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Job Opportunity at Parallel Scientific
by Peter Braam 21 Nov '11

21 Nov '11

Parallel Haskell Programmers Parallel Scientific, LLC is a Boulder, CO based early stage, but funded startup company working in the area of scalable parallelization for scientific and large data computing. We are implementing radically new software tools for the creation and optimization of parallel programs benefiting applications and leveraging modern systems architecture. We build on our mathematical knowledge, cutting edge programming languages and our understanding of systems software and hardware. We are currently working with the Haskell development team and major HPC laboratories world wide on libraries and compiler extensions for parallel programming. Parallel Scientific was founded by Peter Braam in 2010. Peter formerly taught mathematics and computer science at Oxford and Carnegie Mellon. Then he contributed file systems to Linux and invented Lustre (which provides storage to 9 of the top 10 systems in the world). He ran several successful startups, and Parallel Scientific is run by an very experienced management team and board. Successful candidates can in some cases work remotely and will work in a modern virtual environment. We provide training in advanced processes for software design and implementation and domain specific knowledge. Required skills: - Very strong background in computer science or mathematics - Experience with Haskell - Knowledge of systems programming and operating systems functionality - Knowledge of system architectures, such as high performance networking, memory architectures, multi and manycore CPUs and GPGPUs - Experience with performance tuning of parallel or concurrent algorithms - Experience designing and implementing concurrent or parallel programs Experience in one or more of the following areas is desirable: - Experience with Haskell compiler technology - In depth knowledge of core Haskell libraries for parallel programming (NDP, REPA etc) - Experience in the area of middleware algorithms for data flow programming, graphs, cloud based data analytics, or sparse matrices - Domain specific knowledge in scientific programming areas related to irregular and sparse problems, e.g. data analytics using graph analysis, genomics, tightly connected numerical analysis - Experience with performance tuning for parallel applications on multi core systems (e.g. with the Intel toolkit), for GPGPU's using Cuda/OpenCL or with MPI/OpenMP on clusters of SMPs To apply, please send a resume to jobs(a)parsci.com.

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Interpreter with Cont
by Tim Baumgartner 21 Nov '11

21 Nov '11

Hi all, I wrote a simple interpreter that can be run in the console: data Interaction a b = Exit b | Output b (Interaction a b) | Input (a -> Interaction a b) runConsole :: Interaction String String -> IO () runConsole (Exit b) = putStrLn $ "Finished. Result: " ++ b runConsole (Output s cont) = putStrLn s >> runConsole cont runConsole (Input f) = putStr "> " >> getLine >>= runConsole . f interpreter :: Int -> Interaction String String interpreter i = interaction where interaction = Input input input "exit" = Exit (show i) input "inc" = Output "ok" $ interpreter (i+1) input "show" = Output (show i) interaction input "hello"= Output "Hello World!" interaction input s = Output ("Whas's '" ++ s ++ "' ?") interaction main = runConsole . Output "Known commands: show, inc, hello, exit" $ interpreter 5 I have not yet gained a good understanding of the continuation monad, but I wonder if it could be used here. What would a clean solution look like? Perhaps there are other things that need to be changed as well? Regards, Tim

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Superset of Haddock and Markdown
by Johan Tibell 21 Nov '11

21 Nov '11

Hi all, I spent some time today documenting a library and the experience left me wanting a better markup language. In particular, Haddock lacks: * markup for bold text: bold text works better than italics for emphasis on computer monitors. * hyperlinks with anchor texts: having the actual URL rendered inline with text hurts readability. Could Haddock markup be extended to also include some Markdown features? The new features could be hidden behind a flag so old documentation doesn't get unwanted markup (e.g. if it uses *...* to not mean bold). P.S. This good make a good weekend hack that shouldn't be too difficult. -- Johan

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Lifted Spine View
by bob zhang 21 Nov '11

21 Nov '11

Hi, all I tried to follow the program of the paper "Scrap your boilerpolate" Revolutions. Unfortunately, I found the program in the section lifted spine view does not compile in my GHC, could anybody point out where I am wrong? Many Thanks My code is posted herehttp://hpaste.org/54357

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Deduce problem.
by Magicloud Magiclouds 21 Nov '11

21 Nov '11

Hi, Consider I have declarations like this: class (ClassA a) => ClassC a where from :: (ClassB b) => a -> [b] to :: (ClassB c) => a -> [c] data H = ... instance ClassB H where ... data Test = Test { m :: H } instance ClassA Test where ... instance ClassC Test where from = m to = m Well, I got "could not deduce" error here at "from = m" and "to = m". `c' is a rigid type variable bound by the type signature for to :: ClassB c => Test -> [c]. Referring to some similar questions on internet, I should remove the (ClassB c) thing. Is this the only solution? -- 竹密岂妨流水过山高哪阻野云飞

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thread blocked indefinitely in an STM transaction
by Eric Wong 21 Nov '11

21 Nov '11

Hi everyone, I'm writing an API server using the snap framework with the new snaplet infrastructure. In order to connect with the database, I'm using snaplet-hdbc, HDBC, HDBC-mysql. (I'm using InnoDB for storage engine so it can process transaction). Every query is wrapped in the function withTransaction' so I don't have to commit or rollback by hand. If there's a SqlError raised, I will catch it, log the error and return an error message to the client side. But when running the program, if there's a DB error, the process will be blocked and there's an error message: " thread blocked indefinitely in an STM transaction". There's no STM related code in my code. Do you have any idea on this error and how to process this? Thanks. Eric.

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os.path.expanduser analogue
by Ben Gamari 21 Nov '11

21 Nov '11

On the whole, the filepath package does an excellent job of providing basic path manipulation tools, one weakness is the inability to resolve "~/..." style POSIX paths. Python implements this with os.path.expanduser. Perhaps a similar function might be helpful in filepath? Cheers, - Ben Possible (but untested) implementation expandUser :: FilePath -> IO FilePath expandUser p = if "~/" `isPrefixOf` p then do u <- getLoginName return $ u ++ drop 2 p else return p

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Visi.Pro -- My Next Thing
by David Pollak 20 Nov '11

20 Nov '11

Howdy Haskeller, I've launch a new, Haskell powered, adventure: Visi.Pro, Cloud Computing for the Rest of Us. Visi.Pro will offer a HyperCard-like development environment that will empower normal people to build and run beautiful, interactive apps on their iPad and seamlessly integrate the Cloud including real-time data feeds and destinations. More about the journey that led me to Visi.Pro at http://blog.visi.io/ and more about the product vision at http://visi.pro (http://visi.pro/) I am totally stoked about where this journey will lead... it's going to be amazingly exciting! I'm also looking forward to taking advantage of Haskell awesomeness as I build Visi.Pro and Visi.io out. Haskell has been a wonderful journey for me so far. The quality in design and implementation of the language, the runtime, and the libraries is amazing. I am standing on the shoulders of giants by building Visi.Pro on Haskell. Thanks! David -- @dpp

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Re: [Haskell-cafe] [Haskell-beginners] Int V.S. Word32
by Haisheng Wu 20 Nov '11

