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building c2hs on Mac
by John Lato 23 Oct '08

23 Oct '08

Hello, I've been trying to build c2hs-0.15.1 on an Intel Mac (10.4), and am having some difficulty. It has dependencies on happy and alex, which would be fine, except that alex itself seems to require alex (using alex 2.2). Does anyone have any suggestions for how to get around this? I have ghc-6.8.3 and ghc-6.10 RC, and could use either. Last time I tried to build c2hs on a mac I think I used macports, which worked fine, except that's not an option this time because the computer in question isn't (and won't be) online. I'd have to rebuild ghc anyway, which I don't want to do. Thanks, John Lato

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Plans for new System.Process?
by Stephen Hicks 23 Oct '08

23 Oct '08

Hi, I've been trying out the new System.Process and have found it to be very useful. I was wondering what the plans for it were - I'd rather not give up support for older versions of ghc just because I want to use createProcess. Are there plans of releasing process-1.0.1 so that it's compatible with older compilers too? Or does it depend on something internally that makes this impossible? Cheers, steve

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Re: [Haskell-cafe] Re: universal algebra "support" in Haskell?
by Nathan Bloomfield 23 Oct '08

23 Oct '08

This question is relevant to a project I'm working on. I've been putting together an abstract algebra library for handling computations inside group rings, polynomial rings, and rings with adjoined elements. Once I've got it cleaned up a little I'll upload it to an appropriate place. (I forgot to cc haskell-cafe- sorry DavidA!) Nathan Bloomfield

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Call for Papers: Workshop on Language Descriptions, Tools and Applications 2008
by Jurgen Vinju 23 Oct '08

23 Oct '08

LDTA: Workshop on Language Descriptions Tools and Applications ===Call For Papers 2009=== This is the Call For Papers for the Ninth Workshop on Language Descriptions, Tools and Applications (LDTA 2009) LDTA is a two-day satellite event of ETAPS which takes on the 28th and 29th of March 2009 in York, England. ==Scope== LDTA is an application and tool oriented forum on meta programming in a broad sense. A meta program is a program that takes other programs as input or output. The focus of LDTA is on generated or otherwise efficiently implemented meta programs, possibly using high level descriptions of programming languages. Tools and techniques presented at LDTA are usually applicable in the context of "Language Workbenches" or "Meta Programming Systems" or simply as parts of advanced programming environments or IDEs. The applications areas include, but are not limited to: * Program analysis, transformation, generation and verification * Implementation of Domain Specific Languages (both visual and textual) * Reverse engineering and reengineering * Refactoring and other source-to-source transformations * Application modelling (MDE, MDA, Software Factories, Software product lines) * Grammar engineering / Grammarware * Language definition and language prototyping * Debugging, profiling and testing * IDE construction * Compiler construction LDTA is a well-established workshop next to other conferences and workshops on (programming) language engineering topics such as SLE and GPCE.LDTA is traditionally a forum where computer science theories are put to the test of real-world software engineering issues, for example by applying: * context-free grammars to parser generation for real programming languages, * attribute grammars to static analyzer and compiler generation, * term rewriting to source-to-source transformation, * action semantics to programming language implementation, * model checking to software verification. Note that LDTA solicits submissions from any technological or theoretical domain, as long as the paper is within the application scope. ==Submission Procedure and Publication== Submissions in the following categories are admissible: * research papers, * tool papers, * experience papers The final versions of accepted papers will probably(*) be published in Electronic Notes in Theoretical Computer Science (ENTCS), Elsevier Science, and will be made available during the workshop. (*)Due to organizational changes at Elsevier, publication by ENTCS publication is provisional; another comparable venue will be found otherwise. Each submission must: * clearly and unambiguously state in which of the three categories it falls * be original, i.e. not published or submitted elsewhere, * contain a clear motivation, * contain a thorough analysis of the claimed contributions (for example by comparing to related work), * be written in less than 15 pages (research papers and experience reports), or less than 10 pages (tool papers) * use the ENTCS style. The authors of each submission are required to give a presentation at LDTA 2009. The authors of the tool papers are required to include an interactive demonstration in their presentations. The authors of the best papers will be invited to write a journal version of their paper which will be separately reviewed and, assuming acceptance, be published in journal form. As in past years, this will be done in a special issue devoted to LDTA 2009 of the journal Science of Computer Programming (Elsevier Science). The authors of the best tool papers will be invited to write a paper and submit the source of code of their tool, which will both be separately reviewed and, assuming acceptance, be published in the special issue on Experimental Software and Toolkits (EST) of the journal Science of Computer Programming (Elsevier Science). Please submit your abstract and paper using http://www.easychair.org/conferences/?conf=ldta2009 ==Program Committee== Jurgen Vinju, CWI, Amsterdam (co-chair) Torbjörn Ekman, Oxford, UK (co-chair) Erik Meijer, Microsoft, Redmond, USA Walid Taha, Rice University, Houston USA Bob Fuhrer, IBM TJ Watson, USA Susan Eisenbach, Imperial College, UK Jean-Marie Jacquet, FUNDP, Namur, Belgium Sibylle Schuppe, Chalmers, Sweden Elizabeth Scott, RHUL, UK Robert Grimm, NYU, USA Judith Bishop, Pretoria, South Africa Tudor Girba, Univ of Berne, Switzerland Marjan Mernik, University of Maribor, Slovenia Thomas Dean, Fondazione Bruno Kessler - IRST, Italy Martin Bravenboer, Univ. of Oregon, USA Pierre-Etienne Moreau, INRIA-LORIA, France Gabi Taentzer, Philipps-Universität Marburg, Germany Joao Saraiva, Universidade do Minho, Braga, Portugal Tijs van der Storm, CWI, The Netherlands Stephen Edwards, Columbia University, USA Peter Thiemann, Universität Freiburg, Germany ==Important Dates== Abstract submission deadline:Friday November 28th, 2008 Paper submission deadline:Friday December 5th, 2008 Notification of acceptance:Friday February 6th, 2009 Workshop date:28th and 29th of March, 2009

