June 2013 - Haskell-Cafe

Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 28 Jun '13

28 Jun '13

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28 Jun '13

Hi! I'm new to Haskell and I'm very interested in using it as a base layer for my application. I need to generate the LLVM-IR code from ghc compiler, so I've got 2 questuions to you: 1) Is the LLVM Backend actively developed or should I be afraid it will be discontinued or broken? 2) How can I generate the LLVM IR (or bc) files from the compiler? I see that durign compilation with -fllvm -v3 flags the bc files are created but they are immidietly (after usage) deleted - Is it possible to tell the compiler not to delete them?

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Who uses Travis CI and can help write a cookbook for those guys?
by Ryan Newton 28 Jun '13

28 Jun '13

The Travis folks have decided they want to support Haskell better (multiple compiler versions): https://github.com/travis-ci/travis-ci/issues/882#issuecomment-20165378 (Yay!) They're asking for someone to help them up with setup scripts. They mention their cookbook collection here: https://github.com/travis-ci/travis-cookbooks In that thread above, I pasted our little script that fetches and installs multiple GHC versions, but I have little experiences with cloud technologies & VMs. Can someone jump in and help push this forward? As a community I'm sure it would be great to get a higher percentage of Hackage packages using simple, hosted continuous testing... I'd personally like to replace my Jenkins install if they can get the necessary GHC versions in there. Best, -Ryan

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Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 27 Jun '13

27 Jun '13

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Job opportunities at Galois
by Iavor Diatchki 27 Jun '13

27 Jun '13

Hello, Galois is hiring! We're looking for researchers, principal investigators, and software engineers, including those with expertise in functional programming, formal methods, computer security, control systems, informatics, or networking. For more information, take a look at http://corp.galois.com/careers and please feel free to drop me an e-mail if you have questions. Cheers, -Iavor

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Re: [Haskell-cafe] LLVM Backend status
by JP＠eukor.com 27 Jun '13

27 Jun '13

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Going to speak about Haskell at Flock to Fedora
by Garrett Mitchener 27 Jun '13

27 Jun '13

(Sorry if you get this twice, I had some trouble with google groups and the mailing list...) Hi, Red Hat is holding a conference called Flock to Fedora<http://flocktofedora.com/> in Charleston, SC, and I'm going to be speaking about Haskell: http://sched.co/14twxPj I'm planning to introduce the language, touch a few interesting packages, and show how to use GHC on Fedora. If anyone from the Haskell community is going to Flock and has requests or suggestions for what I should talk about, post a reply! -- Garrett Mitchener, associate professor of mathematics, College of Charleston, SC

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Haskell Weekly News: Issue 271
by Daniel Santa Cruz 26 Jun '13

