May 2013 - Haskell-Cafe

Re: [Haskell-cafe] Problem with compilation on MAC OS X
by Simon Thompson 30 May '13

30 May '13

Thanks - unfortunately it breaks cabal-install too! S. On 30 May 2013, at 13:28, Artyom Kazak <artyom.kazak(a)gmail.com> wrote: > Apparently, Agda has been broken by the recent decision to remove 'catch', which had already been deprecated for some time, from Prelude. You can fix the source yourself, or wait for a new release. > > On May 30, 2013 3:04 PM, "Simon Thompson" <s.j.thompson(a)kent.ac.uk> wrote: > Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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Problem with compilation on MAC OS X
by Simon Thompson 30 May '13

30 May '13

New machine, latest version of the Haskell Platform for 64 bit Mac OS X. In trying to build a new version of cabal-install and also of Agda I get variants of the same error dist/build/autogen/Paths_Agda.hs:21:13: Not in scope: `catch' any thoughts on what I am doing wrong? I have XCode command line tools installed. Thanks! Simon T. Simon Thompson | Professor of Logic and Computation School of Computing | University of Kent | Canterbury, CT2 7NF, UK s.j.thompson(a)kent.ac.uk | M +44 7986 085754 | W www.cs.kent.ac.uk/~sjt

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Re: [Haskell-cafe] using a win32 dll (Happy too soon)
by Brandon Allbery 30 May '13

30 May '13

On Wed, May 29, 2013 at 9:40 AM, Kees Bleijenberg < k.bleijenberg(a)lijbrandt.nl> wrote: > If I compile with ghc --make testGlasPng.hs –lglasPng I get: ….\ld.exe: > cannot find –lglasPng. Collect 2: ld returned 1 exit status. > > ** > > Ld can’t find lglasPng (with the l in front, does it trim the l?). Why? > Okay I try > It's reproducing the thing passed to it, rather than outputting both the dll and implib versions that it actually looks for. Same happens on unixlikes where it's looking for a .so/.dylib/whatever or a .a. **** > > ghc --make testGlasPng.hs –L<path to glasPng.dll> I get: > Not quite right; -L identifies a *directory* to search, then you must specify the actual filename afterward. > **** > > testGlasPng.o: fake: (.text + 0x82) :undefined reference to > ‘getPngVersion@0’. I think it has found the > This just means it can't find the symbol; it does not mean it necessarily found the DLL. > I run ghc on a 64 bits computer. The dll is 32 bits. Is that the problem? > That can certainly be a problem, yes, and is likely why it wasn't found with the first one. But it's not so much what kind of machine you are on, as what kind of ghc you are using: a 64-bit ghc cannot link 32-bit libraries, and vice versa. But a 32-bit ghc and toolchain will work fine on a 64-bit system, aside from not linking 64-bit DLLs. -- brandon s allbery kf8nh sine nomine associates allbery.b(a)gmail.com ballbery(a)sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net

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ANN: yi-0.6.7
by Dmitry Ivanov 30 May '13

30 May '13

Hello Cafe After about a year we've released a new version of Yi, text editor written and extensible in Haskell. Please have a look, hopefully you can find something interesting for you, whether you are emacs, vim or $(your-favorite-editor) fan. Changelog is available at https://github.com/yi-editor/yi/blob/master/CHANGELOG We currently lack active maintainers for Pango and Cocoa frontends, Emacs emulation and some smaller modules. Contributors in these areas are especially welcome. Also we have almost no user-level documentation compared to other editors, so if someone new to yi would set it up to his liking and share the experience on wiki or his blog or somewhere else, that would also be a very nice contribution. Places to dicuss using and developing yi: mailing list: https://groups.google.com/group/yi-devel issue tracker: https://github.com/yi-editor/yi/issues IRC channel: #yi@freenode (it's very slow compared to #haskell, please don't quit after 10 mins) Regards, Dmitry

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ANN: hsbencher-1.1, with Fusion Table upload
by Ryan Newton 29 May '13

29 May '13

I'm pleased to announce a new benchmarking framework, HSBencher. It's an early prototype, but it's flexible, extensible and uploads benchmark data to Google Fusion Tables. Right now the fusion table upload depends on a pre-release version of "handa-gdata" (0.6.2), which you can get at one of these locations: https://code.google.com/p/hgdata/ https://github.com/rrnewton/hgdata_mirror (It should be released soon.) Here's a blog post explaining HSBencher's usage: http://parfunk.blogspot.com/2013/05/towards-cloud-based-crowd-sourced.html Hackage: http://hackage.haskell.org/package/hsbencher Github (see README) https://github.com/rrnewton/hsbencher

