- Haskell-Cafe - Haskell.org

HipmunkPlayground compile error
by Andrew Pennebaker 28 Apr '11

28 Apr '11

$ system_profiler SPSoftwareDataType | grep "System Version" System Version: Mac OS X 10.6.7 (10J869) $ ghc --version The Glorious Glasgow Haskell Compilation System, version 7.0.2 $ cabal --version cabal-install version 0.10.2 using version 1.10.1.0 of the Cabal library $ cabal install hipmunkplayground ... Updating documentation index /Users/andrew/Library/Haskell/doc/index.html cabal: Error: some packages failed to install: GLFW-0.4.2 failed during the building phase. The exception was: ExitFailure 1 HipmunkPlayground-5.2.0.3 depends on GLFW-0.4.2 which failed to install. Cheers, Andrew Pennebaker www.yellosoft.us

3 5

GHC repositories
by Andrew Pennebaker 28 Apr '11

28 Apr '11

Now that GHC has a git repository<http://hackage.haskell.org/trac/ghc/wiki/Repositories>, could that change be reflected in the docs<http://www.haskell.org/ghc/download> ? It's hard to work with folks on Trac to debug GHC when I can't find the latest version (changesets are now git, not svn). Cheers, Andrew Pennebaker www.yellosoft.us

1 0

Haskell Weekly News: Issue 179
by Daniel Santa Cruz 28 Apr '11

28 Apr '11

Welcome to issue 179 of the HWN, a newsletter covering developments in the Haskell community. This release covers the week of April 16 to 23, 2011. Announcements Alex Mason announced (http://goo.gl/2qtyM) the second annual Australian Haskell Hackathon to be heald from Friday July 8th to Sunday July 10th, at the UNSW's Computer Science building in Sydney. Come share with your fellow Australasian Haskellers! "The Hac" team invited us (http://goo.gl/8EQfI) to HacPhi 2011, a Haskell hackathon/get-together to be held July 29 to 31 at the University of Pennsylvania, in Philadelphia. Daniel Wagner wanted to stress that "everyone is welcome--you do not have to be a Haskell guru. Helping hack on someone else's project could be a great way to increase your Haskell-fu." Robert Clausecker asked "Is Hugs dead?" (http://goo.gl/639dC) Sad to see projects of this sort fade into the past. Quotes of the Week * copumpkin: THE POWER OF MIXFIX COMPELS YOU (to not use it much) Top Reddit Stories * Why Darcs users care about consistency Domain: koweycode.blogspot.com, Score: 59, Comments: 3 On Reddit: http://goo.gl/oBU0r Original: http://goo.gl/lnUCU * Review: Learn You a Haskell for Great Good! Domain: jerf.org, Score: 57, Comments: 15 On Reddit: http://goo.gl/BjJq7 Original: http://goo.gl/P7u3x * The Haskell Heap : Inside P4 Domain: blog.ezyang.com, Score: 37, Comments: 3 On Reddit: http://goo.gl/EoV5D Original: http://goo.gl/ropku * First-class modules for Haskell : Shields and Peyton Jones, 2001 :: PDF Domain: research.microsoft.com, Score: 27, Comments: 1 On Reddit: http://goo.gl/7renV Original: http://goo.gl/7lHV4 * Darcs hacking sprint 6 report Domain: blog.darcs.net, Score: 27, Comments: 13 On Reddit: http://goo.gl/ljO1O Original: http://goo.gl/xRr6r * Ugly memoization Domain: augustss.blogspot.com, Score: 25, Comments: 8 On Reddit: http://goo.gl/D6FoV Original: http://goo.gl/IUL1M * Monoids for Maybe Domain: byorgey.wordpress.com, Score: 23, Comments: 2 On Reddit: http://goo.gl/yVU7O Original: https://byorgey.wordpress.com/2011/04/18/monoids-for-maybe/ * Don't forget to think about GC flags when doing performance tuning Domain: stackoverflow.com, Score: 20, Comments: 3 On Reddit: http://goo.gl/6xzEj Original: http://goo.gl/Xwkro * Haskell videos on video.google.com, which shuts down for good on April 29th 2011 Domain: google.com, Score: 20, Comments: 5 On Reddit: http://goo.gl/MizlZ Original: http://goo.gl/CxnBK * Evaluation on the Haskell Heap Domain: blog.ezyang.com, Score: 20, Comments: 2 On Reddit: http://goo.gl/EX5aE Original: http://goo.gl/cU7Nt Top StackOverflow Questions * What are the primary theoretical difficulties with adding ML-style modules to Haskell? votes: 27, answers: 3 Read on SO: http://goo.gl/8An0y * Optimizing numerical array performance in Haskell votes: 25, answers: 1 Read on SO: http://goo.gl/ykzlV * lenses, fclabels, data-accessor - which library for structure access and mutation is better votes: 17, answers: 1 Read on SO: http://goo.gl/c74uO * In Haskell performing 'and' and 'or' for boolean functions votes: 15, answers: 5 Read on SO: http://goo.gl/0U5pI * Automatic memoizing in functional programming languages votes: 11, answers: 4 Read on SO: http://goo.gl/hg8Ei * Alternative implementations of Haskell's standard library type classes votes: 9, answers: 3 Read on SO: http://goo.gl/LDp9u * Scheme vs Haskell for an Introduction to Functional Programming? [migrated] votes: 8, answers: 0 Read on SO: http://goo.gl/lbeX3 * Writing loops for interactive IO: problems with do-notation and layout votes: 5, answers: 1 Read on SO: http://goo.gl/HVRrR * Python-"is"-like equality operator for Haskell/GHC votes: 5, answers: 4 Read on SO: http://goo.gl/7Z4mA * Optimising a Haskell XML parser votes: 5, answers: 1 Read on SO: http://goo.gl/fsqqw About the Haskell Weekly News To help create new editions of this newsletter, please send stories to dstcruz(a)gmail.com. Until next time, Daniel Santa Cruz

