- Haskell-Cafe - Haskell.org

hasktags and sublime?
by Edsko de Vries 23 May '14

23 May '14

Hey, has anyone has much luck with hasktags and sublime (3, OSX)? If I create the tags file with hasktags -c it complains that it cannot find any relevant tags file, and when I create it with hasktags -e that warning disappears but I can't jump to any definition (it always says that the tag is not found). -E

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OpenGL performance issue on OSX
by Michael Baker 23 May '14

23 May '14

I'm using OpenGLRaw and I'm getting 3 frames per second trying to draw 8000 triangles. When I profile the application, I see that almost all of the time is taken by a call to CGLFlushDrawable, which is apparently OSX's function for swapping the back buffer to the front buffer. Has anyone else run into a problem like this? I seem to recall a thread a while ago about a Haskell specific OpenGL performance issue, but I can't find it now.

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Haskell-cafe] Yesod can't build on 64 bit 7.8.2 Windows
by Stuart Mills 22 May '14

22 May '14

Apparently in going to Mingw 64 the packages "system-fileio" and "unix-compat" no longer compiled because some Windows routines were not available in their expected "names". I reported the issues and John Milikin quickly patched "system-fileio" (thanks John, if you're listening). The unix-compat issue is still outstanding (not sure if it's still being maintained), but I was able to patch it by adding underscores to elements like "snprintf". ( _snprintf works, _stat instead of stat, etc.) These were the same types of changes that worked for system-fileio. Note that this approach may break Win32. The next issue is when linking with yaml (ghc.exe: panic!). This was reported as a GHC bug 2 weeks ago (#9080) by maun, who was trying to build GHCJS. I get the exact same error in building Yesod. Because of Yesod, I think #9080 should be promoted to high priority, and it would be great if someone could bring unix-compat up to date. Thanks Stuart

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using withAnnotations from Graphics.Rendering.Plot.Figure
by Albert Cardona 22 May '14

22 May '14

Hi all, given two Vector and a list of strings, I generate a plot of one vector as a function of the other [1]. At each x,y point, I am trying to place the corresponding string. For the purpose, I zip3 all three sequences, define an annotation function, and invoke it with mapM_ in the context of withAnnotations [2]: withPlot (1, 1) $ do ... let annotation (x, y, label) = text (x + 2, y) (setText label) in withAnnotations $ do mapM_ annotation $ zip3 (toList vx) (toList vy) labels The code above compiles and runs, the plot shows, but no text annotations appear at all. I understand that I am not using the Annote monad correctly: the mapM_ drops every returned value, so the state is not altered. What is the correct way to invoke withAnnotations over a list of (x, y, String) ? Needless to say, I am a beginner in Haskell. Apologies if the above is too trivial. Thanks very much in advance. Albert [1] https://github.com/acardona/haskell-lib/blob/master/CATMAID/Analysis/Graph/… [2] http://hackage.haskell.org/package/plot-0.2.3/docs/Graphics-Rendering-Plot-… -- http://albert.rierol.net http://www.ini.uzh.ch/~acardona/

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instance Alternative (Either [a])
by Corentin Dupont 22 May '14

22 May '14

Hi guys! I'd like to implement the instance in the subject: instance Alternative (Either [a]) However the instance in Control.Monad.Trans.Error.Error gets in the way... I cannot use this one, it works only with Strings. My use case is that the Either handle in the Right a final value, or else in the Left a list of things "left to do" to compute the value. How can I do? Thanks! Corentin

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extending Do notation
by silvio 22 May '14

22 May '14

#The problem > grep -r ">>=" base | head -3 getExecutablePath = _NSGetExecutablePath >>= realpath then peek p_argv >>= peek >>= peekFilePath ... = getFileSystemEncoding >>= \enc -> GHC.withCString enc fp f > grep -r "flip" base | head -3 ... (o,n,[] ) -> return (foldl (flip id) defaultOptions o, n) peekCString s = getForeignEncoding >>= flip GHC.peekCString s peekCStringLen s = getForeignEncoding >>= flip GHC.peekCStringLen s I don't know how often i've seen this one ... >>= flip ... when really we it should have been ... {...} Only because we can't just execute an IO action and fill in the result. And this list doesn't even include examples where the programmer had to resort to making a pointless temp variable just to avoid using too many complicated functions. #The solution > grep -r ">>=" base | head -3 getExecutablePath = _do realpath { _NSGetExecutablePath } then peekFilePath { peek {peek p_argv} } ... = do GHC.withCString {getFileSystemEncoding} fp f > grep -r "flip" base | head -3 ... (o,n,[] ) -> return (foldl (flip id) defaultOptions o, n) -- leave peekCString s = GHC.peekCString {getForeignEncoding} s peekCStringLen s = GHC.peekCStringLen {getForeignEncoding} s I think there is no use of {} in haskell that does not come after a key word but has an expression inside. But it could be some other syntax too. silvio

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Announce: ghc-imported-from-0.2.0.4
by Carlo Hamalainen 22 May '14

22 May '14

Hi, I have released v0.2.0.4 of my utility ghc-imported-from. It lets you quickly jump to the Haddock documentation for a symbol in a Haskell source file. This version has a few bug fixes, is significantly faster, and has better support for cabal sandboxes. Short screencast showing the vim plugin: https://www.youtube.com/watch?v=7yO_VGCWMu8 (make sure it plays in 720p HD) Hackage page: http://hackage.haskell.org/package/ghc-imported-from-0.2.0.4 Vim plugin: https://github.com/carlohamalainen/ghcimportedfrom-vim Cheers, -- Carlo Hamalainen http://carlo-hamalainen.net

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[Haskell] ANNOUNCE: Haskell Communities and Activities Report (26th ed., May 2014)
by Mihai Maruseac 22 May '14

22 May '14

On behalf of all the contributors, we are pleased to announce that the Haskell Communities and Activities Report (26th edition, May 2014) is now available, in PDF and HTML formats: http://www.haskell.org/communities/05-2014/report.pdf http://www.haskell.org/communities/05-2014/html/report.html Many thanks go to all the people that contributed to this report, both directly, by sending in descriptions, and indirectly, by doing all the interesting things that are reported. We hope you will find it as interesting a read as we did. If you have not encountered the Haskell Communities and Activities Reports before, you may like to know that the first of these reports was published in November 2001. Their goal is to improve the communication between the increasingly diverse groups, projects, and individuals working on, with, or inspired by Haskell. The idea behind these reports is simple: Every six months, a call goes out to all of you enjoying Haskell to contribute brief summaries of your own area of work. Many of you respond (eagerly, unprompted, and sometimes in time for the actual deadline) to the call. The editors collect all the contributions into a single report and feed that back to the community. When we try for the next update, six months from now, you might want to report on your own work, project, research area or group as well. So, please put the following into your diaries now: ======================================== End of October 2014: target deadline for contributions to the November 2014 edition of the HC&A Report ======================================== Unfortunately, many Haskellers working on interesting projects are so busy with their work that they seem to have lost the time to follow the Haskell related mailing lists and newsgroups, and have trouble even finding time to report on their work. If you are a member, user or friend of a project so burdened, please find someone willing to make time to report and ask them to "register" with the editors for a simple e-mail reminder in October (you could point us to them as well, and we can then politely ask if they want to contribute, but it might work better if you do the initial asking). Of course, they will still have to find the ten to fifteen minutes to draw up their report, but maybe we can increase our coverage of all that is going on in the community. Feel free to circulate this announcement further in order to reach people who might otherwise not see it. Enjoy! Mihai Maruseac and Alejandro Serrano Mena <hcar at haskell.org> -- Mihai Maruseac (MM) "If you don't know, the thing to do is not to get scared, but to learn." -- Atlas Shrugged.

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porting Haskell to Mageia
by Roelof Wobben 22 May '14

22 May '14

Hello, I like to port Haskell to mageia linux. Now I found out that someone has already made a bootstrap package. Now my question is how can I use that one so I can make the full package like fedora has. So a lot of small packages instead of one big package. Roelof

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llvm is generating invalid instructions (problem with autovectorization?)
by Mike Izbicki 22 May '14

22 May '14

I have some code* that is causing llvm to throw a fit. In particular, I get (compiling with GHC 7.8 and llvm 3.4): /tmp/ghc1685_0/ghc1685_5.bc:150324:0: Error: no such instruction: `sarxq %rax,%rbx,%r14' Similar errors get repeated several thousand times, and it's always a sarxq instruction. Now, my code doesn't use any of the simd primops, so the sarxq must be coming from llvm's autovectorization. Is it possible that somehow GHC's output bytecode could be responsible, or is the problem more likely with llvm proper? Is there any way I can force GHC to pass flags to llvm so I can experiment with different settings? Another clue that the cause might be in llvm's autovectorization is that when I compile with llvm 3.0 (which does not support autovectorization), there are no error messages. * I suspect my code is far too complicated for it to shed any light on this question, but it's available at: https://github.com/mikeizbicki/HLearn/tree/dev-7.8/src/examples/hlearn-allk… If need be, I can create a minimal sample of code that causes the error, but I don't want to go through the trouble if it's not needed.

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Re: [Haskell-cafe] Default implementation of type class member function not working as expected.
by David Banas 21 May '14

21 May '14

That worked, Brandon; thanks! Gurus, I’d still love to understand exactly what I broke, trying to do it the other way. Any thoughts? Thanks, -db On May 21, 2014, at 12:14 AM, haskell-cafe-request(a)haskell.org wrote: > if there's only one definition, then define it > *outside* the typeclass. > >> I have a typeclass, which defines the following two member functions: >> (t is a Rose Tree.) >> >> getCompNodes :: t -> [CompNode a] >> >> getAllCompNodes :: t -> [CompNode a] >> getAllCompNodes t = getCompNodes t >> ++ (concatMap getAllCompNodes (subForest t)) >> The first one must be defined uniquely by each instance, but the second >> never needs a unique definition. >> So, I provided its implementation in the typeclass definition, as shown. >>

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ghc-mod version 4.1.0
by Kazu Yamamoto 21 May '14

21 May '14

Hello guys, I have released ghc-mod version 4.1.0. In this version, ghc-modi provides "info" and "type" commands. This means that you can display types and information of expressions very quickly on Emacs. http://hackage.haskell.org/package/ghc-mod Thanks to GHC's -fdefer-type-errors, "type" and "info" can work even if the file contains type errors. Yay! Of course, you can make use of GHC's hole. For more information, please read the "Types" subsection of the following page: http://mew.org/~kazu/proj/ghc-mod/en/emacs.html Enjoy! --Kazu

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One PhD position is available at the University of Dundee, Scotland
by Ekaterina Komendantskaya 21 May '14

