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[ANNOUNCE] New release of SBV (v8.1)
by Levent Erkok 10 Mar '19

10 Mar '19

Levent Erkok <erkokl(a)gmail.com> Thu, Jul 20, 2017, 1:10 AM to Haskell I'm pleased to announce v8.1 release of SBV, a library for integrating SMT solvers into Haskell. This is a release with many new features. Some highlights: * Support for symbolic sum-types: Maybe/Either. (Thanks to Joel Burget for initiating these.) * Support for symbolic sets. * Support for uninterpreted-function values in models. * Support for validation of models coming from SMT-solvers for high-assurance. * An implementation of Dijkstra's weakest-precondition logic and a toy language for showing how to do Hoare style total-correctness proofs in SBV. * A new and better interface to the optimization engine supporting arbitrary metric spaces. * A bunch of other fixes, improvements, and examples. Full release notes are here: https://github.com/LeventErkok/sbv/blob/master/CHANGES.md Hackage: https://hackage.haskell.org/package/sbv Homepage: http://leventerkok.github.io/sbv/ Feedback and bug reports are most welcome. Happy proving! -Levent.

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Coercible between data A a b = A a b and (a, b)
by Georgi Lyubenov 08 Mar '19

08 Mar '19

Greetings! Is there any reason behind/what is the reason behind ``` data A a b = A a b ``` and ``` (a, b) ``` not being coercible? And in general all n-ary constructors not being coercible to one another? Thanks in advance! ======= Georgi

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Final steps in GHC's Trac-to-GitLab migration
by Ben Gamari 07 Mar '19

07 Mar '19

Hi everyone, Over the past few weeks we have been hard at work sorting out the last batch of issues in GHC's Trac-to-GitLab import [1]. At this point I believe we have sorted out the issues which are necessary to perform the final migration: * We are missing only two tickets (#1436 and #2074 which will require a bit of manual intervention to import due to extremely large description lengths) * A variety of markup issues have been resolved * More metadata is now preserved via labels. We may choose to reorganize or eliminate some of these labels in time but it's easier to remove metadata after import than it is to reintroduce it. The logic which maps Trac metadata to GitLab labels can be found here [2] * We now generate a Wiki table of contents [3] which is significantly more readable than GitLab's default page list. This will be updated by a cron job until underlying GitLab pages list becomes more readable. * We now generate redirects for Trac ticket and Wiki links (although this isn't visible in the staging instance) * Milestones are now properly closed when closed in Trac * Mapping between Trac and GitLab usernames is now a bit more robust As in previous test imports, we would appreciate it if you could have a look over the import and let us know of any problems your encounter. If no serious issues are identified with the staging site we plan to proceed with the migration this coming weekend. The current migration plan is to perform the final import on gitlab.haskell.org on Saturday, 9 March 2019. This will involve both gitlab.haskell.org and ghc.haskell.org being down for likely the entirety of the day Saturday and likely some of Sunday (EST time zone). Read-only access will be available to gitlab.staging.haskell.org for ticket lookup while the import is underway. After the import we will wait at least a week or so before we begin the process of decommissioning Trac, which will be kept in read-only mode for the duration. Do let me know if the 9 March timing is problematic. Cheers, - Ben [1] https://gitlab.staging.haskell.org/ghc/ghc [2] https://github.com/bgamari/trac-to-remarkup/blob/master/TicketImport.hs#L227 [3] https://gitlab.staging.haskell.org/ghc/ghc/wikis/index

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creating standalone executable with haskell
by Damien Mattei 06 Mar '19

06 Mar '19

i want to run Haskell code on a system i'm not administrator??? if i compile my haskell program rather than use interpreter (i never compile it) can i run the executable on another Linux platform which has nothing of haskell installed on it ( no runtime library,etc...) ? i already did that with Racket Scheme could it be done with GHC compiler or should i ask the system admin to install haskell platform? regards, damien

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Second call for papers, MPC 2019, Portugal
by Graham Hutton 05 Mar '19

