- Haskell-Cafe - Haskell.org

Much faster complex monad stack based on CPS state
by Nicu Ionita 28 Sep '11

28 Sep '11

Hello list, Starting from this emails (http://web.archiveorange.com/archive/v/nDNOvSM4JT3GJRSjOm9P) I could refactor my code (a UCI chess engine, with complex functions, in which the search has a complex monad stack) to run twice as fast as with even some hand unroled state transformer! So from 23-24 kilo nodes per second it does now 45 to 50 kNps! And it looks like there is still some improvement room (I have to play a little bit with strictness annotations and so on). (Previously I tried specializations, then I removed a lot of polimorphism, but nothing helped, it was like hitting a wall.) Even more amazingly is that I could program it although I cannot really understand the Cont & ContT, but just taking the code example from Ryan Ingram (newtype ContState r s a = ...) and looking a bit at the code from ContT (from the transformers library), and after fixing some compilation errors, it worked and was so fast. I wonder why the transformers library does not use this kind of state monad definition. Or does it, and what I got is just because of the unrolling? Are there monad (transformers) libraries which are faster? I saw the library kan-extensions but I did not understand (yet) how to use it. Nicu

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network package Windows co-maintainer/buildbot needed (Was: network 2.3.05 on windows 7 with ghc-7.2.1)
by Johan Tibell 28 Sep '11

28 Sep '11

Let me take this opportunity to ask for a co-maintainer that can help me keep the network package working on Windows. I don't have easy access to a Windows machine (or even VM) anymore so testing on Windows is hard. What I'd really like is a buildbot that builds the following Jenkins job as a "slave" node: http://ci.johantibell.com/job/network/ config.xml: <?xml version='1.0' encoding='UTF-8'?> <matrix-project> <actions/> <description></description> <keepDependencies>false</keepDependencies> <properties/> <scm class="hudson.plugins.git.GitSCM"> <configVersion>2</configVersion> <userRemoteConfigs> <hudson.plugins.git.UserRemoteConfig> <name>origin</name> <refspec>+refs/heads/*:refs/remotes/origin/*</refspec> <url>https://github.com/haskell/network.git</url> </hudson.plugins.git.UserRemoteConfig> </userRemoteConfigs> <branches> <hudson.plugins.git.BranchSpec> <name>stable</name> </hudson.plugins.git.BranchSpec> </branches> <recursiveSubmodules>false</recursiveSubmodules> <doGenerateSubmoduleConfigurations>false</doGenerateSubmoduleConfigurations> <authorOrCommitter>false</authorOrCommitter> <clean>false</clean> <wipeOutWorkspace>false</wipeOutWorkspace> <pruneBranches>false</pruneBranches> <remotePoll>false</remotePoll> <buildChooser class="hudson.plugins.git.util.DefaultBuildChooser"/> <gitTool>Default</gitTool> <browser class="hudson.plugins.git.browser.GithubWeb"> <url>https://github.com/haskell/network/</url> </browser> <submoduleCfg class="list"/> <relativeTargetDir></relativeTargetDir> <excludedRegions></excludedRegions> <excludedUsers></excludedUsers> <gitConfigName></gitConfigName> <gitConfigEmail></gitConfigEmail> <skipTag>false</skipTag> <scmName></scmName> </scm> <canRoam>true</canRoam> <disabled>false</disabled> <blockBuildWhenDownstreamBuilding>false</blockBuildWhenDownstreamBuilding> <blockBuildWhenUpstreamBuilding>false</blockBuildWhenUpstreamBuilding> <triggers class="vector"> <hudson.triggers.SCMTrigger> <spec>*/5 * * * *</spec> </hudson.triggers.SCMTrigger> </triggers> <concurrentBuild>false</concurrentBuild> <axes> <hudson.matrix.TextAxis> <name>compiler</name> <values> <string>ghc-6.10.4</string> <string>ghc-6.12.3</string> <string>ghc-7.0.3</string> </values> </hudson.matrix.TextAxis> </axes> <builders> <hudson.tasks.Shell> <command>cabal install -w $compiler --only-dependencies --enable-tests cabal clean autoreconf cabal configure -w $compiler --enable-tests cabal build cabal test cabal sdist</command> </hudson.tasks.Shell> </builders> <publishers> <hudson.tasks.Mailer> <recipients>johan.tibell(a)gmail.com</recipients> <dontNotifyEveryUnstableBuild>false</dontNotifyEveryUnstableBuild> <sendToIndividuals>false</sendToIndividuals> </hudson.tasks.Mailer> </publishers> <buildWrappers/> <runSequentially>false</runSequentially> </matrix-project>

