October 2007 - Haskell-Cafe

XML parser recommendation?
by Ketil Malde 24 Oct '07

24 Oct '07

Hi, I'm struggling to get my HXT-based parser to parse a largish file (<300MB), even after breaking into reasonably-sized chunks. The culprit appears to be parsing one element comprising 25K lines of text, which apparently requires more memory than the 2Gb my computer is equipped with. I'm wondering what approach others use for non-toy XML data. Is the problem due to some error I have made, or should I just ignore the XML, and just parse it "manually" by dissecting bytestrings, or will another XML library serve better? -k -- If I haven't seen further, it is by standing in the footprints of giants

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Haskell Report??
by Galchin Vasili 24 Oct '07

24 Oct '07

Hello, I am trying to use a Haskell shell (Hsh.hs). I am a little frustrated. There are two modules that are imported: import LibPosix import LibSystem I am running WinHugs (Windows) and hugs/ghci can't find LibSystem. I am confused about 1) what are currently standard libraries, etc. in Haskell, 2) what is deprecated and 3) what are "home grown tomatoes" ;^) How current and definitive is the Haskell Report? Kind regards, Bill Halchin

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ANNOUNCE: dataenc 0.9
by Magnus Therning 24 Oct '07

24 Oct '07

My collection of data encoding functions are now available at http://hackage.haskell.org/cgi-bin/hackage-scripts/package/dataenc-0.9: Dependencies base License LGPL Copyright Magnus Therning, 2007 Author Magnus Therning Maintainer magnus(a)therning.org Exposed modules Codec.Binary.DataEncoding, Codec.Binary.Base16, Codec.Binary.Base32Hex, Codec.Binary.Base32, Codec.Binary.Uu, Codec.Binary.Base64Url, Codec.Binary.Base64 There's a short description of the library on the wiki: http://haskell.org/haskellwiki/Library/Data_encoding The source darcs repo is available on code.haskell.org. Hopefully the haddockuments will be generated on hackage soon-ish. /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus

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Re: [Haskell-cafe] will the real quicksort please stand up? (or: sorting a > million element list)
by Brent Yorgey 24 Oct '07

24 Oct '07

On 10/23/07, Thomas Hartman <thomas.hartman(a)db.com> wrote: > > > Actually I can't compile it, with or without -O2. loads fine into ghci, > but when I try to create an executable I get > > ghc quicksort.hs -o quicksort > quicksort.o: In function `r1Nc_info': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_vector_closure' > quicksort.o: In function `r1Nc_info': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_zdf16_closure' > quicksort.o: In function `s1Ws_info': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_generate_closure' > quicksort.o: In function `r1Nc_srt': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_vector_closure' > quicksort.o: In function `r1Nc_srt': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_zdf16_closure' > quicksort.o: In function `rzC_srt': undefined reference to > `QuickCheckzm1zi0zi1_TestziQuickCheck_generate_closure' > collect2: ld returned 1 exit status hmm, try adding --make to the ghc command line? Unfortunately, GHC doesn't automatically chase down dependencies for linking; you must specify them explicitly with -package, or tell it to auto-chase dependencies with --make. -Brent

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Job: web development in Haskell
by red nucleus 24 Oct '07

24 Oct '07

Anyone who is serious about doing web development in Haskell is welcome to apply for the job outlined below. If we found a good functional programmer, we can ignore the bits about Rails. Web Developer RedNucleus Ltd (rednucleus.co.uk) is seeking a highly motivated programmer for a full or part-time posititon developing social web applications. Initially you will develop and maintain applications using RubyOnRails or a similar framework, but there will be opportunities to explore new web programming paradigms with declarative languages. The successful application will have: -a good degree in computer science or a quantitative topic. -good independent programming and quantitative analysis skills. -some familiarity with HTML, CSS, JavaScript and SQL, and with network programming. -exposure to functional programming methodologies, e.g. in Haskell, Lisp or Erlang. Graduate level qualifications in computer science and expertise in web development including RubyOnRails would be a plus. RedNucleus is based in Beeston, Nottingham. The successful application could work here or mostly from home. Salary depends on experience and qualifications, starting from £22,000 plus performance bonus. To apply, please prepare a single pdf file containing your cover letter and CV, and name the file with your surname, e.g. smith.pdf. Then send the file to: rednucleusltd(a)gmail.com. Informal enquiries can be directed to the same address. The closing date for applications is 22nd November 2007

