April 2012 - Haskell - Haskell.org

ANN: cabal-install-0.14.0
by Andres Löh 18 Apr '12

18 Apr '12

I'm pleased to announce the long-awaited new release of cabal-install-0.14.0 If you are already using cabal-install then you can upgrade both using: $ cabal update $ cabal install Cabal cabal-install New users you can get it from: http://haskell.org/cabal/download.html For users on unix systems there is a source tarball with a bootstrap script. For users on Windows systems there is a pre-compiled cabal.exe (The Windows binary hasn't really been tested yet. Feedback welcome.) Release notes ============= cabal-install-0.14.0 -------------------- Changes since 0.10.2: * Works with ghc-7.4 * Completely new modular dependency solver (default in most cases) * Some tweaks to old topdown dependency solver * Install plans are now checked for reinstalls that break packages * Flags --constraint and --preference work for nonexisting packages * New constraint forms for source and installed packages * New constraint form for package-specific use flags * New constraint form for package-specific stanza flags * Test suite dependencies are pulled in on demand * No longer install packages on --enable-tests when tests fail * New "cabal bench" command * Various "cabal init" tweaks Future plans ------------ There will probably be another incremental 0.14.2 release in the not too distant future, followed by an 0.16.0 release that should work with ghc-7.6. Bugs and feature requests ========================= This is an excellent opportunity to make sure your favourite bug or feature request is properly described in our bug tracker: http://hackage.haskell.org/trac/hackage/ To help us guide development priorities please add yourself to the ticket's cc list and describe why that bug or feature is important to you. Credits ======= On behalf of the Cabal hackers and the community generally I'd like to thank the people who have contributed patches for this release: * Tuncer Ayaz * Max Bolingbroke * Duncan Coutts * Ben Millwood * Jens Petersen * David Terei * Johan Tibell * Thomas Tuegel * Brent Yorgey Get involved ============ If you'd like to contribute, then please: * subscribe to the cabal-devel mailing list: http://www.haskell.org/mailman/listinfo/cabal-devel * check out the information on our trac: http://hackage.haskell.org/trac/hackage/ Andres

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ANNOUNCE: haskell-src-exts-1.13.2
by Niklas Broberg 18 Apr '12

18 Apr '12

Fellow Haskelleers, I'm pleased to announce the release of haskell-src-exts-1.13.2! * On hackage: http://hackage.haskell.org/package/haskell-src-exts * Via cabal: cabal install haskell-src-exts * Darcs repo: http://code.haskell.org/haskell-src-exts This release contains only a few small tweaks and bug-fixes. Changelog: 1.13.1 --> 1.13.2 =============== * Fix the bug with the precedence of unary prefix minus. Previously it was resolved as binding more tightly than any infix operator, now it is correctly treated as having the same fixity as binary infix minus. 1.13.0 --> 1.13.1 =============== * Allow an optional semi before the closing tag of an element. This achieves a similar effect for XmlSyntax in do blocks as DoAndIfThenElse does for the if construct. No more need to indent the closing tag one step further than the opening tag. * Add a dummy 'noLoc :: SrcLoc' to L.H.E.SrcLoc, to use when generating code. It could definitely be done more elegantly, but not without inducing another major version bump, so later. * Fix a regression from 1.11.x where the parser would crash upon encountering non-simple class/data declaration heads, e.g. 'data A [a]'. Now fails with a parse error as intended. Cheers, /Niklas

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CFT -- Haskell Implementors' Workshop 2012
by Johan Tibell 17 Apr '12