21 May '14

One PhD position is available at the University of Dundee, Scotland. Contact ——————————— Katya Komendantskaya - katya(a)computing.dundee.ac.uk Profile ——————————— The subject of the studentship is programming language semantics and implementation. The specific topic for the studentship will depend on the interests and expertise of the potential candidate. Possible topics are: computational logic, interactive or automated theorem proving, verification, type systems, type inference, logics and applications, program analysis tools. Conditions ——————————— The studentship covers 3 years with a standard stipend of about £13-14k a year plus some eligible travel and consumables. Requirements ——————————— The ideal candidate must show a solid Mathematical or Computer Science background and interest in theoretical and/or practical aspects of declarative programming languages. Previous experience in one or more of the areas described in the profile will be considered a plus. How to apply ——————————— The position is available immediately. Candidates please contact Katya Komendantskaya - katya(a)computing.dundee.ac.uk Dundee and the university ——————————— Dundee is the fourth-largest city in Scotland and it is well connected with Edinburgh, Glasgow and Aberdeen. Dundee is promoted as 'One City, Many Discoveries' in honor of Dundee's history of scientific activities and of the RRS Discovery exploration vessel, which is berthed in the city harbor. Biomedical, technological and video game industries have been important for the development of the city in the last 20 years. The University of Dundee counts about 18.000 students and is situated in the city center. The university is ranked in the World's Top 250 Universities and has been voted one of the best universities in the UK for student experience. http://en.wikipedia.org/wiki/Dundee http://www.dundee.ac.uk The Theory of Computation group ——————————— The Theory of Computation group focuses on research into different areas covering functional programming, program analysis, computational logic, theorem proving, machine learning, constraint programming, graph theory, algorithms and applications like privacy, security, complexity, optimisation, and artificial intelligence. ************************ Ekaterina Komendantskaya Senior Lecturer, Head of PhD Studies Room 1.04, Queen Mother Building School of Computing, University of Dundee Scotland, DD14HN Tel: (+44) 01382384820

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TemplateHaskell forces manual declaration ordering?
by Michael Alan Dorman 21 May '14

21 May '14

Hey, all, While refactoring some code, I moved a newtype declaration, and suddenly the compiler (up-to-date ghc-7.6.3 on Debian) started complaining that it wasn't in scope when I attempted to use it in an ADT. I'm still new to Haskell, so I assumed it was my misunderstanding, and looked for documentation of declaration ordering constraints and couldn't find any. So then I went to make a toy case to demonstrate the problem, and it worked: data Baz = Baz { foo :: Foo, bar :: !(Maybe Bar) } newtype Foo = Foo String newtype Bar = Bar String So I started looking at the differences between that and my real code, and the only thing that seemed at all signficant was that I was using TH to generate some lenses. And sure enough, adding that caused it to fail: {-# LANGUAGE TemplateHaskell #-} import Control.Lens data Baz = Baz { foo :: Foo, bar :: !(Maybe Bar) } makeLenses ''Baz newtype Foo = Foo String newtype Bar = Bar String If you feed this to ghci, you now get: test.hs:3:25: Not in scope: type constructor or class `Foo' test.hs:3:45: Not in scope: type constructor or class `Bar' Perhaps you meant `Baz' (line 3) Wondering if lens was somehow doing something so exotic it was breaking things, I tried aeson's TH support instead: {-# LANGUAGE TemplateHaskell #-} import Data.Aeson data Baz = Baz { foo :: Foo, bar :: !(Maybe Bar) } deriveJSON defaultOptions ''Baz newtype Foo = Foo String newtype Bar = Bar String Exact same error. That said, if I move the splices to the end of the file, everything works: {-# LANGUAGE TemplateHaskell #-} import Data.Aeson data Baz = Baz { foo :: Foo, bar :: !(Maybe Bar) } newtype Foo = Foo String newtype Bar = Bar String deriveJSON defaultOptions ''Baz I looked at the GHC docs on TH, and read the wiki page, and didn't see anything suggesting that this was a known limitation, nor did I see a bug in the known bug list that seemed pertinent. So, I'm wondering if I've found an actual bug, or a known limitation whose documentation should be made more prominent (since it seems to me that it has pretty dramatic implications for program structure), or what? And is there any way around it other than moving all the splices to the end of the source file? Mike.

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Manually control linker options in Cabal build system
by Oleg Durandin 21 May '14

21 May '14

Hi all! Not long ago, I faced with problem building library with Cabal. I'm trying to build simple Haskell project as a shared library for use in MS Visual Studio (yes, I use FFI for this). And I created simple test project: / {-# LANGUAGE ForeignFunctionInterface #-} module GrepWrap where import Foreign import Foreign.C.String import Data.Char printCString :: CString -> IO () printCString s = do ss <- peekCString s putStrLn ss getCStringFromKey :: IO CString getCStringFromKey = do guess <- getLine newCString guess hello :: IO() hello = do putStrLn "Hi there!" foreign export stdcall В В В В hello :: IO () foreign export stdcallВ В printCString :: CString -> IO () foreign export stdcallВ В getCStringFromKey :: IO CString/ Also, I created file for safe initialization with wrappers for hs_init() and hs_exit() calls: /// StartEnd.c #include <Rts.h> extern void __stginit_GrepWrap(void); void HsStart() { int argc = 1; char* argv[] = {"ghcDll", NULL}; // argv must end with NULL // Initialize Haskell runtime char** args = argv; hs_init(&argc, &args); } void HsEnd() { hs_exit(); }/ I compile these files with the next commands: /*> ghc -c GrepWrap.c*//* *//*> ghc -c StartEnd.c*//* *//*> ghc -shared -o grepWrap.dll grepWrap.hs StartEnd.o*/ /Linking grepWrap.dll ...// //Creating library file: grepWrap.dll.a// /// After it, I've got grepWrap.dll and grepWrap.dll.a files. I successfully linked that library with my simple C++ test app, that uses these functions. And I was able to use my Haskell functions in my simple C++ app. Further, I'd like to use Cabal build system for building the same Haskell library filles. My cabal file looks like this: /*name: GrepWrap version: 1.0 synopsis: example shared library for C use build-type: Simple cabal-version: >=1.10 library default-language: Haskell2010 exposed-modules: GrepWrap extra-libraries: HSbase-4.6.0.1, wsock32, user32, shell32, HSinteger-gmp-0.5.0.0, HSghc-prim-0.3.0.0, HSrts, gdi32, winmm c-sources: StartEnd.c extensions: ForeignFunctionInterface build-depends: base >= 4 --ghc-options: "-v"*/ After build, in directory dist/build I got a set of files and among them there are: _/libHSGrepWrap-1.0-ghc7.6.3.dll/_ , ___/libHSGrepWrap-1.0-ghc7.6.3.dll.a/_ and /_GrepWrap_stub.h_/ . I use these files in the same Visual Studio project (of course, I changed names of dependent libraries in dependencies configuration in Visual Studio). Application successfully builds, but after run this app, I've got the next exception: Unhandled exception at 0x6D7905FB (libHSrts-ghc7.6.3.dll) in GrepWrapCabalUseDll.exe: 0xC0000005: Access violation reading location 0x00000000 It occurs, when I call functions from library (but when HsStart() already called). When I use "-v" flag with compilation (using ghc) I saw such linker message log: /*** Linker:// //"C:\Program Files (x86)\Haskell Platform\2013.2.0.0\lib/../mingw/bin/gcc.exe" "-fno-stack-protector" "-Wl,--hash-size=31" "-Wl,--reduce-memory-overheads" "-o" "grepWrap.dll" "-shared" "-Wl,--out-implib=grepWrap.dll.a" "grepWrap.o" "-Wl,--enable-auto-import" "StartEnd.o" "-LC:\Program Files (x86)\Haskell Platform\2013.2.0.0\lib\base-4.6.0.1" "-LC:\Program Files (x86)\Haskell Platform\2013.2.0.0\lib\integer-gmp-0.5.0.0" "-LC:\Program Files (x86)\Haskell Platform\2013.2.0.0\lib\ghc-prim-0.3.0.0" "-LC:\Program Files (x86)\Haskell Platform\2013.2.0.0\lib" "-lHSbase-4.6.0.1" "-lwsock32" "-luser32" "-lshell32" "-lHSinteger-gmp-0.5.0.0" "-lHSghc-prim-0.3.0.0" "-lHSrts" "-lm" "-lwsock32" "-lgdi32" "-lwinmm" "-u" "_ghczmprim_GHCziTypes_Izh_static_info" "-u" "_ghczmprim_GHCziTypes_Czh_static_info" "-u" "_ghczmprim_GHCziTypes_Fzh_static_info" "-u" "_ghczmprim_GHCziTypes_Dzh_static_info" "-u" "_base_GHCziPtr_Ptr_static_info" "-u" "_ghczmprim_GHCziTypes_Wzh_static_info" "-u" "_base_GHCziInt_I8zh_static_info" "-u" "_base_GHCziInt_I16zh_static_info" "-u" "_base_GHCziInt_I32zh_static_info" "-u" "_base_GHCziInt_I64zh_static_info" "-u" "_base_GHCziWord_W8zh_static_info" "-u" "_base_GHCziWord_W16zh_static_info" "-u" "_base_GHCziWord_W32zh_static_info" "-u" "_base_GHCziWord_W64zh_static_info" "-u" "_base_GHCziStable_StablePtr_static_info" "-u" "_ghczmprim_GHCziTypes_Izh_con_info" "-u" "_ghczmprim_GHCziTypes_Czh_con_info" "-u" "_ghczmprim_GHCziTypes_Fzh_con_info" "-u" "_ghczmprim_GHCziTypes_Dzh_con_info" "-u" "_base_GHCziPtr_Ptr_con_info" "-u" "_base_GHCziPtr_FunPtr_con_info" "-u" "_base_GHCziStable_StablePtr_con_info" "-u" "_ghczmprim_GHCziTypes_False_closure" "-u" "_ghczmprim_GHCziTypes_True_closure" "-u" "_base_GHCziPack_unpackCString_closure" "-u" "_base_GHCziIOziException_stackOverflow_closure" "-u" "_base_GHCziIOziException_heapOverflow_closure" "-u" "_base_ControlziExceptionziBase_nonTermination_closure" "-u" "_base_GHCziIOziException_blockedIndefinitelyOnMVar_closure" "-u" "_base_GHCziIOziException_blockedIndefinitelyOnSTM_closure" "-u" "_base_ControlziExceptionziBase_nestedAtomically_closure" "-u" "_base_GHCziWeak_runFinalizzerBatch_closure" "-u" "_base_GHCziTopHandler_flushStdHandles_closure" "-u" "_base_GHCziTopHandler_runIO_closure" "-u" "_base_GHCziTopHandler_runNonIO_closure" "-u" "_base_GHCziConcziIO_ensureIOManagerIsRunning_closure" "-u" "_base_GHCziConcziSync_runSparks_closure" "-u" "_base_GHCziConcziSignal_runHandlers_closure"// //Creating library file: grepWrap.dll.a// //link: done/ But, when I call cabal build with "-v2" option to get build log, I get the following: /> cabal build -v2 I've got the next log: creating dist\build creating dist\build\autogen Building GrepWrap-1.0... Preprocessing library GrepWrap-1.0... Building library... creating dist\build C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe --make -fbuilding-cabal-package -O -odir dist\build -hidir dist\build -stubdir dist\build -i -idist\build -i. -idist\build\autogen -Idist\build\autogen -Idist\build -optP-include -optPdist\build\autogen\cabal_macros.h -package-name GrepWrap-1.0 -hide-all-packages -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 -XHaskell2010 -XForeignFunctionInterface GrepWrap [1 of 1] Compiling GrepWrap ( GrepWrap.hs, dist\build\GrepWrap.o ) C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe --make -fbuilding-cabal-package -O -prof -osuf p_o -hisuf p_hi -odir dist\build -hidir dist\build -stubdir dist\build -i -idist\build -i. -idist\build\autogen -Idist\build\autogen -Idist\build -optP-include -optPdist\build\autogen\cabal_macros.h -package-name GrepWrap-1.0 -hide-all-packages -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 -XHaskell2010 -XForeignFunctionInterface GrepWrap [1 of 1] Compiling GrepWrap ( GrepWrap.hs, dist\build\GrepWrap.p_o ) C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe --make -fbuilding-cabal-package -O -dynamic -fPIC -osuf dyn_o -hisuf dyn_hi -odir dist\build -hidir dist\build -stubdir dist\build -i -idist\build -i. -idist\build\autogen -Idist\build\autogen -Idist\build -optP-include -optPdist\build\autogen\cabal_macros.h -package-name GrepWrap-1.0 -hide-all-packages -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 -XHaskell2010 -XForeignFunctionInterface GrepWrap [1 of 1] Compiling GrepWrap ( GrepWrap.hs, dist\build\GrepWrap.dyn_o ) Building C Sources... creating dist\build C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe -c -prof -odir dist\build -Idist\build -optc-O2 -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 StartEnd.c C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe -c -prof -dynamic -fPIC -osuf dyn_o -odir dist\build -Idist\build -optc-O2 -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 StartEnd.c Linking... C:\Program Files (x86)\Haskell Platform\2013.2.0.0\mingw\bin\ar.exe -r dist\build\libHSGrepWrap-1.0.a dist\build\GrepWrap.o dist\build\StartEnd.o C:\Program Files (x86)\Haskell Platform\2013.2.0.0\mingw\bin\ar.exe: creating dist\build\libHSGrepWrap-1.0.a C:\Program Files (x86)\Haskell Platform\2013.2.0.0\mingw\bin\ar.exe -r dist\build\libHSGrepWrap-1.0_p.a dist\build\GrepWrap.p_o dist\build\StartEnd.o C:\Program Files (x86)\Haskell Platform\2013.2.0.0\mingw\bin\ar.exe: creating dist\build\libHSGrepWrap-1.0_p.a C:\Program Files (x86)\Haskell Platform\2013.2.0.0\mingw\bin\ld.exe -x --hash-size=31 --reduce-memory-overheads -r -o dist\build\HSGrepWrap-1.0.o dist\build\GrepWrap.o dist\build\StartEnd.o C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc.exe -shared -dynamic -lHSbase-4.6.0.1 -lwsock32 -luser32 -lshell32 -lHSinteger-gmp-0.5.0.0 -lHSghc-prim-0.3.0.0 -lHSrts -lgdi32 -lwinmm -package-name GrepWrap-1.0 -no-auto-link-packages -package-db dist\package.conf.inplace -package-id base-4.6.0.1-f0c2cc6dcf0e12bf75312a2e7f354095 dist\build\GrepWrap.dyn_o dist\build\StartEnd.dyn_o -o dist\build\libHSGrepWrap-1.0-ghc7.6.3.dll Creating library file: dist\build\libHSGrepWrap-1.0-ghc7.6.3.dll.a In-place registering GrepWrap-1.0... C:\Program Files (x86)\Haskell Platform\2013.2.0.0\bin\ghc-pkg.exe update - --global --user --package-db=dist\package.conf.inplace/ I'm confused.. Cabal uses a batch of options, it adds multiple options that I can't control. I'd like to control this options. How can I build my Haskell library with Cabal build system as same as building it with simple ghc? I can call ghc manually, but it will be a hard task, when I'll compile library for multiple files. Best regards, Oleg Durandin

