- Haskell-Cafe - Haskell.org

ANNOUNCE: bank-holidays-england: Calculation of bank holidays in England and Wales
by David Turner 12 Dec '15

12 Dec '15

Hi all, A very belated announcement of a little library that implements the frankly daft rules for calculating the dates of bank holidays in England and Wales. With apologies to the Welsh for the abbreviated package name, and to the Scots for not including yours too. http://hackage.haskell.org/package/bank-holidays-england Comments and feature requests are most welcome. Cheers, David

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ANNOUNCE: alarmclock-0.2.0.8: wake up at a certain time
by David Turner 12 Dec '15

12 Dec '15

Hi all, A very belated announcement of a little library for efficiently waking up at a certain time. I've found this useful for things like timeouts, scheduling retries, cache expiry and so on. Not a lot to say, really, it does what it says on the tin! http://hackage.haskell.org/package/alarmclock Comments and feature requests are most welcome. Cheers, David

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[ANNOUNCE] Glasgow Haskell Compiler version 7.10.3
by Ben Gamari 12 Dec '15

12 Dec '15

Hello everyone, We are pleased to announce the release of GHC 7.10.3: https://downloads.haskell.org/~ghc/7.10.3/ There can be found source tarballs and binary distributions for 64-bit and 32-bit modern Linux (GMP 5.0 or later), CentOS (GMP 4.0), Windows, and 64-bit Mac OS X platforms. These binaries and tarballs have an accompanying SHA256SUMS file signed by my GPG key id (0x97DB64AD). Significant fixes in release include changes to the simplifier's treatment of rules, the handling of Mac OS X frameworks, and support for response files to work around the restrictive command line length limit on Windows. As always, a full accounting of the changes present in this release can be found in the release notes [1]. The previous release, 7.10.2, was well-behaved save a couple notable bugs; while we have merged a good number of bug fixes in 7.10.3 they were were largely low risk and so we expect that this release should be similiarly stable. A notable exception is the upgrade of the Windows compiler toolchain to GCC 5.2. Typically we would refrain from making such large changes in a point release but Windows users have been long suffering at the hand of the old toolchain (e.g. lack of response file support, #8596, and lack of SEH support). We expect that this change should fix far more than breaks. Unfortunately, due to some oversights in the release process there are two source tarballs for this release. The first, ghc-7.10.3-src.tar.{bz2,xz}, does not include the release notes in the users guide. This is fixed in the second patchlevel release, ghc-7.10.3a-src.tar.{bz2,xz}. It is recommended that users wanting a source release use the ghc-7.10.3a-src tarballs. GHC 7.10.3 will very likely be the last release in the GHC 7 series. In the coming weeks we will be beginning the release process for GHC 8.0, which will include a number of exciting features including the merger of kinds with types, injective type families, imporved DWARF debugging information, applicative-do syntax, a Strict language extension synonyms mechanism, and more. See the GHC 8.0.1 status page for details [2]. Happy compiling! Cheers, - Ben [1] http://downloads.haskell.org/~ghc/7.10.3/docs/html/users_guide//release-7-1… [2] https://ghc.haskell.org/trac/ghc/wiki/Status/GHC-8.0.1

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Audio search library; and debugging help!
by Richard Lewis 11 Dec '15

11 Dec '15

Hi there, For a little while I've been working on an audio search library. It wraps over a C++ library written by some of my colleagues. It's nearing the state where someone other than me might actually be able to use it. So this message is partly an annoucement: <https://github.com/TransformingMusicology/libaudioDB-haskell> I'd be very interested to hear if anyone has a go at installing it and running the "tests". But this message is also a request for help, because I'm actually stuck with a bug. I've created a fork of the above repo here: <https://github.com/ironchicken/libaudioDB-haskell> which includes an extra commit which adds quite a few tracing statements. So if anyone feels up to trying to help me with my bug, then this would be the repo to use. The bug goes something like this: One of the features I need to implement is so-called "query rotation". The library implements audio feature searching. For some kinds of multi-dimensional audio features, it's useful to execute queries with them repeatedly moving the values between the dimensions each time to get a kind of exhaustive search. As a specific example (and for those who know a little music theory), there's a feature known as chroma which gives a measure of the signal energy in each of the 12 pitch classes for each window in the audio. If you search with a vector of chroma features, you will only find results that are at exactly the same pitch. But if you shift the chroma search vector around 11 times, you can effectively search for the query vector in every transposition (that's "transposition" as in to transpose in music theory). Anyway, I've tried to capture this in the library by allowing a call to the Sound.Audio.Database.Query.query function to include a QueryTransformer, which is essentially a function which takes a query and returns a new query. And then one instance of this is the function S.A.D.Query.mkSequenceQueryWithRotation which uses another helper function, S.A.D.Query.mkSequenceQueryMutateDatum. This function takes a Ptr to a query, and scribbles over the memory to replace its contents with an altered query vector: the result of some mutation function. Now, what originally alerted me to there being anything wrong with this was that, when I execute a rotated query, I'm getting exactly the same results as for a non-rotated query. As I started investigating, the first thing I found was that the altered feature vectors were not being altered in the way I expected. If I printed them and traced the path of a single value, it wasn't moving step-wise between the bins, but instead jumping around between them randomly. I eventually put in enough putStrLn and trace calls to find that, I think, each time the query is transformed, instead of doing just one transformation, it does as many transformations as times it has iterated: i.e., first iteration it does one transformation, second iteration it does two transformations, and so on. The recursive (sort of iterative?) query transformation is implemented in S.A.D.Query.queryWithTransformPtr. But I'm now at a loss to say whether there's anything actually wrong with this function. So, I think this is the end of my message. I appreciate that this is a very specific problem. I know it's normally helpful to try and abstract a problem into something in terms of Foos and Bars, but I'm not sure I can do this here. As a result, it would be a significant undertaking for anyone to try and help out. So I would be even more grateful than usual if anyone could! (And that's not really meant as a grovelling plea, it's actually more of a warning: you probably shouldn't try and help me.) Thanks, Richard -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Richard Lewis Computing, Goldsmiths' College t: +44 (0)20 7078 5203 @: lewisrichard http://www.transforming-musicology.org/ 905C D796 12CD 4C6E CBFB 69DA EFCE DCDF 71D7 D455 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

