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Cross compiling Haskell from Linux to Windows with GHCs LLVM backend?
by Rob Stewart 13 Jun '14

13 Jun '14

Hi, I compile my code with GHC on Linux, and don't have ready access to a Windows or a Mac operating system. Is it possible to use the GHC LLVM backend as a means to cross compile Haskell code to target multiple operating systems? I had envisaged it possible to generate the LLVM IR using GHCs -keep-llvm-files flag, and using LLVMs target triple flag to specify the CPU architecture and operating system of the users machine. I'd like to compile on Linux, to target WIndows and Mac machines. Strangely I cannot find blog posts or tutorials online for cross-compiling Haskell with GHC via LLVM. Is it possible? Thanks, -- Rob

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Re: [Haskell-cafe] [Haskell] ANN: io-memoize 1.1
by Kim-Ee Yeoh 13 Jun '14

13 Jun '14

On Thu, Jun 12, 2014 at 4:47 PM, Dan Burton <danburton.email(a)gmail.com> wrote: > Have you ever wanted to restrict an IO action such that it could only be > invoked once? Now you can with System.IO.Memoize.once (formerly known as > ioMemo). > (Moving to cafe for dicussion ...) I may want a one-time only IO action, although so far the need hasn't arisen yet. ;) In the spirit of pilfering while the buns are still hot out of the oven, is there a backstory for this package you could possibly sketch out? Some canonical use case maybe? -- Kim-Ee

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Opening for OpenGL, C++ Development.
by Manoj Chaudhari 12 Jun '14

12 Jun '14

Hello, We are looking for Software Developers with OpenGL experience. - Should have experience in C++/Xcode, OpenGL/DirectX/IOS. - Experience with Shafer programming, Multi-threaded applications, Graphics in CAD domain. - The role is of Software Development on primary CAD application like CATIA. - Good skills in Geometry, algorithms, Mathematics, API's, Graphics-will be a added advantage. Experience : 2 to 6 years. If anyone is interested on learning more about this opportunity and potential salary ranges, please email me at : manoj_chaudhari2(a)3dplmsoftware.com Regards, Manoj Chaudhari

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Troubles installing EclipseFP
by Vagif Verdi 12 Jun '14

12 Jun '14

Hi, i'm trying to install eclipsefp. Ubuntu 14.04, ghc 7.6.3, cabal-install 1.20. I did it with a fresh .cabal and .ghc folders. Nothing else was installed. After restarting eclipse it started doenloading and building haskell libs, and stopped with this error: Cabal==1.16.0/installed-c6e..., SourceGraph => Cabal<1.7) rejecting: SourceGraph-0.2, 0.1 (conflict: buildwrapper => Cabal==1.16.0/installed-c6e..., SourceGraph => Cabal<1.5) Backjump limit reached (change with --max-backjumps). Note: when using a sandbox, all packages are required to have consistent dependencies. Try reinstalling/unregistering the offending packages or recreating the sandbox.

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ghc-options: -dynamic in package refused by Hackage
by JP Moresmau 12 Jun '14

12 Jun '14

Hello, what's the recommended way to make a package dynamic? 1. I need to make the executable in my package dynamic otherwise I run into https://ghc.haskell.org/trac/ghc/ticket/8376 2. I've set ghc-options: -dynamic in my Cabal file and that solves my issues. 3. I can't upload my package to Hackage, I get a "'ghc-options: -d*' debug flags are not appropriate for a distributed package" error. I hadn't realized -dynamic is for debugging purposes... So is there another way to make my package dynamic and uploadable to Hackage? Or should I just not put the flag in the cabal flag and let my users pass the flag when they install? Thanks! JP -- JP Moresmau http://jpmoresmau.blogspot.com/

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Simple but slow, and complex but fast Forth emulation [Was: Bang, a drum DSL for Haskell]
by oleg＠okmij.org 12 Jun '14

12 Jun '14

Emulation of a simple subset of Forth in Haskell seems easy. The trick, continuation-passing style, has been known for a long time. The trick underlies `functional unparsing' by Olivier Danvy. http://www.brics.dk/RS/98/12/BRICS-RS-98-12.pdf (published in JFP in 1998). Chris Okasaki later extended the technique http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.121.1890 http://dl.acm.org/citation.cfm?id=581699 He also noted huge types and slow compilation times. But there is another way. It is far more complex, and far fast. It is used in HSXML, which handles polyvariadic functions with literally thousands of arguments (some of my web pages are long). The following complete code illustrates the idea. {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE FlexibleInstances, FlexibleContexts #-} {-# LANGUAGE TypeFamilies #-} -- Simple Forth module SimpleForth where -- The simple way: Danvy's Functional unparsing begin k = k () n st x k = k ((x::Int),st) add (n1,(n2,st)) k = k (n1+n2,st) end (top,st) = top t1 = begin n 1 n 2 add end -- Uncomment the following to get a hint why t2 is too slow -- t1 = begin _h n 1 n 2 add end -- Uncomment the following only if you are prepared to wait {- t2 = begin n 1 n 2 n 3 n 4 n 5 n 6 n 7 n 8 n 9 add add add add add add add add end -} -- A more complex but faster way -- Start with a stack 'stack' and then continue class Forth stack r where build :: stack -> r data End = End instance (a ~ stack) => Forth stack (End -> a) where build stack _ = stack data Add = Add -- Start with (Int, (Int, stack)), see Add and continue with (Int,stack) instance Forth (Int,stack) r => Forth (Int,(Int,stack)) (Add -> r) where build (n1,(n2,stack)) _ = build (n1+n2,stack) data N = N instance (a ~ Int, Forth (Int,stack) r) => Forth stack (N -> a -> r) where build stack _ n = build (n,stack) -- All of the following typecheck instantaneously, even on my slow -- laptop tt1 = build () N 1 N 2 Add End tt2 = build () N 1 N 2 N 3 N 4 N 5 N 6 N 7 N 8 N 9 Add Add Add Add Add Add Add Add End tt3 = build () N 1 N 2 Add N 3 Add N 4 Add N 5 Add N 6 Add N 7 Add N 8 Add N 9 Add End

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Deleting mailing list
by Jürgen Nicklisch-Franken 12 Jun '14

12 Jun '14

I want to delete the mailman mailing list for leksah (leksah(a)projects.haskell.org.) since it is not used anymore and only collects spam. It looks as I can't do this on my own, so I need help. My mails to support(a)community.haskell.org didn't produce any response. So I try this for years now. Please! Is someone out there that can help me? Kind regards Jürgen Nicklisch-Franken

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Unable to make a HList-like to deal with Kleisli Arrows and State
by Gautier DI FOLCO 12 Jun '14

12 Jun '14

Hi all, My goal is to compose Kleisli arrows with (State s) as parameteric Monadic type. So, I end up with the following code: data REnv :: [*] -> * -> * -> (* -> * -> *) -> ((* -> *) -> * -> * -> *) -> * where Last :: k (s t) i o -> REnv (t ': '[]) i o s k RCons :: k (s t) i o' -> REnv ts o' o s k -> REnv (t ': ts) i o s k Which, of course, gives me the following error when I try to play with it: *H> :t Last genRanking <interactive>:1:6: Kind incompatibility when matching types: s :: * -> * -> * StateT Ranking :: (* -> *) -> * -> * Expected type: Kleisli (s t) Ticket Ranking Actual type: Kleisli (State Ranking) Ticket Ranking In the first argument of ‘Last’, namely ‘genRanking’ In the expression: Last genRanking <interactive>:1:6: Kind incompatibility when matching types: t :: * Data.Functor.Identity.Identity :: * -> * Expected type: Kleisli (s t) Ticket Ranking Actual type: Kleisli (State Ranking) Ticket Ranking In the first argument of ‘Last’, namely ‘genRanking’ In the expression: Last genRanking*H> :t LastLast :: k (s t) i o -> REnv '[t] i o s k*H> :t genRanking genRanking :: Kleisli (State Ranking) Ticket Ranking I understand why it fails (State is * -> * -> *, while s is * -> *), but I can't figure out how to write this, I tried (s t o), but it isn't correct because k waits for a (* -> *). If you have any ideas, I'm curious to read them. Thanks in advance for your help.

