August 2024 - Haskell-Cafe

Best way to implement "scoped exceptions"?
by Tom Ellis 28 May '25

28 May '25

I'd like to implement "scoped exceptions"[1], that is, a combinator of type withScopedException :: ((forall a. e -> IO a) -> IO r) -> IO (Either e r) so I can use exceptions in a convenient way, without having to set up fragile "action at a distance" based on the type of the thing I'm throwing and catching, for example: scopedExceptionExample :: IO (Either String (Either Int Void)) scopedExceptionExample = do withScopedException $ \throw1 -> withScopedException $ \throw2 -> if (1 :: Int) < 0 then throw1 "Hello" else throw2 1234 -- ghci> scopedExceptionExample -- Right (Left 1234) Here's a hacky way of doing it, based on tagging each exception with a unique value, and then filtering when handling: data MyException where MyException :: e -> Data.Unique.Unique -> MyException instance Show MyException where show _ = "<MyException>" instance Exception MyException withScopedException :: ((forall a. e -> IO a) -> IO r) -> IO (Either e r) wiathScopedException f = do fresh <- Data.Unique.newUnique flip tryJust (f (\e -> throwIO (MyException e fresh))) $ \case MyException e tag -> -- unsafeCoerce is very unpleasant if tag == fresh then Just (unsafeCoerce e) else Nothing This is the approach taken by the effectful library[2]. But is there a better way? Can I persuade GHC's RTS to work like this directly? Tom [1] I don't know if these already have a name [2] https://hackage.haskell.org/package/effectful-core-2.2.1.0/docs/src/Effectf…

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Journal of Functional Programming - Call for PhD Abstracts
by Graham Hutton 04 Nov '24

04 Nov '24

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 31st May 2024. Please share! Best wishes, Graham Hutton ============================================================ CALL FOR PHD ABSTRACTS Journal of Functional Programming Deadline: 31st May 2024 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 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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Speeding up trivial programs
by amindfv＠mailbox.org 25 Aug '24

25 Aug '24

I'm working on a small program that has to run many, many times, as quickly as possible (yes, it needs to be a standalone program). I've optimized it in many ways, but I seem to have a time floor, observable with "Hello, world" $ cat Hello.hs main = putStrLn "Hello world" $ ghc -O2 Hello.hs $ time ./Hello Hello world real 0m0.150s user 0m0.117s sys 0m0.032s The equivalent program in C takes only 0.002s (75x faster). What is taking the extra time? Is it the RTS "booting"? Is there any way to speed this up? Thanks, Tom

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[ANN] Dunai 0.13.1, dunai-test 0.13.1 and bearriver 0.14.10
by Ivan Perez 22 Aug '24