17 Apr '12

Call for Talks ACM SIGPLAN Haskell Implementors' Workshop http://haskell.org/haskellwiki/HaskellImplementorsWorkshop/2012 Copenhagen, Denmark, September 14th, 2012 The workshop will be held in conjunction with ICFP 2012 http://www.icfpconference.org/icfp2012/ Important dates Proposal Deadline: 10th July 2012 Notification: 27th July 2012 Workshop: 14th September 2012 The Haskell Implementors' Workshop is to be held alongside ICFP 2012 this year in Copenhagen, Denmark. There will be no proceedings; it is an informal gathering of people involved in the design and development of Haskell implementations, tools, libraries, and supporting infrastructure. This relatively new workshop reflects the growth of the user community: there is a clear need for a well-supported tool chain for the development, distribution, deployment, and configuration of Haskell software. The aim is for this workshop to give the people involved with building the infrastructure behind this ecosystem an opportunity to bat around ideas, share experiences, and ask for feedback from fellow experts. We intend the workshop to have an informal and interactive feel, with a flexible timetable and plenty of room for ad-hoc discussion, demos, and impromptu short talks. Scope and target audience ------------------------- It is important to distinguish the Haskell Implementors' Workshop from the Haskell Symposium which is also co-located with ICFP 2012. The Haskell Symposium is for the publication of Haskell-related research. In contrast, the Haskell Implementors' Workshop will have no proceedings -- although we will aim to make talk videos, slides and presented data available with the consent of the speakers. In the Haskell Implementors' Workshop, we hope to study the underlying technology. We want to bring together anyone interested in the nitty-gritty details behind turning plain-text source code into a deployed product. Having said that, members of the wider Haskell community are more than welcome to attend the workshop -- we need your feedback to keep the Haskell ecosystem thriving. The scope covers any of the following topics. There may be some topics that people feel we've missed, so by all means submit a proposal even if it doesn't fit exactly into one of these buckets: * Compilation techniques * Language features and extensions * Type system implementation * Concurrency and parallelism: language design and implementation * Performance, optimisation and benchmarking * Virtual machines and run-time systems * Libraries and tools for development or deployment Talks ----- At this stage we would like to invite proposals from potential speakers for a relatively short talk. We are aiming for 20 minute talks with 10 minutes for questions and changeovers. We want to hear from people writing compilers, tools, or libraries, people with cool ideas for directions in which we should take the platform, proposals for new features to be implemented, and half-baked crazy ideas. Please submit a talk title and abstract of no more than 200 words to: johan.tibell(a)gmail.com We will also have a lightning talks session which will be organised on the day. These talks will be 2-10 minutes, depending on available time. Suggested topics for lightning talks are to present a single idea, a work-in-progress project, a problem to intrigue and perplex Haskell implementors, or simply to ask for feedback and collaborators. Organisers ---------- * Lennart Augustsson (Standard Chartered Bank) * Manuel M T Chakravarty (University of New South Wales) * Gregory Collins - co-chair (Google) * Simon Marlow (Microsoft Research) * David Terei (Stanford University) * Johan Tibell - co-chair (Google)

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Who should be contacted for changes to the front page of http://www.haskell.org ?
by Bernie Pope 17 Apr '12

17 Apr '12

Greetings, The front page of http://www.haskell.org/haskellwiki/Haskell is (rightly) protected. Who then should we contact if we have suggestions for changes? I apologise profusely if the answer is staring me in the face, but I couldn't seem to find it. Incidentally, and tediously, my suggestion is sadly pedantic: to change "Books & tutorials" to "Books and tutorials", to be more pleasant on the (or my) eye and to be consistent with the rest of the page. Cheers, Bernie.

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Cross-platform scripts on Linux and Windows
by Vinay Sajip 16 Apr '12

16 Apr '12

I've been given a set of .hs files which contain the shebang line #!/usr/bin/env runhaskell and I would like them to work on Windows, but none of the Windows binaries seem to be able to process them without a <script.hs>:1:1: parse error on input `#!' These files came from a Linux machine, where they run without trouble. Is there any way I can get the Windows executables to run these files? I asked on IRC and it was suggested that I change the files to literate Haskell, but I'd rather have some way of having cross-platform operation which does not involve making changes to the scripts themselves. Is there something that can be done e.g. by using particular command line options or configuration settings? Thanks & regards, Vinay Sajip

