- Haskell-Cafe - Haskell.org

Polymorphic equality in LiquidHaskell
by Henning Thielemann 24 Oct '24

24 Oct '24

I want to assert statically assert equality of polymorphic parameters using LiquidHaskell. See for instance the following simplified Array type containing an array shape and for demonstration purposes only a single element: data Array sh a = Array {shape :: sh, element :: a} {-@ lift2 :: (Eq sh) => (a -> b -> c) -> arrA : Array sh a -> {arrB : Array sh b | shape arrA == shape arrB} -> Array sh c @-} lift2 :: (Eq sh) => (a -> b -> c) -> Array sh a -> Array sh b -> Array sh c lift2 f (Array sha a) (Array shb b) = if sha == shb then Array sha $ f a b else error "shapes mismatch" Running liquidhaskell yields Illegal type specification ... Sort Error in Refinement: {arrB : (Example.Equality.Array sh##a31s b##a31u) | Example.Equality.shape arrA == Example.Equality.shape arrB} Unbound symbol Example.Equality.shape I think the Haskell function (==) is not automatically lifted to LiquidHaskell's logic language. Is there another way to assert a kind of equality in LiquidHaskell?

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Configuring cabal to tell HPC to ignore certain functions
by Ivan Perez 23 Oct '24

23 Oct '24

Hi Café I want to configure a cabal package (specifically, copilot-core) so that, when HPC is executed during testing with coverage enabled, it ignores certain definitions, for example: - Anything that is auto-generated (e.g., Show). - Data constructors and field accessors, for which GHC also defines functions automatically, are all assumed to work. - Proxy doesn't need to be WHNFed. I think there's a way to extract the tix file and modify it, but I'm trying to make this automated, and configure the cabal package so that the right options are passed by cabal to HPC. That way, even hackage will pick it up when it reports the coverage of our library. Any pointers? Thanks! Ivan

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[ANNOUNCE] GHC 9.8.3 is now available
by Ben Gamari 20 Oct '24

20 Oct '24

The GHC developers are happy to announce the availability of GHC 9.8.3. Binary distributions, source distributions, and documentation are available on the [release] page. This release is primarily a bugfix release the 9.8 series. These include: * Significantly improve performance of code loading via dynamic linking (#23415) * Fix a variety of miscompilations involving sub-word-size FFI arguments (#25018, #24314) * Fix a rare miscompilation by the x86 native code generator (#24507) * Improve runtime performance of some applications of `runRW#` (#25055) * Reduce fragmentation when using the non-moving garbage collector (#23340) * Fix source links in Haddock's hyperlinked sources output (#24086) A full accounting of changes can be found in the [release notes]. 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! - Ben [release]: https://www.haskell.org/ghc/download_ghc_9_8_3.html [ticket]: https://gitlab.haskell.org/ghc/ghc/-/issues/new [release notes]: https://downloads.haskell.org/~ghc/9.8.3/docs/users_guide/9.8.3-notes.html

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attpoarsec and recursive parsing
by PICCA Frederic-Emmanuel 18 Oct '24

18 Oct '24

Hello I have this type data MaskLocation = MaskLocation Text | MaskLocation'Tmpl Text | MaskLocation'Or MaskLocation MaskLocation deriving (Eq, Generic, Show) deriving anyclass (FromJSON, ToJSON) instance FieldEmitter MaskLocation where fieldEmitter (MaskLocation t) = t fieldEmitter (MaskLocation'Tmpl t) = t fieldEmitter (MaskLocation'Or l r) = fieldEmitter l <> " | " <> fieldEmitter r I just added the MaskLocation'Or constructor in order to allow writing "mymask.npy | mymask2.npy | ..." So my question how should I write the new parser here the parser for the MaskLocation without the MaskLocation'Or instance FieldParsable MaskLocation where fieldParser = do t ← takeText pure $ if "{scannumber:" `Data.Text.isInfixOf` t then MaskLocation'Tmpl t else MaskLocation t It seems to me that I need to consume all text until I find a '|', call the parser on the collected text and start again the process. But I do not have a clear idea of how to collect all the values once the process is over. If someone could help me design this parser, It would be great. thanks a lot Frederic

