- Haskell-Cafe - Haskell.org

Installing Erlang on OSX
by Giuseppe Luigi Punzi Ruiz 21 Jun '10

21 Jun '10

Hi all, I would like to play a little with erlang. I downloaded Haskell platform, ang ghc and ghci seems to work. Trying to install leksah, Cabal, gives me the following error. http://trac.haskell.org/haskell-platform/ticket/110 I downloaded and installed Haskell Platform from source. Did.. cabal update cabal install cabal-install cabal install gtk2hs-buildtools cabal install leksah The last command didn't finish, with this output: ************************************************************ .. ... [22 of 23] Compiling Text.Regex.TDFA.Sequence ( Text/Regex/TDFA/ Sequence.hs, dist/build/Text/Regex/TDFA/Sequence.o ) Text/Regex/TDFA/Sequence.hs:36:9: Warning: orphan instance: instance RegexContext Regex (Seq Char) (Seq Char) Text/Regex/TDFA/Sequence.hs:40:9: Warning: orphan instance: instance RegexMaker Regex CompOption ExecOption (Seq Char) Text/Regex/TDFA/Sequence.hs:46:9: Warning: orphan instance: instance RegexLike Regex (Seq Char) [23 of 23] Compiling Text.Regex.TDFA ( Text/Regex/TDFA.hs, dist/build/ Text/Regex/TDFA.o ) Registering regex-tdfa-1.1.3... Installing library in /Users/glpunzi/.cabal/lib/regex-tdfa-1.1.3/ ghc-6.12.1 Registering regex-tdfa-1.1.3... cabal: Error: some packages failed to install: cairo-0.11.0 failed during the configure step. The exception was: ExitFailure 1 gio-0.11.0 depends on glib-0.11.0 which failed to install. glib-0.11.0 failed during the configure step. The exception was: ExitFailure 1 gtk-0.11.0 depends on glib-0.11.0 which failed to install. gtksourceview2-0.11.0 depends on glib-0.11.0 which failed to install. leksah-0.8.0.6 depends on glib-0.11.0 which failed to install. leksah-server-0.8.0.6 depends on glib-0.11.0 which failed to install. ltk-0.8.0.6 depends on glib-0.11.0 which failed to install. pango-0.11.0 depends on glib-0.11.0 which failed to install. ************************************ Possible usefull info: galilea-2:haskell-platform-2010.1.0.0 glpunzi$ cabal --version cabal-install version 0.8.0 using version 1.8.0.2 of the Cabal library galilea-2:haskell-platform-2010.1.0.0 glpunzi$ ghc --version The Glorious Glasgow Haskell Compilation System, version 6.12.1 Some idea how to get leskah, or/and full Haskell working under OSX? Thanks in advance. Giuseppe Luigi Punzi Ruiz Blog: http://www.lordzealon.com Twitter & Skype & GoogleTalk accounts: glpunzi

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Haskell Indonesia
by vipex.id 21 Jun '10

21 Jun '10

Hi, I'm new in Haskell & wondering is there Indonesian people using Haskell here. Nice meet* you all :) Regards, vipex

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Third Ghent FPG Meeting on Tuesday, June 29: Final Program
by Jeroen Janssen 20 Jun '10

