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In ML books; functors only consume & produce structures; whereas, functions C&P values.
by KC 11 Jun '11

11 Jun '11

I've never seen such an easy description in Haskell books. Is there more going on with Haskell functors? -- -- Regards, KC

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Class and Instance
by Patrick Browne 11 Jun '11

11 Jun '11

Hi Below is a class that I wish to create some instances of. I do not wish to change the class definition. It is supposed to represent containers of type x that contain things of type y. My attempt at the insert function seems ok for Char and lists, but not ok for Integer. How do I instantiate this class for integers and lists? Does this class definition permit y to be a list and hence x to be a list of lists? Something like: instance Containers [] [] where .. Is this a constructor class? Thanks, Pat class Containers x y where insert :: y -> x y -> x y remove :: y -> x y -> x y whatsIn :: x y -> [y] instance Containers [] Char where insert y [] = y:[] insert y m = y:m instance Containers [] Integer where insert y [] = y:[] insert y m = y:m -- OK -- insert '1' ['u','u','l','i'] -- Not OK -- insert 2 [9,2] This message has been scanned for content and viruses by the DIT Information Services E-Mail Scanning Service, and is believed to be clean. http://www.dit.ie

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Vi mode in ghci?
by David McBride 11 Jun '11

11 Jun '11

Somehow in the distant past I managed to get vi editing mode working for ghci on ghc 6, but when I upgraded to ghc 7, I can't seem to figure out how to enable it anymore. I think I might have been using ghci-haskeline in the past. A post I read somewhere suggested that ghc 7 should have innate support for vi mode, but I can't figure out if it does, or how to enable it. Does anyone know? I'm willing to recompile ghc to use readline to get vi mode support if that is possible and the only way to do so.

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Cabal fail
by Andrew Coppin 11 Jun '11

11 Jun '11

How do you make Cabal fail? Let me clarify. I built a package that uses a post-configure hook to do some settings detection. Under certain circumstances, it can fail. When this happens, the hook prints "fatal error" and quits. Unfortunately, I didn't actually /test/ whether it works. On further investigation, I discovered that the hook considers itself to have failed, but it doesn't bother actually telling Cabal about this. (!) So Cabal still thinks everything went fine. OK, so, let's the correct way to notify Cabal that we need to retry the configure step? I can't figure it out from the minimal documentation in Distribution.Simple. (I'm guessing I need to use a pre-configure hook, since by the time post-configure runs, the configure stage is presumably over...?)

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best way to use ghc-7.0 under debian stable
by briand＠aracnet.com 11 Jun '11

11 Jun '11

Hi All, Currently debian stable installs ghc 6.12.1. I'd like to use the latest version of repa which is built on ghc 7.0, and my attempts to placate cabal's complaints about the installation of various packages isn't going anywhere. It's not obvious to me that there's an advantage to using debian for ghc if I want to stay on the latest ghc to support various packages. I'm wondering what the best way to maintain the latest ghc while using debian stable. Should I abandon the ghc debian package and install the haskell-platform ? Should I simply build ghc 7.0 independently ? The advantage of building ghc myself would of course be the ability to incorporate latest patches etc, and that seems like a good way to go. Any advice appreciated. Thanks, Brian

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Installing Gtk2Hs on Win32
by Dmitri O.Kondratiev 11 Jun '11

11 Jun '11

Please help to find pre-compiled binary libraries of Gtk+ for Win32. Gtk2Hs insatll instructions at: http://code.haskell.org/gtk2hs/INSTALL tells us: [quote] Building on Windows -------------------- Installation on Windows is nearly as easy as on Unix platforms. However, you need to download the pre-compiled binary libraries of Gtk+ and all it's dependent libraries. Point your browser to http://www.gtk.org/download-windows.html and download one of the "All-in-one bundles". Note that you do *not* need to install MinGW nor MSys (but it does not hurt if they are installed on your system). Install the binaries by unpacking them into a directory without spaces. [/quote] This link (http://www.gtk.org/download-windows.html) is dead. Where to get pre-compiled binary libraries of Gtk+ ? Thanks!