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Re: [Haskell-cafe] 自动回复： HP's "The Machine"
by Vasili I. Galchin 12 Jun '14

12 Jun '14

2014-06-11 23:26 GMT-05:00 <zhangliu529(a)sina.com>: > 您发的邮件我已收到，我将尽快给您答复。 I too speak/read Chinese .. we can share info :-)

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HP's "The Machine"
by Vasili I. Galchin 12 Jun '14

12 Jun '14

a google of "The Machine" ... https://www.google.com/search?q=HP+%22The+Machine%22&ie=utf-8&oe=utf-8&aq=t… Let's assume this paradigm actually will work, what are the implications for FPLs in general and Haskell in particular?? Regards, Vasili

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Haskell Weekly News: Issue 296
by Daniel Santa Cruz 12 Jun '14

12 Jun '14

Welcome to issue 296 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from May 25 to June 7, 2014 Quotes of the Week * mbrock: then you get into a whole thing about the epistemology of abstract algebra, and someone brings up Wittgenstein, somebody brings out a bottle of wine, and it's yet another one of those nights Top Reddit Stories * An alternative Haskell home page Domain: chrisdone.com, Score: 160, Comments: 57 Original: [1] http://goo.gl/Yw2G3a On Reddit: [2] http://goo.gl/m19Ujx * Third generation of the attoparsec parsing library Domain: serpentine.com, Score: 82, Comments: 22 Original: [3] http://goo.gl/kk8i50 On Reddit: [4] http://goo.gl/LZzevb * Music-Suite Domain: music-suite.github.io, Score: 81, Comments: 44 Original: [5] http://goo.gl/u69ybm On Reddit: [6] http://goo.gl/EYKMwI * Erik Meijer: Introduction to Functional Programming Domain: edx.org, Score: 79, Comments: 11 Original: [7] http://goo.gl/YrfbA3 On Reddit: [8] http://goo.gl/oLRm6k * The abject failure of weak typing Domain: techblog.realestate.com.au, Score: 72, Comments: 28 Original: [9] http://goo.gl/h5XDVZ On Reddit: [10] http://goo.gl/nfnLNN * Lazy Dynamic Programming Domain: jelv.is, Score: 64, Comments: 12 Original: [11] http://goo.gl/kdSbkh On Reddit: [12] http://goo.gl/I6XVa8 * First Person 3D Navigation, written in Elm Domain: github.com, Score: 62, Comments: 0 Original: [13] http://goo.gl/qLM3FD On Reddit: [14] http://goo.gl/CRNW6M * Haskell Platform Redesign Domain: self.haskell, Score: 57, Comments: 39 Original: [15] http://goo.gl/A2OqV4 On Reddit: [16] http://goo.gl/A2OqV4 * Benjamin Pierce on clean-slate security architectures Domain: intelligence.org, Score: 54, Comments: 2 Original: [17] http://goo.gl/dCWGlr On Reddit: [18] http://goo.gl/ns7SF6 * Idris 0.9.13 released, featuring a new erasure implementation, Haddock- and Hoogle-inspired tools, and improved IDE support Domain: idris-lang.org, Score: 53, Comments: 6 Original: [19] http://goo.gl/rf9i2U On Reddit: [20] http://goo.gl/tByoYR * Brilliant explanation of Free Monad + Interpreter pattern. Domain: programmers.stackexchange.com, Score: 52, Comments: 16 Original: [21] http://goo.gl/5wVfG1 On Reddit: [22] http://goo.gl/bCb0tD * I got lenses in my Functor Domain: izbicki.me, Score: 52, Comments: 35 Original: [23] http://goo.gl/9xAo4g On Reddit: [24] http://goo.gl/kZBcK8 * The GHC Runtime System [pdf] Domain: scs.stanford.edu, Score: 50, Comments: 15 Original: [25] http://goo.gl/J2iH4W On Reddit: [26] http://goo.gl/B2AiSo * The typeparams library provides a lens-like interface for type level parameters; it allows unboxing unboxed vectors (with benchmarks indicating a 25% performance gain) and supercompilation-like optimizations (with benchmarks showing 40x performance gain in some cases) Domain: github.com, Score: 49, Comments: 14 Original: [27] http://goo.gl/jzIn2E On Reddit: [28] http://goo.gl/fdiRHU * LiquidHaskell: Pointers Gone Wild Domain: goto.ucsd.edu, Score: 48, Comments: 16 Original: [29] http://goo.gl/aKyRnQ On Reddit: [30] http://goo.gl/pexvtf * Sed implementation in Haskell - Episode 6 [youtube] Domain: youtube.com, Score: 45, Comments: 5 Original: [31] http://goo.gl/JQ2ONf On Reddit: [32] http://goo.gl/vLQWVJ * Call Arity [pdf]: A new analysis implemented in GHC Domain: joachim-breitner.de, Score: 44, Comments: 6 Original: [33] http://goo.gl/BdEFfs On Reddit: [34] http://goo.gl/OSv5Rb Top StackOverflow Questions * Understanding Haskell's Bool Deriving an Ord votes: 17, answers: 2 Read on SO: [35] http://goo.gl/7W9WRb * Precise flow control in Haskell votes: 14, answers: 0 Read on SO: [36] http://goo.gl/uoA9i1 * Why aren't there existentially quantified type variables in GHC Haskell votes: 14, answers: 2 Read on SO: [37] http://goo.gl/ZeBJTK * Is the concept of an “interleaved homomorphism” a real thing? votes: 14, answers: 3 Read on SO: [38] http://goo.gl/gpIH6b * Is it possible to get `-=` working with literals? votes: 12, answers: 1 Read on SO: [39] http://goo.gl/R40i7q * How much overhead does sparking incur? votes: 11, answers: 1 Read on SO: [40] http://goo.gl/ixWkKL Until next time, [41]+Daniel Santa Cruz References 1. http://chrisdone.com/posts/haskell-lang 2. http://www.reddit.com/r/haskell/comments/26rilp/an_alternative_haskell_home… 3. http://www.serpentine.com/blog/2014/05/31/attoparsec/ 4. http://www.reddit.com/r/haskell/comments/26xyah/third_generation_of_the_att… 5. http://music-suite.github.io/docs/ref/ 6. http://www.reddit.com/r/haskell/comments/27djwy/musicsuite/ 7. https://www.edx.org/course/delftx/delftx-fp101x-introduction-functional-2126 8. http://www.reddit.com/r/haskell/comments/27bnt7/erik_meijer_introduction_to… 9. http://techblog.realestate.com.au/the-abject-failure-of-weak-typing/ 10. http://www.reddit.com/r/haskell/comments/26pi5b/the_abject_failure_of_weak_… 11. http://jelv.is/blog/Lazy-Dynamic-Programming 12. http://www.reddit.com/r/haskell/comments/26jh2w/lazy_dynamic_programming/ 13. https://github.com/evancz/first-person-elm#first-person-3d-navigation-in-elm 14. http://www.reddit.com/r/haskell/comments/26mjak/first_person_3d_navigation_… 15. http://www.reddit.com/r/haskell/comments/26g9y8/haskell_platform_redesign/ 16. http://www.reddit.com/r/haskell/comments/26g9y8/haskell_platform_redesign/ 17. http://intelligence.org/2014/05/11/benjamin-pierce/ 18. http://www.reddit.com/r/haskell/comments/274k69/benjamin_pierce_on_cleansla… 19. http://www.idris-lang.org/idris-0-9-13-released/ 20. http://www.reddit.com/r/haskell/comments/279wl7/idris_0913_released_featuri… 21. http://programmers.stackexchange.com/questions/242795/what-is-the-free-mona… 22. http://www.reddit.com/r/haskell/comments/2788cw/brilliant_explanation_of_fr… 23. http://izbicki.me/blog/i-got-lenses-in-my-functors 24. http://www.reddit.com/r/haskell/comments/27h0wk/i_got_lenses_in_my_functor/ 25. http://www.scs.stanford.edu/14sp-cs240h/slides/ghc-rts.pdf 26. http://www.reddit.com/r/haskell/comments/26qshw/the_ghc_runtime_system_pdf/ 27. https://github.com/mikeizbicki/typeparams#the-typeparams-library 28. http://www.reddit.com/r/haskell/comments/27avw8/the_typeparams_library_prov… 29. http://goto.ucsd.edu/~rjhala/liquid/haskell/blog/blog/2014/05/28/pointers-g… 30. http://www.reddit.com/r/haskell/comments/26redl/liquidhaskell_pointers_gone… 31. https://www.youtube.com/watch?v=GKRjVITL_oA 32. http://www.reddit.com/r/haskell/comments/26th92/sed_implementation_in_haske… 33. http://www.joachim-breitner.de/publications/CallArity-TFP.pdf 34. http://www.reddit.com/r/haskell/comments/26fdxq/call_arity_pdf_a_new_analys… 35. http://stackoverflow.com/questions/23880626/understanding-haskells-bool-der… 36. http://stackoverflow.com/questions/23869547/precise-flow-control-in-haskell 37. http://stackoverflow.com/questions/23940487/why-arent-there-existentially-q… 38. http://stackoverflow.com/questions/24090758/is-the-concept-of-an-interleave… 39. http://stackoverflow.com/questions/23875471/is-it-possible-to-get-working-w… 40. http://stackoverflow.com/questions/23877737/how-much-overhead-does-sparking… 41. https://plus.google.com/105107667630152149014/about

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Announcement: Bang, a drum DSL for Haskell
by Benjamin J Kovach 11 Jun '14

11 Jun '14

Hi haskell-cafe, I've been working on "Bang" on and off for about a month or two now, and finally thought it was "good enough" to open-source and show to the public! I've been having fun with it, and hopefully some of you will, too. It currently supports basically all of the primitive transformations that I could think of doing on a drum sequence, such as reversing, mirroring, changing duration and tempo. There are a bunch of operators built in that make it easy to write things like polyrhythms, and infinite sequences of notes are possible as well. The source code and basic tutorial are up on Github: https://github.com/5outh/Bang And the package + more detailed documentation is up on Hackage: http://hackage.haskell.org/package/Bang Let me know if you have any questions, comments, and/or suggestions. I'd love to hear them. Thanks! 5outh?