26 Jun '13

Welcome to issue 271 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of June 9 to 11, 2013. Quotes of the Week * cmccann: also please note that "malign" remains one of my best function names ever * dolio: Peak file descriptors is a myth. * mami: i think my brain rewired for higher typesystem compatibility in my sleep * elliott: it's impure but only depending on the environment! which is to say it is impure. * johnw: lens makes one into a mutating ninja * applicativ: een my language we say Z for one * DavidJacobs: Code is like poetry; most of it shouldn't have been written. * merijn: If I could program with arbitrary real world side effects I'd use "unsafeStabComputerUser" if someone attempted that * shachaf: Hackage going down regularly is part of the rustic charm of Haskell! * shachaf: JavaScript is the best example of a domain-specific language. Because of the same-origin policy. * chrisdone: [on being invited to help with idris development] dude i've already got 20 yaks lined up waiting to be shaved, don't send me a whole truck full * shachaf: edwardk isn't benevolent or malevolent. edwardk is more of a simple mechanical process tending toward maximal complexity. * AndrejBauer: When have you ever heard a category theorist say: I want to prove this diagram commutesâLet's suppose it doesn't. Top Reddit Stories * Applicative => Monad is coming. Domain: haskell.org, Score: 122, Comments: 62 On Reddit: [1] http://goo.gl/JCvQ4 Original: [2] http://goo.gl/fJxeX * The Homotopy Type Theory Book is now available for free online and in print at Lulu.com Domain: homotopytypetheory.org, Score: 86, Comments: 16 On Reddit: [3] http://goo.gl/x8nLW Original: [4] http://goo.gl/DR9gf * Three useful monads Domain: adit.io, Score: 71, Comments: 25 On Reddit: [5] http://goo.gl/WHqPr Original: [6] http://goo.gl/1r8nC * Beta sign up for FP Complete new IDE Domain: fpcomplete.com, Score: 63, Comments: 11 On Reddit: [7] http://goo.gl/RPV0P Original: [8] http://goo.gl/c03Od * HLearn implements more with 6 trivial lines of Haskell than Weka implements with over 100 complex lines of Java Domain: izbicki.me, Score: 47, Comments: 9 On Reddit: [9] http://goo.gl/EEqwS Original: [10] http://goo.gl/Ukk4E * Top secret School of Haskell articles leaked Domain: self.haskell, Score: 47, Comments: 17 On Reddit: [11] http://goo.gl/zhhYm Original: [12] http://goo.gl/zhhYm * F-algebra tutorial Domain: fpcomplete.com, Score: 41, Comments: 35 On Reddit: [13] http://goo.gl/Ybmbs Original: [14] http://goo.gl/szfGk * John Carmack on haskell today. Domain: self.haskell, Score: 40, Comments: 79 On Reddit: [15] http://goo.gl/8qHkt Original: [16] http://goo.gl/8qHkt * Data Flow Fusion with Series Expressions in Haskell Domain: justtesting.org, Score: 40, Comments: 19 On Reddit: [17] http://goo.gl/ZNeIP Original: [18] http://goo.gl/JAjjy * So you still don't understand Hindley-Milner? Part 1 Domain: akgupta.ca, Score: 38, Comments: 0 On Reddit: [19] http://goo.gl/OOk43 Original: [20] http://goo.gl/SZ1Gb * Ask HN: Any downsides of programming in Haskell? Domain: news.ycombinator.com, Score: 36, Comments: 104 On Reddit: [21] http://goo.gl/vRuHW Original: [22] http://goo.gl/fcleS * FP Complete - Haskell Introduction Domain: youtube.com, Score: 36, Comments: 12 On Reddit: [23] http://goo.gl/GqgC5 Original: [24] http://goo.gl/KoVYs * Fix your posture with haskell Domain: github.com, Score: 35, Comments: 2 On Reddit: [25] http://goo.gl/lznTr Original: [26] http://goo.gl/x21Ax * preprint list for ICFP'13 papers (additional links welcome) Domain: github.com, Score: 34, Comments: 9 On Reddit: [27] http://goo.gl/mZsTn Original: [28] http://goo.gl/bhbC9 * GHC: now with closed type families Domain: github.com, Score: 34, Comments: 15 On Reddit: [29] http://goo.gl/JJSSv Original: [30] http://goo.gl/QlV4s Top StackOverflow Questions * How to compare two functions for equivalence, as in (λx.2*x) == (λx.x+x)? votes: 15, answers: 2 Read on SO: [31] http://goo.gl/A6YDd * Should I use typeclasses or not? votes: 15, answers: 2 Read on SO: [32] http://goo.gl/EOV1M * Is there something like `map2 :: (i -> a) -> (i -> b) -> [i] -> [(a,b)]`? votes: 11, answers: 2 Read on SO: [33] http://goo.gl/WZyEy * Why isn't GeneralizedNewtypeDeriving a Safe Haskell? votes: 11, answers: 1 Read on SO: [34] http://goo.gl/on6Fc * It's not a monad, but what is it? votes: 10, answers: 0 Read on SO: [35] http://goo.gl/sm9gR * Writing efficient iterative loop for ST monad votes: 10, answers: 0 Read on SO: [36] http://goo.gl/WAAwA * Getting multiple results from map with “lens” votes: 10, answers: 2 Read on SO: [37] http://goo.gl/zqX8E * How to run Frege programs on Android? votes: 10, answers: 2 Read on SO: [38] http://goo.gl/XlSCN * Are there problems that can't be solved efficiently without arrays? [duplicate] votes: 9, answers: 0 Read on SO: [39] http://goo.gl/Z5j9a * Haskell: How to organize a group of functions that all take the same arguments votes: 9, answers: 4 Read on SO: [40] http://goo.gl/z64H7 Until next time, [41]+Daniel Santa Cruz References 1. http://www.haskell.org/haskellwiki/Functor-Applicative-Monad_Proposal 2. http://www.reddit.com/r/haskell/comments/1gsejt/applicative_monad_is_coming/ 3. http://homotopytypetheory.org/book/ 4. http://www.reddit.com/r/haskell/comments/1gr3uw/the_homotopy_type_theory_bo… 5. http://adit.io/posts/2013-06-10-three-useful-monads.html 6. http://www.reddit.com/r/haskell/comments/1g3a7e/three_useful_monads/ 7. https://www.fpcomplete.com/blog/2013/06/beta-sign-up 8. http://www.reddit.com/r/haskell/comments/1giy7l/beta_sign_up_for_fp_complet… 9. http://izbicki.me/blog/hlearns-code-is-shorter-and-clearer-than-wekas 10. http://www.reddit.com/r/haskell/comments/1g4v7u/hlearn_implements_more_with… 11. http://www.reddit.com/r/haskell/comments/1g5k80/top_secret_school_of_haskel… 12. http://www.reddit.com/r/haskell/comments/1g5k80/top_secret_school_of_haskel… 13. https://www.fpcomplete.com/user/bartosz/understanding-algebras 14. http://www.reddit.com/r/haskell/comments/1g2g3s/falgebra_tutorial/ 15. http://www.reddit.com/r/haskell/comments/1g1mvx/john_carmack_on_haskell_tod… 16. http://www.reddit.com/r/haskell/comments/1g1mvx/john_carmack_on_haskell_tod… 17. http://justtesting.org/post/53175916852/data-flow-fusion-with-series-expres… 18. http://www.reddit.com/r/haskell/comments/1gi5m1/data_flow_fusion_with_serie… 19. http://akgupta.ca/blog/2013/05/14/so-you-still-dont-understand-hindley-miln… 20. http://www.reddit.com/r/haskell/comments/1g0ueo/so_you_still_dont_understan… 21. https://news.ycombinator.com/item?id=5893442 22. http://www.reddit.com/r/haskell/comments/1gknfs/ask_hn_any_downsides_of_pro… 23. https://www.youtube.com/watch?v=Fqi0Xu2Enaw 24. http://www.reddit.com/r/haskell/comments/1glw2o/fp_complete_haskell_introdu… 25. https://github.com/keera-studios/keera-posture 26. http://www.reddit.com/r/haskell/comments/1gr044/fix_your_posture_with_haske… 27. https://github.com/gasche/icfp2013-papers#readme 28. http://www.reddit.com/r/haskell/comments/1gg2xf/preprint_list_for_icfp13_pa… 29. https://github.com/ghc/ghc/commit/569b26526403df4d88fe2a6d64c7dade09d003ad 30. http://www.reddit.com/r/haskell/comments/1gu2yl/ghc_now_with_closed_type_fa… 31. http://stackoverflow.com/questions/17045941/how-to-compare-two-functions-fo… 32. http://stackoverflow.com/questions/17100036/should-i-use-typeclasses-or-not 33. http://stackoverflow.com/questions/17074424/is-there-something-like-map2-i-… 34. http://stackoverflow.com/questions/17137111/why-isnt-generalizednewtypederi… 35. http://stackoverflow.com/questions/17034427/its-not-a-monad-but-what-is-it 36. http://stackoverflow.com/questions/17126923/writing-efficient-iterative-loo… 37. http://stackoverflow.com/questions/17144334/getting-multiple-results-from-m… 38. http://stackoverflow.com/questions/17222383/how-to-run-frege-programs-on-an… 39. http://stackoverflow.com/questions/17128103/are-there-problems-that-cant-be… 40. http://stackoverflow.com/questions/17176829/haskell-how-to-organize-a-group… 41. https://plus.google.com/105107667630152149014/about