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ANN: prelude-safeenum
by wren ng thornton 29 May '13

29 May '13

-------------------------------------------- -- prelude-safeenum 0.1.0 -------------------------------------------- The prelude-safeenum package offers a safe alternative to the Prelude's Enum class in order to render it safe. While we're at it, we also generalize the notion of enumeration to support types which can only be enumerated in one direction. -------------------------------------------- -- Description -------------------------------------------- The prelude-safeenum package offers an alternative to the notion of enumeration provided by the Prelude. For now it is just a package, but the eventual goal is to be incorporated into haskell prime. Some salient characteristics of the new type-class hierarchy are: * Removes partial functions: The Haskell Language Report defines pred, succ, fromEnum, and toEnum to be partial functions when the type is Bounded[1], but this is unacceptable. The new classes remove this problem by correcting the type signatures for these functions. * Generalizes the notion of enumeration: Rather than requiring that the type is linearly enumerable, we distinguish between forward enumeration (which allows for multiple predecessors) and backward enumeration (which allows for multiple successors). * Adds new functions: enumDownFrom, enumDownFromTo One of the big problems with the partiality of pred is that there is no safe way to enumerate downwards since in the border case (enumFromThen x (pred x)) will throw an error rather than evaluating to [x] as desired. These new functions remove this problem. * Removes the requirement that the enumeration order coincides with the Ord ordering (if one exists). Though, of course, it's advisable to keep them in sync if possible, for your sanity. * Ensures that the notion of enumeration is well-defined: This much-needed rigor clarifies the meaning of enumeration. In addition, it rules out instances for Float and Double which are highly problematic and often confuse newcomers to Haskell. Unfortunately, this rigor does render the instance for Ratio problematic. However, Ratio instances /can/ be provided so long as the base type is enumerable (and Integral, naturally); but they must be done in an obscure order that does not coincide with Ord. * The obscure order required for well-defined enumeration of Ratio is provided. [1] <http://www.haskell.org/onlinereport/haskell2010/haskellch6.html#x13-1310006…> -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/prelude-safeenum Darcs: http://community.haskell.org/~wren/prelude-safeenum Haddock (Darcs version): http://community.haskell.org/~wren/prelude-safeenum/dist/doc/html/prelude-s… -- Live well, ~wren

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Ghent FPG meeting on 26 June, 2013
by Jasper Van der Jeugt 29 May '13

29 May '13

Hello, The "Functional Programming Group Ghent" (GhentFPG) [1] is a friendly group for all people interested in functional programming, with a tendency towards Haskell. It is organised as part of Zeus WPI [2]. We are pleased to announce that we will hold a next meeting on Wednesday, 26th of June, starting at 19h00! There will be three talks. The main presentation, by Adam Bergmark from Silk [3] is about Fay [4]: Fay is a proper subset of Haskell that compiles to JavaScript. There is a compiler with the same name written in Haskell. Web browsers only speak JavaScript but more and more people find that they want to compile to JavaScript instead. Why do we want to compile Haskell to JavaScript, and what advantages does Fay have compared to other compilers? What are the challenges in compiling Haskell and supporting a language ecosystem, and how do we do it? What can Fay currently do, and what is planned for the future? This will be a broad overview about Fay for prospective users, followed by an in-depth look at interesting parts of the compiler internals. Additionally, there will be two short talks by two students who did an Msc. Thesis about functional programming languages: "Genetic Algorithms in Haskell" by Matthias Delbar "Automatic Detection of Recursion Patterns" by Jasper Van der Jeugt The meeting will take place in the Jozef Plateauzaal at the following address, Faculteit Ingenieurswetenschappen Universiteit Gent Plateaustraat 22 9000 Gent As mentioned above, we aim to start at 19:00. After the meeting we can go for drinks in a nearby pub (this latter part is, of course, completely optional) We hope to see you all there! Regards, On behalf of the GhentFPG organising committee. [1]: http://groups.google.com/group/ghent-fpg [2]: http://zeus.ugent.be/ [3]: http://www.silkapp.com/ [4]: http://www.fay-lang.org/

