- Haskell-Cafe - Haskell.org

ANN: Yampa 0.11
by Ivan Perez 06 Apr '18

06 Apr '18

Dear all, I'm happy to announce version 0.11 of Yampa! Yampa is a mature and robust FRP implementation that has been used to create mobile, desktop, and web games and applications, including games that use devices like wiimotes and kinect, as well as free and commercial mobile games available on iTunes and Google Play. (For reference, see [1-4].) This version includes documentation for all modules and all definitions. We have closed a total of 29 issues. Thanks to @ptvirgo for contributing to this release. A limitation of Haddock prevents us from achieving 100% coverage. Help with that would be appreciated [5, 6]. This version has been tested against all major GHC versions, from 7.6 to 8.4. A minor change in the low-level interface has triggered a major version bump (0.11). I would expect all projects that use Yampa to work by, at most, adapting the version constraints in the cabal files. Everybody is welcome to collaborate. The github repo includes some simple issues especially suitable for beginners, and we are working on the next major version. We are also exploring different research ideas related to FRP, and actively look for research collaborators. Hope you all enjoy it. Happy Haskelling! Ivan [1] https://github.com/ivanperez-keera/Yampa [2] https://github.com/ivanperez-keera/haskanoid [3] https://github.com/ksaveljev/yampa-2048 [4] https://haskell.games [5] https://github.com/haskell/haddock/issues/123 [6] https://github.com/ivanperez-keera/Yampa/issues/72

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Windows: how to perform cleanup actions when the console window closes
by Peter Dedecker 06 Apr '18

06 Apr '18

Hi Joachim, > You need to intercept the various events that may cause a console > windows to be closed; this is done via the Windows API call > SetConsoleCtrlHandler . > https://stackoverflow.com/a/30843219/6944068 gives an overview very informative, thanks! > I don't know how to register a Haskell function as a Windows callback, > that will have to be answered by somebody else. With your tips, I came across https://hackage.haskell.org/package/base-4.11.0.0/docs/GHC-ConsoleHandler.h…. (The documentation doesn't work, but you can look at the source to see the gist of it). I think this may do what you describe. The documentation for this function says that > When the event is received, if the > 'Handler' value is @Catch f@, then a new thread will be spawned by > the system to execute @f e@, where @e@ is the 'ConsoleEvent' that > was received. I wonder if I can add a handler function that detects Control-C and Close events, and responds by throwing a userInterrupt exception to the main thread, and then sleeping forever. The main thread then sees an asynchronous exception, the bracket cleanup action fires (which is my goal here), main thread shuts down and the program stops. Will try to experiment with that later. Thanks again Peter

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Windows: how to perform cleanup actions when the console window closes
by Peter Dedecker 06 Apr '18

06 Apr '18

Hello all, I have a console (command-line) Haskell application that communicates with some hardware equipment. The equipment needs to be initialized when my program starts, and needs to be cleanly shut down when the program ends. This is the basic structure of the program: main = readAvailableEquipment >>= \descs -> withEquipment descs $ \availableEquipment -> <<< more initialization then an infinite loop as a sockets-based server, communicating with the hardware via availableEquipment >>> withEquipment is defined as withEquipment descs action = bracket (initializeEquipment descs) closeEquipment action Basically I want closeEquipment to be executed when the program shuts down. The program is stopped by the user closing the console window (hitting the upper right 'X' in the Windows title bar). I would expect that the 'closeEquipment' action is performed since it is in the cleanup part of the 'bracket', but my testing suggests that these actions never execute. Incidentally, stopping the program via Ctrl-C doesn't work. I have tested this with GHC 8.2.2 installed via Stack (LTS 11.3). This is on Windows 10. Summary question and TLDR: how do I reliably perform cleanup actions in a Windows console program that is closed by the user by clicking the 'X' symbol in the window title bar? Thanks! Peter

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Re: [Haskell-cafe] Proposal: Professionalizing GHC Development
by Doug McIlroy 06 Apr '18

06 Apr '18

Gershom, An emergent team-building solution (with or without an enabling blockchain protection ring) is all very well, but is it monadic? Doug

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DataHaskell User Survey
by Marco Zocca 05 Apr '18

05 Apr '18

Dear all, the community around datahaskell.org has been slowly but steadily growing since its inception in 2016, and with it the diversity of its members. Its mission is to provide a home for data science and numerical computation students and practitioners who would like to use Haskell in their work and explorations. In order to best represent and serve the community, we'd like to know it in the first place, which is why we have prepared this little questionnaire (10 questions, which should take around 5 minutes to complete): https://www.surveymonkey.com/r/3FBBJWR No personal data are required and the results will only be published in aggregate form at a later stage. The raw data will only be stored and used for producing the aggregate report, after which it will be deleted. Thank you in advance for your time; Best, Marco Zocca github.com/ocramz hackage.haskell.org/user/ocramz

