October 2023 - Haskell-Cafe

Request for take over: graphviz
by Daniel Casanueva 18 Oct '23

18 Oct '23

Hello, graphviz [1] maintenance has been inactive for a long time now. Revisions have been published, but the maintainer seems unresponsive. Last year, Bodigrim suggested the package needs a new maintainer in a GitHub thread [2] that one month ago I found while looking if someone had already done the fix I needed. I'm happy to help keeping the package alive so, about a month ago, I emailed Ivan (graphviz's author) to the e-mail address from his GitHub profile, offering my assistance with graphviz. I haven't gotten any answer yet, so I thought I should be making my offer public, as indicated by the "Taking over a package" wikipage [3]. I don't have big change plans for graphviz. Most likely I will just be patching it to keep it working with future GHC releases and reviewing/accepting PRs. Thank you, Daniel [1] https://hackage.haskell.org/package/graphviz [2] https://github.com/ivan-m/graphviz/pull/53#issuecomment-1261496914 [3] https://wiki.haskell.org/Taking_over_a_package

1 0

Assistant Prof at Barnard College, Columbia U
by Mark Santolucito 17 Oct '23

17 Oct '23

Hi all, Barnard College, Columbia University has an opening for an Assistant Professor: https://cs.barnard.edu/assistant-professor-computer-science-2024 The deadline is Oct 27 for full consideration. Barnard is the women's college of Columbia and has a 2-2 teaching load (typically with additional reductions). If you are interested, please feel free to reach out to me directly to discuss more. This is a unique place that I have really enjoyed the past few years! Mark https://www.marksantolucito.com/

1 0

CFP: Workshop on Hardware Acceleration of Functional and Declarative Languages
by Rob Stewart 17 Oct '23

17 Oct '23

Hi haskell-cafe, Call for participation: HAFDAL 2024 The 1st Workshop on Hardware Acceleration of Functional and Declarative Languages (HAFDAL) will be co-located with HPCA, Edinburgh on March 2nd or 3rd 2024. This workshop will bring together computer architects and programming language implementers to explore software/hardware co-designs of high level execution models. We invite two forms of participation: (1) full paper submissions for 30 minute talks, (2) 5-10 minute lightning talks about related projects and early results. For full papers, we are looking for submissions that cover the motivation, design, or real-world application of hardware technology for functional/declarative languages, their compilers and runtime systems. Submission deadline: 20 November 2023. The call for participation and all key dates are here: https://haflang.github.io/images/hafdal24_cfp.pdf The workshop's website is: https://haflang.github.io/workshops/hafdal24.html Best wishes, Rob Stewart Associate Professor Mathematical and Computer Sciences Heriot-Watt University

1 0

Release: stan, supporting GHCs 8.8-9.4
by Tom Ellis 15 Oct '23

15 Oct '23

I'm pleased to announce a new release of `stan`, a static analysis tool for Haskell. `stan` now supports GHCs in the range 8.8-9.4[1]. ### About `stan` Stan is a command-line tool for analysing Haskell projects. It discovers which parts of the code can potentially be improved, and offers suggestions on how to do so. Read more about `stan` in its [`README`](https://github.com/kowainik/stan/#what-this-tool-is-about). ### Installation I recommend obtaining `stan` from Hackage by following [the installation instructions in the README](https://github.com/kowainik/stan/#hackage). https://hackage.haskell.org/package/stan-0.1.0.0 ### Help wanted `stan` lacks active maintainers and is currently in essential maintainance only mode. I am helping out to make sure `stan` can continue to build with newer GHCs. I would welcome assistance, particularly on the following issues: * Supporting GHC 9.6 * Supporting GHC 9.8 * Prospective support for GHC 9.10 * Fixing caching on Github Actions If you would like to contribute to Stan please [create an issue](https://github.com/kowainik/stan/issues) on the Github repository. ### Credits Thanks to the Kowainik team for creating `stan` in the first place. Thanks to Veronika Romashkina for accepting me as a new maintainer for the project. ---- [1] Some point releases are excluded because the GHC API doesn't seem to provide enough type information, notably the later releases in the 9.2 series.