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Re: [Haskell-cafe] Deploy Haskell application
by Corentin Dupont 11 Jun '14

11 Jun '14

Hi, it seems that 'cabal configure' fails if some dependencies are missing. Then cabal copy complains that I should run 'cabal configure' first... On Wed, Jun 11, 2014 at 4:23 PM, Tom Feron <tho.feron(a)gmail.com> wrote: > Hi Corentin, > > I think you're searching for `cabal configure && cabal copy`. It will > still have an exit code of 1 if you don't compile anything but it will copy > the files from data-files (and alike). > > On my machine, it copies share/index.html into > .cabal-sandbox/share/x86_64-openbsd-ghc-7.6.3/dummy-0.1.0.0/share/index.html. > > Tom > > > On 11 June 2014 16:00, Corentin Dupont <corentin.dupont(a)gmail.com> wrote: > >> In the .cabal file you can put a directive "data-files" and they will be >> deployed in ~/.cabal/share... >> I want to trigger only this. >> >> >> On Wed, Jun 11, 2014 at 3:40 PM, Tom Nielsen <tanielsen(a)gmail.com> wrote: >> >>> Not sure what you mean - cabal doesn't do any deployment, or at least I >>> have not found a useful way of making it do so. In our case the deployment >>> is done by running apt-get update && apt-get install on the server. >>> >>> Tom >>> >>> >>> >>> >>> On Wed, Jun 11, 2014 at 3:18 PM, Corentin Dupont < >>> corentin.dupont(a)gmail.com> wrote: >>> >>>> Thanks for your response! >>>> Is there a way to ask Cabal to just deploy the resources and not >>>> compile everything? >>>> >>>> >>>> >>>> On Wed, Jun 11, 2014 at 11:47 AM, Tom Nielsen <tanielsen(a)gmail.com> >>>> wrote: >>>> >>>>> We package up the executables and other files into a Debain .deb >>>>> package using fpm after running cabal. Here is an example Makefile which >>>>> runs cabal, creates the debian package and adds it to our apt server: >>>>> >>>>> https://github.com/openbrainsrc/debcd/blob/master/Makefile >>>>> >>>>> This is run by our CI server after every commit to GitHub. >>>>> >>>>> Tom >>>>> >>>>> >>>>> On Wed, Jun 11, 2014 at 11:33 AM, Vo Minh Thu <noteed(a)gmail.com> >>>>> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> These days, an increasingly popular solution to package an application >>>>>> with its dependencies is to use Docker. You can build the Docker image >>>>>> locally and push it to a Docker registry and retrieve it on your >>>>>> remote machine, or you can dump it as a tarball and load it on your >>>>>> remote machine. >>>>>> >>>>>> You have different ways to create the Docker image, one of which would >>>>>> be similar to pushing your Haskell binary to your remote machine. That >>>>>> way is simply to compile your exectuable locally, and copy it to the >>>>>> remote machine with is assets if any (you might even move it to a >>>>>> .cabal directory as if it was installed through `cabal install`). By >>>>>> default your executable will be statically linked, except for libgmp >>>>>> that you have to install on the remote machine. >>>>>> >>>>>> I recommand you look into Docker. You will be able to e-use its >>>>>> knowledge to package increasingly complex applications (that might >>>>>> have more numerous dependencies that you wouldn't have to manage on >>>>>> the host). >>>>>> >>>>>> HTH, >>>>>> Thu >>>>>> >>>>>> 2014-06-11 12:24 GMT+02:00 Corentin Dupont <corentin.dupont(a)gmail.com >>>>>> >: >>>>>> > Hi guys! >>>>>> > Is there a procedure to deploy a Haskell application? >>>>>> > I have an Amazon EC2 micro instance to run my application, but it's >>>>>> way too >>>>>> > small to compile it using cabal (compilation takes half a day >>>>>> rouhgly), so I >>>>>> > compile it on my computer. >>>>>> > Is there a convenient way to bundle the executable with the >>>>>> resources and >>>>>> > ship it to the server? >>>>>> > >>>>>> > Thanks! >>>>>> > Corentin >>>>>> > >>>>>> > _______________________________________________ >>>>>> > Haskell-Cafe mailing list >>>>>> > Haskell-Cafe(a)haskell.org >>>>>> > http://www.haskell.org/mailman/listinfo/haskell-cafe >>>>>> > >>>>>> _______________________________________________ >>>>>> Haskell-Cafe mailing list >>>>>> Haskell-Cafe(a)haskell.org >>>>>> http://www.haskell.org/mailman/listinfo/haskell-cafe >>>>>> >>>>> >>>>> >>>> >>> >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >> >

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Deploy Haskell application
by Corentin Dupont 11 Jun '14

11 Jun '14

Hi guys! Is there a procedure to deploy a Haskell application? I have an Amazon EC2 micro instance to run my application, but it's way too small to compile it using cabal (compilation takes half a day rouhgly), so I compile it on my computer. Is there a convenient way to bundle the executable with the resources and ship it to the server? Thanks! Corentin

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non-exhaustive pattern match(es)?
by Semen Trygubenko / Семен Тригубен ко 11 Jun '14

11 Jun '14

Dear Haskell Cafe, In the following program f :: Int -> [(Int,Int)] -> [(Int,Int)] -> [(Int,Int)] f _ cs [] = cs f _ [] _ = [] f i (c:cs) ((i',t):os) | i < i' = [] | i == i' = [] | i > i' = [] -- | otherwise = [] main :: IO () main = do print $ f 0 [] [] without the "otherwise" clause (commented) I get the warning example.hs:2:1: Warning: Pattern match(es) are non-exhaustive In an equation for `f': Patterns not matched: _ (_ : _) ((_, _) : _) Could someone help me uncover which cases that are not… erm… covered by the above patterns? Many thanks, Semen PS This definition, on the other hand, f _ cs [] = cs f _ [] _ = [] f i (c:cs) ((i',t):os) = [] is exhaustive… -- Семен Тригубенко http://trygub.com

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[Rejected Paper] Experience Report: Writing NetBSD Sound Drivers in Haskell
by Kiwamu Okabe 11 Jun '14

11 Jun '14

Hi jhc-hackers, I have written a paper "Experience Report: Writing NetBSD Sound Drivers in Haskell". http://metasepi.org/papers.html It explains Ajhc customized jhc GC, and sometime useful to develop jhc. Thank's, -- Kiwamu Okabe at METASEPI DESIGN

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JOB: AHRC Doctoral Studentship in Computational Musicology
by Richard Lewis 10 Jun '14

