July 2014 - Haskell-Cafe

Taking over setlocale
by Sven Bartscher 21 Aug '14

21 Aug '14

Greetings, I would like to take over the setlocale package. Following the steps described on http://www.haskell.org/haskellwiki/Taking_over_a_package I need to state my intention on a public forum. The original author (Lukas Mai) published his package in the Public Domain. This would be fine, but the Author seems to be living in Germany. The problem with that is that in Germany an author is not allowed to give up his copyright in this way. This means the licensing of the package defaults to "All rights reserved", making the package undistributable. I already tried to contact the author about this problem, but he didn't respond in a week. This isn't a very long time, but I didn't get an answer on past attempts to contact him (this was at least a month, but probably more, ago). To solve this problem, I rewrote the setlocale binding with the same API under the BSD3-clause. PS: Please keep the CC to Lukas Mai and the debian-haskell list intact. Regards Sven

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Bad interaction of inlinePerformIO and mutable vectors
by Michael Snoyman 03 Aug '14

03 Aug '14

I'm trying to understand why some code isn't behaving as I'd expect, and to determine whether it's a bug or not (and where that bug might be). Here's the simplest version of the code: import Data.ByteString.Internal (inlinePerformIO) import qualified Data.Vector as V import qualified Data.Vector.Mutable as VM main :: IO () main = do vm <- VM.new 1 VM.write vm 0 'A' let x = inlinePerformIO $ VM.write vm 0 'B' x `seq` (V.freeze vm >>= print) A more complete example is available on lpaste[1]. The problem is that I would expect the output to be "B", but in fact "A" is still printed. From the longer paste that I linked to, you can see that: * When using unsafePerformIO and unsafeDupablePerformIO, the semantics work as I would have expected: "B" is printed after forcing evaluation of the result. * If I add a `VM.read vm 0` call after the write, it also works. * Using IORef, the behavior is also as I would have expected: as soon as the result is evaluated, the reference is updated. I'm testing on GHC 7.8.3, Ubuntu 64-bit, and compiling with -O2. I'm curious if anyone has an idea as to why there is this difference in behavior. Michael [1] http://lpaste.net/108483

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Re: [Haskell-cafe] Tor project
by Adam Wick 02 Aug '14

02 Aug '14

Hi - Yes, we (Galois) are. The end goal is to have a Tor implementation running on a HaLVM. Right now the project is internal, but the plan is to push a basic relay node implementation out to our GitHub site sometime in the next few weeks. As for TLS, it is possible that timing attacks based on a functional language implementation could be more likely than those for a traditional C implementation. On the other hand, functional language implementations protect you from a wide variety of attacks that occur in C implementations. I don’t believe the balance has been studied, but it’d be interesting. I do know the OCaml/Mirage folks have been having good luck with their TLS implementation. I believe they’ve at least started doing some red team analysis of it, as well, with good results. See their various blog posts, starting with http://openmirage.org/blog/introducing-ocaml-tls. I’m not sure if Vincent’s library has been subject to similar evaluation, and I know the partial library in our Tor implementation has not been. - Adam Quoth: > I’ll make a question out of it: > > Is anyone working on a Haskell project compatible with Tor? Library, Server, Browser, etc. > Is anyone interested in such a project? > Would the Haskell Runtime and TLS modules have any time dependent behavior that would make encryption harder/easier to break than C implementations? Basically, is the TLS attach surface smaller or larger than openssl and is there any data to support claims of such?

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Haskell Platform 2014.2.0.0 Release Candidate 3
by Mark Lentczner 31 Jul '14

31 Jul '14

Small update to the Haskell Platfrom 2014.2.0.0 release: We have new Release Candidate 3 versions of the source tarball... and a new generic-linux bindist of the platform! - source tarball: haskell-platform-2014.2.0.0-srcdist-RC3.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-2014.2.0.0-srcdist…> - generic linux: haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz <http://www.ozonehouse.com/mark/platform/haskell-platform-2014.2.0.0-unknown…> *Windows and OS X users: There are no RC3 versions - as the RC2 versions seem to be holding up fine!* *General* - hptool (and hence ./platform.sh script) take a new --prefix parameter that is used for generic (non-OS X, non-Windows) builds: It sets the root under which haskell installations are located. Defaults to /usr/local/haskell. Everything will be placed in a directory named ghc-7.8.3-<arch> under this prefix. - activate-hs script for default Posix-like builds - small fixes to allow bootstrapping the platform with GHC 7.4 - README and LICENSE updated *Source Tarball* - all missing pieces now present - build platfrom from source tarball verified *Generic Linux Binary Dist* - Built from the GHC's generic Linux bindist for Deb 7 style systems - Complete tarball: this is all you need to install Haskell on a compatible system - Built on Ubuntu 12.04LTS - Tested on Ubuntu 14 - my system needed a symlink from libgmp.so to libgmp.so.10 - this seems to be an issue with the GHC bindist built components To install this: cd / sudo tar xvf ~/haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz sudo /usr/local/haskell/ghc-7.8.3-x8_64/bin/activate-hs This will finish the package registration, and install symlinks from /usr/local/bin for all the standard haskell command line tools. — Mark *shasum -a 256:* ab759ec50618f2604163eca7ad07e50c8292398a2d043fdc1012df161b2eb89a haskell-platform-2014.2.0.0-srcdist-RC3.tar.gz 0da6879ae657481849e7ec4e5d3c4c035e090824167f97434b48af297ec17cf9 haskell-platform-2014.2.0.0-unknown-linux-x86_64-RC3.tar.gz