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ANNOUNCE : Juicy.Pixels 1.2.1
by Vincent Berthoux 16 Apr '12

16 Apr '12

Hello everyone, I'm pleased to announce you the new version of Juicy.Pixels, the 1.2.1, no new major features, here's the changelog : - Removed dependency on the array package. - Updated dependency list to handle latest mtl version. - Helper functions to save files without thinking about it. - Some code snippets in the API documentations GitHub : https://github.com/Twinside/Juicy.Pixels Hackage : http://hackage.haskell.org/package/JuicyPixels Regards Vincent Berthoux

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LOLA 2012: Call for Talk Proposals (deadline extended)
by Amal Ahmed 14 Apr '12

14 Apr '12

*** Submission deadline extended to April 19th *** ============================================================ *** CALL FOR TALK PROPOSALS *** LOLA 2012 Syntax and Semantics of Low Level Languages Sunday 24th June 2012, Dubrovnik, Croatia A LICS 2012-affiliated workshop http://www.ccs.neu.edu/home/amal/lola2012 ============================================================ IMPORTANT DATES Submission deadline Thursday 19th April 2012 (extended) Author notification Monday 30th April 2012 Workshop Sunday 24th June 2012 SUBMISSION LINK The submissions will be made by easychair at https://www.easychair.org/conferences/?conf=lola2012 DESCRIPTION OF THE WORKSHOP It has been understood since the late 1960s that tools and structures arising in mathematical logic and proof theory can usefully be applied to the design of high level programming languages, and to the development of reasoning principles for such languages. Yet low level languages, such as machine code, and the compilation of high level languages into a low level ones have traditionally been seen as having little or no essential connection to logic. However, a fundamental discovery of this past decade has been that low level languages are also governed by logical principles. From this key observation has emerged an active and fascinating new research area at the frontier of logic and computer science. The practically-motivated design of logics reflecting the structure of low level languages (such as heaps, registers and code pointers) and low level properties of programs (such as resource usage) goes hand in hand with the some of the most advanced contemporary researches in semantics and proof theory, including classical realizability and forcing, double orthogonality, parametricity, linear logic, game semantics, uniformity, categorical semantics, explicit substitutions, abstract machines, implicit complexity and sublinear programming. The LOLA workshop, affiliated with LICS, will bring together researchers interested in many aspects of the relationship between logic and low level languages and programs. Topics of interest include, but are not limited to: Typed assembly languages, Certified assembly programming, Certified and certifying compilation, Proof-carrying code, Program optimization, Modal logic and realizability in machine code, Realizability and double orthogonality in assembly code, Parametricity, modules and existential types, General references, Kripke models and recursive types, Continuations and concurrency, Implicit complexity, sublinear programming and Turing machines, Closures and explicit substitutions, Linear logic and separation logic, Game semantics, abstract machines and hardware synthesis, Monoidal and premonoidal categories, traces and effects. SUBMISSION INFORMATION: LOLA is an informal workshop aiming at a high degree of useful interaction amongst the participants, welcoming proposals for talks on work in progress, overviews of larger programmes, position presentations and short tutorials as well as more traditional research talks describing new results. The programme committee will select the workshop presentations from submitted proposals, which may take the form either of a short abstract or of a longer (published or unpublished) paper describing completed work. PROGRAM CO-CHAIRS: Amal Ahmed (Northeastern University) Aleksandar Nanevski (IMDEA Software) PROGRAM COMMITTEE: Cristiano Calcagno (Imperial College London and Monoidics Limited) Robert Dockins (Princeton University) Martin Hofmann (LMU Munich) Xavier Leroy (INRIA Rocquencourt) Andrzej Murawski (University of Leicester) Sungwoo Park (Pohang University of Science and Technology) Dusko Pavlovic (Royal Holloway, University of London) Andreas Rossberg (Google)

