- Haskell-Cafe - Haskell.org

Haskell Platform 64 bit
by Philippe Sismondi 30 Nov '11

30 Nov '11

I just tried to install the Haskell Platform 64-bit on OS X Snow Leopard 10.6.8. The install fails with "an error". This is all I see in /var/log/install.log: 11-11-25 6:22:01 PM Installer[53992] The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance. Is it known to be broken? I find something in haskell-cafe archives from last spring about a such a problem, but I don't know where to look for anything more recent. I may be blind, but I cannot see anything in the tickets under "known problems". I have been successfully running the 32-bit version for quite a while, but have begun to run into problems with linking haskell stuff against various 64-bit macports libraries. - Phil -

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Re: [Haskell-cafe] containers-deepseq?
by John Lato 29 Nov '11

29 Nov '11

> Message: 22 > Date: Tue, 29 Nov 2011 12:18:41 +0200 > From: Michael Snoyman <michael(a)snoyman.com> > Subject: Re: [Haskell-cafe] containers-deepseq? > > By the way, this is the part of situation that cabal-src is coming to > solve, and it *is* solved... except that the result is a lot of > re-compiling. How is cabal-src different from cabal-dev? John

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minor refactoring problem
by Martin DeMello 29 Nov '11

29 Nov '11

I have the following functions: makePair :: (String, String) -> IO PairBox parseFile :: String -> [(String, String)] importFile :: Editor -> String -> IO () importFile ed path = do s <- readFile path ps <- mapM (\x -> makePair (x, "")) (lines s) es <- return $ V.fromList ps writeIORef ed es loadFile :: Editor -> String -> IO () loadFile ed path = do s <- readFile path ps <- mapM makePair (parseFile s) es <- return $ V.fromList ps writeIORef ed es The problem is that loadFile and importFile are so similar it seems a shame not to combine them somehow, but anything I can think of doing leaves the code looking more rather than less messy. Any nice ideas? martin

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Re: [Haskell-cafe] minor refactoring problem
by Martin DeMello 29 Nov '11

29 Nov '11

On Tue, Nov 29, 2011 at 2:54 AM, Martin DeMello <martindemello(a)gmail.com> wrote: > On Tue, Nov 29, 2011 at 2:29 AM, Holger Siegel <holgersiegel74(a)yahoo.de> wrote: >> >> fromRawFile, fromSavedFile :: String -> IO [PairBox] >> fromRawFile = mapM (\x -> makePair (x, "")) . lines >> fromSavedFile = mapM makePair . parseFile >> >> setEditor :: Editor -> [PairBox] -> IO () >> setEditor ed = writeIORef ed . V.fromList >> >> importFile, loadFile :: Editor -> String -> IO () >> importFile ed = readfile >=> fromRawFile >=> setEditor >> loadFile ed = readfile >=> fromSavedFile >=> setEditor > > Wow, very nice! First time I've truly grasped what >=> is good for. > I'll need to go see where else I can use it in my code. Quick question: what's the difference between importFile ed = readfile >=> fromRawFile >=> setEditor ed and importFile = readfile >=> fromRawFile >=> setEditor that the former compiles but the latter doesn't? martin > > martin >

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containers-deepseq?
by Michael Snoyman 29 Nov '11

29 Nov '11

Hi all, Since the release of deepseq 1.2, we've had a bit of a problem: when using the newest versions of packages on Hackage, there is no NFData instance available for the containers types. When GHC 7.4 comes out with its newer version of containers, this will be addressed, but we'll still have problems for users of older GHC releases. I'd like to suggest a solution: a new package called containers-deepseq. Using conditional compilation, it will provide an orphans NFData instance for all containers types when deepseq >= 1.2 and containers < 0.5. Packages (e.g., aeson) would then depend on containers-deepseq and simply import the module whenever they rely on the NFData instances. When GHC 7.4 comes out, the package will essentially be a no-op. Does this make sense? Michael

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Overloaded Strings as default
by Daniel Díaz Casanueva 29 Nov '11

29 Nov '11

Hi Cafe, I only feel curious about what would be the consequences of becoming the Overloaded Strings feature (currently, an extension) to be default in Haskell. This is not a proposal. I just want to know what pros and cons there are. Thanks!

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(no subject)
by Willem Obbens 29 Nov '11

29 Nov '11

Hello, I get this error when I try to derive an instance of the Show typeclass: Abc.hs:21:60: Couldn't match expected type `Vector' with actual type `[Point]' In the first argument of `show'', namely `xs' In the second argument of `(++)', namely `show' xs' In the second argument of `(++)', namely `", " ++ show' xs'Failed, modules loaded: none. Here's the faulty code: newtype Point = Point Intinstance Show Point where show (Point a) = [chr $ a + 48] data Vector = Vector [Point]instance Show Vector where show (Vector ys) = let show' (Vector [z]) = show z show' (Vector (x:xs)) = show x ++ ", " ++ show' xs show' (Vector []) = [] in "(" ++ show' ys ++ ")" What I'm trying to do, is to print out a vector like "Vector [Point 1, Point 2, Point 3]" as "(1, 2, 3)".My question is: what should I change in order to make it work? Best regards, William

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Built-in LLVM exception handling
by Gregory Crosswhite 29 Nov '11

