- Haskell-Cafe - Haskell.org

Conduit missing closing file handles
by Henning Thielemann 14 May '26

14 May '26

I have a pretty simple program for converting ZIP to TAR archives using the 'zip' and 'tar-conduit' packages, both using Conduit for streaming data. In principle the program works, but if the ZIP archive contains a non-trivial number of files, the program breaks because of exceeded limit of open file handles: $ zip2tar /usr/share/libreoffice/share/config/images_colibre.zip >/tmp/images_colibre.tar zip2tar: Uncaught exception ghc-internal:GHC.Internal.IO.Exception.IOException: /usr/share/libreoffice/share/config/images_colibre.zip: openFile: resource exhausted (Too many open files) While handling /usr/share/libreoffice/share/config/images_colibre.zip: openFile: resource exhausted (Too many open files) HasCallStack backtrace: throwIO, called at ./Control/Monad/Trans/Resource.hs:195:13 in resourcet-1.3.0-8b355f9483371034fb75ff40adb2e07157502721c941fbf8a6f607df6dd81546:Control.Monad.Trans.Resource The main function is essentially this one: [1] convertZipToTar :: (Zip.EntrySelector -> Zip.EntryDescription -> CTar.FileInfo) -> Sort -> FilePath -> IO () convertZipToTar fileInfoFromZipEntry_ sortMode zipPath = Zip.withArchive zipPath $ do entries <- Map.toList <$> Zip.getEntries files <- for entries $ \(selector, descr) -> flip fmap (Zip.getEntrySource selector) $ \src -> src .| (C.yield (Left $ fileInfoFromZipEntry_ selector descr) >> C.mapC Right) C.liftIO $ runConduitRes $ sequence_ files .| void CTar.tar .| C.stdoutC 'Zip.getEntrySource selector' generates a conduit for reading a file from the ZIP archive. It opens the archive anew for every accessed file, but it calls Conduit.Binary.sourceIOHandle, which promises to close a file promptly after reading. [2] It seems that files are not immediately closed after reading, but I cannot spot the cause. I suspected that "sequence_ files" might concatenate the Conduits while accumulating open file handles, but I think it should not and I did not find a matching alternative to sequence_. [1] https://hackage-content.haskell.org/package/zip2tar-0.0/src/src/Main.hs [2] https://hackage-content.haskell.org/package/zip-2.2.1/docs/src/Codec.Archiv…

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Subscription management
by Joachim Durchholz 14 May '26

14 May '26

Hi all, I accidentally subscribed two of my mail addresses to Haskell-cafe; here are the pertinent envelope address lines from the incoming mails: Envelope-to: joachim(a)durchholz.org Envelope-to: jo(a)durchholz.org I tried to unsubscribe (both, actually), but https://mailman.haskell.org/accounts/password/reset/ claims to have no knowledge of any of these two addresses. What should I do next? Regards, Jo P.S.: Something is wrong in the appended footer. The HTML version may be fine, but the text version I'm seeing obviously misses a link in the second-to-last line: > _______________________________________________ > Haskell-Cafe mailing list -- haskell-cafe(a)haskell.org > To (un)subscribe, modify options or view archives go to: > Only members subscribed via the mailman list are allowed to post. Sorry for going to the list itself, but I don't know the list administrator's mail address.

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Uploading packages from CLI
by Ivan Perez 08 May '26

08 May '26

Hi, Cabal is getting stuck when I try to upload a package from CLI. My user and password are correct. It this a known problem? Thanks, Ivan

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Journal of Functional Programming - Call for PhD Abstracts
by Graham Hutton (staff) 05 May '26

05 May '26

Dear all, If you or one of your students recently completed a PhD (or Habilitation) in the area of functional programming, please submit the dissertation abstract for publication in JFP: simple process, no refereeing, open access, 200+ published to date, deadline 30st May 2026. Please share! Best wishes, Graham Hutton ============================================================ CALL FOR PHD ABSTRACTS Journal of Functional Programming Deadline: 31st May 2026 http://tinyurl.com/jfp-phd-abstracts ============================================================ PREAMBLE: Many students complete PhDs in functional programming each year. As a service to the community, twice per year the Journal of Functional Programming publishes the abstracts from PhD dissertations completed during the previous year. The abstracts are made freely available on the JFP website, i.e. not behind any paywall. They do not require any transfer of copyright, merely a license from the author. A dissertation is eligible for inclusion if parts of it have or could have appeared in JFP, that is, if it is in the general area of functional programming. The abstracts are not reviewed. Please submit dissertation abstracts according to the instructions below. We welcome submissions from both the student and the advisor/supervisor although we encourage them to coordinate. Habilitation dissertations are also eligible for inclusion. ============================================================ SUBMISSION: Please submit the following information to Graham Hutton <graham.hutton(a)nottingham.ac.uk> by 31st May 2026 o Dissertation title: (including any subtitle) o Student: (full name) o Awarding institution: (full name and country) o Date of award: (month and year; depending on the institution, this may be the date of the viva, corrections being approved, graduation ceremony, or otherwise) o Advisor/supervisor: (full names) o Dissertation URL: (please provide a permanently accessible link to the dissertation if you have one, such as to an institutional repository or other public archive; links to personal web pages should be considered a last resort) o Dissertation abstract: (plain text, maximum 350 words; you may use \emph{...} for emphasis, but we prefer no other markup or formatting; if your original abstract exceeds the word limit, please submit an abridged version within the limit) Please do not submit a copy of the dissertation itself, as this is not required. JFP reserves the right to decline to publish abstracts that are not deemed appropriate. ============================================================ PHD ABSTRACT EDITOR: Graham Hutton School of Computer Science University of Nottingham Nottingham NG8 1BB United Kingdom ============================================================ This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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Questions about my findings about versioning, dependencies and breakages on Hackage
by Jon Kristensen 04 May '26

04 May '26

Hi! I’m currently wrapping up my master’s thesis, which is about dependencies and breakages on Hackage. In short, I’m analyzing all packages released onto Hackage during a certain window (currently the first quarter of 2025). I’m using the Hackage package index and the Hackage API to collect metadata. I’m using print-api[1] to attempt to detect breaking API changes between these releases and their predecessors. I’m using HIE DB[2] to identify which symbols are actually being used by reverse dependencies. My goal is to investigate versioning and dependency constraint practices, as well as package breakages. I’m now at a point where I would like to evaluate my findings with experts in the Haskell community (such as experienced developers and package maintainers). If you could spare a bit of time I would love to hear your thoughts on my work. I’m thinking the questions could be sent via email, but if you prefer a call we could do that as well. You will be anonymous when any data is presented. Thank you for whatever you can do! All the best, Jon [1]: https://github.com/Kleidukos/print-api [2]: https://github.com/haskell/HieDb

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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 06 Apr '26

06 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 03 Apr '26

03 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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