20 Nov '11

Hmm... I think I made a little confusion so I put my finding here: http://haisgwu.info/posts/2011-11-20-euler-problem-14.html I do got stack overflow thus need several compile opts to fix it. Not sure if it is what you mean by "You get overflow using 32-bit types here." -Haisheng On Sat, Nov 19, 2011 at 10:49 PM, Daniel Fischer < daniel.is.fischer(a)googlemail.com> wrote: > On Saturday 19 November 2011, 09:09:50, Haisheng Wu wrote: > > Hello, > > I got great performance difference for the following code if I used > > type `Int` rather than `Data.Word.Word32`. > > Anyone can help to explain why such difference? > > Short answer: GHC optimises Int calculations far better than Word32 > calculations, rather, it optimises more calculations for Int than for > Word32. It also optimises more calculations for Word than for Word32, but > not as many as for Int. > > The reason is that Int (and Word) are (at least expected to be) far more > often used, so the effort has gone to these types primarily. Work is being > done to get the fixed-width types on par, but it's not around the corner > yet. > > You can try using Word instead of Word32, that's likely to be faster. > > But > > > Thanks a lot. > > > > -Simon > > > > module Main where > > import Data.Word > > > > main :: IO () > > main = print $ p14 > > > > p14 = maximum [ (startChain n 0, n) | n <- [2..1000000] ] > > You get overflow using 32-bit types here. > > > > > startChain :: Word32 -> Int -> Int > > startChain 1 count = count + 1 > > startChain n count = startChain (intTransform n) (count+1) > > > > intTransform :: Word32 -> Word32 > > intTransform n > > > > | even n = n `div` 2 > > | otherwise = 3 * n + 1 > >

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Problems with installing the correct version of "process". Help?
by Blaine 20 Nov '11

20 Nov '11

Hi everyone. I'm new to haskell (venturing over from python land); i can't figure this one problem out. This has been incredibly difficult to solve, and it is quite discouraging! i'm trying to get berp up and running ( https://github.com/bjpop/berp/) berp-libs installed fine, berp-compiler is hanging up: >From what I can tell, the only hangup I have is that the "process" package depends on the wrong version of "directory". [blaine@macbook:~/Dropbox/src/berp/compiler Tue Nov 15] 75$ cabal configure Resolving dependencies... Configuring berpcompiler-0.0.3... Warning: This package indirectly depends on multiple versions of the same package. This is highly likely to cause a compile failure. *package process-1.0.1.3 requires directory-1.0.1.0* package cpphs-1.13.2 requires directory-1.1.0.1 package berplibs-0.0.3 requires directory-1.1.0.1 package berpcompiler-0.0.3 requires directory-1.1.0.1 OK so I need to rebuild process so it uses the newest version of directory like the rest of them (I have no idea if this is the right thing to do, but this is what i did with cpphs and it worked). But when I try and build process, it can't find a header on my file that does exist. I also did successfully install from source package manually (using these instructions<http://www.haskell.org/haskellwiki/Cabal/How_to_install_a_Cabal_package>on the package downloaded from here <http://hackage.haskell.org/package/process-1.0.1.3>, which worked fine, but didn't seem update the dependency to rely on the newest version of directory (aka still can't configure berp). I don't know where to go from here. Please note: I have installed from source package, so even if I fix this cabal issue I'm not sure it will fix the dependency issue (but who knows, maybe it will). I'm having a hard time scaring up internet resources on where to proceed. What am I doing wrong? Thanks so much in advance, Blaine Reference: 22$ uname -a Linux macbook 2.6.32-34-generic #77-Ubuntu SMP Tue Sep 13 19:39:17 UTC 2011 x86_64 GNU/Linux (Here I am trying to force include the directory where the missing header file lives. It does exist but cabal won't have it) [blaine@macbook:~/Dropbox/src/berp/compiler Tue Nov 08] 92$ sudo cabal --extra-include-dirs=/usr/lib/ghc-6.12.1/process-1.0.1.2/include/ install process Resolving dependencies... Configuring process-1.1.0.0... configure: WARNING: unrecognized options: --with-compiler checking for gcc... gcc checking whether the C compiler works... yes checking for C compiler default output file name... a.out checking for suffix of executables... checking whether we are cross compiling... no checking for suffix of object files... o checking whether we are using the GNU C compiler... yes checking whether gcc accepts -g... yes checking for gcc option to accept ISO C89... none needed checking how to run the C preprocessor... gcc -E checking for grep that handles long lines and -e... /bin/grep checking for egrep... /bin/grep -E checking for ANSI C header files... yes checking for sys/types.h... yes checking for sys/stat.h... yes checking for stdlib.h... yes checking for string.h... yes checking for memory.h... yes checking for strings.h... yes checking for inttypes.h... yes checking for stdint.h... yes checking for unistd.h... yes checking for pid_t... yes checking vfork.h usability... no checking vfork.h presence... no checking for vfork.h... no checking for fork... yes checking for vfork... yes checking for working fork... yes checking for working vfork... (cached) yes checking signal.h usability... yes checking signal.h presence... yes checking for signal.h... yes checking sys/wait.h usability... yes checking sys/wait.h presence... yes checking for sys/wait.h... yes checking fcntl.h usability... yes checking fcntl.h presence... yes checking for fcntl.h... yes checking for setitimer,... no checking for sysconf... yes checking value of SIG_DFL... -1 checking value of SIG_IGN... -1 configure: creating ./config.status config.status: creating include/HsProcessConfig.h config.status: include/HsProcessConfig.h is unchanged configure: WARNING: unrecognized options: --with-compiler cabal: Missing dependency on a foreign library: ** Missing header file: runProcess.h* This problem can usually be solved by installing the system package that provides this library (you may need the "-dev" version). If the library is already installed but in a non-standard location then you can use the flags --extra-include-dirs= and --extra-lib-dirs= to specify where it is. cabal: Error: some packages failed to install: process-1.1.0.0 failed during the configure step. The exception was: ExitFailure 1 [blaine@macbook:~/Dropbox/src/berp/compiler Tue Nov 08] 93$ ls /usr/lib/ghc-6.12.1/process-1.0.1.2/include/ HsProcessConfig.h *runProcess.h* Blaine

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ANNOUNCE: SmallCheck 0.5
by Roman Cheplyaka 19 Nov '11

19 Nov '11

Following the recent discussion on Haskell-Cafe, I've taken over maintainership of SmallCheck. This is to announce a new minor release, SmallCheck 0.5. It fixes build on GHC 7.2 and makes a few cosmetic changes. http://hackage.haskell.org/package/smallcheck-0.5 In the future there will be more releases that hopefully will make SmallCheck more convenient to use. Feel free to submit bugs, wishes and patches through github: https://github.com/feuerbach/smallcheck -- Roman I. Cheplyaka :: http://ro-che.info/

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Const vs Constant types
by Denis Moskvin 19 Nov '11

19 Nov '11

Is there any rationale for coexistence of newtype Const a b = Const { getConst :: a } from Control.Applicative and newtype Constant a b = Constant { getConstant :: a } from Data.Functor.Constant (transformers package)? Denis Moskvin

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Documenting strictness properties for Data.Map.Strict
by Johan Tibell 19 Nov '11

19 Nov '11

Hi all, Data.Map is getting split into Data.Map.Lazy and Data.Map.Strict (with Data.Map re-exporting the lazy API). I want to better document the strictness properties of the two new modules. Right now the documentation for Data.Map.Strict reads: Strictness properties ===================== * All functions are strict in both key and value arguments. Examples: insertWith (+) k undefined m == undefined delete undefined m == undefined * Keys and values are evaluated to WHNF before they are stored in the map. Examples: map (\ v -> undefined) == undefined mapKeys (\ k -> undefined) == undefined I'm not entirely happy with this formulation. I'm looking for something that's clear (i.e. precise and concise, without leaving out important information), assuming that the reader already knows how lazy evaluation works at a high level. Ideas? Cheers, Johan

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Stream fusion
by Yves Parès 18 Nov '11

18 Nov '11

Hello, While re-reading RealWorldHaskell, chapter 25, I saw that -- unlike I believed -- loop fusion wasn't activated by default under GHC for lists (but that module Data.List.Stream from package stream-fusion could provide it). Is that still the case? If not, then are there some cases of list processing where loop fusion would be a bad thing? (Ergo cases where you should stick to Prelude/Data.List functions and not use Data.List.Stream implementation) Thanks.