29 Nov '11

Purely out of curiosity, would it be more efficient for GHC to use the new built-in exception handling instructions in LLVM? http://blog.llvm.org/2011/11/llvm-30-exception-handling-redesign.html Cheers, Greg

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Drawing charts over a lot of data
by Eugene Kirpichov 28 Nov '11

28 Nov '11

Hi cafe, Are there any (possibly unfinished?) libraries dedicated to drawing charts over large amounts of data? I mean, such amounts that you don't want to store the whole set of input data in memory and instead you prefer to do one or a few passes over the input, calling the library's drawing functions for each data point. I'm currently using the excellent Chart package http://hackage.haskell.org/package/Chart , but it seems to require quite a bit of work to become usable in this mode (I haven't looked really deep yet). So, I'd be happy if someone pointed me to an existing package (I didn't find one on hackage) or if someone expressed interest in making Chart avoid having the whole input in memory. -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

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PADL 2012 Call for Participation
by Claudio Russo 28 Nov '11

28 Nov '11

Call for Participation ====================== 14th International Symposium on Practical Aspects of Declarative Languages (PADL 2012) http://research.microsoft.com/~crusso/padl12 Philadelphia, Pennsylvania, USA, January 23-24, 2012 Co-located with ACM POPL'12 You are cordially invited to PADL'12. PADL is a forum for researchers and practitioners to present original work emphasizing novel applications and implementation techniques for all forms of declarative concepts, including functional, logic and constraints. PADL'12 is sponsored by Association for Logic Programming with cooperation of ACM SIGPLAN and support by Microsoft Research. Registration ============ To register for PADL'12, please follow the instructions at: https://regmaster3.com/2012conf/POPL12/register.php The early registration deadline is December 24, 2011. The registration fee will cover a copy of the symposium proceedings, refreshments, and an informal dinner. Hotel Information ================= PADL will be co-located with POPL at the Sheraton Society Hill Hotel in Philadelphia. Please visit POPL's web site to make reservations at the special conference rate. Program ======= The symposium will include invited talks by Boon Thau Loo and Don Stewart, and 19 technical papers selected from 41 submissions. The preliminary program is as follows: Invited Talk (9:00-10:00) * Boon Thau Loo Recent Advances in Declarative Networking Break (10:00-10:30) Session 1: Applications (10:30-12:00) * Mayer Goldberg and Guy Wiener A Declarative Approach for Software Modeling * Sergio Antoy and Michael Hanus Contracts and Specifications for Functional Logic Programming * Pedro M. Martins, Julie A. McCann and Susan Eisenbach The Environment as an Argument Lunch (not provided) (12:00-13:30) Session 2: Logic Programming (13:30-15:30) * Yuliya Lierler, Shaden Smith, Mirek Truszczynski and Alex Westlund Weighted-Sequence Problem: ASP vs CASP and Declarative vs Problem-Oriented Solving * Marcello Balduccini and Yuliya Lierler Practical and Methodological Aspects of the Use of Cutting-Edge ASP Tools * Christian Theil Have and Henning Christiansen Efficient tabling of structured data using indexing and program transformation * Dario Campagna, Beata Sarna-Starosta and Tom Schrijvers Optimizing Inequality Joins in Datalog with Approximated Constraint Propagation Break (15:30-16:00) Session 3: Parallelism and Concurrency (16:00-17:30) * Elvira Albert, Puri Arenas and Miguel Gomez-Zamalloa Symbolic Execution of Concurrent Objects in CLP * Pablo Chico De GuzmÃ¡n, Amadeo Casas, Manuel Carro and Manuel Hermenegildo A Segment-Swapping Approach for Executing Trapped Computations * Michael Lesniak Palovca: Describing and Executing Graph Algorithms in Haskell Informal PADL Dinner (Place: TBA) Tuesday, January 24, 2012 Breakfast (8:00-9:00) Invited Talk (9:00-10:00) * Don Stewart Make Things Now! Pragmatic Functional Programming in Haskell Break (10:00-10:30) Session 4: Domain Specific Languages I (10:30-12:00) * Kenny Zhu, Kathleen Fisher and David Walker LearnPADS++: Incremental Inference of Ad Hoc Data Formats * Jeroen Bransen, Arie Middelkoop, Atze Dijkstra and S. Doaitse Swierstra The Kennedy-Warren algorithm revisited: ordering Attribute Grammars * Nicholas Coleman Distributed Policy Specification and Interpretation with Classified Advertisements Lunch (not provided) (12:00-13:30) Session 5: Domain Specific Languages II (13:30-15:30) * Andy Gill and Bowe Neuenschwander Handshaking in Kansas Lava using Patch Logic * Daniel Winograd-Cort, Hai Liu and Paul Hudak Virtualizing Real-World Objects in FRP * Edwin Brady and Kevin Hammond Resource-safe Systems Programming with Embedded Domain Specific Languages * David Broman and Henrik Nilsson Node-Based Connection Semantics for Equation-Based Object-Oriented Modeling Languages Break (15:30-16:00) Session 6: Numerics (16:00-17:00) * Paul Tarau A Declarative Specification of Tree-based Symbolic Arithmetic Computations * Vincent St-Amour, Sam Tobin-Hochstadt, Matthew Flatt and Matthias Felleisen Typing the Numeric Tower

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