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Aeson js question
by hc＠j4.pe 14 Nov '13

14 Nov '13

Hello everyone, I'd use aeson to parse JSON. I did much of the translation JSon in Haskell data but I'm stuck on one point. Suppose I have a JSon object that is in this form: {\"Ports\":{\"22/tcp\":[{\"HostIp\":\"0.0.0.0\",\"HostPort\":\"49154\"}],\"80/tcp\":[{\"HostIp\":\"0.0.0.0\",\"HostPort\":\"49155\"}]} I do not know how to "bind" the key name and value knowing that the key changes name "randomly". Example with port 21 and port 8888: {\"Ports\":{\"21/tcp\":[{\"HostIp\":\"0.0.0.0\",\"HostPort\":\"49154\"}],\"8888/tcp\":[{\"HostIp\":\"0.0.0.0\",\"HostPort\":\"49155\"}]}} All code : http://lpaste.net/95607 Thank you for your help.

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ANNOUNCE: Haskell Communities and Activities Report (25th ed., November 2013)
by Janis Voigtlaender 14 Nov '13

14 Nov '13

On behalf of all the contributors, we are pleased to announce that the Haskell Communities and Activities Report (25th edition, November 2013) is now available, in PDF and HTML formats: http://haskell.org/communities/11-2013/report.pdf http://haskell.org/communities/11-2013/html/report.html Many thanks go to all the people that contributed to this report, both directly, by sending in descriptions, and indirectly, by doing all the interesting things that are reported. We hope you will find it as interesting a read as we did. If you have not encountered the Haskell Communities and Activities Reports before, you may like to know that the first of these reports was published in November 2001. Their goal is to improve the communication between the increasingly diverse groups, projects, and individuals working on, with, or inspired by Haskell. The idea behind these reports is simple: Every six months, a call goes out to all of you enjoying Haskell to contribute brief summaries of your own area of work. Many of you respond (eagerly, unprompted, and sometimes in time for the actual deadline) to the call. The editors collect all the contributions into a single report and feed that back to the community. When we try for the next update, six months from now, you might want to report on your own work, project, research area or group as well. So, please put the following into your diaries now: ======================================== End of April 2014: target deadline for contributions to the May 2014 edition of the HC&A Report ======================================== Unfortunately, many Haskellers working on interesting projects are so busy with their work that they seem to have lost the time to follow the Haskell related mailing lists and newsgroups, and have trouble even finding time to report on their work. If you are a member, user or friend of a project so burdened, please find someone willing to make time to report and ask them to "register" with the editors for a simple e-mail reminder in October (you could point us to them as well, and we can then politely ask if they want to contribute, but it might work better if you do the initial asking). Of course, they will still have to find the ten to fifteen minutes to draw up their report, but maybe we can increase our coverage of all that is going on in the community. Feel free to circulate this announcement further in order to reach people who might otherwise not see it. Enjoy! Mihai Maruseac and Janis Voigtlaender <hcar at haskell.org>

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off-topic question: why invent new Haskell-like compile-to-js functional languages when we have awesome js_of_ocaml ?
by Ömer Sinan Ağacan 14 Nov '13

14 Nov '13

Hi all, Sorry for off-topic question, I'm asking this question here because as Haskell community we invent lots of new Haskell-like(sometimes a subset of Haskell like Fay, sometimes different languages with Haskell syntax and Haskell-like features like Elm and recent language with row polymorphic records -- I don't remember it's name) languages. What I'm wondering is that js_of_ocaml project looks like solving all problems we have. It's supports 100% of OCaml(it translates OCaml bytecode), and OCaml is arguably better than all languages we invented(awesome module system, records, strict by default, all OCaml libraries(except FFI ones) work, like functional data structures, parser generators etc.) (I'm assuming we won't have JS backend for GHC anytime soon) So in short, I don't understand why use Haskell like compile-to-js languages instead of js_of_ocaml (other than learning purposes -- JS may be a nice high-level target language to practice writing compilers etc.) Please note that I'm not using any compile-to-js languages in my work, so I may not be able to make a fair comparison, but to me all other compile-to-js langauges look worse after seeing js_of_ocaml. Of course, if I had a JS backend for GHC(which would mean compiling Haskell to JS with all extensions) it would be best solution, but for now I think js_of_ocaml is superior to all other solutions. I'm wondering your opinions about this. Thanks, --- Ömer Sinan Ağacan http://osa1.net

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Best practices for Arrows?
by Tom Ellis 13 Nov '13

13 Nov '13

I feel I may be doing a lot of programming with Arrows in the near future. Currently I'm delighted that Arrow notation[1] exists. It makes using Arrows much less painful. Are there any best-practices I should be aware of with Arrows? Or is it just a case of getting on with it? Tom 1. http://www.haskell.org/ghc/docs/latest/html/users_guide/arrow-notation.html

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Haskell Weekly News: Issue 286
by Daniel Santa Cruz 13 Nov '13