1 1

CFP: Workshop on the Implementation of Type Systems (WITS) '24
by Richard Eisenberg 13 Oct '23

13 Oct '23

---------------------------------------------------------------------- CALL FOR CONTRIBUTIONS 3rd Workshop on the Implementation of Type Systems WITS 2024 January 20, 2024 London, United Kingdom https://popl24.sigplan.org/home/wits-2024 <https://popl24.sigplan.org/home/wits-2024> ---------------------------------------------------------------------- WITS 2024 is the third Workshop on the Implementation of Type Systems. The workshop will be held on January 20, 2024, in London, United Kingdom, co-located with POPL. The goal of this workshop is to bring together the implementors of a variety of languages with advanced type systems. The main focus is on the practical issues that come up in the implementation of these systems, rather than the theoretical frameworks that underlie them. In particular, we want to encourage exchanging ideas between the communities around specific systems that would otherwise be accessible to only a very select group. The workshop will have a mix of invited and contributed talks, organized discussion times, and informal collaboration time. *Scope* We invite participants to share their experiences, study differences among the implementations, and generalize lessons from those. We also want to promote the creation of a shared vocabulary and set of best practices for implementing type systems. Here are a few examples of topics we are interested to discuss: * syntax with binders and substitution * conversion modulo beta and eta * implicit arguments and metavariables * unification and constraint solving * metaprogramming and tactic languages * editor integration and automation * discoverability of language features * pretty printing and error messages This list is not exhaustive, so please contact the PC chairs in case you are unsure if a topic falls within the scope of the workshop. *Submissions* WITS solicits two kinds of submissions: * Contributed talks on the basis of an abstract. This can be on recently published or submitted work, work in progress, or a project that is still in the idea phase. * Proposals for roundtable discussions. This can be on any topic within the scope of the workshop, but should have a broader scope than a contributed talk. If accepted, you will be in charge of leading a discussion of 45 minutes around the proposed topic together with other interested attendees. Both kinds of proposals should be accompanied by an abstract of max. 1 page (exclusive of references), formatted according to the guidelines for SIGPLAN conferences: use the `sigplan` option to the `acmart` LaTeX document class. WITS will have no published proceedings, so submitting to WITS does not interfere with submission (before, after, or simultaneously) with other venues. Submissions are handled via https://wits24.hotcrp.com/ <https://wits24.hotcrp.com/>. *Important Dates* - Abstract submission deadline: 10 November, 2023 (AoE) - Notification: 1 December, 2023 - Workshop in London: 20 January, 2024 *Attendance and registration* WITS 2024 is colocated with POPL 2024 in London, UK. Information on registration and attendance will be posted on the POPL website at https://popl24.sigplan.org/ <https://popl24.sigplan.org/>. *Program Committee* Lennart Augustsson Epic Games, Sweden Edwin Brady St. Andrews, UK Jesper Cockx TU Delft, Netherlands co-chair Richard Eisenberg Jane Street, USA co-chair Jacques-Henri Jourdan CRNS, France Matthieu Sozeau INRIA, France Ningning Xie U. of Toronto, Canada

1 0

[ANNOUNCE] GHC 9.8.1 is now available
by Ben Gamari 13 Oct '23

13 Oct '23

The GHC developers are very pleased to announce the availability of the final release of GHC 9.8.1. Binary distributions, source distributions, and documentation are available at downloads.haskell.org: https://downloads.haskell.org/ghc/9.8.1 GHC 9.8 brings a number of new features and improvements, including: * Preliminary support the `TypeAbstractions` language extension, allowing types to be bound in type declarations [TypeAbstractions]. * Support for the `ExtendedLiterals` extension, providing syntax for non-word-sized numeric literals in the surface language [extended-literals] * Improved rewrite rule matching behavior, allowing limited matching of higher-order patterns * Better support for user-defined warnings by way of the `WARNING` pragma [warnings] * The introduction of the new `GHC.TypeError.Unsatisfiable` constraint, allowing more predictable user-defined type errors [unsatisfiable] * Implementation of the export deprecation proposal, allowing module exports to be marked with `DEPRECATE` pragmas [deprecated-exports] * The addition of build semaphore support for parallel compilation; with coming support in `cabal-install` this will allow better use of parallelism in multi-package builds [jsem] * More efficient representation of info table provenance information, reducing binary sizes by over 50% in some cases when `-finfo-table-map` is in use A full accounting of changes can be found in the [release notes][]. Plans for GHC's future releases can be found on the [GHC Wiki][status]. We would like to thank GitHub, IOG, the Zw3rk stake pool, Well-Typed, Tweag I/O, Serokell, Equinix, 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. Happy compiling, ~ Ben [TypeAbstractions]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0425-d… [extended-literals]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0451-s… [unsatisfiable]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0433-u… [warnings]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0541-w… [deprecated-exports]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0134-d… [jsem]: https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0540-j… [release notes]: https://downloads.haskell.org/ghc/9.8.1/docs/users_guide/9.8.1-notes.html [status]: https://gitlab.haskell.org/ghc/ghc/-/wikis/GHC-status