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[Haskell, FP] Anduril Industries is Hiring
by Travis Whitaker 05 Apr '18

05 Apr '18

Anduril Industries (https://www.anduril.com) is hiring. TL;DR: Come write Haskell, Rust, and Nix (and some C++ when necessary) to make autonomous robots and drones go! We're a team of software and hardware engineers from various backgrounds (game development, computer graphics, financial technology, government intelligence, biotechnology) working to improve the state of defense technology. Our strategy involves focusing on product development instead of traditional governmental processes. By funding product development ourselves instead of relying on government funds, we're able to create more focused products faster and with significantly fewer resources. By leveraging hardware and techniques that have only recently become feasible to deploy at scale (e.g. GPGPU computing), we can significantly advance the state of the defense technology market. We're searching for generally competent, mathematically inclined software engineers, and we're especially interested in those with experience in computer vision (first principles techniques and machine learning), sensor fusion, detection and tracking, and statistical parameter estimation. Our team is increasingly applying functional programming and related technologies; we run Haskell and Rust code in production and use Nix to achieve reproducible build environments and keep deployment, CI, and cross-compilation sane. If you like functional programming, interfacing with hardware, and solving problems in detection, tracking, and autonomous vehicle control (land and air), drop me a line at travis(a)anduril.com

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[ANN] Darcs 2.14.0 release
by Guillaume Hoffmann 04 Apr '18

04 Apr '18

Hi all, The Darcs team is pleased to announce the release of Darcs 2.14.0! Darcs is a free, open source revision control system. It is: * Distributed: Every user has access to the full command set, removing boundaries between server and client or committer and non-committers. * Interactive: Darcs is easy to learn and efficient to use because it asks you questions in response to simple commands, giving you choices in your work flow. You can choose to record one change in a file, while ignoring another. As you update from upstream, you can review each patch name, even the full "diff" for interesting patches. * Smart: Originally developed by physicist David Roundy, darcs is based on a unique algebra of patches. Learn more about Darcs on http://darcs.net . # Supported GHC and Cabal versions Darcs 2.14 can be compiled with GHC 8.0, 8.2 and 8.4, and supports Cabal versions from 1.24. # Windows issues Darcs 2.14 received many updates in its support of encoding. However, it may still contain bugs, especially under Windows, a platform for which we have fewer known users. Please let us know if you encounter weird behaviour under Windows. # What's new # ## User Interface ## - fix encoding business, make DARCS_DONT_ESCAPE_8BIT=1 default (Ben Franksen, Ganesh Sittampalam) - show explicit dependencies in `darcs log -s` (Gian Piero Carrubba) - improve bash/zsh completion (Ben, Gian Piero) - no longer print an error message when ctrlc'ing pager (Guillaume Hoffmann) - `darcs help markdown` mentions all files in `_darcs/prefs/` (Guillaume) - add patch index status to `show repo` command (Ben) ## New features ## - per-file conflict marking (Ben) - make it possible to use DARCS_SCP=rsync (Ben) - add --not-in-remote option to unrecord command (Ben) ## Performance ## - plug memory leak and improve efficiency in annotate (Ben) - save unneeded FL/RL reverses in SelectChanges module (Ben) - optimize token replace code and --look-for-replaces (Ben) - no longer show conflicting files on `whatsnew -s`, will reintrodue this feature when it is done efficiently (Guillaume) ## Developer-related ## - separate display and storage of patches (Ben) - support GHC 8.2 and GHC 8.4 (Ganesh) - many refactorings in Darcs.Repository modules and API (Ben, Guillaume) - no longer track build dependencies in Setup.hs, nor use alpha, beta, rc names (Guillaume) - refactor `pull --reorder-patches` (Ben) - refactor SelectChanges (Ben) - remove Patchy typeclass and redundant constaints where possible (Guillaume) - fix build with cabal new-build (Francesco Ariis) - unit and quickcheck tests for inventories (Ben) - throw out all access to bytestring internals from Darcs.Util.ByteString (Ben) - refactor, simplify, and document hunk application (Ben) - drop support of old cache location and SHA1-hashed repos (Guillaume) - rely on GHC's own stack traces for bug reporting (Guillaume) ## Issues resolved in Darcs 2.14 ## - fix mail encoding with '.' or '=' as last character (Timo von Holtz) - issue2526: whatsnew -l --boring should list boring files (Ben) - issue2208: replace detects existing force hunks in working (Ben) - issue2512: author name is written to repository after multiple-choice prompt (Stephan-A. Posselt) - issue2359: convert --export mishandles Unicode filenames (Ben) - issue2545: prevent argument smuggling in SSH repository URLs (Gian Piero) - issue2581: fix rebase pull --reorder (Ben) - issue2575: fix unrevert with rebase (Ben) - issue2579: allow darcs send to work even if no MTA is installed - issue2555: include explicit dependencies in the output of `log -v` (Gian Piero) - issue2569: decoding multibyte characters (Ben) - issue2563: create remote repo in correct format in ssh tests (Ben) - issue2565: create _darcs dir after searching for an existing one (Ben) - issue2567: darcs whatsnew --unified (Ben) - issue2566: avoid renaming across file systems (Ben) - issue2564: delete wrong and irrelevant propConcatPS (Guillaume) - issue2559: remove trailing empty lines in patch header edition (Guillaume) - issue2536: mask out internal matchers in `show files` routing logic (Gian Piero)

