- Haskell-Cafe - Haskell.org

cannot install regex-posix using cabal ?
by z_axis 16 Dec '10

16 Dec '10

%ghc-pkg list|grep -i regex regex-base-0.93.2 %cabal install regex-posix Resolving dependencies... Configuring regex-posix-0.94.4... Preprocessing library regex-posix-0.94.4... running dist/build/Text/Regex/Posix/Wrap_hsc_make failed command was: dist/build/Text/Regex/Posix/Wrap_hsc_make >dist/build/Text/Regex/Posix/Wrap.hs cabal: Error: some packages failed to install: regex-posix-0.94.4 failed during the building phase. The exception was: ExitFailure 1 How can i fix such a problem ? ----- e^(π.i) + 1 = 0 -- View this message in context: http://haskell.1045720.n5.nabble.com/cannot-install-regex-posix-using-cabal… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Re: [Haskell-cafe] Iteratee-like
by John Lato 16 Dec '10

16 Dec '10

> > From: Permjacov Evgeniy <permeakra(a)gmail.com> > > current links > > https://github.com/permeakra/Rank2Iteratee > https://github.com/permeakra/PassiveIteratee > > The main difference from 'original' iteratees I read about is that both > do not use 'chunks' and pass data one-by-one. So, what I wrote may be > slower, but should be easier to maintain and more transparent for ghc > optimising facilities. I wanted as clean and simple code as possible, > but it is still very, very messy at some places and I want it cleaner. > Any suggestions? I also want to check, how good ghc does its work with > this messy modules. They may become interesting benchmarks. > Have you tried comparing it to either iteratee or enumerator (which had mostly comparable performance last time I checked, with a slight edge to iteratee)? Or to Oleg's library? Try writing test cases, a simple byte-counting application, or similar, so you can compare the performance with the other versions. Both enumerator and iteratee include demo programs that you could use as a starting point. I agree that iteratees which work on a per-element level are very clean and should be amenable to optimization by GHC. It also shows a very clear relationship with stream-fusion techniques. Unfortunately when I last tried it I couldn't get acceptable performance. I was using ghc-6.12.1 IIRC, so it could be different now. John

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Strong version of 'local' for reader monad
by Brent Yorgey 16 Dec '10

16 Dec '10

Hi all, Today I wanted this function strongLocal :: (MonadReader r1 m1, MonadReader r2 m2) => (r2 -> r1) -> m1 a -> m2 a Of course, after staring at this type for ten seconds I realized that it cannot be implemented. But I wondered whether anyone has any pointers to anything related, or if anyone has good ideas for a reasonable interface that would allow this. -Brent

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typesetting with lhs2tex
by Permjacov Evgeniy 16 Dec '10

16 Dec '10

I write docs for my iteratee-like library and I have problem with lhs2tex. When I execute lhs2tex and then latex, I get a document with long typesignatures and expressions expanded beyound page margins. I attached a sourcefile I have problem with. Can someone give me an advise how to force long signatures and expressions to be broken into multible lines ?

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ghc/dph
by Johannes Waldmann 16 Dec '10

16 Dec '10

Hi, I want to use dph (data parallel haskell) for a presentation. (Nothing fancy, just compile and run some demos.) What ghc version should I use and where do I get it? I read the advice "use HEAD" but when I build from the 7.1.20101213 source snapshot, dph is not installed (should it be?) Best - J.W.

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Re: [Haskell-cafe] Beginners help
by z_axis 16 Dec '10

16 Dec '10

According to map's definition, we know the 'fs' should be a list of function. so 'p' need a [a->b] as its parameter. And the result of 'p' should be a list of function which accepts [a] and return [b]. So the type of 'p' is [a->b] -> [[a] -> [b]] hope i make it clear. ----- e^(π.i) + 1 = 0 -- View this message in context: http://haskell.1045720.n5.nabble.com/Beginners-help-tp3306796p3307470.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Haskell Weekly News: Issue 162 - December 15, 2010
by Daniel Santa Cruz 16 Dec '10