10 Jun '14

STUDENTSHIP ADVERTISEMENT With apologies for cross posting AHRC Doctoral Studentship in Computational Musicology http://www.transforming-musicology.org/news/2014-06-03_ahrc-doctoral-studen… London, UK (with UK residency requirement unfortunately) Although this is not an explicitly Haskell programming job, the student would be free to work in whatever language they wish. Furthermore, there would be encouragement to consider a functional and/or logic programming approach to research. Award: fees and tax-free stipend at £15,726 p.a. (inc. of London weighting) Application deadline: Tuesday 1 July 2014 Expected start date: October 2014 We invite applications for a Doctoral Studentship, funded by the Arts and Humanities Research Council, in Computational Musicology, located at Queen Mary University of London, under the supervision of Professor Geraint Wiggins. The studentship is part of the "Transforming Musicology" project, including Goldsmiths, University of London, Queen Mary University of London, the University of Oxford and Lancaster University. This project, led by Prof Tim Crawford in the Computing Department of Goldsmiths, University of London, brings together 15 researchers to effect a Digital Transformation of the discipline of musicology. The aim of the open studentship is to research and develop new methods for the representation of, and inference about, music-theoretic and perceptual aspects of music, based on, but not restricted to, past work by Prof. Wiggins and colleagues. This will be deployed using Semantic Web technology. The studentship will be located in a very rich research environment, first within the Transforming Musicology project, but also within the Computational Creativity Lab at QMUL, and the successful candidate will be encouraged to interact with other researchers in both of these contexts. This studentship, funded by an AHRC Doctoral Training Account, is for fees plus a tax-free stipend starting at £15,726 per annum. Further details of the AHRC scheme including terms and conditions can be found here: http://www.ahrc.ac.uk/Funding-Opportunities/Postgraduate-funding/Pages/Curr… Applicants must satisfy the AHRC's UK residence requirements: http://www.ahrc.ac.uk/Funding-Opportunities/Documents/Guide%20to%20Student%… Candidates must have a first class or 2.1 undergraduate degree or equivalent, either with a significant component of music theory, in which case evidence of exceptionally well-developed practical expertise in computing, including programming, will be required, or in computer science or equivalent, in which case evidence of formal training in music theory (e.g. to grade V or equivalent) will be required. Candidates with relevant postgraduate qualifications will be particularly welcome, especially if they are qualified in both music and computer science. Other relevant qualifications and/or areas of expertise include (but are not limited to): artificial intelligence, informatics, formal logic and automated reasoning, musicology, knowledge representation, deductive database theory. The successful applicant may be required to undertake relevant undergraduate and postgraduate interdisciplinary courses as part of the programme of study. Informal enquiries can be made by email to Prof. Geraint Wiggins (geraint.wiggins(a)qmul.ac.uk) Please note that Prof. Wiggins is unable to advise, prior to interview, whether an applicant is likely to be selected. To apply please follow the on-line process (see http://www.qmul.ac.uk/postgraduate/howtoapply/) by selecting "Electronic Engineering" in the "A-Z list of research opportunities" and following the instructions on the right hand side of the web page. Please note that instead of the 'Research Proposal' we request a 'Statement of Research Interests'. Your Statement of Research Interest should answer two questions: (i) Why are you interested in the proposed area? (ii) What is your experience in the proposed area? Your statement should be brief: no more than 500 words or one side of A4 paper. In addition we would also like you to send a sample of your written work, such as your final year dissertation. More details can be found at: http://www.eecs.qmul.ac.uk/phd/how-to-apply Applications must be received by Tuesday 1 July 2014. Interviews are expected to take place during July 2014. -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Richard Lewis Computing, Goldsmiths' College t: +44 (0)20 7078 5203 @: lewisrichard http://www.transforming-musicology.org/ 905C D796 12CD 4C6E CBFB 69DA EFCE DCDF 71D7 D455 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

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Problems using ghc 7.8.2 with options -staticlib and -threaded on osx
by Frode Nerbråten 10 Jun '14

10 Jun '14

Hi, I'm having trouble building my Haskell library with GHC 7.8.2 and Cabal 1.20.0.2 on OSX 10.9.3 with both -staticlib and -threaded enabled. The library I'm building exports several functions using FFI to be called from ObjectiveC in an Xcode project. This works fine with just -staticlib enabled, but now I realize I need to call into my Haskell library from multiple OS-threads simultaneously. But when I add -threaded to ghc-options I get an error when linking: error: libtool: can't locate file for: -lpthread error: libtool: file: -lpthread is not an object file (not allowed in a library) The linker command that fails looks like this (... replaces a bunch of -l and -L options): libtool -static -o liba.a dist/build/HsCocoa.o ... -lCffi -lpthread In /usr/lib I have a libpthread.dylib that links to libSystem.dylib, but no libpthread.a. I was under the impression that libpthread was included with the system install. Is this supposed to work or am I misunderstanding something basic? :) Any help would be greatly appreciated! The project source is available on github: https://github.com/froden/digipostarkiv (I asked the same question on stackoverflow: http://stackoverflow.com/q/24096257/777411) Best regards, Frode Nerbråten

2 4

XMonad and xinput.d.
by Magicloud Magiclouds 10 Jun '14

10 Jun '14

Hi, I am using Ubuntu, in which, X input method (ibus, for me) is started by xinput.d scripts. This works fine with KDE, Unity, etc. But when I switch to xmonad, there is no input method window, tray icon. And hotkeys not work, either. Ibus processes are there. Seems like I have to kill the ones started by xinput.d, and restart it myself in xmonad. What did I do wrong? -- 竹密岂妨流水过山高哪阻野云飞 And for G+, please use magiclouds#gmail.com.

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New Functional Programming Job Opportunities
by Functional Jobs 09 Jun '14

09 Jun '14

Here are some functional programming job opportunities that were posted recently: Sr. Software Engineer at Clutch Analytics http://functionaljobs.com/jobs/8720-sr-software-engineer-at-clutch-analytics Cheers, Sean Murphy FunctionalJobs.com

1 0

open-union
by Ben Foppa 09 Jun '14

09 Jun '14

Hi cafe. On a use case whim, I made the open-union package ( https://github.com/RobotGymnast/open-union) copying the basic idea from extensible-effects:Data.OpenUnion1. I haven't uploaded to hackage yet, on the chance that there's already something like this around. Here's the basic functionality: {-# LANGUAGE TypeOperators #-} {-# LANGUAGE ScopedTypeVariables #-} import Data.OpenUnion type MyUnion = Union (Char :| Int :| [()] :| Void) showMyUnion :: MyUnion -> String showMyUnion = (\(c :: Char) -> "char: " ++ show c) @> (\(i :: Int) -> "int: " ++ show i) @> (\(l :: [()]) -> "list length: " ++ show (length l)) @> typesExhausted main :: IO () main = do putStrLn $ showMyUnion $ liftUnion (4 :: Int) putStrLn $ showMyUnion $ liftUnion 'a' putStrLn $ showMyUnion $ liftUnion [(), ()] If any of the (@>) cases is omitted, a compile-time error occurs. If you try to lift a bad value to the union, a compile-time error occurs. Any thoughts? Is there already something like this around?

4 7

Using quickcheck with test-framework (collect doesn't work)
by Rafael Almeida 08 Jun '14

08 Jun '14

Hello, I'm trying to use quickcheck with test-framework. QuickCheck site says I can use a function called collect to see statistics of data generation. The function "collect" doesn't seem to print anything, though. This is the output I get after running cabal test: Running 1 test suites... Test suite reference: RUNNING... Test suite reference: PASS Test suite logged to: dist/test/100doors-0.1-reference.log 1 of 1 test suites (1 of 1 test cases) passed. This is what I see inside the log: Test suite reference: RUNNING... Main: flipped door is different state: [OK, passed 100 tests] flipDoors creates a different list of doors unless empty: [OK, passed 100 tests] Properties Total Passed 2 2 Failed 0 0 Total 2 2 Test suite reference: PASS Test suite logged to: dist/test/100doors-0.1-reference.log This is my test code (stripping out the boring parts): instance Arbitrary Door where arbitrary = elements [Opened, Closed] prop_flipped_door_is_different_state door = door /= flipDoor door prop_flipDoors_creates_a_different_list_of_doors_unless_empty n doors = collect n $ (not $ null doors) ==> doors /= (flipDoors n doors) []'s Rafael

2 1

Using quickcheck to check for errors
by Rafael Almeida 08 Jun '14

08 Jun '14

Hello, Let's say we want to quickcheck the function !!. Passing a negative index to it is an error. However, how can you make a check that it indeed errors in such situation? prop_negative_index_generates_error list = forAll negativeIndex \x -> ... What should I write in ...? []'s Rafael

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Postdoctoral Research Position: Type Inference in Functional Programming
by Ekaterina Komendantskaya 07 Jun '14

07 Jun '14

Hello, I am looking for a postdoctoral researcher to work on developing new algorithms for type inference in functional languages. Position is based at the School of Computing, University of Dundee, Scotland. Closing date for applications is 20 June 2014; starting date is flexible. Salary scale: £27,837 to £36,661 per annum. More details are available here: https://docs.google.com/document/d/1UUuf-BllmQ925vLV6jtzKreDcZYEOsF96dtj_IK… Please re-forward to potential applicants. Cheers, Katya Ekaterina Komendantskaya Senior Lecturer, Head of PhD Studies Room 1.04, Queen Mother Building School of Computing, University of Dundee Scotland, DD14HN Tel: (+44) 01382384820

1 0

ZuriHac 2014 - Updates
by Bas van Dijk 05 Jun '14

05 Jun '14

Dear (potential) ZuriHac 2014 attendees, I would like to make a few announcements regarding ZuriHac 2014, a Haskell hackathon taking place in Zurich from Friday 6 June 2014 to Sunday 8 June 2014. Besides hacking on Haskell projects with core members of the community you will hear talks by Simon Marlow and Edward Kmett. Note that this event is open to any experience level, from beginners to gurus. In fact, one of the goals is to bring beginners in contact with experts so that the former can get a quick start in the Haskell community and the latter more help with their projects. For more information see: http://www.haskell.org/haskellwiki/ZuriHac2014 Registration ------------ I'm happy and sad to inform you that we've almost reached capacity for ZuriHac 2014. Happy because it looks like this might be the biggest Haskell Hackathon ever. Sad because I soon have to start adding new registrations to a waiting list. So if you want to join us, and haven't registered already, then please do so soon at: http://bit.ly/ZuriHac2014. Also if you've already registered but know you won't be able to make it, please cancel by emailing me to make room for others. T-Shirt ------- Like last year, each attendee will get a free ZuriHac T-shirt. If you've already registered, please tell me which sizes and model you would like to have: Male: S, M, L, XL, XXL Female: S, M, L, XL, XXL Host ---- Erudify, the company which is hosting ZuriHac, recently changed its name to Better. Do note that we haven't changed location. See our new website on why we have rebranded: http://better.com/en/rebranding Regards, The ZuriHac 2014 organizers