1 0

Good reads?
by Christopher Svanefalk 27 Apr '11

27 Apr '11

[I originally posted this over in haskell-beginners. However, since this list has a lot more traffic, and I am not sure how many people read both lists, I thought I would post here as well. I apologize for the doublepost! Just want to make sure I can get some replies from the great people here who might not read the beginners list] Hey all, I have mostly been brought in imperative/OOP languages. In connection with my college studies, however, I have taken great interest in the functional paradigm, and would very much like to dig deeper into it. I am currently reading through Peyton-Jones "Haskell: The Craft of Functional Programming" (2nd ed.), as well as a great paper published by one of my professors (http://www.cse.chalmers.se/~rjmh/Papers/whyfp.html) However, what other works, in your opinions, should I look into to get a more complete understanding of functional programming? Thanks in advance! Chris

5 6

REMINDER: Haskell Communities and Activities Report, May 2011 edition
by Janis Voigtländer 27 Apr '11

27 Apr '11

Dear all, It is not yet too late to contribute to the 20th edition of the ================================================================ Haskell Communities & Activities Report http://tinyurl.com/haskcar Submission deadline: this weekend (please send your contributions to hcar at haskell.org, in plain text or LaTeX format) ================================================================ If you haven't already, please write an entry for your new project or update your old entry. More information can be found in the original Call for Contributions at http://www.haskell.org/pipermail/haskell/2011-April/022720.html I look forward to your contributions, Janis (current editor) -- Jun.-Prof. Dr. Janis Voigtländer http://www.iai.uni-bonn.de/~jv/ mailto:jv@iai.uni-bonn.de

1 0

[GSoC] Text/UTF-8: Call for Benchmarks
by Jasper Van der Jeugt 27 Apr '11

27 Apr '11

Hello all, I'm very glad that I have been accepted again this year for the Google Summer of Code [1] program for haskell.org. My project aims to improve the text [2] library by converting it to internally use UTF-8 instead of UTF-16. UTF-8 and UTF-16 both have advantages and disadvantages, which actually makes it a pretty complicated choice. I've written about this a little in my [3] (especially see Tom Harper's master dissertation if you're interested in the subject). To support a decision here on UTF-8 vs. UTF-16, lots of benchmarks will be needed. Hence, this is the first focus of the GSoC project: collecting a large benchmark suite which models real-world usage of the text library. This is why I'd like to ask everyone who has written/knows libraries or applications that use the text library extensively to inform me of these efforts. The reverse dependencies list on Hackage is a good starting point for me but it doesn't point out how popular these packages are and how intensively they use the text library. I will then convert a subset of this code to a benchmark suite using criterion. Open source code means more reliable benchmarks, because I can publish the code I used for them. However, I'm also willing to sign non-disclosure agreements if this means I can try out what effects the changes have on large systems. There's several ways to contact me: you can reply to this thread, or you can mail me privately using `jaspervdj+text@gmail.com`. Thanks in advance for any help! [1]: http://code.google.com/soc/ [2]: http://hackage.haskell.org/package/text [3]: http://jaspervdj.be/files/2011-gsoc-text-utf8-proposal.html Cheers, Jasper

