- Haskell-Cafe - Haskell.org

Re: State of Haskell 2025
by Olaf Klinke 12 Dec '25

12 Dec '25

> Because I haven't tried to upgrade: the risk of breaking something > exceeds any 'benefit' from new 'features', none of which do I want to > use. If you did not try to upgrade, how did you find out that upgrading would break your code? Indeed, only offering "yes" and "no" as options is not enough for this question. "Bottom" would be the appropriate answer in your case, and I'd have chosen that, too. Olaf

3 2

GHC 9.12.3-rc3 is now available
by Zubin Duggal 11 Dec '25

11 Dec '25

The GHC developers are very pleased to announce the availability of the third release candidate for GHC 9.12.3. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][] and via [GHCup](https://www.haskell.org/ghcup/). GHC 9.12.3 is a bug-fix release fixing several issues of a variety of severities and scopes. 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][]. This release candidate will have a two-week testing period. If all goes well the final release will be available the week of 22 December 2025. The changes from the first release candidate are - Fix use after free on windows due to a linker optimisation introduced in an earlier RC (#26613) - A fix for a bug in the configure script which result in the LLVM toolchain not being detected in certain situations (#26564) - Fixes for the WASM backend 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 that 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/9.12.3-… [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.12.3-rc3 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

1 0

State of Haskell 2025
by Jose Calderon 11 Dec '25

11 Dec '25

Hello everyone! The Haskell Foundation is reviving Taylor Fausak's State of Haskell Survey. It's been a few years and so we're doing it a bit differently, but the plan is to start doing this yearly again so that we can collect longitudinal data on the Haskell community and ecosystem. Please take the ~10 minutes to fill this out and share it with friends/colleagues/coworkers, whether or not they are users of Haskell. https://www.surveymonkey.com/r/6M3Z6NV Thanks! -Jose

4 4

ICFP 2026: Call for Workshops, Tutorials, and Co-Located Events
by ICFP Publicity 09 Dec '25

09 Dec '25

ICFP 2026: Call for Workshops, Tutorials, and Co-located Events The 31st ACM SIGPLAN International Conference on Functional Programming (ICFP) invites proposals for workshops, tutorials, and co-located events. ICFP will be held in Indianapolis, IN, United States from *Monday, August 24 to Saturday, August 29, 2026*. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementation, principles, and uses of functional programming. Proposals are invited for: - *Workshops* (and other co-located events, such as symposiums and side meetings) to be affiliated with ICFP 2026 and sponsored by SIGPLAN. We welcome proposals for events that facilitate discussions, presentations, hands-on activities, and other engaging formats to foster the exchange of new ideas and community building. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules may be possible. - *Tutorials* (or panels, discussions, etc.), lasting approximately 3 hours each, to be presented during ICFP and its co-located workshops and other events. Tutorials may focus either on a concrete technology or on a theoretical or mathematical tool. Tutorials may be intended primarily for researchers or for practitioners. Ideally, tutorials will have a concrete result, such as “Learn to do X with Y” rather than “Learn language Y”. The workshops, tutorials, etc. may occur on August 24th (the day before ICFP) and August 28-29th (the two days after ICFP). *Submission Portal*: https://icfp26events.hotcrp.com/ *All co-located events* must submit a proposal — workshops, tutorials, symposiums, or side meetings. Submission Details <https://icfp26.sigplan.org/track/icfp-2026-icfp-tutorials#submission-details> - Deadline for Workshop Proposal Submission: January 15, 2026 - Notification of Acceptance: January 29, 2026 - Deadline for Tutorial Proposal Submission: June 21, 2026 - Notification of Acceptance: June 28, 2026 Prospective organizers of workshops, symposia, or co-located events with PCs should submit proposals before the Workshop deadline. Proposals should outline the objectives, intended audience, and planned activities. Workshops that plan to have proceedings in the ACM DL will need SIGPLAN approval of their proposed PC list. The workshop chairs will solicit approval and send any feedback to workshop organizers. Workshops without proceedings still need conference approval from ICFP. See the Submission Portal for details. The selection committee will review proposals. Successful workshops may be asked to prepare a summary report suitable for publication in SIGPLAN Notices. Prospective organizers of tutorials, panels, or discussions should submit proposals by the Tutorial deadline. Proposals should outline the objectives, intended audience, and planned activities. See the Submission Portal for details. Selection Committee <https://icfp26.sigplan.org/track/icfp-2026-icfp-tutorials#selection-committ…> Event proposals will be evaluated by a committee comprising members from the ICFP 2026 organizing committee, in collaboration with the SIGPLAN executive committee. Sponsorship and Reimbursement <https://icfp26.sigplan.org/track/icfp-2026-icfp-tutorials#sponsorship-and-r…> ACM-sponsored workshops are permitted to have additional sponsors (i.e., getting donations specifically for the workshop, not for the main conference). Funds go to the ACM. Workshop organizers can request reimbursement using this form: https://app.hubspot.com/documents/5374542/view/900008676?accessId=a07c28 Further information about SIGPLAN sponsorship is available at: http://www.sigplan.org/Resources/Proposals/Sponsored/ Contact Information <https://icfp26.sigplan.org/track/icfp-2026-icfp-tutorials#contact-informati…> For inquiries, please contact the workshop co-chairs: Ben Greenman: blg(a)cs.utah.edu Jiasi Shen: sjs(a)cse.ust.hk We look forward to your proposals and to creating a vibrant and engaging workshop program at ICFP 2026!