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[ANN] transformers-base, transformers-abort, monad-abort-fd
by Mikhail Vorozhtsov 18 Nov '11

18 Nov '11

Hi Cafe. I've been using these three small transformer libraries for awhile, so it's probably time to announce them. transformers-base[1] introduces a generalized version of MonadIO, MonadBase (BaseM in monadLib terms). It's very useful when you are trying to make a stateful API work in both IO and STM (and all transformer stacks on top of them). transformers-abort[2] basically gives you two versions of EitherT, one for errors and one for short-circuiting. Includes instances for semigroupoids and monad-control classes. monad-abort-fd[3] is a typical companion auto-lifter package for transformers-abort. But it also provides a generalized version[4] of Control.Exception which tries to thread effects properly (e.g. finalizers can read (if control didn't escape) and modify the state in StateT). [1] http://hackage.haskell.org/package/transformers-base [2] http://hackage.haskell.org/package/transformers-abort [3] http://hackage.haskell.org/package/monad-abort-fd [4] http://hackage.haskell.org/packages/archive/monad-abort-fd/0.3/doc/html/src…

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Can I have an alias for selector?
by Magicloud Magiclouds 18 Nov '11

18 Nov '11

Hi, For example: "data A = B { c :: Int }". Then I must use it this way "(B 0) { c = 1 }". Anyway I could make it like "(B 0) { d = 1 }"? -- 竹密岂妨流水过山高哪阻野云飞

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Re: [Haskell-cafe] Deduce problem.
by oleg＠okmij.org 17 Nov '11

17 Nov '11

Multi-parameter type classes are more flexible. Here is how you can write your old code: > {-# LANGUAGE MultiParamTypeClasses, FlexibleInstances #-} > > class (ClassA a, ClassB b) => ClassC a b where > from :: a -> [b] > to :: a -> [b] > > data H = H > > class ClassA a where toInt :: a -> Int > class ClassB b where fromInt :: Int -> b > > instance ClassB H where fromInt _ = H > > data Test = Test { m :: H } > instance ClassA Test where toInt _ = 0 > > instance ClassC Test H where > from = (:[]) . m > to = (:[]) . m The constraints in the ClassC a b declaration specify that in all instances of ClassC, the type a must be in ClassA and the type b must be in ClassB. This is the case for the "ClassC Test H" instance. You can also specify that for some particular 'a' the function 'from' can produce the value of the type [b] for any b in ClassB. The caller will determine which b it wants. This is similar to your original intention, as I understand. > instance ClassA Int where toInt = id > > instance ClassB b => ClassC Int b where > from x = [fromInt x] > > t1:: [H] > t1 = from (5::Int)

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ANNOUNCE: graphviz-2999.12.0.4
by Ivan Lazar Miljenovic 17 Nov '11

17 Nov '11

I've uploaded version 2999.12.0.4. This release fixes the problem described by Max Rabkin below (who also determined how to fix: I *always* get tripped up by asTypeOf :s). It also has improved documentation to help people that are wanting to construct Dot graphs explicitly, and cleans up error messages produced when provided Dot code isn't parseable (along with hints for common solutions). On 11 November 2011 02:19, Max Rabkin <max.rabkin(a)gmail.com> wrote: > My understanding of the documentation for Data.GraphViz.dotizeGraph > and graphToGraph is that they should add position attributes to a > graph. But they always seem to return graphs with empty attribute > lists. What am I doing wrong in the following tiny example? > >> dotizeGraph nonClusteredParams (insNode (0, "Blah") $ empty :: Gr String ()) > > 0:([],"Blah")->[] > > I expected the first list to contain at least a Pos attribute. > > I have written a wrapper around /usr/share/dot which shows the program > is outputting positional information. > > --Max > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Haskell Weekly News: Issue 208
by Daniel Santa Cruz 17 Nov '11

