- Libraries - Haskell.org

Data.Map, Data.IntMap documentation
by Andriy Palamarchuk 19 Mar '08

19 Mar '08

Improved, fixed documentation for Data.Map, Data.IntMap. Moved time complexity Big-O values to the end of function descriptions. Added examples. For the initial review I submitted only changes for Data.Map. I'll update IntMap for the final review. Deadline - August 27 (two weeks). Ticket: http://hackage.haskell.org/trac/ghc/ticket/1611 Haddock output: http://hackage.haskell.org/trac/ghc/attachment/ticket/1611/Data-Map.html?fo… The module source and diff are also attached to the ticket. Andriy ____________________________________________________________________________________ Pinpoint customers who are looking for what you sell. http://searchmarketing.yahoo.com/

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haskell.org is accepted to GSoC
by Malcolm Wallace 18 Mar '08

18 Mar '08

Google announced last night that Haskell.org has been accepted as a mentoring organisation for this year's Summer of Code (amongst 175 Open Source organisations). http://code.google.com/soc/2008/ The game is on! Student applications open at 1900 UTC on Mon 24th March, and close at 2400 UTC on Mon 31st March. In the meantime, my _strong_ suggestion is for students to search for ideas amongst the many lists available on the web: http://hackage.haskell.org/trac/summer-of-code/ http://haskell.org/haskellwiki/Hac_2007_II/Projects http://haskell.org/haskellwiki/Hac4/Projects and when crafting your proposal: * post it to an appropriate mailing list for comments e.g. haskell-cafe, libraries, wxHaskell, cabal-devel (prefix your subject line with [GSoC] to make it easy to find) * use feedback from the list to improve your proposal. Potential mentors will rank your final submitted proposal based on your ability and commitment to engage with the wider Haskell community, in addition to technical merit. Proposals that will benefit the entire Haskell world will generally be ranked more highly than niche projects with only a few potential users. So things like Cabal-hacking, darcs-hacking, compiler-hacking, are good, as are new libraries to do tasks that are in high demand. (This is not an exhaustive list.) Regards, Malcolm

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Cabal's configure doesn't notice missing headers
by Valery V. Vorotyntsev 17 Mar '08

17 Mar '08

Hi, while installing zlib[1] from hackage, I've discovered possible Cabal's misbehaviour. There was no `zlib.h' in my system. runhaskell Setup configure went fine, with no complaints. It was only during build step when missing header had been noticed and an error reported. apt-get install zlib1g-dev; and zlib cabal package installation succeeded, but... Closer to my question. `zlib.h' _is_ mentioned in zlib.cabal: includes: zlib.h According to documentation[2], `includes' "field applies to both header files that are already installed on the system and to those coming with the package to be isntalled." [NB the typo] I think that Cabal should complain of missing headers during configuration step. At least of the ones explicitly mentioned in `includes:' field. 1. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/zlib-0.4.0.4 2. http://www.haskell.org/cabal/release/latest/doc/users-guide/x30.html#buildi… -- vvv

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runSTArray for multiple arrays
by Henning Thielemann 13 Mar '08

13 Mar '08

Currently, runSTArray can handle only one array: runSTArray :: Ix i => (forall s . ST s (STArray s i e)) -> Array i e Would it be possible to access multiple arrays successively by a function like runSTArraySplit :: Ix i => (forall s . ST s (STArray s i e, a)) -> (Array i e, ST t a) Hm, this would not work, because type variables 's' in 'a' had to be converted to 't' as well. Are there other ideas to tackle this problem?

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non-maintainer uploads to hackageDB
by Ross Paterson 12 Mar '08

12 Mar '08

I think we need, perhaps not a policy, but some agreed etiquette regarding uploads to hackageDB. (Please hold off on the technical suggestions until we've decided what behaviour we want.) Personally, I'd rather have all maintainers doing their own uploads. As I user, I'd like to know that someone takes responsibility for the whole of a package I download, including the packaging, and will be available for bug fixes and enhancements (such as making it work with the next GHC release). As this is free software, there's nothing to stop someone forking a package and maintaining their own version. Then as a user I'll need to choose between the two, but I'll still be looking for a maintainer of the whole package. It might be fair to ask that someone creating a fork change the name of the package in some way, to avoid confusion (and eating up the original maintainer's version numbers). This is a different situation from Linux or BSD distributions, where primary releases are repackaged to conform with native conventions. HackageDB is an upstream site, where people can make their own releases, using a common package format (Cabal). (Similarly I don't think we need the pristine+patches setup used by those distributions: maintainers should just take care of the pristine.)