1 0

CGO 2026 - Call for Participation
by Luisa Cicolini 09 Dec '25

09 Dec '25

CGO 2026<https://2026.cgo.org/> registration is now open! The IEEE/ACM International Symposium on Code Generation and Optimization (CGO) provides a premier venue to bring together researchers and practitioners working at the interface of hardware and software on a wide range of optimization and code generation techniques and related issues. The conference spans the spectrum from purely static to fully dynamic approaches, and from pure software-based methods to specific architectural features and support for code generation and optimization. CGO will be held in Sydney, Australia from 31st January – 4th February 2026 and will be co-located as part of HPCA/CGO/PPoPP/CC 2026. The early-bird registration deadline<https://2026.cgo.org/attending/registration> is December 31st. For more information, please visit the CGO conference website at https://2026.cgo.org/. We hope to see you there! Luisa Cicolini

1 0

POPL 2026 Second Call for Participation - Early registration: 12 December
by Ningning Xie 08 Dec '25

08 Dec '25

======================================= Call for Participation ACM SIGPLAN Symposium on Principles of Programming Languages (POPL 2026) January 11-17, 2026, Rennes, France. https://popl26.sigplan.org/ ======================================= - Early registration deadline: ** 12 December 2025 ** - Register here: https://popl26.sigplan.org/attending/registration - The POPL program: https://popl26.sigplan.org/track/POPL-2026-popl-research-papers ======================================= The 53rd ACM SIGPLAN Symposium on Principles of Programming Languages (POPL 2026) is a forum for the discussion of all aspects of programming languages and programming systems. Location: le Couvent des Jacobins, 20 place Saint-Anne, 35000 Rennes, France Dates: - Main conference: Wed 14 - Fri 16 January - Workshops, tutorials, co-located events: Sun 11, Mon 12, Tue 13 and Sat 17 January Keynote Speakers: - Damien Pous, CNRS, Medium-scale automation for proof assistants - Caroline Trippel, Stanford University, Hardware-Software Contracts for High Assurance with Applications to Side-Channel Security Organizers: - General Chair: Sandrine Blazy, University of Rennes - PC Chair: Suresh Jagannathan, Purdue University Full details of the conference and co-located events: https://popl26.sigplan.org/