22 Aug '24

Dear all, I'm really excited to announce the release of Dunai 0.13.1 and Bearriver 0.14.10! Dunai is a reactive programming library structured around a notion of Monadic Stream Functions. Dunai can be used to implement other reactive and FRP frameworks on top, including Classic FRP and Arrowized FRP variants. Dunai comes with: - bearriver: API-compatible implementation of Yampa. (The Bear River is a tributary to the Yampa river.) - dunai-test: QuickCheck-based temporal testing library that can be connected with the testing system haskell-titan. See https://github.com/ivanperez-keera/dunai#features for details on Dunai's features. This release fixes an issue with the dependency on the list-transformer library as an alternative to transformers. Thanks to @ tomsmeding for the contribution. This release also provides a matching FRP.BearRiver.Integration, FRP.BearRiver.Random, FRP.BearRiver.Task and FRP.BearRiver.Simulation (akin to Yampa's), including the new Yampa combinator trapezoidIntegral. This last combinator was copied almost verbatim from Yampa, and I want to thank @idontgetoutmuch , @miguel-negrao and @thalerjonathan once again for the discussion and for contributing several alternative implementations. We are now just one module away from being able to provide 100% match in bearriver for all definitions in Yampa. Special thanks go to Johannes Riecken (@johannes-riecken on github) for a regular contribution to support the dunai and Yampa projects. As always, dunai, dunai-test and bearriver are released in sync. For details, see: - https://github.com/ivanperez-keera/dunai/releases/tag/v0.13.1 *Releases* You can explore the current versions at: - https://hackage.haskell.org/package/dunai - https://hackage.haskell.org/package/dunai-test - https://hackage.haskell.org/package/bearriver *Code* The github repo is located at: https://github.com/ivanperez-keera/dunai *What's coming* This release comes exactly 2 months after the last release. The next release is planned for Oct 21, 2024. There are several issues open that you can contribute to: https://github.com/ivanperez-keera/dunai/issues Following our roadmap, the pending changes remain as follows: - Match all definitions from FRP.Yampa.Switches. - Use new performance evaluation features of Yampa to improve performance of both Yampa and dunai. - Create new examples that demonstrate the features of dunai and bearriver. *Donations* Our project is now seeking donations to help continue developing dunai, create new open source libraries, new material, and give talks. No donation is too small. Any contribution will absolutely help. See https://github.com/sponsors/ivanperez-keera for details. If you can help, please come forward. All the best, Ivan

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IFL 2024, final call for participation/registration
by Mart Lubbers 16 Aug '24

16 Aug '24

======================================================================= IFL 2024 36rd Symposium on Implementation and Application of Functional Languages venue: Radboud University Nijmegen, The Netherlands August 26 - 28 2024 https://ifl24.cs.ru.nl ======================================================================= ### 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 2024 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. ### Industrial track and 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 Following IFL tradition, IFL 2024 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chairs to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. After the symposium, a formal review process will take place, conducted by the program committee. Reviewing is single blind. There will be at least 3 reviews per paper. The reviewers have 6 weeks to write their reviews. For the camera-ready version the authors can make minor revisions which are accepted without further reviewing. ### Important dates Submission deadline of draft papers August 6th, 2024 EXTENDED Notification of acceptance for presentation August 6th, 2024 Registration deadline August 19th, 2024 IFL symposium August 26-28, 2024 Submission of papers for proceedings December 1st, 2024 Notification of acceptance February 2nd, 2025 Camera-ready version March 2nd, 2025 ### 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 Register here: https://ifl24.cs.ru.nl/Registration 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: Mart Lubbers Radboud University, The Netherlands Local Chairs: Peter Achten Radboud University, The Netherlands Sven-Bodo Scholz, Radboud University, The Netherlands ### Program committee: Benoît Montagu, University of Lorraine, Inria, France Christos Dimoulas, Northwestern University, USA Edsko de Vries, Well-typed, The Netherlands Fritz Henglein, University of Copenhagen, Denmark Ian Mackie, University of Sussex, UK Jason Hemann, Seton Hall University, USA João Saraiva, Universidade do Minho, Portugal Jurriaan Hage, Heriot-Watt University, UK Kenichi Asai, Ochanomizu University, Japan Maja Kirkeby, Roskilde University, Denmark Marco Morazán, Seton Hall University, USA Neil Mitchell, Facebook, UK Ralf Laemmel, University of Koblenz Landau, Germany Rinus Plasmeijer, TOP Software/Radboud University, The Netherlands Stephen Chang, UMass Boston, USA Tim Steenvoorden, Open University, The Netherlands Tom Schrijvers, KU Leuven, Belgium Yusuf Moosa Motara, Rhodes University, South Africa ### Venue IFL 2024 will be held physically in Nijmegen, the Netherlands. See the website for more information. https://ifl24.cs.ru.nl ### 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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Vienna Haskell Meetup on Sep 26th
by Andreas Klebinger 15 Aug '24