20 Jun '10

(apologies if you receive multiple copies) Dear all, We have finalized the program for the third Ghent FPG Meeting on Tuesday, June 29 in the Technicum building of Ghent University (Sint-Pietersnieuwstraat 41, 9000 Gent) at 19h. As before, to enter the building, you should go to the automatic sliding door on the far left of the building and dial the phone number provided on the note that is taped to the door. Someone will then open the door for you. The program is as follows: 1. Pierre Carbonnelle - Declarative programming for Business Logic - a new Open-source project Declarative programming has made major inroads in the Presentation and Persistence layers of applications, with HTML, CSS and SQL. Why has it not been popular in the Business Logic layer of applications ? Pierre Carbonnelle, an engineer with 20 years of experience in the IT industry, will present a new open source project, "Yoopf", that aims to fix this gap. It uses the "formula- based" models of spreadsheets for the development of business applications, with a particular emphasis on the Google App Engine platform. Research opportunities will be discussed. 2. Tom Schrijvers - Monadic Constraint Programming A constraint programming system combines two essential components: a constraint solver and a search engine. The constraint solver reasons about satisfiability of conjunctions of constraints, and the search engine controls the search for solutions by iteratively exploring a disjunctive search tree defined by the constraint program. We give a monadic definition of constraint programming where the solver is defined as a monad threaded through the monadic search tree. We are then able to define search and search strategies as first class objects that can themselves be built or extended by composable search transformers. Search transformers give a powerful and unifying approach to viewing search in constraint programming, and the resulting constraint programming system is first class and extremely flexible. This is joint work with Peter Stuckey (University of Melbourne) and Philip Wadler (University of Edinburgh). 3. Wouter Kampmann, Lieven Lemiengre - Lightning Talk on Scala Hope to see you there! Bart Coppens (bart.coppens(a)elis.ugent.be) Jeroen Janssen (jejansse(a)gmail.com) Jasper Van der Jeugt (jaspervdj(a)gmail.com) The Ghent FPG organizing committee.

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Mapping a list of functions
by Martin Drautzburg 20 Jun '10

20 Jun '10

Hello all The standard map function applies a single function to a list of arguments. But what if I want to apply a list of functions to a single argument. I can of course write such a function, but I wonder if there is a standard way of doing this, Related to that is the problem, that the function in map may require more than one argument, so I need to apply it partially to some value(s) first. But what if I want to fix its second and third argument and not its first argument? Can flip help? Thanks -- Martin

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lecture notes for Finally Tagless - benefit of explicit fix combinator
by Günther Schmidt 20 Jun '10

20 Jun '10

Hi all, I'm working my way through the lecture notes to the "Finally Tagless" course, available from: http://okmij.org/ftp/tagless-final/course/index.html As usual at every round of doing so, I think it's my 4th, I discover something new, something that hadn't occurred to me previously. This time it's a comment in the code of SerializeExt.hs -- * Tie up the knot fromTree = S.fix fromTreeExt -- One does use fix in real programs -- Now we can see the real benefit of using fix in real programs. -- The fixpoint combinator is NOT a mere curiosity about the fix-point combinator. I don't think I can deduce what he meant by that from the context alone, could somebody please enlighten me? I'm refering to the benefit of using the fix-point combinator in this particular scenario. Günther

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Re: Modules and their explicit export lists (are an annoyance)
by Antoine Latter 19 Jun '10

19 Jun '10

Hi Christian, Is there a specific library you're having trouble with? One reason library authors can prefer explicit export lists is that they can hide implementation details, which can then make it easier to change in the future without breaking the users of the library. Antoine Cc'ing the haskell-cafe On Jun 19, 2010 1:39 PM, "Christian Höner zu Siederdissen" < choener(a)tbi.univie.ac.at> wrote: Hi everybody, I'd like some input on other peoples' thoughts on this. Recently, I played around with a library that uses an explicit export list. While there are reasons for having one: - efficiencey (inlining in the module) - encapsulation in practice, it seems to me that they are more annoying than useful. For once, it would think that ghc should produce efficient good across modules with -O / -O2 anyway. But the more important thing is, that it makes extending module functionality a pain (eg. if a constructor is not exported using (..)). So, should I really fork a library just to be able to add a function? Btw. there are libraries, where an explicit export list is used, that export the right amount of information. For example, in 'vector' enough is exported to allow you to extend unboxed vectors. _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users(a)haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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Vague: Assembly line process
by Martin Drautzburg 19 Jun '10

19 Jun '10

Hello all, this is a problem which has haunted me for some time. If this is simply hillarious, please tell me so. Or it may be some well known unsolvable problem... An assembly process takes inputs and produces outputs. I could say a Process is a function canProduce :: [Input]->[Output]->Bool which tells me if the outputs can be produced from the inputs There may be a similar function which tells me if the inputs are completely consumed to procude the output. The inputs do not determine the exact outputs. Think of a Process which combines a List of Ints into pairs, such that the input ints are consumed and each input Int occurs in only one position in the output. There are many ways to do this. Still for any set of input Ints and output pairs I could decide if the output can be produced from the input. Likewise the Input is not determined by the output. There may be lots of choices from what I could build my output (buy from different vendors). When I know more about the inputs and outputs my choices get more and more limited. I would like to to pass inputs and/or outputs to "something" and I would like to get a "something" which is more restricted, but still essentially a thing which tells me if the outputs can be produced from the inputs. I just cannot find a way to even THINK about this problem in a reasonable general way. -- Martin