16 Dec '10

Welcome to issue 162 of the HWN, a newsletter covering developments in the [1]Haskell community in the week of December 05 - 11. Wouter Swierstra [2]sent a call for papers for the ICFP 2011 to be held in Tokyo, Japan between September 19 - 21. The announcement contains all relevant dates of importance Dmitry Astapov [3]announced the realease of haskell-mpi, "a suite of Haskell bindings to the C MPI [Message Passing Interface] and convenience APIs on top of it." David Waern [4]annouced a new version of the venerable Haddock. "This version is compatible with .haddock files produced by the version of Haddock that comes with GHC 7.0.1." Michael Snoyman [5]announced the first release of his library and executable packdeps. "This is a library and executable containing the same functionality as the original packdeps website, namely letting you know when your version bounds exclude the use of the newest version of a library available." Michael also [6]announced the second major release of the mime-mail library. This "is a package providing support for rendering multipart emails." Jasper Van der Jeugt [7]announced the 0.0.2.0 release of the digestive functors library. "The library provides a general API to input consumption, and is an upgrade of formlets." So, what went on this week? Top Reddit Stories * Cartesian Closed Comic: Résumé Domain: ro-che.info, Score: 35, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/ekiao/cartesian_closed_comic_résum… Original: http://ro-che.info/ccc/11.html * GHC blog: An overhaul of stack management, and some performance improvements Domain: hackage.haskell.org, Score: 32, Comments: 2 On Reddit: http://www.reddit.com/r/haskell/comments/emabe/ghc_blog_an_overhaul_of_stac… Original: http://hackage.haskell.org/trac/ghc/blog/stack-chunks * How do You use Emacs for Haskell Development? Domain: self.haskell, Score: 29, Comments: 10 On Reddit: http://www.reddit.com/r/haskell/comments/ehl99/how_do_you_use_emacs_for_has… Original: /r/haskell/comments/ehl99/how_do_you_use_emacs_for_haskell_development/ * Library versus Framework: Yesod's Own World Domain: docs.yesodweb.com, Score: 26, Comments: 22 On Reddit: http://www.reddit.com/r/haskell/comments/ejgen/library_versus_framework_yes… Original: http://docs.yesodweb.com/blog/yesods-own-world/ * Visualizing Haskell types part II, Gin and monotonic : Inside T5 Domain: blog.ezyang.com, Score: 24, Comments: 2 On Reddit: http://www.reddit.com/r/haskell/comments/eiaef/visualizing_haskell_types_pa… Original: http://blog.ezyang.com/2010/12/gin-and-monotonic/ * Package of the day: parallel-io: combinators for sequencing IO actions onto a thread pool Domain: hackage.haskell.org, Score: 21, Comments: 15 On Reddit: http://www.reddit.com/r/haskell/comments/ehsqo/package_of_the_day_paralleli… Original: http://hackage.haskell.org/package/parallel-io-0.2.2 * Package of the day: haskell-mpi: Control.Parallel.MPI for high performance parallel (cluster) computations in Haskell Domain: hackage.haskell.org, Score: 19, Comments: 5 On Reddit: http://www.reddit.com/r/haskell/comments/ej5av/package_of_the_day_haskellmp… Original: http://hackage.haskell.org/package/haskell-mpi-1.0.0 * From Polymorphism To Polytypism Domain: zenzike.com, Score: 19, Comments: On Reddit: http://www.reddit.com/r/haskell/comments/ejleb/from_polymorphism_to_polytyp… Original: http://zenzike.com/posts/2010-12-10-from-polymorphic-to-polytypic/ * Hussling Haskell types into Hasse diagrams : Inside T5 Domain: blog.ezyang.com, Score: 18, Comments: On Reddit: http://www.reddit.com/r/haskell/comments/eh2zw/hussling_haskell_types_into_… Original: http://blog.ezyang.com/2010/12/hussling-haskell-types-into-hasse-diagrams/ * Building a business with Haskell: Case Studies: Cryptol, HaLVM and Copilot Domain: corp.galois.com, Score: 17, Comments: 1 On Reddit: http://www.reddit.com/r/haskell/comments/ejmwq/building_a_business_with_has… Original: http://corp.galois.com/blog/2010/12/10/building-a-business-with-haskell-cas… Top StackOverflow Questions * What is the benefit of purely functional data structure? votes: 15, answers: 4 Read on SO: http://stackoverflow.com/questions/4399837/what-is-the-benefit-of-purely-fu… * Haskell: Equation Expander 1+(1+(1+(1+(…))))=∞ votes: 9, answers: 2 Read on SO: http://stackoverflow.com/questions/4404663/haskell-equation-expander-1111 * Pure Functional Language: Haskell votes: 7, answers: 6 Read on SO: http://stackoverflow.com/questions/4382223/pure-functional-language-haskell * How does a haskell compiler works? votes: 7, answers: 4 Read on SO: http://stackoverflow.com/questions/4385160/how-does-a-haskell-compiler-works * Haskell typeclasses and C++ template classes votes: 7, answers: 6 Read on SO: http://stackoverflow.com/questions/4411279/haskell-typeclasses-and-c-templa… * Are there any special challenges for functional programming in an embedded environment? votes: 7, answers: 1 Read on SO: http://stackoverflow.com/questions/4418617/are-there-any-special-challenges… * Haskell: Where vs. Let votes: 6, answers: 3 Read on SO: http://stackoverflow.com/questions/4362328/haskell-where-vs-let * What are some good example haskell projects? votes: 6, answers: 2 Read on SO: http://stackoverflow.com/questions/4369962/what-are-some-good-example-haske… * Program Structure — Simple Commandline To Do List App — What's the Haskell way? votes: 6, answers: 2 Read on SO: http://stackoverflow.com/questions/4383512/program-structure-simple-command… * Learning to read haskell in english votes: 6, answers: 4 Read on SO: http://stackoverflow.com/questions/4393908/learning-to-read-haskell-in-engl… Quotes of the Week * kmc: it's great how laziness lets you ignore the order of evaluation except all the times when it doesn't * tg_: I can't wait until 100 years from now when 'eating food' will be deprecated from our lexicon in favor of 'oming noms' * kmc: maybe the 9,639,482nd time we argue about C++ we will finally resolve the issue * Berengal: * ddarius liked xmonad better when it was 90 lines... * Berengal liked xmonad better when it was on vinyl About the Haskell Weekly News New editions are posted to [8]the Haskell mailing list as well as to [9]the Haskell Sequence and [10]Planet Haskell. [11]RSS is also available, and headlines appear on [12]haskell.org. To help create new editions of this newsletter, please send stories to dstcruz * at * gmail * dot * com. The code used to produce this version of the newsletter is not yet publicly available, as it is a complete hack designed to get things started again. Until next time, Daniel Santa Cruz References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.general/18355 3. http://article.gmane.org/gmane.comp.lang.haskell.general/18357 4. http://groups.google.com/group/fa.haskell/browse_thread/thread/b0c838a2249f… 5. http://article.gmane.org/gmane.comp.lang.haskell.cafe/84141 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/84142 7. http://article.gmane.org/gmane.comp.lang.haskell.cafe/84201 8. http://www.haskell.org/mailman/listinfo/haskell 9. http://sequence.complete.org/ 10. http://planet.haskell.org/ 11. http://sequence.complete.org/node/feed 12. http://haskell.org/

