- Haskell-Cafe - Haskell.org

Non-linear patterns.
by Serguey Zefirov 06 May '25

06 May '25

There are artifacts of old Haskell standards that are a matching against integer value (2 + 2 = 5) and a matching against arithmetic expression (f (n+1) = f n). Both are interesting in requiring a class over type to match. f 10 = 11 has type f :: (Eq a1, Num a1, Num a2) => a1 -> a2 f (n+1) = f n has type f :: Integral t1 => t1 -> t2 In that vein it is possible to add non-linear patterns by adding an equality constraint on the non-linear matches. E.g., f x x = x would have type f :: Eq a => a -> a -> a For example: data Logic = True | False | Not Logic | Or Logic Logic | And Logic Logic deriving Eq simplify (And x x) = simplify x simplify (Or x x) = simplify x simplify (Not (Not x)) = simplify x simplify x = x Patterns like that are common in simplification/optimization rules. Also, by making them legal, it would be possible to use them in Template Haskell to make better embedded languages. On the implementation side, it can be implemented much like the (n+k) pattern. I also think that pattern matching completeness checker should not change. What would you say?

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Journal of Functional Programming - Call for PhD Abstracts
by Graham Hutton 06 May '25

06 May '25

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 30th May 2025. Please share! Best wishes, Graham Hutton ============================================================ CALL FOR PHD ABSTRACTS Journal of Functional Programming Deadline: 30th May 2025 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 29th November 2024. 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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GHC 9.10.2 is now available
by Zubin Duggal 03 May '25

03 May '25

The GHC developers are very pleased to announce the availability of the release candidate for GHC 9.10.2. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org][] and via [GHCup](https://www.haskell.org/ghcup/). GHC 9.10.2 is a bug-fix release fixing over 50 issues of a variety of severities and scopes, including: * Significantly improved performance when dynamically loading Haskell symbols (#23415). * Fixing a bug where the simplifier sometimes destroyed join points during float out, which could impact performance (#24768). * Reduced memory fragmentation in the non-moving GC's segment allocator, improving resident set size by up to 26% for some applications (#24150). * Added new flags to control speculative evaluation (-fspec-eval and -fspec-eval-dictfun) to work around performance regressions (#25606). * Fixed several platform-specific issues, including segfaults with FFI on PowerPC (#23034) and improved code generation for AArch64 with multiway branches now using jump tables (#19912) * 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][]. We would like to thank Well-Typed, Tweag I/O, Juspay, QBayLogic, Channable, Serokell, 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. As always, do give this release a try and open a [ticket][] if you see anything amiss. Cheers, Zubin [release notes]: https://downloads.haskell.org/~ghc/9.10.2/docs/users_guide/9.10.2-notes.html [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status [downloads.haskell.org] https://downloads.haskell.org/ghc/9.10.2 [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new

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Haskell Symposium 2025 Second Call for Papers
by Ningning Xie 02 May '25

02 May '25

======================================================================== Haskell Symposium 2025 Call for Papers Thu 16 - Fri 17 Oct 2025, Singapore https://conf.researchr.org/home/icfp-splash-2025/haskellsymp-2025 ======================================================================== The ACM SIGPLAN Haskell Symposium 2025 will be co-located with the 2025 International Conference on Functional Programming (ICFP) and the 2025 International Conference on Systems, Programming, Languages and Applications: Software for Humanity (SPLASH). The Haskell Symposium presents original research on Haskell, discusses practical experience and future development of the language, and promotes other forms of declarative programming. Submission deadline: 9 June 2025 (Mon) Notification: 17 July 2025 (Thu) Deadlines are valid anywhere on Earth. Papers should be submitted through HotCRP at: https://haskell25.hotcrp.com/ Topics of interest include: * Language design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, such as formal semantics of the present language or future extensions, type systems, effects, metatheory, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management, as well as foreign function and component interfaces; * Libraries, that demonstrate new ideas or techniques for functional programming in Haskell; * Tools, such as profilers, tracers, debuggers, preprocessors, and testing tools; * Applications, to scientific and symbolic computing, databases, multimedia, telecommunication, the web, and so forth; * Functional Pearls, being elegant and instructive programming examples; * Experience Reports, to document general practice and experience in education, industry, or other contexts; * Tutorials, to document how to use a particular language feature, programming technique, tool or library within the Haskell ecosystem; * System Demonstrations, based on running software rather than novel research results. Keynote Speakers ================= * Richard A. Eisenberg * Simon Peyton Jones Program Committee ================= Andreas Abel Gothenburg University Patrick Bahr IT University of Copenhagen Matthew Fluet Rochester Institute of Technology Adam Gundry Well-Typed LLP Xuejing Huang IRIF Hideya Iwasaki Meiji University Patricia Johann Appalachian State University Hsiang-Shang 'Josh' Ko Institute of Information Science, Academia Sinica András Kovács University of Gothenburg and Chalmers University of Technology Andres Löh Well-Typed LLP J. Garrett Morris (co-chair) University of Iowa Liam O'Connor Australian National University Maciej Piróg University of Wrocław Arnaud Spiwack Tweag Meng Wang University of Bristol Li-yao Xia Inria Ningning Xie (co-chair) University of Toronto Gergő Érdi Standard Chartered Bank

