December 2013 - Haskell-Cafe

ANN: tasty-0.5
by Roman Cheplyaka 10 Dec '13

10 Dec '13

The new version of Tasty, a modern and extensible testing framework for Haskell, is out. The major new feature in this release is resources, described in detail in the article http://ro-che.info/articles/2013-12-10-tasty-resources.html Although I haven't posted here since the very first release of tasty, there have been many small improvements and some new big features, such as resources and ingredients. The core Tasty packages are now part of Stackage, which means that you can use them in FP Haskell Center™ and School of Haskell. It's also great to see third-party packages appearing, which was the main motivation behind Tasty's extensible design: http://hackage.haskell.org/package/tasty-th, by Benno Fünfstück http://hackage.haskell.org/package/tasty-hspec, by Mitchell Rosen http://hackage.haskell.org/package/tasty-ant-xml, by Oliver Charles To learn more about Tasty, please see: http://documentup.com/feuerbach/tasty — the README http://hackage.haskell.org/package/tasty-0.5.1/docs/Test-Tasty.html — the haddock documentation https://github.com/feuerbach/tasty/blob/master/CHANGES.md — the changelog http://ocharles.org.uk/blog/posts/2013-12-03-24-days-of-hackage-tasty.html — this year's «24 days of Hackage» article about Tasty Roman

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Re: [Haskell-cafe] XEventPtr in Xlib?
by EatsKittens 10 Dec '13

10 Dec '13

Hmm, I think I now know how to work with XEventPtr's with allocaXEvent event, what I have now is this: raiseWin :: Win -> IO (); raiseWin w = let { d = disp w; r = root w; xID = xid w; } in do { ctime <- Monad.liftM (\(Time.TOD t _) -> fromIntegral t) Time.getClockTime; atom <- Xlib.Atom.internAtom d "_NET_ACTIVE_WINDOW" True; Xlib.Event.allocaXEvent $ \ePtr -> do { Xlib.Extras.setEventType ePtr XTypes.clientMessage; Xlib.Extras.setClientMessageEvent ePtr xID atom 32 2 ctime; Xlib.Event.sendEvent d r False (Xlib.substructureNotifyMask .|. Xlib.substructureRedirectMask) ePtr; }; }; where root in the Win record is derived from: (root, parent, _) <- Xlib.Extras.queryTree d xid; The code compiles and type checks, it just doesn't... work, it does nothing. Replacing the code with: raiseWin w = System.Process.rawSystem "xdotool" ["windowactivate", show x] >> return () where { x = xid w; } Makes it work without errors, inspecting the code of xdotool makes it reveal to use the "_NET_ACTIVE_WINDOW" client message to the root hole? Any idea what I could be doing wrongly, is this the correct root window? On 10 December 2013 06:22, Brandon Allbery <allbery.b(a)gmail.com> wrote: > On Mon, Dec 9, 2013 at 10:57 PM, EatsKittens < > temporalabstraction(a)gmail.com> wrote: > >> Xlib.Event seems to define the interestingly recursive type data XEvent = >> XEvent (Ptr XEvent) and otherwise give no information about that type. >> > > Anything on the far side of a Ptr is defined by C and accessed via the > FFI. In this case, you're looking for the XEvent structure defined by the C > Xlib and described in X11/X.h (constants) and X11/Xlib.h (structs; note > that there is a separate struct for each event type although they all have > a common preamble). > > You may be better served by the event definitions in > http://xmonad.org/xmonad-docs/X11/Graphics-X11-Xlib-Extras.html which is > a Haskell, instead of FFI, interface. (I pointed to the xmonad copy of the > docs because that's what I already have loaded in a tab, but it's part of > the same X11 binding as Graphics.X11.Xlib.Event.) > > I need this type to send an XEvent message to a window, is this a mistake >> or am I overlooking something in how to use it, or is the idea that the >> only way to make XEvent data is to make it in C and import it from there? >> > > allocaXEvent is defined in Graphics.X11.Xlib.Event, but you need to refer > to the C Xlib definitions and use FFI marshaling to work with it (and may > need to know C type sizes and how the C compiler packs structs on your > system). There's some code in xmonad-contrib which uses that interface to > send custom events. > > -- > brandon s allbery kf8nh sine nomine > associates > allbery.b(a)gmail.com > ballbery(a)sinenomine.net > unix, openafs, kerberos, infrastructure, xmonad > http://sinenomine.net >