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ANNOUNCE: notcpp-0.0.1
by Ben Millwood 13 Apr '12

13 Apr '12

I'm pleased to announce my first genuinely original Hackage package: notcpp-0.0.1! http://hackage.haskell.org/package/notcpp This was inspired after someone submitted a patch to another of my packages, applicative-quoters, to improve behaviour on later GHC versions by using the new lookupValueName function where appropriate. The patch used CPP to determine if the package versions were such that lookupValueName would exist. But I never liked using CPP: it completely defeats haskell-src-exts and hence things like SourceGraph, and anyway it's not designed for Haskell and doesn't at all understand its structure, or fit with its syntax. With a little thought, I wondered if creative use of template haskell might not achieve the same goal. It turned out it did, and emboldened with this knowledge I set out to write a new package making this technique available to others. Along the way, a second technique occurred to me along the way that this could provide a hack fix for particularly nasty orphan instances; provide the class name, type, and method definitions, and my code detects if an instance exists. If so, it throws away your hard work and uses that; if not it synthesises (crudely, and probably inaccurately in some cases) an instance from your information and includes it in your code. One way or another, the instance will exist. I should emphasise that the way this is done is strange, and I have possibly hit a GHC bug or two, so I invite people to test, to -ddump-splices and make sure the package is behaving, and to let me know what they discover :) I'm off to fetch a GHC HEAD and see if it is any more co-operative. Ben Millwood (second attempt at sending this, since the first was from an address not subscribed the the list, whoops)

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Last CfP: UNIF 2012 - 26th International Workshop on Unification
by Santiago Escobar 13 Apr '12

13 Apr '12

Call for Papers UNIF 2012 The 26th International Workshop on Unification http://unif2012.cs.man.ac.uk July 1st, 2012, Manchester, UK Satellite event of IJCAR 2012 UNIF 2012 is the 26th event in a series of international meetings devoted to unification theory and its applications. UNIF 2012 is a satellite event of the the 6th International Joint Conference on Automated Reasoning (IJCAR 2012) which is part of the Alan Turing Year 2012, and collocated with The Alan Turing Centenary Conference. Previous editions of UNIF have taken place mostly in Europe, but also in USA and Japan. For more details on previous UNIF workshops, please see the UNIF homepage at <http://www.pps.jussieu.fr/~treinen/unif/>. The aim of UNIF 2012, as that of the previous meetings, is to bring together researchers interested in unification theory and related topics, to present recent (even unfinished) work, and discuss new ideas and trends in this and related fields. This includes scientific presentations, but also descriptions of applications and software using unification as a strong component. A non-exhaustive list of topics of interest includes: unification algorithms, calculi and implementations, equational unification and unification modulo theories, unification in modal, temporal and description logics, admissibility of inference rules, narrowing, matching algorithms, constraint solving, combination problems, disunification, higher-order unification, type checking and reconstruction, typed unification, complexity issues, query answering, implementation techniques and applications of unification. Submissions and Publication: Before the workshop, authors are invited to submit an extended abstract (max. 5 pages) to be formatted in LNCS style through the EasyChair submission site: https://www.easychair.org/account/signin.cgi?conf=unif2012 Accepted abstracts will be presented at the workshop and included in the preliminary proceedings, available at the workshop. We envisage publication of a special issue of a journal dedicated to UNIF after the event. Important Dates: # Submission: April 27 # Notification: May 18 # Final version: June 1 # Workshop: July 1 Programme Committee: # Franz Baader, TU Dresden, Germany # Christoph Benzmueller, Free University Berlin, Germany # Santiago Escobar, Universitat Politecnica de Valencia, Spain (co-chair) # Maribel Fernandez, King's College London, UK # Silvio Ghilardi, Universita degli Studi di Milano, Italy # Rosalie Iemhoff, Utrecht University, The Netherlands # Konstantin Korovin, University of Manchester, UK (co-chair) # Jordi Levy, IIIA - CSIC, Spain # Christopher Lynch, Clarkson University, USA # George Metcalfe, Vanderbilt University, USA # Paliath Narendran, University at Albany, USA # Vladimir Rybakov, Manchester Metropolitan University, UK (co-chair) For more information, please contact any of the three chairs Santiago Escobar, Konstantin Korovin, Vladimir Rybakov