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Fwd: extending Do notation
by Miguel Mitrofanov 21 May '14

21 May '14

Forgot to reply the list -------- Пересылаемое сообщение -------- 20.05.2014, 18:26, "Miguel Mitrofanov" <miguelimo38(a)yandex.ru>: 20.05.2014, 18:14, "Kim-Ee Yeoh" <ky3(a)atamo.com>: >> 2) you can't use >>= in an if condition > Could you give an example of the if condition you want an >>= in? Actually, something like do ... if <- checkCondition then doReportSuccess else doReportFailure as well as do ... case <- generateResult of Nothing -> ... Just r -> ... instead of do ... b <- checkCondition if b ... and do ... r <- generateResult case r of ... would be very nice. -------- Завершение пересылаемого сообщения --------

8 13

Default implementation of type class member function not working as expected.
by David Banas 21 May '14

21 May '14

Hi all, I have a typeclass, which defines the following two member functions: (t is a Rose Tree.) getCompNodes :: t -> [CompNode a] getAllCompNodes :: t -> [CompNode a] getAllCompNodes t = getCompNodes t ++ (concatMap getAllCompNodes (subForest t)) The first one must be defined uniquely by each instance, but the second never needs a unique definition. So, I provided its implementation in the typeclass definition, as shown. However, I don’t get the expected behavior! If I copy and paste the code, above, for getAllCompNodes into my instance definition, then I get the expected results. Does anyone know why this is happening? Thanks, -db

2 1

Hackage Down?
by Alexander Solla 21 May '14

21 May '14

I can get to the Hackage website, but I'm having problems doing things with cabal. I have plenty of disk space. I deleted my package cache, since it was complaining about a truncated tar archive for a specific package. Now I'm trying: $ cabal update Downloading the latest package list from hackage.haskell.org cabal: truncated tar archive

1 0

Imports at bottom, why not?
by Thiago Negri 20 May '14

20 May '14

When reading code, I find it quite distracting to have to get past the import list to reach the actual module code, as the import list can be (and often is) quite big. So, why not issue import statements at the bottom of a module file? Likewise, we can use "where" statements to define names used in a function after using them, so they don't distract the reader. I'm against imports at the middle of the file. But I guess being able to issue them at the end of the module could make sense if you want to get the reader straight to the code. A language pragma could be used to select between top imports or bottom imports (can't use both). What do you think? Example: """ {-# LANGUAGE LateImports #-} module Foo where bar :: String bar = "quux" baz :: Fiz baz = mkFiz import Fiz (Fiz, mkFiz) """

13 16

ML Family workshop - Extended deadline
by oleg＠okmij.org 20 May '14

20 May '14

Extended submission deadline: May 23 (Friday), any time zone Four more days to write a 2-page abstract Submissions of demos, case studies and informed opinions are particularly encouraged! Higher-order, Typed, Inferred, Strict: ACM SIGPLAN ML Family Workshop Thursday September 4, 2014, Gothenburg, Sweden (immediately following ICFP and preceding OCaml Users and Developers Workshop) Call For Papers http://okmij.org/ftp/ML/ML14.html ML is a very large family of programming languages that includes Standard ML, OCaml, F#, SML#, Manticore, MetaOCaml, JoCaml, Alice ML, Dependent ML, Flow Caml, and many others. All ML languages, beside the great deal of syntax, share several fundamental traits. They are all higher-order, strict, mostly pure, and typed, with algebraic and other data types. Their type systems inherit from Hindley-Milner. The development of these languages has inspired a significant amount of computer science research and influenced a number of programming languages, including Haskell, Scala and Clojure, as well as Rust, ATS and many others. ML workshops have been held in affiliation with ICFP continuously since 2005. This workshop specifically aims to recognize the entire extended ML family and to provide the forum to present and discuss common issues, both practical (compilation techniques, implementations of concurrency and parallelism, programming for the Web) and theoretical (fancy types, module systems, metaprogramming). The scope of the workshop includes all aspects of the design, semantics, theory, application, implementation, and teaching of the members of the ML family. We also encourage presentations from related languages (such as Scala, Rust, Nemerle, ATS, etc.), to exchange experience of further developing ML ideas. The ML family workshop will be held in close coordination with the OCaml Users and Developers Workshop. Format Since 2010, the ML workshop has adopted an informal model. Presentations are selected from submitted abstracts. There are no published proceedings, so any contributions may be submitted for publication elsewhere. We hope that this format encourages the presentation of exciting (if unpolished) research and deliver a lively workshop atmosphere. 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. The presentations will likely be recorded. Post-conference proceedings The post-proceedings of selected papers from the ML Family and the OCaml Users and Developers workshops will be published in the Electronic Proceedings in Theoretical Computer Science (EPTCS). The Program Committee shall invite interested authors of selected presentations to expand their abstract for inclusion in the proceedings. The submissions are to be reviewed according to the EPTCS standards. Coordination with the OCaml Users and Developers Workshop The OCaml workshop is seen as more practical and is dedicated in significant part to the OCaml community building and the evolution of the OCaml system. In contrast, the ML family workshop is not focused on any language in particular, is more research oriented, and deals with general issues of the ML-style programming and type systems. Yet there is an overlap, which we are keen to explore in various ways. The authors who feel their submission fits both workshops are encouraged to mention it at submission time or contact the Program Chairs. Scope We acknowledge the whole breadth of the ML family and aim to include languages that are closely related (although not by blood), such as Rust, ATS, Scala, Typed Clojure. Those languages have implemented and investigated run-time and type system choices that may be worth considering for OCaml, F# and other ML languages. We also hope that the exposure to the state of the art ML might favorably influence those related languages. Specifically, we seek research presentations on topics including but not limited to * Design: concurrency, distribution and mobility, programming for the web and embedded systems, handling semi-structured data, facilitating interactive programming, higher forms of polymorphism, generic programming, objects * Implementation: compilation techniques, interpreters, type checkers, partial evaluators, runtime systems, garbage collectors, etc. * Type systems: fancy types, inference, effects, overloading, modules, contracts, specifications and assertions, dynamic typing, error reporting, etc. * Applications: case studies, experience reports, pearls, etc. * Environments: libraries, tools, editors, debuggers, cross-language interoperability, functional data structures, etc. * Education: ML and ML-like languages in college or high-school, in general or computer science curriculum. Four kinds of submissions will be accepted: Informed Positions, Research Presentations, Experience Reports and Demos. * Informed Positions: A justified argument for or against a language feature. The argument must be substantiated, either theoretically (e.g., by a demonstration of (un)soundness, an inference algorithm, a complexity analysis), empirically or by a substantial experience. Personal experience is accepted as justification so long as it is extensive and illustrated with concrete examples. * Research Presentations: Research presentations should describe new ideas, experimental results, or significant advances in ML-related projects. We especially encourage presentations that describe work in progress, that outline a future research agenda, or that encourage lively discussion. These presentations should be structured in a way which can be, at least in part, of interest to (advanced) users. * Experience Reports: Users are invited to submit Experience Reports about their use of ML and related languages. These presentations do not need to contain original research but they should tell an interesting story to researchers or other advanced users, such as an innovative or unexpected use of advanced features or a description of the challenges they are facing or attempting to solve. * Demos: Live demonstrations or short 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. (You will need to provide all the hardware and software required for your demo; the workshop organizers are only able to provide a projector.) Important dates Friday May 23 (any time zone): Abstract submission Monday June 30: Author notification Thursday September 4, 2014: ML Family Workshop Submission Submissions should be at most two pages, in PDF format, and printable on US Letter or A4 sized paper. A submission should have a synopsis (2-3 lines) and a body between 1 and 2 pages, in one- or two-column layout. The synopsis should be suitable for inclusion in the workshop program. Submissions must be uploaded to the workshop submission website before the submission deadline (Monday May 19, 2014). For any question concerning the scope of the workshop or the submission process, please contact the program chair. Program Committee Kenichi Asai Ochanomizu University, Japan Matthew Fluet Rochester Institute of Technology, USA Jacques Garrigue Nagoya University, Japan Dave Herman Mozilla, USA Stefan Holdermans Vector Fabrics, Netherlands Oleg Kiselyov (Chair) Monterey, CA, USA Keiko Nakata Tallinn University of Technology, Estonia Didier Remy INRIA Paris-Rocquencourt, France Zhong Shao Yale University, USA Hongwei Xi Boston University, USA

1 0

Making the encoding Haskell package compile with ghc-7.8.2
by José Romildo Malaquias 20 May '14

