April 2011 - Haskell - Haskell.org

Errata for "Pearls of Functional Algorithm Design" by Richard Bird, 2010, page 25 #Haskell
by KC 18 Apr '11

18 Apr '11

Errata for "Pearls of Functional Algorithm Design" by Richard Bird, 2010, page 25 #Haskell smallest :: (Ord a) => Int -> (Array Int a, Array Int a) -> a smallest k (xa,ya) = search k (0,m+1) (0,n+1) where (0,m) = bounds xa (0,n) = bounds ya search k (lx,rx) (ly,ry) | lx == rx = ya ! (k+ly) | ly == ry = xa ! (k+lx) | otherwise = case (xa ! mx < ya ! my, k <= mx-lx+my-ly) of (True, True) -> search k (lx,rx) (ly,my) (True, False) -> search (k-(mx-lx)-1) (mx+1,rx) (ly,ry) (False, True) -> search k (lx,mx) (ly,ry) (False, False)-> search (k-(my-ly)-1) (lx,rx) (my+1,ry) where mx = (lx+rx) `div` 2 my = (ly+ry) `div` 2 -- -- Regards, KC

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select(2) or poll(2)-like function?
by Matthias Kilian 18 Apr '11

18 Apr '11

Hi, is there something like select(2) or poll(2) available in the standard (HP) libraries? I hoogled around a little bit but didn't find anything. (Something like this will be crucial for networking stuff listening on v4 and v6 sockets at the same time) Ciao, Kili

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ANNOUNCE: floatshow-0.1 faster String representations for Double and Float
by Daniel Fischer 18 Apr '11

18 Apr '11

The Show instances for RealFloat types provided in base are very elegant, as they produce the shortest string which 'read' converts back to the original number. That, however, involves a check after each digit has been determined and arithmetic of usually fairly large Integers, which makes these Show instances rather slow. For cases where having the conversion fast is more important than having it produce elegant output, the floatshow package provides alternative conversions, which avoid the checks and reduce the occurrences of large Integers by just producing a sufficiently long output string. The speed gain can be substantial if the numbers have exponents of large absolute modulus, but for the more common case of numbers whose exponents have small absolute modulus, the difference is (although still significant for Double) too small in my opinion to seriously consider replacing the Show instances. Therefore I've put these functions into their own package. In my benchmarks, the speed gain ranges from 4x to 10x for Double and from 1.25x to 5x for Float, so the package may be a useful alternative for tasks requiring the output of many floating point numbers. Sadly, floatshow is non-portable and requires ghc >= 6.12.

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Creating a Project
by Dominic Steintiz 18 Apr '11

18 Apr '11

Hi, I am trying to create a project using http://community.haskell.org/admin/project_request.html but I am getting "Service Temporarily Unavailable". Does anyone know when it will be back on line? Thanks, Dominic.

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Summer school on Applied Functional Programming at Utrecht University; deadline for registration May 15
by S. Doaitse Swierstra 18 Apr '11

18 Apr '11

Again we will teach an "Applied Functional Programming Summer in Haskell" school this year at Utrecht University. In the previous two occasions students were all very happy with the school and we plan to repeat this success this year. The intended audience are prospective master students who have been in contact with Functional Programming, e.g. by taking a general course on programming languages, and want to learn more about Haskell and its typical programming patterns. In the previous two years we have taught an introductory part (advanced bachelor level), an advanced part (beginning master level) and a shared part for both groups. Topics covered are, besides some examples of domain specific languages, also monads, monad transformers, arrows, parser combinators and self-analysing programs, underlying principles, type inferencing, etc. Half of the course time is spent on a larger programming exercise; you can also come with a problem of your own if you want, and get help from the Utrecht University Software Technology group in finding the proper Haskell idioms, tools and libraries, for solving it. Important links: -- our own page where we supply information based on questions asked http://www.cs.uu.nl/wiki/bin/view/USCS2011/WebHome -- the poster you can print and hang somewhere (why not your office door): http://www.cs.uu.nl/wiki/pub/USCS2011/WebHome/USCSpos11.pdf -- the official summerschool site where you can register: http://www.utrechtsummerschool.nl/index.php?type=courses&code=H9 Furthermore we ask for your cooperation to bring this announcement under the attention of potential participants. Best, Doaitse Swierstra PS: apologies if you get this mail more than once

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FOPARA 2011: Extended deadline May 29th
by Ricardo Peña 18 Apr '11