17 Nov '11

Welcome to issue 208 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of November 6 to 12, 2011. You can find the HTML version at: http://contemplatecode.blogspot.com/2011/11/haskell-weekly-news-issue-208.h… New and Updated Projects * GHC (Ian Lynagh; 7.2.2) bugfix release for the 7.2 branch. [1] http://goo.gl/eB4X6 * CoreErlang (Alex Kropivny; 0.0.2) New maintainer, plus some bug fixes. [2] http://goo.gl/TMUWs * virthualenv (Bartek ƒwik≈owski) A tool inspired by Python's virtualenv. [3] http://goo.gl/3Jvc0 * transformers-base, transformers-abort, monad-abort-fd (Mikhail Vorozhtsov). [4] http://goo.gl/DRNgt Quotes of the Week * Nimatek: People shouldn't be able to add two and two in Haskell without knowing monoids! * shachaf: Sometimes things are complicated because the domain is complicated. Other times things are complicated because edwardk. * shachaf: It's-a me, MonadIO! * elliott: a typeclass is nothing without semantics * Jafet: I didn't know what your question was so I answered the question that I liked * steakknife: Skip multidimensional types and go straight types that can express general relativity. * ddarius: "use the right platitude for the job" * balor: hmm....do not try to compile a file with a 30mb string in it Top Reddit Stories * Quick poll: upvote if you think GHC should enable -O by default, downvote if you think -O0 should continue to be the default Domain: self.haskell, Score: 68, Comments: 46 On Reddit: [5] http://goo.gl/q43Ur Original: [6] http://goo.gl/q43Ur * What's going on with "id id id ... id 0"? Domain: self.haskell, Score: 46, Comments: 25 On Reddit: [7] http://goo.gl/a57l0 Original: [8] http://goo.gl/a57l0 * HaskellDB: A long tutorial Domain: chrisdone.com, Score: 45, Comments: 6 On Reddit: [9] http://goo.gl/FYBiU Original: [10] http://goo.gl/794G2 * The Agda mailing list has the best questions [somewhat off topic] Domain: lists.chalmers.se, Score: 41, Comments: 1 On Reddit: [11] http://goo.gl/ec5gB Original: [12] http://goo.gl/ODpKV * Virtual Haskell Environment Domain: paczesiowa.blogspot.com, Score: 40, Comments: 33 On Reddit: [13] http://goo.gl/17qDB Original: [14] http://goo.gl/V7onW * Why doesn't Haskell's Prelude.read return a Maybe? Domain: stackoverflow.com, Score: 39, Comments: 44 On Reddit: [15] http://goo.gl/vceL7 Original: [16] http://goo.gl/ETu1j * First release of Kansas Lava Domain: ittc.ku.edu, Score: 32, Comments: 1 On Reddit: [17] http://goo.gl/bj8vw Original: [18] http://goo.gl/nhAho * A major new release of the statistics library Domain: serpentine.com, Score: 28, Comments: 2 On Reddit: [19] http://goo.gl/dYwQd Original: [20] http://goo.gl/7QkKY * TRYDSH - Test Your Code Domain: dbwiscam.informatik.uni-tuebingen.de, Score: 27, Comments: 3 On Reddit: [21] http://goo.gl/qbZyA Original: [22] http://goo.gl/IiRf6 * ScalableServer-0.1 - Providing an easy API for attoparsec/enumerator/blaze based TCP services Domain: github.com, Score: 20, Comments: 14 On Reddit: [23] http://goo.gl/aXqQ7 Original: [24] http://goo.gl/Z1zcm * Python 3 Implementation in Haskell [x-post from programming.reddit.com] Domain: reddit.com, Score: 19, Comments: 0 On Reddit: [25] http://goo.gl/lDJBr Original: [26] http://goo.gl/UrWld * let's derive Eq.(==) -- reflexivity not guaranteed Domain: self.haskell, Score: 16, Comments: 11 On Reddit: [27] http://goo.gl/1ANU9 Original: [28] http://goo.gl/1ANU9 * Haskell and High-Performance Computing (HPC) Domain: self.haskell, Score: 16, Comments: 7 On Reddit: [29] http://goo.gl/AZQPv Original: [30] http://goo.gl/AZQPv Top StackOverflow Questions * Why doesn't Haskell's Prelude.read return a Maybe? votes: 29, answers: 4 Read on SO: [31] http://goo.gl/ETu1j * Choosing between a class and a record votes: 27, answers: 3 Read on SO: [32] http://goo.gl/Dn5FT * Function using foldr is too eager votes: 9, answers: 3 Read on SO: [33] http://goo.gl/jUJxG * Odd results from monad transformer benchmark. A bug? votes: 9, answers: 2 Read on SO: [34] http://goo.gl/qlvDj * Binary instance for an existential votes: 8, answers: 3 Read on SO: [35] http://goo.gl/cHzhb * GHC Install Without Root votes: 7, answers: 2 Read on SO: [36] http://goo.gl/mJnx5 * Fixed point combinator in Haskell votes: 7, answers: 5 Read on SO: [37] http://goo.gl/K4VcI * What's the best way to write facebook apps in haskell? votes: 6, answers: 1 Read on SO: [38] http://goo.gl/HeXOp * Creating a list by cumulatively adding elements of another list: Haskell votes: 6, answers: 4 Read on SO: [39] http://goo.gl/neP6s * ghci environment dump votes: 6, answers: 2 Read on SO: [40] http://goo.gl/EnKpp Until next time, Daniel Santa Cruz References 1. http://permalink.gmane.org/gmane.comp.lang.haskell.general/19017 2. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/93712 3. http://permalink.gmane.org/gmane.comp.lang.haskell.general/19011 4. http://permalink.gmane.org/gmane.comp.lang.haskell.cafe/93802 5. http://www.reddit.com/r/haskell/comments/m5yhx/quick_poll_upvote_if_you_thi… 6. http://www.reddit.com/r/haskell/comments/m5yhx/quick_poll_upvote_if_you_thi… 7. http://www.reddit.com/r/haskell/comments/m7uph/whats_going_on_with_id_id_id… 8. http://www.reddit.com/r/haskell/comments/m7uph/whats_going_on_with_id_id_id… 9. http://chrisdone.com/posts/2011-11-06-haskelldb-tutorial.html 10. http://www.reddit.com/r/haskell/comments/m2df2/haskelldb_a_long_tutorial/ 11. https://lists.chalmers.se/pipermail/agda/2011/003493.html 12. http://www.reddit.com/r/haskell/comments/m8iwo/the_agda_mailing_list_has_th… 13. http://paczesiowa.blogspot.com/2011/11/virtual-haskell-environment.html 14. http://www.reddit.com/r/haskell/comments/m39v5/virtual_haskell_environment/ 15. http://stackoverflow.com/questions/8066850/why-doesnt-haskells-prelude-read… 16. http://www.reddit.com/r/haskell/comments/m7agm/why_doesnt_haskells_preluder… 17. http://ittc.ku.edu/csdl/fpg/Tools/KansasLava 18. http://www.reddit.com/r/haskell/comments/m3nss/first_release_of_kansas_lava/ 19. http://www.serpentine.com/blog/2011/11/10/a-major-new-release-of-the-haskel… 20. http://www.reddit.com/r/haskell/comments/m8cox/a_major_new_release_of_the_s… 21. http://dbwiscam.informatik.uni-tuebingen.de/trydsh/ 22. http://www.reddit.com/r/haskell/comments/m9s37/trydsh_test_your_code/ 23. https://github.com/jamwt/haskell-scalable-server 24. http://www.reddit.com/r/haskell/comments/m4cz0/scalableserver01_providing_a… 25. http://www.reddit.com/r/programming/comments/m4rbs/python_3_implementation_… 26. http://www.reddit.com/r/haskell/comments/m5l1u/python_3_implementation_in_h… 27. http://www.reddit.com/r/haskell/comments/m9975/lets_derive_eq_reflexivity_n… 28. http://www.reddit.com/r/haskell/comments/m9975/lets_derive_eq_reflexivity_n… 29. http://www.reddit.com/r/haskell/comments/m9s9p/haskell_and_highperformance_… 30. http://www.reddit.com/r/haskell/comments/m9s9p/haskell_and_highperformance_… 31. http://stackoverflow.com/questions/8066850/why-doesnt-haskells-prelude-read… 32. http://stackoverflow.com/questions/8106764/choosing-between-a-class-and-a-r… 33. http://stackoverflow.com/questions/8032228/function-using-foldr-is-too-eager 34. http://stackoverflow.com/questions/8092787/odd-results-from-monad-transform… 35. http://stackoverflow.com/questions/8101067/binary-instance-for-an-existenti… 36. http://stackoverflow.com/questions/8084832/ghc-install-without-root 37. http://stackoverflow.com/questions/8099349/fixed-point-combinator-in-haskell 38. http://stackoverflow.com/questions/8052177/whats-the-best-way-to-write-face… 39. http://stackoverflow.com/questions/8059057/creating-a-list-by-cumulatively-… 40. http://stackoverflow.com/questions/8067368/ghci-environment-dump

1 0

doctest: Interpreter exited with an error: ExitFailure 127
by informationen 17 Nov '11

17 Nov '11

Hi, i have upgraded to doctest version 0.4.1. Now when i try to run the example from the webpage, i get: doctest: Interpreter exited with an error: ExitFailure 127 What's wrong here and how can i fix it? Kind regards Chris This is the content of Fib.hs: module Fib where -- | Compute Fibonacci numbers -- -- Examples: -- -- >>> fib 10 -- 55 -- -- >>> fib 5 -- 5 fib 0 = 0 fib 1 = 1 fib n = fib (n - 1) + fib (n - 2) main = do print $ fib 4

3 4

Tutorial/slides on pretty-printing combinators?
by Sean Leather 17 Nov '11

17 Nov '11

Do you know of any tutorial or slides from a talk on one of the pretty-printing libraries? It could be on Text.PrettyPrint.HughesPJ or uulib or any other, similar library. I'm thinking of developing slides for a course, and I'm looking for sources of inspiration. Regards, Sean