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[ANN] hsimport 0.5: configurable pretty printing and placing of imports
by Daniel Trstenjak 31 Jul '14

31 Jul '14

Hi all, hsimport[1] is a command line program for extending the import list of a Haskell source file. There's an integration[2] for the vim editor, which can automatically extend the import list for the symbol under the cursor. hsimport 0.5 changes: - configurable[3] pretty printing of imports - configurable placing of new imports - support of multi line imports - better handling of incomplete/invalid Haskell source files Grettings, Daniel [1] https://github.com/dan-t/hsimport [2] https://github.com/dan-t/vim-hsimport [3] https://github.com/dan-t/hsimport/blob/master/README.md

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Tor project
by Vasili I. Galchin 31 Jul '14

31 Jul '14

Haskell contributions to http://www.torproject.org .. .any thoughts ??

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Intuition to understand poor man's concurrency
by martin 31 Jul '14

31 Jul '14

Hello all, I am trying to understand the ideas of Koen Klaessen, published in Functional Pearls: "A poor man's concurrency" (1993). The code in the paper doesn't compile. E.g. uses "lambda dot" instead of "labmda arrow", i.e. the way the labmda calculus guys write things. Was that ever legal haskell or is this the result of some lhs2lex pretty printer? Anyways, I believe I was able to convert that into modern haskell syntax - at least it compiles. But I have trouble to understand the Monad instance presented there. Could anyobody walk me through the bind function? But even more important: how do you guys develop an intuition about what the bind operator does in a specific monad. I saw a Google tech talk where Douglas Crockford explains mondads in terms of Objects in javascript (https://www.youtube.com/watch?v=b0EF0VTs9Dc) which was certainly enlightening, but I couldn't apply it to this particular modad. I also tried using something like Data Flow Diagrams. This kinda works for simple Mondads such as the state mondad, but I couldn't apply it to the concurrency mondad. In general DFDs are not very good when it comes to higher order functions. In any case here is the code. I made it more verbose than necessary in order to understand it (bind was originally just one line), but to no avail. newtype C m a = C ((a -> Action m) -> Action m) instance Monad m => Monad (C m) where (C m) >>= k = C cont where cont c = m (\a -> let C h = k a in h c) return x = C $ \c -> c x data Action m = Atom (m (Action m)) | Fork (Action m) (Action m) | Stop

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Newtype derivation understanding problem
by Konstantine Rybnikov 31 Jul '14

31 Jul '14

Excuse me if the question is silly. Thought this MonadCatchIO will be removed in next version of snap, current version has it and I can't understand this derivation: [0] L.Lensed seems like just a newtype wrapper around a function [1], and there is no instance of MonadCatchIO for a function. How is it derived? [0]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Intern… [1]: https://github.com/snapframework/snap/blob/0.13.2.8/src/Snap/Snaplet/Intern…

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Haskell Weekly News: Issue 300
by Daniel Santa Cruz 31 Jul '14