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Call for Proposals Now Open for Functional Conf 2025 (online)
by John Sinclair 17 Oct '24

17 Oct '24

Attention all functional programming enthusiasts and experts! The Functional Conf 2025 Call for Proposals is now open, and it's a golden opportunity to share your insights and innovative applications of functional programming with a vibrant community of like-minded individuals. Whether you have tackled a tricky problem using functional programming, developed a unique application, or have experiences that could enlighten your peers, we want to hear from you! We're open to all topics related to functional programming. We are seeking deep technical topics that push the boundaries of what's possible with functional programming. Our commitment to diversity and transparency means all proposals will be public for community review. Is your proposal unique? Is it well-developed and ready-to-go? Then you've got what it takes! Submit your ideas and help us make Functional Conf 2025 an unforgettable experience. Submit your proposal today and help shape the future of functional programming! https://confengine.com/conferences/functional-conf-2025/proposals<https://confengine.com/conferences/functional-conf-2025/proposals?utm_mediu…> Submission deadline: 17 November 2024 Functional Conf is an online event running 24-25 January 2025. Learn more about the conference: https://functionalconf.com

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POPL 2025 Call for Tutorials (deadline extended: Oct 25th, 2024)
by Ningning Xie 17 Oct '24

17 Oct '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 25th, 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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Re: [Haskell-cafe] [ANNOUNCE] GHC 9.12.1-alpha1 is now available
by Vanessa McHale 16 Oct '24

16 Oct '24

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anyone using wxHaskell
by Zoran Bošnjak 15 Oct '24

15 Oct '24

Dear haskell cafe, I have a problem with scrolledWindow inside notebook, when running with the latest version of wxHaskell. See the minimal example below, where the scrollbar is not shown (the same sample is OK on the wxHaskell version from few years ago). I would appreciate a suggestion how to make the scrollbar work again (a workaround if possible). I have also filed the issue on the wxHaskell project page. But the project does not look like being super actively maintained. https://codeberg.org/wxHaskell/wxHaskell/issues/48 Minimal example: module Main where import Graphics.UI.WXCore import Graphics.UI.WX gui :: IO () gui = do f <- frame [text := "Frame"] p <- panel f [] nb <- notebook p [] p1 <- scrolledWindow nb [ scrollRate := sz 20 20 ] texts <- mapM (\n -> staticText p1 [text := ("test" <> show n) ]) [1::Int ..20] set f [ layout := fill $ widget p , clientSize := sz 400 200 ] set p [ layout := fill $ tabs nb [ tab "tab1" $ container p1 $ column 5 (fmap widget texts) ] ] main :: IO () main = start gui regards, Zoran

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Re: [Haskell-cafe] Runtime selection on types while capturing a dictionary?
by Benjamin Redelings 14 Oct '24