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Utrecht Summer School on Advanced Functional Programming
by Wouter Swierstra 02 May '25

02 May '25

Second Call for Participation SUMMER SCHOOL ON ADVANCED FUNCTIONAL PROGRAMMING Utrecht, the Netherlands, 07 July – 11 July 2025 http://afp.school **Please register before June 15th** ## ABOUT The Advanced Functional Programming summer school has been running for more than fifteen years. We aim to educate aspiring Haskell programmers beyond the basic material covered by many textbooks. The lectures will cover several more advanced topics regarding the theory and practice of Haskell programming, including topics such as: * lambda calculus; * lazy evaluation; * generalized algebraic data types; * type families and type-level programming; * concurrency and parallelism. The summer school will be held in Utrecht and consists of a mix of lectures, labs, and a busy social program. ## PREREQUISITES We expect students to have a basic familiarity with Haskell already. You should be able to write recursive functions over algebraic data types, such as lists and trees. There is a great deal of material readily available that covers this material. If you've already started learning Haskell and are looking to take your functional programming skills to the next level, this is the course for you. ## DATES Registration deadline: June 15th, 2025 School: 07 July – 11 July 2025 ## COSTS € 950 euro - Profession registration fee € 500 euro - Student registration fee € 200 euro - Housing fee We will charge a registration fee of €950 (or €500 for students) to cover our expenses. This fee includes all lunches, dinners, and coffee breaks - you won't need to budget much else besides your travel. If this is problematic for you for any reason at all, please email the organisers and we can try to offer you a discounted rate or a fee waiver. We have a limited number of scholarships or discounts available for students that would not be able to attend otherwise, especially for women and under-represented minorities. ## FURTHER INFORMATION Further information, including instructions on how to register, is available on our website: http://afp.school

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IFL 2025: First call for papers
by Mart Lubbers 29 Apr '25

