January 2009 - Haskell-Cafe

Cabal dependencies
by Stephen Hicks 20 Jan '09

20 Jan '09

Hi, I'm having some difficulty specifying dependencies in my .cabal file for a package I'm looking to upload to hackage soon. The difficulty is as follows. I basically want to specify parsec (>= 2.1 && < 3.0.0) || (> 3.0.0 && < 4) The problem is that 3.0.0 as it exists on hackage is missing a constructor that I need (namely, Postfix, in the compatibility module). The bug was fixed and will presumably work fine if a newer version of parsec is ever uploaded to hackage, and my package works fine with older parsecs as well - I just want to exclude this one version. How can I go about doing that? A secondary question is this - I can actually compile with version 3.0.0 by just not using this constructor, although it does reduce the package's functionality. I've seen flags in various .cabal files, and presumably I could invent a flag to make it work with 3.0.0, but I'm confused about how these flags are set. Specifically, cabal-install has never asked me anything about flags, so what's the point? Or does it automatically set whichever flags satisfy the dependencies? Thanks, steve

2 1

xhtml + bytestring
by Joachim Breitner 20 Jan '09

20 Jan '09

Hi Bjorn, hi list, the darcswatch instance I’m running is getting quite big, and it periodically slows down my server. I managed to get quite an improvement with this simple patch to my parsing: http://darcs.nomeata.de/cgi-bin/darcsweb.cgi?r=darcswatch;a=commitdiff;h=20… Since the new HTTP library, my code runs completely on ByteStrings, only the xhtml library expects me to feed strings. I tried to fix this and created a patch against xhtml-3000.2.0.1 to work internally with lazy ByteStrings. It’s API-compatible to the normal xhtml library, it just adds showHtml', renderHtml' and prettyHtml' that output lazy ByteStrings, and that has Html instances for strict any lazy ByteStrings. There were some speed and space improvements, but none horrific (at least for DarcsWatch, most of the time goes into parsing the repositories and mails, and into sorting that data). Unfortunately, I can’t use it in the live installation until I upgrade the machine from Debian etch to lenny, as the bundled bytestring library in ghc-6.6’ base is too old. Nevertheless, I’m sharing my patch here, maybe it’s useful for some, or maybe it can be the base for an official xhtml release with bytestrings inside. To speed things up even more one should probably create a type analogous to ShowS, i.e. (L.ByteString -> L.ByteString), that allows you to concatenate ByteString chunks cheaply. I also noted that the current version of bytestring implements "concatMap" in a way that is guaranteed to rip apart the string into very small chunks, even if the mapped function returns the same character most times (as it is the case for the Html escaping function). Therefore, I wrote this function: -- | More efficient variant of 'L.concatMap' concatMapL' :: (Char -> String) -> L.ByteString -> L.ByteString concatMapL' f s = go s where go s = let (unmodified, modified) = L.span (\c -> f c == [c]) s in case L.uncons modified of Nothing -> unmodified Just (c,rest) -> L.pack (f c) `L.append` go rest Does this make sense? Should it maybe replace the function in the library? Greetings, Joachim [1] http://darcswatch.nomeata.de/ -- Joachim "nomeata" Breitner mail: mail(a)joachim-breitner.de | ICQ# 74513189 | GPG-Key: 4743206C JID: nomeata(a)joachim-breitner.de | http://www.joachim-breitner.de/ Debian Developer: nomeata(a)debian.org

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Haskell and C++ program
by Sukit Tretriluxana 19 Jan '09

19 Jan '09

Hi all, I was looking around Stroustrup's website and found a simple program that he showed how standard library can be used to make the program succinct and safe. See http://www.research.att.com/~bs/bs_faq2.html#simple-program. I wondered how a Haskell program equivalent to it looks like and I came up with the code below. import qualified Control.Exception as E main = E.catch (interact reverseDouble) (\_ -> print "format error") reverseDouble = unlines . doIt . words where doIt = intro . toStrings . reverse . toDoubles . input toDoubles = map (read::String->Double) toStrings = map show input = takeWhile (/= "end") intro l = ("read " ++ (show $ length l) ++ " elements") : "elements in reversed order" : I'm not a Haskell expert and I am pretty sure that this is not the optimal form a Haskell program that's equivalent to the C++ one. So I would like to see, from the Haskell experts in this group, how else (of course better form) such a program can be written. Thanks, Ed

