February 2023 - Haskell-Cafe

Best way to implement "scoped exceptions"?
by Tom Ellis 27 May '25

27 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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Takeover request: unix-compat
by Mitchell Rosen 07 Mar '23

07 Mar '23

Hi all, I'd like to take over maintenance responsibility for the `unix-compat` package. Unfortunately, I've been unable to get in touch with the maintainer. I intend to make a release compatible with `unix-2.8`, and will be around to make subsequent bounds bumps and whatnot. You can find me on GitHub: https://github.com/mitchellwrosen Or Hackage: https://hackage.haskell.org/user/mitchellwrosen Thanks, Mitchell

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Re: [Haskell-cafe] Status of ghcup?
by Anthony Clayden 03 Mar '23

03 Mar '23

> Sigh. As a college educator who is trying to use Haskell in as many classes as possible, ... > you better fire up Notepad.exe. ... some decent syntax highlighting, Hi Todd, and Mig, I too feel your pain. And Windows seems to have always been a neglected child in distros -- even when SPJ was actually sponsored by MSoft. If you're only trying to give a flavour of Haskell for (say) a few weeks intro, I don't see that you even need all the drama of ghcup. Perhaps just ignore what it says on the GHC download pages, and grab the compiler plus minimal libraries. Then you can either defer a 'proper' install until students are motivated enough to go through the pain; or don't bother/they've gone on to other subjects. I agree syntax highlighting is very helpful for newbies: I use NotePad++ for editing and not even VSCode for compiling, but GHCi. I suspect these fully integrated dev environments are quite confusing for newbies. (Unless they've already experienced them with other languages.) Hard for me to be sure: they simply weren't a thing when I learned Haskell. These days I have installed VSCode; I seldom use it (just way too much clutter around the screen). AntC

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[ANN] landlock 0.2.1.0
by Nicolas Trangez 27 Feb '23

27 Feb '23

I’m happy to announce the latest version of `landlock`, a Haskell library to access the Linux Landlock LSM API. This version updates the library to expose all Landlock features up to Linux 6.2 (Landlock ABI 3). It also introduces `landlocked`[1], a utility to spawn some process in a landlocked environment, and serves as a demo of how to use the API (next to the library documentation[2] and README.md[3]). It’s available on Hackage[4] and GitHub[5]. The Linux kernel Landlock API provides unprivileged access control. The goal of Landlock is to enable to restrict ambient rights (e.g. global filesystem access) for a set of processes. Because Landlock is a stackable LSM, it makes possible to create safe security sandboxes as new security layers in addition to the existing system-wide access- controls. This kind of sandbox is expected to help mitigate the security impact of bugs or unexpected/malicious behaviors in user space applications. Landlock empowers any process, including unprivileged ones, to securely restrict themselves. For more information, see the Landlock homepage[6] and its kernel documentation[7]. [1] https://github.com/NicolasT/landlock-hs/blob/27d2d95478f8c85cfbf4025bb41d57… [2] https://hackage.haskell.org/package/landlock-0.2.1.0/docs/System-Landlock.h… [3] https://github.com/NicolasT/landlock-hs/tree/main/landlock#readme [4] https://hackage.haskell.org/package/landlock-0.2.1.0 [5] https://github.com/NicolasT/landlock-hs [6] https://landlock.io/ [7] https://docs.kernel.org/userspace-api/landlock.html

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[Haskell] [ANNOUNCE] GHC 9.2.7 released
by Zubin Duggal 27 Feb '23

27 Feb '23

The GHC developers are happy to announce the availability of GHC 9.2.7. Binary distributions, source distributions, and documentation are available at [downloads.haskell.org](https://downloads.haskell.org/ghc/9.2.7). Download Page: https://www.haskell.org/ghc/download_ghc_9_2_7.html Blog Post: https://www.haskell.org/ghc/blog/20230227-ghc-9.2.7-released.html This release is primarily a bugfix release addressing a few issues found in 9.2.6. These include: * A fix for a bug with the RTS linker being unable to resolve the `setKeepCafs` symbol which started being used by the GHC library in 9.2.6, resulting in code depending on this symbol failing to load in GHCi or via a compile time splice when using a statically linked GHC, such as on Windows (#22961). * A fix a bug with the alignment of RTS data structures that could result in segfaults when compiled with high optimisation settings on certain platforms (#22975 , #22965). * A fix for a bug in the simplifier related to placeholder values (rubbish literals) emitted by the worker/wrapper optimisation leading to -dcore-lint errors and compiler panics in certain cases (#19882, #22914, #23000). * Easier installation of binary distribution on MacOS platforms by changing the installation Makefile to remove the quarantine attribute when installing. * ... and a few more. See the [release notes] for a full accounting. As some of the fixed issues do affect correctness users are encouraged to upgrade promptly. We would like to thank Microsoft Azure, GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, SimSpace, 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. Happy compiling, - Zubin [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.2.7/docs/html/users_guide/9.2.7-notes.…

