May 2022 - Haskell-Cafe

GHC 9.4.1-alpha2 now available
by Ben Gamari 24 May '22

24 May '22

The GHC developers are happy to announce the availability of the second alpha release of the GHC 9.4 series. Binary distributions, source distributions, and documentation are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.4.1-alpha2 This major release will include: - A new profiling mode, `-fprof-late`, which adds automatic cost-center annotations to all top-level functions *after* Core optimisation has run. This incurs significantly less performance cost while still providing informative profiles. - A variety of plugin improvements including the introduction of a new plugin type, *defaulting plugins*, and the ability for typechecking plugins to rewrite type-families. - An improved constructed product result analysis, allowing unboxing of nested structures, and a new boxity analysis, leading to less reboxing. - Introduction of a tag-check elision optimisation, bringing significant performance improvements in strict programs. - Generalisation of a variety of primitive types to be levity polymorphic. Consequently, the `ArrayArray#` type can at long last be retired, replaced by standard `Array#`. - Introduction of the `\cases` syntax from [GHC proposal 0302] - A complete overhaul of GHC's Windows support. This includes a migration to a fully Clang-based C toolchain, a deep refactoring of the linker, and many fixes in WinIO. - Support for multiple home packages, significantly improving support in IDEs and other tools for multi-package projects. - A refactoring of GHC's error message infrastructure, allowing GHC to provide diagnostic information to downstream consumers as structured data, greatly easing IDE support. - Significant compile-time improvements to runtime and memory consumption. - On overhaul of our packaging infrastructure, allowing full traceability of release artifacts and more reliable binary distributions. - ... and much more. See the [release notes] for a full accounting. Note that, as 9.4.1 is the first release for which the released artifacts will all be generated by Hadrian, it's possible that there will be packaging issues. If you enounter trouble while using a binary distribution, please open a [ticket]. Likewise, if you are a downstream packager, do consider migrating to [Hadrian] to run your build; the Hadrian build system can be built using `cabal-install`, `stack`, or the in-tree [bootstrap script]. We would like to thank Microsoft Azure, GitHub, IOHK, the Zw3rk stake pool, Tweag I/O, Serokell, Equinix, SimSpace, 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. Happy testing, - Ben [GHC proposal 0302]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0302-c… [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [bootstrap script]: https://gitlab.haskell.org/ghc/ghc/-/blob/e2520df3fffa0cf22fb19c5fb872832d1… [release notes]: https://downloads.haskell.org/~ghc/9.4.1-alpha2/docs/users_guide/9.4.1-note…

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ANN: haskell-links.org - searchable links db
by Simon Michael 21 May '22

21 May '22

Hello Haskell friends, Recently I said this on reddit: > There's no way these very frequent reddit and chat requests for learning materials can capture all the existing resources. There are too many, and folks who know where they are get burned out reposting them. There have been many attempts to gather them, haskell.org/documentation being the most obvious, but none of them have fully succeeded. We could really do with some more systematic, scalable (crowd-sourced, lightweight) approach. Then I experimented and set up https://haskell-links.org . This is version 1, providing: - A searchable read-only view of the Haskell links collected by lambdabot, the popular #haskell IRC bot. - A redirector/link shortener/memory aid, for jumping to any of these links via their short ID. Eg: https://haskell-links.org/doc <https://haskell-links.org/doc> https://haskell-links.org/books <https://haskell-links.org/books> https://haskell-links.org/ghc-guide <https://haskell-links.org/ghc-guide> - Collected links to other Haskell search tools, making this a fast way to get to anywhere in Haskelldom. After contemplation and discussion on #haskell, I believe version 2 should allow web editing and use its own database. But I wanted to share this one as it's a nice simple setup. I hope you might find useful ! Help is welcome, see README. Best, -Simon

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[ANN]: simfin 1.0.0 - Simple financial data API wrapper
by Owen Shepherd 21 May '22

21 May '22

Hello everyone, I've released a small library that wraps the SimFin (https://simfin.com/) API. SimFin collates and organises financial data, and provides a nice little web API which provides historical prices, ratios, financial statement extracts, etc. Hackage link: https://hackage.haskell.org/package/simfin-1.0.0 Enjoy, - Owen