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know a workaround for greedy context reduction?
by Nicolas Frisby 19 Jan '09

19 Jan '09

With these three declarations {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE UndecidableInstances #-} class C a where c :: a class C a => D a where d :: a instance C a => D a where d = c ghci exhibits this behavior: *> :t d d :: (C a) => a Where I would prefer "d :: (D a) => a". In my actual examples, the context is much larger and I can't involve overlapping instances. Is there a known workaround? I didn't find a related bug on the GHC trac, and I don't know if other compilers behave in the same way.

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LinuxFest Northwest 2009
by Shachaf Ben-Kiki 19 Jan '09

19 Jan '09

LFNW 2009 (<http://linuxfestnorthwest.org/>) is going to be at the end of April, and I was wondering if anyone here is going to be there, or possibly a Haskell-related presentation. Last year I met ac from #haskell there, but it would be nice if more people came, especially with the (relatively) big group in Oregon and such. Perhaps someone here has plans already? Shachaf

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Haskell Weekly News: Issue 101 - January 19, 2009
by Brent Yorgey 19 Jan '09

19 Jan '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20090119 Issue 101 - January 19, 2009 --------------------------------------------------------------------------- Welcome to issue 101 of HWN, a newsletter covering developments in the [1]Haskell community. Gee whiz, people, stop being so darn productive or you're going to burn me out. Seriously. Announcements curl-1.3.4. Sigbjorn Finne [2]announced that a new version of [3]curl, a complete Haskell binding to the libcurl API, is now available and have been uploaded to Hackage. The most notable change is the overloading of representation of response buffers (and headers), allowing for the use of ByteStrings. Turbinado V0.4. Alson Kemp [4]announced the release of version 0.4 of [5]Turbinado, an easy to use Model-View-Controller-ish web framework for Haskell. Highlights for the 0.4 release include a dramatically improved ORM which handles foreign keys, and improved documentation. Hackage about to reach 1000 releases. Don Stewart [6]announced that Hackage is about to reach the 1000 release mark, 2 years after it went live. Some pretty charts [7]can be seen here. leapseconds-announced-2009. Bjorn Buckwalter [8]announced the release of the [9]leapseconds-announced package, which contains a single module and a single function implementing the Data.Time.Clock.TAI.LeapSecondTable interface. zipper-0.1. Andres Loeh [10]announced [11]zipper-0.1, a library offering a generic zipper for systems of recursive datatypes. multirec-0.2. Andres Loeh [12]announced [13]multirec-0.2, a library which provides a mechanism to talk about fixed points of systems of datatypes that may be mutually recursive. On top of these representations, generic functions such as the fold or the Zipper can then be defined. ghci-haskeline 0.1. Judah Jacobson [14]announced the first release of [15]ghci-haskeline. This package uses the GHC API to reimplement ghci with the [16]Haskeline library as a backend. Haskeline is a library for line input in command-line programs, similar to readline or editline, which is written in Haskell and thus (hopefully) more easily integrated into other Haskell programs. The Monad.Reader (13) - Call for copy. Wouter Swierstra [17]announced a Call for Copy for Issue 13 of [18]The Monad.Reader. The submission deadline is February 13, 2009. Please get in touch with Wouter if you intend to submit something. Cabal 2.0. Duncan Coutts [19]announced that he has started a [20]wiki page to collect ideas for Cabal 2. The basic idea for Cabal 2 is to learn lessons from our how the existing design has fared and how we can make a better design to tackle an expanded set of goals. Announcing Haskell protocol-buffers 1.4.0 (the smashing recursive edition). Chris Kuklewicz [21]announced version 1.4.0 (the smashing recursive edition) of [22]protocol-buffers, a Haskell interface to Google's "..language-neutral, platform-neutral, extensible way of serializing structured data for use in communications protocols, data storage, and more." Haskell WikiProject. Robin Green [23]asked: is anyone else interested in forming a Haskell WikiProject on Wikipedia, to collaborate on improving and maintaining the coverage and quality of articles on Haskell-related software and topics (broadly defined)? darcs 2.2.0. Petr Rockai [24]announced the release of darcs 2.2.0, with