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Munich Haskell Meeting, 2023-02-28 @ 19:30
by Leah Neukirchen 27 Feb '23

27 Feb '23

Dear all, Next week, our monthly Munich Haskell Meeting will take place again on Tuesday, February 28 at Cafe Puck at 19h30. For details see here: http://muenchen.haskell.bayern/dates.html If you plan to join, please add yourself to this nuudel so we can reserve enough seats! It is OK to add yourself to the dudle anonymously or pseudonymously. https://nuudel.digitalcourage.de/1HlsYFhVtoBdDSSM Everybody is welcome! cu, -- Leah Neukirchen <leah(a)vuxu.org> https://leahneukirchen.org/

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[ANN] NASA's Ogma 1.0.7
by Ivan Perez 25 Feb '23

25 Feb '23

Hi everyone! I'm really excited to announce the release of Ogma 1.0.7! Ogma is a NASA tool that facilitates integrating runtime monitors or runtime verification applications into other systems. Ogma extends Copilot [1], a high-level runtime verification framework that generates hard real-time code. In spite of the small increase in the version number, the feature included in this version is big: we now generate monitors for Robot Operating System (ROS 2) applications. Use cases supported by Ogma also include generating monitors directly from requirements specified using a structure natural language framework, and producing NASA Core Flight System (cFS) monitoring applications. For more details, including videos of monitors being generated and flown in simulators, see: https://github.com/nasa/ogma * Releases Ogma is released as a collection of packages in Hackage. The entry point is https://hackage.haskell.org/package/ogma-cli. * Code The github repo is located at: https://github.com/nasa/ogma. * What's coming The next release is planned for March 21st, 2023. Ogma is currently undergoing the qualification process necessary for NASA Class D Software. Apart from the changes required by that process, we also have the following in our roadmap: - Extend ROS 2 monitors with further information about sources of violations. - Add tests to generated code. - Simplify NASA cFS monitor generation process. Happy Haskelling! Ivan [1] https://github.com/Copilot-Language/copilot/

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KSF Media Ab hiring Senior Developer in Helsinki, Finland (repost)
by Kari Pahula 24 Feb '23

24 Feb '23

This was posted already once in November: https://mail.haskell.org/pipermail/haskell-cafe/2022-November/135687.html We got a second open position. KSF Media is Finland’s largest Swedish language news media group. Our products include Hufvudstadsbladet, Västra Nyland, Östnyland and HBL Junior. KSF Media’s digital products are growing fast and our focus is in digital subscription sales and product development. We are now looking for a new member to join our digital development team to create outstanding news media products for our readers. We are a small but capable team with a lean way of working and passion to learn new things every day. Our way of working • Kanban • Pair Programming, Code Reviews • Git, CI/CD (multiple deployments a day), Trunk Based Development • Working in the open. Our whole frontend is open source: https://github.com/KSF-Media/affresco and https://github.com/KSF-Media/mosaico Our stack • Most new developments happen in Haskell, PureScript and Javascript • Cloud Infrastructure as Code (Google Cloud, Kubernetes, Terraform) • Microservices environment with REST APIs What we expect from you is some relevant work experience and • English language. Swedish or Finnish knowledge is a plus • Knowledge of the principles behind the modern Web stack: things like MVC, Relational Databases and Testing • High motivation, self-steering, willingness to learn and dive into things, good social skills and good sense of humour • Interest in functional programming, news media and making the world a better place • Awareness of some UX principles, API design (and optionally UI design) and empathy for the users of your code • This job opportunity requires the successful candidate to relocate to Finland and offers a hybrid work arrangement, combining remote work and on-site presence. What we can offer • Competitive salary and benefits • The best co-workers • Office in the most central location in Helsinki • Flexible terms, with possibility to remote working Interested? Please apply via LinkedIn <https://www.linkedin.com/jobs/view/3498430755> or drop a line at antti.haarala(a)ksfmedia.fi no later than on the 10th of March.

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Status of ghcup?
by Dominick Samperi 23 Feb '23

23 Feb '23

I watched an interesting YouTube video explaining how to install and use the Haskell extension in VS code, but the information appears to be obsolete, because there is no mention of ghcup, and ghcup is now required, along with a new version of the Haskell extension (the old one is labeled "legacy"). Unfortunately, I could not install ghcup on Windows due to obscure PowerShell security issues, or missing libraries in MSYS. While wrestling with this problem I discovered that Unix tools from Rtools must not be in PATH while working with Stack, probably due to incompatible MSYS versions. But removing Rtools from PATH does not resolve the ghcup installation problems. Any tips on ghcup installation under Windows would be appreciated. Thanks, Dominick

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CfP - HLPP'2023 High-Level Parallel Programming and Applications
by VIRGINIA NICULESCU 23 Feb '23