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Binding a socket to all interfaces
by Michael Snoyman 28 Sep '11

28 Sep '11

Hi, One of the recurring issues that comes up in Warp is binding to IPv4 versus IPv6 hosts. Our current code is available at [1]. It was updated to look like that in this commit [2] in order to support both IPv4 and IPv6 hosts by default. However, now it seems than on Debian and FreeBSD, it *only* responds to IPv6 by default[3][4]. I'm frankly stumped at this point on how to have our cake and eat it too. Does anyone have an idea of the correct incantation to get Warp to do the Right Thing(tm) here? And if not, is there any advice on sensible default behavior? I'm considering allowing a few special host values: * "*" (default, what we have now): Make this bind to IPv4 * "ipv4": Again, bind to IPv4. Guaranteed not to change in the future * "ipv6": Bind to IPv6. Michael [1] https://github.com/yesodweb/wai/blob/master/warp/Network/Wai/Handler/Warp.h… [2] https://github.com/snoyberg/warp/commit/02c1396c86e3fceb48cbe7df58cb631c804… [3] https://github.com/snoyberg/warp/issues/9 [4] http://stackoverflow.com/questions/7486257/yesod-devel-server-only-listenin…

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Parsing binary data question
by Michael Oswald 28 Sep '11

28 Sep '11

Hello all, I am currently working on parser for some packets received via the network. The data structure currently is like that: data Value = ValUInt8 Int8 | ValUInt16 Int16 | ValUInt32 Int32 -- more datatypes data Parameter = Parameter { paramName :: String, paramValue :: Value } | ParameterN { paramName :: String, paramValue :: Value }deriving (Show) data TCPacket = TCPacket { tcAPID :: Word16, tcType :: Word8, tcSubType :: Word8, tcParameters :: [Parameter] } The output should a parsed packet (I am using cereal for this). The packet structure can vary depending on the type and the configuration, so I have a function which takes a TCPacket as "input template" which has already the correct list of parameters which are then parsed: parseTCPacket :: Word16 -> Word8 -> Word8 -> ByteString -> TCPacket -> TCPacket parseTCPacket apid t st pktData tmplate = TCPacket apid t st params where tmplParams = (tcParameters tmplate) params = zipWith (\p v -> p {paramValue = v} ) tmplParams values' values = map paramValue tmplParams values' = binValues values (pktData pusPkt) getBinGet :: Value -> Get Value getBinGet (ValInt8 _) = getWord8 >>= \x -> return $ ValInt8 $ fromIntegral x getBinGet (ValInt16 _) = getWord16be >>= \x -> return $ ValInt16 $ fromIntegral x -- many more datatypes getBinValues :: [Value] -> Get [Value] getBinValues inp = mapM getBinGet inp binValues :: [Value] -> ByteString -> ([Value], B.ByteString) binValues inp bytes = case runGet (getBinValues inp) bytes of Left err -> throw $ DecodeError ("binValues: " ++ err) Right x -> x This works quite well and does what I want. Now I have the problem that there are some parameters, which could be so-called "group repeaters" (the ParameterN constructor above). This means, that if such a parameter N is encountered during parsing (it has to be an int type), all following parameters are repeated N times with possible nesting. So for example if the template (where the values are all 0) is like this: [Parameter "Param1" (ValUInt32 0), ParameterN "N1" (ValUInt8 0), Parameter "Param2" (ValUint16 0), ParameterN "N2" (ValUint8 0), Parameter "Param3" (ValUint8 0)] Which means there is a group for the last 3 parameters which is repeated N1 times which contains another group which is repeated N2 times. If binary data based on the template above would be like this (datatypes omitted): 10, 2, 439, 2, 12, 13, 65535, 2, 22, 23 then a valid packet after parsing would be: [Parameter "Param1" (ValUint32 10), ParameterN "N1" (ValUint8 2), Parameter "Param2" (ValUint16 439), ParameterN "N2" (ValUint8 2), Parameter "Param3" (ValUint8 12), Parameter "Param3" (ValUint8 13), Parameter "Param2" (ValUint16 65535), ParameterN "N2" (ValUint8 2), Parameter "Param3" (ValUint8 22), Parameter "Param3" (ValUint8 23)] Now I am a bit lost on how to implement such a parser. It would be much easier if the structure would be already encoded in the binary data, but I have to stick to this template approach. I have some C++ parser which does this but of course it's very imperative and a little bit quirky implemented, so if anybody has an idea on how to proceed (cereal, attoparsec whatever), please tell me. lg, Michael