both a [25]source tarball and a [26]cabalized tarball available. This version features many improvements and bug fixes; see Petr's original announcement for a list. hledger 0.3. Simon Michael [27]announced the release of [28]hledger 0.3, a partial haskell clone of John Wiegley's "ledger" text-based accounting tool. It generates transaction and balance reports from a plain text ledger file, and demonstrates a functional implementation of ledger. language-sh-0.0.3.1. Stephen Hicks [29]announced the [30]language-sh package, a set of modules for parsing, manipulating, and printing sh-style shell scripts. It's being developed alongside shsh, the [31]Simple Haskell Shell. Coadjute 0.0.1, generic build tool. Matti Niemenmaa [32]announced version 0.0.1 of [33]Coadjute, a generic build tool intended as an easier to use and more portable replacement for make. dataenc 0.12. Magnus Therning [34]announced version 0.12 of [35]dataenc, a data encoding library currently providing Uuencode, Base64, Base64Url, Base32, Base32Hex, Base16, Base85, and (new in 0.12) yEncoding. 3 applications of "indexed composition" as a language design principle. Greg Meredith [36]announced that he has found a way to generalize the LogicT transformer, and calculated it's [37]application to three fairly interesting examples. HTTPbis / HTTP-4000.x package available. Sigbjorn Finne [38]announced the availability of a modernization of the venerable and trusted [39]HTTP package. The headline new feature of this version is the parametrization of the representation of payloads in both HTTP requests and responses; two new representations are supported, strict and lazy ByteStrings. monad-interleave 0.1. Patrick Perry [40]announced the [41]monad-interleave package, which provides a type class generalizing his two favorite functions in Haskell, "unsafeInterleaveIO" and "unsafeInterleaveST". hs-dotnet, version 0.3.0. Sigbjorn Finne [42]announced the [43]first public release of [44]hs-dotnet, a pragmatic take on interoperating between Haskell (via GHC) and .NET. HEADS UP: finalizer changes coming in GHC 6.10.2. Simon Marlow [45]announced that, by popular demand, GHC 6.10.2 will support finalizers that are actually guaranteed to run, and run promptly. However, there's a catch. If you want to know what the catch is, read his message. split-0.1.1 (doc bugfix; new functions wordsBy and linesBy). Brent Yorgey [46]announced version 0.1.1 of the [47]split library. This version fixes some Haddock bugs, and adds two new convenience functions suggested by Neil Mitchell, wordsBy and linesBy. json-0.4.1. Sigbjorn Finne [48]announced a new release (0.4.1) of the [49]json package. New in this release is a generic JSON encoder contributed by Lennart Augustsson along with a number of other, smaller changes. haskell-platform mailing list. Duncan Coutts [50]announced that anyone interested in helping out with the haskell platform project is invited to subscribe to the [51]haskell-platform mailing list. This mailing list is for discussing practical stuff; policy questions will be discussed on the libraries mailing list. bytestring-trie 0.1.4. wren ng thornton [52]announced version 0.1.4 of the [53]bytestring-trie package. This release fixes a number of bugs, adds functions such as keys, toListBy, fromList{L,R,S}, and separated Data.Trie (the main module for users) from Data.Trie.Internal (gritty details, and core implementation). HLint 1.2. Neil Mitchell [54]announced [55]HLint version 1.2, a lint-like tool for Haskell that detects and suggests improvements for your code. The biggest new feature is list recursion suggestions. Working with HLint from Emacs. Alex Ott [56]announced an [57]emacs module for integration with [58]HLint. Discussion An Alternative Data.List.Zipper. Jeff Wheeler [59]posted [60]an improved version of Data.List.Zipper, and requested feedback or constructive criticism. Comments from OCaml Hacker Brian Hurt. John Goerzen [61]posted a link to a [62]blog post by Brian Hurt, along with some thoughts about naming things in the standard libraries, spawning the longest ML thread in recent history. Blog noise [63]Haskell news from the [64]blogosphere. * Jeff Heard: [65]The Docuverse.. Cool search query visualization for massive numbers of documents. * Ben Moseley: [66]The Category Theory of Appendages. * Galois, Inc: [67]Galois at POPL. * Colin Ross: [68]Does your IDE define you or support you?. * Alson Kemp: [69]ANNOUNCE: Turbinado V0.4. * Jeff Heard: [70]ProteinVis: Visualizing a large tree in Haskell and OpenGL. * ezekiel smithburg: [71]what to do when you can't solve a problem with a hackage