05 Mar '19

Dear all, The next Mathematics of Program Construction (MPC) conference will be held in Portugal in October 2019, co-located with the Symposium on Formal Methods (FM). Paper submission is 3rd May 2019. Please share, and submit your best papers! Best wishes, Graham Hutton Program Chair, MPC 2019 ====================================================================== *** SECOND CALL FOR PAPERS -- MPC 2019 *** 13th International Conference on Mathematics of Program Construction 7-9 October 2019, Porto, Portugal Co-located with Formal Methods 2019 https://tinyurl.com/MPC-Porto ====================================================================== TIMELINE: Abstract submission 26th April 2019 Paper submission 3rd May 2019 Author notification 14th June 2019 Camera ready copy 12th July 2019 Conference 7-9 October 2019 KEYNOTE SPEAKERS: Assia Mahboubi INRIA, France Annabelle McIver Macquarie University, Australia BACKGROUND: The International Conference on Mathematics of Program Construction (MPC) aims to promote the development of mathematical principles and techniques that are demonstrably practical and effective in the process of constructing computer programs. MPC 2019 will be held in Porto, Portugal from 7-9 October 2019, and is co-located with the International Symposium on Formal Methods, FM 2019. Previous conferences were held in Königswinter, Germany (2015); Madrid, Spain (2012); Québec City, Canada (2010); Marseille, France (2008); Kuressaare, Estonia (2006); Stirling, UK (2004); Dagstuhl, Germany (2002); Ponte de Lima, Portugal (2000); Marstrand, Sweden (1998); Kloster Irsee, Germany (1995); Oxford, UK (1992); Twente, The Netherlands (1989). SCOPE: MPC seeks original papers on mathematical methods and tools put to use in program construction. Topics of interest range from algorithmics to support for program construction in programming languages and systems. Typical areas include type systems, program analysis and transformation, programming language semantics, security, and program logics. The notion of a 'program' is interpreted broadly, ranging from algorithms to hardware. Theoretical contributions are welcome, provided that their relevance to program construction is clear. Reports on applications are welcome, provided that their mathematical basis is evident. We also encourage the submission of 'programming pearls' that present elegant and instructive examples of the mathematics of program construction. SUBMISSION: Submission is in two stages. Abstracts (plain text, maximum 250 words) must be submitted by 26th April 2019. Full papers (pdf, formatted using the llncs.sty style file for LaTex) must be submitted by 3rd May 2019. There is no prescribed page limit, but authors should strive for brevity. Both abstracts and papers will be submitted using EasyChair. Papers must present previously unpublished work, and not be submitted concurrently to any other publication venue. Submissions will be evaluated by the program committee according to their relevance, correctness, significance, originality, and clarity. Each submission should explain its contributions in both general and technical terms, clearly identifying what has been accomplished, explaining why it is significant, and comparing it with previous work. Accepted papers must be presented in person at the conference by one of the authors. The proceedings of MPC 2019 will be published in the Lecture Notes in Computer Science (LNCS) series, as with all previous instances of the conference. Authors of accepted papers will be expected to transfer copyright to Springer for this purpose. After the conference, authors of the best papers from MPC 2019 and MPC 2015 will be invited to submit revised versions to a special issue of Science of Computer Programming (SCP). For any queries about submission please contact the program chair, Graham Hutton <graham.hutton(a)nottingham.ac.uk>. PROGRAM COMMITTEE: Patrick Bahr IT University of Copenhagen, Denmark Richard Bird University of Oxford, UK Corina Cîrstea University of Southampton, UK Brijesh Dongol University of Surrey, UK João F. Ferreira University of Lisbon, Portugal Jennifer Hackett University of Nottingham, UK William Harrison University of Missouri, USA Ralf Hinze University of Kaiserslautern, Germany Zhenjiang Hu National Institute of Informatics, Japan Graham Hutton (chair) University of Nottingham, UK Cezar Ionescu University of Oxford, UK Mauro Jaskelioff National University of Rosario, Argentina Ranjit Jhala University of California, USA Gabriele Keller Utrecht University, The Netherlands Ekaterina Komendantskaya Heriot-Watt University, UK Chris Martens North Carolina State University, USA Bernhard Möller University of Augsburg, Germany Shin-Cheng Mu Academia Sinica, Taiwan Mary Sheeran Chalmers University of Technology, Sweden Alexandra Silva University College London, UK Georg Struth University of Sheffield, UK CONFERENE VENUE: The conference will be held at the Alfândega Porto Congress Centre, a 150 year old former custom's house located in the historic centre of Porto on the bank of the river Douro. The venue was renovated by a Pritzer prize winning architect and has received many awards. LOCAL ORGANISERS: José Nuno Oliveira University of Minho, Portugal For any queries about local issues please contact the local organiser, José Nuno Oliveira <jno(a)di.uminho.pt>. ====================================================================== 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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cannot catch exception
by Kees Bleijenberg 05 Mar '19