15 Aug '24

** *Hello everyone! We are hosting a Haskell meetup in Vienna on the 26th of September! The location will be at TU Vienna Treitlstraße 3, Seminarraum DE0110. The room will open at 18:00.We plan to have 1-2 short talks starting at 19:00 (topics to be announced). Depending on interest there might also be a short Show & Tell session giving people the opportunity to show off or talk about something they work(ed) on for 5-10 Minutes each.There will be time to discuss the presentations with some snacks and non-alcoholic drinks being provided afterwards with an option to acquire beer for a reasonable price.The meetup is open ended but we might have to relocate to a nearby bar as a group if it goes very late..* *There is no entrance fee or mandatory registration, but to help with planning we ask you to let us know in advance if you plan to attend here https://forms.gle/Paiw6D4QJzTKzcmM6 <https://forms.gle/Paiw6D4QJzTKzcmM6>or per email at haskellvienna.meetup(a)gmail.com. We especially encourage you to reach out if you would like to participate in the show&tell or to give a full talk so that we can ensure there is enough time for you to present your topic.We hope to welcome everyone soon, your organizers:Andreas(Andreas PK), Benny, Chris, fendor, VeryMilkyJoe, Samuel*

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no-unused-imports for only one import
by PICCA Frederic-Emmanuel 10 Aug '24

10 Aug '24

Hello, I would like to set -Wno-unused-imports for only one import, is it possible and how to do it ? thanks for your advices. Frederic

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POPL 2025 Call for Tutorials
by Ningning Xie 08 Aug '24

08 Aug '24

POPL 2025 CALL FOR TUTORIALS https://popl25.sigplan.org/track/POPL-2025-tutorials#Call-For-Tutorials The 52nd ACM SIGPLAN-SIGACT Symposium on Principles of Programming Languages (POPL 2025) will be held in Denver, United States. POPL provides a forum for the discussion of fundamental principles and important innovations in the design, definition, analysis, transformation, implementation, and verification of programming languages, programming systems, and programming abstractions. Tutorials for POPL 2025 are solicited on any topic relevant to the POPL community. We particularly encourage submissions of introductory tutorials that make the research presented at POPL more accessible to the participants. Tutorials will be held on Jan 19–21, 2025. The expected length of a tutorial is 3 hours, including questions and discussion (Q&A). *Submission details* Deadline for submission: October 18th, 2024 Notification of acceptance: November 1st, 2024 A tutorial proposal should provide the following information: - Tutorial title - Presenter(s), affiliation(s), and contact information - 1-3 page description (for evaluation). This should include the objectives, topics to be covered, presentation approach, target audience, prerequisite knowledge, and if the tutorial was previously held, the location (i.e. which conference), date, and number of attendees if available. - 1-2 paragraph abstract suitable for tutorial publicity. - 1-paragraph biography suitable for tutorial publicity. Proposals must be submitted by email to Christoph Matheja (chmat(a)dtu.dk) and Robert Rand (rand(a)uchicago.edu) with the subject line "POPL 2025 Tutorial Proposal: [tutorial name]". The proposal should be attached as a PDF, docx, or txt file. *Further information* Any query regarding POPL 2025 tutorial proposals should be addressed to the co-located events chairs Christoph Matheja (chmat(a)dtu.dk) and Robert Rand ( rand(a)uchicago.edu) or to the general chair Steve Zdancewic ( stevez(a)seas.upenn.edu)

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Mathematics in Programming - a book with Haskell examples
by Xinyu LIU 06 Aug '24