4 3

Re: [Haskell-cafe] Amazon AWS storage best to use with Haskell?
by dokondr 16 Nov '11

16 Nov '11

On Mon, Oct 31, 2011 at 6:50 PM, John Lenz <lenz(a)math.uic.edu> wrote: > CouchDB works great, although I decided to go with SimpleDB since then it > is amazon's problem to scale and allocate disk and so forth, which I like > better. For couchdb, you can use my package couchdb-enumerator on hackage. > > > Regarding CouchDB. So far I have my records keyed by Id and stored in Data.Map which I serialize to text file. Using Data.Map functions I do many operations with these records including mapping functions over keys and values, accumulation, lookup, intersection, union etc. When I move this data to CouchDB and start using couchdb-enumerator to work with it, how natural will it be to implement all these functions that I use from Data.Map? Or maybe it makes more sense to store my serialized Data.Map as a blob in CouchDB? And do not use views or similar CouchDB / SimpleDB interfaces at all? Just retrieve necessary blob and deserialize it to Data.Map, update and then store modified blob to CouchDB again? It would be great if somebody had time to implement Data.List, Data.Map, etc on top of generic NoSQL DB interface with specific instances for CouchDB, SimpleDB, etc.

4 9

Dutch National FP Day 2012
by Sean Leather 16 Nov '11

16 Nov '11

(Sent on behalf of Doaitse Swierstra) Despite some last minute changes to the planning we are happy to announce that the next Dutch functional programming day will take place on January 6, 2012, at the university campus "De Uithof" of Utrecht University. In case you want to give a presentation please send title, speaker and abstract to doaitse(a)swierstra.net before Dec 1. We will collect the proposals and try to make an interesting program out of it. Further details will be placed on the site: http://www.cs.uu.nl/wiki/FPDag2012 Best, hoping to see you all, Doaitse

3 3

How to Create Programming Language with Haskell?
by Shogo Sugamoto 16 Nov '11

16 Nov '11

Hi,Cafe. I want to create my own Programming Language with Haskell, and I learn how to do it. I read: WikiBooks of "Write Yourself a Scheme in 48 Hours", "Real World Haskell" of Chapter "Using Parsec", Source of "HJS", Book of "Introduction of Functional Programming Using Haskell". Ok,What is another good source creating my own Programming Language with Haskell? Thanks :) esehara

3 2

(no subject)
by Benjamin L. Russell 16 Nov '11

16 Nov '11

http://elikat.com/blogs/wp-content/plugins/index1.php

1 0

Re: [Haskell-cafe] A Mascot
by heathmatlock 16 Nov '11

16 Nov '11

On Tue, Nov 15, 2011 at 7:06 PM, Ivan Lazar Miljenovic < ivan.miljenovic(a)gmail.com> wrote: > Ummmmm.... do we _really_ need a mascot? I don't think a programming community every really needs a mascot, just nice to have. > And no offence to your > artistic abilities, but even if we did, I don't see how a lamb relates > to Haskell :/ > > The lamb is a play on lambda calculus. -- Heath Matlock +1 256 274 4225

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Second CfP: International Conference on Test and Proofs (TAP 2012), Next Deadline: 2011-12-14
by Achim D. Brucker 16 Nov '11

16 Nov '11

(Apologies for duplicates) ************************************************* **** Less than one month until the deadline *** **** for submitting abstract to TAP 2012 *** ************************************************* CALL FOR PAPERS Full and short Research Paper, Industrial Expierence Papers, Tool Papers Abstract submission: Dec 14, 2011, Paper submission Dec 21, 2012 6th INTERNATIONAL CONFERENCE ON TEST AND PROOFS (TAP 2012) http://lifc.univ-fcomte.fr/tap2012/ May 31 - June 1, 2012, Prague, Czech Republic Part of the TOOLS Federated Conferences 2012 http://tools2012.fit.cvut.cz/ The TAP conference is devoted to the convergence of proofs and tests, to the application of techniques from both sides and their combination for the advancement of software quality. Test and Proof seem to be contradictory techniques: if you have proved your program to be correct, it is fruitless to comb it for bugs; and if you are testing it, that is surely a sign that you have given up on any hope to prove its correctness. Accordingly, proofs and tests have, since the onset of software engineering research, been pursued by distinct communities. However, the development of both approaches lead to the discovery of common issues and to the realization that each may need the other. The emergence of model checking has been one of the first signs that contradiction may yield to complementarity. Further evidence give test data generation techniques from models or programs which boil down to constraint resolution techniques for relatively large formula; the advent of powerful SMT solvers have therefore powered new testing techniques. Finally, since formal, proof-based verification is costly, testing invariants and background theories can be helpful to detect errors early and to improve cost effectivity. Summing up, in the past few years an increasing number of research efforts have encountered the need for combining proofs and tests, dropping earlier dogmatic views of incompatibility and taking instead the best of what each of these software engineering domains has to offer. The TAP conference aims to bring together researchers and practitioners working in the converging fields of testing and proving, and will offer a generous allocation of papers, panels and informal discussions. Topics of interest cover theory definitions, tool constructions and experimentations and include (other topics related to TAP are welcome): - Transfer of concepts from testing to proving (e.g., coverage criteria) and from proving to testing - Program proving with the aid of testing techniques - New problematics in automated reasoning emerging from specificities of test generation - Verification and testing techniques combining proofs and tests - Generation of test data, oracles, or preambles by deductive techniques such as: theorem proving, model checking, symbolic execution, constraint logic programming - Model-based testing and verification - Generation of specifications by deduction - Automatic bug finding - Debugging of programs combining static and dynamic analysis - Formal frameworks - Tool descriptions and experience reports - Case studies combining tests and proofs - Applying combination of test and proof techniques to new application domains such as validating security procotols or vulnerability detection of programs Important Dates: ================ Abstract submission: December 14, 2011 Paper submission: December 21, 2011 Notification: March 2, 2012 Camera ready version: March 19, 2012 TAP conference: May 31 - June 1, 2012 (to be confirmed) TOOLS conferences (TOOLS, ICMT, SC, TAP): May 29 - June 01, 2012 Conference Chairs: Bertrand Meyer Program Chairs: Achim D. Brucker and Jacques Julliand Program Committee (to be extended): =================================== Nazareno Aguirre, Bernhard K. Aichernig, Paul Ammann, Dirk Beyer, Nikolaj Bjorner, Robert Clarisó, Marco Comini, Catherine Dubois, Gordon Fraser, Angelo Gargantini, Alain Giorgetti, Patrice Godefroid, Martin Gogolla, Arnaud Gotlieb, Reiner Hähnle, Bart Jacobs, Thierry Jéron, Gregory Kapfhammer, Nikolai Kosmatov, Victor Kuliamin, Karl Meinke, Jeff Offutt, Holger Schlingloff, T.H. Tse, Margus Veanes, Luca Viganò, Burkhart Wolff, Fatiha Zaidi Submission: =========== Please submit your papers via http://lifc.univ-fcomte.fr/tap2012/. TAP 2012 will accept two types of papers: - Research papers: full papers with at most 16 pages in LNCS format (pdf), which have to be original, unpublished and not submitted elsewhere. - Short contributions: work in progress, (industrial) experience reports or tool demonstrations, position statements; an extended abstract with at most 6 pages in LNCS format (pdf) is expected. Accepted papers will be published in the Springer LNCS series and will be available at the conference. The contents of previous TAP proceedings is available at: http://www.informatik.uni-trier.de/~ley/db/conf/tap/ -- Dr. Achim D. Brucker, SAP Research, Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe Phone: +49 6227 7-52595, Fax: +49-6227 78-50502, http://www.brucker.ch