library you need?. * Jeff Heard: [72]Simple Futures in Haskell. * Dan Piponi (sigfpe): [73]Haskell Monoids and their Uses. A nice introductory tutorial on Monoids in Haskell. * Real-World Haskell: [74]John Goerzen on Why You Should Learn Haskell. * LHC Team: [75]LLVM is great.. * Jeff Heard: [76]iBiblio traffic, search engine hits, and cross-traffic. * Luke Palmer: [77]Use MonadRandom!. * LHC Team: [78]Why LLVM probably won't replace C--.. * Magnus Therning: [79]Series of posts on testing Haskell code. * Magnus Therning: [80]Useful thing when adopting test-framework after already using HUnit. * Magnus Therning: [81]dataenc 0.12 posted to HackageDB. * Jeff Heard: [82]The new HTTP library. * Jeff Heard: [83]Beautiful Code, Compelling Evidence. * LHC Team: [84]The case against C/LLVM.. * Manuel M T Chakravarty: [85]Some nice code examples showing how to use type families.. * Manuel M T Chakravarty: [86]Enforcing a relation between independent type families.. * Nick Mudge: [87]Zunes, Year 2038 Problem, Real World Haskell, Why, Potion, Games. * Darcs: [88]darcs 2.2.0 is released!. * GHC / OpenSPARC Project: [89]Info tables. * LHC Team: [90]What is LHC?. * LHC Team: [91]Resources.. * LHC Team: [92]Typeclass Blues. * GHC / OpenSPARC Project: [93]Liveness lies. * Galois, Inc: [94]Real World Haskell: Intel Parallel Programming Podcast. * Real-World Haskell: [95]Intel Parallel Programming Podcast: Real World Haskell. * Brent Yorgey: [96]Abstraction, intuition, and the "monad tutorial fallacy". * Luke Palmer: [97]Ha! I can't even get Events right. * GHC / OpenSPARC Project: [98]Bootstrapping 7. * Colin Ross: [99]Finding a member of an infinite list. * LHC Team: [100]The mess with variable ids.. * Luke Palmer: [101]Ridding ourselves of IO before there is a good replacement. * GHC / OpenSPARC Project: [102]Bootstrapping 7. * Colin Ross: [103]Notes on working with finite sorted lists. * Bryan O'Sullivan: [104]Fun with Haskell view patterns. * Conal Elliott: [105]3D rendering as functional reactive programming. Quotes of the Week * luqui: sigh: mathematicians. can't live with 'em, can't prove 'em wrong. * mauke: YO DAWG I HEARD YOU LIKE METACIRCULARITY SO WE PUT AN INTERPRETER IN YOUR INTERPRETER SO YOU CAN RUN CODE WHILE YOU RUN CODE * lament: tuples are proof that haskell is inherently broken and will never work. * roconnor: [after a long -cafe thread on the suckiness of using math terms in Haskell] we don't use Integer anymore. Too abstract. It is now called CountingThingy. * quicksilver: partially applied type synonym = type lambdas = unrestricted type functions = can of pants * ddarius: In the spirit of that article on monoids, we should drop the term "tree" and replace it with the term "free pointed magma" * ski_: unique among types, 'Void -> X' has its own charm. tourists should definitely pay a visit. * pao: Cale: thanks ... I really think you deserve a statue ... or, at least, a portrait in ascii art on haskell.org :-) * byorgey: TDD replaces a type checker in Ruby in the same way that a strong drink replaces sorrows. About the Haskell Weekly News New editions are posted to [106]the Haskell mailing list as well as to [107]the Haskell Sequence and [108]Planet Haskell. [109]RSS is also available, and headlines appear on [110]haskell.org. To help create new editions of this newsletter, please see the information on [111]how to contribute. Send stories to byorgey at cis dot upenn dot edu. The darcs repository is available at darcs get [112]http://code.haskell.org/~byorgey/code/hwn/ . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.general/16792 3. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/curl 4. http://article.gmane.org/gmane.comp.lang.haskell.general/16788 5. http://www.turbinado.com/ 6. http://article.gmane.org/gmane.comp.lang.haskell.general/16782 7. http://archhaskell.wordpress.com/2009/01/18/open-source-haskell-releases-an… 8. http://article.gmane.org/gmane.comp.lang.haskell.general/16770 9. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/leapseconds-anno… 10. http://article.gmane.org/gmane.comp.lang.haskell.general/16756 11. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/zipper 12. http://www.haskell.org//pipermail/haskell/2009-January/020925.html 13. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/multirec 14. http://article.gmane.org/gmane.comp.lang.haskell.general/16751 15. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/ghci-haskeline 16. http://trac.haskell.org/haskeline 17. http://article.gmane.org/gmane.comp.lang.haskell.general/16750 18. http://www.haskell.org/haskellwiki/The_Monad.Reader 19. http://article.gmane.org/gmane.comp.lang.haskell.libraries/10568 20. http://hackage.haskell.org/trac/hackage/wiki/Cabal-2 21. http://article.gmane.org/gmane.comp.lang.haskell.libraries/10497 22. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/protocol-buffers 23. http://article.gmane.org/gmane.comp.lang.haskell.cafe/51037 24. http://www.haskell.org//pipermail/haskell-cafe/2009-January/053732.html 25. http://www.darcs.net/darcs-2.2.0.tar.gz 26. http://hackage.haskell.org/packages/archive/darcs/2.2.0/darcs-2.2.0.tar.gz 27. http://www.haskell.org//pipermail/haskell-cafe/2009-January/053843.html 28. http://joyful.com/hledger 29. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50907 30. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/language-sh 31. http://code.haskell.org/shsh/ 32. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50896 33. http://iki.fi/matti.niemenmaa/coadjute/ 34. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50831 35. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/dataenc 36. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50756 37. http://biosimilarity.blogspot.com/2009/01/3-applications-of-indexed-composi… 38. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50748 39. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HTTP 40. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50648 41. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/monad-interleave 42. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50548 43. http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hs-dotnet 44. http://haskell.forkIO.com/dotnet 45. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50477 46. http://article.gmane.org/gmane.comp.lang.haskell.cafe/50421 47. 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http://planet.haskell.org/ 64. http://haskell.org/haskellwiki/Blog_articles 65. http://vis.renci.org/jeff/?p=66 66. http://nattermorphisms.blogspot.com/2009/01/category-theory-of-appendages.h… 67. http://www.galois.com/blog/2009/01/18/galois-at-popl/ 68. http://vcolin.com/2009/01/18/ide-define-support/ 69. http://www.alsonkemp.com/haskell/announce-turbinado-v04/ 70. http://vis.renci.org/jeff/?p=52 71. http://tehgeekmeister.wordpress.com/2009/01/17/what-to-do-when-you-cant-sol… 72. http://vis.renci.org/jeff/?p=27 73. http://sigfpe.blogspot.com/2009/01/haskell-monoids-and-their-uses.html 74. http://www.realworldhaskell.org/blog/2009/01/17/john-goerzen-on-why-you-sho… 75. http://lhc-compiler.blogspot.com/2009/01/llvm-is-great.html 76. http://vis.renci.org/jeff/?p=33 77. http://lukepalmer.wordpress.com/2009/01/17/use-monadrandom/ 78. http://lhc-compiler.blogspot.com/2009/01/why-llvm-probably-wont-replace-c.h… 79. http://therning.org/magnus/archives/436 80. http://therning.org/magnus/archives/437 81. http://therning.org/magnus/archives/434 82. http://vis.renci.org/jeff/?p=8 83. http://vis.renci.org/jeff/?p=4 84. http://lhc-compiler.blogspot.com/2009/01/case-against-cllvm.html 85. http://justtesting.org/post/70895924 86. http://justtesting.org/post/70893530 87. http://nickmudge.info/?post=103 88. http://blog.darcs.net/2009/01/darcs-220-is-released.html 89. http://ghcsparc.blogspot.com/2009/01/info-tables.html 90. http://lhc-compiler.blogspot.com/2009/01/what-is-lhc.html 91. http://lhc-compiler.blogspot.com/2009/01/resources.html 92. http://lhc-compiler.blogspot.com/2009/01/typeclass-blues.html 93. http://ghcsparc.blogspot.com/2009/01/liveness-lies.html 94. http://www.galois.com/blog/2009/01/13/real-world-haskell-intel-parallel-pro… 95. http://www.realworldhaskell.org/blog/2009/01/13/intel-parallel-programming-… 96. http://byorgey.wordpress.com/2009/01/12/abstraction-intuition-and-the-monad… 97. http://lukepalmer.wordpress.com/2009/01/13/ha-i-cant-even-get-events-right/ 98. http://ghcsparc.blogspot.com/2009/01/bootstrapping-7.html 99. http://vcolin.com/2009/01/12/finding-member-infinite-list/ 100. http://lhc-compiler.blogspot.com/2009/01/mess-with-variable-ids.html 101. http://lukepalmer.wordpress.com/2009/01/12/ridding-ourselves-of-io-before-t… 102. http://ghcsparc.blogspot.com/2009/01/bootstrapping-7.html 103. http://vcolin.com/2009/01/11/notes-working-finite-sorted-lists/ 104. http://www.serpentine.com/blog/2009/01/11/fun-with-haskell-view-patterns/ 105. http://conal.net/blog/posts/3d-rendering-as-functional-reactive-programming/ 106. http://www.haskell.org/mailman/listinfo/haskell 107. http://sequence.complete.org/ 108. http://planet.haskell.org/ 109. http://sequence.complete.org/node/feed 110. http://haskell.org/ 111. http://haskell.org/haskellwiki/HWN 112. http://code.haskell.org/~byorgey/code/hwn/