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f^n for functional iteration
by Doug McIlroy 10 Dec '13

10 Dec '13

Is there a trick whereby the customary notation f^n for iterated functional composition ((\n f -> foldl (.) id (replicate n f)) n f) can be defined in Haskell? Doug McIlroy

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No instance for (Constructor Main.D1MyData)
by Maarten Faddegon 10 Dec '13

10 Dec '13

Dear list, I try to implement the generic show of section 3.6 from the paper Magelheas et al., "A Generic Deriving Mechanism for Haskell" but run into problems with the Constructor class. If someone could point out what is wrong here I would be most grateful. I import generics: > import GHC.Generics And I define my own "Show" class named "Toonbaar", and a generic version of the class "GToonbaar": > class Toonbaar a where > toon :: a -> String > > default toon :: (Generic a, GToonbaar (Rep a)) => a -> String > toon a = gtoon (from a) > > instance Toonbaar Int where > toon i = show i > > class GToonbaar f where > gtoon :: f a -> String Next I want implement instances of gtoon for the 5 primitive types that are used to by the "from" function to represent data types. Most interisting is the meta-information instance here, where I use the "conName" function. Most of the rest I copied from the serialization example on the wiki: http://www.haskell.org/haskellwiki/GHC.Generics#Complete_working_example > -- | Meta-information (constructor names, etc.) > instance (GToonbaar a, Constructor c) => GToonbaar (M1 i c a) where > gtoon m@(M1 _) = conName m > > -- | Unit: used for constructors without arguments > instance GToonbaar U1 where > gtoon _ = "Unit" > > -- | Constants, additional parameters and recursion of kind * > instance (GToonbaar a, GToonbaar b) => GToonbaar (a :*: b) where > gtoon _ = "Constant" > > > -- | Sums: encode choice between constructors > instance (GToonbaar a, GToonbaar b) => GToonbaar (a :+: b) where > gtoon x = gtoon x > > -- | Products: encode multiple arguments to constructors > instance (Toonbaar a) => GToonbaar (K1 i a) where > gtoon (K1 x) = toon x I define a data type, deriving Generic and make it an instance of Toonbaar. > data MyData = MyInt Int > deriving (Generic) > instance Toonbaar MyData > > main = putStrLn (toon (MyInt 42)) When I try to compile the above, ghc emits the following error: No instance for (Constructor Main.D1MyData) arising from a use of `Main.$gdmtoon' Possible fix: add an instance declaration for (Constructor Main.D1MyData) In the expression: (Main.$gdmtoon) In an equation for `toon': toon = (Main.$gdmtoon) In the instance declaration for `Toonbaar MyData' There are 2 things here that I do not understand: 1. I was under the impression that Constructor can be derived, but this does not seem to be the case. (I tried adding it to the line where I also derive Generic). Is there another way to derive it? 2. Why is the error message referring to D1MyData and not to MyData? And $gdmtoon instead of toon or gtoon? Thanks, Maarten

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[ANN] SFML and SFML-control
by Alfredo Di Napoli 10 Dec '13

10 Dec '13

Hello guys, I will send you the link back to the original Reddit discussion that, for some unfathomable reason is not showing up directly in /r/haskell. http://www.reddit.com/r/haskell/comments/1sjemq/ann_sfml_and_sfmlcontrol/ Feedback appreciated! Alfredo

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Does anyone use ghc-mod with Yesod?
by Carlo Hamalainen 10 Dec '13