1 0

Build error with network/snap w/win7 haskell platform
by Adam Turoff 16 Nov '11

16 Nov '11

I'm trying to build snap-0.6 on win7/x64 with the current 64-bit haskell platform. I have the mingw compilers from the platform in $PATH, and I can get the network and snap-server modules to build. But snap-0.6 fails: [18 of 31] Compiling Snap.Snaplet.Internal.Types ( src\Snap\Snaplet\Internal\Types.hs, dist\build\Snap\Snaplet\Internal\Types.o ) Loading package ghc-prim ... linking ... done. ... Loading package murmur-hash-0.1.0.4 ... linking ... done. Loading package parsec-3.1.2 ... linking ... done. Loading package network-2.3.0.7 ... linking ... ghc.exe: unable to load package `network-2.3.0.7' ghc.exe: C:\Users\aturoff\AppData\Roaming\cabal\network-2.3.0.7\ghc-7.0.3\HSnetwork-2.3.0.7.o: unknown symbol `_acceptNewSock' cabal.exe: Error: some packages failed to install: snap-0.6.0.2 failed during the building phase. The exception was: ExitFailure 1 Any ideas? The platform comes with network-2.3.0.2, but cabal insists on upgrading it. Is there some way to force cabal to use the version that came with the platform instead? Specifying network==2.3.0.2 as a dependency just rebuilds it as a user package. Thanks, -- Adam

1 0

deepseq-1.2.0.1 missing Data.Map instance
by Henry Laxen 16 Nov '11

16 Nov '11

Dear Group, Today I tried to compile snap 0.6 with ghc 7.2, (using virthualenv, which is GREAT by the way) and got the following error somewhere along the way got a message about aeson-native requires deepseq-1.1.0.2 but I had deepseq-1.2.0.1 installed. So I unpacked aeson-native-0.3.3.1 in my virthualenv and changed the build-depends to just deepseq which caused: Configuring aeson-native-0.3.3.1... Preprocessing library aeson-native-0.3.3.1... Building aeson-native-0.3.3.1... [2 of 6] Compiling Data.Aeson.Types ( Data/Aeson/Types.hs, dist/build/Data/Aeson/Types.o ) Data/Aeson/Types.hs:196:22: No instance for (NFData Object) arising from a use of `rnf' Possible fix: add an instance declaration for (NFData Object) In the expression: rnf o In an equation for `rnf': rnf (Object o) = rnf o In the instance declaration for `NFData Value' cabal: Error: some packages failed to install: aeson-native-0.3.3.1 failed during the building phase. The exception was: ExitFailure 1 A little investigating and I discovered that instance (NFData k, NFData a) => NFData (Data.Map.Map k a) where rnf = rnf . Data.Map.toList is in deepseq-1.1.0.2 but not in deepseq-1.2.0.1. Adding it back got aeson-native-0.3.3.1 and later snap-0.6 to compile just fine. So I guess my question is: Is there a reason that the map instance was removed from deepseq-1.2.0.1, and can we please put it back in? Thanks. Best wishes, Henry Laxen

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1p function for NonEmpty
by Yitzchak Gale 15 Nov '11

15 Nov '11

Hi Edward, I started @telling you on #haskell, but it has become too long for that. :) The following functions would be nice additions to Data.List.NonEmpty in the semigroups package: replicate1p :: Whole n => n -> a -> NonEmpty a take1p :: Whole n => n -> NonEmpty a -> NonEmpty a splitAt1p :: Whole n => n -> NonEmpty a -> (NonEmpty a, [a]) Also, your warnings in the haddocks about blowing up on negative arguments don't seem to be needed for take, drop, and splitAt. We could avoid the problem with negative arguments for (!!) too by providing an alternative for Whole numbers. But in that case the function would still be partial, so I'm not sure if it's worth it. I wish there were some way to get Whole to default to Natural. Thanks, Yitz

1 1

[Announcement] New release of SBV (0.9.22)
by Levent Erkok 14 Nov '11

14 Nov '11

New release of SBV (0.9.22) is out: http://hackage.haskell.org/package/sbv Major changes in this release are: - Support for explicit quantification (including alternating existentials and universals) - Ability to use Microsoft's Z3 SMT solver (in addition to Yices). Full release notes: http://github.com/LeventErkok/sbv/blob/b75fb082c013ae9612ef09b90d5feeaec652… Thanks, -Levent.

1 0

Can't establish subprocess communication
by Poprádi Árpád 14 Nov '11

14 Nov '11

Hi all! I have found a simple program on the web: --code begin: copierer.hs module Main (main) where main = interact id --code end I compiled it with ghc -threaded --make copierer.hs If i start it from a terminal,it behaves like the "cat" program without arguments: simply copies the stdin to stdout line by line. I wanted it to use from another Haskell program as subprocess: --code begin: twowaysubprocesscomm.hs module Main where import System.IO import System.Process import Control.Concurrent main :: IO () main = do (hin,hout,p) <- start_subprocess send_and_receive (hin,hout) "boo" send_and_receive (hin,hout) "foo" terminateProcess p start_subprocess :: IO (Handle,Handle,ProcessHandle) start_subprocess = do -- (hin, hout, _, p) <- runInteractiveProcess "cat" [] Nothing Nothing -- This line works as expected (hin, hout, _, p) <- runInteractiveProcess "copierer" [] Nothing Nothing -- This line doesn't work hSetBuffering hin LineBuffering hSetBuffering hout LineBuffering return (hin, hout, p) send_and_receive :: (Handle,Handle) -> String -> IO () send_and_receive (hin,hout) indata = do forkIO $ hPutStrLn hin indata outdata <- hGetLine hout putStrLn $ "outdata: " ++ outdata --code end I compiled it with: ghc -threaded --make twowaysubprocesscomm.hs then ran: ./twowaysubprocesscomm twowaysubprocesscomm: fd:7: hGetLine: end of file twowaysubprocesscomm: fd:6: hPutChar: resource vanished (Broken pipe) Copierer doesn't work as subprocess! If i compile twowaysubprocesscomm.hs using the original "cat", it works as expected: ./twowaysubprocesscomm outdata: boo outdata: foo What is wrong here? The "copierer.hs", its usage in "twowaysubprocesscomm.hs" or both? I use GHC 6.12.3 on a 64 bit linux. Thanks, Árpád

