February 2009 - Libraries

bug in System.Info in ghc 6.8.2 and ghc 6.10.1
by David Roundy 01 Mar '09

01 Mar '09

It seems that System.Info.compilerVersion doesn't know the minor release number of ghc. This looks like a bug to me. -- David Roundy

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Deadlock when using Control.Concurrent.Chan
by Ben Franksen 01 Mar '09

01 Mar '09

This code demonstrates the problem: import Control.Concurrent import Control.Concurrent.Chan import Control.Monad test = do c <- newChan forkIO $ forever $ do i <- readChan c print i writeChan c 1 threadDelay 1000000 isEmptyChan c >>= print Test session: ben@sarun[1]: .../hca/current > ghci Bug5.hs GHCi, version 6.10.1: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. [1 of 1] Compiling Main ( Bug5.hs, interpreted ) Ok, modules loaded: Main. *Main> test 1 The program hangs here. This is a deadlock caused by the calls to isEmptyChan and readChan both waiting on the same MVar, as a quick look at the sources reveals. I don't have an immediate fix but is shouldn't be too hard to find one. I can try to, if it is consensus that this is a bug. Incidentally, if I replace Chan with TChan (and wrap all xxxTChan calls in an atomically), then this code terminates just fine. Cheers Ben

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darcs patch: Expose socket internals in a new module. (and 3 more)
by Ian Lynagh 01 Mar '09

01 Mar '09

Sun Feb 1 21:55:08 GMT 2009 Johan Tibell <johan.tibell(a)gmail.com> * Expose socket internals in a new module. Expose some of the internals in a new module, Network.Socket.Internal, to make it easier to extend the functionality of the library. Sat Feb 28 08:59:05 GMT 2009 Johan Tibell <johan.tibell(a)gmail.com> * Expose protocol family data type and helpers in internals module. Ignore-this: 23fdb3b21bac47c98dcb2a0212f9b0d7 Sat Feb 28 09:05:39 GMT 2009 Johan Tibell <johan.tibell(a)gmail.com> * Whitespace changes only (remove tabs). Ignore-this: 3a695c355c6122ea13360046512b58f9 Sat Feb 28 10:00:24 GMT 2009 Johan Tibell <johan.tibell(a)gmail.com> * Added more documentation. Ignore-this: daae026cbffc50163316e5d7815be87e

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lhs2TeX Build Failure
by Dominic Steinitz 28 Feb '09

28 Feb '09

The latest version (1.14) on hackage fails under ghc --version The Glorious Glasgow Haskell Compilation System, version 6.10.1 Curiously, I think I built it at work under windows yesterday but maybe I was using ghc 6.8. I can't check until Monday. FileNameUtils.lhs:81:35: Ambiguous type variable `b' in the constraint: `GHC.Exception.Exception b' arising from a use of `catch' at FileNameUtils.lhs:(81,35)-(89,60) Probable fix: add a type signature that fixes these type variable(s) FileNameUtils.lhs:98:44: Ambiguous type variable `e2' in the constraint: `GHC.Exception.Exception e2' arising from a use of `try' at FileNameUtils.lhs:98:44-57 Probable fix: add a type signature that fixes these type variable(s) FileNameUtils.lhs:118:35: Ambiguous type variable `e1' in the constraint: `GHC.Exception.Exception e1' arising from a use of `catch' at FileNameUtils.lhs:(118,35)-(119,104) Probable fix: add a type signature that fixes these type variable(s) FileNameUtils.lhs:122:35: Ambiguous type variable `e' in the constraint: `GHC.Exception.Exception e' arising from a use of `catch' at FileNameUtils.lhs:122:35-54 Probable fix: add a type signature that fixes these type variable(s)

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cabal install profiling and documentation
by Ben 27 Feb '09

27 Feb '09

hi -- i asked this on haskell cafe but got no response. here it is again: i've gone and cabal installed a lot of packages, but now i want to go back and install their profiling libraries and documentation. is there an easy way of doing this, short of reinstalling all of them (in the proper dependency order)? thanks, ben