6 7

ambiguous type variable question
by Zoran Bošnjak 11 Oct '23

11 Oct '23

Hi all, I want to convert a type level structure to the value level structure of the same shape. This is the simplified example: {-# LANGUAGE AllowAmbiguousTypes #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE DataKinds #-} {-# LANGUAGE UndecidableInstances #-} module Test where import GHC.TypeLits import Data.Kind import Data.Proxy -- This data structure serves both for 'type level' and 'value level'. data Content n s b = ContentRaw | ContentTable [(n, s)] | ContentBool b deriving instance (Show n, Show s, Show b) => Show (Content n s b) -- Convert from types to values. class IsSchema s where type SchemaVal s :: Type schema :: SchemaVal s instance IsSchema 'ContentRaw where type (SchemaVal 'ContentRaw) = Content Integer String Bool schema = ContentRaw instance IsSchema ('ContentTable '[]) where type (SchemaVal ('ContentTable '[])) = Content Integer String Bool schema = ContentTable [] instance ( IsSchema ('ContentTable ts) , t ~ '(n, s), KnownNat n, KnownSymbol s , SchemaVal ('ContentTable ts) ~ Content Integer String Bool ) => IsSchema ('ContentTable (t ': ts)) where type SchemaVal ('ContentTable (t ': ts)) = Content Integer String Bool schema = case schema @('ContentTable ts) of ContentTable lst -> let n = natVal (Proxy @n) s = symbolVal (Proxy @s) in ContentTable ((n,s) : lst) _ -> error "internal error" If I remove the type parameter 'b', 'ContentBool b' and coresponding 'Bool' from the sample, the conversion works as expected. >>> schema @'ContentRaw ContentRaw >>> schema @('ContentTable ( '(1,"test1") ': '(2,"test2") ': '[])) ContentTable [(1,"test1"),(2,"test2")] But for some reason, as soon as I extend the example with 'b' and 'Bool' as shown above, it results in the following error: * Could not deduce (SchemaVal ('ContentTable ts) ~ Content Integer String b0) from the context: (IsSchema ('ContentTable ts), t ~ '(n, s), KnownNat n, KnownSymbol s, SchemaVal ('ContentTable ts) ~ Content Integer String Bool) bound by the instance declaration at test2.hs:(34,5)-(37,43) The type variable `b1' is ambiguous How do I fix it or how do I rewrite it to get the intended result? regards, Zoran

2 7

Call for Contributions: BOB 2024 [March 15, Deadline Nov 17]
by Stefan Wehr 11 Oct '23