14 Oct '24

On 10/9/24 10:11 AM, Benjamin Redelings wrote: > Interesting! And thanks. I've been able to move the labels into the > Graph class, and just use () as the label type when I don't want > labels. Somehow I was expecting a Haskell mailing list to recommend > something involving DataKinds. > > The other augmentations are a bit more tricky. The tree can have > either a BranchLength augmentation OR a NodeTime augmentation, but not > both. The NodeTime augmentation only makes sense when the tree is > rooted. Additionally, it makes sense on rooted forests and directed > acyclic graphs. When using the NodeTime augmentation, we can > CALCULATE the branch lengths as the time difference between the nodes > at the two ends of a branch. This provides some motivation to make > the branchLength function polymorphic, so that some of the downstream > code can be agnostic as to whether the branch lengths are directly > augmented, or computed from NodeTimes. And then there is also a > BranchRate augmentation that only makes sense if we have a NodeTime > augmentation. > > I think your ADT makes more sense than just creating a lot of > (AddAugmentationX ExtraInfo Graph) data types. So, I'll have to think > how to do that. > > On the other hand, I would like to retain some polymorphism. For > example, it would be nice to allow multiple tree representations. > Sometimes a generic graph is what you want, but in other cases the > tree-generation process makes a data structure like > > data Tree = Leaf {parent :: Maybe Tree } | Internal { left:: Tree, > right:: Tree, parent:: (Maybe Tree)} > > more natural. So, having an IsGraph *class* versus just a single > Graph data structure seems valuable. > > QUESTION: Given that, can you expand on what counts as a type-class > "shenanigan"? I fully agree that the class structure and the data > type structure isn't very good yet. (It was implemented in haste to > make something "just work". The standard format for printing trees -- > Newick format -- really prints rooted trees, so I ended up creating a > 'type family Rooted t' to make a rooted tree type from an unrooted > tree type. That seems very hacky.) But I would like to retain some > generality across common features between NodeTime and BranchLength > augmented trees, as well as (perhaps) generality across different > implementations of Graph / Tree. > > QUESTION: For the constraint that a NodeTime tree should be rooted, do > you think I should encode this constraint at the data-type level, or > at the function level? I was initially thinking of encoding this at > the data type level, so that you couldn't construct a tree with node > times that was not rooted. But I suppose one could simply make all the > functions that USE node-time trees require some kind of Rooted > constraint by calling a function like 'parent node'. This would > decouple the Rooted/Unrooted augmentation from the BranchLength / > NodeTime / Nothing augmentation. Thoughts? > > -BenRI > > > On 10/7/24 6:13 PM, Tom Ellis wrote: >> On Mon, Oct 07, 2024 at 05:38:30PM -0400, Benjamin Redelings wrote: >>> I'm new to Haskell, and I'm writing a class for evolutionary trees. >>> Since >>> I'm new to Haskell, trying to encode information at the type level >>> is new to >>> me. In C++ I'd use runtime checks to ask whether (for example) a >>> tree is >>> rooted. Or I'd have the getRoot function return Maybe NodeID and >>> then make >>> the methods for checking if a branch points rootward throw an >>> exception if >>> the tree is unrooted. >> I think I'd just do >> >> data AugmentedTree roots lengths labels = >> MkAugmentedTree { >> tree :: Tree, >> labels :: labels, >> roots :: roots, >> lengths :: lenghts >> } >> >> and then just do stuff like >> >> type FullyAugmentedTree = >> AugmentedTree [NodeId] (IntMap Double) (IntMap (Maybe l)) >> type PartiallyAugmentedTree = >> AugmentedTree [NodeId] () (IntMap (Maybe l)) >> >> For rootedness-independence I strongly recommend against any type >> class shenanigans. Instead you can do >> >> data PossiblyRootedTree lengths labels where >> RootedTree :: AugmentedTree [NodeId] lengths labels >> UnrootedTree :: AugmentedTree () lengths labels >> >> and then >> >> isRooted :: PossiblyRootedTree lengths labels -> Bool >> isRooted = \case >> RootedTree {} -> True >> UnrootedTree {} -> False >> >> (but `isRooted` is not really very useful compared to just pattern >> matching every where you need to know.) >> >> Tom >> _______________________________________________ >> Haskell-Cafe mailing list >> To (un)subscribe, modify options or view archives go to: >> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe >> Only members subscribed via the mailman list are allowed to post.

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Call for Contributions: BOB 2025 (Berlin, March 14 - Deadline Nov 15)
by Stefan Wehr 14 Oct '24

14 Oct '24

================================================================================ BOB Conference 2025 "What happens when we use what's best for a change?" https://bobkonf.de/2025/cfc.html Berlin, Mar 14 Call for Contributions Deadline: November 15, 2024 ================================================================================ 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 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 15, 2024 - Notification: December 4, 2024 - Program: December 11, 2024 Submit here: https://pretalx.com/bob-2025/submit/ Program Committee ----------------- (more information here: https://bobkonf.de/2025/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

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