1 0

PhD studentships in Nottingham
by Graham Hutton (staff) 05 Dec '25

05 Dec '25

Dear all, The School of Computer Science at the University of Nottingham in the UK is seeking applications for a number of fully-funded PhD studentships: https://tinyurl.com/uon-phds-2026 Applicants in the area of the Functional Programming Lab (tinyurl.com/fp-notts) are strongly encouraged! If you are interested in applying, please contact a potential supervisor as soon as possible; the application deadline is 7th January 2026: Thorsten Altenkirch - constructive logic, proof assistants, homotopy type theory, category theory, lambda calculus. Ulrik Buchholtz - homotopy type theory, synthetic homotopy theory, proof assistants, constructive mathematics, and related topics. Graham Hutton - functional programming, haskell, category theory, program verification, program calculation. Nicolai Kraus - not seeking a student through this scheme, but has separate funding available for a home/international student. Dan Marsden - category theory, logic, finite model theory, diagrammatic reasoning, foundations of computer science. Best wishes, The FP Lab University of Nottingham +-----------------------------------------------------------+ Fully-Funded PhD Studentships School of Computer Science University of Nottingham, UK https://tinyurl.com/uon-phds-2026 Applications are invited for fully-funded PhD studentships in the School of Computer Science, starting on 1st October 2026. The topics for the studentships are open, but your research proposal should relate to the interests of one of the School's research groups: Cyber-Physical Health and Assistive Robotics; Computational Optimisation and Learning; Computer Vision; Cyber Security; Functional Programming; Intelligent Modelling and Analysis; Mixed Reality; Uncertainty in Data and Decision Making; Visualisation and Computer Graphics; Responsible Digital Futures. The studentships available are fully funded for 3.5 years and include a stipend of £20,780 per year and tuition fees for home students. They are open to students of any nationality, but non-home students must be able to cover the additional cost of international tuition fees. Applicants are expected to have a first-class Bachelor or Masters degree or international equivalent, in a related discipline. If you are interested in applying, please contact a potential supervisor as soon as possible, and at least two weeks prior to the closing date. If the supervisor wishes to support your application, they will direct you to make an official application through the MyNottingham system. Closing date for applications: Wednesday 7th January 2026 +-----------------------------------------------------------+ 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.

2 1

How to use locally compiled GHC?
by Stefan Klinger 02 Dec '25

02 Dec '25

Hello, what do I have to do to use a locally compiled GHC on my own projects? Background: I'm working on this [1]. I've managed to compile GHC following the instructions given on https://ghc.dev, also here [2]. I can run $ ./_build/stage1/bin/ghc --interactive GHCi, version 9.15.20251202: https://www.haskell.org/ghc/ :? for help with the expected result. However, the locally built compiler (master branch, without any modifications) fails with all but the most primitive of my own projects. I try to do this by adding a line with-compiler: /home/sk/prg/ghc/master/_build/stage1/bin/ghc to the `cabal.project` file of a project. Then, success depends on the dependencies of a project. Here is one using `criterion`: $ cabal build Warning: Unknown/unsupported 'ghc' version detected (Cabal 3.12.1.0 supports 'ghc' version < 9.12): /home/sk/prg/ghc/third/_build/stage1/bin/ghc is version 9.15.20251202 Resolving dependencies... Error: [Cabal-7107] Could not resolve dependencies: [__0] next goal: foo (user goal) [__0] rejecting: foo-1.0 (constraint from user target requires ==0.0.1) [__0] trying: foo-0.0.1 [__1] trying: criterion-1.6.4.1 (dependency of foo) [__2] trying: vector-algorithms-0.9.1.0 (dependency of criterion) [__3] trying: primitive-0.9.1.0 (dependency of vector-algorithms) [__4] next goal: base (dependency of foo) [__4] rejecting: base-4.22.0.0/installed-inplace (conflict: primitive => base>=4.10 && <4.22) [__4] rejecting: base; 4.21.0.0, 4.20.2.0, 4.20.1.0, 4.20.0.1, 4.20.0.0, 4.19.2.0, 4.19.1.0, 4.19.0.0, 4.18.3.0, 4.18.2.1, 4.18.2.0, 4.18.1.0, 4.18.0.0, 4.17.2.1, 4.17.2.0, 4.17.1.0, 4.17.0.0, 4.16.4.0, 4.16.3.0, 4.16.2.0, 4.16.1.0, 4.16.0.0, 4.15.1.0, 4.15.0.0, 4.14.3.0, 4.14.2.0, 4.14.1.0, 4.14.0.0, 4.13.0.0, 4.12.0.0, 4.11.1.0, 4.11.0.0, 4.10.1.0, 4.10.0.0, 4.9.1.0, 4.9.0.0, 4.8.2.0, 4.8.1.0, 4.8.0.0, 4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (constraint from non-reinstallable package requires installed instance) [__4] fail (backjumping, conflict set: base, foo, primitive) After searching the rest of the dependency tree exhaustively, these were the goals I've had most trouble fulfilling: base, primitive, vector-algorithms, criterion, uvector, foo Try running with --minimize-conflict-set to improve the error message. And similar problems occur when depending on `unliftio` or `attoparsec`. How should I approach this? And I expect to run into similar questions in the near future, i.e., related to bulding, testing, using, but not necessarily related to [1]. Where should I ask? Kind regards Stefan [1]: https://github.com/haskell/core-libraries-committee/issues/367 [2]: https://gitlab.haskell.org/ghc/ghc/-/wikis/contributing -- Stefan Klinger, Ph.D. -- computer scientist o/X http://stefan-klinger.de /\/ https://github.com/s5k6 \ I prefer receiving plain text messages, not exceeding 32kB.

