August 2008 - Haskell-Cafe

ICFP08 Call for Participation
by Matthew Fluet (ICFP Publicity Chair) 04 Aug '08

04 Aug '08

===================================================================== Call for Participation The 13th ACM SIGPLAN International Conference on Functional Programming (ICFP 2008) http://www.icfpconference.org/icfp2008 Victoria, BC, Canada, 22-24 September 2008 ===================================================================== ICFP 2008 provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. Preliminary program: * http://www.icfpconference.org/icfp2008/schedule.html * Invited speakers: + Butler Lampson, Microsoft Research; Lazy and Speculative Execution in Computer Systems + Olivier Danvy, University of Aarhus; Defunctionalized Interpreters for Higher-Order Languages + Mark Jones, Portland State University; Polymorphism and Page Tables -- Systems Programming From a Functional Programmer's Perspective Schedule including related workshops: * Sep 20: ACM SIGPLAN Workshop on Generic Programming * Sep 20: ACM SIGPLAN Workshop on Mechanizing Metatheory * Sep 20: ACM SIGPLAN Workshop on Scheme and Functional Programming * Sep 21: ACM SIGPLAN Workshop on ML * Sep 21: ACM SIGPLAN Functional and Declarative Programming in Education * Sep 22-24: ICFP08 * Sep 25: ACM SIGPLAN Haskell Symposium * Sep 25: Functional Programming Developer Tracks * Sep 26: Commercial Users of Functional Programming * Sep 27: ACM SIGPLAN Erlang Workshop * Sep 27: Functional Programming Developer Tracks Registration information: * http://www.regmaster.com/conf/icfp2008.html * Early registration deadline: August 20, 2008 Conference hotel accommodation information: * http://www.deltahotels.com/groups/online/VIC/acm.php * Conference rate deadline: August 18, 2008 * Wiki page to coordinate room-sharing: http://www.icfpconference.org/pmwiki/pmwiki.php?n=Main.ICFP08RoomShare Conference organizers: * General Chair: James Hook (Portland State University) * Program Chair: Peter Thiemann (Universität Freiburg) * Local Arrangements Chair: George Tzanetakis (University of Victoria) * Workshop Co-Chairs: Michael Sperber (DeinProgramm) and Graham Hutton (University of Nottingham) * Programming Contest Co-Chairs: John Reppy (University of Chicago) and Tim Sheard (Portland State University) * Publicity Chair: Matthew Fluet (Toyota Technological Institute at Chicago)

1 0

HDBC-ODBC linking problems in windows.
by PJ Durai 04 Aug '08

04 Aug '08

Greetings everyone, I am having issues getting hdbc/odbc working on windows. When using GHC, I am not able to compile a simple program. It ends up with linker errors like C:\Program Files\Haskell\HDBC-odbc-1.1.4.3\ghc-6.8.3/libHSHDBC-odbc-1.1.4.3.a(Connection.o)(.text+0x52c):fake: undefined reference to `SQLAllocHandle' C:\Program Files\Haskell\HDBC-odbc-1.1.4.3\ghc-6.8.3/libHSHDBC-odbc-1.1.4.3.a(Connection.o)(.text+0x5b8):fake: undefined reference to `SQLSetEnvAttr' C:\Program Files\Haskell\HDBC-odbc-1.1.4.3\ghc-6.8.3/libHSHDBC-odbc-1.1.4.3.a(Connection.o)(.text+0x62c):fake: undefined reference to `SQLDriverConnect' C:\Program Files\Haskell\HDBC-odbc-1.1.4.3\ghc-6.8.3/libHSHDBC-odbc-1.1.4.3.a(Connection.o)(.text+0x700):fake: undefined reference to `SQLEndTran' C:\Program Files\Haskell\HDBC-odbc-1.1.4.3\ghc-6.8.3/libHSHDBC-odbc-1.1.4.3.a(Connection.o)(.text+0x770):fake: undefined reference to `SQLGetInfo' C:\Program Files\Haskell\HDBC-odbc-1 When I use ghci, it exits silently. It looks like calling convension mix-up in FFI declarations to me. I ran 'dumpbin' on odbc32.lib and all the exported function names are decorated like they are PASCAL calls, not ccall's. But GHC in this case is looking for undecorated names. I assume it works as is on Unix (unixODBC) ? Is there an easy workaround for this? Or am I doing something wrong? MySetup ======= Windows XP SP2 ghc 6.8.3 hdbc 1.1.5.0 hdbc-odbc 1.1.4.3.0 appreciate your time. Thanks pj