18 Apr '11

*************************************************************************** * * EXTENDED CALL FOR PAPERS AND CALL FOR PARTICIPATION * * 2nd International Workshop on * Foundational and Practical Aspects of Resource Analysis (FOPARA 2011) * May 19th 2011, Madrid, SPAIN * http://dalila.sip.ucm.es/fopara11/ * *************************************************************************** SUBMISSION DATE EXTENDED!! REGISTRATION IS OPEN NOW!! Submission date has been extended --------------------------------- Full Paper extended submission deadline: April 29, 2011 Notification of acceptance (for presentation): May 1, 2011 Early Registration deadline for extended deadline papers: May 5, 2011 FOPARA workshop: May 19, 2011 Submission for formal review deadline: July 8, 2011 Notification of acceptance (for LNCS): September 16, 2011 Camera ready paper: October 7th, 2011 Invited Speaker --------------- Reinhard Wilhelm (Universitat des Saarlandes) Timing Analysis and Timing Predictability I will describe our approach to compute safe and precise upper bounds on execution times for real-time programs. The required effort and the precision of the results depends strongly on the characteristics of the execution platform. Increasing the precision and reducing the effort is easy if performance is of no concern. However, the ultimate goal is to design architectures that offer a good combination of performance and predictability. I will present an overview of existing results in this research area. Scope ----- The 2nd International Workshop on Foundational and Practical Aspects of Resource Analysis (FOPARA 2011) will be held at the Computer Science Faculty of Complutense University of Madrid. It will be co-located with the 12th International Symposium Trends in Functional Programming, TFP 2011 (http://dalila.sip.ucm.es/tfp11/) The workshop will serve as a forum for presenting original research results that are relevant to the analysis of resource (time, space, and others) consumption by computer programs. The workshop aims to bring together the researchers that work on foundational issues with the researchers that focus more on practical results. Therefore, both theoretical and practical contributions are encouraged. We also encourage papers that combine theory and practice. Topics ------ The following list of topics is non-exhaustive: * resource static analysis for embedded or/and critical systems * logical and machine-independent characterisations of complexity classes * logics closely related to complexity classes * type systems for controlling/inferring/checking complexity * semantic methods to analyse resources, including quasi- and sup-interpretations, * practical applications of resource analysis. Submissions ----------- FOPARA 2011 is a two-phase workshop. All participants are invited to submit a draft paper describing the work to be presented at the workshop. These submissions will be screened by the program committee chair to make sure they are within the scope of FOPARA and will appear in the draft proceedings distributed at the workshop. Submissions appearing in the draft proceedings are not peer-reviewed publications. After the workshop, authors will be given the opportunity to incorporate the feedback from discussions at the workshop and will be invited to submit a revised full article for the formal review process. These revised submissions will be reviewed by the program committee using prevailing academic standards to select the best articles that will appear in the formal proceedings. All contributions must be written in English, conform to the Springer LNCS series format and not exceed 16 pages. The draft proceedings will appear as a technical report of the Computer Science Department of Complutense University of Madrid. The papers selected after the reviewing process will be published as a volume of the Springer LNCS series. Program Committee ----------------- . Puri Arenas (Complutense University of Madrid, ES) . David Aspinall (University of Edinburgh, UK) . David Cachera (IRISA/École normale supérieure de Cachan, FR) . Marko van Eekelen (Radboud University Nijmegen and Open University, NL) . Kevin Hammond (University of St. Andrews, UK) . Martin Hofmann (LMU, Munich, DE) . Tamás Kozsik (Eötvös Loránd University of Budapest, HU) . Hans-Wolfgang Loidl (Heriot-Watt, Edinburgh, UK) . Jean-Yves Marion (Loria, Nancy, FR) . Simone Martini (University of Bologna, IT) . Ricardo Pe~na (PC Chair) (Complutense University of Madrid, ES) . Simona Ronchi della Rocca (University of Turin, IT) . Olha Shkaravska (Radboud University, NL) Sponsors -------- . Computer Science Faculty, Complutense University of Madrid . Spanish Ministry of Science and Innovation

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Announcing AusHac 2011 - The second annual Australian Haskell Hackathon (July 8-10)
by Alex Mason 17 Apr '11

