May 2009 - Haskell-Cafe

ANN: New repository and trac for haskell-src-exts
by Niklas Broberg 26 May '09

26 May '09

Hi all, In preparation for my GSoC project, I've set up some new infrastructure for the haskell-src-exts package. Instead of residing with the HSP packages, it's now old enough to be allowed to live on its own. The new repository is darcs get http://code.haskell.org/haskell-src-exts I've also finally set up a bug tracker for all things big and small, found at http://trac.haskell.org/haskell-src-exts I've added all issues from my old TODO list, but I'm sure there's more stuff that I've missed. Please help me by reporting anything you come across, or by requesting new and cool features. Cheers, /Niklas

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Anglohaskell?
by Philippa Cowderoy 26 May '09

26 May '09

Is anyone up for Anglohaskell this year? Perhaps more importantly, is anyone willing to step forward to run it? I can lend a hand, having organised and to some extent meta-organised in previous years, but I'm not sure I have spare time to do the same kind of job as I did in 2007. For those who're new or don't remember, http://www.haskell.org/haskellwiki/AngloHaskell contains links to info from previous years - the idea's a get-together with lots of talks from hobbyist to academic, and plenty of chat. -- Philippa Cowderoy <flippa(a)flippac.org>

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No VerboseCheck in QuickCheck 2?
by Shin-Cheng Mu 26 May '09

26 May '09

Hi, I believe this must have been raised before but I did some searching to no avail, so please allow me.. It seems that verboseCheck is gone in QuickCheck 2. In QuickCheck 2, how do we print the test cases, specify the number of tests, or the sizes of test cases, etc.? Thank you very much.. sincerely, Shin

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ANNOUNCE: Haskell Communities and Activities Report (16th ed., May 2009)
by Janis Voigtlaender 26 May '09

26 May '09

On behalf of the many, many contributors, I am pleased to announce that the Haskell Communities and Activities Report (16th edition, May 2009) http://www.haskell.org/communities/ is now available from the Haskell Communities home page in PDF and HTML formats. 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. I hope you will find it as interesting a read as I 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 editor collects all the contributions into a single report and feeds that back to the community. When I 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 2009: target deadline for contributions to the November 2009 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 editor for a simple e-mail reminder in October (you could point me to them as well, and I 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! Janis Voigtlaender <hcar at haskell.org> -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de

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Parsing command lines
by Patai Gergely 26 May '09

26 May '09

Hello all, is there a function that can safely split a command line into a FilePath to the executable and its parameters? I couldn't manage to find one. If not, what are the pitfalls in creating a cross-platform solution to this problem? Can I assume that the first space not within double quotes and not preceded by an unescaped backslash marks the end of the executable path, or is that too naive (or completely wrong)? Gergely -- http://www.fastmail.fm - A fast, anti-spam email service.

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Haskell type system and the lambda cube
by Petr Pudlak 25 May '09

25 May '09

Hi, I'm trying to get some better understanding of the theoretical foundations behind Haskell. I wonder, where exactly does Haskell type system fit within the lambda cube? <http://en.wikipedia.org/wiki/Lambda_cube> I guess it could also vary depending on what extensions are turned on. Thanks, Petr

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Haskell furniture?
by Steve Schafer 25 May '09

25 May '09

Here is some furniture that ought to appeal to the Haskell afficionado: http://karl-andersson.se/view_product.asp?rangeId=39&catId=2&picture=2 Steve Schafer Fenestra Technologies Corp. http://www.fenestra.com/

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Any interest in forming a Haskell Meetup group in Edinburgh, Scotland
by A Smith 25 May '09

25 May '09

Anyone interested in just getting together, from complete beginner, to those with experience, to share ideas and help each other other out. The Filmhouse on Lothian Road, is quite handy for Edinburgh folk, and for anyone was coming through from Glasgow, and alighting(using train speak) at Haymarket. Its got plenty space, serves reasonable food, as well as having lots of good food places nearby. I'll suggest meeting on a Saturday to try and avoid conflict with the many other things people do in the evenings. Its also off-peak return from Glasgow all day. I'm a Haskell beginner, so I'm no good for answering more difficult questions, need someone else for that. -- Andrew

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The Computer Language Benchmarks Game: pidigits
by Arnaud Payement 25 May '09

25 May '09

Hi all, I recently decided to rewrite the pidigits benchmark of the debian shootout (shootout.alioth.debian.org) as toy project. However, it seems that on my machine, the code seems to be more performant than both the current entry and the proposed replacement (see http://www.haskell.org/haskellwiki/Shootout/Pidigits) for the same number of lines. Do you think it might be worth submitting my entry? Here is my code,: {-# OPTIONS -O2 -optc-O3 #-} -- -- The Great Computer Language Shootout -- http://shootout.alioth.debian.org/ -- by Arnaud Payement -- import System data F = F Integer Integer Integer Integer extract s@(F k n a d) = ((n*3+a) `div` d, (n*4+a) `div` d, s) update (F k n a d) = F (k+1) (n*k) ((a+n*2)*y) (d*y) where y = 2*k+1 next state = let (u, v, s'@(F k n a d)) = extract (update state) in if (n > a || (u /= v)) then next s' else (show u, F k (n*10) ((a-d*u)*10) d) digits = ("", (F 1 1 0 1)):[next state | state <- map snd digits] pr (d:t) k n | k > n = putStr "" | k `mod` 10 /= 0 = putStr d >> pr t (k+1) n | otherwise = putStrLn (d ++ "\t:" ++ show k) >> pr t (k+1) n main = pr (map fst (tail digits)) 1 . read . head =<< getArgs Best, Arnaud

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[ANN] multirec-binary
by Sebastiaan Visser 25 May '09

25 May '09

Hello all, MultiRec[1,2] is a great library for generic programming for families of possibly mutual recursive data types. Creating new generic functions might take some effort but the use of these functions is very straightforward. The multirec-binary[3] packages allows generic derivation of Data.Binary instances using the MultiRec library. Just try something like this: > import Data.Binary > import Generics.MultiRec.Base > import Generics.MultiRec.Binary > > instance Binary MyType where > put = gput MyFamily > get = gget MyFamily Have fun, -- Sebastiaan Visser [1] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/multirec-0.3 [2] http://www.cs.uu.nl/research/techreps/repo/CS-2008/2008-019.pdf [3] http://hackage.haskell.org/cgi-bin/hackage-scripts/package/multirec-binary

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