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Haskell Weekly News: Issue 222
by Daniel Santa Cruz 12 Apr '12

12 Apr '12

Welcome to issue 222 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of April 1 to 7, 2012. Quotes of the Week * tgeeky_: "What I cannot create, I do not understand." -- Richard Feynman, on his blackboard when he died in 1988. * elliott: ... [a] is more of a control structure than a data structure. * Cale: Basically, we've known how to implement first class functions efficiently for 20 or 30 years now, and we've known about their importance to abstraction in programming since before the advent of electronic computers. There's no excuse to still be writing new programs in languages without them. * edwardk: When someone throws an exception at you, duck. * luite: I think it uses levenshtein distance (he invented this distance because nobody could spell his name correctly) * edwardk: 'hey ghc devs can you fix this thing that might or might not be a bug so we can break a huge pile of invariants in your compiler to put go faster stripes on something nobody uses? k thx' Top Reddit Stories * Tfoo, my simple Five in a Row game. Online, with server-sent events, deployed to Heroku, open source. Domain: tfoo.herokuapp.com, Score: 49, Comments: 18 On Reddit: [1] http://goo.gl/Klevh Original: [2] http://goo.gl/PtjKk * Interacting with inner-functions in GHCi [StackOverflow] Domain: stackoverflow.com, Score: 48, Comments: 12 On Reddit: [3] http://goo.gl/23l0G Original: [4] http://goo.gl/2H5kI * ANN: acme-http. 221,693.0 req/s on the PONG benchmark. Domain: groups.google.com, Score: 42, Comments: 4 On Reddit: [5] http://goo.gl/XROlu Original: [6] http://goo.gl/PuOt3 * Recent haskell-mode changes screencast Domain: youtube.com, Score: 39, Comments: 15 On Reddit: [7] http://goo.gl/JyX0s Original: [8] http://goo.gl/VWLIF * An Haskell tutorial. What do you think? Domain: yannesposito.com, Score: 39, Comments: 47 On Reddit: [9] http://goo.gl/eLiQT Original: [10] http://goo.gl/yBDnQ * Galois' Open-Source code available on github Domain: corp.galois.com, Score: 38, Comments: 3 On Reddit: [11] http://goo.gl/xoz4K Original: [12] http://goo.gl/OhlaA * Wadler’s Law Revisited Domain: comonad.com, Score: 27, Comments: 9 On Reddit: [13] http://goo.gl/8p9As Original: [14] http://goo.gl/7iB53 * With Linux supporting x32 ABI, should GHC follow suit? Domain: self.haskell, Score: 23, Comments: 6 On Reddit: [15] http://goo.gl/Nkuob Original: [16] http://goo.gl/Nkuob * cabal-meta: transcending to dependency heaven Domain: yesodweb.com, Score: 22, Comments: 27 On Reddit: [17] http://goo.gl/nsVhn Original: [18] http://goo.gl/U2cDK * [Haskell-cafe] A Modest Records Proposal Domain: haskell.org, Score: 21, Comments: 7 On Reddit: [19] http://goo.gl/MvbRq Original: [20] http://goo.gl/RgaRU Top StackOverflow Questions * What is the best way to test and interact with inner functions defined inside a toplevel function? votes: 44, answers: 1 Read on SO: [21] http://goo.gl/2H5kI * How can a Windows service application be written in Haskell? votes: 15, answers: 1 Read on SO: [22] http://goo.gl/kz8TA * What does ':..' mean in Haskell? votes: 