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Darcs Hacking Sprint #10 (January 15th-17th, Seville)
by Guillaume Hoffmann 11 Dec '15

11 Dec '15

Dear Hackers I'm glad to announce that the 10th Darcs Sprint that will be in Seville, on January 15-17 at the ETS de Ingeniería Informática, Universidad de Sevilla. Please check the details at: http://darcs.net/Sprints/2016-01 Here are three things to know 1. Everybody is welcome to join us. We'd love to have you, whatever your Haskell or Darcs hacking experience. Also, if you've got a wacky idea for the future of version control, or a cool use for the Darcs library, you should join us too :-) 2. Please let us know if you're attending: * add your name to http://wiki.darcs.net/Sprints/2016-01 * send me (privately) your full name and some official identification number for access to the university on Saturday and Sunday. 3. We can reimburse travel costs (within reason!). Let us know if you'd like a reimbursement, and save your receipts. Many thanks to everybody who participated in our fundraising drives or who gave money on the side. Thanks also to the Software Freedom Conservancy for making fundraising and reimbursements so painless! If you can't join us in person, but you'd like to cheer us on, say hello at http://darcs.net/Donations ! see you in one month! Guillaume

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Looking for maintainers for emacs-haskell-tutorial
by Alejandro Serrano Mena 11 Dec '15

11 Dec '15

Dear Haskell-Café, Some time ago, and as part of my Google Summer of Code project, I wrote a tutorial about setting up Emacs to work with Haskell [ https://github.com/serras/emacs-haskell-tutorial/blob/master/tutorial.md] The tutorial is now a bit outdated and several issues are pending solution [ https://github.com/serras/emacs-haskell-tutorial/issues] However, due to other (young, crying) obligations I don't have the time needed to maintain the tutorial anymore, all by myself. Thus, I would like to ask whether somebody is willing to maintain the tutorial up-to-date, and take care of the issues. Or simply, whether somebody is willing to help in doing so. Regards, Alejandro

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setting up property tests
by Michael Litchard 10 Dec '15

10 Dec '15

I've got a little project, based off of fizzbuzz, that I would like to write property tests for using either QuickCheck or SmallCheck. Could someone have a look at https://github.com/mlitchard/fizzbuzzfib/blob/master/src/FizzBuzz.hs and help me sort out how to write property tests?

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FLOPS 2016: Call for Participation and Posters/Demos
by Oleg 10 Dec '15

