to wiki-account-request(a)haskell.org but that has been quiet. Preferred username would be vem or vmchale Cheers, Vanessa McHale

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Aeson
by Ivan Perez 04 Apr '26

04 Apr '26

Hi Café The aeson (https://github.com/haskell/aeson) package hasn't seen updates in a while. The last one I see is from Oct 2025. It's getting out of date wrt new versions of dependencies available on Hackage, such as QuickCheck. It's also heavily depended on. What's the best course of action here? What can be done to get this updated? Thanks, Ivan

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Enriching errors in the "network" library
by Kazu Yamamoto 02 Apr '26

02 Apr '26

Hi all, For many years, users of the "network" library have been suffered from poor error handling. For example, the "bind" function displays an error message like the following, but it doesn't tell you which port you were trying to bind to. Network.Socket.bind: resource busy (Address already in use) I am working to improve this situation. The error message becomes as follows: Network.Socket.bind: resource busy (Address already in use [EADDRINUSE] <socket: 13> [::1]:53) If you're interested, please join the discussion: https://github.com/haskell/network/pull/610 P.S. In my opinion, Show IOException should display errno. Why doesn't it display? instance Show IOException where showsPrec p (IOError hdl iot loc s _errno fn) = (case fn of Nothing -> case hdl of Nothing -> id Just h -> showsPrec p h . showString ": " Just name -> showString name . showString ": ") . (case loc of "" -> id _ -> showString loc . showString ": ") . showsPrec p iot . (case s of "" -> id _ -> showString " (" . showString s . showString ")") --Kazu

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tls v2.3.1
by Kazu Yamamoto 31 Mar '26

31 Mar '26

Hi all, I have just released the "tls" library version 2.3.1. As I said before, this version uses ML-KEM (Post-Quantum Cryptography) by default. Since no changes to the existing code are necessary, I released this as a minor version. However, ClientHello and ServerHello become larger by more than 1000 bytes. If the world breaks down, I will deprecate v2.3.1 and re-release a major version. I've written an explanatory article in Japanese. If you're interested, please read it using machine translation. https://eng-blog.iij.ad.jp/archives/35451 --Kazu

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Re: HasCallStack constraint for maximum in Prelude?
by Olaf Klinke 27 Mar '26

27 Mar '26

> Mind you there's a conflict between the suggested `foldMap'` > implementation for Bounded elements and efficient implementations > with ordered Foldable collections (Map, IntMap, Set, ...). > > The latter, just return quickly return the least or greatest element > without paying a linear cost to perform the proposed fold. ... which is why functions like sum, product, maximum and minimum have become Foldable class methods, to be overridden whenever it is more efficient. I fail to see how your boundedMinimum reduces time complexity. It is still a general fold in the non-empty case. I wonder, though, how sustainable it is to bloat the Foldable interface with special cases of foldMap that can be overridden. What special monoid structures do exist that warrant a specialized fold implementation? We have (1) commutative monoids, such as Sum and Product, (2) semilattices, where (x<>) is idempotent for every x, (3) Short-circuiting monoids such as First and Last, where either (x<>) or (<>x) is constant for x /= mempty. Evidently, for cases (2) and (3) there are examples where the short- circuiting behavior of the monoid itself can be leveraged to short- circuit foldMap. Does anyone know of a real-world example where sum and product are overridden? All instances Hoogle turns up are O(n). I can't cast that into a type signature right now, but I feel all of null, sum, product, maximum, minimum can be unified given a suitable sub-class that relates the particular Foldable f to the contraint (Ord, Num etc.) present in the head of the function. Olaf

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GHC 9.12.4 is now available
by Zubin Duggal 27 Mar '26