29 Apr '25

===================================================================== IFL 2025 37th Symposium on Implementation and Application of Functional Languages Montevideo, Uruguay October 1-3, 2025 https://www.fing.edu.uy/inco/congresos/ifl2025 ===================================================================== ### Scope The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2025 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. ### Topics of interest Topics of interest to IFL include, but are not limited to: - language concepts - type systems, type checking, type inferencing - compilation techniques - staged compilation - run-time function specialisation - run-time code generation - partial evaluation - (abstract) interpretation - meta-programming - generic programming - automatic program generation - array processing - concurrent/parallel programming - concurrent/parallel program execution - embedded systems - web applications - (embedded) domain specific languages - security - novel memory management techniques - run-time profiling performance measurements - debugging and tracing - virtual/abstract machine architectures - validation, verification of functional programs - tools and programming techniques ### Peer-review process Differently from previous editions of IFL, IFL 2025 solicits two kinds of submissions: * Regular papers (12 pages including references) * Draft papers for presentations ('weak' limit between 8 and 15 pages) Regular papers will undergo a rigorous review by the program committee, and will be evaluated according to their correctness, novelty, originality, relevance, significance, and clarity. A set of regular papers will be conditionally accepted for publication. Authors of conditionally accepted papers will be provided with committee reviews along with a set of mandatory revisions. Regular papers not accepted for publication will be considered as draft papers, at the request of the author. Draft papers will be screened to make sure that they are within the scope of IFL, and will be accepted for presentation or rejected accordingly. Prior to the symposium: Authors of conditionally accepted papers and accepted presentations will submit a pre-proceedings version of their work that will appear in the draft proceedings distributed at the symposium. The draft proceedings does not constitute a formal publication. We require that at least one of the authors present the work at IFL 2025. After the symposium: Authors of conditionally accepted papers will submit a revised versions of their paper for the formal post-proceedings. The program committee will assess whether the mandatory revisions have been adequately addressed by the authors and thereby determines the final accept/reject status of the paper. Our interest is to ultimately accept all conditionally accepted papers. If you are an author of a conditionally accepted paper, please make sure that you address all the concerns of the reviewers. Authors of accepted presentations will be given the opportunity to incorporate the feedback from discussions at the symposium and will be invited to submit a revised full article for the formal post-proceedings. The program committee will evaluate these submissions according to their correctness, novelty, originality, relevance, significance, and clarity, and will thereby determine whether the paper is accepted or rejected. ### Important dates Submission of regular papers: June 16, 2025 Regular papers notification: August 4, 2025 Submission of draft papers: August 4, 2025 Draft papers notification: August 11, 2025 Deadline for early registration: September 5, 2025 Submission of pre-proceedings version: September 8, 2025 IFL Symposium: October 1-3, 2025 Submission of papers for post-proceedings: December 15, 2025 Notification of acceptance: February 28, 2026 Camera-ready version: March 30, 2026 Deadlines are end of day Anywhere on Earth (UTC-12) (https://www.timeanddate.com/time/zones/aoe) ### Submission details All contributions must be written in English. Papers must use the ACM two columns conference format, which can be found at: http://www.acm.org/publications/proceedings-template Submit your paper here: https://easychair.org/conferences/?conf=ifl20240 Important note to authors about the new ACM open access publishing model ACM has introduced a new open access publishing model for the International Conference Proceedings Series (ICPS). Authors based at institutions that are not yet part of the ACM Open program and do not qualify for a waiver will be required to pay an article processing charge (APC) to publish their ICPS article in the ACM Digital Library. To determine whether or not an APC will be applicable to your article, please follow the detailed guidance here: https://www.acm.org/publications/icps/author-guidance. Further information may be found on the ACM website, as follows: - Full details of the new ICPS publishing model: https://www.acm.org/publications/icps/faq - Full details of the ACM Open program: https://www.acm.org/publications/openaccess - Please direct all questions about the new model to icps-info(a)acm.org. ### Peter Landin Prize The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honoured article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. ### Organisation PC Chairs: Alberto Pardo, Universidad de la República, Montevideo, Uruguay Marcos Viera, Universidad de la República, Montevideo, Uruguay Local Chairs: Alberto Pardo, Universidad de la República, Montevideo, Uruguay Marcos Viera, Universidad de la República, Montevideo, Uruguay ### Program committee: Matteo Cimini, University of Massachusetts Lowell Facundo Domínguez, Tweag João Paulo Fernandes, Universidade do Porto Jeremy Gibbons, Oxford University Jurriaan Hage, Heriot Watt University Jason Hemann, Seton Hall University Maja Hanne Kirkeby, Roskilde University Mart Lubbers, Radboud University Bruno C. D. S. Oliveira, The University of Hong Kong Rinus Plasmeijer, Radboud University Andre Rauber Du Bois, Universidade Federal de Pelotas Rodrigo Ribeiro, Universidade Federal de Ouro Preto Alejandro Russo, Chalmers University of Technology João Saraiva, University of Minho Wenhao Tang, University of Edinburgh Zhixuan Yang, Imperial College London Brent Yorgey, Hendrix College Beta Ziliani, Manas.Tech Viktória Zsók, Eötvös Loránd University ### Venue IFL 2025 will be held physically in Montevideo, Uruguay. See the website for more information. https://www.fing.edu.uy/inco/congresos/ifl2025 ### Acknowledgments This call-for-papers is an adaptation and evolution of content from previous instances of IFL. We are grateful to prior organisers for their work, which is reused here.