23 Feb '23

[Apologies if you receive multiple copies of this CFP] CALL FOR PAPERS >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> HLPP 2023 16th International Symposium on International Symposium on High-Level Parallel Programming and Applications Cluj-Napoca, Romania June 29-30, 2023 https://www.cs.ubbcluj.ro/hlpp2023 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Important Dates * Abstract submission: April 3, 2023 * Paper submission: April 7, 2023 * Notification: May 15, 2023 * Draft proceedings version: June 9, 2023 * Conference: June 29-30, 2023 * Journal paper submission: September 2023 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Aims and Scope As processor and system manufacturers adjust their roadmaps towards increasing levels of both inter and intra-chip parallelism, so the urgency of reorienting the mainstream software industry towards these architectures grows. At present, popular parallel and distributed programming methodologies are dominated by low-level techniques such as send/receive message passing, or equivalently unstructured shared memory mechanisms. Higher-level, structured approaches offer many possible advantages and have a key role to play in the scalable exploitation of ubiquitous parallelism. HLPP symposia provide a forum for discussion and research about such high-level approaches to parallel and distributed programming. Topics HLPP 2023 invites papers on all topics in high-level parallel programming, its tools and applications including, but not limited to, the following aspects: * High-level parallel programming and performance models (e.g. BSP, CGM, LogP, MPM, etc.) and tools * Declarative parallel and distributed programming methodologies based on functional, logical, data-flow, actor, and other paradigms * Algorithmic skeletons, patterns, etc. and constructive methods * High-level parallelism in programming languages and libraries (e.g, OCaml, Haskell, Scala, C++, etc.): semantics and implementation * Verification of declarative parallel and distributed programs * Efficient code generation, auto-tuning, and optimization for parallel and distributed programs * Model-driven software engineering for parallel and distributed systems * Domain-specific languages: design, implementation, and applications * High-level programming models for heterogeneous/hierarchical platforms with accelerators, e.g., GPU, Many-core, DSP, VPU, FPGA, etc. * High-level parallel methods for large structured and semi-structured datasets * Applications of parallel and distributed systems using high-level languages and tools * Teaching experience with high-level tools and methods for parallel and distributed computing Past HLPP Symposia: https://hlpp.eu<https://hlpp.eu/> Submission Papers submitted to HLPP 2023 must describe original research results and must not have been published or simultaneously submitted anywhere else. As it is traditional for HLPP symposia, the accepted papers will be distributed at the symposium in draft proceedings, and then the papers will be published in the special issue of an international journal (the name of the journal is to be confirmed). In the past years, the journals were the International Journal of Parallel Programming and The Journal of Supercomputing. Each paper will receive a minimum of three reviews by members of the international technical program committee. Papers will be selected based on their originality, relevance, technical clarity, and quality of presentation. Manuscripts must be prepared with the Springer IJSS latex macro package using the single column option (\documentclass[smallextended]{svjour3}) and submitted via the EasyChair Conference Management System as one pdf file. The strict page limit for initial submission and camera-ready version is 20 pages in the aforementioned format. At least one author of each accepted paper must register for the HLPP 2023 symposium and present the paper. After the symposium the authors of the papers will have ample time to revise their papers and to incorporate both reviewer feedback and presentation feedback from the whole audience during the symposium. Organization * Virginia Niculescu, “Babeş-Bolyai” University of Cluj-Napoca, Romania * Adrian Sterca, “Babeş-Bolyai” University of Cluj-Napoca, Romania * Darius Bufnea, “Babeş-Bolyai” University of Cluj-Napoca, Romania Steering Committee * Gaétan Hains (Université Paris-Est Créteil, France) * Clemens Grelck (Universiteit van Amsterdam, Netherlands) * Kiminori Matsuzaki (Kochi University of Technology, Japan) * Christoph W. Kessler (Linköping University, Sweden) * Herbert Kuchen (University of Münster, Germany) * Marco Danelutto (University of Pisa, Italy) * Ines Dutra (University of Porto, Portugal) * Arturo Gonzalez-Escribano (Universidad de Valladolid, Spain) * Frédéric Dabrowski, Université d'Orléans, France) * Virginia Niculescu (“Babes-Bolyai” University, Romania) We are looking forward to your submissions and to seeing you in Cluj-Napoca, Romania in June 2022. Best regards, Virginia Niculescu ---------------------------------------------- Dr. Virginia Niculescu Faculty of Mathematics and Computer Science "Babes-Bolyai" University E-mail: virginia.niculescu(a)ubbcluj.ro, vniculescu(a)cs.ubbcluj.ro<mailto:vniculescu@cs.ubbcluj.ro> Web: http://www.cs.ubbcluj.ro/~vniculescu DISCLAIMER Prezentul mesaj ?i orice documente ata?ate pot con?ine informa?ii confiden?iale sau sensibile care apar?in Universită?ii Babe?-Bolyai din Cluj-Napoca. 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