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Re: Troubles Building LLVM (Fixed)
by Keith Sheppard 19 Jun '10

19 Jun '10

Hello, in case someone else hits this problem I was able to fix it by installing the latest haskell platform via macports. - I uninstalled ghc "sudo /Library/Frameworks/GHC.framework/Tools/Uninstaller" - deleted ~/.ghc and ~/.cabal - did a "sudo port install haskell-platform" (be prepared for this to take a couple of hours). ghc --version gives 6.10.4 - cabal install llvm I still don't know the root cause of the build error but now the llvm examples build and run with no errors. -Keith On Thu, Jun 17, 2010 at 10:46 PM, Keith Sheppard <keithshep(a)gmail.com> wrote: > Hello All, > > I'm trying to get up and running with the very interesting llvm > package[1] but I'm running into problems during the linking stage. > > keith@sugarglider-2:~/projects/third-party/llvm-hs-bindings/examples/> > make clean all > rm -f HelloJIT Fibonacci BrainF Vector Array DotProd Arith Align > Struct Varargs *.o *.hi *.s *.bc Fib *.exe *.exe.manifest *~ > ghc -Wall -optl -w --make -o HelloJIT.exe -main-is HelloJIT.main HelloJIT.hs > [1 of 1] Compiling HelloJIT ( HelloJIT.hs, HelloJIT.o ) > Linking HelloJIT.exe ... > Undefined symbols: > "_LLVMAddCondPropagationPass", referenced from: > _ssCM_info in libHSllvm-0.7.1.1.a(Scalar.o) > ld: symbol(s) not found > collect2: ld returned 1 exit status > make: *** [HelloJIT.exe] Error 1 > > It's probably something very simple that I'm doing wrong since this is > my first Haskell build linking against foreign libs. Do you know what > I might be doing wrong? > > Here are the versions: > Mac OS X 10.5.8 > GHC 6.10.1 (waiting out a leopard installer bug [2]) > llvm-2.7 installed to default location > llvm package version 0.7.1.1 > > Thanks! > > BTW, the combination of this package plus the awesome Haskell parsers > seem to make for a great compiler construction kit. I'm looking > forward to playing around w/ llvm > > [1] http://hackage.haskell.org/package/llvm > [2] http://trac.haskell.org/haskell-platform/ticket/110 > > -- > keithsheppard.name > -- keithsheppard.name

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ANN: BlazeHtml 0.1
by Jasper Van der Jeugt 19 Jun '10

19 Jun '10

Hello all, In light of Google Summer of Code, we are proud to release the first version of BlazeHtml today. It's a 0.1 release, so beware of bugs! Nevertheless, we encourage you to try it out. You can find more information: - On the website: http://jaspervdj.be/blaze - On hackage: http://hackage.haskell.org/package/blaze-html-0.1 - In this blogpost: http://jaspervdj.be/posts/2010-06-20-blazehtml-0.1.html Looking forward to your feedback, Kind regards, Jasper Van der Jeugt Simon Meier

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ANN: text-json-qq - json quasiquatation
by Oscar Finnsson 18 Jun '10

18 Jun '10

Hi, I've just uploaded the first version of text-json-qq (http://hackage.haskell.org/package/text-json-qq) It's a quasiquatation library converting json into Haskell (Text.JSON). You can use it like: > user = [$jsonQQ| {name: "Pelle", age: 34.3, likes: ["mac", "Haskell"] } |] or you can use Haskell variables with the <<x>>-syntax like: > user = [$jsonQQ| {name: <<name>>, age: <<age>>} |] > name = "Pelle" > age = 34 :: Integer It seems to have some performance problems at the moment so I guess I'll have to learn how to profile my code. -- Oscar

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