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[haskell.org Google Summer of Code 2013] Approved Projects
by Edward Kmett 29 May '13

29 May '13

We've worked our way through the project approval process for another year. This year we accepted 9 projects for haskell.org in general and are hosting 2 additional projects for darcs as an umbrella organization. haskell.org: * Parallelise 'cabal build' by Mikhail Glushenkov, mentored by Johan Tibell * Extending GHC to support building modules in parallel by Patrick Palka, mentored by Thomas Schilling * Communicating with mobile devices by Marcos Pividori, mentored by Michael Snoyman * Improve Haddock Markup and Capabilities by Fūzetsu, mentored by Simon Hengel * Haskell Qt Binding Generator by Zhengliang Feng, mentored by Carter Schonwald with help from Ian-Woo Kim * Improve the feedback of the cabal-install dependency solver by Martin Ruderer, mentored by Andres Löh * Interactive-diagrams and a paste site with the ability for dynamic rendering of diagrams by Dan Frumin, mentored by Luite Stegeman * Overloaded record fields for GHC by Adam Gundry, mentored by Simon Peyton-Jones * Port Charts to use Diagrams by Jan Bracker, mentored by Tim Docker darcs: * Better record command for darcs by José Neder, mentored by Gillaume Hoffmann * Enhancing Darcsden by BSRK Aditya, mentored by Ganesh Sittampalam Students have from now through Jun 16th to get up to speed and get to know their mentors. And while the summer of code officially starts on Jun 17th, keep in mind that the mid-term evaluations aren't that much farther behind, starting July 29th, so you'll want to hit the ground running. If you put in a project proposal and it wasn't accepted and/or you would like feedback, please feel free to email me or contact me on the #haskell-gsoc channel on irc.freenode.net. We received more proposals than slots this year, and so we were forced to make a few hard decisions. Shachaf Ben-Kiki is helping out as this year's backup administrator and he should also be able to help out with administrivia or questions as well. I'd like to thank everyone for participating in the selection process and I think we can look forward to another excellent summer of code! Edward Kmett haskell.org Google Summer of Code Administrator

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Re: [Haskell-cafe] using a win32 dll (Happy too soon)
by Robert Jakob 29 May '13

29 May '13

> If I compile with ghc --make testGlasPng.hs -lglasPng I > get: ..\ld.exe: cannot find -lglasPng. Collect 2: ld returned 1 exit > status. > > Ld can't find lglasPng (with the l in front, does it trim the l?). > Why? Okay I try > > ghc --make testGlasPng.hs -L<path to glasPng.dll> I get: > > testGlasPng.o: fake: (.text + 0x82) :undefined reference to > 'getPngVersion@0'. I think it has found the dll, but it complains the > function is not in the dll. But TDump and Dll export viewer say > getPngVersion is in the dll. I think you should use both -L and -l. ghc --make testGlasPng.hs -L/path/to/folder/where/glasPng/is -lglasPng -L should point to the folder, NOT the dll itself. Hope this helps. R.

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using a win32 dll (Happy too soon)
by Kees Bleijenberg 29 May '13

29 May '13

Unfortunatly the proposed solutions didn't work after all (It worked once, I think, but.) Here again the problem: glasPng.dll is a Delphi dll with the function getPngVersion in it. Calling convention is stdCall. I want to use this dll. The code: {-# LANGUAGE ForeignFunctionInterface #-} module Main( main ) where import Control.Monad import Foreign.C import Foreign.Marshal.Alloc import Foreign.Marshal.Array import System.Win32.Types foreign import stdcall "getPngVersion" getPngDllVersion :: IO CString main :: IO () main = do s <- getPngDllVersion putStrLn (show s) glasPng.dll is in the Windows path (I've checked it). If I compile with ghc --make testGlasPng.hs -lglasPng I get: ..\ld.exe: cannot find -lglasPng. Collect 2: ld returned 1 exit status. Ld can't find lglasPng (with the l in front, does it trim the l?). Why? Okay I try ghc --make testGlasPng.hs -L<path to glasPng.dll> I get: testGlasPng.o: fake: (.text + 0x82) :undefined reference to 'getPngVersion@0'. I think it has found the dll, but it complains the function is not in the dll. But TDump and Dll export viewer say getPngVersion is in the dll. I run ghc on a 64 bits computer. The dll is 32 bits. Is that the problem? What can I do? Kees

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