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Is there good place to post Haskell alorithms/data structures that follow Steven Skiena's book on algorithm design and also Haskell code snippets that follow some of Knuth's books?
by Casey Hawthorne 22 Jun '10

22 Jun '10

Is there good place to post Haskell alorithms/data structures that follow Steven Skiena's book on algorithm design and also Haskell code snippets that follow some of Knuth's books? These code snippets don't seem to fit with Hackage. Is there a Hatorial? -- Regards, Casey

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Ph.D. positions on HW acceleration of Haskell
by Rami Mukhtar 22 Jun '10

22 Jun '10

========================================================================= Vacancies for Ph.D. positions at NICTA with the University of Sydney, Australia ========================================================================= Background ~~~~~~~~~~ NICTA has established a project with a goal of developing technology to map high level descriptions of computer vision algorithms to heterogeneous parallel hardware architectures. NICTA scholarships are available at the University of Sydney for outstanding students in the areas listed below. For further information, please contact either: Dr Rami Mukhtar (rami.mukhtar _AT_ nicta.com.au) or Dr Philip Leong (philip.leong _AT_ sydney.edu.au). Further information concerning these scholarships is available from: http://www.nicta.com.au/education/scholarships/sydney_research_lab/scholars… Reconfigurable Computing Architectures for Acceleration of Functional Languages ---------------------------------------------------------------------- This project would provide a candidate with the opportunity to develop new reconfigurable computing hardware architectures that are well suited for accelerating computations on collections of data. The work would be driven by recent advances on computations of collections made in the functional language community. The outcomes of this research would be to develop new hardware accelerator architectures, supporting tools chains, and undertake performance analysis. The candidate would be part of a larger team working to develop a technology for mapping computer vision algorithms to heterogeneous parallel hardware architectures. Hardware Acceleration of Functional Languages --------------------------------------------- This project would provide a candidate with the opportunity to develop new methods for mapping functional languages to implementations that target hardware accelerators, including FPGAs and other reconfigurable computing architectures. The outcomes of this research would be to develop algorithms, methodologies and related software frameworks that make this possible. The candidate would be part of a larger team working to develop a technology for mapping computer vision algorithms to heterogeneous parallel hardware architectures. The information in this e-mail may be confidential and subject to legal professional privilege and/or copyright. National ICT Australia Limited accepts no liability for any damage caused by this email or its attachments.

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Functional programming techniques in small projects
by Markus Dönges 22 Jun '10

22 Jun '10

Hello Community, I am a student from the University of Duisburg-Essen, Germany, and at the moment I am writing my bachelor thesis about "Post-Mass-Prodcution Softwaresupply/ -development in case of an University administration". This approach deals with student-driven software development in which functional programming techniques (ie, Haskell) and agile development approaches matter. I am looking for opinions and statements on how small (agile) software development projects may benefit from functional programming techniques (perhaps in contrast to imperative programming techniques). Since I am at the very start, I would appreciate further literature advices. In addition, does anybody know particular people who are familiar with this topic? Any answer is appreciated :-) Regards, Markus

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Generics and type families
by Louis Wasserman 21 Jun '10

21 Jun '10

What is the relationship between -XGenerics and -XTypeFamilies? Can I automatically create a data family instance based on its generic decomposition? Louis Wasserman wasserman.louis(a)gmail.com http://profiles.google.com/wasserman.louis

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HaskellWiki and Wikipedia
by Roman Beslik 21 Jun '10

21 Jun '10

Hi all. There are some notions which are not described in HaskellWiki but described in Wikipedia, e.g. "catamorphism". When clicking on a link [[catamorphism]] that leads to "create a new page" it would be nice to show link to a corresponding Wikipedia page. Also "search in Wikipedia" on the search results page. -- Best regards, Roman Beslik.