3 3

your RSA code
by Galchin, Vasili 04 Aug '08

04 Aug '08

Hi John, I am reading your RSA code as suggested. 1) Do you have an example code that uses your RSA API? 2) a ForeignPtr is created in function createPkey and "returned" to the caller. I am trying to follow which function(s) GC the associated heap. ?? 3) My assertion: It seems in my Posix asynch IO case ... that functions like aioRead, aioWrite, lioListIO would create ForeignPtrs that would "carried around in the AIO application and the associated heap would only be GC'd (garbage collected) when aioReturn or aio_Cancel get called. True? Kind regards, Vasili

1 0

Re: [Haskell-cafe] question about "faulting in" Haskell packages ...
by david48 03 Aug '08

03 Aug '08

You need to get cabal-install. Here's how I got it working on kubuntu : 1) install GHC 6.8.3 from haskell.org's binaries (kubuntu hardy isn't at 6.8.3 yet....) 2) download from hackage : * cabal-install-0.5.1.tar.gz from hackage * HTTP-3001.0.4.tar.gz * zlib-0.4.0.4.tar.gz * Cabal-1.4.0.1.tar.gz 3) build and install http, zlib, Cabal and then cabal-install for each package you have to type (*) : runhaskell Setup.hs configure runhaskell Setup.hs build sudo runhaskell Setup.hs install (*) sometimes it'll be Setup.lhs, I'm annoyed that it's not always the same name, can't rely on shell history :( 4) once cabal-install is installed you can do cabal update sudo cabal upgrade --global that'll upgrade all your ghc's packages. 5) from now if you want to install package a just type cabal install a --global cabal should download packages b,c,d for you if required. P.S. Sorry for the previous email, it got sent before I finished it :)

4 3

Memory problems reading a IntMap from a binary file
by Ludger Steens 03 Aug '08

03 Aug '08

Hi, I have IntMap String with about 40,000 entries. After saving it to disk (via Data.Binary) the file is 3.5 Mb small. However if I load it and save it back again my program needs 180 MB memory. Is there anything I do wrong or does the map really need that much memory? The (simple) program I wrote: main = do mp <- decodeFile "i.bin" :: IO ( IntMap String ) encodeFile "i2.bin" mp exitWith ExitSuccess Thanks, Ludger

2 1

adjoint of coproduct & diagonal
by Jason Dusek 03 Aug '08

03 Aug '08

I'm trying to figure out the adjunction diagrams for the adjunction where the diagonal functor is right adjoint to the coproduct functor. I'm |almost done|, but the co-unit has me stumped, because I can't figure out how the arrow at the top can be unique -- it seems it could be either one of: i_1 . [f,g] i_2 . [f,g] i_1, i_2 : C -> C+C f : A -> C g : B -> C The net effect of [id,id] on the right is to blur out the distinction. On #haskell, someone suggested there is a constraint I am missing; I've poked around for a day and still can't figure it out. -- _jsn |almost done| http://hpaste.org/9303

3 13

Kleisli composition operator
by Roly Perera 03 Aug '08

03 Aug '08

Hi, I'm obviously missing something basic here but I don't seem to be able to use the >=> operator which is apparently defined in the Prelude and also in Control.Monad. My imports are: import Prelude hiding (abs, lookup, init) import Data.Maybe import Data.List as List hiding (lookup, insert, delete, union, init) import Data.Map as Map hiding (update, delete, union, null, findIndex) import qualified Data.Tree as Tree import Control.Monad import Control.Monad.State Any suggestions anyone? thanks, Roly Perera

3 5

Re: [darcs-users] [Haskell-cafe] Re: poll: how can we help you contribute to darcs?
by Ashley Moran 03 Aug '08

