May 2010 - Haskell-Cafe

posting UTF8 data with Curl library
by Eugeny N Dzhurinsky 06 May '10

06 May '10

Hello! I need to submit data to HTTP server using UTF8 encoding. I found out that libcurl for haskell can work with Data.ByteString - but it seems not able to work with Data.ByteString.UTF8. Can you please advice, how do I convert Data.ByteString.UTF8 into Data.ByteString and visa versa? Thank you in advance! -- Eugene Dzhurinsky

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macosx-app for wxHaskell
by Bill Atkins 05 May '10

05 May '10

In order to run apps built with wxHaskell on OS X, you're supposed to wrap the binary using a script called macosx-app ( http://www.haskell.org/haskellwiki/WxHaskell/MacOS_X) Unfortunately, after running "cabal install wx" this file is not in "~/.cabal" - it's also not in the wxHaskell source. Does anyone know where I can find it? Thanks, Bill

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Would it be evil to add "deriving Typeable" to newtype Q?
by Leonel Fonseca 05 May '10

05 May '10

Hi everybody, Is it reasonable to add "deriving Typeable" to newtype Q? In case you wonder why I want to do that, it is because I've constructed a Q [Dec] inside a monad, I want to extract it from the monad (via runIO) and the monad has constraint "Typeable" over this parameter. I've also tried to write the Typeable instance in my own module (not Language.Haskell.TH.Syntax). But I've got no luck since the Q type constructor is exported but the data constructor is not. Thanks. -- Leonel Fonseca.

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ANN: Holumbus-Distribution 0.1.0 - distributed data structures
by Stefan Schmidt 05 May '10

05 May '10

Hello, after a long year, I've finally managed to upload the new version of Holumbus-Distribution to Hackage. Holumbus-Distribution offers distributed data structures like Chan, MVar or functions. These data types can be used for inter-process communication. With the help of this library it is possible to build Erlang-Style mailboxes for an easy implementation of distributed systems in Haskell. You can find the library on Hackage at: http://hackage.haskell.org/package/Holumbus-Distribution And the project homepage at: http://www.holumbus.org (for the current documentation please refer to the example programs in the source bundle, the Wiki will be updated soon) The following data structures are implemented so far: * distributed Chan (DChan) like the Chan datatype, but it allows the writing and reading from other programs * distributed MVar (DMVar) like the MVar data type, but the content of the MVar is shared among multiple programs. * distributed Functions (DFunction) an easy way to do remote procedure calls, just like haxr * distributed Values (DValue) a variable which could only be written once and which could easily read by other programs * distributed Streams and Ports (DStream, DPort) just like the DChan, but this time, you are only allowed to read from the channel from one program This library was completely rewritten between version 0.0.1 and 0.1.0. The old packages can be found under Holumbus.Network.* while the new ones are located at Holumbus.Distribution.*. The old packages will be removed in future versions (0.2.0). This library itself is independent from other Holumbus libraries although it contains some modules which are only to be used by the other Holumbus libraries but this may change in the near future. Regards, Stefan

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Benchmarks game updated to ghc 6.12.2
by Isaac Gouy 05 May '10

05 May '10

Ketil Malde <ketil at malde.org> writes: > As for code size, the programs are heavily tuned for speed. iirc there was a community effort 2 or 3 years ago, but now ghc has changed enough that the compiler and runtime parameters seem to need re-tuning. > Is it an idea to go back a few steps to more idiomatic code? Perhaps as a separate "track"? There's always room for 2 or 3 Haskell programs per task - not necessarily The Good, the Bad and the Ugly - but you'll already find the cliched example of a faster more convoluted Haskell program and a more concise but slower Haskell program. (Idiomatic code? Aren't there idioms for writing fast Haskell too?) > I also worry a bit that source code optimization for a specific > compiler makes it more difficult to take advantage of compiler > optimization improvements. These are tiny tiny programs - when those compiler optimization improvements arrive re-write the programs to take advantage of them ;-)

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ANNOUNCE: happstack 0.5.0
by Jeremy Shaw 05 May '10

