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Error in installing dph-examples on Mac OS X 10.7.3
by mukesh tiwari 10 Feb '12

10 Feb '12

Hello all I am trying to install dph-examples on Mac OS X version 10.7.3 but getting this error <http://hpaste.org/57699>. I am using ghc-7.4.1. Error running clang! you need clang installed to use the LLVM backend cabal: Error: some packages failed to install: dph-examples-0.6.1.3 failed during the building phase. The exception was: ExitFailure 1 I have already installed Xcode 4.2 and it shows Macintosh-0026bb610428:tmp mukesh$ clang clang clang++ Macintosh-0026bb610428:tmp mukesh$ clang -v Apple clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM 3.0svn) Target: x86_64-apple-darwin11.3.0 Thread model: posix Macintosh-0026bb610428:tmp mukesh$ clang++ -v Apple clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM 3.0svn) Target: x86_64-apple-darwin11.3.0 Thread model: posix Macintosh-0026bb610428:tmp mukesh$ l Display all 113 possibilities? (y or n) Macintosh-0026bb610428:tmp mukesh$ llvm- llvm-ar llvm-config llvm-diff llvm-extract llvm-gcc llvm-link llvm-objdump llvm-rtdyld llvm-tblgen llvm-as llvm-cov llvm-dis llvm-g++ llvm-gcc-4.2 llvm-mc llvm-prof llvm-size llvm-bcanalyzer llvm-cpp-4.2 llvm-dwarfdump llvm-g++-4.2 llvm-ld llvm-nm llvm-ranlib llvm-stub Macintosh-0026bb610428:tmp mukesh$ llvm-g++ -v Using built-in specs. Target: i686-apple-darwin11 Configured with: /private/var/tmp/llvmgcc42/llvmgcc42-2336.1~1/src/configure --disable-checking --enable-werror --prefix=/Developer/usr/llvm-gcc-4.2 --mandir=/share/man --enable-languages=c,objc,c++,obj-c++ --program-prefix=llvm- --program-transform-name=/^[cg][^.-]*$/s/$/-4.2/ --with-slibdir=/usr/lib --build=i686-apple-darwin11 --enable-llvm=/private/var/tmp/llvmgcc42/llvmgcc42-2336.1~1/dst-llvmCore/Developer/usr/local --program-prefix=i686-apple-darwin11- --host=x86_64-apple-darwin11 --target=i686-apple-darwin11 --with-gxx-include-dir=/usr/include/c++/4.2.1 Thread model: posix gcc version 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00) Regards Mukesh Tiwari

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Mersenne-random and standard random API
by Yves Parès 10 Feb '12

10 Feb '12

Hi, I've been in the past told that mersenne-random was much better than the standard random package. However, System.Random.Mersenne doesn't follow the general API described in System.Random, MTGen is not an instance of RandomGen. But a sample on System.Random.Mersenne.getStdRandom documentation ( http://hackage.haskell.org/packages/archive/mersenne-random/1.0.0.1/doc/htm…) indicates this: rollDice :: IO Int rollDice = getMTRandom (randomR (1,6)) It looks like wrong documentation (checking of older versions show that getMTRandom have never lived or been exposed by this module), but suggests MTRandom should be an instance of RandomGen (if I assume well that randomR is that of System.Random). So is it possible to use the fast and efficient mersenne generator with the convenient and general random API?