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ANNOUNCE: music-suite 1.7
by Hans Höglund 05 Jun '14

05 Jun '14

I am pleased to announce the release of Music Suite v1.7. The Music Suite is a collection of Haskell libraries for composition, analysis and manipulation of music. It is generic enough to handle electronic music and non-Western music theory, as well as most aspects of common music notation. It can read and write many standard representations such as MIDI, MusicXML, Lilypond and ABC notation. Getting it Install the Suite from Hackage: cabal install music-suite Documentation and examples: http://music-suite.github.io The source code is available on Github: https://github.com/music-suite For bug reports, please use the relevant Github tracker: https://github.com/music-suite/music-score/issues For questions, feedback and general discussion, see music-suite-discuss(a)googlegroups.com http://groups.google.com/d/forum/music-suite-discuss Highlights Some highlights of this release include: Many new time containers, including more fine-grained versions of Score and Behavior Better interface for Score, Voice and Chord Better interface to musical aspects (i.e. parts, pitches, dynamics and articulations) using lenses and traversals Polymorphic update of musical aspects, so representation can change mid-traversal Now supports phrase-wise traversals of scores and voices New SuperCollider backend Restructuring of backend code in terms of a single class HasBackend Backend can now be parameterized on container type, rather than just note type Better notation of dynamics and articulation For the full notes, see: https://github.com/music-suite/music-docs/blob/master/releases/Notes.md Stability Please note that the Suite is quite usable, parts of it are still experimental, and we expect the API to change slightly with every release up to v2.0.0 (think of it as optimistic versioning). If you have any problems with upgrading from a previous version, please post to the group below. Contributing If you are interested in contributing to the Suite, please join the Github organization (see the link above). In addition to code, we appreciate contributions in the form of tutorials, examples or musical compositions. Hopefully we may soon have a showcase of works created with Music Suite, like Diagram's gallery. Sincerly, Hans - Hans Höglund Composer, conductor and developer hans [at] hanshoglund.se hanshoglund.com https://twitter.com/hanshogl https://soundcloud.com/hanshoglund http://github.com/hanshoglund

2 2

Getting list of constructors of a Type
by Alejandro Serrano Mena 04 Jun '14

04 Jun '14

Dear Haskell-Café, As part of my Google Summer of Code, I need to get the list of data constructors of a certain data type on a specific scenario. In my case, I'm getting a value of type Type (by calling exprType). I was expecting to be able to call getInfo directly on that value of type Type, but it doesn't have a name nor the constructors of Type are public. Thus, I'm not able to get that information :( Thanks in advance, Alejandro

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PROPOSAL: Record field type inference
by John Meacham 04 Jun '14

04 Jun '14

This is also available as html at http://repetae.net/computer/jhc/record_inference.html Record Type Inference ===================== An extension to the named field mechanism that will greatly enhance the utility of them when combined with the existing `DisambiguateRecordFields`, `RecordPuns`, and `RecordWildCards`. The proposal is to allow the types of record fields to be inferred by the normal type inference engine. It would look like ~~~~ {.haskell} data Rec = Rec {fieldA,fieldB,fieldC} f Rec { .. } = Rec { .. } where fieldA = True fieldB = 4 ~~~~ This would infer the types `Bool`, `Int`, and `forall a . a` for the fields of the record constructor and `f :: Rec -> Rec` for f. For the purposes of type checking the fields are treated as monomorphic and not generalized but defaulted like normal after typechecking the module. Other than infering the types of the record fields, the records have the normal syntax. The extensions `RecordPuns`, `RecordWildCards` and `DisambiguateRecordFields` will be enabled when record field inference is enabled. Selector functions will not be created for infered records, as in, the names are field labels and not functions. This means they do not share a namespace with functions and do not conflict with each other. Multiple records may have the same field names in the same module. This means the following is fine. ~~~~ {.haskell} data Rec1 = Rec1 {input, withFoo, withoutFoo } data Rec2 = Rec2 {input, withBar, withoutBar } f Rec1 { .. } = case input of [] -> Rec1 { .. } (x:xs) -> if hasFoo x then Rec1 { withFoo = x:withFoo, .. } else Rec1 { withoutFoo = x:withoutFoo, .. } ~~~~ Possible extensions ------------------- ### as-pattern disambiguation In order to make the disambiguation of record fields more useful without relying on the type checker for disambiguation, We can declare that variables explicitly bound to a constsructor in a pattern match use that constructor to disambiguate fields for operations on the variable. This is a purely syntactic transformation that can happen before typechecking. It can be used as follows. ~~~~ {.haskell} -- use the input bound by a Rec1 to update the input bound by a Rec2 f r1@Rec1 { input } r2@Rec2 {} = case input of xs | any hasBar xs = f r1 { input = [] } r2 { input } ~~~~ ### Field label inference It is concievable that we may want to infer the fields themselves of a record, as in: ~~~~ {.haskell} -- infer that R has the field labels bob and susan data R = R { ..} f x@R {bob} = R {susan = bob} ~~~~ In order to implement this, a pass through the file will collect every field label that is used with an explicit R constructor and treat the record as if it were declared with those names as infered fields.

2 2

Happstack: moving the uploaded file
by Nikita Karetnikov 03 Jun '14

03 Jun '14

I’m trying to create a trivial Happstack application based on the example from the “File Uploads” section of the Happstack book [1]. It should work as follows: 1. If there is no file called ‘foo’ on disk, show the upload form at any page. 2. If the file exists, show its contents at ‘localhost:8000/file’ and the upload form at any other page. The difficulty is that initially the uploaded file is placed to a temporary location, but since I want to read the file later, I have to move it somewhere. ‘UploadFile-working.hs’ uses two handlers for that, which doesn’t look right. I’d like the code to look like ‘UploadFile.hs’, but it doesn’t work properly. Could anyone explain why? [1] http://happstack.com/docs/crashcourse/index.html

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ANNOUNCE: jhc 0.8.2
by John Meacham 02 Jun '14

02 Jun '14

Lots of internal improvements in this one, so may be of more interest to developers http://repetae.net/computer/jhc/ - completely replaced the front end parser/lexer with a new more flexible one. My rewritten one is about 3,250 lines shorter. - The new one uses a general precedence parser for application as well as infix operators, allowing consistent handling of bang, irrefutable, and @ patterns and allows prefix and infix operators with a higher precedence than application to be defined. Incidentally, this allows for ~ and @ in expressions. (~) = negate (prefixr 11) gives us a nice strongly binding negative and @ (infixr 12) is perfect for type directed name resolution without further overloading the humble dot. they parse exactly the same as they do in patterns so no new magic is being added to the symbols other than allowing them in expressions. - Layout algorithm is fully in the lexer now, no lexer/parser interaction needed and useful transformations happen between the two simplifying the parser. - updated a lot of the external libraries to new versions - improvements to the build based on feedback, now gives much better error messages about what went wrong. - include an experimental utility to automatically download 3rd party packages from hackage and install them, it has some kinks, but even if it can't do it automatically, it provides a template for easily modifying the package to work. - removed the last of the cabal-cruft from the library build system. - fixed a lot of bugs relating to errors not being caught early by jhc so they produce a cryptic message from the compiler later, attach source location to more errors for better reporting. - ghc 7.8 compatibilty contributed by others. (thanks!) - infix type constructor extension supported - field punning extension now supported - new option -fno-sugar to turn off all desugaring that would introduce any hidden dependencies, all literals are unboxed under it. WYSIWYG. - unboxed kinds now more general, work in more places - record field names may overlap - more efficient binary representation using LEB128 - Data.String added with mild magic. -- John Meacham - http://notanumber.net/

1 0

Haskell jobs in the Silicon Valley?
by David Banas 02 Jun '14

02 Jun '14

Hi all, Just pinging to see if anyone knows of a Haskell job opening in the Silicon Valley. Thanks, -db

1 0

MacOS testing?
by Ian Ross 01 Jun '14

01 Jun '14

Hi all, Does anyone know of a good solution for MacOS testing that doesn't cost much? (Ideally, that costs nothing...) I've been getting a lot of MacOS-specific issues on the C2HS that I maintain and, since I don't have a Mac myself, testing and fixing these things is a bit of a problem. There is no equivalent of Amazon's EC2 for MacOS. There are some hosting services out there, but they're not all that practical, since they cost, they're set up for continuous hosting rather than intermittent use for bug-fixing, and you can't save a machine image snapshot once you've installed all the software you need (as you can on AWS) so you either need to keep your instance running or reinstall everything every time you want to test something. Any ideas? The only thought I've had so far was to try to do something horrible using Travis (Kiwamu Okabe has some slides about building and testing Haskell code on Travis: http://www.slideshare.net/master_q/20131109-kof2013-travisciosx) That's not a good solution for debugging though. Thanks for any thoughts you might have, Ian. -- Ian Ross Tel: +43(0)6804451378 ian(a)skybluetrades.net www.skybluetrades.net

