- Libraries - Haskell.org

Re: cabal-install calls setup with unrecognised distpref flag
by José Pedro Magalhães 19 Aug '08

19 Aug '08

Hello all, I decided to bring this to libraries(a)haskell.org too in case anyone had the same problem before. Cheers, Pedro On Wed, Aug 6, 2008 at 11:38, José Pedro Magalhães <jpm(a)cs.uu.nl> wrote: > Hello all, > > Recently, while developing a package here in the group, we changed the > build-type from "Simple" to "Custom" to allow for "cabal test". The Setup.hs > simply calls defaultMainWithHooks with simpleUserHooks where runTests has > been redefined. > > The problem is that this change gives me the following error when invoking > "cabal build" (after invoking "cabal configure"): > setup.exe: Unrecognised flags: > --distpref=dist > > runhaskell Setup.hs build works fine, though. This happens on a win64 > machine, cabal-install version 0.5.1 using version 1.4.0.1 of the library. > On a mac there seem to be no problems, though. > > Am I doing something wrong? > > > Thanks, > Pedro >

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Re: [Haskell] ANN: witness 0.1, open-witness 0.1, "Witnesses and Open Witnesses"
by Don Stewart 18 Aug '08

18 Aug '08

ashley: > witness 0.1 > A witness is a value that witnesses some sort of constraint on some list > of type variables. This library provides support for simple witnesses, > that constrain a type variable to a single type, and equality witnesses, > that constrain two type variables to be the same type. The library also > provides classes for representatives, which are values that represent types. snip > open-witness 0.1 > Open witnesses (type IOWitness) are simple witnesses that can witness to > any type. However, they cannot be constructed, they can only be > generated in certain monads: snip > Hackage: > <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/open-witness> > Source: <http://code.haskell.org/open-witness/> You can find these packages for your local Arch Linux distribution, http://aur.archlinux.org/packages.php?ID=19194 http://aur.archlinux.org/packages.php?ID=19195 Come on Debian! :) -- Don

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Re: laziness of intersperse
by Thomas Schilling 17 Aug '08

17 Aug '08

On Sun, Aug 17, 2008 at 9:43 AM, Barton C Massey <bart(a)cs.pdx.edu> wrote: > Maybe something like > > intersperse _ [] = [] > intersperse sep (x : xs) = > x : concatMap ((sep :) . (: [])) xs > > is clearer (maybe), but I doubt it's as efficient (although > I haven't checked). concatMap is a bit tricky when it comes to performance. I also think the low-level loop implementation that duncan showed is rather readable. > Thanks much for the corrections! (I hope it's OK to do this on-list.) Of course. Nobody gets it right the first time. (Well, maybe Oleg. But then again we have some doubts whether he is from this planet or, if he is, perhaps from the future.)

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laziness of intersperse
by Reid Barton 16 Aug '08

16 Aug '08

(This is the same issue as http://www.haskell.org/pipermail/haskell/ 2004-March/013739.html but there was no follow-up at that time.) The intersperse library function is not as lazy as it could be. The current definition of intersperse is intersperse :: a -> [a] -> [a] intersperse _ [] = [] intersperse _ [x] = [x] intersperse sep (x:xs) = x : sep : intersperse sep xs For any list (x:xs) not containing _|_, intersperse sep (x:xs) is a list of the form (x:...); yet intersperse sep (x:_|_) = _|_ because the pattern match on the second equation diverges. A better definition would be intersperse _ [] = [] intersperse sep (x:xs) = x : intersperseWithPrefix xs where intersperseWithPrefix [] = [] intersperseWithPrefix (x:xs) = sep : x : intersperseWithPrefix xs (slightly modified from http://www.haskell.org/pipermail/haskell/2004- March/013741.html) An application: There was a question on #haskell about how to compute the "ruler" sequence [1,2,1,3,1,2,1,4,1,2,1,3,1,2,1,5,...]. The definition ruler = fix ((1:) . intersperse 1 . map (1+)) works with the properly lazy intersperse, but not with the intersperse in Data.List. Comments on this new definition? Can it get added to Data.List? Regards, Reid Barton

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darcs patch: Fix oversight in Control.OldException
by Bertram Felgenhauer 16 Aug '08

16 Aug '08

Sat Aug 16 15:26:31 CEST 2008 Bertram Felgenhauer <int-e(a)gmx.de> * Fix oversight in Control.OldException The NonTermination constructor slipped through in the Exception instance.

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proposal #2517: remove 'pure' method from Arrow class
by Ross Paterson 16 Aug '08

16 Aug '08

The Arrow class as originally defined by John Hughes had methods arr, >>> and first. (>>> has since been moved by #1773 to the Category class.) When writing the "Fun of Programming" paper, I added pure as a synonym for arr, because Richard Bird preferred it. However this name hasn't caught on, and now it clashes with a method in the Applicative class, so I propose to remove it. The usual practice would be to deprecate the name in one release and remove it in the following one, but I propose to remove it in one step because * no-one seems to be using this name, and * backward compatibility has been broken anyway by the Category split (#1773). The only people who will be bitten by the change are those who import Control.Arrow hiding pure, and they wouldn't be warned by deprecation.

