November 2013 - Haskell-Cafe

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 12 Nov '13

12 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 11 Nov '13

11 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 11 Nov '13

11 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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