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Matplotlib analog for Haskell?
by Dmitri O.Kondratiev 10 Jun '11

10 Jun '11

Hello, Please advise on Haskell 2D plotting libraries to generate plots, histograms, power spectra, bar charts, errorcharts, scatterplots, etc, similar to what Matplotlib does: http://matplotlib.sourceforge.net/ Thanks! Dmitri

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Errors installing 'Haskell Charts'
by Dmitri O.Kondratiev 10 Jun '11

10 Jun '11

I am trying to install HaskellCharts at: http://dockerz.net/twd/HaskellCharts Running: cabal update cabal install gtk2hs-buildtools cabal install gtk cabal install chart goes well untill 'cabal install chart' which results in: C:\wks\RCA>cabal install chart Resolving dependencies... C:\Users\DKONDR~1\AppData\Local\Temp\cairo-0.12.03136\cairo-0.12.0\Gtk2HsSetup.h s:25:2: warning: #warning Setup.hs is guessing the version of Cabal. If compilat ion of Setup.hs fails use -DCABAL_VERSION_MINOR=x for Cabal version 1.x.0 when b uilding (prefixed by --ghc-option= when using the 'cabal' command) [1 of 2] Compiling Gtk2HsSetup ( C:\Users\DKONDR~1\AppData\Local\Temp\cairo -0.12.03136\cairo-0.12.0\Gtk2HsSetup.hs, C:\Users\DKONDR~1\AppData\Local\Temp\ca iro-0.12.03136\cairo-0.12.0\dist\setup\Gtk2HsSetup.o ) [2 of 2] Compiling Main ( C:\Users\DKONDR~1\AppData\Local\Temp\cairo -0.12.03136\cairo-0.12.0\Setup.hs, C:\Users\DKONDR~1\AppData\Local\Temp\cairo-0. 12.03136\cairo-0.12.0\dist\setup\Main.o ) Linking C:\Users\DKONDR~1\AppData\Local\Temp\cairo-0.12.03136\cairo-0.12.0\dist\ setup\setup.exe ... Configuring cairo-0.12.0... setup.exe: The program pkg-config version >=0.9.0 is required but it could not be found. C:\Users\DKONDR~1\AppData\Local\Temp\glib-0.12.03136\glib-0.12.0\Gtk2HsSetup.hs: 25:2: warning: #warning Setup.hs is guessing the version of Cabal. If compilatio n of Setup.hs fails use -DCABAL_VERSION_MINOR=x for Cabal version 1.x.0 when bui lding (prefixed by --ghc-option= when using the 'cabal' command) [1 of 2] Compiling Gtk2HsSetup ( C:\Users\DKONDR~1\AppData\Local\Temp\glib- 0.12.03136\glib-0.12.0\Gtk2HsSetup.hs, C:\Users\DKONDR~1\AppData\Local\Temp\glib -0.12.03136\glib-0.12.0\dist\setup\Gtk2HsSetup.o ) [2 of 2] Compiling Main ( C:\Users\DKONDR~1\AppData\Local\Temp\glib- 0.12.03136\glib-0.12.0\Setup.hs, C:\Users\DKONDR~1\AppData\Local\Temp\glib-0.12. 03136\glib-0.12.0\dist\setup\Main.o ) Linking C:\Users\DKONDR~1\AppData\Local\Temp\glib-0.12.03136\glib-0.12.0\dist\se tup\setup.exe ... Configuring glib-0.12.0... setup.exe: The program pkg-config version >=0.9.0 is required but it could not be found. cabal: Error: some packages failed to install: Chart-0.14 depends on glib-0.12.0 which failed to install. cairo-0.12.0 failed during the configure step. The exception was: ExitFailure 1 gio-0.12.0 depends on glib-0.12.0 which failed to install. glib-0.12.0 failed during the configure step. The exception was: ExitFailure 1 gtk-0.12.0 depends on glib-0.12.0 which failed to install. pango-0.12.0 depends on glib-0.12.0 which failed to install. Where to get glib-0.12.0 ? Thanks!