13 Nov '13

Welcome to issue 286 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the weeks of November 03 to 09, 2013. Quotes of the Week * edwardk: (->) is syntax, sadly. * chrisdone: my brother was killed by an IO monad hpc: i guess it started as an evaluation, but ended up as an execution... * mauke: no, haskell doesn't support trees * un1xguy: first web server was written in php... Top Reddit Stories * Haskell, the Language Most Likely to Change the Way you Think About Programming Domain: m.huffpost.com, Score: 54, Comments: 71 On Reddit: [1] http://goo.gl/E0dfbl Original: [2] http://goo.gl/1CGVmK * Announcing 24 Days of Hackage 2013 - I need your help! Domain: ocharles.org.uk, Score: 53, Comments: 45 On Reddit: [3] http://goo.gl/7RupOj Original: [4] http://goo.gl/6Uog4B * Pyret: New teaching language from makers of Racket with ADTs and pattern matching Domain: pyret.org, Score: 47, Comments: 25 On Reddit: [5] http://goo.gl/Xeyyyh Original: [6] http://goo.gl/GJmYgI * haskintex: Write and run Haskell within LaTeX Domain: daniel-diaz.github.io, Score: 42, Comments: 14 On Reddit: [7] http://goo.gl/1UTbdL Original: [8] http://goo.gl/2DbE5I * Haskell.org SSL rollout Domain: hackage.haskell.org, Score: 41, Comments: 9 On Reddit: [9] http://goo.gl/2DvgLX Original: [10] http://goo.gl/M0QwMh * Why Lists? Domain: self.haskell, Score: 36, Comments: 54 On Reddit: [11] http://goo.gl/Y2ma9V Original: [12] http://goo.gl/Y2ma9V * Frege: a JVM pure functional programming language in the spirit of Haskell Domain: github.com, Score: 36, Comments: 22 On Reddit: [13] http://goo.gl/pyaB8s Original: [14] http://goo.gl/kJWFg * Switching from imperative to functional programming with games in Elm (xpost from /r/programming) Domain: github.com, Score: 35, Comments: 11 On Reddit: [15] http://goo.gl/CbsMhS Original: [16] http://goo.gl/0MpQJ0 * FP Complete is hiring a Ruby expert Haskeller. Help bring Haskell to Rubyists! Domain: self.haskell, Score: 34, Comments: 26 On Reddit: [17] http://goo.gl/eb6G1s Original: [18] http://goo.gl/eb6G1s * plaimi’s introduction to Haskell for the Haskell-curious game programmer [PDF] Domain: secure.plaimi.net, Score: 31, Comments: 21 On Reddit: [19] http://goo.gl/khkU80 Original: [20] http://goo.gl/ZgRzkn * The F# Computation Expression Zoo (Why "computation expressions" are not just an "enterprise-y monad") Domain: tomasp.net, Score: 31, Comments: 18 On Reddit: [21] http://goo.gl/qnbrNx Original: [22] http://goo.gl/ErKmeU * Try PureScript Domain: tryps.functorial.com, Score: 30, Comments: 13 On Reddit: [23] http://goo.gl/mOJCvG Original: [24] http://goo.gl/aujnyl * Internship at Facebook London working on Haxl Domain: haskell.org, Score: 30, Comments: 4 On Reddit: [25] http://goo.gl/pHjgFp Original: [26] http://goo.gl/3qrzyR * Soostone is hiring in Turkey Domain: haskell.org, Score: 29, Comments: 15 On Reddit: [27] http://goo.gl/juSJLL Original: [28] http://goo.gl/IpYTkJ * Mind-bending behavior for deserialization in Haskell Domain: justinleitgeb.com, Score: 25, Comments: 75 On Reddit: [29] http://goo.gl/4BnEVn Original: [30] http://goo.gl/wTC06g * Hudak and Jones - An Experiment in Software Prototyping Productivity - 1994 [PDF] Domain: cs.yale.edu, Score: 24, Comments: 9 On Reddit: [31] http://goo.gl/krp66H Original: [32] http://goo.gl/qK6H98 * Webcast: Designing Domain Specific Languages with Haskell - Michael Snoyman - 2012-11-14 Domain: oreillynet.com, Score: 23, Comments: 0 On Reddit: [33] http://goo.gl/liqoge Original: [34] http://goo.gl/X7N0eN * Code review request: Wikipedia API for Haskell Domain: self.haskell, Score: 23, Comments: 25 On Reddit: [35] http://goo.gl/VgPCpC Original: [36] http://goo.gl/VgPCpC * transliterate: A korean transliteration library targeting GHC, Fay, and JS Domain: github.com, Score: 21, Comments: 16 On Reddit: [37] http://goo.gl/oYrL6c Original: [38] http://goo.gl/OAZ1z9 * lens-family 1.0.0 Domain: comments.gmane.org, Score: 20, Comments: 5 On Reddit: [39] http://goo.gl/H1HFyZ Original: [40] http://goo.gl/oAAd6Z * Gershom Bazerman, NYC Haskell Meetup Organizer, interviewed for your great learning Domain: rogueleaderr.com, Score: 20, Comments: 0 On Reddit: [41] http://goo.gl/unTdeJ Original: [42] http://goo.gl/0hJ1DL Top StackOverflow Questions * “Eta reduce” is not always held in Haskell? votes: 11, answers: 1 Read on SO: [43] http://goo.gl/G0NZPp * Data Constructor promotion in GHC-7.6 votes: 10, answers: 0 Read on SO: [44] http://goo.gl/huK32T * best way to check arguments of a function in haskell votes: 9, answers: 1 Read on SO: [45] http://goo.gl/Cz5VDs * Processing a very large text file with lazy Texts and ByteStrings votes: 8, answers: 1 Read on SO: [46] http://goo.gl/eMtxDx * Style vs Performance Using Vectors votes: 8, answers: 1 Read on SO: [47] http://goo.gl/gm9o08 * Monad with no wrapped value? votes: 8, answers: 4 Read on SO: [48] http://goo.gl/XPBwQd * Is it safe to reuse a conduit? votes: 7, answers: 1 Read on SO: [49] http://goo.gl/QTepyV * Haskell Repa stencil hacks votes: 6, answers: 1 Read on SO: [50] http://goo.gl/2vEqVg * Are Functor instances unique? votes: 6, answers: 1 Read on SO: [51] http://goo.gl/EHm4yq Until next time, [52]+Daniel Santa Cruz References 1. http://m.huffpost.com/us/entry/4242119 2. http://www.reddit.com/r/haskell/comments/1q93r2/haskell_the_language_most_l… 3. http://ocharles.org.uk/blog/posts/2013-11-06-24-days-of-hackage-2013.html 4. http://www.reddit.com/r/haskell/comments/1q1sg1/announcing_24_days_of_hacka… 5. http://www.pyret.org/index.html 6. http://www.reddit.com/r/haskell/comments/1q8wv5/pyret_new_teaching_language… 7. http://daniel-diaz.github.io/projects/haskintex 8. http://www.reddit.com/r/haskell/comments/1pwcd7/haskintex_write_and_run_has… 9. https://hackage.haskell.org/ 10. http://www.reddit.com/r/haskell/comments/1q1039/haskellorg_ssl_rollout/ 11. http://www.reddit.com/r/haskell/comments/1q0jsj/why_lists/ 12. http://www.reddit.com/r/haskell/comments/1q0jsj/why_lists/ 13. https://github.com/Frege/frege 14. http://www.reddit.com/r/haskell/comments/1q3r8v/frege_a_jvm_pure_functional… 15. https://github.com/Dobiasd/elm-articles/blob/master/switching_from_imperati… 16. http://www.reddit.com/r/haskell/comments/1q5s14/switching_from_imperative_t… 17. http://www.reddit.com/r/haskell/comments/1pv6ua/fp_complete_is_hiring_a_rub… 18. http://www.reddit.com/r/haskell/comments/1pv6ua/fp_complete_is_hiring_a_rub… 19. https://secure.plaimi.net/~alexander/tmp/main.pdf 20. http://www.reddit.com/r/haskell/comments/1q1b9f/plaimis_introduction_to_has… 21. http://tomasp.net/blog/2013/computation-zoo-padl/index.html 22. http://www.reddit.com/r/haskell/comments/1q6o2a/the_f_computation_expressio… 23. http://tryps.functorial.com/ 24. http://www.reddit.com/r/haskell/comments/1pu02e/try_purescript/ 25. http://www.haskell.org/pipermail/haskell/2013-November/023977.html 26. http://www.reddit.com/r/haskell/comments/1pvggf/internship_at_facebook_lond… 27. http://www.haskell.org/pipermail/haskell-cafe/2013-November/111295.html 28. http://www.reddit.com/r/haskell/comments/1pyfor/soostone_is_hiring_in_turke… 29. http://justinleitgeb.com/haskell/mind-bending-behavior-for-deserialization-… 30. http://www.reddit.com/r/haskell/comments/1q4r3b/mindbending_behavior_for_de… 31. http://www.cs.yale.edu/publications/techreports/tr1049.pdf 32. http://www.reddit.com/r/haskell/comments/1pxvbk/hudak_and_jones_an_experime… 33. http://oreillynet.com/pub/e/2400 34. http://www.reddit.com/r/haskell/comments/1pzre6/webcast_designing_domain_sp… 35. http://www.reddit.com/r/haskell/comments/1pzymv/code_review_request_wikiped… 36. http://www.reddit.com/r/haskell/comments/1pzymv/code_review_request_wikiped… 37. https://github.com/bergmark/transliterate 38. http://www.reddit.com/r/haskell/comments/1q367s/transliterate_a_korean_tran… 39. http://comments.gmane.org/gmane.comp.lang.haskell.cafe/107972 40. http://www.reddit.com/r/haskell/comments/1ps3d7/lensfamily_100/ 41. http://rogueleaderr.com/post/66018558718/a-interview-4-gershom-bazerman-org… 42. http://www.reddit.com/r/haskell/comments/1pwkey/gershom_bazerman_nyc_haskel… 43. http://stackoverflow.com/questions/19758828/eta-reduce-is-not-always-held-i… 44. http://stackoverflow.com/questions/19875636/data-constructor-promotion-in-g… 45. http://stackoverflow.com/questions/19869902/best-way-to-check-arguments-of-… 46. http://stackoverflow.com/questions/19779559/processing-a-very-large-text-fi… 47. http://stackoverflow.com/questions/19803949/style-vs-performance-using-vect… 48. http://stackoverflow.com/questions/19884548/monad-with-no-wrapped-value 49. http://stackoverflow.com/questions/19793824/is-it-safe-to-reuse-a-conduit 50. http://stackoverflow.com/questions/19749343/haskell-repa-stencil-hacks 51. http://stackoverflow.com/questions/19774904/are-functor-instances-unique 52. https://plus.google.com/105107667630152149014/about

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Fake Conferences CSCI and WORLDCOMP of Hamid Arabnia
by abbasakbar＠hushmail.com 12 Nov '13

12 Nov '13

Fake Conferences CSCI and WORLDCOMP of Hamid Arabnia Hamid Arabnia from University of Georgia is well known for his fake WORLDCOMP conferences https://sites.google.com/site/worlddump1 or https://sites.google.com/site/dumpconf Hamid Arabnia understood that he cannot deceive researchers anymore using his WORLDCOMP. Hamid Arabnia (Guru of Fake Conferences and champion of academic scam) has recently started 2014 International Conference on Computational Science and Computational Intelligence (CSCI'14) http://www.americancse.org to deceive researchers further. CSCI'14 is started under the title of “American Council on Science and Education” which is a dummy corporation (does not exist anywhere in the world). Hamid Arabnia buried his name in the list of names of other innocent steering and program committee members of CSCI’14 to avoid any special attention. He knows that if his name is given any special attention then researchers immediately know that the conference is fake due to his “track record” with WORLDCOMP. Hamid Arabnia (the money hungry beast) spoiled the reputations and careers of many authors and committee members involved in his infamous WORLDCOMP for more than a decade and he is now ready to do the same using CSCI. Interestingly, CSCI is scheduled to be held at the same venue where WORLDCOMP was held until 2012. Hamid Arabnia claimed that CSCI proceedings will be published by IEEE but no one knows if IEEE really publishes. Many scholars have already sent emails to IEEE protesting for the unethical behavior of Hamid Arabnia and for the new series of his bogus conferences CSCI. CSCI paper submission deadline will be extended multiple times as usual. Do not spoil your resume by submitting your papers in this bogus conference CSCI which will not be held beyond 2014. Sincerely, Many researchers cheated by Hamid Arabnia conferences

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Things stopping pure Haskell code from having a cross-platform single semantics?
by Ryan Newton 12 Nov '13

12 Nov '13

Haskell isn't like Java byte code in having a single semantics for a program irrespective of where it is run. In particular, "Int" has a platform-defined width -- so the same (pure) code can yield different answers on different machines. numCapabilities was also a "leak" of platform information, which did not require IO. But, happily, now it does not appear in the [Trustworthy] module, Control.Concurrent. Ok, what else? What other holes are there that allow my pure functions to change their answer on different machines? I'm making a list of these in a paper and I want to make sure I give a full account. Thanks, -Ryan

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Re: [Haskell-cafe] Things stopping pure Haskell code
by Doug McIlroy 12 Nov '13

12 Nov '13

> What other holes are there that allow my pure functions to > change their answer on different machines? Floating point poses potential surprises. Library functions required by Haskell, but obtained from outside, can differ. IEEE FP modes may not be consistently set across all or even consistently at all times in one system if control ever leaaves Haskell code. Haskell's second-rate IO conversion functions cry out for replacement. I can imagine them being replaced in installations that really care about floating-point. Doug McIlroy

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Re: [Haskell-cafe] off-topic question: why invent new Haskell-like compile-to-js functional languages when we have awesome js_of_ocaml ?
by Hans Höglund 12 Nov '13