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Proposal: add some missing tuple functions
by Don Stewart 12 Mar '08

12 Mar '08

Basic texts often define swap, fst3, snd3 and thd3 So let's add them to the rather bare Data.Tuple. The fst3.. series were approved to be added a couple of years ago, but I never got around to it. The patch is attached. -- Don

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Re: Data.HashTable
by Johannes Waldmann 08 Mar '08

08 Mar '08

Hello. I could build HsJudy-0.2, meanwhile. Thanks. It is not an immediate replacement for Data.Map or Data.HashTable, though? I figure I need some wrapper code (instances of Stringable and Refeable) but the documentation is somewhat terse. For Stringable I can guess the meaning of to/fromString, but I have no idea how I should implement the other methods. - (I also do not see why I need fromString.) For Refeable - what is the "Value" type? Best regards, Johannes.

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GetOpt bug causing it to mistakenly reject options as ambiguous
by Eelis van der Weegen 07 Mar '08

07 Mar '08

[This is a resend; I tried to post through gmane but the message never arrived.] There is a bug in System.Console.GetOpt causing it to mistakenly reject options as ambiguous. Testcase: > import System.Console.GetOpt > > type Color = String > > optsDesc :: [OptDescr Color] > optsDesc = [Option "" ["color", "colour"] (ReqArg id "color") "Foreground color"] > > main = do > let args = ["--col=blue"] > case getOpt RequireOrder optsDesc args of > (_, _, err:_) -> putStrLn err > _ -> return () Output: option `--col' is ambiguous; could be one of: --color=color, --colour=color Foreground color --color=color, --colour=color Foreground color This error is silly, because the two alternatives listed are the same option. The problem is caused by incorrect use of a generator in a list comprehension. I've attached a patch that fixes the problem. Regards, Eelis

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Data.HashTable
by Johannes Waldmann 06 Mar '08

06 Mar '08

Hello. When I insert 50 values in an empty hashtable, I get longest chains of length 10. Like this: import Data.HashTable ( HashTable ) import qualified Data.HashTable as H import System.Random main = do t <- H.new ( == ) H.hashInt sequence $ replicate 50 $ do x <- randomRIO ( 0 , 1000 ) H.update t x () lc <- H.longestChain t print lc output: [(831,()),(346,()),(773,()),(475,()),(812,()),(307,()),(113,()),(637,()),(100,())] This is not what I expected (quite the contrary). Did I miss something here? The access time is linear in the length of the longest chain? Perhaps the initial table (produced by "new") is too small, so the table is always overloaded? Looking at http://java.sun.com/javase/6/docs/api/java/util/HashMap.html they start out with table size 16 by default *and* (more importantly) they have a constructor that allows to set the initial table size and the load factor. Best regards, Johannes Waldmann.

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ANN: Takusen 0.8
by Alistair Bayley 06 Mar '08

06 Mar '08

Oleg and I are pleased to announce the release of Takusen 0.8. (Don Stewart did an interim 0.7 release for us a few weeks ago, and added us to Hackage. This release is a tidy-up of some loose ends, and some bug fixes. Hence, I've summarise the changes since the 0.6 release.) Changes since 0.6: - ODBC support. This still has a few gaps (and probably bugs and rough edges) but should be fairly usable. - support for reusable/persistent sessions, so you can hang onto the connection object between invocations of withSession (this was in release 0.6 but omitted from the release notes). - improvements to the Cabal Setup scripts, which should give better experiences for ghc-6.4, ghc-6.6, and ghc-6.8. The (eventual) 1.4 release of Cabal should be able to build our haddock docs, too. - improved UTF8 decoder (marshals directly from buffer). The release bundle: http://hackage.haskell.org/packages/archive/Takusen/0.8/Takusen-0.8.tar.gz The latest code: darcs get http://darcs.haskell.org/takusen Docs: http://darcs.haskell.org/takusen/doc/html/index.html A comprehensive description of API usage can be found in the documentation for module Database.Enumerator (look for the Usage section): http://darcs.haskell.org/takusen/doc/html/Database-Enumerator.html Future plans: - FreeTDS backend (Sybase and MS Sql Server) - support for Blobs and Clobs For those of you unfamiliar with Takusen, here is our HCAR blurb: Takusen is a library for accessing DBMS's. Like HSQL, we support arbitrary SQL statements (currently strings, extensible to anything that can be converted to a string). Takusen's `unique-selling-point' is safety and efficiency. We statically ensure all acquired database resources - such as cursors, connection and statement handles - are released, exactly once, at predictable times. Takusen can avoid loading the whole result set in memory, and so can handle queries returning millions of rows in constant space. Takusen also supports automatic marshalling and unmarshalling of results and query parameters. These benefits come from the design of query result processing around a left-fold enumerator. Currently we fully support ODBC, Oracle, Sqlite, and PostgreSQL.

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