3 2

MonadRandom and traversing infinite streams
by Petr Pudlák 31 May '14

31 May '14

Hi Brent and Wouter, looking at SO questions http://stackoverflow.com/q/14494648/1333025 http://codereview.stackexchange.com/q/52149/15600 threre are monads and applicative functors that support ``` sequenceInf :: S.Stream (f a) -> f (S.Stream a) ``` that is, allow lazy traversals of streams (infinite lists). Namely those that don't produce any additional output. And instances of MonadRandom seem to have valid implementations of `sequenceInf`, which would allow to produce lazy infinite randomized lists (basically a generalization of `getRandoms`). My proposal is to add ``` class Applicative f => LazyApplicative f where sequenceInf :: S.Stream (f a) -> f (S.Stream a) sequenceInf = traverseInf id traverseInf :: (a -> f b) -> S.Stream a -> f (S.Stream b) traverseInf f = sequenceInf . S.map f ``` to a module in Stream package (for example `Control.Applicative.Lazy`), and add its instances into `MonadRandom`. What do you think? I'd be willing to send patches. Best regards, Petr

2 2

Self-contained GHC for Mac
by Bob Ippolito 30 May '14

30 May '14

After seeing some demand for packaged Haskell for Mac for the IHaskell project and by word of mouth at BayHac I decided to take a stab at it. Here you go: http://ghcformacosx.github.io/ (currently GHC 7.8.2 and cabal-install 1.20.0.1) Why? It can be a bit cumbersome to use the GHC builds from haskell.org on Mac, because they don't come "fully baked", you have to ./configure --prefix=/some/path to get them installed and the installation is not relocatable, if you move it the scripts will break and the package.conf.d files will go stale. It also doesn't ship with cabal-install, which is cumbersome as well, especially for new users. How does it work? In https://github.com/ghcformacosx/ghc-dot-app I have a Main.hs script which downloads/builds/etc. all of the prerequisites. Then it patches the shell scripts to use a path relative to themselves (after following symlinks) rather than hard-coding an installation location. It also patches the package.conf.d files to use ${pkgroot} relative paths. Separately, there's an Xcode project that includes all of the metadata to make it look like a real Mac app bundle (icons, Info.plist) and a small Cocoa application that has a button to open the docs and provides instructions for adding it to the PATH in .bashrc. Due to the heuristics in Mac OS X's man, this will automatically make man pages work as well. Using Xcode here also makes it produce a signed build (which I do, since I am already paying for the $99/year license). -bob

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Local .ghci_history
by João Cristóvão 29 May '14

29 May '14

Hello, I raised this on trac ( https://ghc.haskell.org/trac/ghc/ticket/9089 ), but it seems it did not get much attention, but surelly I'm not the only one who finds this useful. With this little change, if there is a .ghci_history in the folder where you launch ghci it will use it instead of the global ~/.ghc/ghci_history. So, if you keep jumping from one project folder to the other, you can have a project specific history on each one (if you want). If you do not create a local .ghci_history file on that folder, the behaviour is exactly the same as it was before. Thus, this is somewhat identical to the local .ghci file. This, coupled with finally discovering the well hidden possibility of increasing the history size: http://trac.haskell.org/haskeline/wiki/UserPrefs Has vastly improved my ghci workflow. What do you think? João

2 2

Haskell in Org Mode Babel
by Chris Warburton 29 May '14

29 May '14

Hello, I'm wondering if anyone's had success using Haskell in "Babel", the literate programming system in Emacs's Org Mode? I'm trying it with a blog post, but am getting mixed results. For those who don't know, Org Mode is an Emacs mode for editing text files, which has a bunch of features controlled by markup in the file. Babel is a feature which allows source code in various languages to be included in-line and executed. For example, I can write some Haskell like this: #+begin_src haskell [1..10] #+end_src Cheers, Chris

1 1

Haskell Weekly News: Issue 295
by Daniel Santa Cruz 29 May '14

29 May '14

Welcome to issue 294 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers from May 4 to 24, 2014 Quotes of the Week * dalaing: going from doing a fair bit of haskell recently to doing javascript today... sigh... it feels like the difference between typing at a keyboard and typing with a pair of those sporting-event-foam-hands-with-a-pointing-finger on * monochrom: to be blunt, I believe that "I do X for a living" means nothing. politicians do politics for a living too, what is the result? * Cale: Java seems like it was designed especially to be a strawman for people who hate static type systems * ReinH: Every so often edwardk goes up to the mountain of CT and brings us some new tablets edwardk: hear that dolio? we're going to start calling you the mountain. Top Reddit Stories * #haskell is welcoming and troll resistent (just found this by accident) Domain: gist.github.com, Score: 172, Comments: 19 Original: [1] http://goo.gl/TCiMW On Reddit: [2] http://goo.gl/JZNY3M * $7.5m DoD grant to develop Homotopy Type Theory Domain: cmu.edu, Score: 117, Comments: 70 Original: [3] http://goo.gl/EmSlbE On Reddit: [4] http://goo.gl/sKjGIl * Understanding the Stack Domain: well-typed.com, Score: 102, Comments: 13 Original: [5] http://goo.gl/qo9m5O On Reddit: [6] http://goo.gl/MVvaQn * Elm 0.12.3 - efficient 3D rendering with WebGL Domain: elm-lang.org, Score: 82, Comments: 19 Original: [7] http://goo.gl/iATfSi On Reddit: [8] http://goo.gl/QJ5ttp * An example of a Real World Haskell Application Architecture Domain: self.haskell, Score: 68, Comments: 36 Original: [9] http://goo.gl/ZTcr1x On Reddit: [10] http://goo.gl/ZTcr1x * ezyang: “try a <|> b” considered harmful Domain: blog.ezyang.com, Score: 67, Comments: 29 Original: [11] http://goo.gl/BEkC6W On Reddit: [12] http://goo.gl/3oql5l * 9m URL Shortener (Written in Haskell) Domain: 9m.no, Score: 67, Comments: 27 Original: [13] http://goo.gl/E0NoYv On Reddit: [14] http://goo.gl/n4cyN5 * Announce: JHC 0.8.1 IS OUT Domain: notanumber.net, Score: 66, Comments: 14 Original: [15] http://goo.gl/n6qAcf On Reddit: [16] http://goo.gl/wSMrva * Haskell for Mac OS X, self-contained relocatable GHC builds Domain: ghcformacosx.github.io, Score: 64, Comments: 35 Original: [17] http://goo.gl/CvsYC7 On Reddit: [18] http://goo.gl/WcIBw5 * Binary serialisation: better, stronger, faster (PDF, Duncan Coutts, March 2014) Domain: code.haskell.org, Score: 63, Comments: 39 Original: [19] http://goo.gl/r4xShZ On Reddit: [20] http://goo.gl/xhJRbg * CS240h lecture notes Domain: scs.stanford.edu, Score: 61, Comments: 8 Original: [21] http://goo.gl/F39zHe On Reddit: [22] http://goo.gl/AQqrUj * Haskell-mode documentation Domain: chrisdone.com, Score: 58, Comments: 28 Original: [23] http://goo.gl/XzKMCk On Reddit: [24] http://goo.gl/DZBQtO * PSA: you can now visit status.haskell.org Domain: status.haskell.org, Score: 58, Comments: 19 Original: [25] http://goo.gl/oRHfsn On Reddit: [26] http://goo.gl/Ye9YU2 * Once more into the teach, dear friends Domain: serpentine.com, Score: 57, Comments: 11 Original: [27] http://goo.gl/L8Csnm On Reddit: [28] http://goo.gl/AyF2Fs * What Features Would You Like to Find in a Haskell IDE? Domain: self.haskell, Score: 57, Comments: 90 Original: [29] http://goo.gl/Pvo32I On Reddit: [30] http://goo.gl/Pvo32I * Adventure with Types in Haskell - Simon Peyton Jones [1:33:36] Domain: youtu.be, Score: 57, Comments: 10 Original: [31] http://goo.gl/L9wGWe On Reddit: [32] http://goo.gl/sL3u8i * Ars Technica has Haskell as one of three potential heirs to Fortran's scientific computing throne Domain: arstechnica.com, Score: 56, Comments: 78 Original: [33] http://goo.gl/lxWcdK On Reddit: [34] http://goo.gl/kCxUS9 Top StackOverflow Questions * Why does Haskell's “do nothing” function, id, consume tons of memory? votes: 72, answers: 1 Read on SO: [35] http://goo.gl/8awkSk * Are Ana-/Catamorphisms just slower? votes: 29, answers: 2 Read on SO: [36] http://goo.gl/wcmkQw * Code becomes slower as more boxed arrays are allocated votes: 22, answers: 2 Read on SO: [37] http://goo.gl/qfKo2a * Which part of Real World Haskell is now obsolete or considered bad practise? votes: 22, answers: 1 Read on SO: [38] http://goo.gl/EtT51x Until next time, [39]+Daniel Santa Cruz References 1. https://gist.github.com/quchen/5280339 2. http://www.reddit.com/r/haskell/comments/2516e4/haskell_is_welcoming_and_tr… 3. http://www.cmu.edu/news/stories/archives/2014/april/april28_awodeygrant.html 4. http://www.reddit.com/r/haskell/comments/24rs73/75m_dod_grant_to_develop_ho… 5. http://www.well-typed.com/blog/94/ 6. http://www.reddit.com/r/haskell/comments/2641x0/understanding_the_stack/ 7. http://elm-lang.org/blog/announce/0.12.3.elm 8. http://www.reddit.com/r/haskell/comments/261abs/elm_0123_efficient_3d_rende… 9. http://www.reddit.com/r/haskell/comments/24y6ls/an_example_of_a_real_world_… 10. http://www.reddit.com/r/haskell/comments/24y6ls/an_example_of_a_real_world_… 11. http://blog.ezyang.com/2014/05/parsec-try-a-or-b-considered-harmful/ 12. http://www.reddit.com/r/haskell/comments/25ulsv/ezyang_try_a_b_considered_h… 13. http://9m.no/ 14. http://www.reddit.com/r/haskell/comments/267evu/9m_url_shortener_written_in… 15. http://notanumber.net/archives/178/jhc-haskell-0-8-1-released 16. http://www.reddit.com/r/haskell/comments/25o33n/announce_jhc_081_is_out/ 17. http://ghcformacosx.github.io/ 18. http://www.reddit.com/r/haskell/comments/26bx5n/haskell_for_mac_os_x_selfco… 19. http://code.haskell.org/~duncan/binary-experiment/binary.pdf 20. http://www.reddit.com/r/haskell/comments/25ch8v/binary_serialisation_better… 21. http://www.scs.stanford.edu/14sp-cs240h/slides/ 22. http://www.reddit.com/r/haskell/comments/25i99i/cs240h_lecture_notes/ 23. http://chrisdone.com/posts/haskell-mode-docs 24. http://www.reddit.com/r/haskell/comments/2583sm/haskellmode_documentation/ 25. http://status.haskell.org/ 26. http://www.reddit.com/r/haskell/comments/2653kp/psa_you_can_now_visit_statu… 27. http://www.serpentine.com/blog/2014/05/13/once-more-into-the-teach-dear-fri… 28. http://www.reddit.com/r/haskell/comments/25iqk7/once_more_into_the_teach_de… 29. http://www.reddit.com/r/haskell/comments/25sqvk/what_features_would_you_lik… 30. http://www.reddit.com/r/haskell/comments/25sqvk/what_features_would_you_lik… 31. http://youtu.be/6COvD8oynmI 32. http://www.reddit.com/r/haskell/comments/25vj62/adventure_with_types_in_has… 33. http://arstechnica.com/science/2014/05/scientific-computings-future-can-any… 34. http://www.reddit.com/r/haskell/comments/250558/ars_technica_has_haskell_as… 35. http://stackoverflow.com/questions/23746852/why-does-haskells-do-nothing-fu… 36. http://stackoverflow.com/questions/23664197/are-ana-catamorphisms-just-slow… 37. http://stackoverflow.com/questions/23462004/code-becomes-slower-as-more-box… 38. http://stackoverflow.com/questions/23727768/which-part-of-real-world-haskel… 39. https://plus.google.com/105107667630152149014/about