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I for one welcome our new Robotic Overlords
by Jeremy Shaw 28 Sep '11

28 Sep '11

When the robots take over, do you want them to be developed using a sane language like Haskell or Agda? Or some dangerous untyped OO language? I think the answer is obvious. The question is, "How?". The robots will not be developed by us, but by the children of today. So, we must reach their pure minds before they have been unsafely coerced by the evil unbelievers who do not worship the gods λ, Π, and ω. My long term vision is: A company which produces an extensible robotics platform for children and adults ages 8 and up. The platform would be very open, extensible, and hackable. The robotic programming languages would be based around concepts like functional reactive programming, dependent types, etc. Children would begin with a simple FRP language to control the robot. They would solve simple problems like "go forward until an object is encountered." As the young masters grow, they can tackle more difficult problems such as maze solving. Even later they can delve into more advanced subjects like computer vision, speech recognition and synthesis, or mind control rays. The short term vision can be summarized in one word "leverage". We need to find an existing robotic platform which can be easily targeted somehow using Haskell or Agda. Perhaps something that can be targeted using atom or lava? Maybe something Arduino based? I have created a wiki page here to record your suggestions and ideas: http://haskell.org/haskellwiki/RoboticOverlords The requirements now are something that is: - hackable/open - easily obtained - reasonable in price - can easily be targeted via Haskell The only candidate I know of so far is lego mindstorms via the NXT package on hackage, Though some could argue that lego mindstorms are not reasonably priced. http://hackage.haskell.org/package/NXT Let's here your ideas! - jeremy

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Fwd: [Haskell] getting started
by Ivan Lazar Miljenovic 28 Sep '11

28 Sep '11

It helps if I actually CC the right mailing list... ---------- Forwarded message ---------- From: Ivan Lazar Miljenovic <ivan.miljenovic(a)gmail.com> Date: 28 September 2011 20:02 Subject: Re: [Haskell] getting started To: haskell <shubhammaheshwariy(a)gmail.com> Cc: cafe(a)haskell.org On 28 September 2011 19:56, haskell <shubhammaheshwariy(a)gmail.com> wrote: > i am new to haskell can you tell me the softwares to install in haskell > i have install hugs emacs > but when i write any code it gives same error can you help me start i have > lekash too i have installed some more packages Sending this over to the haskell-cafe(a)haskell.org mailing list (as that is where discussions take place, haskell(a)haskell.org is for announcements). You may wish to try the beginners mailing list however: http://www.haskell.org/mailman/listinfo/beginners If you want help, try providing the errors. However, I would recommend that you install the Haskell Platform instead of Hugs: http://hackage.haskell.org/platform/ -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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[ANN] crypto-api-tests
by Thomas DuBuisson 28 Sep '11