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[template haskell] Sharing names between constructors and types
by Patrick L Redmond 20 May '22

20 May '22

Hello Haskell Cafe, When can a type not share the name of a constructor? Defining a type and a constructor with the same name, manually, as follows, seems to be acceptable: data F = F | T data T However, if the type is generated by Template Haskell, it is no longer acceptable, as follows: voidType :: Name -> DecsQ voidType n = do d <- dataD (return []) n [] Nothing [] [] return [d] In a separate module: data F = F | T $(voidType 'T) This will result in a "Multiple declarations of ‘T’" error. Is this expected? Thank you, Patrick

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Package takeover request for rapid
by Markus Läll 19 May '22

19 May '22

Hi I would like to take over https://hackage.haskell.org/package/rapid The author of the package Ertugrul Söylemez, once an active member of the community perhaps best known for netwire, passed away in 2018. [1] The work required for the package thus far, and for which I've kept a fork for, is to bump version bounds as GHCs progress. [1] https://github.com/esoeylemez/rapid/pull/2#issuecomment-427065739 -- Markus Läll

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ML Family Workshop 2022: Final Call for Presentations
by Benoit Montagu 17 May '22

17 May '22

We are happy to invite submissions to the ML Family Workshop 2022, to be held during the ICFP conference week on Thursday, September 15th. The ML family workshop warmly welcomes submission touching on the programming languages traditionally seen as part of the “ML family” (Standard ML, OCaml, F#, CakeML, SML#, Manticore, MetaOCaml, etc.). The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of the members of the ML family. We also encourage presentations from related languages (such as Haskell, Scala, Rust, Nemerle, Links, Koka, F*, Eff, ATS, etc), to exchange experience of further developing ML ideas. The workshop does not have proceedings, making it the perfect venue to run some ideas with the community or present some work in progress within a friendly environment. The PC has a broad expertise and submissions are 3 pages long: when in doubt, just submit! Currently, the workshop is scheduled to be an in-person event. We will give to the authors of accepted abstracts the opportunity to give their talks remotely if necessary, in case they could not travel. See the detailed CFP online on the ICFP website: https://icfp22.sigplan.org/home/mlfamilyworkshop-2022#Call-for-Presentations Important dates --------------- Friday 3th June (any time zone): Abstract submission deadline Tuesday 28th June: Author notification Thursday 15th August: ML Family Workshop Program committee ----------------- Kenichi Asai (Ochanomizu University) Arthur Azevedo de Amorim (Boston University) Dariusz Biernacki (University of Wrocław) Stephen Dolan (Jane Street) Kavon Farvardin (Apple) Armaël Guéneau (Inria) Sam Lindley (University of Edinburgh) Guido Martínez (CIFASIS-CONICET) Keiko Nakata (SAP Innovation Center Potsdam) Lionel Parreaux (Hong Kong University of Science and Technology) Matija Pretnar (University of Ljubljana) Mike Rainey (Carnegie Mellon University) Yann Régis-Gianas (Nomadic Labs) KC Sivaramakrishnan (IIT Madras and Tarides) Ningning Xie (University of Cambridge) Chair: Benoît Montagu (Inria) Submission details ------------------ See the online CFP for the details on the expected submission format. Submissions must be uploaded to the workshop submission website https://ml2022.hotcrp.com/ before the submission deadline.

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Assistant Professorships in Nottingham
by Graham Hutton 17 May '22

17 May '22

Dear all, As part of a strategic expansion, the School of Computer Science at the University of Nottingham is seeking to make multiple new appointments at the Assistant Professor level: https://tinyurl.com/38f753d5 These positions are aimed at early career academics who recently completed or will soon complete their PhD, and have a reduced teaching responsibility for the first three years. Applications in the area of the Functional Programming (FP) lab are strongly encouraged! The FP lab is keen to receive applications from candidates with a strong publication record (e.g. papers in leading venues such as LICS, POPL, ICFP, JFP, TOPLAS, etc) and the potential to secure external funding. The group recently grew its profile in type theory with the appointment of Nicolai Kraus and Ulrik Buchholtz. To complement these appointments, we particularly welcome applications from candidates who would bring further or other areas of expertise. Further information about the FP lab is available from: https://tinyurl.com/y2ekdkqa The deadline for applications is Tuesday 24th May 2022. -- Graham Hutton and Thorsten Altenkirch 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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Haskellers needed @ Superrare Labs
by Ruben Astudillo 13 May '22