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ANN: new version of matrix library (GSLHaskell)
by Alberto Ruiz 24 Oct '07

24 Oct '07

Dear Haskellers, I am happy to announce a new version of GSLHaskell, a basic library for matrix computations and other numeric algorithms based on LAPACK, BLAS and GSL. The goal is that simple problems involving singular values, linear systems, etc, can be easily solved using Haskell. The library is horribly incomplete, I don't recommend it for any serious work. But at least I enjoy using it in my projects... Some features of this release are: * Improved internal implementation, most code has been refactored. * It works on Linux, Windows, and MacOS X (see the README of the distribution). * Automatic bindings to 200+ GSL special functions. Source code, documentation, updated tutorial, and more information is available from: http://dis.um.es/~alberto/GSLHaskell I'd like to upload a decent version to hackage, so any kind of feedback is very welcome! Thanks, Alberto

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A possibly stupid doubt about the GHC's overlapping instances flag's
by Rodrigo Geraldo 24 Oct '07

24 Oct '07

Hi! Suppose that the GHC's flag -fallow-incoherent-instances is enabled. In this situation, when a instance will be rejected? And if the flag -fallow-overlapping-instances is enabled. When a instance will be rejected? Thanks! Rodrigo

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string literals and haskell'
by David Roundy 23 Oct '07

23 Oct '07

I've just been annoyed with errors ghc reports when I use a string literal such as ":\/:" (which is a contructor in darcs). Of course, it wants ":\\/:", but I'd rather type the former. Is there any reason why the language couldn't be modified (e.g. in haskell') to make the former legal? i.e. to treat string literals with '\\' followed by a character that doesn't describe an escape as a literal backslash? It makes the rules a bit more complicated, but doesn't modify the meaning of any currently-legal code, and removes a potential error. -- David Roundy Department of Physics Oregon State University

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OS Abstraction module??
by Galchin Vasili 23 Oct '07

23 Oct '07

Hello, In the Haskell libraries, is there an OS abstraction module, that would "hide" the POSIX API and Win-32 API? If not, this would be nice so that Haskell "programs" could be written in an OS independent manner! Kind regards, Bill Halchin

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Using Haddock to document ADTs
by Alfonso Acosta 23 Oct '07

23 Oct '07

Hi all, I'm beginning to get familiar with Haddock and I want to document a library which, as usually happens, has some ADT definitions. I'd like to document the ADTs both for the end-user (who shouldn't be told about its internal implementation) and future developers. Let's imagine my library is called FooLib, defines an ADT whose implementation is hidden by an outer module. =========== FooLib/ADT1.hs ===== -- | This module defines my type ADT1 module ADT1 -- | This type implements whatever and. As you can see it's implemented -- using blah blah so that is more efficient because of blah blah data ADT1 a = ... ========== Foolib.hs ============ -- | This is Foolib which is aimed at whatever module Foolib (ADT) where import ADT =================== Generating documentation for Foolib.hs with this Haddock annotations will unfortunatelly reveal implementation details since the annotation of ADT1 is forwarded. My question is, How can I generate documentation for both developers and the end-users using the same Haddock annotations? I'm beginning to think it would be a good idea to distinguish those two cases (documentation for end-users and internal developers) in Haddock, but I'm probably wrong since it seems a common thing and wasn't implemented yet. Best Regards, Alfonso

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