- Libraries - Haskell.org

Re: [Haskell-cafe] Library Process (was Building "productionstable" software in Haskell)
by Claus Reinke 18 Sep '07

18 Sep '07

>> I thought the master plan was that less would come with the compiler / >> interpreter and the user would install packages using cabal. > > Ideally, yes. I think a useful model would be GNU/Linux, where there is > the Linux kernel, developed by core hackers, and then there are > "distributions", which package up particular kernels with a load of > different GNU libraries and utilities to form a complete operating > environment. The maintainers of the distributions do not work on the > kernel, but they do test their own combinations of kernel/libraries + > utilities to ensure that everything plays together nicely. > > I would like to see the same separation forming between the ghc compiler > itself (which would minimally include only the small number of libraries > needed to build the compiler), and larger "distributions" which would be > maintained by other people, and include much larger collections of > packages that the maintainer has tested and verified to work together. > In the best of all worlds, a Haskell "distribution" would include > multiple compilers, not just ghc. i think that such separately maintained distributions would be one way to avoid the version skew chaos that might otherwise result from dropping all but the minimal set of libraries from ghc/hugs/.. distributions. now everybody take a step back to make room for the volunteers?-) a slightly more lightweight approach, that could grow into the above, would be if cabal packages supported nesting/grouping, so that sets of useful/proven libs could be bundled into a single package (the whole package builds if all the subpackages build individually, and form a coherent whole; that is, there'd need to be tests checking that the subpackages are actually compatible versions). then, instead of extra-libs in ghc/hugs/.., there'd be a standard-libs package on hackage showing exactly which haskell implementations it builds&tests with successfully and which not. and one could still get a whole consistent and maintained? bunch of standard libs in one go. </dream> claus

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library submission: Data.Either.unzipEithers :: [Either a b] -> ([a], [b])
by Jeremy Shaw 17 Sep '07

17 Sep '07

http://hackage.haskell.org/trac/ghc/ticket/1695 This function is like unzip for a list of Eithers instead of tuples. According to google code search, I am at least the 5th person to implement this function: http://www.google.com/codesearch?hl=en&lr=&q=%22%5BEither+a+b%5D+-%3E+%28%5… I opted for the name unzipEithers because the function is similar to two existing functions: unzip and catMaybes. It seems less similar to partition, because partition does not desconstruct the values, it just divides them into to two groups. I have no particular attachment to the name however. I modeled the implementation after unzip and partition. Hopefully I made effective use of the irrefutable patterns and laziness, but someone else should verify. j.

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Statistics Module
by Marshall Beddoe 17 Sep '07

17 Sep '07

For my first contribution to the Haskell community, I was thinking of releasing a statistical computing module. Using google code, I found a few Stats.hs files contained in various projects, therefore I think it would be a good idea to have a unified module. Currently, my module contains all the base functions one would expect: arithmetic/geometric/harmonic mean, median, mode, range, average/standard deviation, variance, interquartile range, kurtosis and skew. Plans moving forward include histograms, covariance and principal and independent components. What would you all like to see in a module like this? Thanks very much, Marshall

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instance Eq (TChan a)
by Ashley Yakeley 15 Sep '07

15 Sep '07

Like most reference-like things, Control.Concurrent.STM.TChan should be in Eq, shouldn't it? It's not in stm=2.0, though it does have Eq (TVar a). -- Ashley Yakeley Seattle WA

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Parsec issue
by Lennart Kolmodin 11 Sep '07

11 Sep '07

Hi dear list, while using parsec for a project I ran into this issue. Take the following program: import Text.ParserCombinators.Parsec import Text.ParserCombinators.Parsec.Language import Text.ParserCombinators.Parsec.Token main = do run "0xf" run "xf" run str = putStrLn $ str ++ " parses as: " ++ show (parse p "" str) p = hexadecimal $ makeTokenParser emptyDef ----- Running it yields: 0xf parses as: Left (line 1, column 1): unexpected "0" xf parses as: Right 15 ----- Looking at the code for hexadecimal in Parsec.Token it looks like: hexadecimal = do{ oneOf "xX"; number 16 hexDigit } clearly not handling the leading zero as the docs states: hexadecimal :: CharParser st Integer Parses a positive whole number in the hexadecimal system. The number should be prefixed with "0x" or "0X". Returns the value of the number. Same goes for 'octal' in the same module. Parsing using 'natural' works though: nat = zeroNumber <|> decimal zeroNumber = do{ char '0' ; hexadecimal <|> octal <|> decimal <|> return 0 } Also, neither hexadecimal nor octal eat the trailing whitespaces as natural, integer and float does (using lexme). Am I missing something? Cheers, Lennart K

