March 2014 - Haskell-Cafe

Re: [Haskell-cafe] [ANN] network-transport-zeromq-0.1.
by Alexander V Vershilov 31 Mar '14

31 Mar '14

Hi, On 31 March 2014 15:41, Mathieu Boespflug <m(a)tweag.io> wrote: > Hi Edsko, > > no worries. > >> Have you tried running Cloud Haskell on top of 0MQ, or are >> you using Network.Transport for something else? > > We're at a point where all distributed-process-tests pass, not just > network-transport-tests (Alexander can confirm). I need to add a correction, some tests, that implies connection break doesn't work, i.e. they are locking (but very rarely they are passing), and I didn't found a valid reason for it. I will try to prepare a email with description of this problem and everything I've found out in a next few days. -- Alexander

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[ANN] cake3-0.4.0.0 released
by Sergey Mironov 30 Mar '14

30 Mar '14

Hi! I'm glad to announce a new version of cake3 the Makefile generator. http://hackage.haskell.org/package/cake3 https://github.com/grwlf/cake3 Cake3 is a EDSL for building Makefiles, written in Haskell. With cake3, developer can write their build logic in Haskell, obtain clean and safe Makefile and distribute it among the non-Haskell-aware users. Currenly, GNU Make is the only backend supported. === Chagnes === - Automatically generate the 'clean' rule - New genFile and genTmpFile functions embed text files into the Makefile. - The Ur/Web extension improved === The sample program === module Cakefile where import Development.Cake3 import Cakefile_P main = writeMake (file "Makefile") $ do selfUpdate cs <- return $ [file "main.c", file "second.c"] d <- rule $ do shell [cmd|gcc -M $cs -MF @(file "depend.mk")|] os <- forM cs $ \c -> do rule $ do shell [cmd| gcc -c $(extvar "CFLAGS") -o @(c.="o") $c |] elf <- rule $ do shell [cmd| gcc -o @(file "main.elf") $os |] rule $ do phony "all" depend elf includeMakefile d Regards, Sergey

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TLS Handshake fails with 'invalid header type: 1\nFrom:\theader\n\n"'
by Reto Hablützel 30 Mar '14

30 Mar '14

Hello, I'm trying to a establish a TLS connection with the hs-tls library. I got most of the code from the Stunnel.hs, but what I am trying do here is to be able to pass either 'Client' or 'Server' as argument and then, depending on which one it is, act as either one in the handshake. This is the code, that tries to make the handshake: client :: Socket -> IO () client sock = do addr <- sockaddr _ <- connect sock addr ctx <- myCCtx sock contextHookSetLogging ctx logging handshake ctx server :: Socket -> IO () server sock = do sockaddr >>= bind sock listen sock 1 (peer, _) <- accept sock ctx <- mySCtx peer contextHookSetLogging ctx logging handshake ctx The rest of it would probably too much to fit into an email, so I am linking it from here: http://lpaste.net/102014 When I run it, the client fails to parse the handshake: Error_Packet_Parsing "Failed reading: invalid header type: 1\nFrom:\theader\n\n" Whereas the server says 'server hello done' right before it receives the alert from the client. How can this happen? That 'From:\theader...' doesn't even exist as a string in the hs-tls library.. Is there anywhere an example for the hs-tls library with a client as well as a server? Thanks a lot! - Reto

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Parsec Preprocessor
by Alessio Valentini 29 Mar '14

29 Mar '14

Dear Haskellers This is gonna be my first post on here : ) . I am developing some tools to interact with Chemistry packages, and I basically have to write input files for those programs. I would like to be able to write those input in a better way inside the hs code. For example this would be perfect ( {{{+ and +}}} are just labels to mark the "special syntax"): --------------a.hs-------------------------------- main = do writeFile "inputOfChemPack" string string = {{{+ This is the actual input file Formatted like this with some %variable +}}} variable = "foo" -------------------------------------------------- I have written a parser that is reading the code and outputs a file like this (it can handle special characters and variables that are not strings, but let's keep it simple here): ----------------b.hs------------------------------ main = do writeFile "inputOfChemPack" string string = "This is the actual input file\nFormatted like this\nwith some " ++ variable ++ " " variable = "foo" -------------------------------------------------- Now... this file can be compiled and it does exactly what I want: it prints a file like this: --------inputOfChemPack----- This is the actual input file Formatted like this with some foo -------------------------------------- Now the big question... right now I am doing this with some bash scripts (run the parser on the file and then compile its output)... but... is it possible to automatize this using my parser as a sort of preprocessor? the "dream" would be to make an extension that just applies the parser automatically before compilation, such as: -----------------a.hs----------------------------- {-# extensionName #-} main = do writeFile "inputOfChemPack" string string = {{{+ This is the actual input file Formatted like this with some %variable +}}} variable = "foo" -------------------------------------------------- $ ghci a.hs GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( a.hs, interpreted ) Ok, modules loaded: Main. *Main> string "This is the actual input file\nFormatted like this\nwith some foo" I have been browsing stuffs about quasiquotation and preprocessors, but I have the feeling that is a quite simple task compared to those solutions. Any ideas? How can I solve this problem? Thank you Alessio