20 May '14

Hello. I use encodign in a Haskell application and I would like to have it working with ghc-7.8.2. So I am kindly asking to, if possible, update the encoding package[1] to be compilable with ghc-7.8.2. Currently it fails with the messages: [...] * Prepending /usr/lib64/ghc-7.8.2 to LD_LIBRARY_PATH /usr/bin/ghc -package Cabal-1.20.0.0 --make /tmp/portage/dev-haskell/encoding-0.7/work/encoding-0.7/Setup.hs -dynamic -o setup [1 of 8] Compiling Data.Static ( Data/Static.hs, Data/Static.o ) Data/Static.hs:39:28: Couldn't match expected type ‘Bool’ with actual type ‘Int#’ In the expression: eqWord# v (int2Word# 4294967295#) In the expression: if eqWord# v (int2Word# 4294967295#) then Nothing else (if (I# (word2Int# v)) > 1114111 then error (show (I# (word2Int# v)) ++ " is not a valid char (" ++ show (I# i) ++ ")") else Just (chr (I# (word2Int# v)))) /usr/bin/ghc -package Cabal-1.20.0.0 --make /tmp/portage/dev-haskell/encoding-0.7/work/encoding-0.7/Setup.hs -o setup [1 of 8] Compiling Data.Static ( Data/Static.hs, Data/Static.o ) Data/Static.hs:39:28: Couldn't match expected type ‘Bool’ with actual type ‘Int#’ In the expression: eqWord# v (int2Word# 4294967295#) In the expression: if eqWord# v (int2Word# 4294967295#) then Nothing else (if (I# (word2Int# v)) > 1114111 then error (show (I# (word2Int# v)) ++ " is not a valid char (" ++ show (I# i) ++ ")") else Just (chr (I# (word2Int# v)))) Regards, Romildo

1 1

ANNOUNCE: New OpenGL packages
by Sven Panne 19 May '14

19 May '14

New versions of the OpenGL packages are available on Hackage: * OpenGLRaw 1.5.0.0 * GLURaw 1.4.0.1 * OpenGL 2.9.2.0 * GLUT 2.5.1.1 Cheers, S. ====================================================================== Changes in the OpenGLRaw package ====================================================================== * Don't rely on K&R features in CPP, making things easier for Mac/clang users. * Added support for OpenGL 3.2's glGetInteger64i_v and the following extensions, so now all parts of OpenGL 4.1 are supported (plus a few more): APPLE_flush_buffer_range APPLE_vertex_array_object ARB_blend_func_extended ARB_gpu_shader_fp64 ARB_sampler_objects ARB_shader_subroutine ARB_shading_language_include ARB_texture_compression_bptc ARB_texture_rgb10_a2ui ARB_texture_swizzle ARB_transform_feedback2 ARB_vertex_attrib_64bit ARB_vertex_type_2_10_10_10_rev EXT_draw_buffers2 EXT_framebuffer_blit EXT_framebuffer_multisample EXT_gpu_shader4 EXT_packed_stencil_depth EXT_texture_array EXT_texture_compression_rgtc EXT_texture_shared_exponent EXT_transform_feedback * Made naming more consistent: Abgr => ABGR Bgra => BGRA Cmyka => CMYKA Dxt1 => DXT1 Fp => FP Gpu => GPU Latc => LATC Lod => LOD S3tc => S3TC Vtc => VTC ====================================================================== Changes in the GLURaw package ====================================================================== * Don't rely on K&R features in CPP, making things easier for Mac/clang users. ====================================================================== OpenGL 2.9.2.0 ====================================================================== * Added generateMipmap’, a modern version of the deprecated generateMipmap. * Added a few missing IndexedBufferTargets. * indexedBufferSize and indexedBufferStart correctly use 64bit queries now. * Setting bindBufferRange handles Nothing correctly now. * Added missing Eq/Ord/Show instances for a few data types. ====================================================================== Changes in the GLUT package ====================================================================== * Don't rely on K&R features in CPP, making things easier for Mac/clang users. * Added ColorTriange example.

1 0

Haskell Developer - Job Opening - New York, NY
by Ryan Trinkle 19 May '14

19 May '14

skedge.me is seeking a Haskell developer to improve and maintain our Snap-based web application stack. skedge.me is committed to using the best tool for the job throughout our software stack. That includes a mixture of cutting-edge tools like Haskell and the Nix package manager as well as tried-and-true products like PostgreSQL and Linux. Your role will be to find, use, and create tools like these to build a robust and powerful software platform to serve our clients' needs. This job requires that you be able to hit the ground running with Haskell. As part of your application, please submit a small to medium sized code sample (approximately 100 to 1000 lines) demonstrating your ability to write clear, concise, and efficient Haskell code, together with a brief English explanation of what the code does, how it works, and how to build and run it. Your Haskell code is our primary consideration in reviewing your application. However, experience with PostgreSQL, Linux, NixOS, web server programming, Varnish, AWS or other similar technologies is a plus. It is also a plus if you are local to the NYC area, as our offices are located in Midtown. To apply, please email me your resume and code sample at ryan(a)skedge.me. Ryan

1 0

Constants in Class definitions - could not deduce
by martin 19 May '14

19 May '14

Hello all, in my attempt to solve a Calendar related problem, I wanted to define Months and Weekdays such that I can increment a value. Unlike the "succ" Funktion in Enum my "inc" function shall circle endlessly. I came up with the following class (Ix a, Enum a) => Incrementable a where from :: a to :: a inc :: a -> a inc x = [from .. to] !! ((1 + index (from, to) x) `mod` rangeSize (from,to)) but GHC complains: /home/martin/projects/haskell/euler/p19.hs:39:65: Could not deduce (Ix a0) arising from a use of `rangeSize' from the context (Incrementable a) I suppose this is because GHC does not know that I want "to" and "from" to be taken from the same instance as x. If I replace the signature of "from" by "a -> a" and implement it by using a function which throws aways its argument, the types become clear and GHC no longer complains. Alternatively I can omit the implementation of "inc" in the class and leave that to the instances. I can easily fix the types in the instances, but this leads to some code duplication. I tried (from::a) to fix the type, but this had no effect. How is this done correctly?

3 3

Conduits vs. lazy byte strings
by Mike Meyer 18 May '14

18 May '14

I'm working on a web app that loads a file, tweaks it a bit, then downloads the results. I'd like for it to use the minimal amount of memory possible, just as good practice. Especially since the tweaking all happens in the first K or so of the file, and the rest of it is passed through untouched. The current version uses a conduit that just reads the data to a sinkLbs to get a lazy bytestring, which is then processed. I think this will have the desired behavior (after all, the bytestring is lazy), but have this itch that says I should be doing the processing in the conduit. Someone want to tell me if I correctly understand things and the itch is just leftover imperative thinking, or the itch is right and I need to fix the code? If you're intersted, you can find the code at https://www.fpcomplete.com/user/mwm/xyzifiy

2 1

Packaging Haskell Environment for Mac App
by Andrew Gibiansky 18 May '14

18 May '14

Hey all, [This is an xpost from Reddit, where the post<http://www.reddit.com/r/haskell/comments/24hct1/packaging_haskell_platform_…>seems not to be showing up for some reason...] I'd like to package the Haskell Platform and GHC (for GHC API) together in one bundle in order to distribute it with a Mac app. (Specifically, I am working on a Mac app for IHaskell <https://github.com/gibiansky/IHaskell>, so beginners can download that to immediately get started playing with Haskell). Does anyone have any experience with this? What's the easiest way to do this? My list of dependencies is fairly long: - Haskell Platform (well, all packages in it) - A few other packages installed via cabal - A native library (libzmq); cabal packages depend on it - Functioning Python > 2.6ish - GHC API My current best idea is to package this all in a Virtualbox VM. I need to run a server that my Mac app client can use, so mount shared folders in the VM so that the VM can read/write to disk and expose some ports from the VM. If this is the best solution, what Linux distro would you suggest to use in the VM? I'd want something very lightweight. I've also considered using Docker somehow, as IHaskell is already packaged with a Dockerfile. However, I'm not sure how I'd package docker so that its all doable via a single Mac app install. Ideas? Suggestions? Thanks! I know this isn't *directly* related to Haskell, but I'm hoping someone here has experience packaging Haskell applications. -- Andrew Gibiansky

4 5

System.Process and -threaded
by Karsten Gebbert 18 May '14

18 May '14

Hello, I'm writing a little networking wrapper around a sub-process (mplayer -idle -slave) and I'm running into some issues with the System.Process API. This is the program: > module Main where > > import System.IO > import System.Process > import Network.Socket hiding (recv) > import Network.Socket.ByteString > import Control.Concurrent > import qualified Data.ByteString.Char8 as C > > -- WARNING: when compiled with -threaded, this program is likely not going > -- to work. As soon as one writes to the stdin of the forked process, it > -- zombifies and any other command with crash this program. > > main = withSocketsDo $ do > -- network stuff > addrinfos <- getAddrInfo Nothing (Just "localhost") (Just "4000") > let serveraddr = head addrinfos > sock <- socket (addrFamily serveraddr) Stream defaultProtocol > bindSocket sock (addrAddress serveraddr) > listen sock 1 > > -- mplayer > (hand,o,e,pid) <- runInteractiveProcess "mplayer" ["-fs", "-idle", "-slave"] Nothing Nothing > hSetBinaryMode hand False > hSetBuffering hand LineBuffering > > putStrLn "listening for commands" > loop sock hand > > -- closing everything down > sClose sock > terminateProcess pid > waitForProcess pid > return () > > loop sock hand = do > (conn, _) <- accept sock > str <- recv conn 2048 > > putStr $ "received: " ++ C.unpack str > > -- write command to handler > hPutStr hand $ C.unpack str > > sClose conn > loop sock hand When compile with -threaded, the mplayer process gets zombified and hangs until I shut down the program. When compiled with non-threaded RTS (thats whats its called, correct?) I can successfully send a few commands, but then mplayer freezes. When I strace mplayer, this error is what it gets stuck on. ioctl(0, TIOCGWINSZ, 0x7fff2897a070) = -1 ENOTTY (Inappropriate ioctl for device) Apparently that means I'm trying to communicate with it as though it were a type writer. How fitting :) The commands are all simple strings as docs here: http://www.mplayerhq.hu/DOCS/tech/slave.txt My questions are these: is there anything I need to take care of when handling sub-processes like this, specifically while writing to stdin of the process, and with particular regard to -threaded? Does anybody spot a problem or something I'm overlooking when handling processes like this? I have been reading the API docs, but found no mention of potential caveats pertaining to -threaded. Thanks! k ✉ k(a)ioctl.it ☎ +49(0)176 / 61995110

3 4

Status of efl-haskell?
by José Romildo Malaquias 18 May '14

18 May '14

Hello. I am interested in the project efl-haskell[1] a Haskell library that provides an interface to EFL (Enlightenment Foundation Libraries) and elementary (widget toolkit)[2]. The git repository[3] has seen almost no activity. It has been created and populated on Dec 2012 and has just a workaround update on Jan 2013. Is the project still being developed? [1] https://bitbucket.org/arrowdodger/efl-haskell [2] http://enlightenment.org/ [3] https://bitbucket.org/arrowdodger/efl-haskell Romildo

2 1

Was directed here for help with why ghc is failing to find mtl.
by Haskell Beginner 17 May '14

