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For Project Euler #1 isn't it more efficient to generate just the numbers you need? <Spoiler>
by caseyh＠istar.ca 07 May '11

07 May '11

-- Instead of this -- sumMultiples3or5 s = sum [x | x <- [3..s-1], x `mod` 3 == 0 || x `mod` 5 == 0] -- Isn't this faster sumMultiples3or5 s = sum ([x | x <- [3,6..s-1]] `merge` [x | x <- [5,10..s-1]]) merge xs [] = xs merge [] ys = ys merge txs@(x:xs) tys@(y:ys) | x < y = x : xs `merge` tys | x > y = y : txs `merge` ys | otherwise = x : xs `merge` ys

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Server hosting
by Andrew Coppin 07 May '11

07 May '11

OK, so strictly this is unrelated to Haskell as such. However, there's enough people doing webby stuff with Haskell that some of you must have wanted to run your code on a real, Internet-accessible web server. So does anybody have any suggestions on which companies offer the most favourable tools / pricing? I currently have a website, but it supports only CGI *scripts* (i.e., Perl or PHP). It does not support arbitrary CGI *binaries*, which is what I'd want for Haskell. In fact, I don't have control over the web server at all; I just put content on there. The same provider can offer me a virtual server, but at 3x the price I'm currently paying. I simply cannot afford that kind of money just for silly toy projects. What does everybody else use?

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lambdabot install error
by epsilonhalbe 07 May '11

07 May '11

hey haskellers, i'm fresh into haskell and love it. so to do faster easier haskell i wanted to install lambdabot but had to face some errors - i don't understand them at all here is some error output from zsh: http://hpaste.org/46401/bot_install_error can anyone help me - i'm working on a debian (crunchbang) y.t epsilonhalbe (ε/2)

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Manatee-0.2.1 release!
by Lazycat Manatee 07 May '11

07 May '11

Hi all, Manatee-0.2.1 release! (Detail see: http://goo.gl/MkVw http://goo.gl/PnPbq http://goo.gl/OSpz8) New features in new version: * Show welcome page when you first time use Manatee, make manatee easier to use. * Keymap helper, you just need hit Ctrl+/ or Ctrl+? if you don't know keymap. * Window layout save/restore, you play Manatee and shutdown, all window layout will restore when you next startup. * Tab position save when you switch to other tab-group, and restore tab position when you switch back. * Use new input-framework instead manatee-anything package. * Many detail improve and bug fixed. Enjoy! -- Andy

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ANN: stm-chans 1.2.0
by wren ng thornton 07 May '11

07 May '11

-------------------------------------------- -- stm-chans 1.2.0 -------------------------------------------- The stm-chans package offers a collection of channel types, similar to Control.Concurrent.STM.TChan but with additional features. -------------------------------------------- -- Changes (since 1.0.0) -------------------------------------------- * (Version 1.1.0) Added tryWriteTBChan. * (Version 1.1.0) Added tryWriteTBMChan. * Some major performance improvements in TBChan and TBMChan, thanks to Thomas DuBuisson. In particular, these improvements reduce contention between readers and writers, improving throughput by up to 2--3 times when producers and consumers are running in separate OS threads. The cost for non-parallel programs is trivial (<1% worst-case running time, per Criterion). * Added estimateFreeSlotsTBChan, freeSlotsTBChan, estimateFreeSlotsTBMChan, and freeSlotsTBMChan. These functions return either the exact number or a lower-bound on the number of free slots available before the channels will block/retry. * Some other minor optimizations and code improvements. -------------------------------------------- -- Long description -------------------------------------------- In particular stm-chans offers these types: * Control.Concurrent.STM.TBChan: Bounded FIFO channels. When the channel is full, writers will block/retry. This ensures that the writers do not get too far ahead of the readers, which helps to make sure that memory and cpu resources are used responsibly. * Control.Concurrent.STM.TMChan: Closeable FIFO channels. This is like TChan (Maybe a) but with a monotonicity guarantee that once Nothing is returned all future reads will be Nothing as well. * Control.Concurrent.STM.TBMChan: Bounded Closeable FIFO channels. This combines the capabilities of TBChan and TMChan. In addition, the stm-chans package offers a (partial) compatibility layer for some recent API improvements to the stm package (see ticket #5104 [1]). These new functions include: * tryReadTChan :: TChan a -> STM (Maybe a) A version of readTChan which does not retry. Instead it returns Nothing if no value is available. * peekTChan :: TChan a -> STM a Get the next value from the TChan without removing it, retrying if the channel is empty. * tryPeekTChan :: TChan a -> STM (Maybe a) A version of peekTChan which does not retry. Instead it returns Nothing if no value is available. [1] http://hackage.haskell.org/trac/ghc/ticket/5104 -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/stm-chans Darcs: http://community.haskell.org/~wren/stm-chans Haddock (Darcs version): http://community.haskell.org/~wren/stm-chans/dist/doc/html/stm-chans -- Live well, ~wren