03 Aug '08

On Aug 03, 2008, at 12:53 pm, Lele Gaifax wrote: > I fail to see what's so cool with GitHub: a quick overview didn't > reveal anything that couldn't be done with, say, Trac+Darcs. Can you > elaborate on that? Hi Lele It probably doesn't do anything you couldn't in Trac+darcs. But that's not the point - it's easy to jump on there, and fork a repo, track the changes in both directions. The barrier to working on a project on there is virtually nil (there is, of course, the issue of figuring out git when you've got the source on your machine, but that's a separate issue). What GitHub does really well is build a community around the repos. They could have used Hg or bzr or pretty much and DVCS and been as successful, but they (unfortunately) chose git. > IMHO, the biggest problem with darcs is with its underdocumented (from > the technical point of view) code base, that only an handful of people > understand. As already stated, I doubt Haskell is the real culprit > here: the algorithms are effectively difficult to explain in any > language, English to starts with. I wish David used a less succint > coding style, and could spend some time to enlight and mentor new > developers, but that's the way it is. My issue with the code base is the lack of unit tests. Coming from a Ruby background, I'm used to very short methods with very specific tests, often for things that to new programmers look trivial. To RSpec users, these unit tests *are* the documentation. By comparison, darcs only has functional tests, and it's hard to see how you can tell what code is covered by them. This would make me very wary about hacking at the code, not knowing if I could inadvertently break something. It also means you have to understand much bigger chunks of code to know how to fix something. I've very often fixed a bug in Ruby code because there's a one-line spec that describes exactly the behaviour that is at fault (or a missing one for the case I want). I don't know what the standard for Haskell testing is, and how FP testing compares to OOP testing. As a very trivial example the function "showPatchInfo :: PatchInfo -> Doc" could do with a test to show it produces output of the format "Initial import Ashley Moran <ashley.moran(a)patchspace.co.uk>**20080630153800]" (and if it *doesn't*, that is the point I'm making!) I think having the patch algorithms broken down and tested in this way would be the best form of documentation, although a plain-English specification would probably also be necessary. Simpler stuff (like showPatchInfo) just needs something to demonstrate what it does. Just my (naive) opinion coming from a OOP, test-obsessed background. Ashley -- http://www.patchspace.co.uk/ http://aviewfromafar.net/

1 0

Web processing
by Rafael C. de Almeida 02 Aug '08

02 Aug '08

Hello, I understand that nowadays there are several frameworks and wrapper libraries for making some sense of the XHTML documents you find over the web. That is, making the life of those who want to process the semi-structured data you find on the sites. I don't have much experience on that field myself, but I want to learn a little more about how I can, for instance, associate information from one site with information in another site. Even though it is structured differently in both places. Does anyone know about libraries that would help me out with that sort of work? Hope I'm being clear. []'s Rafael

3 2

Cabal + yi + alex problem.
by Yann Golanski 02 Aug '08

02 Aug '08

I cannot seem to be able to install yi via cabal install. The error I get is as follows. I suspect alex is not installed in the correct place. ; sudo cabal install yi Resolving dependencies... Downloading yi-0.4.3... Configuring yi-0.4.3... cabal: alex version >=2.0.1 && <3 is required but it could not be found. cabal: Error: some packages failed to install: yi-0.4.3 failed during the configure step. The exception was: exit: ExitFailure 1 ; sudo cabal install alex Resolving dependencies... Downloading alex-2.2... [1 of 1] Compiling Main ( Setup.lhs, dist/setup/Main.o ) Linking dist/setup/setup ... Warning: defaultUserHooks in Setup script is deprecated. Configuring alex-2.2... Warning: No 'build-type' specified. If you do not need a custom Setup.hs or ./configure script then use 'build-type: Simple'. Preprocessing executables for alex-2.2... Building alex-2.2... [...] Linking dist/build/alex/alex ... Installing: /home/yann/.cabal/bin ; sudo cabal install yi Resolving dependencies... 'yi-0.4.3' is cached. Configuring yi-0.4.3... cabal: alex version >=2.0.1 && <3 is required but it could not be found. cabal: Error: some packages failed to install: yi-0.4.3 failed during the configure step. The exception was: exit: ExitFailure 1 -- yann(a)kierun.org -= H+ =- www.kierun.org PGP: 009D 7287 C4A7 FD4F 1680 06E4 F751 7006 9DE2 6318

6 9