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ThEdu'18: Second Call for Extended Abstracts & Demonstrations
by Achim D. Brucker 04 Apr '18

04 Apr '18

(Apologies for duplicates) 2nd Call for Extended Abstracts & Demonstrations ************************************************************************** ThEdu'18 Theorem proving components for Educational software 18 July 2018 http://www.uc.pt/en/congressos/thedu/thedu18 ************************************************************************** affiliated to IJCAR 2018 July 14-17, 2018 Oxford, United Kingdom http://www.ijcar2018.org/ (part of FLoC 2018) ************************************************************************** THedu'18 Scope: Computer Theorem Proving is becoming a paradigm as well as a technological base for a new generation of educational software in science, technology, engineering and mathematics. The workshop brings together experts in automated deduction with experts in education in order to further clarify the shape of the new software generation and to discuss existing systems. Invited Talk Julien Narboux, University of Strasbourg, France Important Dates * Extended Abstracts: 15th April 2018 * Author Notification: 15th May 2018 * Workshop Day: 18 July 2018 Topics of interest include: * methods of automated deduction applied to checking students' input; * methods of automated deduction applied to prove post-conditions for particular problem solutions; * combinations of deduction and computation enabling systems to propose next steps; * automated provers specific for dynamic geometry systems; * proof and proving in mathematics education. Submission We welcome submission of extended abstracts and demonstration proposals presenting original unpublished work which is not been submitted for publication elsewhere. All accepted extended abstracts and demonstrations will be presented at the workshop. The extended abstracts will be made available online. Extended abstracts and demonstration proposals should be submitted via easychair, https://easychair.org/conferences/?conf=thedu18 formatted according to http://www.easychair.org/publications/easychair.zip Extended abstracts and demonstration proposals should be approximately 5 pages in length and are to be submitted in PDF format. At least one author of each accepted extended abstract/demonstration proposal is expected to attend THedu'18 and presents his/her extended abstract/demonstration. Program Committee Francisco Botana, University of Vigo at Pontevedra, Spain Roman Hašek, University of South Bohemia, Czech Republic Filip Maric, University of Belgrade, Serbia Walther Neuper, Graz University of Technology, Austria (co-chair) Pavel Pech, University of South Bohemia, Czech Republic Pedro Quaresma, University of Coimbra, Portugal (co-chair) Vanda Santos, CISUC, Portugal Wolfgang Schreiner, Johannes Kepler University, Austria Burkhart Wolff, University Paris-Sud, France Proceedings The extended abstracts and system descriptions will be available in ThEdu'18 Web-page. After presentation at the conference, selected authors will be invited to submit a substantially revised version, extended to 14--20 pages, for publication by the Electronic Proceedings in Theoretical Computer Science (EPTCS). -- Dr. Achim D. Brucker | Software Assurance & Security | University of Sheffield https://www.brucker.ch | https://logicalhacking.com/blog @adbrucker | @logicalhacking

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Where are rank-3 types necessary in practice for maintaining abstraction?
by Timotej Tomandl 04 Apr '18

04 Apr '18

Hello, So we need rank-2 type in runST :: (forall s. ST <https://hackage.haskell.org/package/base-4.11.0.0/docs/Control-Monad-ST.htm…> s a) -> a, to prevent s from appearing in a. I have been thinking about this for a bit, but I failed to come up with a practical situation, where rank-3 types are necessary for safety of some abstraction. The rank-3 example in here and any other I found, look very synthetic, i.e. limiting computation to id: https://ocharles.org.uk/blog/guest-posts/2014-12-18-rank-n-types.html and compared to the runST example of limiting a scope of a type variable for purposes of safety looks unnatural. Could anyone please point me to a practical example of rank-3 polymorphism, where it is necessary for safety of an abstraction, if it exists? I suspect there is a situation, where rank-3 is necessary for maintaining abstration exists, but I can't think of any. Any ideas about such situations and even better situations where this is used on hackage? Timotej Tomandl

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Database of real faults
by Gabriela Araujo Britto 04 Apr '18

04 Apr '18

Hi, I'd like to know if there exists a database of reproducible real faults in Haskell software, along the lines of defects4j (https://github.com/rjust/ defects4j/), or a related initiative. My intention is to use this for research in mutation testing. Thank you, Gabriela

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