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Re: [Haskell-cafe] [Haskell] Support tools for development with Cabal and Darcs
by Duncan Coutts 10 Feb '12

10 Feb '12

On 10 February 2012 12:06, Henning Thielemann <lemming(a)henning-thielemann.de> wrote: > > I have uploaded three packages to Hackage that shall simplify maintaining > cabal packages under darcs revision control. They simplify tasks like > uploading packages after some tests, cabal version handling, compiling > multiple local packages in the right order, replacing identifiers in > multiple files, renaming modules. > > * http://hackage.haskell.org/package/darcs-scripts > * http://hackage.haskell.org/package/cabal-scripts > * http://hackage.haskell.org/package/cabal-sort Hi Henning, Would you mind giving me a breif explanation of the "compiling multiple local packages in the right order" feature? I'd like to understand what is missing in cabal-install in this respect. Currently with cabal-install you can say: cabal install ./a ./b ./c and it will install the packages in those directories in the right order. (It is also possible to list other install targets including local and remote tarballs, and of course packages from hackage). Duncan

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Fancy REPL
by Heinrich Apfelmus 10 Feb '12

10 Feb '12

Dear list, the Show class is extremely useful for exploring Haskell in a terminal, but sometimes, I just want something fancier. For instance, I'm currently dabbling with sound generation and it is only natural that I want to hear the sound instead of seeing a textual representation. Another example would be graphics, that are simply drawn on screen whenever you evaluate their value. Of course, this is simple to implement with a class class Demonstrable a where demo :: a -> IO () instance Demonstrable Sound where demo = play instance Demonstrable Sound where demo = draw instance Demonstrable GUI where demo = run etc. However, I don't want to reinvent the wheel, small as it may be, hence my question: is there a package on hackage that already defines a class similar to Demonstrable ? Or any other projects in this direction, like, say, a fancy REPL built on wxHaskell? Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com

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The State of Testing?
by Michael Craig 10 Feb '12

10 Feb '12

I've been picking up Haskell as a side project for the last few months, and I'm now considering publishing some useful code I've written and reused in several small projects. So far I've done relatively little with testing (these have been non-mission-critical applications) but I feel I should get my act together before pushing my work into the common ecosystem. I'm comfortable writing tests in QuickCheck and HUnit and bundling them as optional executables with cabal, but I understand there's a better way. Specifically, I'm looking at the test-framework package and cabal's (newish) test-suite sections. Are these two used together or each to the exclusion of the other? Is there something else I should be using? Cheers, Mike Craig

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: hs-json-rpc 0.0.0.1
by Felipe Almeida Lessa 09 Feb '12

09 Feb '12

[Redirecting to haskell-cafe] Congrats on your first release! While I haven't looked into your package in more depth, I'd suggest taking a look at http-conduit [1]. While I don't know of any benchmarks, it should be faster or at least as fast the HTTP package. It's also used by many people everyday (myself included), which means that it has no major bugs and that bugs are promptly solved. It also has some features that HTTP doesn't. Cheers! [1] http://hackage.haskell.org/package/http-conduit -- Felipe.

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Yesod and dependencies hell
by Никита Тимофеев 09 Feb '12

09 Feb '12

For three days I can't compile dependencies for my project using yesod, yesod-auth, yesod-persistent, persistent-template, persistent-sqlite, persistent. When I varied version I received a variety of broken dependencies: persistent (0.6.* vs 0.7.*), conduit (0.1.* vs 0.2.*), conduit-pool, path-pieces, attoparsec and something else. In this regard, I have a few questions. How to build these packages together? And, Michael, why so bad? -- Тимофеев Н.Д.

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Re: [Haskell-cafe] Is ListT a valid MonadPlus?
by oleg＠okmij.org 09 Feb '12

09 Feb '12

First of all, ListT is not a monad transformer, since it breaks the law of associativity of bind: *Control.Monad.List> let one = (lift $ putStrLn "1") :: ListT IO () *Control.Monad.List> let two = (lift $ putStrLn "2") :: ListT IO () *Control.Monad.List> let choice = return 1 `mplus` return 2 :: ListT IO Int *Extensible Control.Monad.List> runListT $ choice >> (one >> two) 1 2 1 2 [(),()] *Extensible Control.Monad.List> runListT $ (choice >> one) >> two 1 1 2 2 [(),()] > It appears to me that the MonadPlus instance for ListT breaks the > following MonadPlus law > m >> mzero = mzero The precise set of MonadPlus laws isn't actually agreed upon. The above law is the least agreed upon. Incidentally, this law is certainly violated for _any_ back-tracking monad transformer. Consider (lift <any action in base monad>) >> mzero for example (lift (putStrLn "printed")) >> mzero Is it reasonable to expect that printing should be undone? That the paper should be fed back into the printer and the toner lifted? There are back-tracking monad transformers; for example, LogicT.