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Data.List.select
by Christian Maeder 27 Feb '09

27 Feb '09

Libraries-List, browsing through the sources of Data.List I discovered "select", which is only used for the implementation of partition and not exported. Can someone explain, why the irrefutable pattern "~" is used? Both components are used in both branches. select :: (a -> Bool) -> a -> ([a], [a]) -> ([a], [a]) select p x ~(ts,fs) | p x = (x:ts,fs) | otherwise = (ts, x:fs) Why is it not just in where-clause? Doesn't "INLINE partition" work then? Cheers Christian

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documentation of Data.List.intersect(By)
by Christian Maeder 26 Feb '09

26 Feb '09

Hi, for Data.List.intersect I'm missing the documentation that the element order in the result list is taken from the first list. The comment "If the first list contains duplicates, so will the result." indicates that, but also the example could be improved to show this: > [1,2,2,3,4] `intersect` [6,4,4,2] == [2,2,4] Cheers Christian

1 0

modules of cabal-install
by Christian Maeder 25 Feb '09

25 Feb '09

Hi, I would like to reuse the module Distribution.Client.Tar from the cabal-install package. Are you willing to split up your package? Is it worth to have single module packages? Currently, Distribution.Client.Tar depends on Distribution.Client.Utils.writeFileAtomic, but this final call could be left to the user. Maybe writeFileAtomic should be in another package, too? Trying to avoid copying source code, Christian

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ANN: bug fix for regex-tdfa, version 0.97.4 (and "regex-ast")
by ChrisK 24 Feb '09

24 Feb '09

Hello, The regex-tdfa package has had a series of bug fix releases (0.97.1 and 2 and 3 and now 4). This 0.97.4 releases finishes fixing the bug that was only mostly fixed in the 0.97.1 release. An example of the fixed bug: Apply the regex pattern (BB(B?))+(B?) to the text BBBB. The "BB" in the pattern should be used twice and both "B?" should match nothing. My code grouped the "+" wrong and matched the "BB" once and then both the "B?" matched a "B". The case fixed here was not initially caught because of how I search for unknown bugs. I use "Arbitrary" from QuickCheck to generate random patterns and strings to search, and compare regex-tdfa to another POSIX engine. Because I am on OS X, I am limited by the the native POSIX libraries bugs: this bug in regex-tdfa was triggered only when the native POSIX was also buggy. But the source of most of my unit tests is AT&T research [1], and they have a "libast" with a POSIX implementation. I have adapted my regex-* wrapper packages to make a "regex-ast" Haskell interface, but the difficulties with the AT&T headers prevent me from releasing this on hackage. This "regex-ast" has given me access to a less buggy POSIX back-end, and randomized testing has led to catching the bug fixed here (as well as a few bug reports back to AT&T). So while regex-tdfa will not win many speed contests, it is the only POSIX regular expression library I have running that passes all the unit tests. [1] http://www.research.att.com/sw/download/ http://www.research.att.com/~gsf/testregex/ http://www.research.att.com/~gsf/testregex/re-interpretation.html

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Re: Pickling a finite map (Binary + zlib) [was: Data.Binary poor read performance]
by Christian Maeder 24 Feb '09

24 Feb '09

Felipe Lessa wrote: > The builds seem fine, but we spot a (length xs) on the beginning. > Maybe this is the culprit? We already know the size of the map (it was > serialized), so it is just a matter of exporting > > fromDistinctAscSizedList :: Int -> [(k, a)] -> Map k a Excellent idea, what does stop you? fromDistinctAscList is already a function with a precondition that is not checked. > Too bad 'Map' is exported as an abstract data type and it's not > straighforward to test this conjecture. Any ideas? One really doesn't want to see the actual implementation (except for debugging or tuning purposes), but maybe conversions to and from a fully (and uniquely) balanced binary tree are desirable. (a basic binary tree data type is still missing on hackage). I think, equal maps should not yield different serialization results just because the internal tree structure happens to be different, but that's of course debatable. Cheers Christian Maybe the discussion should be continued on libraries(a)haskell.org?

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