12 Nov '13

It is actually confirmed that GHCJS will go into an official GHC release? I have not been able to find that information on the GHC tracker. I have tried GHCJS, Haste and the UHC-JS in the past and found Haste the most easy to install and use. As far as I know, GHCJS and Haste are the only compilers to support all GHC extensions. Of course, this actualizes that old question of whether pervasive use of GHC-only extensions is A Good Thing... yet still I keep finding {-# LANGUAGE DeriveTraversable, ViewPatterns, TypeFamilies … #-} on top of my source files. Regards, Hans On Mon, Nov 11, 2013 at 2:37 PM, Brandon Allbery <allbery.b(a)gmail.com>wrote: > On Mon, Nov 11, 2013 at 2:32 PM, ?mer Sinan A?acan <omeragacan(a)gmail.com>wrote: > >> I'm aware of this, but when I first tried it a few months ago, it was >> not easy to use at all. Is it changed now? >> > > The biggest bump in usability will come from it not being just in HEAD > with everything about building it that that implies. (next release of GHC > will have it) > > -- > brandon s allbery kf8nh sine nomine > associates > allbery.b(a)gmail.com > ballbery(a)sinenomine.net > unix, openafs, kerberos, infrastructure, xmonad > http://sinenomine.net > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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Looking for feedback on my Haskell game programming paper
by Alexander Berntsen 12 Nov '13

12 Nov '13

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Someone suggested I posted this here: <https://secure.plaimi.net/~alexander/tmp/main.pdf>. "This" being an informal introduction to game programming in Haskell, aimed at game programmers used to C or C-likes. I and a fellow student originally wrote it for a class, but someone (someone else than the first someone) found the URL and posted it on Reddit[0], and various other people have read it as well -- so we already have some feedback to go on. But we welcome more feedback. It has yet to be shared outside of the Haskell community, as I would like to polish it first, and reach a 1.0 version. (Hopefully this week!) The game presented in the paper is far from finished. We aim towards a full-blown but small game. It should have multi-player, AI, networking, somewhat complicated physics, control handling, menus, a graphics system, and so on and so forth. Basically it should cover "everything", but still be small enough to serve as an example. Contributions to the game itself would be also be greatly appreciated. Its source is available on GitHub[1]. [0] <http://www.reddit.com/r/haskell/comments/1q1b9f/plaimis_introduction_to_has…> [1] <http://www.reddit.com/r/haskell/comments/1q1b9f/plaimis_introduction_to_has…> - -- Alexander alexander(a)plaimi.net http://plaimi.net/~alexander -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iF4EAREIAAYFAlKBa34ACgkQRtClrXBQc7UDGgEAtTF83DTlLM8eR68hGhgJTxj3 1sygYsqNQae3Zm5KbMcA/RfwyqyWzBgOOyeuI0JpSToWuh1ex2ILFcPdjX5nR6X7 =f0mJ -----END PGP SIGNATURE-----

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Quickcheck generator help
by Graham Berks 12 Nov '13

12 Nov '13

Hi, have the following type data BinomialHeap a = EmptyHeap | Node a Int (BinomialHeap a) and wanted to create a test generator with type ‘a’ as an Int for example hence had newtype BinominalHeapInt = BinominalHeap Int deriving (Eq, Show) But struggling to get the generator correct, currently have instance Arbitrary BinominalHeapInt where arbitrary = sized heap' where heap' 0 = return EmptyHeap heap' n | n>0 = oneof [return EmptyHeap, liftM3 Node arbitrary arbitrary subnode] where subnode = heap' (n `div` 2) But it complains Expected type: Int -> Gen BinominalHeapInt Actual type: Int -> Gen (BinomialHeap a1) in sized heap’ Any pointers ? Thanks

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New: Haskell meeting in Regensburg, 2013-11-12, 20:00
by Andres Löh 11 Nov '13

11 Nov '13

Hi. There's a new monthly Haskell meeting in Regensburg, Bavaria, Germany. Tomorrow will be our third meeting, and the first one with a Haskell talk: Tuesday, 12 November 2013 20:00 Plan 9, Werftstraße 15, 93059 Regensburg There'll be a short presentation by Martin Ruderer on how to solve problems such as the n-queens problem in Haskell. In addition, there's time for informal discussions and drinks. Everyone who's interested in Haskell is welcome. No actual knowledge of Haskell is expected or required. We'll speak German and/or English, depending on who's going to be there. If you'd like to get updates about future Regensburg Haskell meetings or vote on when we meet next, please join our mailing list at http://lists.binary-kitchen.de/listinfo/haskell If you have any questions and for some reason don't want to join the mailing list, you can also email me :) Hope to see many of you tomorrow. Cheers, Andres

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idea: ratings (or maybe comments) for packages in hackage
by Ömer Sinan Ağacan 11 Nov '13

11 Nov '13

Hi all, The following is happening to me very often: - I decide to do some work in Haskell and decide to do it using a library. - I go to hackage and search for some keywords, find 10 different packages that does similar things. - In that moment, I need to apply some heuristics to decide which package to use. When my heuristics don't end up with only one package, I go to Haskell IRC channel and ask people there to which library to use. My heuristic is something like: - Look if author/maintainer is well-known people in Haskell community that are already produced very high-quality libraries. - Make sure it's currently maintained(updated at least in past few months) - Make sure it has Github repository. - some other stuff like that. These heuristics are not working great, most of the time I'm ending up with IRC channel. So my proposal is this: Why not have a rating/comment system for packages in hackage, so that when I need to find a library for something I can just look to comments or ratings to see how complete/well-implemented or what does it good for etc. (for example, we have several high quality xml parsers, some of them are for performance while some of them aiming for being easy to use) Any comments would be appreciated. --- Ömer Sinan Ağacan http://osa1.net

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Haskell talks at Code Mesh London 3-5 Dec - Early Bird ends in 3 days
by Andra Dinu 11 Nov '13

11 Nov '13

Hi, Between the 4th and 5th of December, inventors and users of the most discussed technologies of the moment will gather in London for the second edition of Code Mesh - The Alternative Programming Conference. Haskell talks include: * Haskell at Barclays: Exotic Tools for Exotic Trades - http://codemesh.io/index.html#tim-williams * The Haxl Project at Facebook - http://codemesh.io/index.html#simon-marlow * Haskell in the Newsroom - http://codemesh.io/index.html#erik-hinton Other languages discussed: Clojure, Erlang, Elixir, Rust, Julia and more! Among the 50 speakers you will also find Ruby guru and author of 'The Pragmatic Programmer' Dave Thomas, Erlang co-inventor Joe Armstrong, Elixir creator José Valim, Akka inventor Jonas Bonér, creator of the Parallela board Andreas Olofsson, creator of Catnip IDE Bodil Stokke, co-inventor of Julia Stefan Karpinski, Clojure experts Carin Meijer and Timothy Baldridge, creator of ZeroMQ Pieter Hintjens, as well as O'Reilly authors such as Francesco Cesarini and Dean Wampler. Check out the entire programme on the conference website: http://codemesh.io/ Thanks, Andra -- Andra Dinu Community & Social ERLANG SOLUTIONS LTD New Loom House 101 Back Church Lane London, E1 1LU United Kingdom Tel +44(0)2076550344 Mob +44(0)7983484387 www.erlang-solutions.com

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Installing pandoc without root
by Theo Moore 11 Nov '13

11 Nov '13

I am trying to install the Haskell libraries for pandoc on a local home folder and without root access, using the command: cabal install pandoc However, I run into the error: cabal: Missing dependency on a foreign library: * Missing (or bad) header file: zlib.h * Missing C library: z >From what I understand, I need to install zlib1g-dev. GHC and cabal install are available, but without root access I'm having trouble figuring out how to provide the necessary zlib files. I've tried to download the source of zlib1g-dev, but in order to compile it, I have to use "make" which I do not have the priviledge to invoke. Can someone guide me through getting pandoc up and running without root access? The system is Debian 3.2.41-2 x86_64 GNU/Linux.

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Expressing "self-composable" functions at the type level
by Ignas Vyšniauskas 10 Nov '13

10 Nov '13

Hi, I'm wondering if there's some way to express that a function can be composed with itself at the type level. Due to polymorphism this is not quite the same as saying that the domain and co-domain match. Example: swap :: (a, b) -> (b, a) swap . swap :: (a, b) -> (a, b) I'd like to write a function such as (in pseudocode): involute :: ((a -> b) &&& (b -> a)) -> (a -> a) involute f = f . f But I obviously can't write down the type for (a -> b) &&& (b -> a) Perhaps this can be done with some typeclass hackery? -- Ignas

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Re: [Haskell-cafe] IDE
by Schell Scivally 09 Nov '13

09 Nov '13

I use vim for all dev work except iOS. Specifically I use MacVim on OS X and GVim on Linux. Once I switched to vim I never looked back. Here are some plugins that I use: http://github.com/gmarik/vundle -- Package manager http://github.com/Shougo/vimproc -- Required for ghcmod-vim http://github.com/Shougo/neocomplcache -- Completion http://github.com/Shougo/neosnippet -- Snippets http://github.com/schell/vim-snippets -- Snippets http://github.com/scrooloose/syntastic -- Syntax checking http://github.com/scrooloose/nerdtree -- File drawer http://github.com/altercation/vim-colors-solarized -- Color theme http://github.com/ujihisa/neco-ghc -- Haskell completion for neocomplcache http://github.com/tpope/vim-fugitive.git-- Git integration http://github.com/kien/ctrlp.vim -- Sublime text's anything command (quick goto) http://github.com/Lokaltog/vim-powerline-- Status line http://github.com/majutsushi/tagbar -- Symbol goto based on ctags http://github.com/kana/vim-fakeclip -- OS X clipboard support http://github.com/flazz/vim-colorschemes-- More colorschemes http://github.com/eagletmt/ghcmod-vim -- Syntax/compilation checking, quickfix integration http://github.com/travitch/hasksyn -- Better haskell syntax coloring http://github.com/dag/vim2hs -- More haskell syntax coloring I have a lot of Haskell syntax plugins and some of those may be conflicting, IDK, but it works well IMO. Using all that I get a pretty good IDE feeling when developing in Haskell. I also use a tool called steeloverseer that I wrote to continuously compile my cabal projects. If you're interested it's on hackage and you can read the readme at https://github.com/schell/steeloverseer/. I hope that helps!