31 Jul '14

Welcome to issue 300 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from July 13 to 26, 2014 Looks like we are chuck-full of goodies this time around! Enjoy! Quotes of the Week * Cale: Functions aren't monads, the type constructor (->) e is a monad * glguy: There's no achievement for using all the operators * benmachine: adoption by lots of people may stunt progress of haskell, but it will probably help the progress of people Top Reddit Stories * Somehow, this happened. Haskell Ryan Gosling. Domain: haskellryangosling.tumblr.com, Score: 144, Comments: 31 Original: [1] http://goo.gl/IQ2f3s On Reddit: [2] http://goo.gl/H24aRa * Papers every haskeller should read Domain: self.haskell, Score: 104, Comments: 35 Original: [3] http://goo.gl/R7uGSB On Reddit: [4] http://goo.gl/R7uGSB * Strict Language Pragma Proposal Domain: ghc.haskell.org, Score: 86, Comments: 95 Original: [5] http://goo.gl/Yq28yt On Reddit: [6] http://goo.gl/BlmXpA * Announcing engine-io and socket-io for Haskell Domain: ocharles.org.uk, Score: 81, Comments: 7 Original: [7] http://goo.gl/PGW8Y8 On Reddit: [8] http://goo.gl/IsGRGi * The Haskell Cast #8 - Ollie Charles on 24 Days of Hackage and Nix Domain: haskellcast.com, Score: 70, Comments: 12 Original: [9] http://goo.gl/jBc9bk On Reddit: [10] http://goo.gl/syhwPd * Blazing Fast HTML - Virtual DOM in Elm Domain: elm-lang.org, Score: 60, Comments: 28 Original: [11] http://goo.gl/3luwtw On Reddit: [12] http://goo.gl/88zNkZ * Idris 0.9.14 released, with updated JavaScript backend, quasiquotes, and lots of internal cleanups and improvements Domain: idris-lang.org, Score: 55, Comments: 11 Original: [13] http://goo.gl/wmW3RM On Reddit: [14] http://goo.gl/fN28z6 * hoodle 0.3 released - free pen note taking program Domain: ianwookim.org, Score: 53, Comments: 15 Original: [15] http://goo.gl/jauFC On Reddit: [16] http://goo.gl/upMnf6 * This just in, from my local GHC/Cabal checkout... (re: Cabal Hell) Domain: self.haskell, Score: 52, Comments: 13 Original: [17] http://goo.gl/tD2yOg On Reddit: [18] http://goo.gl/tD2yOg * Haskell for all: Equational reasoning at scale Domain: haskellforall.com, Score: 52, Comments: 29 Original: [19] http://goo.gl/BZtZ4R On Reddit: [20] http://goo.gl/xKxCM3 * Complete roadmap from total novice to Haskell mastery? Domain: self.haskell, Score: 50, Comments: 74 Original: [21] http://goo.gl/5y1lXA On Reddit: [22] http://goo.gl/5y1lXA * Write webservices around databases with 0 boilerplate: announcing servant 0.1 Domain: alpmestan.com, Score: 50, Comments: 16 Original: [23] http://goo.gl/vzz8aT On Reddit: [24] http://goo.gl/qTty6u * Mutable Algorithms in Immutable Languages, Part 3 Domain: tel.github.io, Score: 49, Comments: 2 Original: [25] http://goo.gl/uG5Bds On Reddit: [26] http://goo.gl/qrdk6Y * Best Practices for Avoiding Cabal Hell Domain: softwaresimply.blogspot.com, Score: 47, Comments: 13 Original: [27] http://goo.gl/OqG241 On Reddit: [28] http://goo.gl/fapyz2 * Applicative (Make) vs Monadic (Shake) build systems Domain: neilmitchell.blogspot.co.uk, Score: 47, Comments: 7 Original: [29] http://goo.gl/CPyzpd On Reddit: [30] http://goo.gl/2eW8Ed * Nemnem - Haskell source hyperlinker Domain: robinp.github.io, Score: 41, Comments: 33 Original: [31] http://goo.gl/2msbLR On Reddit: [32] http://goo.gl/R6hBOl * Let me tell you about the types of data Domain: tel.github.io, Score: 41, Comments: 51 Original: [33] http://goo.gl/ZjJelo On Reddit: [34] http://goo.gl/bbmXSW * Lens Tutorial - Introduction (part 1) Domain: blog.jakubarnold.cz, Score: 39, Comments: 11 Original: [35] http://goo.gl/yQRoPY On Reddit: [36] http://goo.gl/fnbZ0F * Help - I wrote some Haskell code, it works, but it's slower than Python. What did I do wrong? Domain: self.haskell, Score: 39, Comments: 43 Original: [37] http://goo.gl/CG13CR On Reddit: [38] http://goo.gl/CG13CR * IntrinsicSuperclasses for Haskell (new proposal for default superclass instances