17 May '14

This is the error message which started it all off: http://lpaste.net/104242 Then the following conversation happened: ============================================================================== --- JPMoresmau ------ First package to fail is exceptions. Just open a console and type in cabal install exceptions EclipseFP tries to put some parallel install flags that may make the errors less visible (a Cabal thing, not an EclipseFP thing). I really don't like the look of getting warnings in c code, though... --- haskell_beginner ------ $ cabal install exceptions Resolving dependencies... Configuring exceptions-0.6.1... /var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/5187.c:1:12: warning: control reaches end of non-void function [-Wreturn-type] int foo() {} ^ 1 warning generated. Building exceptions-0.6.1... Preprocessing library exceptions-0.6.1... <command line>: cannot satisfy -package-id mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62 (use -v for more information) Failed to install exceptions-0.6.1 cabal: Error: some packages failed to install: exceptions-0.6.1 failed during the building phase. The exception was: ExitFailure 1 $ What flags can I add to that to get a better error message? EDIT TO ADD: Again if there is another layer automatically adding flags to the above command, I know nothing about it. This includes if Haskell or cabal uses a config file. I am on a — to my knowledge — completely stock install of Haskell for Mac OS. --- JPMoresmau ------ cabal install -v exceptions May give more info about why the mtl package cannot be satisfied when it seems to have been installed. --- haskell_beginner ------ $ cabal install -v exceptions Reading available packages... Choosing modular solver. Resolving dependencies... Ready to install exceptions-0.6.1 Waiting for install task to finish... Extracting /Users/person/Library/Haskell/repo-cache/ hackage.haskell.org/exceptions/0.6.1/exceptions-0.6.1.tar.gz to /var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/exceptions-0.6.1-5256... Updating exceptions.cabal with the latest revision from the index. Configuring exceptions-0.6.1... Dependency base ==4.6.0.1: using base-4.6.0.1 Dependency mtl ==2.1.2: using mtl-2.1.2 Dependency transformers ==0.3.0.0: using transformers-0.3.0.0 /var/folders/3r/gvk584k50jb253024p4wxy3r0000gn/T/5256.c:1:12: warning: control reaches end of non-void function [-Wreturn-type] int foo() {} ^ 1 warning generated. Using Cabal-1.16.0 compiled by ghc-7.6 Using compiler: ghc-7.6.3 Using install prefix: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1 Binaries installed in: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/bin Libraries installed in: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/lib Private binaries installed in: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/libexec Data files installed in: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/share Documentation installed in: /Users/person/Library/Haskell/ghc-7.6.3/lib/exceptions-0.6.1/doc Using alex version 3.0.5 found on system at: /usr/bin/alex Using ar found on system at: /usr/bin/ar No c2hs found Using cpphs version 1.18.1 found on system at: /Users/person/Library/Haskell/bin/cpphs No ffihugs found Using gcc version 4.2.1 found on system at: /usr/bin/gcc Using ghc version 7.6.3 found on system at: /usr/bin/ghc Using ghc-pkg version 7.6.3 found on system at: /usr/bin/ghc-pkg No greencard found Using haddock version 2.13.2 found on system at: /usr/bin/haddock Using happy version 1.18.10 found on system at: /usr/bin/happy No hmake found Using hpc version 0.6 found on system at: /usr/bin/hpc Using hsc2hs version 0.67 found on system at: /usr/bin/hsc2hs Using hscolour version 1.20 found on system at: /Users/person/Library/Haskell/bin/HsColour No hugs found No jhc found Using ld found on system at: /usr/bin/ld No lhc found No lhc-pkg found No nhc98 found No pkg-config found Using ranlib found on system at: /usr/bin/ranlib Using strip found on system at: /usr/bin/strip Using tar found on system at: /usr/bin/tar No uhc found creating dist/build creating dist/build/autogen Building exceptions-0.6.1... Preprocessing library exceptions-0.6.1... Building library... creating dist/build /usr/bin/ghc --make -fbuilding-cabal-package -O -odir dist/build -hidir dist/build -stubdir dist/build -i -idist/build -isrc -idist/build/autogen -Idist/build/autogen -Idist/build -optP-include -optPdist/build/autogen/cabal_macros.h -package-name exceptions-0.6.1 -hide-all-packages -package-db dist/package.conf.inplace -package-id base-4.6.0.1-6c351d70a24d3e96f315cba68f3acf57 -package-id mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62 -package-id transformers-0.3.0.0-ff2bb6ac67241ebb987351a3db564af0 -XHaskell98 Control.Monad.Catch Control.Monad.Catch.Pure -Wall -fwarn-tabs -O2 <command line>: cannot satisfy -package-id mtl-2.1.2-94c72af955e94b8d7b2f359dadd0cb62 (use -v for more information) Failed to install exceptions-0.6.1 World file is already up to date. cabal: Error: some packages failed to install: exceptions-0.6.1 failed during the building phase. The exception was: ExitFailure 1 $ Hope that helps. I don't know what to make of it. :-/ --- JPMoresmau ------ Neither do I! It seems cabal finds a mtl package to use, but when it passes the exact reference of the package (with a trailing hash to indicate the specifics of your install), ghc doesn't find it. At least it's nothing to do with EclipseFP, which is a relief (for me :-p). I suggest you post that to the Haskell-Cafe mailing list if nobody has any clue here. I know that MacOS is a bit weird sometimes with PATH and such. ============================================================================== Thus with the history of this error now told (TL;DR: read JPMoresmau's last comment above), the question I pose to this mailing list is: Why is ghc failing to find mtl? Thanks, ~Haskell Beginner

2 1

Research position "Coalgebraic Logic Programming for Type Inference"
by Ekaterina Komendantskaya 17 May '14

17 May '14

We have a fixed-term position at the School of Computing, Dundee for a postdoctoral researcher to work on the project Coalgebraic Logic Programming for Type Inference: a new generation of languages for parallelism and corecursion. More details are available below and at http://staff.computing.dundee.ac.uk/katya/CoALP/ For further inquiries please email me: Katya Komendantskaya <katya(a)computing.dundee.ac.uk> School of Computing University of Dundee Postdoctoral Researcher in Coalgebraic Logic Programming for Type Inference Fixed-term position for 2 years (extension possible). Start date: between 1 July 2014 and 1 October 2014; Salary scale: between £29,837 and £33,5562 per annum. Closing Date for applications: 16 June 2014. The School of Computing at the University of Dundee invites applications for a postdoctoral researcher to work on an interdisciplinary project "Coalgebraic Logic Programming for type inference: a new generation of languages for parallelism and corecursion" ( http://staff.computing.dundee.ac.uk/katya/CoALP/) The project spans several subjects, among which are: - -- Computational Logic, - -- (Coalgebraic) Operational semantics, - -- Functional Programming; - -- Logic Programming, - -- Recursion and Corecursion in Programming languages; -- Category Theory, - -- Type Theory; - -- Compilers - -- Parallelism and Concurrency The project is jointly led by Dr E.Komendantskaya, University of Dundee and Dr J.Power, University of Bath. We are looking for a researcher to spend up to 29 months in the Dundee team developing CoALP-based type inference. This will involve close collaboration with the existing group members, as well as interaction with the project partners. Research experience of at least a PhD level in computer science or mathematics is essential, as is some knowledge of either functional programming or automated/interactive theorem provers. ************************************** Project description: The main goal of typing is to prevent the occurrence of execution errors during the running of a program. Milner formalised the idea, showing that ``well-typed programs cannot go wrong''. In practice, type structures provide a fundamental technique of reducing programmer errors. At their strongest, they cover most of the properties of interest to the verification community. A major trend in the development of functional languages is improvement in expressiveness of the underlying type system, e.g., in terms of Dependent Types, Type Classes, Generalised Algebraic Types (GADTs), Dependent Type Classes and Canonical Structures. Milner-style decidable type inference does not always suffice for such extensions (e.g. the principal type may no longer exist), and deciding well-typedness sometimes requires computation additional to compile-time type inference. Implementations of new type inference algorithms include a variety of first-order decision procedures, notably Unification and Logic Programming (LP), Constraint LP, LP embedded into interactive tactics (Coq's eauto), and LP supplemented by rewriting. A second major trend is parallelism: the absence of side-effects makes it easy to evaluate sub-expressions in parallel. Powerful abstraction mechanisms of function composition and higher-order functions play important roles in parallelisation. Three major parallel languages are Eden (explicit parallelism), Parallel ML (implicit parallelism) and Glasgow parallel Haskell (semi-explicit parallelism). Control parallelism in particular distinguishes functional languages. Type inference becomes more sophisticated and takes a bigger role in the overall program development. In this project, we have devloped a new dialect of logic programming -- Coalgebraic Logic Programming (CoALP) that features both extra expressiveness (via corecursion) and parallelism in one algorithm. We propose to use CoALP in place of LP tools currently used in type inference. With the mentioned major developments in Corecursion, Parallelism, and Typeful (functional) programming it has become vital for these disjoint communities to combine their efforts: enriched type theories rely more and more on the new generation of LP languages; coalgebraic semantics has become influential in language design; and parallel dialects of languages have huge potential in applying common techniques across the FP/LP programming paradigm. This project is unique in bringing together local and international collaborators working in the three communities. See http://staff.computing.dundee.ac.uk/katya/CoALP/ for more details. *************************************************************** Ekaterina Komendantskaya Senior Lecturer, Head of PhD Studies Room 1.04, Queen Mother Building School of Computing, University of Dundee Scotland, DD14HN Tel: (+44) 01382384820

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ICFP 2014 Student Research Competition: Call for Submissions
by David Van Horn 17 May '14