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Is there a way to make this code compose generic ?
by PICCA Frederic-Emmanuel 25 Apr '25

25 Apr '25

Hello, I have this data DataSourceShape = DataSourceShape ([HSize], [Maybe HSize]) | DataSourceShape'Range !DIM1 !DIM1 a function which combine 2 DataSourceShape and produce an new one (monoid operation ?) combine'Shape ∷ DataSourceShape → DataSourceShape → DataSourceShape I use this in this class with familly types. class DataSource a where data DataSourcePath a ∷ Type data DataSourceAcq a ∷ Type ds'Shape ∷ MonadSafe m ⇒ DataSourceAcq a → m DataSourceShape withDataSourceP ∷ (Location l, MonadSafe m) ⇒ ScanFile l → DataSourcePath a → (DataSourceAcq a → m r) → m r and here an instance for one of my type DataFrameQCustom (I have plenty of them). they are all constructed the same way. data DataSourceAcq DataFrameQCustom = DataSourceAcq'DataFrameQCustom (DataSourceAcq Attenuation) (DataSourceAcq Geometry) (DataSourceAcq Image) (DataSourceAcq Mask) (DataSourceAcq Timestamp) (DataSourceAcq Timescan0) (DataSourceAcq Scannumber) ds'Shape(DataSourceAcq'DataFrameQCustom a g i m idx t0 s) = do sa ← ds'Shape a sg ← ds'Shape g si ← ds'Shape i sm ← ds'Shape m sidx ← ds'Shape idx st0 ← ds'Shape t0 ss ← ds'Shape s pure $ foldl1 combine'Shape [sa, sg, si, sm, sidx, st0, ss] withDataSourceP f (DataSourcePath'DataFrameQCustom a g i m idx t0 s) gg = withDataSourceP f a $ λa' → withDataSourceP f g $ λg' → withDataSourceP f i $ λi' → withDataSourceP f m $ λm' → withDataSourceP f idx $ λidx' → withDataSourceP f s $ λs' → withDataSourceP f t0 $ λt0' → gg (DataSourceAcq'DataFrameQCustom a' g' i' m' idx' t0' s') My question is, how should avoid writting by hand all these ds'Shape / withDatasourceP implementations, which seems quite mechanical. thanks for your help Frederic

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ICFP 2025 Student Research Competition Call for Submissions
by Kimball Germane 24 Apr '25

24 Apr '25

ICFP 2025 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 2025 * Finalists' presentations at ICFP 2025 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 2025. 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. Please note that a work cannot be simultaneously submitted to multiple SRCs, including both the ICFP SRC and the SPLASH SRC which are co-located this year. ### IMPORTANT DATES AND TIMES * Submission Deadline: 19 June 2025 (Thursday) * Author Notification: 14 July 2025 (Monday) * ICFP 2025 Conference in Singapore: 12 October 2025 (Sunday) - 18 October 2025 (Saturday) ### SUBMISSION OF EXTENDED ABSTRACTS * Submission Website: https://icfp25src.hotcrp.com Each submission (referred to as "abstract" below) should include the student author's name and e-mail 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://icfp25.sigplan.org/track/icfp-2025-student-research-competition

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"Magical Haskell" book is finally finished and available :)
by Anton Antich 22 Apr '25

22 Apr '25

Dear all, I have started working on this book almost 10 years ago, wrote about a third and then took a big pause until last year, when I got approached by Springer and finished the book in another 6 months, dedicating the 2nd part to Agentic AI and now it's finally out and available and I would really love to get the community's feedback :) I tried to introduce Haskell from the first mathematical principles, but very gently, so that it is accessible to a much wider audience as we all know the learning curve can be a bit steep. Here is a sample free chapter on medium: https://medium.com/superstringtheory/functor-bifunctor-trifunctor-c1424f962… The book itself is available on Springer: https://link.springer.com/book/10.1007/979-8-8688-1282-8 And there is a 20% discount with the code APAUT - or just scan the QR code below. I put a lot of effort into this book, being passionate about the language we all love and do hope it will help more people to become proficient and fluent in Haskell! Best wishes, Anton Antich, CPO and founder, Integrail.ai [image: image.png]

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Release: webdriver-precore
by John Walker 21 Apr '25

21 Apr '25

Hi All, We are happy to announce the release of [webdriver-precore]( https://hackage.haskell.org/package/webdriver-precore) ~ *A typed wrapper for [W3C WebDriver](https://www.w3.org/TR/2025/WD-webdriver2-20250306/) protocol* This library is intended to be used as a base for other libraries that provide a WebDriver client implementation and higher level functions for browser automation. More details can be found in the [project README]( https://github.com/pyrethrum/webdriver) John & Adrian

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