3 3

ANN: Netwire 2.0.0
by Ertugrul Soeylemez 14 Nov '11

14 Nov '11

Hello everybody, it's finally done. I have just released Netwire 2.0.0, which is a complete rewrite from scratch. It has been generalized to arbitrary automata with inhibition, so FRP is now just a special use case. First of all the top module is now: import Control.Wire Wire is now an arrow transformer instead of an arrow-to-monad transformer and the inhibition type is polymorphic instead of the hard-coded SomeException type: Wire e (>~) a b Wire represents the following underlying type: a >~ (Either e b, Wire e (>~) a b) Inhibition uses any monoid 'e'. To get the old behaviour, you can use Last SomeException as 'e'. One significant change is that all features which were builtin in Netwire 1 are now addons, including even time and random number generation. These addons are available in the form of type classes (Control.Wire.Classes) for the underlying arrow, including for example: * ArrowIO, * ArrowRandom, * ArrowTime. Also there are no explicit sessions anymore. The current state of a wire is simply the wire itself. Everything else is captured by the underlying arrow (>~), which you can construct the way you like. There is no hard-coded WireState anymore. To get going really fast, just use the following type: type SimpleWire = Wire () (Kleisli IO) with the testWire function. You can find a small demo here: <http://hpaste.org/54025> There are instances for all addon classes for Kleisli IO, so you can write your first application very quickly. For more serious applications, you would usually write or compose your own underlying arrow or even leave it polymorphic. Please don't hesitate to give me feedback. Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/

2 3

Do type classes have a partial order?
by Patrick Browne 14 Nov '11

14 Nov '11

2 1

Re: [Haskell-cafe] German names for kinds and sorts
by John Lato 14 Nov '11

14 Nov '11

> From: Jerzy Karczmarczuk <jerzy.karczmarczuk(a)unicaen.fr> > > So, even more seriously, I propose to use more often Latin and Greek. Jerzy's arguments make a lot of sense to me, but why not use an index-based notation? T0 = Type T1 = Kind T2 = Sort etc. this seems easier to me than an arbitrary hierarchy, particularly as you go higher up the structure. John Lato

1 0

Identifying thunks from GHC heap profiles
by Tristan Ravitch 14 Nov '11

14 Nov '11

I am trying to debug a stack overflow that seems to be caused by a large chain of thunks being evaluated all at once. I have some profiles generated using +RTS -hd -RTS that show some promising candidates, but they have generated names like Module.sat_s9et, Module.sat_s9jk, etc Is there any convenient way to map these generated names back to something recognizable in the source? I tried using +RTS -hc -hdsat_s9et -RTS to filter SCCs as suggested in http://hackage.haskell.org/trac/ghc/ticket/1639, but the resulting profile is always empty. I also tried to use -fext-core and -ddump-simpl to dump some intermediate representations but none of the thunk names seem to appear in those outputs.

2 1

German names for kinds and sorts
by Robert Clausecker 14 Nov '11

14 Nov '11

Hi all! I want to write my Facharbeit (kind of an essay you have to write on a specific topic you can choose yourself for highschool graduation) about the type-system of Haskell. It is required in our school to write this document in German language. Most time, it is not really difficult to find an appropriate term for concepts of Haskell, like types (Typen) or type classes (Typklassen). But I really don't know how to call kinds and sorts in German. Any ideas? Yours, Robert Clausecker

10 10

ANNOUNCE: iteratee-compress 0.3.0.0
by Maciej Marcin Piechotka 14 Nov '11

14 Nov '11

Iteratee-compress provides compressing and decompressing enumerators including flushing (using John Lato's implementation). Currently only gzip and bzip is provided but LZMA is planned. Changes from previous version: - Move API from enumerator to enumeratee Next goals: - LZMA support - Generic interface for flushing To think about: - Should inner iteratee be able to request flushing Regards

1 0

Getting started on Mac OSX
by hstenstrom 12 Nov '11

12 Nov '11

I have a book on Haskell, and I've downloaded and installed Haskell Platform for Mac OS X. What do I do now? XCode is a requirement, and I have it, but I don't know how to run it. To begin with, I want to test small examples from the book, using ghc or ghci. I have read file:///Library/Haskell/doc/start.html. - Where is the software I've just installed? - How is ghci started? Or the "platform", whatever that is? Many thanks if you can help me! Helge -- View this message in context: http://haskell.1045720.n5.nabble.com/Getting-started-on-Mac-OSX-tp4983597p4… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 4

Strange GC timings
by Artyom Kazak 12 Nov '11

12 Nov '11

Hello! The following program executes 1.5 seconds on my computer: -----------------------CODE BEGIN------------------------- module Main where import Data.Array.IArray main = print (answers ! 1000000) nextAns :: (Int, Int, Float) -> (Int, Int, Float) nextAns (a, n, r) = if r2 > 1 then (a+1, n+2, r2) else (a+1, n+3, r3) where a' = fromIntegral a n' = fromIntegral n r2 = r * (a'/(a'+1))**n' * (n'+1)*(n'+2)/(a'+1)^2 r3 = r2 * (n'+3) / (a'+1) answers :: Array Int Int answers = listArray (1, 1000000) (map snd3 $ iterate nextAns (1, 2, 2)) where snd3 (a, b, c) = b ------------------------CODE END-------------------------- From these 1.5 seconds, 1 second is spent on doing GC. If I run it with "-A200M", it executes for only 0.5 seconds (total). Which is more interesting, when I use UArray instead of Array, it spends only 0.02 seconds in GC, but total running time is still 1.5 seconds. Why are... these things?

2 1

Label macro expansion bug In HList.
by aditya siram 12 Nov '11

12 Nov '11

Hi all, I am exploring OOHaskell and ran into some compilation issues with some of the samples. I hope this is the right place to report it. For example "OCamlTutorial.hs" generates the following error: ../samples/OCamlTutorial.hs:98:3: Multiple declarations of `foo' Declared at: ../samples/OCamlTutorial.hs:54:1 ../samples/OCamlTutorial.hs:98:3 Failed, modules loaded: OOHaskell, Dynamic, Print, DeepNarrow, Nominal, New. This is happening because the "label" macro on line 98: $(label "varX") doesn't expand correctly and clashes with the "foo" function on line 54: foo f = f # field1 The "label" function is found in the Data.HList.MakeLabels module and should work this way according to the docs: > runQ (label "test") >>= putStrLn . pprint data Test deriving (Data.Typeable.Internal.Typeable) test = Data.HList.FakePrelude.proxy :: Data.HList.FakePrelude.Proxy Test But I get: data Foo_0 deriving (Data.Typeable.Internal.Typeable) foo_1 = Data.HList.FakePrelude.proxy :: Data.HList.FakePrelude.Proxy Foo_0 This still doesn't cleanly explain why "OCamlTutorial.hs" is failing since it seems to be generating unique datatypes and functions by suffixing them with a number, but it seems to point to the problem. I'm hoping someone who knows HList better might understand it better. Thanks, -deech

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Data.Vector.Unboxed
by kaffeepause73 11 Nov '11

11 Nov '11

Hello, quick question about unboxed Vectors : Is it possible to create an unboxed vector of unboxed vector ? : > import qualified Data.Vector.Unboxed as V > type UnboxedNestedVextor = V.Vector (V.Vector Int) Alternatively I would have to use: > import qualified Data.Vector.Unboxed as V > import qualified Data.Vector as VB type UnboxedNestedVextor = VB.Vector (V.Vector Int) Is there a rule of thumb how much quicker Unboxed Vectors are ? Cheers Phil -- View this message in context: http://haskell.1045720.n5.nabble.com/Data-Vector-Unboxed-tp4977289p4977289.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Usage question with TemplateHaskell and Generic
by Magicloud Magiclouds 11 Nov '11