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Gtk 0.12.0, Windows 7, Haskell Platform 2010.2.0.0, build error
by aditya siram 16 Dec '10

16 Dec '10

Hi all, I am having some issues building Gtk2Hs on Windows 7. It completes compiling the whole thing and then errors out with this message: Registering gtk-0.12.0... setup.exe: WARNING: cache is out of date: c:/Program Files/Haskell Platform/2010.2.0.0\lib\package.conf.d\package.cache use 'ghc-pkg recache' to fix. gtk-0.12.0: library-dirs: c:/devel/dist/win32/libpng-1.4.3-1/lib doesn't exist or isn't a directory (use --force to override) cabal.exe: Error: some packages failed to install: gtk-0.12.0 failed during the building phase. The exception was: ExitFailure 1 I'm not sure why it's looking at c:/devel/dist/win32/libpng-1.4.3-1/lib and I couldn't find any reference to this directory in the source tree. I tried to do a ghc-pkg recache but I get the follow permissions error: ghc-pkg.exe: c:/Program Files/Haskell Platform/2010.2.0.0\lib\package.conf.d\package.cache: you don't have permission to modify this file I changed this file to be world-writeable but with the same results. I get the same error if I try and cabal install gtk. Thanks for your help. -deech

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installing gtk2
by Max Buchholz 15 Dec '10

15 Dec '10

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par / pseq example
by J. Waldmann 15 Dec '10

15 Dec '10

I was trying to find an easy example for par/pseq, and I finally used plain mergesort ( on Prelude.[] ) and I observed that it is best to give +RTS -A1G (or more) such that there are only very few garbage collections. This roughly cuts execution time in half (from +RTS -N1 to -N4, on an i7 CPU) which is nice for a demonstration. The following is the very straightforward program that I use. Is it OK? I'm not asking for a faster sort algorithm, but whether par/pseq is used correctly/idiomatically in this program (so that students don't get a wrong impression). msort [] = [] ; msort [x] = [x] msort xs = let ( here, there ) = splitAt ( div ( length xs ) 2 ) xs mshere = msort here msthere = msort there in last mshere `par` last msthere `pseq` merge mshere msthere merge [] ys = ys ; merge xs [] = xs merge (x:xs) (y:ys) = if x < y then x : merge xs (y:ys) else y : merge (x:xs) ys Thanks - J.W.

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