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[ANN] cartel - specify Cabal files using Haskell
by Omari Norman 29 May '14

29 May '14

The Cabal file format works very well for small projects. However, in big projects with a library, many executables, and test suites, some irritations emerge. You need to specify dependencies in multiple places, leading to redundancy. You also have to manually add in new modules, make sure you list all modules (a real pain with executables, as problems may arise only after you build a distribution tarball), and update your module lists when you refactor. Specifying your Cabal files in Haskell rather than in a plain-text file format helps deal with a lot of these problems. You have the full power of Haskell to make definitions in one place and then reuse them. You can also dynamically read a tree of modules and use the result, thus avoiding the need to manually update your module lists. A disadvantage to Cartel is that it can be a bit more verbose than a vanilla Cabal file. In addition, you also have to remember to generate the new Cabal file whenever you change the script that generates your Cabal file. Cabal already has an AST that it uses. Cartel could, perhaps, have re-used these structures. Cartel does not do this for three reasons. First, the Cabal API is a bit untidy, partially because it has to do things that Cartel doesn't have to worry about, but also because the comments in the Cabal modules themselves indicate that the whole thing could use a refactoring. Second, the Cabal developers make no commitment to keep that API stable. Third, the Cartel API tries only to replicate format of the plain-text Cabal file, which will be much more stable than the Cabal API. Hackage: http://hackage.haskell.org/package/cartel Github: https://github.com/massysett/cartel

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ANN: hcwiid-0.0.5 (wiimote, gaming)
by Ivan Perez 28 May '14

28 May '14

Hi cafe! We are happy to announce the release of Hcwiid 0.0.5, the Haskell bindings for cwiid, which provide a user-space driver for Nintendo's Wiimotes. The following new features have been made available recently: *- Infrared support*. This is essential if you want to use the sensor bar to detect what the wiimote is pointing at. *- Accelerometer support*. * - Improved API*. Access to all the key features, new auxiliary functions not present in cwiid, and a higher-level interface via the type system. *- Documentation*. An effort is being made to provide not only haddock documentation, but also several tests that demonstrate the features of this library. More information (including "What is a wiimote and how can I use it?" and "what can we expect next") can be found here: http://keera.co.uk/blog/2014/05/27/interacting-haskell-games-using-wiimote/ Hackage: https://hackage.haskell.org/package/hcwiid Github: https://github.com/ivanperez-keera/hcwiid I hope you all enjoy spicing up your applications a little bit with this library. All the best Ivan facebook: https://www.facebook.com/keerastudios twitter: @KeeraStudios

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Interfacing BTCe
by Miro Karpis 28 May '14

28 May '14

Hi cafe, I'm trying to interface BTCe and get my account info. I have found following peace of code, which I would like to build on top: http://pastebin.com/AfDt8jcs I have added to the request a POST method, but I'm still getting error from BTCe: "{\"success\":0,\"error\":\"*invalid nonce parameter; on key:0*, you sent:\"}" The API is documented here: https://btc-e.com/api/documentation In short: Authorization is performed by sending the following HTTP Headers: *Key* — API key *Sign* — POST data (?param=val&param1=val1) signed by a secret key according to HMAC-SHA512 method; Sent on *https://btc-e.com/tapi <https://btc-e.com/tapi>* . All requests must also include a special *nonce* POST parameter with increment integer. (>0) The method name is sent via POST parameter method. All the method parameters are sent via POST. {-# LANGUAGE OverloadedStrings #-} import Network.HTTP.Conduit import Network.HTTP.Types.Header import Data.Word import Data.ByteString.Lazy(pack) import qualified Data.ByteString.Char8 as B import Data.Digest.Pure.SHA import Data.Time.Clock.POSIX ------------------------------------------------------------------------------- toWord8 :: String -> [Word8] toWord8 = Prelude.map (fromIntegral . fromEnum) ------------------------------------------------------------------------------- key :: B.ByteString key = "key" secret :: String secret = "secret" url :: String url = "https://btc-e.com/tapi" ------------------------------------------------------------------------------- querystring :: Int -> String querystring nonce = "?method=getInfo&nonce=" ++ show nonce sign :: Int -> B.ByteString sign nonce = B.pack $ show $ hmacSha512 (pack $ toWord8 secret) (pack $ toWord8 $ querystring nonce) main :: IO () main = do nonce <- fmap floor getPOSIXTime putStrLn $ url ++ (querystring nonce) ticker <- parseUrl $ url ++ (querystring nonce) let request = ticker { secure = True , method = "POST" , requestHeaders = (requestHeaders ticker) ++ [ ("Content-Type", "application/x-www-form-urlencoded") , ("Host", "btc-e.com") , ("User-Agent", "Haskell Trading Robot") , ("Key", key) , ("Sign", sign nonce)]} putStrLn $ show request response <- withManager $ httpLbs request print $ responseBody response any ideas more than welcome cheers, miro

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Munich Haskell Meeting
by Heinrich Hördegen 27 May '14

27 May '14

Dear all, our next Haskell meeting in Munich is scheduled for the 29th of May, 19h30 at Cafe Puck. If you plan to join, please go to http://www.haskell-munich.de/dates and klick the button. With hope to see many of you, Heinrich