1 0

float show instances
by Evan Laforge 09 Nov '13

09 Nov '13

Ok, here's a bit of shameless bike-sheddery, so feel free to move on if you don't have time for that kind of thing. It seems silly, but this is something that's been bothering me for something like 5 years now, namely that ghc's float show instance is very aggressive about resorting to scientific notation for numbers below 1. If you get to 0.01 it writes it as 1.0e-2. Python and ruby, by comparison, have the cutoff at 1e-5. But it's only for <1, if you go higher you have to get all the way up to 1.0e7 before it goes exponential (python and ruby are even more reluctant: 1e16 and 1e14 respectively). This little detail has been a constant low-grade hassle for me because I don't read scientific notation fluently, and it's hard for me to see relative magnitudes in a big chunk of floats. In the past I've resorted to copy pasting a list into a python prompt or a separate pretty printer program, and in the present I have my own replacement for Show that is less aggressive with scientific notation, in addition to other things. So I was wondering, was this a considered design choice, or just the preference of the person who happened to write Show Float and Show Double way back when? Are there people who read scientific notation just as easily as positional (and if so, would they prefer to see 100 as 1e3)? Is there hope that if I look at it enough maybe someday it'll be clear to me too? I'm not actually expecting anyone will say "why didn't we think of that, let's change it right away", but I'm curious about how it came about, and whether other people have resorted to as drastic measures as I have. As an aside, I've noticed that when I'm debugging, the formatting of the output is very important. Surprisingly so. It's worth it for me to spend extra time making test and debugging output minimal and clear, otherwise my brain is already overtaxed trying to understand the problem, and just can't handle extra load like skipping irrelevant data, figuring out scientific notation, and even trying to figure out where the breaks are in un-spaced output. Maybe a personal quirk.

5 5

a tiny HTTP server.. that doesn't work
by Corey O'Connor 09 Nov '13

09 Nov '13

I attempted to write a tiny HTTP server using only Haskell Platform packages: * https://github.com/coreyoconnor/tiny-http-hp Which works... Unless the threaded runtime is used. When compiled using the threaded runtime and run with +RTS -N this server fails to reply correctly to ~3% of requests. The expectation is that the reply will be exactly the request body. However, 3% of the time the HTTP request fails to be parsed due to an "ErrorClosed" The server then executes: * https://github.com/coreyoconnor/tiny-http-hp/blob/master/TinyHttp.hs#L23 which responds to the client. The client receives the response correctly most of the time. My current hypothesis is that some aspect of lazy IO is not playing nice. The connection is being closed before the request can be completely parsed. Is this correct? What am I missing? I know there are other HTTP server packages that could be used. However, the exercise was to build a HTTP server using only Haskell Platform packages. Below is the main body of the code: main = withSocketsDo $ do http_socket <- listenOn $ PortNumber 9090 dispatch_on_accept http_socket $ either handle_failed_request handle_valid_request sClose http_socket handle_failed_request failure = return $ Response (4,0,0) "Bad Request" [mkHeader HdrConnection "close"] (encodeUtf8 $ pack $ show failure) handle_valid_request request = do let request_body = rqBody request return $ Response (2,0,0) "OK" [mkHeader HdrConnection "close"] (encodeUtf8 $ pack $ show request_body) dispatch_on_accept http_socket handler = forever $ accept http_socket >>= forkIO . httpHandler . fst where httpHandler client_socket = bracket (socketConnection "client" 0 client_socket) Network.HTTP.close client_interact client_interact :: HandleStream BS.ByteString -> IO () client_interact byte_stream = receiveHTTP byte_stream >>= handler >>= respondHTTP byte_stream -Corey O'Connor coreyoconnor(a)gmail.com http://corebotllc.com/

3 8

Help using Groundhog Template Haskell.
by Andrew Myers 08 Nov '13

08 Nov '13

Hi Cafe, I'm trying to experiment with groundhog because I want something that I can map between arbitrary ADTs and arbitrary Schema. Groundhog looks like exactly what I want but I'm hung up on an error coming from the mkPersist TH function. When I compile the code below with ghc --make groundhog.hs I get this error: groundhog.hs:23:1: Function binding for `Database.Groundhog.Core.entityFieldChain' has no equations When splicing a TH declaration: I'm pretty sure it has something to do with the TransactionType not being made up of primitive types but I'm not sure what to do about it. Can someone familiar with the library point me in the right direction? Thanks, Andrew Myers {-# LANGUAGE TemplateHaskell, QuasiQuotes #-} module Checking.Database.Groundhog where import qualified Database.Groundhog.TH as TH import qualified Data.Text as T import qualified Data.Time as D import qualified Control.Lens as L data TransactionType = Deposit | Debt | Informational deriving (Show, Eq, Read) data Transaction = Transaction { _transactionDate :: D.UTCTime , _transactionAmount :: Double , _transactionDescription :: T.Text , _transactionBalanced :: Bool , _transactionCheckNumber :: Maybe Int , _transactionTransactionType :: TransactionType } deriving (Show, Read, Eq) TH.mkPersist TH.defaultCodegenConfig [TH.groundhog| - entity: Transaction constructors: - name: Transaction fields: - name: _transactionDate dbName: date exprName: DateField - name: _transactionAmount dbName: amount exprName: AmountField - name: _transactionDescription dbName: description exprName: DescriptionField - name: _transactionBalanced dbName: balanced exprName: BalancedField - name: _transactionCheckNumber dbName: check_number exprName: CheckNumberField - name: _transactionTransactionType dbName: transaction_type exprName: TransactionTypeField - entity: TransactionType |]

2 1

Job opportunities at Startup - London and Exeter
by Ben Moseley 08 Nov '13

08 Nov '13

If you are an experienced developer, have a keen interest in functional programming and would be interested in working at an ambitious, funded, consumer-focused UK startup, please get in touch with me. Our main server-side infra is Haskell-based but we also use Java and Objective-C for the mobile platforms we target. Beyond the obvious technical skills, successful candidates will need focus and determination to get the job done. In return we offer a hugely exciting and challenging working environment, competitive compensation, a great culture (we'll probably try and drag you away from your keyboard and onto a mountain bike) and an experienced management team with a proven track-record. We are looking for developers to be based in London and Exeter. -- Ben Moseley - Programmer ben(a)benmoseley.net

1 0

QuickCheck
by Tony Morris 08 Nov '13

08 Nov '13

Hello, I have implemented a function for QuickCheck: untilJust :: Gen a -> (a -> Maybe b) -> Gen b I based it on the code for suchThat[1] and suchThatMaybe[2]. I am wondering if I have potentially re-implemented an existing function in part or full. In other words, is there an easier way of achieving this function without pulling the generator apart as much as I have in this implementation: http://lpaste.net/95317 [1] suchThat :: Gen a -> (a -> Bool) -> Gen a http://hackage.haskell.org/package/QuickCheck-2.6/docs/src/Test-QuickCheck-… [2] suchThatMaybe :: Gen a -> (a -> Bool) -> Gen (Maybe a) http://hackage.haskell.org/package/QuickCheck-2.6/docs/src/Test-QuickCheck-… -- Tony Morris http://tmorris.net/

2 1

concatMap with state for Data.Vector?
by Evan Laforge 08 Nov '13

08 Nov '13

This is a Data.Vector question, hopefully here is a good place for those. Or would it be better to ask on stackoverflow? I want to generate a vector from another, where I interpolate between each point. So I need something like concatMap because the vector gets longer, but I need state because I need to remember the previous value (and I need to look at the next value to avoid overrunning, but that can be done with state and 'tails'). Stated imperatively, it would look like this: state = Nothing out = [] for (x, y) in signal: case state of Nothing -> out.append (x, y) Just (x0, y0) -> for (x, y) in interpolate ...: out.append (x, y) state = Just (x, y) The simplest option would be just doing the transformation on a list: `Vector.concat . snd . List.mapAccumL go Nothing . Vector.toList` But unless fusion is more powerful than I imagined, that builds a couple of lists and a bunch of intermediate vectors. I did try to read the core, but it's hard to follow when vector is involved. If they're large, it's probably no worse than a builder, but if they're small, well I'd want a builder to fill up each chunk efficiently... but there's no builder for Data.Vector (I did write one once, maybe I should pull it out and dust it off). unfoldr could also do it, but to emit multiple samples I'd need to make the state `Either ([a], state) state`, and some awkward plumbing, and constant tag checks. So it's looking like converting to a list and back is the most reasonable option... unless there's some way to express this that I'm missing?