by Conor McBride) Domain: ghc.haskell.org, Score: 37, Comments: 10 Original: [39] http://goo.gl/vDYUQh On Reddit: [40] http://goo.gl/vZjHXS * hackage-diff: Compare the public API of different versions of a Hackage library Domain: self.haskell, Score: 37, Comments: 32 Original: [41] http://goo.gl/y682CB On Reddit: [42] http://goo.gl/y682CB * How do you avoid the Cabal Hell™? Domain: self.haskell, Score: 36, Comments: 30 Original: [43] http://goo.gl/9uS54H On Reddit: [44] http://goo.gl/9uS54H * Edward Kmett on Hask Domain: youtu.be, Score: 35, Comments: 34 Original: [45] http://goo.gl/1lfywk On Reddit: [46] http://goo.gl/D0AuFQ * Mutable Algorithms in Immutable Languages, Part 2 Domain: tel.github.io, Score: 33, Comments: 1 Original: [47] http://goo.gl/g0ylvT On Reddit: [48] http://goo.gl/jwwr87 * Multi-instance packages status report Domain: permalink.gmane.org, Score: 32, Comments: 7 Original: [49] http://goo.gl/JSPx39 On Reddit: [50] http://goo.gl/2rzPJL * Slides from Conan Elliott's workshop on Denotational Design: from meanings to programs Domain: conal.net, Score: 32, Comments: 6 Original: [51] http://goo.gl/GwO4Fv On Reddit: [52] http://goo.gl/0u9KVl * Reactive-banana anti-tutorial Domain: gelisam.blogspot.ca, Score: 31, Comments: 23 Original: [53] http://goo.gl/D7mv4X On Reddit: [54] http://goo.gl/shMY0N * Intro to Machines & Arrows Part 2: 'Auto' as Category, Applicative & Arrow, ft. locally stateful compositions; Further down the road to an Arrowized FRP implementation. Domain: blog.jle.im, Score: 28, Comments: 9 Original: [55] http://goo.gl/xkwocR On Reddit: [56] http://goo.gl/phqXn8 Top StackOverflow Questions * Examples of histomorphisms in Haskell votes: 16, answers: 2 Read on SO: [57] http://goo.gl/ZmGzI6 * Plan B, or what's the opposite of Maybe's >>=? votes: 15, answers: 2 Read on SO: [58] http://goo.gl/rYWlzQ * Let-renaming function breaks code votes: 14, answers: 2 Read on SO: [59] http://goo.gl/R9CGyL * Pattern matching on rank-2 type votes: 14, answers: 3 Read on SO: [60] http://goo.gl/s0IszK * Haskell algorithm advice and suggestions for alternate solutions votes: 14, answers: 1 Read on SO: [61] http://goo.gl/2l23N8 * Why can't Haskell be tricked into performing IO operations by using strict evaluation? votes: 14, answers: 2 Read on SO: [62] http://goo.gl/Ey9795 * How does lifting (in a functional programming context) relate to category theory? votes: 14, answers: 1 Read on SO: [63] http://goo.gl/esTTbO Until next time, [64]+Daniel Santa Cruz References 1. http://haskellryangosling.tumblr.com/ 2. http://www.reddit.com/r/haskell/comments/2avnc0/somehow_this_happened_haske… 3. http://www.reddit.com/r/haskell/comments/2blsqa/papers_every_haskeller_shou… 4. http://www.reddit.com/r/haskell/comments/2blsqa/papers_every_haskeller_shou… 5. https://ghc.haskell.org/trac/ghc/wiki/StrictPragma 6. http://www.reddit.com/r/haskell/comments/2bi69g/strict_language_pragma_prop… 7. https://ocharles.org.uk/blog/posts/2014-07-13-announcing-socket-io-for-hask… 8. http://www.reddit.com/r/haskell/comments/2aks91/announcing_engineio_and_soc… 9. http://www.haskellcast.com/episode/008-ollie-charles-on-24-days-of-hackage-… 10. http://www.reddit.com/r/haskell/comments/2bbc82/the_haskell_cast_8_ollie_ch… 11. http://elm-lang.org/blog/Blazing-Fast-Html.elm 12. http://www.reddit.com/r/haskell/comments/2bam6p/blazing_fast_html_virtual_d… 13. http://www.idris-lang.org/idris-0-9-14-released/ 14. http://www.reddit.com/r/haskell/comments/2aw6vl/idris_0914_released_with_up… 15. http://ianwookim.org/hoodle/ 16. http://www.reddit.com/r/haskell/comments/2aotln/hoodle_03_released_free_pen… 17. http://www.reddit.com/r/haskell/comments/2b7odl/this_just_in_from_my_local_… 18. http://www.reddit.com/r/haskell/comments/2b7odl/this_just_in_from_my_local_… 19. http://www.haskellforall.com/2014/07/equational-reasoning-at-scale.html 20. http://www.reddit.com/r/haskell/comments/2b7xwx/haskell_for_all_equational_… 