11 Oct '23

================================================================================ BOB Conference 2024 "What happens when we use what's best for a change?" https://bobkonf.de/2024/cfc.html Berlin, Mar 17 Call for Contributions Deadline: November 17, 2023 ================================================================================ You are actively engaged in advanced software engineering methods, solve ambitious problem with software and are open to cutting-edge innovation? Attend this conference, meet people that share your goals, and get to know the best software tools and technologies available today. We strive to offer a day full of new experiences and impressions that you can use to immediately improve your daily life as a software developer. If you share our vision and want to contribute, submit a proposal for a talk or tutorial! NOTE: The conference fee will be waived for presenters. Travel expenses will not be covered (for exceptions see "Speaker Grants"). Shepherding ----------- The program committee offers shepherding to all speakers. Shepherding provides speakers assistance with preparing their sessions. Specifically: - advice on structure and presentation - review of talk slides - assistance with recording - review of recording, if applicable Speaker Grants -------------- BOB has Speaker Grants available to support speakers from groups under-represented in technology. We specifically seek women speakers, speakers of color, and speakers who are not able to attend the conference for financial reasons. Topics ------ We are looking for talks about best-of-breed software technology, e.g.: - functional programming - persistent data structures and databases - event-based modelling and architecture - "fancy types" (dependent types, gradual typing, linear types, ...) - formal methods for correctness and robustness - abstractions for concurrency and parallelism - metaprogramming - probabilistic programming - math and programming - controlled side effects - program synthesis - next-generation IDEs - effective abstractions for data analytics - … everything really that isn’t mainstream, but you think should be - … includeing rough ideas worth discussing. Presenters should provide the audience with information that is practically useful for software developers. Challenges ---------- Furthermore, we seek contributions on successful approaches for solving hard problems, for example: - bias in machine-learning systems - digital transformation in difficult settings - accessibiltity - systems with critical reliability requirements - ecologically sustainable software development We're especially interested in experience reports. Other topics are also relevant, e.g.: - introductory talks on technical background - overviews of a given field - demos and how-tos Requirements ------------ We accept proposals for presentations of 45 minutes (40 minutes talk + 5 minutes questions), as well as 90 minute tutorials for beginners. The language of presentation should be either English or German. Your proposal should include (in your presentation language of choice): - An abstract of max. 1500 characters. - A short bio/cv - Contact information (including at least email address) - A list of 3-5 concrete ideas of how your work can be applied in a developer's daily life - additional material (websites, blogs, slides, videos of past presentations, …) Organisation ------------ - Direct questions to konferenz at bobkonf dot de - Proposal deadline: November 17, 2023 - Notification: December 5, 2023 - Program: December 12, 2023 Submit here: https://pretalx.com/bob-2024/submit/ Program Committee ----------------- (more information here: https://bobkonf.de/2024/programmkomitee.html) - Matthias Fischmann, Wire - Matthias Neubauer, SICK AG - Nicole Rauch, Softwareentwicklung und Entwicklungscoaching - Michael Sperber, Active Group - Stefan Wehr, Hochschule Offenburg Scientific Advisory Board - Annette Bieniusa, TU Kaiserslautern - Torsten Grust, Uni Tübingen - Peter Thiemann, Uni Freiburg

1 0

[Haskell] [ANNOUNCE] Haskell Language Server 2.4.0.0 released
by Zubin Duggal 10 Oct '23

10 Oct '23

Binaries for this release are available at https://downloads.haskell.org/~hls/haskell-language-server-2.4.0.0/. These binaries can be installed using [GHCup](https://www.haskell.org/ghcup/) or the Haskell VSCode extension. All of these tarballs have associated GPG signatures. The signature should be from `Zubin Duggal <zubin(a)well-typed.com>` (key ID [588764FBE22D19C4](https://keys.openpgp.org/search?q=588764FBE22D19C4)) The prebuilt binaries in this release support the following GHC versions: - 9.0.2 - 9.2.8 - 9.4.7 - 9.6.3 - 9.8.1 # Changelog * Initial support for GHC 9.8.1, without plugins dependent on `ghc-exactprint` * Fix broken Windows binaries (#3822) Happy editing! - Zubin

1 0

XMonad for Wayland — seeking help
by Brandon Allbery 08 Oct '23

08 Oct '23

We on the XMonad devteam (Tomáš, Tony, Yecine, and myself) have been collecting contributions for the past two years with an eye toward paying someone to work on a port of XMonad to Wayland, since none of us is up to the task. We think we now have enough contributions coming in monthly to pay for someone to work with us on it. Problem is, we have no idea who can do this. So this is a call for help, looking for someone who can write it. There is an existing project <https://github.com/L-as/waymonad> but it’s badly bitrotted, including using a very old and buggy version of wlroots <https://gitlab.freedesktop.org/wlroots>, and L-as has had little time to revisit it. It’s not clear that it’s worth revisiting. One problem that’s unlikely to be solvable is that Wayland programs don’t set distinct identifiers that a manageHook could use, so the appName and className hooks can’t be ported. We welcome information to the contrary, though. So, help? Comments and especially proposals welcome on the Discourse thread <https://discourse.haskell.org/t/xmonad-for-wayland-call-for-help/7812>. -- brandon s allbery kf8nh allbery.b(a)gmail.com

1 0