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Re: [Haskell-cafe] Better integration with Xcode
by David Banas 07 Nov '13

07 Nov '13

Could the originator of this thread say something, as to what advantages his approach has over Leksah, please? Thanks, -db

2 1

Haskell Weekly News: Issue 285
by Daniel Santa Cruz 07 Nov '13

07 Nov '13

Welcome to issue 285 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the weeks of October 20 to November 02, 2013. Quotes of the Week * roconnor: edwardk: is comonad Haskell 1.4? I liked Haskell 1.4. * Peaker: Don't trust the @src, luke * dmwit: If it fits in a tweet, you haven't included enough information to debug it yet. Top Reddit Stories * The Haskell Cast #3 - Simon Peyton Jones on GHC Domain: haskellcast.com, Score: 88, Comments: 11 On Reddit: [1] http://goo.gl/0sGzlg Original: [2] http://goo.gl/wQ4FKi * Elm 0.10 released: faster strings, nice colors, bug fixes, and searchable documentation Domain: elm-lang.org, Score: 74, Comments: 9 On Reddit: [3] http://goo.gl/HJ2fc7 Original: [4] http://goo.gl/xFJJMN * Procrustean Mathematics by Edward Kmett Domain: fpcomplete.com, Score: 71, Comments: 17 On Reddit: [5] http://goo.gl/AsB0CM Original: [6] http://goo.gl/E1iDNM * Haskell hurdle: uninteresting world Domain: gundersen.net, Score: 68, Comments: 58 On Reddit: [7] http://goo.gl/W8l3T1 Original: [8] http://goo.gl/uBVp1f * websockets-0.8 released: with browser shell example + bonus section on pipes vs. conduit vs. io-streams Domain: jaspervdj.be, Score: 65, Comments: 9 On Reddit: [9] http://goo.gl/0XvXZa Original: [10] http://goo.gl/eUDMn1 * IHaskell: Haskell for Interactive Computing Domain: gibiansky.github.io, Score: 61, Comments: 26 On Reddit: [11] http://goo.gl/ZpNpq8 Original: [12] http://goo.gl/A8iccI * ShellCheck – static analysis and linting tool for sh/bash script Domain: shellcheck.net, Score: 55, Comments: 10 On Reddit: [13] http://goo.gl/z0giaP Original: [14] http://goo.gl/zF3DLB * Micro-tutorial: liftM by accident Domain: self.haskell, Score: 54, Comments: 29 On Reddit: [15] http://goo.gl/d6ReRs Original: [16] http://goo.gl/d6ReRs * Barclays are hiring: Haskell developers in London and Kiev Domain: self.haskell, Score: 52, Comments: 14 On Reddit: [17] http://goo.gl/Fq7JPE Original: [18] http://goo.gl/Fq7JPE * License monads Domain: joeyh.name, Score: 52, Comments: 18 On Reddit: [19] http://goo.gl/oZ9La1 Original: [20] http://goo.gl/9C1Stp * Show Reddit: My weekend project, PureScript Domain: functorial.com, Score: 49, Comments: 61 On Reddit: [21] http://goo.gl/sRx1Eh Original: [22] http://goo.gl/TJBCYN * Deamortized ST by Edward Kmett Domain: fpcomplete.com, Score: 49, Comments: 57 On Reddit: [23] http://goo.gl/Vck3Ij Original: [24] http://goo.gl/wtaueO * HaLVM 2.0 Developer's Release (trans: buggy but API-stable pre-release) now available for folks to try. GHC 7.8, threaded RTS, SMP HaLVM support, 0-copy networking, and more. Domain: community.galois.com, Score: 44, Comments: 13 On Reddit: [25] http://goo.gl/5Psg7B Original: [26] http://goo.gl/xQFUA2 * Could you explain why complexity of monadic IO is worth it? Domain: self.haskell, Score: 43, Comments: 128 On Reddit: [27] http://goo.gl/esFCc4 Original: [28] http://goo.gl/esFCc4 * London Haskell User Group 18/09/2013: Oliver Charles on pipes [video] Domain: ocharles.org.uk, Score: 42, Comments: 14 On Reddit: [29] http://goo.gl/8kDKnw Original: [30] http://goo.gl/hi3L3P * C-- as a project separate from GHC Domain: cminusminus.org, Score: 42, Comments: 14 On Reddit: [31] http://goo.gl/fvUjIk Original: [32] http://goo.gl/VueAA * How to start a new Haskell project Domain: jabberwocky.eu, Score: 42, Comments: 26 On Reddit: [33] http://goo.gl/6dRRXn Original: [34] http://goo.gl/btWJYS * The let-no-escape optimization Domain: lambda.jstolarek.com, Score: 41, Comments: 1 On Reddit: [35] http://goo.gl/l8xhuP Original: [36] http://goo.gl/J8uekI * Improving Applicative do-notation Domain: tmorris.net, Score: 40, Comments: 150 On Reddit: [37] http://goo.gl/MXoPdz Original: [38] http://goo.gl/y1I8Tx * Odersky: The Trouble with Types - Strange Loop 2013 [InfoQ] Domain: infoq.com, Score: 39, Comments: 55 On Reddit: [39] http://goo.gl/5QEJfz Original: [40] http://goo.gl/Ir4kwG Top StackOverflow Questions * Haskell Thrift library 300x slower than C++ in performance test votes: 34, answers: 5 Read on SO: [41] http://goo.gl/timvYf * Creating methods bound to records in Haskell votes: 10, answers: 1 Read on SO: [42] http://goo.gl/4E4Sgh * Installing & Building GHC with OSX Mavericks GHC votes: 10, answers: 1 Read on SO: [43] http://goo.gl/44PIaj * How to properly communicate compile-time information to Template Haskell functions? votes: 10, answers: 0 Read on SO: [44] http://goo.gl/YQkGbl * Data.Text vs String votes: 9, answers: 2 Read on SO: [45] http://goo.gl/ttjnJ1 * Why is matrix multiplication faster with Repa than with hmatrix? votes: 9, answers: 1 Read on SO: [46] http://goo.gl/e36toD * Efficient functional algorithm for computing closure under an operator votes: 8, answers: 1 Read on SO: [47] http://goo.gl/538Yyr * Why doesn't Haskell sequence these IO actions properly? votes: 8, answers: 2 Read on SO: [48] http://goo.gl/82PZYb * Is there a way to make my word counting program faster without using impure tricks? votes: 8, answers: 1 Read on SO: [49] http://goo.gl/F3OiUk * Is it better to define Functor in terms of Applicative in terms of Monad, or vice versa? votes: 8, answers: 3 Read on SO: [50] http://goo.gl/xEkVIf * Standard Haskell function :: (a -> Maybe b) -> [a] -> Maybe b votes: 8, answers: 3 Read on SO: [51] http://goo.gl/JdA5Xf * Why are cabal reinstalls “always dangerous”? votes: 8, answers: 1 Read on SO: [52] http://goo.gl/kCdUsL * How to use the maybe monoid and combine values with a custom operation, easily? votes: 8, answers: 3 Read on SO: [53] http://goo.gl/BpL8NK Until next time, [54]+Daniel Santa Cruz References 1. http://www.haskellcast.com/episode/003-simon-peyton-jones-on-ghc/ 2. http://www.reddit.com/r/haskell/comments/1pe8tj/the_haskell_cast_3_simon_pe… 3. http://elm-lang.org/blog/announce/0.10.elm 4. http://www.reddit.com/r/haskell/comments/1p43xx/elm_010_released_faster_str… 5. https://www.fpcomplete.com/user/edwardk/editorial/procrustean-mathematics 6. http://www.reddit.com/r/haskell/comments/1p85al/procrustean_mathematics_by_… 7. http://www.gundersen.net/functional-programming-hurdle-uninteresting-progra… 8. http://www.reddit.com/r/haskell/comments/1oyy54/haskell_hurdle_uninterestin… 9. http://jaspervdj.be/posts/2013-10-22-websockets-0.8.html 10. http://www.reddit.com/r/haskell/comments/1p0bey/websockets08_released_with_… 11. http://gibiansky.github.io/IHaskell/ 12. http://www.reddit.com/r/haskell/comments/1oxj6k/ihaskell_haskell_for_intera… 13. http://www.shellcheck.net/about.html 14. http://www.reddit.com/r/haskell/comments/1pg7ym/shellcheck_static_analysis_… 15. http://www.reddit.com/r/haskell/comments/1pd1ep/microtutorial_liftm_by_acci… 16. http://www.reddit.com/r/haskell/comments/1pd1ep/microtutorial_liftm_by_acci… 17. http://www.reddit.com/r/haskell/comments/1p70l3/barclays_are_hiring_haskell… 18. http://www.reddit.com/r/haskell/comments/1p70l3/barclays_are_hiring_haskell… 19. http://joeyh.name/blog/entry/license_monads/ 20. http://www.reddit.com/r/haskell/comments/1plql7/license_monads/ 21. http://functorial.com/purescript/ 22. http://www.reddit.com/r/haskell/comments/1pkzd0/show_reddit_my_weekend_proj… 23. https://www.fpcomplete.com/user/edwardk/oblivious/deamortized-st 24. http://www.reddit.com/r/haskell/comments/1pnrqn/deamortized_st_by_edward_km… 25. http://community.galois.com/pipermail/halvm-devel/2013-October/000041.html 26. http://www.reddit.com/r/haskell/comments/1ot4ep/halvm_20_developers_release… 27. http://www.reddit.com/r/haskell/comments/1owtvs/could_you_explain_why_compl… 28. http://www.reddit.com/r/haskell/comments/1owtvs/could_you_explain_why_compl… 29. http://ocharles.org.uk/blog/posts/2013-10-23-pipes-talk.html 30. http://www.reddit.com/r/haskell/comments/1p1wrt/london_haskell_user_group_1… 31. http://www.cminusminus.org/ 32. http://www.reddit.com/r/haskell/comments/1pbbon/c_as_a_project_separate_fro… 33. http://jabberwocky.eu/2013/10/24/how-to-start-a-new-haskell-project/ 34. http://www.reddit.com/r/haskell/comments/1pdxcr/how_to_start_a_new_haskell_… 35. http://lambda.jstolarek.com/2013/10/let-no-escape/ 36. http://www.reddit.com/r/haskell/comments/1pi6fz/the_letnoescape_optimizatio… 37. http://tmorris.net/posts/applicative-do/index.html 38. http://www.reddit.com/r/haskell/comments/1ou06l/improving_applicative_donot… 39. http://www.infoq.com/presentations/data-types-issues 40. http://www.reddit.com/r/haskell/comments/1pjjy5/odersky_the_trouble_with_ty… 41. http://stackoverflow.com/questions/19512952/haskell-thrift-library-300x-slo… 42. http://stackoverflow.com/questions/19484232/creating-methods-bound-to-recor… 43. http://stackoverflow.com/questions/19579577/installing-building-ghc-with-os… 44. http://stackoverflow.com/questions/19679024/how-to-properly-communicate-com… 45. http://stackoverflow.com/questions/19608745/data-text-vs-string 46. http://stackoverflow.com/questions/19733382/why-is-matrix-multiplication-fa… 47. http://stackoverflow.com/questions/19485082/efficient-functional-algorithm-… 48. http://stackoverflow.com/questions/19513660/why-doesnt-haskell-sequence-the… 49. http://stackoverflow.com/questions/19535688/is-there-a-way-to-make-my-word-… 50. http://stackoverflow.com/questions/19635265/is-it-better-to-define-functor-… 51. http://stackoverflow.com/questions/19643664/standard-haskell-function-a-may… 52. http://stackoverflow.com/questions/19692644/why-are-cabal-reinstalls-always… 53. http://stackoverflow.com/questions/19706501/how-to-use-the-maybe-monoid-and… 54. https://plus.google.com/105107667630152149014/about