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Haskell WikiProject
by Robin Green 19 Jan '09

19 Jan '09

Is anyone else interested in forming a Haskell WikiProject on Wikipedia, to collaborate on improving and maintaining the coverage and quality of articles on Haskell-related software and topics (broadly defined)? Not just programming topics specific to Haskell, but also ones of interest to the Haskell community. Some of you might already be doing this from time to time, but forming an explicit WikiProject might help to: * Highlight things that could use some attention * Divide up tasks (based on expertise or interest) * Recruit more editors (sticking a banner on article Talk pages can let editors know the WikiProject exists) * Eventually (something for the future, maybe!) work together on a Wikipedia Haskell Portal * And of course, improve the visibility of Haskell on Wikipedia, which should help our community Here's a good example to start with. The article on Eager evaluation could do with some improvement - and possibly should be merged into the Lazy evaluation article, I'm not sure: http://en.wikipedia.org/wiki/Eager_evaluation We could also probably create some more articles on projects written in Haskell, and add more references to Haskell research papers. Software projects don't have to be polished to be covered in Wikipedia - or even working! - they essentially just have to be "notable", as the Wikipedia guidelines define it. By the way (getting a bit offtopic here) an annoying limitation of the Wikipedia category system, that you couldn't run queries like "Give me all the articles in the Haskell category that are also in the Unreferenced category" has now been partially addressed by the experimental prototype of Category Intersection: http://toolserver.org/~dschwen/intersection/ This is slightly better than Googling, because crucially, it searches *recursively* through categories. That means it will turn up articles that are in a subcategory of "Category:Haskell programming language" but don't explicitly mention Haskell. Don't know if there any such articles yet, but it's worth bearing in mind that you can do this. I think it will, in principle, make topic-specific maintenance a bit more convenient - and it's what I've been waiting for before getting involved in topic-specific maintenance. If you want to just express interest in signing up for such a WikiProject (no commitment required whatsoever!), please reply privately via email or publicly on my User Talk page (User talk:Greenrd) - to avoid clogging up this mailing list. -- Robin