10 Dec '13

Hi, I have been using ghc-mod (via ghcmod-vim) recently and it's fantastic but I can't get it to work on one of my Yesod projects. This is what happens on a minimal scaffolded Yesod project: $ yesod init # create project Foo, sqlite, no other options $ cd Foo $ cabal install # builds ok, no issues $ ghc-mod check Handler/Home.hs Handler/Home.hs:0:0:Error:<command line>: cannot satisfy -package yesod-test (use -v for more information) I've reported the error on github [1] but I was wondering if anyone here had a workaround, maybe using cabal-dev or sandboxing or something? Cheers, -- Carlo Hamalainen http://carlo-hamalainen.net [1] https://github.com/kazu-yamamoto/ghc-mod/issues/170

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XEventPtr in Xlib?
by EatsKittens 10 Dec '13

10 Dec '13

Xlib.Event seems to define the interestingly recursive type data XEvent = XEvent (Ptr XEvent) and otherwise give no information about that type. I need this type to send an XEvent message to a window, is this a mistake or am I overlooking something in how to use it, or is the idea that the only way to make XEvent data is to make it in C and import it from there?

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cmm
by Alexander Pakhomov 09 Dec '13

09 Dec '13

Hi. Trying to compile ghc-7.7.20130828 on OpenBSD I got an error: rts/HeapStackCheck.cmm:97:18: parse error on input `[' The code is following: 96 if (HpAlloc <= BLOCK_SIZE 97 && bdescr_link(CurrentNursery) != NULL) { which preprocesses to: if (HpAlloc <= (1<<12) && b0[CurrentNursery+15] != (0::bits64)) { This is the first occurrence of b0 in preprocessed file. I believe that it is due to undefined b0. Command that fails is: "inplace/bin/ghc-stage1" -static -H32m -O -Iincludes -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -package-name rts -dcmm-lint -i -irts -irts/dist/build -irts/dist/build/autogen -Irts/dist/build -Irts/dist/build/autogen -O2 -c rts/HeapStackCheck.cmm -o rts/dist/build/HeapStackCheck.o To preprocess do the following: cpp -O -Iincludes -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -Irts/dist/build -Irts/dist/build/autogen rts/HeapStackCheck.cmm | less Can you please find source of b0 in preprocessed file?

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Call for Participation PEPM 2014 (co-located with POPL 2014)
by Jurriaan Hage 09 Dec '13