2 1

ANNOUNCE: New version Feldspar
by Emil Axelsson 27 Apr '11

27 Apr '11

On behalf of the Feldspar team, I'm happy to announce version 0.4.0.2 of feldspar-language and feldspar-compiler: http://hackage.haskell.org/package/feldspar-language http://hackage.haskell.org/package/feldspar-compiler Feldspar is an embedded domain-specific language for generating code for embedded applications, in particular for digital signal processing. For more information, see our web pages: http://feldspar.inf.elte.hu/feldspar/ http://feldspar.inf.elte.hu/ A brief list of changes since the last version: * Support for GHC 7. * Including a fresh tutorial for new users. * Improved C code generation (efficiency and readability). - Efficient vector append. - More unified representation of arrays in the C code. - Etc. * A new sequential construct for unfolding vectors using an accumulating parameter. * Support for structs. * New optimization: common sub-expression elimination. * Lots of restructuring under the hood. * Bugfixes. / Emil

1 0

How to update the RNG per call (State monad) when generating QuickCheck arbitraries?
by Daniel Kahlenberg 27 Apr '11

27 Apr '11

Maybe this is a beginners question... But here my problems description: > import Random > import Control.Monad > import qualified Control.Monad.State as S > import Test.QuickCheck.Gen > import Test.QuickCheck.Arbitrary Each thing can have one of three types: > data Ontology = Thing1 Bool > | ThingK Bool > deriving (Show, Eq) > instance Arbitrary Ontology where > arbitrary = > oneof [ return $ Thing1 True > , return $ ThingK True > , return $ Thing1 False > , return $ ThingK False ] Liked to have a state monad runner for my arbitrary things as in "Real World Haskell", "Chapter 14. Monads" ("Random values in the state monad"). [RWH]: > -- file: ch14/Random.hs > type RandomState a = S.State StdGen a [RWH]: < -- file: ch14/Random.hs < getRandom :: Random a => RandomState a < getRandom = < S.get >>= \gen -> < let (val, gen') = random gen in < S.put gen' >> < return val [RWH]: < -- file: ch14/Random.hs < getTwoRandoms :: Random a => RandomState (a, a) < getTwoRandoms = liftM2 (,) getRandom getRandom [RWH]: < -- file: ch14/Random.hs < runTwoRandoms :: IO (Int, Int) < runTwoRandoms = do < oldState <- getStdGen < let (result, newState) = S.runState getTwoRandoms oldState < setStdGen newState < return result Thought getRandom function would be the best place to inject my unGen function call, but cannot get it to type-check: > getRandom :: Random a => RandomState [a] > getRandom = > S.get >>= \gen -> > let (val, gen') = liftM2 (,) (unGen arbitrary gen 12) (random gen) in > S.put gen' >> > return val A function not almost fulfilling my needs but the Random Number Generator isn't updated... I liked to have different [Ontology] occasions per call: > genArray :: [Ontology] > genArray = unGen arbitrary (mkStdGen 42) 12 :: [Ontology] Does anyone have the patience to help me out at least one step further? Cheers Daniel

2 3

plugins and cabal build
by Michael Snoyman 27 Apr '11

27 Apr '11

Hi all, I'm experimenting with using the plugins package for yesod devel server. The basic approach is to use cabal for building the object files, and then load them with plugins. I can get everything to work when I compile with "ghc --make", but I believe name mangling is getting in the way with the "cabal build" route. Can someone give some guidance on how to properly mangle the function names so that plugins can load them? Thanks, Michael

3 3

Creating polygons in qtHaskell
by Øystein Kolsrud 26 Apr '11

26 Apr '11

Hi! I'm using qtHaskell and I'm trying to create a QGraphicsPolygonItem object. From what I see I need to create a QPolygonF item that I can supply to the constructor, but to populate the QPolygonF I need to use methods of the QVector class that QPolygonF inherits and I can't figure out how to do that. It seems that QVector is not part of the qtHaskell library. What I would like to do is something like this (where mypoints is a list of QPointF): makePolygon = do polygon <- qPolygonF () mapM (pushBack polygon) mypoints qGraphicsPolygonItem_nf polygon However, pushBack doesn't seem to be available. Does anyone know a way to do this? -- Mvh Øystein Kolsrud

1 0