05 May '10

(Note: Reply-to is set to haskell-cafe(a)haskell.org) Hello, I am very pleased to announce Happstack 0.5.0. It should install cleanly from hackage via: cabal install happstack If it does not, please report errors to the happstack mailing list: http://groups.google.com/group/HAppS (You will, unfortunately, need to be subscribed due to SPAM issues). Here are the official release notes: Release Notes: This release should fix many (hopefully all) known cabal install related issues. It also includes many other improvements detailed below. Known issues: * dropped support for GHC 6.8. GHC 6.10 and 6.12 currently supported. * happstack-data compiled with -O0 due to bug in cabal http://thread.gmane.org/gmane.comp.lang.haskell.cafe/69215 You may be able to change that to -O2 if you first do: cabal install --reinstall syb-with-class --disable-documentation But we need a solution that works automatically when people run, cabal install happstack. Changes since 0.4.1: * many IxSet improvements by Gracjan Polak - hide IxSet constructor. use ixSet instead. - improved efficiency of gteTLE, getGTE, and getRange - get rid of Dynamic, just use Data.Typeable (internal change) - added deleteIx - Eq and Ord instances for IxSet - removed a bunch of cruft - greatly improved documentation - added stats function - Protect user from using unindexed keys in searches in IxSet - Runtime safeguard for badly formed inferIxSet indexes - Fixed IxSet Default instance - More detailed error messages in IxSet * work around bug in bytestring which causes the server to hang (http://hackage.haskell.org/trac/ghc/ticket/3808) * support for uincode Text and lazy Text types - Serialize/Version instances now provided automatically by happstack-data - instances of EmbedAsChild and EmbedAsAttr for Text for Identity, IdentityT, ServerPartT, and WebT. - patches sent upstream to HSP, waiting on acceptance * Added Serialize/Version instances for time / Data.Time library * Improvements to GuestBook demo by Gracjan Polak - better handling of Ctrl-C - simplified .cabal to only build executable * Improvements to GuestBook demo by Gracjan Polak - nice command line interface with help message and version information - restructured parsing of command line to make it scale better with further parameters - added reference to Paths_guestbook module to enable incorporating version and path information generated by cabal. - added withLogger transformer guaranteeing clean setup and teardown of loggers - Added clean shutdown to logging component. * fail instance for WebT now includes location of pattern match failure. e.g. src\AppControl.hs:43:24: Pattern match failure in do expression * added expireCookie function * Improvements to documentation * Additional test cases * Fixes many build failures * Experimental: Added proof of concept port of happstack-server to WAI. http://www.haskell.org/pipermail/haskell-cafe/2010-March/ 074142.html * added 'dirs' guard. (Similar to dir, but for a list of path components). * set SO_KEEPALIVE so that dropped connections will eventually time out * happstack-util only depends on QuickCheck when compiled with -ftests. This is wrong but solves a lot of annoy install failures. * file serve functions now use MonadPlus instead of setting explicit 404 * XMLMetaData for webHSP * Allow colons in cookie names Contributors: A big thanks to everyone who contributed patches for this release, including: Gracjan Polak (25 patches in this release!) Simon Meier Paulo Tanimoto Joachim Fasting Antoine Latter Simon Michael Adam Vogt Joe Edmonds Andrea Vezzosi Nils Schweinsberg

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Anglohaskell preparations?
by Philippa Cowderoy 05 May '10

05 May '10

Hi everyone. It's just over three months until the traditional time for Anglohaskell, so I wanted to ask: is anyone willing to step up and run it this year? We had a volunteer at last year's event, but I've forgotten who. It was also suggested that emails about the organisation and planning of the event be sent to the Hackathon mailing list, though it might be an idea to keep this thread on -cafe for now. If the event's going to run, we really need to try for dates and a venue in the next month or so. It's been a great event in previous years, and I'd love for it to happen again! -- flippa(a)flippac.org

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Re: Learning about Programming Languages (specifically Haskell)
by Samuel Williams 04 May '10

04 May '10

Also, one more thing - if someone could write some comments to go along with the source code that explain what it is doing, that would be really helpful. I can see the general structure, but I don't know the ins and outs of Haskell. If someone could augment the example with comments explaining what the functions do that would be great! data Door = Open | Closed deriving Show toggle Open = Closed toggle Closed = Open pass k = zipWith ($) (cycle $ replicate k id ++ [toggle]) run n = foldl (flip pass) (replicate n Closed) [0..n] Do I need to add run 100 to the end of the example for it to actually do something?

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ANNOUNCE: happstack-hamlet: compile-time HTML templates for the Haskell application server stack
by Jeremy Shaw 04 May '10

04 May '10

Hello, I am pleased to announce the availability of happstack-hamlet: http://hackage.haskell.org/package/happstack-hamlet http://patch-tag.com/r/mae/happstack/snapshot/current/content/pretty/happst… Happstack is a web application development framework. Hamlet provides HTML templates which are checked for correctness at compile time. This package add support for using Hamlet templates with Happstack. A simple demo is available here: http://patch-tag.com/r/mae/happstack/snapshot/current/content/pretty/happst… Please report any issues with the happstack-hamlet package itself to the happs mailing list (You will need to be subscribed): http://groups.google.com/group/happs Big thanks to Michael Snoyman for writing Hamlet! Hamlet homepage: http://docs.yesodweb.com/hamlet/ Happstack homepage: http://www.happstack.com/ happy hacking! - jeremy p.s. Reply-to is set to haskell-cafe

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Installing ghc in an OpenSolaris Zone
by Günther Schmidt 04 May '10

04 May '10

Hello, has anyone yet managed to install ghc (6.10.4) into an OpenSolaris zone? Günther

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