17 May '14

====================================================================== CALL FOR SUBMISSION SRC@ICFP 2014 Gothenburg, Sweden 1-3 September 2014 http://www.icfpconference.org/icfp2014/src.html Co-located with the International Conference on Functional Programming (ICFP 2014) ====================================================================== Student Research Competition ------------------------ This year ICFP will host a Student Research Competition where undergraduate and postgraduate students can present posters. The SRC at the ICFP 2014 consists of three rounds: Extended abstract round: All students are encouraged to submit an extended abstract outlining their research (800 words). Poster session at ICFP 2014: Based on the abstracts, a panel of judges will select the most promising entrants to participate in the poster session which will take place at ICFP. Students who make it to this round will be eligible for some travel support to attend the conference. In the poster session, students will have the opportunity to present their work to the judges, who will select three finalists in each category* (graduate/undergraduate) to advance to the next round. ICFP presentation: The last round will consist of an oral presentation at the ICFP to compete for the final awards in each category. Prizes ----- * Both the top three graduate and the top three undergraduate winners will receive prizes of $500, $300, and $200, respectively. * All six winners will receive award medals and a two-year complimentary ACM student membership, including a subscription to ACMâ€™s Digital Library. * The names of the winners will be posted on the SRC web site. * The overall first place winner of the SRC will be invited to participate in the ACM SRC Grand Finals, an on-line round of competitions among the winners of other conference-hosted SRCs. * Grand Finalists and their advisors will be invited to the Annual ACM Awards Banquet for an all-expenses-paid trip, where they will be recognized for their accomplishments along with other prestigious ACM award winners, including the winner of the Turing Award (also known as the Nobel Prize of Computing). * The top three graduate Grand Finalists will receive an additional $500, $300, and $200. Likewise, the top three undergraduate Grand Finalists will receive an additional $500, $300, and $200. All six Grand Finalists will receive Grand Finalist certificates. * The ACM, Microsoft Research, and our industrial partners provide financial support for students attending the SRC. You can find more information about this on the ACM website. Eligibility -------- The SRC is open to both undergraduate (not in a PhD programme) and graduate students (in a PhD programme). Upon submission, entrants must be enrolled as a student at their universities, and are ACM student members. Furthermore, there are some constraints on what kind of work may be submitted. Previously published work: Submissions should consist of original work (not yet accepted for publication). If the work is a continuation of previously published work, the submission should focus on the contribution over what has already been published. We encourage students to see this as an opportunity to get early feedback and exposure for the work they plan to submit to the next ICFP or POPL. Collaborative work: Students are encouraged to submit work they have been conducting in collaboration with others, including advisors, internship mentors, or other students. However, submissions are individual, so they must focus on the contributions of the student. Submission Details --------------- Each submission should include the student authorâ€™s name, institutional affiliation, e-mail address, and postal address; research advisorâ€™s name; ACM student member number; category (undergraduate or graduate); research title; and an extended abstract addressing the following: * Problem and Motivation: Clearly state the problem being addressed and explain the reasons for seeking a solution to this problem. * Background and Related Work: Describe the specialized (but pertinent) background necessary to appreciate the work. Include references to the literature where appropriate, and briefly explain where your work departs from that done by others. * Approach and Uniqueness: Describe your approach in attacking the problem and clearly state how your approach is novel. * Results and Contributions: Clearly show how the results of your work contribute to computer science and explain the significance of those results. The abstract must describe the studentâ€™s individual research and must be authored solely by the student. If the work is collaborative with others and/or part of a larger group project, the abstract should make clear what the studentâ€™s role was and should focus on that portion of the work. The extended abstract must not exceed 800 words and must not be longer than 2 pages. The reference list does not count towards these limits. To submit an abstract, please register through the submission page and follow the instructions. Abstracts submitted after the deadline may be considered at the committee's discretion, but only after decisions have been made on all abstracts submitted before the deadline. If you have any problems, don't hesitate to contact the competition chair. Important Dates ------------- * Deadline for submission: 29 June * Notification of acceptance: 14 July Selection Committee ---------------- Jeremy Gibbons, University of Oxford Andrew Kennedy, Microsoft Research Cambridge Matthieu Sozeau, INRIA Paris Sam Tobin-Hochstadt, Indiana University Meng Wang, Chalmers University of Technology (Chair) Stephanie Weirich, University of Pennsylvania Transport of your poster ------------------- You can either bring your poster on your own to the conference or mail it to the local organizers: Attn.: Meng Wang Chalmers University of Technology Department of Computer Science and Engineering SE-412 96 Göteborg, Sweden If you choose to mail, please make sure that the poster will arrive at the latest on 30th August 2014.

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Parent Modules: Common Functions or Re-Exportation?
by Sacha Sokoloski 17 May '14

17 May '14

So as a relatively long term user of haskell at this point, one issue which I've never found a simple solution to is the one stated in the thread. That is, given modules Foo, Foo.Bar, and Foo.Baz, should Foo reexport Bar and Baz, or should Foo provide common functions for Bar and Baz? In the first case, the common functions would have to be provided by some third module Foo.Util, which for some reason I find unsatisfying, as it means all my my modules have these Util after Util after Util module floating aroudn. My natural tendency is follow the second case, but then of course when it comes to actually using the code that I've written, I no longer have such a nicely exposed interface outside of the particular library. One simply can't eat ones cake and have it too. Maybe this problem is just silly, but perhaps others have always been left feeling ambivalent across similar lines, and have somehow found a pleasant solution for when this particular crossroads is reached? Cheers, - Sacha Sokoloski

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Fwd: Composable events: Applicative and Alternative
by Tikhon Jelvis 17 May '14

17 May '14

Oops, forgot to include the list. ---------- Forwarded message ---------- From: Tikhon Jelvis <tikhon(a)jelv.is> Date: Fri, May 16, 2014 at 12:27 PM Subject: Re: [Haskell-cafe] Composable events: Applicative and Alternative To: Corentin Dupont <corentin.dupont(a)gmail.com> It sounds like you're trying to solve the same problems as FRP. In fact, this was basically the original impetus for FRP: making events (and reactive programs in general) nicely composable. Perhaps you could take a look at how event streams work in frameworks like Reactive-Banana? Reactive-Banana doesn't make its events applicatives, but it's a perfectly reasonable thing to do: there's a great explanation in Conal's "Push-Pull Functional Reactive Programming"[1] in section 2.2.4. On Fri, May 16, 2014 at 12:15 PM, Corentin Dupont <corentin.dupont(a)gmail.com > wrote: > > I created a DSL to manage and create events (see under). It's an instance > of Applicative and Alternative, which make them compose nicely. > The idea is that when an event is firing, I look the corresponding event > in the tree and replace it by its value using Pure. > > For example onInputText will trigger the display of a form with a text > field on the screen, and when the player validates the form, the same > onInputText is searched in the tree by the engine and replaced by the > text value. This is where the difficulty begins: > > --> How to make Event an instance of Eq? How to search and replace > through it? > > The problem is the EventProduct primitive, that forbids to make the DSL an > instance of Eq: > EventProduct :: Event (a -> b) -> Event a -> Event b > > Should I replace it by: > EventProduct :: Event a -> Event b -> Event (a,b) > > But then, bye-bye Applicative/Alternative instances! > How can I make the tree of events searchable/traversable and still > maintain the Applicative instance? > > Thanks!! > Corentin > > > On Sat, May 3, 2014 at 8:02 PM, Corentin Dupont <corentin.dupont(a)gmail.com > > wrote: > >> Hi Cafe!! >> >> For my game Nomyx, I am using events that the player can program. For >> example, the player can register a callback that will be triggered when a >> new player arrives. He can also program some forms (with buttons, >> checkboxes, textboxes...) to appear on the Web GUI. The problem is those >> events are not composable: he has to create and handle them one by one. >> >> So I'm thinking of making those events composable by making them an >> instance of Applicative and Alternative. >> For Applicative, this makes events composable very much like in >> Applicative-Functors and Reform. I can build neat composed events such as >> (full program below): >> >> onInputMyRecord :: Event MyRecord >> onInputMyRecord = MyRecord <$> onInputText <*> onInputCheckbox >> >> For Alternative, I haven't seen any example of it on the net. The idea >> is that the first event that fires is used to build the alternative: >> >> onInputMyAlternative :: Event Bool >> onInputMyAlternative = (True <$ onInputButton) <|> (False <$ >> onInputButton) >> >> Here is an example program: >> >> {-# LANGUAGE GADTs #-} >> >> module ComposableEvents where >> >> import Control.Applicative >> import Data.Time >> import Data.Traversable >> >> type PlayerNumber = Int >> >> data Event a where >> OnInputText :: PlayerNumber -> Event String -- A textbox >> will be created for the player. When filled, this event will fire and >> return the result >> OnInputCheckbox :: PlayerNumber -> Event Bool -- Idem with a >> checkbox >> OnInputButton :: PlayerNumber -> Event () -- Idem with a >> button >> OnTime :: UTCTime -> Event () -- time event >> EventSum :: Event a -> Event a -> Event a -- The first >> event to fire will be returned >> EventProduct :: Event (a -> b) -> Event a -> Event b -- both events >> should fire, and then the result is returned >> Fmap :: (a -> b) -> Event a -> Event b -- transforms >> the value returned by an event. >> Pure :: a -> Event a -- Create a fake >> event. The result is useable with no delay. >> Empty :: Event a -- An event that >> is never fired. >> >> instance Functor Event where >> fmap = Fmap >> >> instance Applicative Event where >> pure = Pure >> (<*>) = EventProduct >> >> instance Alternative Event where >> (<|>) = EventSum >> empty = Empty >> >> onInputText = OnInputText >> onInputCheckbox = OnInputCheckbox >> onInputButton = OnInputButton >> onTime = OnTime >> >> -- A product type >> data MyRecord = MyRecord String Bool >> >> -- A sum type >> data MyAlternative = A | B >> >> -- Using the Applicative instance, we can build a product type from two >> separate event results. >> -- The event callback should be called only when all two events have >> fired. >> onInputMyRecord :: Event MyRecord >> onInputMyRecord = MyRecord <$> onInputText 1 <*> onInputCheckbox 1 >> >> -- other possible implementation (given a monad instance) >> -- onInputMyRecord' = do >> -- s <- onInputText >> -- b <- onInputCheckbox >> -- return $ MyRecord s b >> >> -- Using the Alternative instance, we build a sum type. >> -- The event callback should be called when the first event have fired. >> onInputMyAlternative :: Event MyAlternative >> onInputMyAlternative = (const A <$> onInputButton 1) <|> (const B <$> >> onInputButton 1) >> >> allPlayers = [1 .. 10] >> >> -- Now complex events can be created, such as voting systems: >> voteEvent :: UTCTime -> Event ([Maybe Bool]) >> voteEvent time = sequenceA $ map (singleVote time) allPlayers >> >> singleVote :: UTCTime -> PlayerNumber -> Event (Maybe Bool) >> singleVote timeLimit pn = (Just <$> onInputCheckbox pn) <|> (const >> Nothing <$> onTime timeLimit) >> >> vote :: UTCTime -> Event Bool >> vote timeLimit = unanimity <$> (voteEvent timeLimit) >> >> unanimity :: [Maybe Bool] -> Bool >> unanimity = all (== Just True) >> >> >> --Evaluation >> --evalEvent :: Event a -> State Game a >> --evalEvent = undefined >> >> With this DSL, I can create complex events such as time limited votes >> very neatly... >> There is much left to do for a full implem: the way to register callbacks >> on complex events, the evaluator and the event manager. >> Have you heard about a similar implementation? It seems pretty useful. >> Maybe in FRP frameworks? >> >> Thanks a lot!! >> Corentin >> PS: I copied this example also in >> https://github.com/cdupont/Nomyx-design/blob/master/ComposableEvents.hs. >> > > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >

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Composable events: Applicative and Alternative
by Corentin Dupont 16 May '14