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Is ListT a valid MonadPlus?
by Richard Wallace 09 Feb '12

09 Feb '12

It appears to me that the MonadPlus instance for ListT breaks the following MonadPlus law m >> mzero = mzero I've tried with every implementation of ListT I could find - the one in mtl, transformers, List, even "ListT done right" and it's alternative. They all seem to violate the above law. Following is a ghci session that shows this with the mtl impl. Prelude> import Control.Monad.List Prelude Control.Monad.List> let nt = ListT Nothing :: ListT Maybe Int Prelude Control.Monad.List> let e = mzero :: ListT Maybe Int Prelude Control.Monad.List> runListT nt Nothing Prelude Control.Monad.List> runListT e Just [] Prelude Control.Monad.List> runListT $ nt >> e Nothing According to the MonadPlus law above, that last line should evaluate to `Just []`. So is ListT a valid MonadPlus? Or am I missing something? If not, can a valid MonadPlus instance for ListT be written? I've tried a few things and come up short. Thanks, Rich

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Haskell Weekly News: Issue 214
by Daniel Santa Cruz 09 Feb '12

09 Feb '12

Welcome to issue 214 the HWN, a newsletter covering stories, questions, and remarks seen around the web during the week of January 29 to February 4, 2012. You can find the HTML version at: http://contemplatecode.blogspot.com/2012/02/haskell-weekly-news-issue-214.h… Quotes of the Week * Jafet: [on memoising an O(n) algorithm:] This is like trying to save work in a police investigation by having each detective determine whether another detective has already removed all evidence from his area by walking through it to search for evidence in the area. * CodeWeaver: keep in mind encryption's only as good as how much you trust that the implementors got it right. * cmccann: length [1..10^20] lambdabot: mueval-core: Time limit exceeded cmccann: looks like 10^20 is infinity * elliott: race condition waiting to happen * elliott: o'reilly publishes attoparsec tutorial: exactly the same as their parsec tutorial, but 10^-18th the size * rwbarton: Num works for Float/Double, it's Float/Double that doesn't work for Num * ddarius: Space isn't that big. * Brent Yorgey: > Sometimes, I suspect that Haskell not only makes easier of the hard > things for imperative programming languages but also makes harder of > some easy things. This is true. But usually these are things that you don't *want* to be easy, like shooting yourself in the kidney. (But these features are often described in ways that make them sound great, like "flexible usage of bullet-placement tools".) Inserting arbitrary print statements into the middle of some code is difficult for a reason. Top Reddit Stories * GHC 7.4.1 is out. Here's the release notes Domain: haskell.org, Score: 107, Comments: 59 On Reddit: [1] http://goo.gl/su4jl Original: [2] http://goo.gl/Nstve * Coming soon, to a bookstore near you Domain: yesodweb.com, Score: 82, Comments: 16 On Reddit: [3] http://goo.gl/6gZXg Original: [4] http://goo.gl/zSW1l * ImplicitCAD is a Programmatic CAD Tool/3D Modelling Engine in Haskell. Also my first big Haskell project. Feedback, advice? Domain: github.com, Score: 63, Comments: 23 On Reddit: [5] http://goo.gl/YHMRa Original: [6] http://goo.gl/39rc3 * Using monadic effects to reverse a merge sort Domain: github.com, Score: 42, Comments: 4 On Reddit: [7] http://goo.gl/dVuyp Original: [8] http://goo.gl/jL9qj * Exciting changes coming to conduit 0.2 Domain: yesodweb.com, Score: 38, Comments: 7 On Reddit: [9] http://goo.gl/neyW2 Original: [10] http://goo.gl/1ikN5 * Vectorisation without Replication in Data Parallel Haskell Domain: disciple-devel.blogspot.com, Score: 35, Comments: 4 On Reddit: [11] http://goo.gl/iJ4OD Original: [12] http://goo.gl/uMp4S * If software purity in functional languages is such an awesome idea, why are we still writing Python, Ruby or Java? Domain: self.haskell, Score: 33, Comments: 136 On Reddit: [13] http://goo.gl/F0QCY Original: [14] http://goo.gl/F0QCY * Released Data.Array.Accelerate 0.9.0.0 — the Haskell array library for GPUs Domain: justtesting.org, Score: 32, Comments: 3 On Reddit: [15] http://goo.gl/NqUwp Original: [16] http://goo.gl/JYTQ4 * Fun With -XPolyKinds : Polykinded Folds Domain: typesandotherdistractions.com, Score: 24, Comments: 1 On Reddit: [17] http://goo.gl/daxL8 Original: [18] http://goo.gl/u9gHi * Introduction to using acid-state, IxSet and data-lens as a native Haskell, noSQL, RAM-cloud database Domain: happstack.com, Score: 23, Comments: 21 On Reddit: [19] http://goo.gl/9bliO Original: [20] http://goo.gl/ZGXyW * Can't wait for the Haskell Platform? -- Compiling GHC 7.4.1 from source has never been easier. Domain: blog.jasonknight.us, Score: 21, Comments: 8 On Reddit: [21] http://goo.gl/IKjm6 Original: [22] http://goo.gl/dgMF2 * Generating random functions Domain: mainisusuallyafunction.blogspot.com, Score: 20, Comments: 6 On Reddit: [23] http://goo.gl/DB4f6 Original: [24] http://goo.gl/aOAPo * How to deal with undesired values when designing types Domain: self.haskell, Score: 19, Comments: 28 On Reddit: [25] http://goo.gl/aPCbQ Original: [26] http://goo.gl/aPCbQ * Guarded Pipes or How to write Conduit.List Combinators in Pipes. Domain: pcapriotti.wordpress.com, Score: 17, Comments: 16 On Reddit: [27] http://goo.gl/vo8ip Original: [28] http://goo.gl/mhnfH * UHC JavaScript Backend Project Page (Work in Progress) Domain: uu-computerscience.github.com, Score: 16, Comments: 0 On Reddit: [29] http://goo.gl/42xXs Original: [30] http://goo.gl/Cz8R6 Top StackOverflow Questions * What are the rules about concurrently accessing a persistent database votes: 17, answers: 1 Read on SO: [31] http://goo.gl/m3QhB * Functions don't just have types: They ARE Types. And Kinds. And Sorts. Help put a blown mind back together votes: 15, answers: 2 Read on SO: [32] http://goo.gl/fKjQR * Defining polymorphic constants in Haskell votes: 12, answers: 2 Read on SO: [33] http://goo.gl/3H3ke * Do guarded pipes behave the same as pipes using await? votes: 12, answers: 2 Read on SO: [34] http://goo.gl/Mf3HQ * What is the purpose of the IdentityT transformer? votes: 11, answers: 2 Read on SO: [35] http://goo.gl/L7Syk * call/cc implementation? votes: 10, answers: 5 Read on SO: [36] http://goo.gl/tfLLz * Understanding bind function in Haskell votes: 9, answers: 4 Read on SO: [37] http://goo.gl/amtSd * How to show that a monad is a functor and an applicative functor? votes: 8, answers: 2 Read on SO: [38] http://goo.gl/Cg0EQ * Avoiding lift with Monad Transformers