2 2

GHC 9.14.1-rc3 is now available
by Zubin Duggal 02 Dec '25

02 Dec '25

The previous email had an incorrect subject line, GHC 9.14.1-rc3 is what it was intended to say. The contents following this are the same. The GHC developers are very pleased to announce the availability of the third release candidate of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. The changes from the second release candidate are: - Fix RTS segfaults in certain situations (#26495) - Fix use after free on windows due to a linker optimisation introduced in an earlier RC (#26613) GHC 9.14 will bring 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 * SSE/AVX2 support in the x86 native code generator backend * A major update of the Windows toolchain and improved compatibility with macOS Tahoe * ... and many more A full accounting of changes can be found in the [release notes][]. Given the many specialisation improvements and their potential for regression, we would very much appreciate testing and performance characterisation on downstream workloads. Note that while this release makes many improvements in the specialisation optimisation, polymorphic specialisation will remain disabled by default in the final 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 that 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. [downloads.haskell.org] https://downloads.haskell.org/ghc/9.14.1-rc3 [release notes]: https://downloads.haskell.org/ghc/9.14.1-rc3/docs/users_guide/9.14.1-notes.… [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…

1 0

GHC 9.12.3-rc3 is now available
by Zubin Duggal 02 Dec '25

02 Dec '25

The GHC developers are very pleased to announce the availability of the third release candidate of GHC 9.14.1. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][]. The changes from the second release candidate are: - Fix RTS segfaults in certain situations (#26495) - Fix use after free on windows due to a linker optimisation introduced in an earlier RC (#26613) GHC 9.14 will bring 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 * SSE/AVX2 support in the x86 native code generator backend * A major update of the Windows toolchain and improved compatibility with macOS Tahoe * ... and many more A full accounting of changes can be found in the [release notes][]. Given the many specialisation improvements and their potential for regression, we would very much appreciate testing and performance characterisation on downstream workloads. Note that while this release makes many improvements in the specialisation optimisation, polymorphic specialisation will remain disabled by default in the final 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 that 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. [downloads.haskell.org] https://downloads.haskell.org/ghc/9.14.1-rc3 [release notes]: https://downloads.haskell.org/ghc/9.14.1-rc3/docs/users_guide/9.14.1-notes.… [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…

1 0