1 0

Better integration with Xcode
by haskell cafe 07 Nov '13

07 Nov '13

I'm pretty new to Haskell, but have been having fun learning it. Being a Mac and Windows programmer most of my life, I'm used to using GUIs and IDEs to program and don't really care for using command-line tools. As such, I've been working on getting Xcode to build Haskell files directly and I have something working that I thought others might be interested in. Looking through the "Building/Cross-Compiling/iOS" instructions, it looks like the standard way of building Haskell files is to build them on the command line into a library and then link your C/C++/Objective-C sources against the library. But you don't need to do this. You can directly edit Haskell in Xcode (with very basic syntax highlighting), and build it from Xcode all without ever going to the command-line. Would people be interested in working this way? If so, I'll be happy to post steps to do it. -DC

1 2

Stackage Package List
by Daniel Díaz Casanueva 07 Nov '13

07 Nov '13

Hello Haskellers. I was looking for a complete list of the packages included in Stackage, the vetted (sub)set of packages from Hackage. I couldn't find one (except by looking at the source code of Stackage [1] directly) so I made one. http://daniel-diaz.github.io/stackagelist It is automatically updated regularly, based on the GitHub repo of Stackage. As a next step, I will include also the list of packages that are not included directly on Stackage, but as a dependency of an included package. This way, it will be possible to check easily which libraries will be available after building Stackage, also having access to their documentation via links to Hackage. I was doing this for me, but I thought it could be useful for someone else, so I share it. Best regards, Daniel Díaz. -- References [1] https://github.com/fpco/stackage/blob/master/Stackage/Config.hs

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Deprecation of MonadCatchIO-transformers
by Arie Peterson 06 Nov '13

06 Nov '13

Hi all, As discussed before <http://www.mail-archive.com/haskell-cafe@haskell.org/msg104498.html>, the interface of the MonadCatchIO packages is effectively deprecated by the removal of the 'block' and 'unblock' functions in base-4.7. I would like to deprecate MonadCatchIO-transformers now. As there are quite a few reverse dependencies, and as there is at least one use case that apparently cannot be migrated easily <http://www.mail-archive.com/haskell-cafe@haskell.org/msg104501.html>, I will try to keep the package functioning, for now. In order to do this, I followed Edward Z. Yang's suggestion, and re- implemented the IO instances of block and unblock, in terms of GHC primitives. The instance now reads > import qualified Control.Exception.Extensible as E > import GHC.Base (maskAsyncExceptions#) > import GHC.IO (unsafeUnmask,IO(IO)) > > instance MonadCatchIO IO where > catch = E.catch > block = \ (IO io) -> IO $ maskAsyncExceptions# io > unblock = unsafeUnmask You can get a release candidate for a new version 0.3.1.0, by darcs get http://patch-tag.com/r/AriePeterson/MonadCatchIO-transformers I would be most grateful if someone could review and/or test this under GHC 7.8! Regards, Arie

1 0

Unused Arrow commands do not give warning
by Tom Ellis 06 Nov '13

06 Nov '13

GHC can give you a warning when you fail to use the result of a monadic action in a do block. The same does not hold for arrow commands in arrow notation. (See demonstration below signature). What would it take to add a warning for this? I am writing arrow-heavy code at the moment and I think such a warning would be a nice feature. Tom % cat Test.hs {-# LANGUAGE Arrows #-} module Test where import Control.Arrow (returnA, arr) import Control.Monad.Identity (Identity(..)) foo :: Identity () foo = do Identity True return () bar :: () -> () bar = proc () -> do arr (const True) -< () returnA -< () % ghc -fforce-recomp -Wall Test.hs [1 of 1] Compiling Test ( Test.hs, Test.o ) Test.hs:10:5: Warning: A do-notation statement discarded a result of type Bool. Suppress this warning by saying "_ <- Data.Functor.Identity.Identity GHC.Types.True", or by using the flag -fno-warn-unused-do-bind

1 0

Soostone Hiring In Turkey
by Ozgun Ataman 05 Nov '13

05 Nov '13

Dear Haskellers, Soostone is hiring Haskell programmers for its Turkey R&D group located in METU research park in Ankara. These position(s) are only available for local candidates with no possibility for remote work at this point in time. Interested fellow Haskellers may respond directly to me or to jobs(a)soostone.com. Soostone is an enterprise analytics company with a technology stack built entirely on Haskell. We work on interesting engineering challenges that span a multitude of topics in our area of expertise, including big-data crunching, predictive models, machine learning, data visualization and web-app development - all predominantly using Haskell. As a full-time member of our team in Ankara, you will work collaboratively with our HQ team in New York and get a chance to put your Haskell skills to use in real-world research, products and services. Soostone is also very involved with the open source community. Our team members maintain several packages on Hackage, contribute significantly to the Snap Web Framework, co-organize the New York Haskell Meetup and frequently participate in various community debates. We encourage all our team members to play an active role in the community in ways they find interesting and rewarding. Ideal candidates for this position will have: - A solid grasp of the Haskell language with an ability to produce working code from from day one (monad transformers, concurrency, streaming IO, dealing with space leaks, etc.) - Significant experience crafting software products, in academia and/or the industry - Strong presence in the OSS community with released packages in Hackage considered a big plus - Good communication skills and comfort in working as part of a team - Significant experience in a relevant application area such as compilers, distributed computing, numerics, machine learning, simulations or graphics - Experience in web application development and familiarity with web technologies - Willingness and enthusiasm to learn quickly and extend capabilities in new directions as necessary We look forward to hearing from interested candidates. The Soostone Team

2 1

Cabal: --enable-shared and executables
by Magnus Therning 05 Nov '13

05 Nov '13

We've had a discussion about DSOs on the arch-haskell mailing list[1] and it made me realise one thing: --enable-shared will cause the generation of DSOs for libraries, but it won't cause executables to be dynamically linked Is the only way to cause these executables to be dynamically linked against their dependencies to pass the -dynamic flag to ghc (e.g. via the --ghc-options flag when configuring the package)? That then raises the issue of finding the DSOs. Something that is discussed in the Ghc documentation[2]. However, the generated DSOs are correctly linked to their dependencies. I guess what I'm trying to get to is that it seems to me that Cabal only provides half the solution to DSOs; it solves generation, but not usage. Is that an observation that people agree with? Are there any plans to solve this (maybe it's already solved in 1.18)? /M [1]: http://www.haskell.org/pipermail/arch-haskell/2013-October/004599.html [2]: http://www.haskell.org/ghc/docs/7.6.3/html/users_guide/using-shared-libs.ht… -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: magnus(a)therning.org jabber: magnus(a)therning.org twitter: magthe http://therning.org/magnus The day after tomorrow is the third day of the rest of your life.

5 9

When will next release of haskell-platform come?
by yi lu 05 Nov '13

05 Nov '13

Hi, As the subject goes, when will it come? http://trac.haskell.org/haskell-platform/wiki/ReleaseTimetable Even though I hope for a `good` release to use, I hope to use it earlier. BTW, what are you expecting for this release? Best Regards, Yi

2 1

updating multiple fields of a record with lenses
by felipe zapata 05 Nov '13

05 Nov '13

Dear Haskellers, let's suppose I have the following lenses data Foo = Foo { _a :: String _b :: [Double] _c :: Vector Double _d :: Int .............. (more fields) _z :: Double } Now, I want to update fields a,b,c and d without changing the rest. What is the functional way of doing it ? Surely there a function smarter than set a "String" . set b [1,2,3] . set c <1,2,3> . set d 4 $ foo can some please help me with it? Thanks in advance, Felipe Z.