06 Aug '24

Hello, My book 'Mathematics in Programming' in English was published on 7/11/2024. This book uses Haskell as the main tool for examples of mathematics ideas. Springer link: https://link.springer.com/book/10.1007/978-981-97-2432-1 Amazon link: https://www.amazon.com/Mathematics-Programming-Xinyu-Liu/dp/9819724317/ The book presents the mathematical view and tools of computer programming with broad and friendly context. It explains the basic concepts such as recursion, computation model, types, data, and etc. The book serves as an introductory and reference guide to the engineers, students, researchers, and professionals who are interested in functional programming, type system, and computer programming languages. The book covers seven topics. Firstly, it lays out the number system based on Peano Axioms and demonstrates the isomorphic computer data structures. Then, it introduces Lambda calculus as a computing model and recursion, an important programming structure, with the Y-combinator. It next presents the basic abstract algebra, including group and fields, and provides a friendly introduction to Galois theory. After that, it uses category theory as a tool to explain several concepts in computer programming, including the type system, polymorphism, null handler, and recursive data types, then followed by an application of program optimization. In the last two chapters, the author shows how to program with the concept of infinity through stream and lazy evaluation, and then explains the naïve set theory and transfinite numbers, from which the logic paradox arises. Finally, it introduces four historical views of mathematical foundation, as well as Gödel’s incompleteness theorems developed in 1930s, and how they define the boundaries of computer programming. Additionally, the book provides biographies, stories, and anecdotes of 25 mathematicians, along with over 130 exercises and their corresponding answers. Xinyu LIU https://github.com/liuxinyu95 <https://github.com/liuxinyu95/unplugged> *e*^(*π*i)+1 = 0

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IFL 2024 Final call for papers, extended submission deadline.
by Mart Lubbers 06 Aug '24

06 Aug '24

======================================================================= IFL 2024 36rd Symposium on Implementation and Application of Functional Languages venue: Radboud University Nijmegen, The Netherlands August 26 - 28 2024 https://ifl24.cs.ru.nl ======================================================================= ### 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 2024 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. ### Industrial track and 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 Following IFL tradition, IFL 2024 will use a post-symposium review process to produce the formal proceedings. Before the symposium authors submit draft papers. These draft papers will be screened by the program chairs to make sure that they are within the scope of IFL. The draft papers will be made available to all participants at the symposium. Each draft paper is presented by one of the authors at the symposium. After the symposium, a formal review process will take place, conducted by the program committee. Reviewing is single blind. There will be at least 3 reviews per paper. The reviewers have 6 weeks to write their reviews. For the camera-ready version the authors can make minor revisions which are accepted without further reviewing. ### Important dates Submission deadline of draft papers August 6th, 2024 EXTENDED Notification of acceptance for presentation August 6th, 2024 Registration deadline August 19th, 2024 IFL symposium August 26-28, 2024 Submission of papers for proceedings December 1st, 2024 Notification of acceptance February 2nd, 2025 Camera-ready version March 2nd, 2025 ### 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 Register here: https://ifl24.cs.ru.nl/Registration 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: Mart Lubbers Radboud University, The Netherlands Local Chairs: Peter Achten Radboud University, The Netherlands Sven-Bodo Scholz, Radboud University, The Netherlands ### Program committee: Benoît Montagu, University of Lorraine, Inria, France Christos Dimoulas, Northwestern University, USA Edsko de Vries, Well-typed, The Netherlands Fritz Henglein, University of Copenhagen, Denmark Ian Mackie, University of Sussex, UK Jason Hemann, Seton Hall University, USA João Saraiva, Universidade do Minho, Portugal Jurriaan Hage, Heriot-Watt University, UK Kenichi Asai, Ochanomizu University, Japan Maja Kirkeby, Roskilde University, Denmark Marco Morazán, Seton Hall University, USA Neil Mitchell, Facebook, UK Ralf Laemmel, University of Koblenz Landau, Germany Rinus Plasmeijer, TOP Software/Radboud University, The Netherlands Stephen Chang, UMass Boston, USA Tim Steenvoorden, Open University, The Netherlands Tom Schrijvers, KU Leuven, Belgium Yusuf Moosa Motara, Rhodes University, South Africa ### Venue IFL 2024 will be held physically in Nijmegen, the Netherlands. See the website for more information. https://ifl24.cs.ru.nl ### 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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