16 May '14

Hi Cafe!! For my game Nomyx, I am using events that the player can program. For example, the player can register a callback that will be triggered when a new player arrives. He can also program some forms (with buttons, checkboxes, textboxes...) to appear on the Web GUI. The problem is those events are not composable: he has to create and handle them one by one. So I'm thinking of making those events composable by making them an instance of Applicative and Alternative. For Applicative, this makes events composable very much like in Applicative-Functors and Reform. I can build neat composed events such as (full program below): onInputMyRecord :: Event MyRecord onInputMyRecord = MyRecord <$> onInputText <*> onInputCheckbox For Alternative, I haven't seen any example of it on the net. The idea is that the first event that fires is used to build the alternative: onInputMyAlternative :: Event Bool onInputMyAlternative = (const True <$> onInputButton) <|> (const False <$> onInputButton) Here is an example program: {-# LANGUAGE GADTs #-} module ComposableEvents where import Control.Applicative import Data.Time import Data.Traversable type PlayerNumber = Int data Event a where OnInputText :: PlayerNumber -> Event String -- A textbox will be created for the player. When filled, this event will fire and return the result OnInputCheckbox :: PlayerNumber -> Event Bool -- Idem with a checkbox OnInputButton :: PlayerNumber -> Event () -- Idem with a button OnTime :: UTCTime -> Event () -- time event EventSum :: Event a -> Event a -> Event a -- The first event to fire will be returned EventProduct :: Event (a -> b) -> Event a -> Event b -- both events should fire, and then the result is returned Fmap :: (a -> b) -> Event a -> Event b -- transforms the value returned by an event. Pure :: a -> Event a -- Create a fake event. The result is useable with no delay. Empty :: Event a -- An event that is never fired. instance Functor Event where fmap = Fmap instance Applicative Event where pure = Pure (<*>) = EventProduct instance Alternative Event where (<|>) = EventSum empty = Empty onInputText = OnInputText onInputCheckbox = OnInputCheckbox onInputButton = OnInputButton onTime = OnTime -- A product type data MyRecord = MyRecord String Bool -- A sum type data MyAlternative = A | B -- Using the Applicative instance, we can build a product type from two separate event results. -- The event callback should be called only when all two events have fired. onInputMyRecord :: Event MyRecord onInputMyRecord = MyRecord <$> onInputText 1 <*> onInputCheckbox 1 -- other possible implementation (given a monad instance) -- onInputMyRecord' = do -- s <- onInputText -- b <- onInputCheckbox -- return $ MyRecord s b -- Using the Alternative instance, we build a sum type. -- The event callback should be called when the first event have fired. onInputMyAlternative :: Event MyAlternative onInputMyAlternative = (const A <$> onInputButton 1) <|> (const B <$> onInputButton 1) allPlayers = [1 .. 10] -- Now complex events can be created, such as voting systems: voteEvent :: UTCTime -> Event ([Maybe Bool]) voteEvent time = sequenceA $ map (singleVote time) allPlayers singleVote :: UTCTime -> PlayerNumber -> Event (Maybe Bool) singleVote timeLimit pn = (Just <$> onInputCheckbox pn) <|> (const Nothing <$> onTime timeLimit) vote :: UTCTime -> Event Bool vote timeLimit = unanimity <$> (voteEvent timeLimit) unanimity :: [Maybe Bool] -> Bool unanimity = all (== Just True) --Evaluation --evalEvent :: Event a -> State Game a --evalEvent = undefined With this DSL, I can create complex events such as time limited votes very neatly... There is much left to do for a full implem: the way to register callbacks on complex events, the evaluator and the event manager. Have you heard about a similar implementation? It seems pretty useful. Maybe in FRP frameworks? Thanks a lot!! Corentin PS: I copied this example also in https://github.com/cdupont/Nomyx-design/blob/master/ComposableEvents.hs.

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Object oriented haskell.
by silvio 16 May '14

16 May '14

Hi Haskell, I've been wondering if (.) is so cool in other languages why can't we make it even cooler in haskell. And went on to implement such a (.) based on multiparameter type classes and type families. type family Output object action class Action object action where (.) :: object -> action -> Output object action I'm not sure if this has been done before like this but i didn't find anything. I used Map as an example, and here is what I ended up with: > :m -Prelude > import Prelude hiding ((.)) > import Object > import Object.Example > import Data.Map hiding (size) > let m = empty . [ 'f' := Just 1, 'o' := Just 2, 'o' := Nothing ] > m fromList [('f',Just 1),('o',Nothing)] > m . 'f' Just 1 > m . size 2 I also have a pretty cool (almost) solution to the name collision problem. Visit the project homepage for a more thorough explanation. https://github.com/yokto/object And to those who gonna hate on me because they like the (.) as function composition I have only this to say. type instance Output (b -> c) (a -> b') = (a -> c) instance (b ~ b') => Action (b -> c) (a -> b') where f . g = f Prelude.. g Have fun, Silvio

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make "cabal repl" run a custom preprocessor before loading
by Markus Läll 15 May '14

15 May '14

Hi Cafe, I'm wondering how to run a custom preprocessor with "cabal repl"? The case is that I have a package with an executable and a library. The executable works fine with "ghc-options: -F -pgmF ./xxx.sh" in its cabal config section, but the library seems to ignore it when I put the same line into the library's section and then run "cabal repl". Also, the substitutions didn't happen when running GHC directly with -F and -pgmF in expression mode (-e). -- Markus Läll

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Get "cabal repl" to dump ghc options?
by Carlo Hamalainen 15 May '14

15 May '14

Hi, The cabal repl command works out a bunch of GHC options. Is there any way to dump these options without actually starting the repl? In particular, things like this: ghcOptPackageDBs = [ GlobalPackageDB , SpecificPackageDB \"/home/carlo/foo/.cabal-sandbox/x86_64-linux-ghc-7.6.3-packages.conf.d\",SpecificPackageDB \"dist/package.conf.inplace\" ] Basically it would be nice to get the contents of replOpts just before this bit of code: https://github.com/haskell/cabal/blob/master/Cabal/Distribution/Simple/GHC.… -- Carlo Hamalainen http://carlo-hamalainen.net

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First call for papers IFL 2014
by publicityifl＠gmail.com 15 May '14

15 May '14

Hello, Please, find below the first call for papers for IFL 2014. Please forward these to anyone you think may be interested. Apologies for any duplicates you may receive. best regards, Jurriaan Hage Publicity Chair of IFL --- CALL FOR PAPERS 26th SYMPOSIUM ON IMPLEMENTATION AND APPLICATION OF FUNCTIONAL LANGUAGES - IFL 2014 NORTHEASTERN UNIVERSITY/BOSTON, USA OCTOBER 1-3, 2014 http://ifl2014.github.io We are pleased to announce that the 26th edition of the IFL series will be held at Northeastern University in Boston, USA. The symposium will be held from 1st to 3rd of October 2014. Scope ----- The goal of the IFL symposia is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. IFL 2014 will be a venue for researchers to present and discuss new ideas and concepts, work in progress, and publication-ripe results related to the implementation and application of functional languages and function-based programming. Following the IFL tradition, IFL 2014 will use a post-symposium review process to produce the formal proceedings. All participants of IFL 2014 are invited to submit either a draft paper or an extended abstract describing work to be presented at the symposium. At no time may work submitted to IFL be simultaneously submitted to other venues; submissions must adhere to ACM SIGPLAN's republication policy: http://www.sigplan.org/Resources/Policies/Republication The submissions will be screened by the program committee chair to make sure they are within the scope of IFL, and will appear in the draft proceedings distributed at the symposium. Submissions appearing in the draft proceedings are not peer-reviewed publications. Hence, publications that appear only in the draft proceedings do not count as publication for the ACM SIGPLAN republication policy. After the symposium, authors will be given the opportunity to incorporate the feedback from discussions at the symposium and will be invited to submit a revised full article for the formal review process. From the revised submissions, the program committee will select papers for the formal proceedings considering their correctness, novelty, originality, relevance, significance, and clarity. Submission Details ------------------ Submission deadline draft papers: September 1 Notification of acceptance for presentation: September 5 Early registration deadline: September 10 Late registration deadline: September 17 Submission deadline for pre-symposium proceedings: September 24 26th IFL Symposium: October 1-3 Submission deadline for post-symposium proceedings: December 15 Notification of acceptance for post-symposium proceedings: January 31 2015 Camera-ready version for post-symposium proceedings: March 15 2015 Prospective authors are encouraged to submit papers or extended abstracts to be published in the draft proceedings and to present them at the symposium. All contributions must be written in English. Papers must adhere to the standard ACM two columns conference format. For the pre-symposium proceedings we adopt a 'weak' page limit of 12 pages. For the post-symposium proceedings the page limit of 12 pages is firm. A suitable document template for LaTeX can be found at: http://www.acm.org/sigs/sigplan/authorInformation.htm Topics ------ IFL welcomes submissions describing practical and theoretical work as well as submissions describing applications and tools in the context of functional programming. If you are not sure whether your work is appropriate for IFL 2014, please contact the PC chair at samth(a)cs.indiana.edu. Topics of interest include, but are not limited to: - language concepts - type systems, type checking, type inferencing - compilation techniques - staged compilation - run-time function specialization - run-time code generation - partial evaluation - (abstract) interpretation - metaprogramming - generic programming - automatic program generation - array processing - concurrent/parallel programming - concurrent/parallel program execution - embedded systems - web applications - (embedded) domain specific languages - security - novel memory management techniques - run-time profiling performance measurements - debugging and tracing - virtual/abstract machine architectures - validation, verification of functional programs - tools and programming techniques - (industrial) applications Peter Landin Prize ------------------ The Peter Landin Prize is awarded to the best paper presented at the symposium every year. The honoured article is selected by the program committee based on the submissions received for the formal review process. The prize carries a cash award equivalent to 150 Euros. Programme committee ------------------- Sam Tobin-Hochstadt, Indiana University (Chair) Rinus Plasmeijer, Radboud University Nijmegen (Co-Chair) Atze Dijkstra, Utrecht University Colin Runciman, University of York Graham Hutton, University of Nottingham Mary Sheeran, Chalmers University of Technology Patricia Johann, Appalachian State University Matthew Fluet, Rochester Institute of Technology Josef Svenningsson, Chalmers University of Technology Malgorzata Biernacka, University of Wroclaw Peter Achten, Radboud Univerity Nijmegen Laura Castro, University of A Corua Hai Paul Liu, Intel Labs Kathryn Gray, Cambridge University Lars Bergstrom, Mozilla Research Lindsey Kuper, Indiana University Nicolas Wu, Oxford T. Stephen Strickland, University of Maryland Xavier Clerc, INRIA Venue ----- The 26th IFL will be held in association with the College of Computer and Information Science at Northeastern University. It can be reached quickly and easily by public transport.

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ANN: fsnotify-0.1
by Roman Cheplyaka 15 May '14

15 May '14

A new version of fsnotify, a cross-platform filesystem notification library, is available. http://hackage.haskell.org/package/fsnotify-0.1.0.1 The main user-visible changes since the last version are: * ability to stop a listening job * ability to set a polling interval (when polling is used) * a couple of small semantic changes (see [changelog] for details) * improved documentation Plus, there was a fair bit of internal refactoring, including a new test suite. [changelog]: https://github.com/haskell-fswatch/hfsnotify/blob/master/CHANGELOG.md There's still a long-standing bug about wrong event types being generated on OS X. We know how to fix it (basically, use kqueue instead of OS X's own API), but I don't have time to do it. So if anyone is interested, help would be welcome! See https://github.com/haskell-fswatch/hfsnotify/issues/36 Thanks to Miguel Mitrofanov for providing access to an OS X host, which was extremely valuable while working on and testing this version. Roman

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case, GADTs, Arrows
by Miguel Mitrofanov 15 May '14

15 May '14

Hi Café! Are there EXACT rules for desugaring "case" construct in Arrow syntax? The documentation says just "The translation is similar to that of if commands". But that can't be right in case of GADTs. For example, let's say we have data A where A :: Show s => s -> A Then the following would work fine: proc () -> do a <- arr A -< "test" case a of A s -> returnA -< show s But if we abstract part of it: b :: (Arrow a, Show s) => a s String b = proc(s) -> returnA -< show s proc() -> do a <- arr A -< "test" case a of A s -> b -< s then it fails. Now, I'm not asking why exactly does it fail. I understand, that type classes are just data types, and, if arrow is fixed, then the real type of "b" would be b :: Show s -> a s String and that can't be combined with something of type a () (Show s, s). So, the second example shouldn't work at all (although the error message could use some improvement). But I'm surprised that the first one does. Another unexpected thing is that it still requires ArrowChoice from the arrow, although there are no binary alternatives here. Therefore, the rules would be quite helpful.