28 Sep '11

The crypto-api test modules have been split out into their own package, crypto-api-tests. Additionally, the tests now use the test-framework package. This should make it much easier for hash/cipher maintainers to integrate into their existing testing infrastructure. For example: $ cabal update ; cabal install cryptocipher crypto-api crypto-api-tests {- BEGIN CODE -} import Test.Framework import Test.AES (makeAESTests) import Crypto.Cipher.AES (AES128) main = do ts <- makeAESTests (a :: AES128) defaultMain ts {- END CODE -} $ ghc test.hs ; ./test ... snip ... OFBVarTxt128d.txt-125: [OK] OFBVarTxt128d.txt-126: [OK] OFBVarTxt128d.txt-127: [OK] Block Cipher tests (ident): ECBEncDecID: [OK, passed 100 tests] CBCEncDecID: [OK, passed 100 tests] CFBEncDecID: [OK, passed 100 tests] OFBEncDecID: [OK, passed 100 tests] CTREncDecID: [OK, passed 100 tests] Block Cipher tests (lazy/string bytestring equality): ECBStringLazyEq: [OK, passed 100 tests] CBCStrictLazyEq: [OK, passed 100 tests] CFBStrictLazyEq: [OK, passed 100 tests] OFBStrictLazyEq: [OK, passed 100 tests] CTRStrictLazyEq: [OK, passed 100 tests] Properties Test Cases Total Passed 10 2272 2282 Failed 0 0 0 Total 10 2272 2282 Patches for more algorithms and/or property tests for classes of algorithms are certainly welcome. Cheers, Thomas

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emacs literate haskell mode
by Mathijs Kwik 28 Sep '11

28 Sep '11

Hi all, I'm using haskell-mode for emacs and I'm using it to open a literate haskell file which uses latex. This works fine, haskell code has syntax highlighting, and special symbols like lambda get used. However, the latex itself is dull and gree, no highlighting/coloring there. Does anyone know if it's possible to turn on latex highlighting in literate haskell mode? I tried switching to latex-mode, which does the trick (but it chokes on the haskell code inbetween), so I'm pretty sure emacs has everything it needs, but haskell-mode needs to enable this somehow. Any help would be great. Greetings, Mathijs

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Re: [Haskell-cafe] mapM is supralinear?
by John Lato 27 Sep '11

27 Sep '11

> From: Daniel Fischer <daniel.is.fischer(a)googlemail.com> > > On Friday 09 September 2011, 00:41:11, Roman Cheplyaka wrote: >> * Ertugrul Soeylemez <es(a)ertes.de> [2011-09-07 16:20:03+0200] >> >> > In general it's a bad idea to use mapM over IO. >> >> Could you explain why? > > Take it with a grain of salt, there's nothing necessarily wrong with using > mapM over IO on short lists. Agreed. Whenever I'd like to use mapM (or any other function for which a *M_ is available), I've found the following rules helpful: 1. If I can guarantee the list is short (~ n<=20), go ahead and use mapM 2. Otherwise use mapM_, foldM_, or foldM if a real reduction is possible (i.e. not "foldM snocM []"). Step 2 sometimes requires changing my design, but it's always been for the better. `mapM_` tends to require more pipeline composition, so it's leveraging the language's strengths. This has served me well, especially in IO, but in other monads as well. John L.

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9th Ghent Functional Programming Group meeting on Tuesday, the 4th of October, 2011
by Jasper Van der Jeugt 27 Sep '11

27 Sep '11

Hello all, We are glad to invite you to our 9th GhentFPG [1] meeting, which takes place on Thursday, the 4th of October, 2011 at 19:30 in the Technicum building of Ghent University. You do not have to be a Functional Programming guru to attend, everyone eager to learn is welcome. As before, the electronic sliding doors will be locked, but a phone number that you can call to get in will be provided at the doors on the far left of the building. The program is as follows: First, we will have a talk by Jurriën Stutterheim, from Utrecht: Snap Framework [2] is a relatively young, but very promising and already quite popular Haskell web framework. Its upcoming 0.6 release has seen a major redesign in the way you write (reusable) components for the framework using so-called snaplets. In this talk, we will look at how you can write snaplets and how you can put them together to create modular web applications. Then, we will have a number of lightning talks in which the following projects are presented: - hCole-server [3], a web interface to a framework for compiler optimizations (Andy Georges); - GA [4], a library to write genetic algorithms in Haskell (Kenneth Hoste); - websockets [5], a Haskell library for writing WebSocket-capable servers (Jasper Van der Jeugt). If you would also like to give a lightning talk (15 mins), please contact us and we will add you to this list. Afterwards, we will have some drinks at a local bar. [1]: http://www.haskell.org/haskellwiki/Ghent_Functional_Programming_Group [2]: http://snapframework.com/ [3]: http://github.com/itkovian/hcole-server [4]: http://github.com/boegel/GA [5]: http://github.com/jaspervdj/websockets Hoping to see you there, The GhentFPG organizing commitee

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