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Do exist globally available hosting project services?
by Facundo Domínguez 07 May '11

07 May '11

Dear haskellers, I was reading the terms of service of the Haskell Community Server and found this statement: "Users residing in countries on the United States Office of Foreign Assets Control sanction list, including Cuba, Iran, Libya, North Korea, Sudan and Syria, may not post or access CONTENT available through OUR services." I wonder whether there is a solution for hosting projects which does not discriminate people by their place of residence. http://code.haskell.org http://www.patch-tag.com https://github.com all seem to be ruled under USA laws. Would anybody recommend an alternative? Best, Facundo

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ANN: timeplot-0.3.0 - the analyst's swiss army knife for visualizing ad-hoc log files
by Eugene Kirpichov 06 May '11

06 May '11

Hello fellow haskellers, I announce the release of timeplot-0.3.0, the "analyst's swiss army knife for visualizing ad-hoc log files". Links: * http://jkff.info/presentation/two-visualization-tools - a presentation saying what the tools are all about and giving plenty of graphical examples on cluster computing use cases. At the end of the presentation there's also a couple of slides about installation. It is a little bit outdated, it corresponds to versions just before 0.3.0. * http://hackage.haskell.org/package/timeplot * http://github.com/jkff/timeplot * The sibling tool, splot - for visualizing the activity of many concurrent processes - http://hackage.haskell.org/package/splot and http://github.com/jkff/splot . It has also gotten a couple of new features since my last announcement. The major new feature of tplot is the introduction of subplots, the <<'within' plots>>. It allows one to plot data from several sub-tracks on one track of the graph: - several line- or dot-plots - several plots of sums or cumulative sums, perhaps stacked (to see how the sub-tracks contribute to the total sum - e.g. if your log speaks about different types of overhead and you wish to see how they contribute to the total) - stacked "activity count" plot - a generalization of the previous "activity count" plot, which allows you to, given a log saying like "Machine started servicing job JOB1 ... Machine finished servicing job JOB1" etc, plot how many machines are servicing each job at any moment, in a stacked fashion - so, how loads by different jobs contribute to the whole cluster's load. The "activity frequency" plot plots the same on a relative scale. The syntax is, for example: "within[.] dots" or "within[.] acount" or even "within[.] duration cumsum stacked" etc. Note that these are of course just example use cases and the tool is universal, it is not in any sense specialized to clusters, jobs, overheads or actually even to logs. I'd like to encourage you to give it a try and look around for a use case :) If you do give the tool a try, please tell me if something goes wrong, be it an installation problem or a bug (the version is fresh released, so this is quite possible). -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

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Can't build Gtk2hs on Windows
by Andrew Coppin 06 May '11

06 May '11

Today I tried to install Gtk2hs. Big mistake! Last time I tried it, it was quite easy. Now that it uses Cabal, even on Windows you can compile this stuff from source fairly easily. It's just that you have to fiddle with environment variables to make it find stuff. However... 1. Since the move of haskell.org, the gtk2hs homepage has vanished off the face of the Earth. Is there any danger we might get this back some day? 2. http://hackage.haskell.org/trac/gtk2hs/ticket/1203 (In other words, every time you try to cabal install a GTK-related package, it fails during the register step, and you need to hand-edit Gtk2HsSetup.hs to fix the issue.) 3. http://hackage.haskell.org/trac/gtk2hs/ticket/1209 (In other words, certain GTK-related packages just plain fail to build due to undefined names or missing header files or...) In summary, it's just utterly broken. Which is very frustrating, given that not so long ago it was working really well. (I never did get Glade to work though... although it looks like that might be fixed now, if I could just get past all the other issues.)

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ANN: syntactic-0.1
by Emil Axelsson 06 May '11

06 May '11

I'm happy to announce the first release of syntactic: http://hackage.haskell.org/package/syntactic providing generic abstract syntax and utilities for embedded languages. To get an idea of what it's about, check out the tiny(!) implementation of (simplified) Feldspar in the Examples directory: http://projects.haskell.org/syntactic/Examples/MuFeldspar The library is intended to provide a growing set of utilities for embedded languages. In particular, I hope to be able to provide safe interfaces to various unsafe techniques for speeding things up. Comments, patches and clients are welcome! / Emil

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CFP: APLAS 2011, Kenting, Taiwan
by Shin-Cheng Mu 06 May '11