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Reading and writing to handles made with System.Process far too slow
by Mateusz Kowalczyk 13 May '14

13 May '14

Hi, I'm have some business in piping some data and reading some data back out of a socket so I thought that I'd just use the ‘socat’ tool. I went off to System.Process just to find out that reading and writing are taking far too long. I put together a small example which only requires that you have ‘cat’ on your system: {-# LANGUAGE UnicodeSyntax #-} module Uzbl.WithSource where import GHC.IO.Handle ( hPutStr, hGetContents, hSetBuffering , BufferMode(..)) import System.Process ( createProcess, proc , StdStream(CreatePipe), std_out, std_in) gs ∷ IO String gs = do let sp = (proc "cat" []) { std_out = CreatePipe, std_in = CreatePipe } (Just hin, Just hout, _, _) ← createProcess sp -- hSetBuffering hin NoBuffering -- hSetBuffering hout NoBuffering hPutStr hin "Test data" hGetContents hout All this should effectively do is to give you back "Test data". While it *does* do that, it takes far too long. When I run ‘gs’, it will start to (lazily) print the result, printing nothing but opening ‘"’ and then after about 2-3 seconds printing the rest and finishing. If we set buffering on the in-handle (hin) to NoBuffering, we get a slightly different behaviour: pretty much straight away we'll have ‘"Test data’ but then it will wait for the same amount of time to conclude that it's the end of the response. Changing buffering mode on ‘hout’ seems to make no difference. Setting precise number in a BlockBuffering seems to be no improvement and in the actual application I will not know how long the data I'm piping in and out will be. GHC 7.8.2, process-1.2.2.0; I'm running ‘gs’ in GHCi. It seems that if I change the module name to Main, make ‘main = gs >>= putStrLn’, compile the file and run it, it just hangs there! If I add a newline at the end, it will print but the program will not finish. This makes me think that perhaps I should be closing handles somewhere (but if I try inside the function, I get no output, thanks lazy I/O). What I would expect this program to do is to produce same result as ‘print "Test data" | cat’. -- Mateusz K.

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ANNOUNCE: graphviz-2999.17.0.0
by Ivan Lazar Miljenovic 13 May '14

13 May '14

It's taken me over a year, but I'm pleased to announce the latest version of my graph visualisation (via the Graphviz suite of tools) library: http://hackage.haskell.org/package/graphviz You can read all the changes in the Changelog (now linked to from the Hackage page, thanks to the magic of Hackage 2.0! :o), but here are some explicit non-API changes that people should probably be made aware of: * Parsing is currently about 8x slower than previously... because I suggested something two years ago to Malcolm Wallace on what seemed to make polyparse faster; he then released that change as part of polyparse-1.9 a year ago, but now when I do proper benchmarks (rather than the extremely limited ones I did then) I find that my changes actually make it _slower_ in real world usage. Whoops! I'm still using polyparse-1.9 in the hopes that Malcolm is able to release a point-fix release to revert my suggestion. * I'm not sure when it happened, but upstream Graphviz seems to have changed the behaviour of `dot -Tcanon` such that nodes are now interspersed among the edges (and I have been told that it's just a pretty-printer and that it's behaviour should not matter). As such, it is highly recommended that people only use the Generalised representation for parsing unless they're very sure of their input sources. One other change that people might find useful: if I ever again take so long (i.e. 4 major version releases of upstream) to update graphviz such that the various Attribute definitions are no longer valid and fail to parse, there's now (semi-experimental) support for having unrecognised attributes be parsed as an UnknownAttribute instead; but most of the other functions aren't aware of this functionality and thus you might need to duplicate a lot of code if you want to use this with other features like round-tripping. -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com http://IvanMiljenovic.wordpress.com

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FLOPS 2014 call for participation (early registration deadline extended)
by Eijiro Sumii 13 May '14

13 May '14

Dear colleagues, The early registration for FLOPS 2014 (Twelfth International Symposium on Functional and Logic Programming, June 4-6, Kanazawa, Japan) is now open until May 16 Friday, 23:59 JST. - Please register *now* (that is, if you plan to attend) at: http://www.jaist.ac.jp/flops2014/registration.html - Program: http://www.jaist.ac.jp/flops2014/program.html - Invited talks by Ranjit Jhala, Shin-ya Katsumata, and Gabriele Keller: http://www.jaist.ac.jp/flops2014/invited.html - Proceedings to be published as LNCS 8475 - Hyakuman-goku Matsuri Festival http://www.kanazawa-tourism.com/eng/event/event2.php on the day after the symposium (June 7); accommodation can be extended on request basis via the registration site (use the comments field) - More information at: http://www.jaist.ac.jp/flops2014/ Thank you again, FLOPS 2014 Program Co-Chairs Michael Codish and Eijiro Sumii

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Visiting Portland 6/12-6/14 (and Eugene after that)
by Joachim Breitner 13 May '14

13 May '14

Hi, I’ll be visiting a summer school in Eugene¹ in June and my travel plans include two days in Portland, (Tuesday June 12th, afternoon until Saturday, June 14th, shortly past noon). If there anybody wants to meet for keysigning/sightseeing/discussing Haskell/other stuff, let me know. Also, I’d be happy to join any interesting event such as User group meetings, and I can offer to hold a talk (most likely something Haskell related, or general Debian topics). I haven’t book accommodation yet. Useful secret tips are welcome :-) After that I’ll be in Eugene for two weeks and although the schedule is full I’m sure there will be time to meet likewise people in the evening. Or even during the event – I would be surprised if I were there the only haskell-cafe reader that attends the summer school. Greetings, Joachim ¹ http://www.cs.uoregon.edu/research/summerschool/summer14/ -- Joachim “nomeata” Breitner mail(a)joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata(a)joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata(a)debian.org

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Error when trying to use Hashable
by John Ky 12 May '14

12 May '14

Hi Haskell Cafe, I have some code that compiles when running on GHC on OS X, but not on Ubuntu: No instance for (hashable-1.2.1.0:Data.Hashable.Class.GHashable (GHC.Generics.Rep Point)) arising from a use of `hashable-1.2.1.0:Data.Hashable.Class.$gdmhashWithSalt' Possible fix: add an instance declaration for (hashable-1.2.1.0:Data.Hashable.Class.GHashable (GHC.Generics.Rep Point)) In the expression: (hashable-1.2.1.0:Data.Hashable.Class.$gdmhashWithSalt) In an equation for `hashWithSalt': hashWithSalt = (hashable-1.2.1.0:Data.Hashable.Class.$gdmhashWithSalt) In the instance declaration for `Hashable Point' Anyone know what's happening here? Cheers, -John -- <http://www.gocatch.com/> Sydney, Australia <https://www.facebook.com/goCatch> <https://twitter.com/gocatchapp> <http://www.linkedin.com/company/goCatch> <https://itunes.apple.com/au/app/gocatch/id444439909?mt=8> <https://play.google.com/store/apps/details?id=com.gocatchapp.goCatch&hl=en> <http://www.windowsphone.com/en-au/store/app/gocatch/d76b0eb5-bad6-429f-b99e…> <http://appworld.blackberry.com/webstore/content/31917887/>

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what did I do wrong
by Roelof Wobben 12 May '14

12 May '14

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cabal install lens fails
by John Ky 12 May '14

12 May '14

Hi Haskell Cafe, Anyone know about this error? Installing library in /Users/johnky/Library/Haskell/ghc-7.6.3/lib/reflection-1.4/lib Registering reflection-1.4... Installed reflection-1.4 Configuring mtl-2.0.1.0... Building mtl-2.0.1.0... Preprocessing library mtl-2.0.1.0... [ 1 of 21] Compiling Control.Monad.Writer.Class ( Control/Monad/Writer/Class.hs, dist/build/Control/Monad/Writer/Class.o ) [ 2 of 21] Compiling Control.Monad.State.Class ( Control/Monad/State/Class.hs, dist/build/Control/Monad/State/Class.o ) [ 3 of 21] Compiling Control.Monad.Reader.Class ( Control/Monad/Reader/Class.hs, dist/build/Control/Monad/Reader/Class.o ) [ 4 of 21] Compiling Control.Monad.RWS.Class ( Control/Monad/RWS/Class.hs, dist/build/Control/Monad/RWS/Class.o ) [ 5 of 21] Compiling Control.Monad.Identity ( Control/Monad/Identity.hs, dist/build/Control/Monad/Identity.o ) [ 6 of 21] Compiling Control.Monad.Error.Class ( Control/Monad/Error/Class.hs, dist/build/Control/Monad/Error/Class.o ) Control/Monad/Error/Class.hs:93:18: Not in scope: `catch' Failed to install mtl-2.0.1.0 Cheers, -John -- <http://www.gocatch.com/> Sydney, Australia <https://www.facebook.com/goCatch> <https://twitter.com/gocatchapp> <http://www.linkedin.com/company/goCatch> <https://itunes.apple.com/au/app/gocatch/id444439909?mt=8> <https://play.google.com/store/apps/details?id=com.gocatchapp.goCatch&hl=en> <http://www.windowsphone.com/en-au/store/app/gocatch/d76b0eb5-bad6-429f-b99e…> <http://appworld.blackberry.com/webstore/content/31917887/>

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Custome monoid mappend on HashMap and HashSet values
by John Ky 12 May '14

12 May '14

Hello, Does anyone have an example on how I might be able to use monoids to mappend a HashMap Int (HashMap Int Int) together? Cheers, -John -- <http://www.gocatch.com/> Sydney, Australia <https://www.facebook.com/goCatch> <https://twitter.com/gocatchapp> <http://www.linkedin.com/company/goCatch> <https://itunes.apple.com/au/app/gocatch/id444439909?mt=8> <https://play.google.com/store/apps/details?id=com.gocatchapp.goCatch&hl=en> <http://www.windowsphone.com/en-au/store/app/gocatch/d76b0eb5-bad6-429f-b99e…> <http://appworld.blackberry.com/webstore/content/31917887/>

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Re: [Haskell-cafe] [Haskell] ANNOUNCE: jhc-0.8.1
by Henning Thielemann 12 May '14

12 May '14

Am 11.05.2014 22:20, schrieb John Meacham: > After a hiatus, jhc 0.8.1 is released. Could you clarify the current relation between jhc and ajhc. Are they independent from each other, or does ajhc still pull all features from jhc?

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Installation of package text failing installation on ghc 7.6.3
by Victor Miller 12 May '14

12 May '14

I just downloaded the latest Haskell platform (I realize that ghc might not be up-to-date in this) for my macbook. I installed it, which appeared to go without problems. However, when I tried to update the package text, I get the errors below. I suspect that the first error (not recognizing ' in a comment) cascades through the rest. How do you suggest fixing this (other than getting Bryan do drop the apostrophe :-))? Victor Configuring text-1.1.1.2... Building text-1.1.1.2... Preprocessing library text-1.1.1.2... Data/Text.hs:9:52: warning: missing terminating ' character [-Winvalid-pp-token] -- Copyright : (c) 2009, 2010, 2011, 2012 Bryan O'Sullivan, ^ Data/Text.hs:90:12: warning: missing terminating ' character [-Winvalid-pp-token] , foldl' ^ Data/Text.hs:92:13: warning: missing terminating ' character [-Winvalid-pp-token] , foldl1' ^ Data/Text.hs:151:14: warning: missing terminating ' character [-Winvalid-pp-token] --, lines' ^ Data/Text.hs:269:15: warning: missing terminating '"' character [-Winvalid-pp-token] -- character \"�\" (U+FFFD). Functions that perform this ^ Data/Text.hs:271:5: warning: missing terminating '"' character [-Winvalid-pp-token] -- \"Performs replacement on invalid scalar values\". ^ Data/Text.hs:304:12: warning: missing terminating '"' character [-Winvalid-pp-token] -- phrase \"Subject to fusion\". ^ Data/Text.hs:440:3: error: invalid preprocessing directive #-} ^ Data/Text.hs:477:4: error: invalid preprocessing directive #-} ^

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