05 Mar '19

Hi all, The program reads lots of small Text files. readCDFile handles the encoding. Below is the simplest version of readCDFile. If I call readCDFile "/home/kees/freeDB/inputError/" "blah" (the file blah does not exist) I get: Left "MyError: /home/kees/freeDB/inputError/blah: openBinaryFile: does not exist (No such file or directory)". The exception is caught by exceptionHandler If I call readCDFile "/home/kees/freeDB/inputError/" "67129209" I get freeDB: Cannot decode byte '\xa0': Data.Text.Internal.Encoding.decodeUtf8: Invalid UTF-8 stream. The exception is not caught by exceptionHandler (No "MyError: " in front). The file 67129209 is indeed bad encoded. I'am using SomeException. Still, this 'bad encoding exception' is not caught. Why? Kees import qualified Data.Text as T import System.FilePath.Posix import qualified Data.Text.Encoding as TE import qualified Data.ByteString.Lazy as B import Prelude hiding (catch) import Control.Exception main :: IO () main = do res <- readCDFile "/home/kees/freeDB/inputError/" "67129209" print res readCDFile :: FilePath -> FilePath -> IO (Either String T.Text) readCDFile baseDir fn = do catch ( do buffer <- B.readFile (combine baseDir fn) let bufferStrict = B.toStrict buffer return $ Right $ TE.decodeUtf8 bufferStrict ) exceptionHandler exceptionHandler :: SomeException -> IO (Either String T.Text) exceptionHandler e = do let err = show e return $ Left $ "MyError: " ++ err --- Dit e-mailbericht is gecontroleerd op virussen met Avast antivirussoftware. https://www.avast.com/antivirus

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Haskell wiki account request response time
by Howard B. Golden 04 Mar '19

04 Mar '19

Hi Michal, You requested a Haskell wiki account at Fri, 1 Mar 2019 16:08:10 +0100 > Date: Fri, 1 Mar 2019 16:08:10 +0100 > From: Miguel <m.i(a)gmx.at> > To: wiki-account-request(a)haskell.org > Subject: wiki-account-request > oo_miguel Then, 8 minutes, 25 seconds later, you sent this message to Haskell-Cafe: > From: m.i at gmx.at (Miguel) > Date: Fri, 1 Mar 2019 16:16:35 +0100 > Subject: [Haskell-cafe] wiki-account-request > Message-ID: <20190301151635.kkpq2m4x7fkbftqj(a)megaloman.softwarefools.com> > Hi, > Not receiving any response from the other channel I hereby request a > wiki.haskell.org account with the preferred username: "oo_miguel" > Thanks in Advance, > Michal Idziorek > Ref: > https://wiki.haskell.org/index.php?title=Special:UserLogin > "If you would like an account please email 'wiki-account-request' > (at the domain haskell dot org) or, if you find that unresponsive, > on the haskell-cafe mailing list." At Fri, 1 Mar 2019 18:36:00 +0100, Henk-Jan_van_Tuyl created your account. This was 2 hours and 28 minutes after your initial request. Generally, we create accounts within 24 hours of their request, often much sooner. All of us who create accounts are volunteers. We create accounts manually to prevent spam. Regards, Howard

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PR to "double-conversion"
by Иван Николаев 02 Mar '19

02 Mar '19

Hi Bryan! May I ask you to take a look at my PR to your double-conversion library? I’ve made it about six months ago and sent you an email. A few days ago I updated it. In the PR mentioned above I’m adding several things which need your attention: 1. Conversion to bytestring and text builder. 2. Conversion of Float (using type family, but without performance degrading). 3. More benchmarks. 4. Update of the original double-conversion library. Now a bunch of 20k doubles is converted to strict bytestring in 5-8 ms using bytestring builder instead of >200-300ms using just bytestring. Cheers, Rinat

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ANN: hledger-1.14
by Simon Michael 02 Mar '19

02 Mar '19

I'm pleased to announce the release of hledger 1.14! Thank you release contributors Jakob Schöttl and Jakub Zárybnický. hledger is a robust, cross-platform plain text accounting tool, for tracking money, time, stocks, cryptocurrencies or any other commodity, using double-entry accounting, private or shared plain text files, revision control, and command-line, curses or web UIs. Find out more at http://hledger.org and http://plaintextaccounting.org. Release notes summary: ---------------------- Inclusive balance assertions, commodities command, --invert option, JSON get/add support in hledger-web. For full details, see http://hledger.org/release-notes. Getting started: ---------------- All install methods are described at http://hledger.org/download . (system packages, windows binaries, docker, nix, cabal, stack, hledger-install bash script..) Some of these might take a few days to become up to date. Tutorials and all docs and support options are linked at http://hledger.org . Get help via chat in #hledger on Freenode: http://irc.hledger.org Or connect via Matrix: http://riot.hledger.org New and old users, contributors, sponsors, positive/negative feedback, always welcome! Best, -Simon

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wiki-account-request
by Miguel 01 Mar '19

01 Mar '19

Hi, Not receiving any response from the other channel I hereby request a wiki.haskell.org account with the preferred username: "oo_miguel" Thanks in Advance, Michal Idziorek Ref: https://wiki.haskell.org/index.php?title=Special:UserLogin "If you would like an account please email 'wiki-account-request' (at the domain haskell dot org) or, if you find that unresponsive, on the haskell-cafe mailing list."

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