June 2010 - Haskell-Cafe

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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The functional-object style seems to be gaining momentum.
by caseyh＠istar.ca 18 Jun '10

18 Jun '10

The functional-object style seems to be gaining momentum. Is there any way to convert monads into objects, so that beginners have an easier time with the syntax and thus we can attract more people to the language? :)

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Has anybody tried to upgrade Cabal on HP (Win 7)
by Daniel Kahlenberg 18 Jun '10

18 Jun '10

Hello, I recently installed HP 2010.1.0.0 within Windows 7 and wanted to upgrade the Cabal package to 1.8.0.6 today, sadly I got stuck on a failure building the "directory" package. So I tried to isolate the messages a bit and gave the following a try in a ghci session (1st time only with path to cygwin binaries/2nd time only with path to msys binaries added on my path variable, for both times I append the logging output): Prelude System.Cmd> > rawSystem "cabal" ["upgrade", "--constraint=base==4.*", "directory", > "-v3", "--user", > "--build-log=d:/temp/log/build-$$pkgid-$$compiler.log"] Maybe we can find the cause?! Greetz Daniel

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Re: [Haskell-cafe] What is Haskell unsuitable for?
by caseyh＠istar.ca 18 Jun '10

18 Jun '10

> If you want to use cool languages, you may have to get a cool job. I > know: it's easy to say and harder to accomplish. Most functional languages (e.g. Lisp, Haskell, ...) have a challenging time in industry since they require some savvy with multiple levels of higher abstractions and some savvy with mathematical ideas and some savvy with functional algorithms and data structures. Also, your manager has probably come up through the technical ranks on his/her OOA/OOD/OOP skills and sees you as a young (or not) upstart trying to show off. :)

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Fun Facts: A lazy bill
by Leonel Fonseca 18 Jun '10

18 Jun '10

I share this just for the sake of fun. In Costa Rica (Central America) a new series of bills are to be emitted and to celebrate bio-diversity some animal drawings are going to be used. Look at the new 10.000 colones bill: http://www.bccr.fi.cr/WebPages/PaginaInicio/NuevaFamilia/10.html Choose "reverso" in order to see the other side. -- Leonel Fonseca.

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Troubles Building LLVM
by Keith Sheppard 17 Jun '10

17 Jun '10

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

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