votes: 7, answers: 2 Read on SO: [39] http://goo.gl/fBhCz * Container element types votes: 7, answers: 1 Read on SO: [40] http://goo.gl/UfZnG Until next time, Daniel Santa Cruz References 1. http://www.haskell.org/ghc/docs/7.4.1/html/users_guide/release-7-4-1.html 2. http://www.reddit.com/r/haskell/comments/p886g/ghc_741_is_out_heres_the_rel… 3. http://www.yesodweb.com/blog/2012/01/coming-soon 4. http://www.reddit.com/r/haskell/comments/p4hpt/coming_soon_to_a_bookstore_n… 5. https://github.com/colah/ImplicitCAD 6. http://www.reddit.com/r/haskell/comments/p9jzh/implicitcad_is_a_programmati… 7. https://github.com/DanBurton/Blog/blob/master/Literate%20Haskell/recovery.l… 8. http://www.reddit.com/r/haskell/comments/p2kar/using_monadic_effects_to_rev… 9. http://www.yesodweb.com/blog/2012/01/conduit-changes-0-2 10. http://www.reddit.com/r/haskell/comments/p1iu0/exciting_changes_coming_to_c… 11. http://disciple-devel.blogspot.com/2012/02/vectorisation-without-replicatio… 12. http://www.reddit.com/r/haskell/comments/p7f6u/vectorisation_without_replic… 13. http://www.reddit.com/r/haskell/comments/pavb1/if_software_purity_in_functi… 14. http://www.reddit.com/r/haskell/comments/pavb1/if_software_purity_in_functi… 15. http://justtesting.org/released-dataarrayaccelerate-0900-the-haskell 16. http://www.reddit.com/r/haskell/comments/p5sij/released_dataarrayaccelerate… 17. http://www.typesandotherdistractions.com/2012/02/fun-with-xpolykinds-polyki… 18. http://www.reddit.com/r/haskell/comments/p8djh/fun_with_xpolykinds_polykind… 19. http://www.happstack.com/docs/crashcourse/AcidState.html 20. http://www.reddit.com/r/haskell/comments/p75ko/introduction_to_using_acidst… 21. http://blog.jasonknight.us/2012/02/how-to-install-ghc-741-in-ubuntu-from.ht… 22. http://www.reddit.com/r/haskell/comments/pabfi/cant_wait_for_the_haskell_pl… 23. http://mainisusuallyafunction.blogspot.com/2012/02/generating-random-functi… 24. http://www.reddit.com/r/haskell/comments/p89fq/generating_random_functions/ 25. http://www.reddit.com/r/haskell/comments/p5lv0/how_to_deal_with_undesired_v… 26. http://www.reddit.com/r/haskell/comments/p5lv0/how_to_deal_with_undesired_v… 27. http://pcapriotti.wordpress.com/2012/02/02/an-introduction-to-guarded-pipes/ 28. http://www.reddit.com/r/haskell/comments/p8g55/guarded_pipes_or_how_to_writ… 29. http://uu-computerscience.github.com/uhc-js/ 30. http://www.reddit.com/r/haskell/comments/p1nqh/uhc_javascript_backend_proje… 31. http://stackoverflow.com/questions/9055214/what-are-the-rules-about-concurr… 32. http://stackoverflow.com/questions/9074261/functions-dont-just-have-types-t… 33. http://stackoverflow.com/questions/9088821/defining-polymorphic-constants-i… 34. http://stackoverflow.com/questions/9145656/do-guarded-pipes-behave-the-same… 35. http://stackoverflow.com/questions/9122825/what-is-the-purpose-of-the-ident… 36. http://stackoverflow.com/questions/9050725/call-cc-implementation 37. http://stackoverflow.com/questions/9074284/understanding-bind-function-in-h… 38. http://stackoverflow.com/questions/9098247/how-to-show-that-a-monad-is-a-fu… 39. http://stackoverflow.com/questions/9054731/avoiding-lift-with-monad-transfo… 40. http://stackoverflow.com/questions/9078168/container-element-types

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