10 Dec '15

FLOPS 2016: 13th International Symposium on Functional and Logic Programming March 4-6, 2016, Kochi, Japan http://www.info.kochi-tech.ac.jp/FLOPS2016/ Call for Participation and Posters/Demos Registration will be open on Monday, Dec 21, 2015. Early registration deadline is Monday, Feb 8, 2016. Poster/Demo abstract submission deadline is Monday, Jan 11, 2016. FLOPS aims to bring together practitioners, researchers and implementers of the declarative programming, to discuss mutually interesting results and common problems: theoretical advances, their implementations in language systems and tools, and applications of these systems in practice. The scope includes all aspects of the design, semantics, theory, applications, implementations, and teaching of declarative programming. FLOPS specifically aims to promote cross-fertilization between theory and practice and among different styles of declarative programming. In addition to the presentations of regular research papers, the FLOPS program includes tutorials, as well as the poster/demo session for demonstrating the tools and systems described during the talks and for presenting works-in-progress and getting the feedback. FLOPS has established a Best Paper award. The winner will be announced at the symposium. CALLS FOR POSTERS AND DEMONSTRATIONS If you wish to present a poster at FLOPS, please send the plain text abstract by e-mail to <flops2016(a)easychair.org> -- by January 11, 2016. The abstract should include the title, the names of the authors and their affiliation, along with enough details to judge its scope and relevance. We will announce the accepted submissions on January 25, 2016. The format of the poster will be announced at that time. Important Dates * Submission due: January 11, 2016 (Monday), any time zone * Notification: January 25, 2016 (Monday) INVITED TALKS Kazunori UEDA (Waseda University) The exciting time and hard-won lessons of the Fifth Generation Computer Project Atze Dijkstra (Utrecht University) UHC: Coping with Compiler Complexity TUTORIALS Andreas Abel, on Agda Atze Dijkstra, on Attribute Grammars Neng-Fa Zhou, on programming in Picat ACCEPTED PAPERS Ki Yung Ahn and Andrea Vezzosi. Executable Relational Specifications of Polymorphic Type Systems using Prolog Markus Triska. The Boolean Constraint Solver of SWI-Prolog: System Description Peng Fu, Ekaterina Komendantskaya, Tom Schrijvers and Andrew Pond. Proof Relevant Corecursive Resolution Jay McCarthy, Burke Fetscher, Max New and Robert Bruce Findler. A Coq Library For Internal Verification of Running-Times Akimasa Morihata. Incremental Computing with Abstract Data Structures Wouter Swierstra and Joao Alpuim. >From proposition to program: embedding the refinement calculus in Coq Andre Van Delft and Anatoliy Kmetyuk. Declarative Programming with Algebra Ian Mackie and Shinya Sato. An interaction net encoding of Godel's System T Arthur Blot, Pierre-Evariste Dagand and Julia Lawall. >From Sets to Bits in Coq Jeremy Yallop, David Sheets and Anil Madhavapeddy. Declarative foreign function binding through generic programming Praveen Narayanan, Jacques Carette, Wren Romano, Chung-Chieh Shan and Robert Zinkov. Probabilistic inference by program transformation in Hakaru: System description Francisco Javier Lopez-Fraguas, Manuel Montenegro and Juan Rodriguez-Hortala. Polymorphic Types in Erlang Function Specifications Remy Haemmerle, Pedro Lopez-Garcia, Umer Liqat, Maximiliano Klemen, John Gallagher and Manuel V. Hermenegildo. A Transformational Approach to Parametric Accumulated-cost Static Profiling Taus Brock-Nannestad. Space-efficient Planar Acyclicity Constraints: A Declarative Pearl

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ANNOUNCE: Haskell Platform 7.10.3
by Gershom B 10 Dec '15

10 Dec '15

Haskellers, we are pleased to announce the release of Haskell Platform 7.10.3 * * get it here: https://www.haskell.org/platform/ * * Highlights include: - GHC 7.10.3 - Major version bumps to - HUnit - OpenGL - OpenGLRaw - syb - Minor version bumps to - Cabal - case-insensitive - fgl - GLUT - GLURaw - primitive Full package and version list: https://www.haskell.org/platform/contents.html GHC release notes can be found at: http://downloads.haskell.org/~ghc/7.10.3/docs/html/users_guide/release-7-10… This is the first release in which I've taken over as release manager. Thanks to Erik Rantapaa, Ben Gamari, Randy Polen and Jason Dagit for various platform related work; thanks to Oleg Grenrus and John Wiegley for additional testing; and thanks of course to Mark Lentczner for developing the new streamlined HP build process that has made things so much easier for all of us. * Windows Notes * The Haskell Platform on Windows now provides the MSys2 tools. These tools are needed when installing packages that use conf-tools (generally rare). These tools are not automatically placed onto the PATH in order avoid troubles due to MSys2 tools which have the same name as a standard Windows tool (e.g., echo, find, dir). * Future Plans * As per the November 13 email on "Haskell Platform Plans" (https://mail.haskell.org/pipermail/haskell-cafe/2015-November/122171.html) this is a modest release for ghc, and also a modest release for the platform, to put a capstone on the 7.10 series. Coming with the 8.0 platform we'll have lots of the exciting stuff that has been long promised, including a minimal distro without extra packages, a bundled stack binary, and a much-improved experience for installing build-type: configure packages (such as network) on Windows. Issues can be reported on the github tracker: https://github.com/haskell/haskell-platform/issues * Known Issues * As the platform builds were done from the tarballs lacking 7.10.3 release notes, those notes will not be present in the installed users' guides. However, they are available online, as in the link given above. Happy Haskelling, Gershom Bazerman, Haskell Platform release manager

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parsing and printing - applicative style?
by Johannes Waldmann 09 Dec '15

09 Dec '15

Dear Cafe, what is the current state of the art (and notation) in writing combined parser/printers? (as in Rendel/Ostermann ICFP 2010, http://lambda-the-ultimate.org/node/4191 ) >From the paper I get the impression that this is, or could be, a nice showcase for Applicative and Alternative. Indeed, if parsing a text in a (programming) language is separated from semantics, then the parsing should be applicative? You don't need ">>=" since you do not compute a semantical value on the left, but just the AST, which is syntax only. But then Section 3.2 shows that Printer cannot be Applicative. Indeed, the version of "pure" in the paper (see class "Syntax delta" in Section 3.4) has type "Eq a => a -> delta a", and that's different from the Applicative that we know. But one of the many "categorial" packages on hackage can express this, meanwhile? What is the meta-search-procedure to find it? - J.W.

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