12, answers: 2 Read on SO: [23] http://goo.gl/Whi8a * Is the whole Map copied when a new binding is inserted? votes: 10, answers: 3 Read on SO: [24] http://goo.gl/OabLu * Haskell functions left-to-right votes: 10, answers: 1 Read on SO: [25] http://goo.gl/rhCm3 * How can I avoid writing boilerplate code for functions performing pattern matching? votes: 9, answers: 3 Read on SO: [26] http://goo.gl/6cvXJ * Controlling how test data is generated in QuickCheck votes: 8, answers: 1 Read on SO: [27] http://goo.gl/BNSug * Can I get warnings about overly-restrictive type signatures? votes: 8, answers: 1 Read on SO: [28] http://goo.gl/X7PkN * Slowdown when using parallel strategies in Haskell votes: 8, answers: 1 Read on SO: [29] http://goo.gl/ghV3C * Dealing with boilerplate in Haskell votes: 7, answers: 2 Read on SO: [30] http://goo.gl/Um4Fm Until next time, Daniel Santa Cruz References 1. http://tfoo.herokuapp.com/ 2. http://www.reddit.com/r/haskell/comments/rx20z/tfoo_my_simple_five_in_a_row… 3. http://stackoverflow.com/questions/9987739/what-is-the-best-way-to-test-and… 4. http://www.reddit.com/r/haskell/comments/rr7se/interacting_with_innerfuncti… 5. https://groups.google.com/group/happs/browse_thread/thread/9b078d23b59a7374 6. http://www.reddit.com/r/haskell/comments/ro77b/ann_acmehttp_2216930_reqs_on… 7. http://www.youtube.com/watch?v=E6xIjl06Lr4 8. http://www.reddit.com/r/haskell/comments/rtctu/recent_haskellmode_changes_s… 9. http://yannesposito.com/Scratch/en/blog/Haskell-the-Hard-Way/ 10. http://www.reddit.com/r/haskell/comments/rw61r/an_haskell_tutorial_what_do_… 11. http://corp.galois.com/blog/2012/4/4/galois-open-source-projects-on-github.… 12. http://www.reddit.com/r/haskell/comments/rt8m3/galois_opensource_code_avail… 13. http://comonad.com/reader/2012/wadlers-law-revisited/ 14. http://www.reddit.com/r/haskell/comments/rpyhr/wadlers_law_revisited/ 15. http://www.reddit.com/r/haskell/comments/rpbcx/with_linux_supporting_x32_ab… 16. http://www.reddit.com/r/haskell/comments/rpbcx/with_linux_supporting_x32_ab… 17. http://www.yesodweb.com/blog/2012/04/cabal-meta 18. http://www.reddit.com/r/haskell/comments/rurn4/cabalmeta_transcending_to_de… 19. http://www.haskell.org/pipermail/haskell-cafe/2012-April/100527.html 20. http://www.reddit.com/r/haskell/comments/rnwgn/haskellcafe_a_modest_records… 21. http://stackoverflow.com/questions/9987739/what-is-the-best-way-to-test-and… 22. http://stackoverflow.com/questions/10037654/how-can-a-windows-service-appli… 23. http://stackoverflow.com/questions/9996740/what-does-mean-in-haskell 24. http://stackoverflow.com/questions/10002956/is-the-whole-map-copied-when-a-… 25. http://stackoverflow.com/questions/10003796/haskell-functions-left-to-right 26. http://stackoverflow.com/questions/10024455/how-can-i-avoid-writing-boilerp… 27. http://stackoverflow.com/questions/9977734/controlling-how-test-data-is-gen… 28. http://stackoverflow.com/questions/9986508/can-i-get-warnings-about-overly-… 29. http://stackoverflow.com/questions/10009361/slowdown-when-using-parallel-st… 30. http://stackoverflow.com/questions/9969638/dealing-with-boilerplate-in-hask…

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