11 Nov '11

Hi, I'd like to simpler the work of deriving MyClass. And I have two ways to do: TemplateHaskell "$(derivingMyClass)", or Generic "deriving (MyClass)". Since I need to get the type name in the deriving, then I met this question: If I have "data A b = C b", then with TemplateHaskell, the type would be "VarT b", which means at compile time, I cannot get the exact type, so the type name would be "b". So I wonder if this could be resolved by TemplateHaskell, or Generic is the only choice. PS: I have not tried to do this in Generic. -- 竹密岂妨流水过山高哪阻野云飞

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Re: [Haskell-cafe] Ridiculously slow FFI, or cairo binding?
by Eugene Kirpichov 11 Nov '11

11 Nov '11

Hi, The actual thanks for tracking this down go to Vincent Hanquez for finding that we're doing a lot of gmp calls (and for making me aware of ltrace), and to Felipe Lessa for finding that this is caused by poor code generated for cFloatConv :) Your changes look identical to those that I made in my copy. On Thu, Nov 3, 2011 at 11:41 AM, Axel Simon <Axel.Simon(a)in.tum.de> wrote: > Hi Eugene, > > > On 02.11.2011, at 17:34, Eugene Kirpichov wrote: > > Heh. >> >> Guess what! >> A simple {-# INLINE cFloatConv #-} helped to the same extent! >> >> Axel, I think this change should be pretty easy to incorporate, and it >> probably makes sense to inline all other functions in Types.chs too. >> >> > I've added INLINE pragmas to all these odd c2hs marshalling functions. > Could you pull and check if I've done it correctly? > > Thanks for tracking this down! > > Axel > > > Would you like me to send the trivial darcs patch or the gtk2hs team >> will take care of this? >> >> On Wed, Nov 2, 2011 at 7:29 PM, Felipe Almeida Lessa >> <felipe.lessa(a)gmail.com> wrote: >> >>> On Wed, Nov 2, 2011 at 11:24 AM, Jean-Marie Gaillourdet >>> <jmg(a)gaillourdet.net> wrote: >>> >>>> Hi Eugene, >>>> >>>> did you try using the SPECIALIZE pragma? It is part of the Haskell 98 >>>> and Haskell 2010 specifications. >>>> >>> >>> I don't think it's going to make any difference, as the core already >>> have an specialized poor version. See my first e-mail. >>> >>> -- >>> Felipe. >>> >>> >> >> >> -- >> Eugene Kirpichov >> Principal Engineer, Mirantis Inc. http://www.mirantis.com/ >> Editor, http://fprog.ru/ >> > > -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

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How can I get rid of this link error?
by Amy de Buitléir 11 Nov '11

11 Nov '11

I wrote a library called AmysGeometry. The only modules in it (so far) are: Amy/Geometry/ThreeD.hs Amy/Geometry/UnitSphere.hs The library compiles just fine, and I've been using it with other programs for a while. Then yesterday, I started getting the following error. Linking dist/build/add-centroids/add-centroids ... /usr/local/lib/AmysGeometry-1.0/ghc-7.0.3/libHSAmysGeometry-1.0.a(UnitSphere.o): In function `s3c6_info': (.text+0x4557): undefined reference to `__stginit_AmysGeometryzm1zi0_AmyziGeometry_' /usr/local/lib/AmysGeometry-1.0/ghc-7.0.3/libHSAmysGeometry-1.0.a(UnitSphere.o): (.data+0x3f0): undefined reference to `AmysGeometryzm1zi0_AmyziGeometry_DZCLocation_static_info' collect2: ld returned 1 exit status cabal: Error: some packages failed to install: I think this started because I recompiled some stuff with profiling. So I wiped out my current GHC and Haskell installation, re-installed it, and rebuilt AmysGeometry. But I'm still getting this error when I try to link with it. I would be grateful for any advice on how to diagnose this and fix it. Oh, and "ghc-pkg check" doesn't report any errors.

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Consuming anyToken with parsing with derivatives (derp) library in Hackage?
by Ahn, Ki Yung 11 Nov '11

11 Nov '11

I was playing with derp recently, and many of the Char and Combinator of Parsec seem to be easily definable from derp. However, I haven't yet figured out a natural way to define anyToken or satisfy combiator of Parsec using derp. There is a way of course, to list all the unicode characters and combine them with <|>, which is extremely inefficient, even if you limit yourself that satisfy combinator be compile time template haskell function, it still seems a bit silly. For things like space, it seems reasonable to list all take the sum of them, since there are handful of them. But things like consume anything that is not a space ought to be defined as a complement or negation of the space parser. In general CFG is not closed under negation, but most of the time what we want to take a negation is really for regular fragment of the language, like consuming anything that is not a linebreak to lex/parse one line comments. In Matt's Standford talk, he mentioned some vision about going beyond CFG and he mentioned negation, but in the library implementation I didn't find that. Is it already possible with some trick? Is there a standard way to define such combinators with derp? Or, is it the case that there a way to do it in the scheme library but not implemented in Haskell derp package? I read through the scheme implementation too but there didn't seem to be a combinator for tacking negations either. Ki Yung Ahn

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graphviz: dotizeGraph and graphToGraph not adding positions
by Max Rabkin 11 Nov '11

11 Nov '11

My understanding of the documentation for Data.GraphViz.dotizeGraph and graphToGraph is that they should add position attributes to a graph. But they always seem to return graphs with empty attribute lists. What am I doing wrong in the following tiny example? > dotizeGraph nonClusteredParams (insNode (0, "Blah") $ empty :: Gr String ()) 0:([],"Blah")->[] I expected the first list to contain at least a Pos attribute. I have written a wrapper around /usr/share/dot which shows the program is outputting positional information. --Max

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Easiest to use NoSQL storage with Haskell?
by dokondr 10 Nov '11

10 Nov '11

Hi, What Haskell package to work with NoSQL storage is both mature and easiest to use? I need persistent storage for simple key/value lists (not complex JSON docs). CouchDB and Cassandra seems to be overkill for my needs. What about Riak, MongoDB, Voldemort, etc. ? Thanks! Dmitri.

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timezone-series, timezone-olson dependencies
by Ben Gamari 10 Nov '11

10 Nov '11

Is there a reason why the current version of the timezone-series and timezone-olson packages depend on time<1.3? With time 1.4 being widely used at this point this will cause conflicts with many packages yet my tests show that both packages work fine with time 1.4. Could we have this upper bound bumped to 1.5? Cheers, - Ben

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Re: [Haskell-cafe] [ANN] transformers-base, transformers-abort, monad-abort-fd
by Bas van Dijk 10 Nov '11

10 Nov '11

What about "base" instead of "b"? I don't think we should change "m" since that name is used to denote a monad in almost any Haskell library I know. On 10 November 2011 19:07, Colin Adams <colinpauladams(a)gmail.com> wrote: > And quite rightly too. > > On 10 November 2011 18:02, Felipe Almeida Lessa <felipe.lessa(a)gmail.com> > wrote: >> >> On Thu, Nov 10, 2011 at 2:54 PM, Bas van Dijk <v.dijk.bas(a)gmail.com> >> wrote: >> > * Use descriptive variable names: 'm' for monad, 'b' for base monad >> >> It's funny how we, haskellers, find 'm' and 'b' descriptive names. I >> know many programmers who would cry after seeing this =). >> >> Cheers, >> >> -- >> Felipe. >> >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe > >

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