17 Apr '11

Attention all Australasian Haskellers! After last year’s fantastic turnout for the first Australian Haskell Hackathon - AusHac 2010 - we’ve decided to organise another. As it’s rather boring to have a Hackathon with only two people, we encourage and welcome anyone interested in Haskell in Australia, New Zealand and surrounding areas (or further afield if you want!) to come and join us. Last year we had more than 25 Haskellers come from Brisbane, Canberra, Melbourne, Sydney and even two from as far away as New Zealand. AusHac 2011 will be held from Friday July 8th until Sunday July 10th, again at UNSW’s Computer Science building in Sydney. There’s no need to come for the entire weekend, just for whenever you’re able to. Last year, people worked on several projects including: • Accelerate: a high performance library for array computations using various backends (CUDA, LLVM, etc.) being written at UNSW. • Leksah: the Haskell IDE written in Haskell • DDC: the compiler for the Haskell-like language Disciple, which has strict evaluation by default, region, effect and closure typing and other interesting language features. • Hubris: the Haskell/Ruby bridge for calling Haskell from Ruby and vice-versa. • haskell-mpi: bindings to MPI, the message passing interface used frequently on high performance super-computers to allow programs to run on many nodes in parallel with easy communication. • There was even some work on LLVM to produce HTML output showing register allocations (as an aid to those writing new code generators etc.), which has now been included upstream. This work did not use Haskell, but it did happen at AusHac 2010. • And much more! This is a great chance to collaborate with others and get feedback on your work, while having heaps of fun and meeting other Haskellers, to verify they do actually exist! And don’t worry if you can’t think of a project to work on; just come along and pitch in with whatever strikes your fancy! If you’re interested in coming and have a project you’d like to work on, check out the wikipage http://www.haskell.org/haskellwiki/AusHac2011 where you can add your project ideas, or just take a look and see what others will be working on that you can help out with. People of all skill levels are welcome, from complete beginners to Oleg-level sage masters. We’re more than happy to help you learn Haskell if you’re just starting out or help you solve that little niggly bit in your code. If you’re interested in coming along, fill out our registration form http://axman6.wufoo.com/forms/aushac-2011-sign-up/. Registration is required so we know numbers and for you to get access to the university Wifi. Even if you’re not sure, fill it in to express your interest, obligation free. We’d rather know we have room for too many people than not enough. So come along! And if for some reason you don’t enjoy yourself, registration comes with a money-back guarantee! Hope to see you there, -- Alex Mason and Ivan Miljenovic, AusHac organisers P.S: If you have received this email directly, it is because you have shown previous interest in AusHac by signing up via the previous signup. If you do not wish to receive any more email regarding AusHac, please email me (axman6(a)gmail.com) and I'll be sure to take you off the list of interested people.

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ANNOUNCE: acid-state-0.3
by Lemmih 16 Apr '11

16 Apr '11

Greetings, With acid-state-0.3, you can use regular Haskell data structures without worrying about data loss or durability. Your state will simply always be available to you even after software crashes or power outages. For examples of how to use the library, see: http://mirror.seize.it/acid-state/examples/ http://hackage.haskell.org/package/acid-state http://acid-state.seize.it/ -- Cheers, Lemmih

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Haskell Platform 2011.2.0.1 now available
by Don Stewart 16 Apr '11

16 Apr '11

We're pleased to announce the 2011.2.0.1 release of the Haskell Platform: a single, standard Haskell distribution for everyone. Download the Haskell Platform 2011.2.0.1: http://haskell.org/platform/ This release adds support for GHC 7.0.3, and significant improvements for Mac OS X users. The specification, along with installers (including Windows, Mac and Unix installers for a full Haskell environment) are available. The Haskell Platform is a single, standard Haskell distribution for every system, in the form of a blessed library and tool suite for Haskell distilled from the thousands of libraries on Hackage, along with installers for a wide variety of systems. It saves developers work picking and choosing the best Haskell libraries and tools to use for a task. When you install the Haskell Platform, you get the latest stable compiler, an expanded set of core libraries, additional development tools, and cabal-install – so you can download anything else you need from Hackage. This release ships with GHC 7.0.3. What you get is specified here: http://hackage.haskell.org/platform/contents.html Thanks! -- The Platform Infrastructure Team P.S. a big thanks to Mark Lentczner and Mikhail Glushenkov who built the Mac and Windows installers!

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Haskell Weekly News: Issue 177
by Daniel Santa Cruz 14 Apr '11