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Network.Socket.getaddrinfo
by Peter Simons 10 Sep '07

10 Sep '07

Hi, the module Network.Socket provides 'getaddrinfo' only if IPv6 support is enabled. That surprises me because, as far as I know, there is nothing IPv6-specific about that function. Does anyone know why that choice was made? Best regards, Peter

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Second Request for code review - Knuth Morris Pratt for Data.Sequence
by Justin Bailey 10 Sep '07

10 Sep '07

Using the code developed for ByteStrings by myself, Christ Kuklewicz and Daniel Fischer, I've implemented Knuth-Morris-Pratt substring searching on Data.Sequence "Seq" values. Attached you'll find the library in kmp.zip.safe. The algorithm is implemented in the module Data.Sequence.KMP. At the root, SpeedTest.hs can be compiled on Windows with the "prof_compile.bat" file included (you'll need to install the "regex-dfa" and "regex-base" packages from Hackage to build). SpeedTest searches for a known value in the 7 MB file "endo.dna" (which can be downloaded from http://www.icfpcontest.org/endo.zip) using several different algorithms and methods: strict and lazy bytestrings, regular expressions, and the KMP algorithm for "Seq" values. SpeedTest is pretty fast but I worry about its space usage. It may just be the nature of Seq values, but I cannot get it to run in constant space when I think it should be. I'm especially interested in help here. All comments and feedback are welcome. Since the zip file includes a darcs context file, feel free to send patches. Justin

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Re: patch applied (packages/regex-base): Make setup script compileagain after recent Cabal changes
by Claus Reinke 10 Sep '07

10 Sep '07

[subject taken from cvs-libraries@; discussion directed to libraries@] does anyone else feel that there is something wrong in haskell library land? i'm picking on cabal here as one of "the usual suspects", but it seems to have become the rule that otherwise stable code has to be fixed every so often, to accomodate new compiler versions, new library dependency versions, new cabal versions, new xyz versions,.. it is almost as if everything feels free these days to evolve in non- backwards-compatible ways, following the motto "what do i care for my apis of yesterday?". with the ongoing trend towards separately evolving libraries rather than prepackaged kitchen-sink releases, this means that useful libraries die quickly, and have to be revived continuously, or they will be left behind. one symptom is "get the latest from hackage" replacing useful extra libraries kept in sync with each other (never mind that the hackage versions are no more likely to work without fixes than the in-repository versions). it is often small things ("that function/option has been renamed", "you now need to import x instead of y", "you can work around this by using 2 cabal files, then removing one depending on context", etc.), but as all dependencies keep eroding in this way, haskell projects are now built on sand rather than firm foundations, requiring constant attention just to avoid falling behind - attention that would better be focussed on development than maintenance. just a thought, claus ps. perhaps i've misunderstood, and there is in fact a haskell cabal trying to introduce as many version incompatibilities as possible, to ensure a market demand for cabal.. ?-)

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Patch with new API for get/setsockopt
by Matthew Danish 09 Sep '07

09 Sep '07

Hi, Russell O'Connor pointed out the other day that it is impossible to use the getSocketOption/setSocketOption functions on options which expect or provide a non-Int value. I've concocted another API which allows values to be constructed from a specific disjoint union. This should make it possible to use options like SendTimeOut which expect a struct timeval. The attached darcs patch to the network package has the new functions setSockOpt/getSockOpt and SocketOptionValue. Whether or not those will be the final names, I am not sure. Also, I thought of some better possible interfaces, but on Ian's suggestion I stuck to Haskell'98 capabilities only. I've tested it on Linux/x86-64 and run the validate script. I'm new to GHC development, though, so I'm not sure if I should just go ahead and submit the patch. -- -- Matthew Danish -- user: mrd domain: cmu.edu -- OpenPGP public key: C24B6010 on keyring.debian.org

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Re: ANNOUNCE: Cabal 1.2.0 released
by Thomas Schilling 09 Sep '07

09 Sep '07

On Thu, 2007-09-06 at 21:00 +0400, Bulat Ziganshin wrote: > Hello Thomas, > > Thursday, September 6, 2007, 8:35:19 PM, you wrote: > > We are pleased to announce that Cabal version 1.2.0 is now available. > > i suggest you to forward announce into main haskell maillist too > > major release of such important library is definitely news interesting > for many haskellers Well, I think I should have been a little clearer about the status of this release. Let me clarify. Earlier releases were preceded by release candidates before the .0 release. However, we changed it this time so that .0 basically is the release candidate and .1 will then be the first stable release. Therefore, we decided to post only to the developer mailing lists, so that the first release to the wider public (1.2.1) will, hopefully, have most issues resolved. / Thomas

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