13 May '22

Hello haskell-cafe . I have been working with SuperRare Labs for more than a year and they are looking to grow the team! I know the feelings of the community about NFTs and Blockchains. Those arguments have been said (and said better!) for example on the haskell sub-reddit. Still, I think there are neat pieces of technology on our backend and we have a good work environment where we can do some neat engineering. SuperRare labs is a US based company with US level compensation, fully remote (I am Chilean and I feel in-the-loop). Technology wise we are into Haskell, GraphQL (template haskell interop), `extensible`-records, Postgresql and hs-web3[0]. If any of those technologies interest you, _please_ send a message at the forms at greenhouse[1], in particular on the backend engineer role. Also, send me a private email so we can chat, answer your questions and/or see ways to speed up the process. [0]: <https://hackage.haskell.org/package/web3> [1]: <https://boards.greenhouse.io/superrarelabs> -- Rubén. (pgp: 1E88 3AC4 89EB FA22)

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Final call for participation: Advanced Functional Programming Summer School in Utrecht
by Swierstra, W.S. (Wouter) 13 May '22

13 May '22

# Call for Participation SUMMER SCHOOL ON ADVANCED FUNCTIONAL PROGRAMMING Utrecht, the Netherlands, 04 July – 08 July 2022 http://www.afp.school **Please register before June 17th ** ## ABOUT The Advanced Functional Programming summer school has been running for more than ten years. We aim to educate aspiring Haskell programmers beyond the basic material covered by many textbooks. After running remotely for the past two years, we're thrilled to announce that this year's edition will take place on site in Utrecht. We are monitoring the pandemic closely - and will make contingency plans if we cannot meet in person; at the moment, we do not have plans for remote participation. The lectures will cover several more advanced topics regarding the theory and practice of Haskell programming, including topics such as: * lambda calculus; * monads and monad transformers; * lazy evaluation; * generalized algebraic data types; * type families and type-level programming; * concurrency and parallelism. The summer school consists of a mix of lectures, labs, and a busy social program. ## LECTURERS Utrecht staff: * Gabriele Keller * Trevor McDonell * Wouter Swierstra ## 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 17th, 2022** School: 04 July – 08 July 2022 ## COSTS 750 euro - Profession registration only 250 euro - Student registration fee 200 euro - Housing fee We will charge a registration fee of 750 euros (or 250 euros for students) to cover our expenses. 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://www.afp.school

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profiling cpu usage of concurrent program
by Olaf Klinke 12 May '22

12 May '22

Dear Café, I have a network application of which I would like to know which parts are responsible for the majority of CPU usage. Conventional GHC profiling does not quite work here, because 1. +RTS -p shows that the program spends most of its *time* idling, where cost centers of interest are so insignificant that the precision of %time in the .prof format make it impossible to determine the relative execution time of selected cost centers. The Wiki [1] suggests the -P option. 2. Even ThreadScope (haven't tried yet) may show me only what's expected: The work is done in worker threads. I am not so much concerned about the level of concurrency or parallelism, but which parts occupy the cpu. I ran the program with +RTS -P and sorted the output by ticks. Naturally, functions like threadDelay and liftIO come at the top. But these all stand for waiting IO actions. As first approximation, I might ignore these and consider the remainder. Is that a valid approach? Is there a profiler that measures something like CPU cycles per cost center? Should I turn to ghc-events-analyze [2]? Or perf? Execution time is not critical (as long as the queue is emptied faster than data is flowing in) but maxing out the computing resources may become critical because it mandates more expensive hardware. I've been pitching Haskell to my bosses by promising better performance (compared to Python). Appropriate profiling seems essential to keep that promise. Olaf [1] https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/profiling.h… [2] https://hackage.haskell.org/package/ghc-events-analyze

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