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homotopy type theory for amateurs
by Ben 26 Jun '13

26 Jun '13

hello cafe -- by now i'm sure you have heard that the homotopy type theory folks have just written up a free introductory book on their project. http://homotopytypetheory.org/2013/06/20/the-hott-book/ gabriel gonzalez and i are starting up a small reading group for the book. the level of study will be "amateur", though i have high hopes for rigor and thoroughness. personally, i know hardly any type theory or logic, and the last time i thought about homotopy theory in any seriousness was years ago. thankfully the book looks very accessible. being time-constrained we were going to do it mostly over email, maybe starting a google group or other mailing list, but we might meet as well, say once a month in san francisco (where we both are.) if you're interested in joining us, send me an email (midfield at gmail) and i'll try to keep you informed of any developments. best, ben

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Geometric Algebra [Was: writing a function to make a correspondance between type-level integers and value-level integers]
by oleg＠okmij.org 26 Jun '13

26 Jun '13

> It seems very interesting, but I have not currently the time to make a > detailed comparison with vector/tensor algebra. Moreover I have not I would suggest the freely available Oersted Medal Lecture 2002 by David Hestenes http://geocalc.clas.asu.edu/pdf/OerstedMedalLecture.pdf the person who discovered and developed the Geometric Algebra. In particular, see Section V of the above paper. It talks about vectors, geometric products, the coordinate-free representation for `vector product' and the geometric meaning of the imaginary unit i. Section 1 gives a good motivation for the Geometric Algebra. Other sections of the paper develop physical applications, from classical mechanics to electrodynamics to non-relativistic and relativistic quantum mechanics. Computer Scientists might then like http://www.geometricalgebra.net/ see the good and free introduction http://www.geometricalgebra.net/downloads/ga4cs_chapter1.pdf Incidentally, David Hestenes said in the lecture that he has applied for an NSF grant to work on Geometric Algebra TWELVE times in a row, and was rejected every single time.

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