3 2

ANNOUNCE: Rlang-QQ 0.1
by adam vogt 04 Nov '13

04 Nov '13

Greetings, I'm pleased to announce a new version of Rlang-QQ. It is a way to get R code inline in you .hs files. The main highlight for this release is that correctly named variables assigned to in R are available to haskell. Many data types can be converted. You can get this package by cabal update && cabal install Rlang-QQ Please refer to the documentation here <http://hackage.haskell.org/package/Rlang-QQ-0.1.0.2> or in the examples/* that you can get at with a: cabal unpack Rlang-QQ Regards, Adam Vogt

1 0

SSL support for hackage and cabal
by Eli Frey 04 Nov '13

04 Nov '13

Hello all, It recently came to my attention that hackage is http only. I would love to do anything I can to help hackage support https. What is the process for volunteering with the IHG (I imagine this is the avenue for helping with hackage/haskell.org) If the IHG is having dificulty getting an SSL certificate, GlobalSign (ful disclosure, they are my employer) provides free certificates to FOSS projects. here is a link: https://www.globalsign.com/ssl/ssl-open-source/ I am also concerned that cabal does not have support for SSL, but hackage must come first and at least then a sufficiently paranoid person can download their packages over https and ad them to their cabal sandboxes. Cheers, Eli

14 25

How to avoid floods of fromIntegral (in ALSA.Sequencer)
by martin 04 Nov '13

04 Nov '13

Hello all, in my recent attempts to work with ALSA.Sequencer, I frequently stumble across the problem that this library uses GHC.Word.Word8 (don't know where this comes from), but I am passing in plain Ints. Adding a fromIntegral solves this issue, but I end up with code like the following: type T = Int -- time type C = Int -- channel type N = Int -- note type V = Int -- velocity type L = Int -- LSB type M = Int -- MSB type P = Int -- program type X = Int -- something data DtzEvent = NoteOn C N V | NoteOff C N V | ProgChange C P | PitchBend C X | BankSelMsb C X | BankSelLsb C X ... playSong :: DtzEvents -> IO() playSong events = runContT (foo "128:0" 120 (map render events)) print where render (t,(NoteOn c n v)) = ((fromIntegral t), noteOn (fromIntegral c) (fromIntegral n) (fromIntegral v)) render (t,(NoteOff c n v)) = ((fromIntegral t), noteOff (fromIntegral c) (fromIntegral n) (fromIntegral v)) render (t,(ProgChange c p)) = ((fromIntegral t), progChange (fromIntegral c) (fromIntegral p)) render (t,(PitchBend c x)) = ((fromIntegral t), pitchBend (fromIntegral c) (fromIntegral x)) render (t,(BankSelMsb c x)) = ((fromIntegral t), bankSelMsb (fromIntegral c) (fromIntegral x)) render (t,(BankSelLsb c x)) = ((fromIntegral t), bankSelLsb (fromIntegral c) (fromIntegral x)) The last piece looks pretty ugly. Is there a way to avoid this?

4 4

Can't install vector-0.10.9.1 on OS X Maverick
by Alfredo Di Napoli 04 Nov '13

04 Nov '13

Hello Cafè, this is what I'm getting: ╰─$ cabal install vector-0.10.9.1 1 ↵ Resolving dependencies... Configuring vector-0.10.9.1... Building vector-0.10.9.1... Preprocessing library vector-0.10.9.1... [ 1 of 19] Compiling Data.Vector.Storable.Internal ( Data/Vector/Storable/Internal.hs, dist/build/Data/Vector/Storable/Internal.o ) [ 2 of 19] Compiling Data.Vector.Fusion.Util ( Data/Vector/Fusion/Util.hs, dist/build/Data/Vector/Fusion/Util.o ) [ 3 of 19] Compiling Data.Vector.Fusion.Stream.Size ( Data/Vector/Fusion/Stream/Size.hs, dist/build/Data/Vector/Fusion/Stream/Size.o ) Data/Vector/Fusion/Stream/Size.hs:25:10: Warning: No explicit method or default declaration for `*' In the instance declaration for `Num Size' Data/Vector/Fusion/Stream/Size.hs:25:10: Warning: No explicit method or default declaration for `abs' In the instance declaration for `Num Size' Data/Vector/Fusion/Stream/Size.hs:25:10: Warning: No explicit method or default declaration for `signum' In the instance declaration for `Num Size' [ 4 of 19] Compiling Data.Vector.Internal.Check ( Data/Vector/Internal/Check.hs, dist/build/Data/Vector/Internal/Check.o ) [ 5 of 19] Compiling Data.Vector.Fusion.Stream.Monadic ( Data/Vector/Fusion/Stream/Monadic.hs, dist/build/Data/Vector/Fusion/Stream/Monadic.o ) Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... <command line>: can't load .so/.DLL for: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib/libiconv.dylib (dlopen(/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib/libiconv.dylib, 9): no suitable image found. Did find: /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/lib/libiconv.dylib: mach-o, but wrong filetype) Failed to install vector-0.10.9.1 cabal: Error: some packages failed to install: vector-0.10.9.1 failed during the building phase. The exception was: ExitFailure 1 I've did the trick of installing gcc-4.8 as described here: http://cp.reddit.com/r/haskell/comments/1ozukp/anyone_running_ghc_763_on_os… I'm running a compiled version of ghc 7.6.3 (so not installed via the Haskell platform). Have anyone stumbled upon this? Thanks, Alfredo

2 9

more generic class instances?
by Christopher Howard 02 Nov '13

02 Nov '13

Hi. I am playing around with basic Haskell overloading. What I'm interested in is how to do specialization in Haskell -- i.e., functions that work generically on all (or many) types but work more efficiently on certain types. So, I am trying to make a class of functions which can be fed into a partial sum calculator. Maybe something like so: class PartialSum f where -- params: term function, end index partialSum :: Integral b => f -> b -> a The most generic instance would be any function that takes an integer and returns a number. The specialized instances would things like, say, a wrapped function which is guaranteed to be linear (through safe constructors or something). But I'm having trouble figuring out how even to make the generic version. I'm thinking something like this: instance PartialSum (a -> b) where partialSum f n = foldl (\u v -> u + f v) 0 [1..n] But the compiler complains it can't prove that the input to the "f" function is the same type as the "n" parameter. That makes sense, but I'm not sure how to fix that.

2 5

LiberalTypeSynonyms: documentation issue
by Obscaenvs 02 Nov '13

02 Nov '13

In the docs for GHC 7.6.3, e.g. at [1], it is said that one can use LiberalTypeSynonyms as so: `type Discard a = forall b. Show b => a -> b -> (a, String)` This is, however, not possible without RankNTypes which is stated in a tutorial at FPComplete [2] and, of course, GHC 7.6.3 itself says so when trying to compile something with the above definition for Discard: ` Illegal polymorphic or qualified type: forall b. Show b => a -> b -> (a, String) Perhaps you intended to use -XRankNTypes or -XRank2Types In the type declaration for `Discard' ` Maybe the GHC User Guide should be updated to reflect this? /Fredrik References: [1] http://www.bugthunk.net/ghc/docs/7.6.3/html/users_guide_repl/data-type-exte… [2] https://www.fpcomplete.com/school/to-infinity-and-beyond/pick-of-the-week/g…

1 0

beginners list for common lisp?
by Christopher Howard 02 Nov '13

02 Nov '13

Does anybody know if there is something like a Common Lisp version of the Haskell Beginner's mailing list? Haskell's great, of course, but I've also been picking up Lisp, and I'm looking for a Lisp list that is very newbie friendly.

3 2

Re: [Haskell-cafe] Cabal sandboxes over cabal-dev (Rogan Creswick)
by Gregory Guthrie 02 Nov '13

02 Nov '13

"I *strongly* suggest everyone start transitioning from cabal-dev to cabal sandboxes." Is there any reason that this is not just the default install mode for Cabal? Anything that prevents the current cabal-swamp of broken dependencies is a great help. I have tried to use Haskell in some classes, but it is hard when students (and I) cannot install packages, and the only answer is the Microsoft-like; "delete everything and start over; reinstall". It certainly reduces their confidence that Haskell is a feasible working environment.

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ANNOUNCE: HList-0.3
by adam vogt 02 Nov '13

02 Nov '13

Greetings, We are pleased to announce HList-0.3. This is an update the well-known library for strongly typed heterogenous lists, records, type-indexed products (TIP) and co-products. Some of the highlights are: * works with lens. See examples/labelable.hs * modern features such as TypeFamilies, DataKinds (Symbol), ConstraintKinds, PolyKinds, QuasiQuotes * Data instances for HList and Record. One application is given in examples/cmdargs.hs * named and optional function parameters (using Keyword or perhaps RecordPuns) are part of the library proper * additional functions including: HTranspose, HZip, HFoldl, HScanr, HReplicate * improved type inference. To give an example: > let y = hMap (Fun' read :: Fun' Read String) x This is about the same as `let y = map read x', but each element of the HList `y' can have a different type. Only one of the two lengths needs to be specified. * more documentation and examples, which should make it easier to find your way around. Refer to the included ChangeLog or `darcs changes` for more details. This release requires ghc>=7.6. You can get the release from <http://hackage.haskell.org/package/HList> or use cabal-install: $ cabal update $ cabal install HList-0.3 For now it seems that hackage is rejecting the upload due to language extensions it doesn't know about, so in the meantime you can get it with: $ cabal install http://code.haskell.org/~aavogt/HList/HList-0.3.0.tar.gz With haddocks at <http://code.haskell.org/~aavogt/HList/docs/HList/>. -- Adam

1 0

How do I lift Control.Monad.Reader.local?
by David Fox 02 Nov '13

02 Nov '13

I can write a stack push function in the reader monad like so: import Control.Monad.Reader push :: String -> Reader [String] a -> Reader [String] a push s action = local (s :) action How can I write a push that works inside a monad transformer? push' :: MonadTrans t => String -> t (Reader [String]) a -> t (Reader [String]) a push' s action = ???