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Second Workshop on Haskell And Rewriting Techniques (HART 2014, co-located with ICFP 2014)
by Janis Voigtlaender 27 May '14

27 May '14

CALL FOR PAPERS Second Workshop on Haskell And Rewriting Techniques (HART 2014) http://www.program-transformation.org/HART14/ To be held on September 5, co-located with ICFP, the Haskell Symposium, etc., in Gothenburg. Haskell is an advanced purely-functional programming language. Pure functional programming is programming with equations, often defined by pattern-matching. Rewriting is the science of replacing equals by equals and thus a very powerful method for dealing with equations, often constructor-based. There are strong connections between Haskell (or generally, pure functional) programming and rewriting. The purpose of the HART workshop is to foster those connections. In addition to an invited talk by Oleg Kiselyov, we plan a half day of discussions, in an informal setting, on how Haskell (and related languages) and rewriting techniques and theories can cross-fertilize each other. Topics of interest are, for example: ==================================== - equational reasoning and other rewriting techniques for program verification and analysis; - lambda calculi and type systems for functional programs and higher-order rewrite systems; - rewriting of type expressions in the type checker; - rewriting of programs by refactoring tools, optimizers, code generators; - execution of programs as a form of graph rewriting (terms with sharing); - Template Haskell, generally introducing a rewriting-like macro language into the compilation process. This list of topics is non-exclusive. If you have a contribution that connects Haskell and rewriting, then submit. Also, the workshop is deliberately open for discussion of rewriting-related aspects of languages like Agda, Clean, ... When in doubt, please contact a member of the PC (see below). Dates: ====== July 2: deadline for submissions July 21: notification of acceptance September 5: workshop Submission and proceedings: =========================== We solicit two types of submissions: - Extended abstracts. Presenting original research, and also preliminary reports of work in progress. Will be included in the proceedings. - Presentation-only papers. Describing work recently published or submitted. Only abstract will be included in the proceedings. Papers should be at most 5 pages in length, and should use the easychair.cls style. Submission is electronically at https://www.easychair.org/conferences/?conf=hart2014 In line with the informal style of the workshop, the reviewing of submissions will be light. Proceedings will be made available electronically. Program committee: ================== Bertram Felgenhauer Carsten Fuhs Andy Gill Makoto Hamana Bastiaan Heeren Femke van Raamsdonk Tiark Rompf Kristoffer Rose (co-chair) Christian Sternagel Janis Voigtländer (co-chair) Johannes Waldmann

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Cabal, tar and uploading to Hackage
by Magnus Therning 26 May '14

26 May '14

Lately my attempts at creating tar-balls for uploading to Hackage have been failing. I use the standard `./Setup.hs sdist` method to generate tar-balls, but apparently that uses `/usr/bin/tar` (GNU tar), which defaults to the 'gnu' format, while Hackage requires the 'ustar' format. Is there some way to pass arguments to `tar` when using `./Setup.hs sdist`? /M -- Magnus Therning OpenPGP: 0xAB4DFBA4 email: magnus(a)therning.org jabber: magnus(a)therning.org twitter: magthe http://therning.org/magnus Heuristic is an algorithm in a clown suit. It’s less predictable, it’s more fun, and it comes without a 30-day, money-back guarantee. -- Steve McConnell, Code Complete

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How to write fast for loops
by Niklas Hambüchen 26 May '14

26 May '14

As you probably now, `forM_ [1..n]` is incredibly slow in Haskell due to lack of list fusion [1]; a manually written loop is 10x faster. How do you people work around this? I keep defining myself something like loop :: (Monad m) => Int -> (Int -> m ()) -> m () loop bex f = go 0 where go !n | n == bex = return () | otherwise = f n >> go (n+1) Is there a function for this somewhere already? Or do you have another way to deal with this problem? Thanks! [1]: https://ghc.haskell.org/trac/ghc/ticket/8763

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New Functional Programming Job Opportunities
by Functional Jobs 26 May '14

26 May '14

Here are some functional programming job opportunities that were posted recently: Haskell Developer at skedge.me http://functionaljobs.com/jobs/8712-haskell-developer-at-skedgeme Cheers, Sean Murphy FunctionalJobs.com

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Chan with priorities
by Bulat Ziganshin 26 May '14

26 May '14

Hello Haskell-cafe, can you please point me to any OSS implementation of IO Channels with priorities - i.e. data pushed to the Chan using high priority should be read prior to the data pushed with lower priority: pushChan ch 1 'x' pushChan ch 2 'y' readChan ch >>= print -- prints 'y' i've found only STM implementations - i don't know STM enough, may be i just need to convert STM to IO operations? i don't expect strong guarantees, my algorithm will remain correct anyway. and i don't have lot of objects, it's just a few dozens -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com

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Job opening: Anchor Hosting, Sydney - Linux Haskell Developers
by Christian Marie 26 May '14

26 May '14

Anchor hosting is hiring Haskell developers! ============================================ Anchor hosting has job opportunities for two entry-to mid-level developers. We will be building an open source cloud hosting platform built upon Ceph and OpenStack in Haskell. This will involve experience across diverse fields, such as: Linux systems development, distributed systems, metric storage, data analysis, monitoring, tool development, REST API design and development, to name a few. We have two positions available; if you can't make your mind up, feel free to ask about them. Linux Systems Developer / Wizard ================================ You will work alongside sysadmins and developers on the Systems Team. This developer will be cutting a lot of Linux systems automation code, and will probably build a distributed system by the time you're done. A proven track record with Haskell and Linux is a must. Knowledge of type theory and language design would be a bonus. A working knowledge of C and basic algorithms is expected. You'll get to work on a Cloud hosting framework with interesting technologies, doing some cool things that nobody has done before. Data engineer ============= Part of our Analytics team, this role is fundamentally about helping our engineers make evidence-based decisions. You would be writing code to take numbers (such as the CPU usage of a set of machines) and convert them into more useful numbers (such as the probability of those servers catching fire in the next week, or the usage we should be billing the customer for). In addition to a working knowledge of Haskell and UNIX programming, experience working with large datasets, computational stats or machine learning would be a big plus. Applicants ========== Please send a resume along with a link to your Github account to pingu(a)anchor.com.au. Perks ===== Why Anchor should be your home away from home: * Our kick-ass office is on Hyde park, with Town Hall station just minutes away. * Well-stocked drinks fridge. * Catered lunch every Friday. * Pizza and board games every Tuesday night. * Transparent, no-nonsense and trusting environment – if we hire you we know you’ll do the right thing. * Company account with a great coffee shop across the road means your daily caffeination is free of charge! -- Christian Marie - Sparkly Code Princess

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wanted: Function to break circular data dependencies
by Job Vranish 25 May '14

25 May '14

Is a function like the following possible?: avoidCircularDataDependency :: a -> a -> a avoidCircularDataDependency a b = ? I want avoidCircularDataDependency to evaluate 'a', but if in the process of evaluating 'a' its own result is demanded (which normally would result in an infinite loop) it returns 'b' otherwise it returns 'a' . I've often found myself wanting a function like this. It would make certain kinds of knot-tying/cycle detection _much_ easier. Is there any reason why this function can't/shouldn't exist? - Job

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Typeclasses -- if does not satisfy
by Dmitry Bogatov 24 May '14

24 May '14

Hello! I am working on package to generalize common `runSomeThing` and `runSomethingT` functions. It is very easy to generalize runStateT and runReaderT like class Runnable a where type RunResult a run :: a -> RunResult a instance Runnable (StateT s m a) where --- Why ScopedTypeVariables do not work here? type RunResult (StateT s m a) = s -> m (a, s) run = runStateT --- ReaderT absolutely the same But problem is that `State s a` is in fact `StateT s Identity a` and I get type family conflicts. In fact, it boils down to following: type family TestIdentity (m :: * -> *) type instance TestIdentity Identity = Int type instance TestIdentity m = () -- Anything but Identity. In general, with all this TypeClass magic, I have a lot of ways that something belong to some class, and no (aside OverlappingInstances) to tell that it does NOT belong. I belive, there is reason to, but I do not see it. Also, seems even TH does not helps here. PS. Please, keep me in To: -- Best regards, Dmitry Bogatov <KAction(a)gnu.org>, Free Software supporter, esperantisto and netiquette guardian. git://kaction.name/rc-files.git GPG: 54B7F00D

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haskell on OpenBSD 5.5
by Michael S 24 May '14

24 May '14

Good day all, I installed OpenBSD 5.5 in order to learn haskell. There are a few glitches however. I installed the haskell-platform meta-package and the issues I noticed are: - hs-vector wouldn't install - ghci wouldn't start, the message: unable to load package `integer-gmp' Has anyone experienced the same issue? Is this happening on OpenBSD 5.4? Is this OpenBSD specific? Thanks in advance.

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