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new recursive do notation (ghc 6.12.x) spoils layout
by John Lask 21 Jun '10

21 Jun '10

Whilst I have nothing against the change in syntax for recursive do aka http://old.nabble.com/Update-on-GHC-6.12.1-td26103595.html Instead of writing mdo a <- getChar b <- f c c <- g b putChar c return b you would write do a <- getChar rec { b <- f c ; c <- g b } putChar c return b it does spoil the nice layout - it would be nice to just be able to write (which does not parse) do rec a <- getChar b <- f c c <- g b putChar c return b I don't particularly care that the only recursive statements are #2,#3 - I just want my nice neat layout back. I have just spent an inordinate amount of time updating code when if the parser recognised "do rec" as a recursive group it would have been a drop in replacement and taken me one tenth of the time. Why can't we have this?

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Re: Installing Haskell on OSX
by Giuseppe Luigi Punzi 21 Jun '10

21 Jun '10

I died in more dependencies. One, ige-mac-integration. To avoid possible problems I uninstall all ports last night to reinstall full gtk2 with quartz. For now, i'm solving all of this and I hope to get it working this night. Sudish Joseph <sudish(a)gmail.com> wrote: >Antoine Latter <aslatter(a)gmail.com> writes: >> On Sun, Jun 20, 2010 at 12:53 PM, Giuseppe Luigi Punzi Ruiz >> <glpunzi(a)lordzealon.com> wrote: >>> Hi again, >>> >>> Yes, you are right, but now, "cabal install leksah" I get: >>> > >[...] > >>> Undefined symbols: >>> "_iconv_close", referenced from: >>> _hs_iconv_close in libHSbase-4.2.0.0.a(iconv.o) >>> "_iconv_open", referenced from: >>> _hs_iconv_open in libHSbase-4.2.0.0.a(iconv.o) >>> "_iconv", referenced from: >>> _hs_iconv in libHSbase-4.2.0.0.a(iconv.o) >>> ld: symbol(s) not found > >> This one is a bummer, and I see it all the time when I try to build a >> package linked against macports. > >This is caused by the two libiconv's in the system being >ABI-incompatible, sadly. The ghc pkg available for download from >haskell.org is linked against the system /usr/lib/libiconv.dynlib, which >has iconv_open() as a function. Macports has GNU libiconv which >#defines iconv_open to libiconv_open() in /opt/local/include/iconv.h. > >This then blows up as above when linking against other libraries in >macports - the linker pulls in GNU libiconv which lacks the symbols >needed as you see above. > >One workaround is to link GHC itself against the macports version of >libiconv (and libgmp) and have cabal-install link all subsequent >libraries against macports. I did just that this weekend and now have a >working threadscope using the Quartz backend for gtk2, which is very >nice (no need to run the X server). > >Recipe for reproducing this build is included below (and I can also >provide the resulting ghc-6.12.3 pkg file if needed). > >Another possible option is to use Homebrew to install gtk2 and other >dependencies. Homebrew prefers to use the system-provided libraries and >will not pull in GNU libiconv, so this should work with the existing GHC >pkg in theory. I didn't pursue this since the homebrew 'gtk+' package >didn't seem to have the option to use Quartz instead of X11 as its >backend. > >Steps for linking the ghc runtime against macports: > >- Specify EXTRA_CABAL_CONFIGURE_FLAGS in mk/build.mk as mentioned at > the bottom of http://www.haskell.org/ghc/download_ghc_6_12_3.html > > EXTRA_CABAL_CONFIGURE_FLAGS = --extra-include-dirs=/opt/local/include \ > --extra-lib-dirs=/opt/local/lib > >- Use the --with-iconv-* and --with-gmp-* flags when configuring ghc. > > ./configure --with-iconv-includes=/opt/local/include \ > --with-iconv-libraries=/opt/local/lib \ > --with-gmp-includes=/opt/local/include \ > --with-gmp-libraries=/opt/local/lib > >- This produces a GHC runtime and libraries linked against macports: > > % otool -L ghc > ghc: > /opt/local/lib/libncurses.5.dylib (compatibility version 5.0.0, current version 5.0.0) > /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.0) > /opt/local/lib/libiconv.2.dylib (compatibility version 8.0.0, current version 8.0.0) > /opt/local/lib/libgmp.10.dylib (compatibility version 11.0.0, current version 11.1.0) > > % nm HSbase-4.2.0.2.o | fgrep iconv > 001ff7f0 T _hs_iconv > 001ff7e0 T _hs_iconv_close > 001ff800 T _hs_iconv_open > U _libiconv > U _libiconv_close > U _libiconv_open > > ghc and included libraries use the macports libiconv, so linking > against other libraries in macports (gtk2!) will work. > >- Have cabal-install use macports as well for packages it installs by > editing ~/.cabal/config and setting: > > extra-include-dirs: /opt/local/include > extra-lib-dirs: /opt/local/lib > >- This gives, for e.g., threadscope linked against macports: > > % otool -L ~/.cabal/bin/threadscope | egrep '(gtk|iconv)' > /opt/local/lib/libgtk-quartz-2.0.0.dylib (compatibility version 2001.0.0, current version 2001.1.0) > /opt/local/lib/libiconv.2.dylib (compatibility version 8.0.0, current version 8.0.0) > >- Note that since the ghc runtime is still in 32-bit i386 mode, we > need universal versions of most libraries in macports. Recent > versions of macports (1.9 for sure, maybe 1.8) make it simple to > switch from an x86_64 library to a universal one: > > % port install gtk2 +universal > > This will recompile gtk2 and *all* dependent libraries as universal > libraries which is exactly what you need. You can then eliminate any > inactive 64-bit libraries with: > > % port -f uninstall inactive > >> Here's the last thread about with, with more links and discussion: >> >> http://thread.gmane.org/gmane.comp.lang.haskell.general/18064/ >> >> The response by Jean-Marie Gaillourdet has worked for me in the past. >> >> Antoine > >Thanks for that link, I didn't think of overriding libiconv on a >per-package basis. > >-Sudish