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the Haskell notion of class vis-a-vis universal algebra?
by Galchin, Vasili 23 Oct '08

23 Oct '08

Hello, What is the relationship of a Haskell class to universal algebra? (a refresher ... http://en.wikipedia.org/wiki/Universal_algebra) ... it seems that all types that belong to a class are models? E.g. all "monads" have to satisfy the "monad laws" stated in the Monad class, i.e. equational axioms! Vasili

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Help converting Perl to Haskell
by Jason Dagit 23 Oct '08

23 Oct '08

Hello, I'm not very perl literate, but I want to convert a perl script to Haskell. This bit of perl is part of darcs' test suite. I was hoping to make it "more portable" by writing it in Haskell. By more portable I mean, works in windows without cygwin/mingw/msys and avoids the need for perl also. Depending on a Haskell compiler seems reasonable since darcs is written in Haskell :) Correct me if I'm wrong, but if I want to make this work on windows I can't use System.Posix, right? If so, what is the portable way to set environment variables? I see[1] that getEnv exists in System.Environment, but setEnv is in System.Posix.Env. I looked in System.Win32 and I didn't see anything that looked like it would manipulate environment variables. Will I have to use System.Process.runProcess on Win32? I'd like this to work on ghc 6.6 and System.Process looks new? Another thing I noticed is that System.Directory doesn't give me a way to exactly emulate this bit of perl: mkdir 'test_output', 0750; If I use System.Directory.setPermissions, then I think the closest I can approximate those permissions is: setPermissions "test_output" (Permissions {readable = True, writable = True, executable = True, searchable = True}) Which just makes sure it has the 7 for user, but doesn't seem to change the other permissions. Maybe that won't matter in practice, but I wanted to make it as close as possible to minimize unforeseen problems. I guess I could write a function that uses setPermissions on win32 and uses the appropriate thing from System.Posix when not on windows. Below is the full perl script if you want to see what I'm starting from. I think most of it should be easy to replace. \begin{perl} #!/usr/bin/perl -w # Run each of the shell tests, capturing the output, and reporting passed # or failed. use Cwd; use File::Find; # Place to put test output to avoid cluttering test/ mkdir 'test_output', 0750; # Override the users default .darcs settings $ENV{HOME} = cwd(); mkdir '.darcs'; system 'echo ALL --ignore-times >> .darcs/defaults'; # Used for finding darcs, but may not be defined by the shell $ENV{PWD} = cwd(); # Put the right darcs first in PATH my $darcspath="$ENV{HOME}/.."; if ($ENV{DARCS}) { # User has asked for a particular darcs... my $actualdarcs=`which $ENV{DARCS}`; my $darcspath=`dirname "$actualdarcs"`; } $ENV{PATH} = "$darcspath:$ENV{PATH}"; # Some environment variables can act as defaults that we don't want $ENV{EMAIL} = $ENV{DARCS_EMAIL} = 'tester'; # These two environment variables will turn off darcs' "Christmas mode". # It will make the tests run a tad faster, and make darcs' output # independent of the testing systems locale and environment. $ENV{DARCS_DONT_COLOR} = 1; $ENV{DARCS_DONT_ESCAPE_ANYTHING} = 1; my $OK = 1; my @Failures; my @Passes; `which bash`; if( $? != 0 ) { die "You need bash to run the shell tests!" } for my $test (@ARGV) { my $test_out = "test_output/$test.out"; printf "Running %-40s", "$test ..."; my $output = `bash $test 2>&1`; if( $? == 0 ) { push @Passes, $test; print " passed.\n"; } else { $OK = 0; push @Failures, $test; print " FAILED!\n"; print "Output from failed $test:\n$output"; } # give ourselves write permissions to every file in a tmp dir # (in case a script sets permissions and fails to clean up # after itself) my @tmpdirs = glob("tmp* temp*"); if (@tmpdirs > 0) { find (sub { chmod 0755, $_; }, @tmpdirs); } } my $CWD = cwd(); if ($CWD =~ /bugs/ && $#Passes >= 0) { print "Some tests passed:\n"; print "\t$_\n" for @Passes; } if ($OK) { print "All tests successful!\n"; } else { print "TESTS FAILED!\n"; print "\t$_\n" for @Failures; } # Exit with non-zero if anything failed. exit !$OK; \end{perl} Thanks! Jason [1] http://www.haskell.org/ghc/docs/latest/html/libraries/