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Naming/Bikeshedding: Haskell version of Capybara
by Charles Strahan 28 Mar '14

28 Mar '14

A question for you all: what would be a good name for a Haskell version of Ruby's Capybara web testing framework? I'm about to start hacking on some better web testing tools for Haskell, but I'm afraid I'm terrible at coming up with concise, revealing names for things. Any suggestions would be very welcome! -Charles

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Best Actor system?
by james 28 Mar '14

28 Mar '14

Having been introduced to actors by looking at Erlang, I discovered Akka. It seems that the performance is pretty impressive and I like the model. There seem to be several basic Actor libraries in Hackage, but they don't seem to be very actively developed. I'm more interested in the model for programming within a single runtime than I am for distributed systems, but message and dispatch performance definitely is important. Can anyone share experiences with the different packages? Is any one of them stand-out? Thanks James

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Happstack website down?
by Sgeo 28 Mar '14

28 Mar '14

http://www.happstack.com/ is now giving a default-looking "It works!" page. Anyone know why?

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Help getting hcwiid to work
by Ivan Perez 28 Mar '14

28 Mar '14

Hi Café, I'm trying to get the wiimote bindings to work (hcwiid). I can compile them just fine, but trying to open the wiimote with the demo application included in the repo returns a null. I tried using C apps directly (wmgui, etc.) and they work for me. I googled as much as I could, but found no solution there. I tried using previous versions of the package, going back in the history of the repo, but it seems to be "just broken". The maintainer of this package cannot offer any help at this moment. Has any haskeller been able to make this work? Best Ivan

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Haskell article from a friend ... .
by Vasili I. Galchin 28 Mar '14

28 Mar '14

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[ANN] network-transport-zeromq-0.1.
by Alexander V Vershilov 28 Mar '14

28 Mar '14

Hi, I'm happy to announce a new network-transport backend based on the 0MQ brokerless protocol [1]. This implementation makes it possible to the wealth of ZeroMQ transports through a simple and shared API. In particular, ZeroMQ supports authenticated communication channels, encryption, efficient multicast and throughput enhancement techniques such as message batching. Wrapping a subset of the ZeroMQ API behind the network-transport API makes it possible for a wealth of higher-level libraries such as distributed-process and HdpH to communicate over ZeroMQ seamlessly, with little to no modification necessary. Network transport zeromq provides: * basic network transport API, ability to use channels and send messages over reliable connections between endpoints. * multicasting. Multicasting reliable and ordered in absence of a long network failures, i.e. if message A is send before message B, then message A will be delivered before message B to every subscriber in multicast group. * basic plain text authorization. * 0mq driven reliability. (automatic connection restart without message loose). * ability mark connections as broken, this may be required to stop automatic reconnect. We currently have a few performance issues that cause a consistent 30% slowdown in performance of network-transport-zmq over TCP, but we’re working on it. ZeroMQ should in fact *improve* performance over raw TCP in many use cases thanks to intelligent batching of queued messages. Current approach is an early release of the library in order to gather feedback. There is a large TODO list with a set of features that may be useful for a big set of use cases like different authorization mechanisms including certificate based, support of connection encryption, support for unreliable connections, heartbeating and service discovery support. This features will be implemented in short milestones. While we believe network-transport-zmq to be useful in its own right, it is only a stepping stone towards making the rich communication patterns implemented in ZeroMQ available through distributed-process. This will allow for writing ZeroMQ applications with all the power of the Process monad, supervision hierarchies, powerful type based matching abstractions and intuitive message sending primitives. All feedback are appreciated. If you have a commercial interest around this project then feel free to contact [2]. [1] http://zeromq.org/ [2] mailto:sales@tweag.io -- Alexander Vershilov mail-to: alexander.vershilov(a)tweag.io -- Alexander

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