2 4

Internship opportunities at Galois
by Adam Foltzer 01 Nov '13

01 Nov '13

Hello, Galois has some exciting opportunities for interns in software engineering and research for 2014. Most of our projects use Haskell to some extent, so this is a great chance to get experience applying functional programming to real-world problems. Please pass along this posting to anyone you think might be interested, even if they don't yet know Haskell! Thank you, Adam Foltzer --- # Galois Software Engineering/Research Intern # Galois is currently seeking software engineering and research interns for 2014 at all educational levels. We are committed to matching interns with exciting and engaging engineering work that fits their particular interests, creating lasting value for interns, Galois, and our community. A Galois internship is a chance to tackle cutting-edge, meaningful problems in a uniquely collaborative environment with world-leading researchers. Roles may include technology research and development, requirements gathering, implementation, testing, formal verification, and infrastructure development. Past interns have integrated formal methods tools into larger projects, built comprehensive validation suites, synthesized high-performance cryptographic algorithms, written autopilots for quad-copters, designed the syntax and semantics of scripting languages, and researched type system extensions for academic publication. We deeply believe in providing comprehensive support and mentorship to all of our employees, particularly interns. We provide our employees with a steward who regularly checks in to ensure that they feel welcome and safe in the Galois community while gaining real value from their experiences. ## About Galois ## Our mission is to create trustworthiness in critical systems. We're in the business of taking blue-sky ideas and turning them into real-world technology solutions. We've been developing real-world systems for over ten years using functional programming, language design, and formal methods. Galois values diversity. We believe that differing viewpoints and experiences are essential to the process of innovation. We look broadly, including outside of established communities, to deliver innovation. ## How to Prepare ## An internship is an opportunity for learning and growth as an engineer. To make the most of the opportunity, we ask that candidates have experience reading, writing, and maintaining code in a realistic project. Many university courses involve multi-week collaborative projects that provide this type of experience. Most of our projects use the Haskell programming language and the git version control system. These tools aren't often taught in computer science classes, but there are many free resources available that we recommend for learning: - [Learn You a Haskell for Great Good!] [1] by Miran Lipovača - [Real World Haskell] [2] by Bryan O'Sullivan, Don Stewart, and John Goerzen - [tryGit] [3] by Code School - [Pro Git] [4] by Scott Chacon [1]: http://learnyouahaskell.com/ [2]: http://book.realworldhaskell.org/ [3]: http://try.github.io [4]: http://git-scm.com/book ## Qualifications ## - The ability to be geographically located in Portland during the internship - Experience reading, writing, and maintaining code in a project as described above - Proficiency in software development practices such as design, documentation, testing, and the use of version control - Well-developed verbal and written communication skills; comfort in a collaborative team environment The following skills are not required, but may be relevant to a particular project. - Proficiency in Haskell or other programming languages with rich type systems (eg., OCaml, Standard ML, Scala) - Experience using C and assembly languages for low-level systems programming - Development experience in high assurance systems or security software - Specific experience in an area of Galois' expertise, such as: - Assured information sharing - Software modelling and formal verification - Cyber-physical systems and control systems - Operating systems, virtualization and secure platforms - Networking and mobile technology - Cyber defense systems - Scientific computing - Program analysis and software evaluation - Web security ## Logistics ## The length and start date of the internship are negotiable: starting any time from the new year through next fall is acceptable, but an intern must be at Galois for at least three continuous months. The internship is paid competitively, and interns are responsible for living arrangements (although we can certainly help you find arrangements). Galois is located in the heart of downtown Portland with multiple public transportation options available and world-class bicycle infrastructure. ## Application Details ## Send an email to careers(a)galois.com with the subject line "Internship 2014" with the following contents: - Email body: a brief plain-text note explaining your interests, experience, and other relevant details - Attachment: CV/Resume (PDF, plain text, or markdown only) **Applications must be received at least two months before the desired start date**. For example, we must receive your application by November 6, 2013, if you wish to start on January 6, 2014.

1 0

Accessing own haddock files
by Corentin Dupont 01 Nov '13

01 Nov '13

Hi the list, I have an application that need to access its own haddock documentation (to display on a web site). What is the best way to do that? Unfortunatly Cabal doesn't seem to provide that. Cabal generates a file "<package name>_Path.hs" containing: *bindir = "/home/kau/.cabal/bin" libdir = "/home/kau/.cabal/lib/Nomyx-Language-0.4.0/ghc-7.6.3" datadir = "/home/kau/.cabal/share/Nomyx-Language-0.4.0"* But there is no: *docdir = "/home/kau/.cabal/share/doc/Nomyx-Language-0.4.0"* That would be handy in my situation :) Best, Corentin

2 1

Cabal sandboxes over cabal-dev
by Graham Berks 01 Nov '13

01 Nov '13

Can someone point me in the direction of why you would use one over the other ?? Thanks Graham

6 6

SYB: queries using IO Monad
by JP Moresmau 01 Nov '13

01 Nov '13

Hello cafe, I have code that works well using the syb package, and the ext1Q, extQ and gmapQ functions. This code that a Data and transforms it into something else. However I need to make a change, and this change involves calling a function in the IO monad (the function is from another library so I have no choice). However, the ext1Q, extQ and gmapQ functions have no monadic equivalent. There seems to be monadic transformation (from a to different a) but no monadic queries (from a to b). Do I have to rewrite these functions myself to work with monadic queries (it at all possible) or is there a better way? I've seen some functions that work with monads and MonadPlus, but I don't see anything that would work with IO. So far I've checked that the IO() function I'm calling does the job by using unsafePerformIO, but I know that's a sin and I'd like to find a better way! Thanks! JP -- JP Moresmau http://jpmoresmau.blogspot.com/

2 3

cabal-install sandbox with happy and alex
by Badi' Abdul-Wahid 01 Nov '13

01 Nov '13

Hi I've run into difficulty building happy and alex using the sandbox feature of cabal-install 1.18.0.2. Installation of dependencies succeeds but both happy and alex fail with: setup: The program happy is required but it could not be found My workaround is to use the --only-dependencies flag, install the dependencies, and manually install the packages. This is on Mac OS X 10.8.4 with GHC 7.6.3. I've copied the steps demonstrating the problem on lpaste: http://lpaste.net/95027 Summary to reproduce: cabal sandbox init; cabal install happy alex Below is the script for my workaround. [0 :)] badi@olorin /tmp/sb ~> cat sandbox-install.sh #!/usr/bin/env bash packages="$@" cabal sandbox init cabal install --only-dependencies $packages for p in $packages; do cabal unpack $p pushd $p-* cabal sandbox --sandbox ../.cabal-sandbox init cabal configure cabal build runhaskell Setup.lhs install popd done -- Badi' Abdul-Wahid

3 3

xmonad install problem
by Никитин Лев 31 Oct '13

31 Oct '13

1 1

Call for Contributions - Haskell Communities and Activities Report, November 2013 edition
by Janis Voigtlaender 31 Oct '13

31 Oct '13

[Transition in editorship of HCAR in progress!] Dear all, We would like to collect contributions for the 25th edition of the ================================================================ Haskell Communities & Activities Report http://www.haskell.org/haskellwiki/Haskell_Communities_and_Activities_Report Submission deadline: 1 Nov 2013 (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ================================================================ This is the short story: * If you are working on any project that is in some way related to Haskell, please write a short entry and submit it. Even if the project is very small or unfinished or you think it is not important enough --- please reconsider and submit an entry anyway! * If you are interested in an existing project related to Haskell that has not previously been mentioned in the HCAR, please tell us, so that we can contact the project leaders and ask them to submit an entry. * Feel free to pass on this call for contributions to others that might be interested. More detailed information: The Haskell Communities & Activities Report is a bi-annual overview of the state of Haskell as well as Haskell-related projects over the last, and possibly the upcoming six months. If you have only recently been exposed to Haskell, it might be a good idea to browse the previous edition --- you will find interesting projects described as well as several starting points and links that may provide answers to many questions. Contributions will be collected until the submission deadline. They will then be compiled into a coherent report that is published online as soon as it is ready. As always, this is a great opportunity to update your webpages, make new releases, announce or even start new projects, or to talk about developments you want every Haskeller to know about! Looking forward to your contributions, Mihai Maruseac and Janis Voigtlaender (for this edition) FAQ: Q: What format should I write in? A: The required format is a LaTeX source file, adhering to the template that is available at: http://haskell.org/communities/11-2013/template.tex There is also a LaTeX style file at http://haskell.org/communities/11-2013/hcar.sty that you can use to preview your entry. If you do not know LaTeX, then use plain text. If you modify an old entry that you have written for an earlier edition of the report, you should soon receive your old entry as a template (provided we have your valid email address). Please modify that template, rather than using your own version of the old entry as a template. Q: Can I include Haskell code? A: Yes. Please use lhs2tex syntax (http://www.andres-loeh.de/lhs2tex/) The report is compiled in mode polycode.fmt. Q: Can I include images? A: Yes, you are even encouraged to do so. Please use .jpg format, then. Q: Should I send files in .zip archives or similar? A: No, plain file attachements are the way. Q: How much should I write? A: Authors are asked to limit entries to about one column of text. A general introduction is helpful. Apart from that, you should focus on recent or upcoming developments. Pointers to online content can be given for more comprehensive or "historic" overviews of a project. Images do not count towards the length limit, so you may want to use this opportunity to pep up entries. There is no minimum length of an entry! The report aims for being as complete as possible, so please consider writing an entry, even if it is only a few lines long. Q: Which topics are relevant? A: All topics which are related to Haskell in some way are relevant. We usually had reports from users of Haskell (private, academic, or commercial), from authors or contributors to projects related to Haskell, from people working on the Haskell language, libraries, on language extensions or variants. We also like reports about distributions of Haskell software, Haskell infrastructure, books and tutorials on Haskell. Reports on past and upcoming events related to Haskell are also relevant. Finally, there might be new topics we do not even think about. As a rule of thumb: if in doubt, then it probably is relevant and has a place in the HCAR. You can also simply ask us. Q: Is unfinished work relevant? Are ideas for projects relevant? A: Yes! You can use the HCAR to talk about projects you are currently working on. You can use it to look for other developers that might help you. Q: If I do not update my entry, but want to keep it in the report, what should I do? A: Tell us that there are no changes. The old entry will typically be reused in this case, but it might be dropped if it is older than a year, to give more room and more attention to projects that change a lot. Do not resend complete entries if you have not changed them. Q: Will I get confirmation if I send an entry? How do I know whether my email has even reached its destination, and not ended up in a spam folder? A: Prior to publication of the final report, we will send a draft to all contributors, for possible corrections. So if you do not hear from us within two weeks after the deadline, it is safer to send another mail and check whether your first one was received.

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