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Building Haskell Platform natively for 64bit Windows
by John Sneer 10 Jun '11

10 Jun '11

Hello all, I know it is not probably good question to this list, but anyway, could anyone point me to some more detailed "how to" where is described building of Haskell Platform natively to 64bit Windows? I have no problem using 32bit version until I need more than 2GB of RAM. I went through some older threads, but description like: 1) install gcc 2) install ghc 3) build platform is something that didn't work well. Is there some more detailed description or recommended versions etc? If there is none then there is no need to respond. Thanks, regards J. -- John Sneer johnsneer(a)operamail.com -- http://www.fastmail.fm - Does exactly what it says on the tin

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Deadline June 17: ACM SIGPLAN Workshop on ML
by Chung-chieh Shan 10 Jun '11

10 Jun '11

ACM SIGPLAN Workshop on ML Sunday, 18 September 2011, Tokyo, Japan (co-located with ICFP) http://conway.rutgers.edu/ml2011/ CALL FOR CONTENT The ML family of programming languages includes dialects known as Standard ML, Objective Caml, and F#. These languages have inspired a large amount of computer-science research, both practical and theoretical. This workshop aims to provide a forum for discussion and research on ML and related technology (higher-order, typed, or strict languages). The format of ML 2011 will continue the return in 2010 to a more informal model: a workshop with presentations selected from submitted abstracts. Presenters will be invited to submit working notes, source code, and extended papers for distribution to the attendees, but the workshop will not publish proceedings, so any contributions may be submitted for publication elsewhere. We hope that this format will encourage the presentation of exciting (if unpolished) research and deliver a lively workshop atmosphere. SCOPE We seek research presentations on topics related to ML, including but not limited to * applications: case studies, experience reports, pearls, etc. * extensions: higher forms of polymorphism, generic programming, objects, concurrency, distribution and mobility, semi-structured data handling, etc. * type systems: inference, effects, overloading, modules, contracts, specifications and assertions, dynamic typing, error reporting, etc. * implementation: compilers, interpreters, type checkers, partial evaluators, runtime systems, garbage collectors, etc. * environments: libraries, tools, editors, debuggers, cross-language interoperability, functional data structures, etc. * semantics: operational, denotational, program equivalence, parametricity, mechanization, etc. Research presentations should describe new ideas, experimental results, significant advances in ML-related projects, or informed positions regarding proposals for next-generation ML-style languages. We especially encourage presentations that describe work in progress, that outline a future research agenda, or that encourage lively discussion. In addition to research presentations, we seek both Status Reports and Demos that emphasize the practical application of ML research and technology. Status Reports: Status reports are intended as a way of informing others in the ML community about the status of ML-related research or implementation projects, as well as communicating insights gained from such projects. Status reports need not present original research, but should deliver new information. In the abstract submission, describe the project and the specific technical content to be presented. Demos: Live demonstrations or tutorials should show new developments, interesting prototypes, or work in progress, in the form of tools, libraries, or applications built on or related to ML. In the abstract submission, describe the demo and its technical content, and be sure to include the demo's title, authors, collaborators, references, and acknowledgments. (Please note that you will need to provide all the hardware and software required for your demo; the workshop organizers are only able to provide a projector.) Each presentation should take 20-25 minutes, except demos, which should take 10-15 minutes. The exact time will be decided based on the number of accepted submissions. We plan to make videos of the presentations available on ACM Digital Library. SUBMISSION INSTRUCTIONS Email submissions to ccshan AT cs.rutgers.edu. Submissions should be at most two pages, in PDF format, and printable on US Letter or A4 sized paper. Persons for whom this poses a hardship should contact the program chair. Submissions longer than a half a page should include a one-paragraph synopsis suitable for inclusion in the workshop program. IMPORTANT DATES * 2011-06-17: Submission * 2011-07-22: Notification * 2011-09-18: Workshop PROGRAM COMMITTEE Amal Ahmed (Indiana University) Andrew Tolmach (Portland State University) Anil Madhavapeddy (University of Cambridge) Chung-chieh Shan (chair) (Rutgers University) Joshua Dunfield (Max Planck Institute for Software Systems) Julia Lawall (University of Copenhagen) Keisuke Nakano (University of Electro-Communications) Martin Elsman (SimCorp) Walid Taha (Halmstad University) STEERING COMMITTEE Eijiro Sumii (chair) (Tohoku University) Andreas Rossberg (Google) Jacques Garrigue (Nagoya University) Matthew Fluet (Rochester Institute of Technology) Robert Harper (Carnegie Mellon University) Yaron Minsky (Jane Street)

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