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How to browse code written by others
by Martin Drautzburg 21 Jun '10

21 Jun '10

Hello all, I need your advice about how to browse code which was written by someone else (Paul Hudak's Euterpea, to be precise, apx. 10000 LOC). I had set some hopes on leksah, and it indeed shows me the interfaces, but I have not yet convinced it to show me more than that. I ran haddock over the sources, and again I could not see more that just signatures. I would be very happy with something like a Smalltalk browser. Something that would let me zoom down to the source code, but with "search" and hyperlink capabilities ("senders" and "implementers" in Smalltalk). Anyways, how do you guys do it, i.e. how to you dive into non-trivial foreign code? -- Martin

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MonadCatchIO-transformers and ContT
by Michael Snoyman 21 Jun '10

21 Jun '10

Hi cafe, I ran into a segfault while working on some database code. I eventually traced it back to a double-finalizing of a statement (read: freeing memory twice), which ultimately led back to switching my code to use the ContT monad transformer. I was able to isolate this down to a minimal test case (catch.hs); when run, it prints the line "released" twice. In an attempt to understand what's going on, I rewrote the code to avoid the libraries entirely (catch-simplified.hs); it didn't give me any insight into the problem, but maybe it will help someone else. If someone sees an obvious mistake I'm making in my usage of the bracket_ function, please let me know. Otherwise, I'd really like to get a fix for this so I can use this library. Thanks, Michael

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installation problem with cabal
by Louis Plissonneau 21 Jun '10

21 Jun '10

Hi, when I install packages from cabal, the package manager installs already installed files (some of his favorites are process and haskell98) so these packages are both system and user installed (that can cause later dependency problems, but the cabal FAQ explains very well how to recover from it) but the funniest is that if I reinstall it, it again reinstall the same packages even they are already twice installed does anyone know how to solve this issue? Thanks Louis

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