21. http://www.reddit.com/r/haskell/comments/2ali12/complete_roadmap_from_total… 22. http://www.reddit.com/r/haskell/comments/2ali12/complete_roadmap_from_total… 23. http://alpmestan.com/posts/2014-07-26-announcing-servant.html 24. http://www.reddit.com/r/haskell/comments/2bs536/write_webservices_around_da… 25. http://tel.github.io/2014/07/15/mutable_algorithms_in_immutable_languages_p… 26. http://www.reddit.com/r/haskell/comments/2ase1q/mutable_algorithms_in_immut… 27. http://softwaresimply.blogspot.com/2014/07/haskell-best-practices-for-avoid… 28. http://www.reddit.com/r/haskell/comments/2ameew/best_practices_for_avoiding… 29. http://neilmitchell.blogspot.co.uk/2014/07/applicative-vs-monadic-build-sys… 30. http://www.reddit.com/r/haskell/comments/2blex3/applicative_make_vs_monadic… 31. http://robinp.github.io/nemnem/ 32. http://www.reddit.com/r/haskell/comments/2ata3n/nemnem_haskell_source_hyper… 33. http://tel.github.io/2014/07/23/types_of_data/ 34. http://www.reddit.com/r/haskell/comments/2bj7it/let_me_tell_you_about_the_t… 35. http://blog.jakubarnold.cz/2014/07/14/lens-tutorial-introduction-part-1.html 36. http://www.reddit.com/r/haskell/comments/2ap02f/lens_tutorial_introduction_… 37. http://www.reddit.com/r/haskell/comments/2brxwp/help_i_wrote_some_haskell_c… 38. http://www.reddit.com/r/haskell/comments/2brxwp/help_i_wrote_some_haskell_c… 39. https://ghc.haskell.org/trac/ghc/wiki/IntrinsicSuperclasses 40. http://www.reddit.com/r/haskell/comments/2avs16/intrinsicsuperclasses_for_h… 41. http://www.reddit.com/r/haskell/comments/2b5jfd/hackagediff_compare_the_pub… 42. http://www.reddit.com/r/haskell/comments/2b5jfd/hackagediff_compare_the_pub… 43. http://www.reddit.com/r/haskell/comments/2al3vx/how_do_you_avoid_the_cabal_… 44. http://www.reddit.com/r/haskell/comments/2al3vx/how_do_you_avoid_the_cabal_… 45. http://youtu.be/Klwkt9oJwg0 46. http://www.reddit.com/r/haskell/comments/2b3rk5/edward_kmett_on_hask/ 47. http://tel.github.io/2014/07/13/mutable_algorithms_in_immutable_languages_p… 48. http://www.reddit.com/r/haskell/comments/2al4cw/mutable_algorithms_in_immut… 49. http://permalink.gmane.org/gmane.comp.lang.haskell.ghc.devel/5413 50. http://www.reddit.com/r/haskell/comments/2bbys6/multiinstance_packages_stat… 51. http://conal.net/talks/lambdajam-2014.pdf 52. http://www.reddit.com/r/haskell/comments/2brioe/slides_from_conan_elliotts_… 53. http://gelisam.blogspot.ca/2014/07/reactive-banana-anti-tutorial.html 54. http://www.reddit.com/r/haskell/comments/2auswf/reactivebanana_antitutorial/ 55. http://blog.jle.im/entry/auto-as-category-applicative-arrow-intro-to-machin… 56. http://www.reddit.com/r/haskell/comments/2aot3i/intro_to_machines_arrows_pa… 57. http://stackoverflow.com/questions/24884475/examples-of-histomorphisms-in-h… 58. http://stackoverflow.com/questions/24902463/plan-b-or-whats-the-opposite-of… 59. http://stackoverflow.com/questions/24724738/let-renaming-function-breaks-co… 60. http://stackoverflow.com/questions/24744294/pattern-matching-on-rank-2-type 61. http://stackoverflow.com/questions/24748750/haskell-algorithm-advice-and-su… 62. http://stackoverflow.com/questions/24775528/why-cant-haskell-be-tricked-int… 63. http://stackoverflow.com/questions/24856963/how-does-lifting-in-a-functiona… 64. https://plus.google.com/105107667630152149014/about

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www.galois.com vs Google??
by Vasili I. Galchin 31 Jul '14

31 Jul '14

Hello Haskellers(and all FPL people), I just ran across the following effort by Google: http://blogs.techworld.com/war-on-error/2014/07/googles-project-zero-flaw-p… It seems to me that www.galois.com(www.janestreetcapital.com) realizes that the solution to software correctness problems doesn't lie with uncontrolled "mutability" ... Question: does Google concur with www.galois.com or google's effort just "more of the same"?? Vasili

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