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RE: [nightly] 10-Aug-2008 build of HEAD on i386-unknown-linux (cam-02-unx.europe.corp.microsoft.com)
by Simon Peyton-Jones 15 Aug '08

15 Aug '08

| -fgenerics -Wall -fno-warn-deprecated-flags -c Data/Time/Calendar/Gregorian.hs -o | dist/build/Data/Time/Calendar/Gregorian.o -ohi dist/build/Data/Time/Calendar/Gregorian.hi | | Data/Time/Calendar/Gregorian.hs:73:9: | Warning: orphan instance: instance Show Day | | <no location info>: | Failing due to -Werror. | | gmake[2]: *** [dist/build/Data/Time/Calendar/Gregorian.o] Error 1 | gmake[2]: Leaving directory `/playpen/simonmar/nightly/HEAD/i386-unknown-linux/libraries/time' | gmake[1]: *** [make.library.time] Error 2 | gmake[1]: Leaving directory `/playpen/simonmar/nightly/HEAD/i386-unknown-linux/libraries' | gmake: *** [stage1] Error 2 Now that orphan warnings are "proper warnings" as Duncan requested, and hence do the right thing with -Werror, someone should either remove this orphan (best), by moving the instance to the module that defines Day, or add -fno-warn-orphans to this module. Who is responsible for the time/ library? There may be other libraries similarly affected. Simon

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ANN: Initial release of Language.C (language-c-0.3)
by Benedikt Huber 14 Aug '08

14 Aug '08

Hi all, I'm pleased to announce the first release of Language.C, a library for analysing and generating C code. This release features * A reasonably well tested parser handling and recording all of C99 and most GNU extensions, most notably gcc's attribute syntax. * A pretty printer generating source code from the AST, covering the same language subset as the parser. * A preview of the analysis framework, including functionality for dissecting C's cruel type and variable declarations. Places: * The project's homepage is located at http://www.sivity.net/projects/language.c (Getting Started, Bug Tracker) * The package is available via hackage (language-c-0.3) * darcs repo: http://code.haskell.org/language-c * API docs: http://code.haskell.org/~bhuber/docs/language-c-latest/ The library originated from the C-related code in c2hs (http://www.cse.unsw.edu.au/~chak/haskell/c2hs/ ), and is the topic of my SoC project, mentored by Iavor Diatchki. (Iavor, Don Steward and Duncan Coutts provided great support, thank you) Feedback and suggestions in any form are most welcome, especially because there is a large range of features which could be implemented. The current status and a few ideas for the next releases are summarized at http://www.sivity.net/projects/language.c/wiki/ ProjectPlan. best regards, benedikt

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ANN: protocol-buffers (very early edition) version 0.0.5
by Chris Kuklewicz 14 Aug '08

14 Aug '08

Hi all, The Haskell version of protocol-buffer is still pre-bootstrap, but further, so there is a 0.0.5 release on http://hackage.haskell.org/cgi-bin/hackage-scripts/package/protocol-buffers and a darcs repository on http://darcs.haskell.org/packages/protocol-buffers/ The leading 0.0 in the type should show how early this code is :) What are protocol buffers? The are google's data interchange format: http://code.google.com/apis/protocolbuffers/docs/overview.html > What are protocol buffers? > > Protocol buffers are a flexible, efficient, automated mechanism for > serializing structured data – think XML, but smaller, faster, and simpler. You > define how you want your data to be structured once, then you can use special > generated source code to easily write and read your structured data to and from > a variety of data streams and using a variety of languages. You can even update > your data structure without breaking deployed programs that are compiled against > the "old" format. In addition to a manual translation of the self describing 'decriptor.proto' it has a partial code generator in Gen.hs and a stub of a parser in ProtoParser.hs and an intermediate data type in WireMessage.hs that I expect to sit between the byte stream reader/writer and the message types. Eventually the parser with read 'decriptor.proto' and the generator will emit source code to replace the manual translation. FAQ 1: Why is the Text.DescriptorProtos.* hierarchy so huge and the imports so plentiful? ANSWER 1: The namespace management. The namespace paradigm is the nested OO style namespace of C++, so I need modules and imports to fake nested Haskell namespaces. Cheers, Chris Kuklewicz

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PROPOSAL: More base package breakup
by Ian Lynagh 13 Aug '08

13 Aug '08

Hi all, This is trac #1338: http://hackage.haskell.org/trac/ghc/ticket/1338#comment:14 http://hackage.haskell.org/trac/ghc/attachment/ticket/1338/packagegraph.png Initial deadline: 21 Aug (2 weeks). The base package is still a large, unwieldy beast, making it hard to develop and debug. If possible, I'd like to cut it down a bit more before the 6.10 release. I won't inline all the details here, as it's a huge amount of text and an image, but basically I'm proposing to: * Create packages: timeout, unique, concurrent, st, system, numeric, generics, version, getopt, debug, printf ghc-exts * Merge what I've listed as "control" into "containers" There's definitely a "foreign" package fighting to get out too, but that needs more work before we can set it free. An important point to note is that Simon Marlow has made a base 3 compatibility library that will come with GHC 6.10, and will provide the same interface as the base library that came with 6.8, so breaking backwards compatibility in base 4 shouldn't cause large problems like the base 2 to base 3 change did. Thanks Ian

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