- Haskell-Cafe - Haskell.org

how to call a callback in a haskell dll
by Kees Bleijenberg 15 Nov '13

15 Nov '13

My program creates a Windows dll. The calling program calls a function with strings as parameters. Works fine. I want to add a extra parameter. This extra parameter is a callback: a function Int -> Int: stdcall. In Haskell I want to call this function. So I have to convert the pointer to a (formal) Haskell function. In the examples for the FFI, Haskell provides the callback. I need an example or documentation. Kees

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ANNOUNCE: Haskell Pdf Presenter (hpdfp) 0.2.2
by Michael D. Adams 15 Nov '13

15 Nov '13

ANNOUNCE: Haskell Pdf Presenter (hpdfp) 0.2.2 I'm pleased to announce the first public release of the Haskell Pdf Presenter (hpdfp). Project home page: http://michaeldadams.org/projects/haskell-pdf-presenter/ Project on Hackage: http://hackage.haskell.org/package/haskell-pdf-presenter/ Project repository: http://michaeldadams.org/repos-pub/hg/haskell-pdf-presenter/ What it is ========== The Haskell Pdf Presenter (hpdfp) is a tool for presenting PDF-based slide shows. For example, as a presenter, I like to see the next slide before it is shown to the audience as well as how much allotted time remains. I was never quite satisfied with the existing tools for this, so I wrote my own and hpdfp is the result. Though I originally wrote it for my own use, the tool has matured over time, and I now wish to share it with others. Aside from being a useful tool, I think hpdfp is a good example of elegance and economy in program design. Despite being only a thousand lines long, this program is full of features that may not be obvious at first glance so please be sure to look at the available help. Status ====== I've been using this tool in my own talks for over a year now, and it is fairly stable and feature complete. I've only tested it on Ubuntu so I don't know if it ports to other platforms. I'd love to hear any field reports about how it runs on other platforms. Future Directions ================= I have a long TODO list of ideas I may implement in the future, but most development has been driven by the practical considerations that I discover as I use the tool. If you have a use case for a particular feature, please let me know. ================ Feature requests, bug reports, suggestions or feedback as well as contributions to the documentation or implementation are most welcome. Michael D. Adams

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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 13 Nov '13

13 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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