14 Apr '11

Welcome to issue 177 of the HWN, a newsletter covering developments in the [1]Haskell community. This release covers the week of April 3 to 9, 2011. You can find a HTML rendition of this issue at: http://bit.ly/hR2sMB Announcements Brent Yorgey [2]sent out a call for contributions for the second edition of Typeclassopedia. Roel van Dijk started what became a popular[3]thread on the mailing list about encodings of Haskell source files. What would you like to see here? I have gotten mixed feedback on what constitutes interesting items for the "announcements" section of the mailing list. Some have pointed out that package announcements tend to be noisy and not all that interesting to the community at large, or that have a bias towards only pointing out packages where the maintainer decides to send an email to the mailing list. What do *you* think? How about the "calls for papers"? Do those catch your attention? Let me hear what you think. Quotes of the Week * ion: Itâs a well-known historical fact cave men writing Haskell hated the ASCII pseudoglyphs. * shapr: I persuaded academics to show up and hang out. [...] I told the academics that there were academics worth chatting with on #haskell :-) * pjscott: If you really want to see something ridiculous, try looking at the auto-generated library documentation for anything involving regular expressions. The type declarations in Text.Regex.TDFA are like something H. P. Lovecraft might write about. * monochrom: the road to haskell is paved with good abstractions Top Reddit Stories * Typeclassopedia second edition: call for contributions From (byorgey.wordpress.com) scored 53 with 1 comments. Read on [4]reddit. Read the [5]original post. * High-Performance Web Applications In Haskell : Gregory Collins : QCon London :: PDF From (qconlondon.com) scored 45 with 8 comments. Read on [6]reddit. Read the [7]original post. * Haskell For the Cloud (new paper by Jeff Epstein, Andrew Black, and and Simon Peyton Jones) From (research.microsoft.com) scored 41 with 23 comments. Read on [8]reddit. Read the [9]original post. * Yhc is dead !? From (yhc06.blogspot.com) scored 32 with 27 comments. Read on [10]reddit. Read the [11]original post. * What is a functional language? :: Robert Harper From (existentialtype.wordpress.com) scored 29 with 35 comments. Read on [12]reddit. Read the [13]original post. * Functions are values From (existentialtype.wordpress.com) scored 27 with 16 comments. Read on [14]reddit. Read the [15]original post. * Understanding practical API design, static typing and functional programming. From (blog.tmorris.net) scored 27 with 2 comments. Read on [16]reddit. Read the [17]original post. * Platform Robots in Nikki and the Robots: a Haskell platform game From (joyridelabs.de), scored 22 with 3 comments. Read on [18]reddit. Read the [19]original post. * A Model for Denotative Continuous-Time Programming (AKA: FRP) From (creativelad.wordpress.com) scored 21 with 1 comments. Read on [20]reddit. Read the [21]original post. * Type Kata: Local data type From (blog.ezyang.com) scored 19 with 3 comments. Read on [22]reddit. Read the [23]original post. Top StackOverflow Questions * [24]Difference between State, ST, IORef, and MVar votes: 16, answers: 3 * [25]Duality approaches in functional programming votes: 11, answers: 1 * [26]What are the main differences of language features between Haskell and the functional part of F#? [closed] votes: 9, answers: 5 * [27]Using the Maybe Monad in "reverse" in Haskell votes: 9, answers: 3 * [28]How to reason about space complexity in Haskell votes: 8, answers: 1 About the Haskell Weekly News To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. I'm in dire need of finding good "quotes of the week". If you happen to come across any, please don't hesitate to send it along. Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.general/18636 3. http://article.gmane.org/gmane.comp.lang.haskell.cafe/87815 4. http://www.reddit.com/r/haskell/comments/ghs1x/typeclassopedia_second_editi… 5. http://byorgey.wordpress.com/2011/04/03/call-for-contributions-second-editi… 6. http://www.reddit.com/r/haskell/comments/gj7ud/highperformance_web_applicat… 7. http://qconlondon.com/dl/qcon-london-2011/slides/GregoryCollins_HighPerform… 8. http://www.reddit.com/r/haskell/comments/gjb52/haskell_for_the_cloud_new_pa… 9. http://research.microsoft.com/en-us/um/people/simonpj/papers/parallel/ 10. http://www.reddit.com/r/haskell/comments/ghtlf/yhc_is_dead/ 11. http://yhc06.blogspot.com/2011/04/yhc-is-dead.html 12. http://www.reddit.com/r/haskell/comments/gk1tp/what_is_a_functional_languag… 13. http://existentialtype.wordpress.com/2011/03/16/what-is-a-functional-langua… 14. http://www.reddit.com/r/haskell/comments/ghdvn/functions_are_values/ 15. http://existentialtype.wordpress.com/2011/04/02/functions-are-values/ 16. http://www.reddit.com/r/haskell/comments/gir70/understanding_practical_api_… 17. http://blog.tmorris.net/understanding-practical-api-design-static-typing-an… 18. http://www.reddit.com/r/haskell/comments/ghs81/platform_robots_in_nikki_and… 19. http://joyridelabs.de/blog/?p=612 20. http://www.reddit.com/r/haskell/comments/ghrmv/a_model_for_denotative_conti… 21. http://creativelad.wordpress.com/2011/04/03/dctp-model/ 22. http://www.reddit.com/r/haskell/comments/gk1w4/type_kata_local_data_type/ 23. http://blog.ezyang.com/2011/04/type-kata-local-data-type/ 24. http://stackoverflow.com/questions/5545517/difference-between-state-st-iore… 25. http://stackoverflow.com/questions/5557810/duality-approaches-in-functional… 26. http://stackoverflow.com/questions/5541487/what-are-the-main-differences-of… 27. http://stackoverflow.com/questions/5606228/using-the-maybe-monad-in-reverse… 28. http://stackoverflow.com/questions/5552433/how-to-reason-about-space-comple…

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