09 Dec '13

Dear all, Note the presence of Haskell papers in the program. Hope to see many of you there. best, Jur (co-chair of PEPM 2014) =========== PEPM 2014 =============== ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation http://www.program-transformation.org/PEPM14 January 20-21, 2014 San Diego, CA, USA (Affiliated with POPL 2014) CALL FOR PARTICIPATION IMPORTANT DATES * Hotel reservation deadline: December 21, 2013 * Early registration deadline: December 31, 2013 VENUE PEPM'14 and all POPL'14 affiliated events will take place at the US Grant in San Diego, CA, USA. SCOPE The PEPM Symposium/Workshop series aims at bringing together researchers and practitioners working in the areas of program manipulation, partial evaluation, and program generation. PEPM focuses on techniques, theory, tools, and applications of analysis and manipulation of programs. INVITED TALKS: * Manuel Fahndrich (Microsoft Research, USA) on Lessons from a Web-Based IDE and Runtime * Sven-Bodo Scholz (Heriott-Watt University, Scotland) on Partial Evaluation as Universal Compiler Tool (experiences from the SAC eco system) PROGRAM CHAIRS Wei Ngan Chin (National University of Singapore, Singapore) Jurriaan Hage (Utrecht University, Netherlands) PROGRAM COMMITTEE Evelyne Contejean (LRI, CNRS, Université Paris-Sud, France) Cristina David (University of Oxford, UK) Alain Frisch (LexiFi, France) Ronald Garcia (University of British Columbia, Canada) Zhenjiang Hu (National Institute of Informatics, Japan) Paul H J Kelly (Imperial College, UK) Oleg Kiselyov (Monterey, USA) Naoki Kobayashi (University of Tokyo, Japan) Jens Krinke (University College London, UK) Ryan Newton (University of Indiana, USA) Alberto Pardo (Universidad de la República, Uruguay) Sungwoo Park (Pohang University of Science and Technology, South Korea) Tiark Rompf (Oracle Labs & EPFL, Switzerland) Sukyoung Ryu (KAIST, South Korea) Kostis Sagonas (Uppsala University, Sweden) Max Schaefer (Nanyang Technological University, Singapore) Harald Søndergaard (The University of Melbourne, Australia) Eijiro Sumii (Tohoku University, Japan) Eric Van Wyk (University of Minnesota, USA) Jeremy Yallop (University of Cambridge, UK) PRELIMINARY PROGRAM DAY 1: Monday, January 20th, 2014 ================================== 09:00 - 10:00 Invited Talk =========================== Lessons from a Web-Based IDE and Runtime Manuel Fahndrich 10:30 - 12:00 Meta-Programming ------------------------------- Combinators for Impure yet Hygienic Code Generation Yukiyoshi Kameyama, Oleg Kiselyov, Chung-Chieh Shan Effective Quotation James Cheney, Sam Lindley, Gabriel Radanne, Philip Wadler Compile-time Reflection and Metaprogramming for Java Weiyu Miao, Jeremy Siek 14:00 - 15:25 Bidirectional Transformations -------------------------------------------- Monadic Combinators for "Putback" Style Bidirectional Programming Hugo Pacheco, Zhenjiang Hu and Sebastian Fischer Semantic Bidirectionalization Revisited Meng Wang and Shayan Najd Generating Attribute Grammar-based Bidirectional Transformations from Rewrite Rules Pedro Martins, Joao Paulo Fernandes, Joao Saraiva and Eric Van Wyk 16:00 - 17:00 Static Analysis and Optimization ----------------------------------------------- Optimizing SYB is Easy! Michael D. Adams, Andrew Farmer, Jose Pedro Magalhaes: QEMU/CPC: Static Analysis and CPS Conversion for Safe, Portable, and Efficient Coroutines Gabriel Kerneis, Charlie Shepherd, Stefan Hajnoczi ================================= DAY 2: Tuesday, January 21, 2014 ================================= 09:00 - 10:00 Invited Talk --------------------------- Partial Evaluation as Universal Compiler Tool (experiences from the SAC eco system) Sven-Bodo Scholz 10:30 - 12:00 Program Transformation -------------------------------------- The HERMIT in the Stream Andrew Farmer, Christian Hoener Zu Siederdissen, Andy Gill Type-Changing Rewriting and Semantics-Preserving Transformation Sean Leather, Johan Jeuring, Andres Loeh, Bram Schuur An Operational Semantics for Android Activities Etienne Payet, Fausto Spoto 14:00 - 15:30 Type Systems ---------------------------- Early Detection of Type Errors in C++ Templates Sheng Chen, Martin Erwig Lazy Stateless Incremental Evaluation Machinery for Attribute Grammars Jeroen Bransen, Atze Dijkstra, Doaitse Swierstra Deriving Interpretations of the Gradually-Typed Lambda Calculus. Alvaro Garcia-Perez, Pablo Nogueira, Ilya Sergey 16:00 - 17:20 Program Analysis/Testing ---------------------------------------- Automating Property-based Testing of Evolving Web Services Huiqing Li, Simon Thompson, Pablo Lamela Seijas, Miguel Angel Francisco A Modular and Generic Analysis Server System for Functional Logic Programs Michael Hanus, Fabian Skrlac HIPimm: Verifying Granular Immutability Guarantees Andreea Costea, Asankhaya Sharma, Cristina David

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Is anyone currently working on SDL2 FFI ?
by Ömer Sinan Ağacan 09 Dec '13

09 Dec '13

Hello everyone, I was wondering if anyone is currently working on SDL2 FFI. I really need that library and I'm willing to contribute to the work, but I can't currently spare enough time to start it from scratch(it's very big library). I know we have OpenGL and GLFW bindings and gloss for 2D stuff etc. but for several reasons I want this particular library. (just wanted to make this clear because I presume people point me alternatives otherwise :-) ) Thanks, --- Ömer Sinan Ağacan http://osa1.net

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