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Expect module?
by Erik de Castro Lopo 19 Jan '09

19 Jan '09

Hi all, Is there a Haskell-Expect module? Something that would allow me to control an external Unix program via its stdin/stdout/stderr? Cheers, Erik -- ----------------------------------------------------------------- Erik de Castro Lopo ----------------------------------------------------------------- Seen on comp.lang.c : klaushuot : C rocks the world. Plain and simple. It's the ultimate solution, period. user923005 : Every tool should be a screwdriver. You can hammer with it, if you pound hard enough. You can pry with it -- just like a crowbar. Or, perhaps, there are room for other tools in the bag.

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plugins can not be installed in ghc 6.10.1
by Alberto G. Corona 19 Jan '09

19 Jan '09

Do really pluigins needs Cabal (>=1.4 && <1.5) ??? C:\Documents and Settings\Administrator>cabal install plugins Resolving dependencies... cabal: dependencies conflict: ghc-6.10.1 requires Cabal ==1.6.0.1 however Cabal-1.6.0.1 was excluded because plugins-1.3.1 requires Cabal ==1.4.*

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ANN: hledger 0.3 released
by Simon Michael 19 Jan '09

19 Jan '09

I'm pleased to announce another hledger release. Happy new year, all! hledger is a partial haskell clone of John Wiegley's "ledger" text-based accounting tool. It generates transaction & balance reports from a plain text ledger file, and demonstrates a functional implementation of ledger. For more information, see hledger's home page: http://joyful.com/hledger News for 0.3 ------------ Fixes: * count timelog sessions on the day they end, like ledger, for now * when options are repeated, use the last instead of the first * builds with ghc 6.10 as well as 6.8 * runs much faster than 0.2:: $ bench hledger-0.2 hledger ledger || hledger-0.2 | hledger | ledger ==================================++=============+=========+======= -f 2008.ledger -s balance || 2.59 | 0.26 | 0.11 -f 10000entries.ledger -s balance || 566.68 | 2.72 | 0.96 Features: * a simple ui for interactive report browsing: hledger ui * accept smart dates everywhere (YYYYMMDD, Y/M/D, Y, M/D, D, jan, today, last week etc.) * --period/-p flag accepting period expressions like "in 2008", "weekly from last month".. * -W/-M/-Y convenience flags to summarise register weekly, monthly, yearly * --depth and -E flags also affect summarised register reports (including depth=0) * --display/-d flag supporting date predicates (like "d<[DATE]", "d>=[DATE]") * !include directive to include additional ledger files * !account directive to set a default parent account * Added support for reading historical prices from files * timelog and ledger entries can be intermixed in one file * modifier and periodic entries can appear anywhere (but are still ignored) * help and readme improvements Contributors: * Simon Michael * Nick Ingolia * Tim Docker * Corey O'Connor & the vty team Stats: * Known errors: 1 * Tests: 58 * Lines of non-test code: 2123 Installation ------------ hledger requires GHC. It is known to build with 6.8 and 6.10. If you have cabal-install, do:: cabal update cabal install hledger Otherwise, unpack the latest tarball from http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hledger and do:: runhaskell Setup.hs configure runhaskell Setup.hs build sudo runhaskell Setup.hs install This will complain about any missing libraries, which you can download and install manually from hackage.haskell.org. (The Build-Depends: in hledger.cabal has the full package list.) To get the latest development code do:: darcs get http://joyful.com/repos/hledger

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