27 Mar '26

The GHC developers are very pleased to announce the release of GHC 9.12.4. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][] and via [GHCup](https://www.haskell.org/ghcup/). GHC 9.12.4 is a bug-fix release fixing many issues of a variety of severities and scopes, including: * Fixed a critical code generation regression where sub-word division produced incorrect results (#26711, #26668), similar to the bug fixed in 9.12.2 * Numerous fixes for register allocation bugs, preventing data corruption when spilling and reloading registers (#26411, #26526, #26537, #26542, #26550) * Fixes for several compiler crashes, including issues with CSE (#25468), and the simplifier(#26681), implicit parameters (#26451), and the type-class specialiser (#26682) * Fixed cast worker/wrapper incorrectly firing on INLINE functions (#26903) * Fixed LLVM backend miscompilation of bit manipulation operations (#20645, #26065, #26109) * Fixed associated type family and data family instance changes not triggering recompilation (#26183, #26705) * Fixed negative type literals causing the compiler to hang (#26861) * Improvements to determinism of compiler output (#26846, #26858) * Fixes for eventlog shutdown deadlocks (#26573) and lost wakeups in the RTS (#26324) * Fixed split sections support on Windows (#26696, #26494) and the LLVM backend (#26770) * Fixes for the bytecode compiler, PPC native code generator, and Wasm backend * The runtime linker now supports COMMON symbols (#6107) * Improved backtrace support: backtraces for `error` exceptions are now evaluated at throw time * `NamedDefaults` now correctly requires the class to be standard or have an in-scope default declaration, and handles poly-kinded classes (#25775, #25778, #25882) * ... 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://gitlab.haskell.org/ghc/ghc/-/blob/ghc-9.12/docs/users_guide/9.12.4-… [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.4 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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Call for Submissions: ICFP 2026 Student Research Competition
by Kimball Germane 27 Mar '26

27 Mar '26

ICFP 2026 Student Research Competition Call for Submissions ICFP 2026 invites students to participate in the Student Research Competition in order to present their research and get feedback from prominent members of the programming language research community. The SRC consists of three rounds: * Submission of an extended abstract * Poster session at ICFP 2026 * Finalists' presentations at ICFP 2026 During the first round students submit an extended abstract detailing their research to be reviewed by the program committee. Those students whose abstracts get accepted advance to the poster session round which will take place during ICFP 2026. Winners of the poster session advance to the next round, where they will give a 5-minute presentation about their work on the ICFP main stage in front of a live audience. IMPORTANT DATES AND TIMES * Submission Deadline: 11 May 2026 (Monday) * Author Notification: 1 June 2026 (Monday) * ICFP 2026 Conference in Indiana, USA: 24 August 2026 (Monday) - 26 August 2026 (Wednesday) SUBMISSION OF EXTENDED ABSTRACTS * Submission Website: https://icfp26src.hotcrp.com Each submission (referred to as "abstract" below) should include the student author's name and email address; institutional affiliation; research advisor's name; ACM student member number; category (undergraduate or graduate); research title; and an extended abstract addressing the following: * Problem and Motivation: Clearly state the problem being addressed and explain the reasons for seeking a solution to this problem. * Background and Related Work: Describe the specialized (but pertinent) background necessary to appreciate the work in the context of ICFP areas of interest. Include references to the literature where appropriate, and briefly explain where your work departs from that done by others. * Approach and Uniqueness: Describe your approach in addressing the problem and clearly state how your approach is novel. * Results and Contributions: Clearly show how the results of your work contribute to programming language design and implementation in particular and to computer science in general; explain the significance of those results. * Submissions must be original research that is not already published at ICFP or another conference or journal. One of the goals of the SRC is to give students feedback on ongoing, unpublished work. Furthermore, the abstract must be authored solely by the student. If the work is collaborative with others and/or part of a larger group project, the abstract should make clear what the student's role was and should focus on that portion of the work. * Formatting: Submissions must be in PDF format, printable in black and white on US Letter sized paper, and interpretable by common PDF tools. All submissions must adhere to the "ACM Small" template that is available (in both LaTeX and Word formats) from https://www.acm.org/publications/authors/submissions. For authors using LaTeX, a lighter-weight package, including only the essential files, is available from http://sigplan.org/Resources/Author/#acmart-format. The submission must not exceed 3 pages in PDF format. Reference lists do not count towards the 3-page limit. Further information is available at the ICFP SRC website: https://icfp26.sigplan.org/track/icfp-2026-src

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