06 May '11

========================================================== APLAS 2011 Call For Papers Ninth Asian Symposium on Programming Languages and Systems Kenting, Taiwan, December 5--7, 2011 (co-located with CPP 2011) http://flolac.iis.sinica.edu.tw/aplas11/ ========================================================== BACKGROUND: APLAS aims at stimulating programming language research by providing a forum for the presentation of latest results and the exchange of ideas in topics concerned with programming languages and systems. APLAS is based in Asia, but is an international forum that serves the worldwide programming language community. APLAS is sponsored by the Asian Association for Foundation of Software (AAFS) founded by Asian researchers in cooperation with many researchers from Europe and the USA. The past APLAS symposiums were successfully held in Shanghai ('10), Seoul ('09), Bangalore ('08), Singapore ('07), Sydney ('06), Tsukuba ('05), Taipei ('04) and Beijing ('03) after three informal workshops. Proceedings of the past symposiums were published in Springer-Verlag's LNCS 6461, 5904, 5356, 4807, 4279, 3780, 3302, and 2895. The 2011 edition will be held at Kenting, a seaside resort in Southern Taiwan. TOPICS: The symposium is devoted to both foundational and practical issues in programming languages and systems. Papers are solicited on, but not limited to, the following topics: + semantics, logics, foundational theory; + design of languages and foundational calculi; + type systems; + compilers, interpreters, abstract machines; + program derivation and transformation; + program analysis, verification, model-checking, software security; + concurrency, constraints, domain-specific languages; + tools for programming, verification, implementation. APLAS 2011 is not limited to topics discussed in previous symposiums. Papers identifying future directions of programming and those addressing the rapid changes of the underlying computing platforms are especially welcome. Demonstration of systems and tools in the scope of APLAS are welcome to the System and Tool presentations category. Authors concerned about the appropriateness of a topic are welcome to consult with Program Chair prior to submission. IMPORTANT DATES: Abstract Deadline: June 13, 2011 Submission Deadline: June 17, 2011 (GMT) Notification: August 29, 2011 Camera-Ready: September 19, 2011 INVITED SPEAKERS: Nikolaj Bjorner, Microsoft Research Redmond Ranjit Jhala, UC San Diego Peter O'Hearn, Queen Mary U. London Sriram Rajamani, Microsoft Research India SUBMISSION INFORMATION: We solicit submissions in two categories: Regular research papers, describing original research results, including tool development and case studies, from a perspective of scientific research. Regular research papers should not exceed 16 pages in the Springer LNCS format, including bibliography and figures. They should clearly identify what has been accomplished and why it is significant. Submissions will be judged on the basis of significance, relevance, correctness, originality, and clarity. In case of lack of space, proofs, experimental results, or any information supporting the technical results of the paper could be provided as Appendix or a link to a web page. System and Tool presentations, describing systems or tools that support theory, program construction, reasoning, and/or program execution in the scope of APLAS. Unlike presentations of regular research papers, presentation of accepted papers in this category is expected to be centered around a demonstration. The paper and the demonstration should identify the novelties of the tools and use motivating examples. System and Tool papers should not exceed 8 pages in the Springer LNCS format, including bibliography and figures. Submissions will be judged based on both the papers and the systems or tools as described in the papers. It is highly desirable that the tools are available on the web. Papers should be submitted electronically via the submission web page at http://www.easychair.org/conferences/?conf=aplas2011. Acceptable formats are PostScript or PDF, viewable by Ghostview or Acrobat Reader. Submitted papers must be unpublished and not submitted for publication elsewhere. Papers must be written in English. The proceedings are planned to be published as a volume in Springer-Verlag's Lecture Notes in Computer Science series. Accepted papers must be presented at the conference. GENERAL CHAIR: Tyng-Ruey Chuang, Academia Sinica, Taiwan PROGRAM CHAIR: Hongseok Yang, Queen Mary U. London aplas2011(a)easychair.org PROGRAM COMMITTEE: Lars Birkedal (ITU, Denmark) James Brotherston (Imperial College, UK) Kung Chen (National Chengchi U., Taiwan) Wenguang Chen (Tsinghua U., China) Wei-Ngan Chin (NUS, Singapore) Javier Esparza (TUM, Germany) Xinyu Feng (USTC, China) Jerome Feret (INRIA, France) Matthew Fluet (RIT, USA) Rajiv Gupta (UC Riverside, USA) Masahito Hasegawa (Kyoto U., Japan) Radha Jagadeesan (Depaul U., USA) Naoki Kobayashi (Tohoku U., Japan) Daniel Kroning (U. Oxford, UK) Rupak Majumdar (MPI-SWS, Germany) Andrzej Murawski (U. Leicester, UK) Paulo Oliva (Queen Mary U. London, UK) Doron Peled (Bar Ilan U., Israel) Sukyoung Ryu (KAIST, Korea) Sriram Sankaranarayanan (U. Colorado, USA) Armando Solar-Lezama (MIT, USA) Sam Staton (U. Cambridge, UK) Viktor Vafeiadis (MPI-SWS, Germany) Kapil Vaswani (MSR, India) Martin Vechev (IBM, USA) Peng Wu (IBM, USA) Hongseok Yang (Queen Mary U. London, UK) Pen-Chung Yew (Academia Sinica, Taiwan) ORGANIZERS: Mike Dodds, U. Cambridge (Poster chair) Shin-Cheng Mu, Academia Sinica, Taiwan (Local arrangement chair) Noam Rinetzky, Queen Mary U. London (Publicity chair) Yih-Kuen Tsay, National Taiwan University (Finance chair)

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