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Cabal warning
by Henk-Jan van Tuyl 22 Oct '08

22 Oct '08

L.S., I keep getting the following warning for each "cabal install" command: Warning: Error parsing config file C:\Documents and Settings\[User]\Application Data\cabal\config: On line 1: GHC Warning: Using default configuration. The first line of this file is: compiler: GHC What can I do about this? -- Regards, Henk-Jan van Tuyl -- http://functor.bamikanarie.com http://Van.Tuyl.eu/ --

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Spine-lazy "multiqueue"
by Luke Palmer 22 Oct '08

22 Oct '08

Hi, I need a rather strange data structure, and I can't find any existing implementations or think of a way to implement it. It's a "multiqueue", basically a map of queues. The trick is that it should be lazy in its spine and still support efficient access. For example, the following should hold: dequeue 1 (foldr (enqueue 1) empty [42..]) = Just (42, ...) (where dequeue :: k -> QMap k v -> Maybe (v, QMap k v), similarly for enqueue) I also need a unionWith :: ([v] -> [v] -> [v]) -> QMap k v -> QMap k v -> QMap k v. I realize that these might be some pretty tough requirements to meet. Any pointers or original ideas? Thanks, Luke

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Template Haskell
by Andrew Coppin 22 Oct '08

22 Oct '08

If I'm understanding this correctly, Template Haskell is a way to auto-generate repetative Haskell source code. The thing that worries me is... if you need to write repetative Haskell source code, doesn't that mean that Haskell itself is broken in the first place?

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ghc error: requested module name differs from name found in interface file
by Larry Evans 22 Oct '08

22 Oct '08

With a file containing: > module Main where > > import Array > import Control.Functor.Fix I get: > make > ghc -i/root/.cabal/lib/category-extras-0.53.5/ghc-6.8.2 -c catamorphism.example.hs > > catamorphism.example.hs:19:0: > Bad interface file: /root/.cabal/lib/category-extras-0.53.5/ghc-6.8.2/Control/Functor/Fix.hi > Something is amiss; requested module main:Control.Functor.Fix differs from name found in the interface file category-extras-0.53.5:Control.Functor.Fix > make: *** [all] Error 1 I used cabal to install category-extras: > /home/evansl/download/haskell/libs # cabal install category-extras > Resolving dependencies... > Downloading category-extras-0.53.5... > Configuring category-extras-0.53.5... > Preprocessing library category-extras-0.53.5... ... > /usr/bin/ar: creating dist/build/libHScategory-extras-0.53.5.a > Installing library in /root/.cabal/lib/category-extras-0.53.5/ghc-6.8.2 > Registering category-extras-0.53.5... > Reading package info from "dist/installed-pkg-config" ... done. > Saving old package config file... done. > Writing new package config file... done. > /home/evansl/download/haskell/libs # What should I do to import the Functor.Fix as shown here: http://comonad.com/reader/2008/recursion-schemes/ TIA. -Larry

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