September 2011 - Haskell-Cafe

Packaged my log visualization tools
by Eugene Kirpichov 17 Sep '11

17 Sep '11

Hello cafe, I've packaged my log visualization tools in binary form for several platforms. Perhaps those of you who have better things to do than struggle installing them from source will find this useful :) Here you go: http://jkff.info/presentations/two-visualization-tools.pdf Documentation http://jkff.info/software/timeplotters-0.1-1_win32.zip Windows (any architecture) http://jkff.info/software/timeplotters-0.1-1_i386.deb Debian (i386) http://jkff.info/software/timeplotters-0.1-1_amd64.deb Debian (amd64) http://jkff.info/software/timeplotters-0.1-1_i386.tar.gz *nix binaries (i386), require gtk2.0, gmp3, libc6. http://jkff.info/software/timeplotters-0.1-1_amd64.tar.gz *nix binaries (amd64), require gtk2.0, gmp3, libc6. -- Eugene Kirpichov Principal Engineer, Mirantis Inc. http://www.mirantis.com/ Editor, http://fprog.ru/

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ANNOUNCE: qrcode: QR Code encoder in pure Haskell
by Chris Yuen 16 Sep '11

16 Sep '11

Hello cafe, My first Hackage upload is a pure Haskell QR Code library ( http://hackage.haskell.org/package/qrcode-0.1) This is intended to be a full featured QR Code library with encoding and decoding and other advanced features. Currently it can only do encoding but I figured it would be nice to get some early feedback so here we go :) Cheer, Chris

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pattern matching instead of prelude.head
by Michael Litchard 16 Sep '11

16 Sep '11

Someone commented on StackOverflow that pattern matching the first element of a list was preferable to head. This makes sense intuitively. Could someone articulate the reason why this is true?

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VirtuaHac - online Haskell hacathon
by Chris Smith 16 Sep '11

16 Sep '11

Overview ======== VirtuaHac is a Haskell hacathon being planned using Google+ and a Wiki. The rules will be that if you have a project you'd like to participate in, then: 1. Create a darcs or git repository. 2. Post a Hangout in Google+. 3. Add a name, brief description, and links to the preceding two items to the Wiki. This way, we hope to recreate the idea of a Hacathon, but without the travel expenses or inconvenience. What Next? ========== I'm taking a poll of availability, at https://docs.google.com/spreadsheet/viewform?formkey=dDZ3Tjh1RzVDeHdRYWhNTk… The poll will remain open for the next week, after which I'll choose a date so we can all start planning. -- Chris Smith

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ANN: numerals
by Roel van Dijk 16 Sep '11

16 Sep '11

Hello everyone, I would like to announce the release of the numerals and numerals-base packages. * Numerals The numerals package contains functions to convert numbers to number words in a number of languages. For now the package only supports cardinal numbers. Example: >>> import qualified Text.Numeral.Language.EN as EN >>> EN.uk_cardinal 123 :: Maybe String Just "one hundred and twenty-three" You can also inspect the underlying structure of a number word: >>> import Text.Numerals >>> EN.shortScaleStruct 123 :: Exp Add (Mul (Lit 1) (Lit 100)) (Add (Mul (Lit 2) (Lit 10)) (Lit 3)) Compare this structure with the number word: 1 (one) * 100 (hundred) + (and) 2 (twen) * 10 (ty) + 3 (three) The package also comes with a test suite: >>> cabal configure --enable-tests >>> cabal build >>> ./dist/build/test-numerals/test-numerals --hide-successes I recommend the "--hide-successes" option of test-framework (>=0.4) because there are many tests (3383). * Numerals-base The numerals-base package contains all the machinery upon which numerals is build. Using this package you can write conversion functions for your own language(s). It is documented, although the documentation can be improved. For now the numerals package is probably the best documentation. * Resources: Hackage: http://hackage.haskell.org/package/numerals http://hackage.haskell.org/package/numerals-base Github: http://github.com/roelvandijk/numerals http://github.com/roelvandijk/numerals-base * Help wanted Currently I support 24 languages. But I only have some experience with 4 of them. The rest is scraped together with information I found online. For most languages I can find online how to form the first 100 cardinal numbers. But after that information is sparse. You can help by checking and expanding the test suite. This is very simple because the test suite consists only of numbers combined with the expected cardinal number word. Regards, Roel van Dijk

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ANN: Webwire 0.1.0, netwire 1.2.5
by Ertugrul Soeylemez 16 Sep '11

16 Sep '11

Hello fellow Haskellers, webwire is an experimental web framework based on the functional reactive programming library netwire. It uses WAI under the hood and right now features only a subset of the very basics of what you need to write web sites. Features: * Reactive programming of web sites. * Stick together subapplications similar to Happstack. * Build web pages piece by piece using Yesod-inspired widgets. * Builtin support for "shakespearean" templates. * Builtin support for selecting output types (like HTML/JSON). * Simple Happstack-style routing functionality. * Very simple overall design. * And as always: 100% Haddock documentation coverage. Its aim is to combine all the good features of continuation-based web frameworks by hiding as much as possible of the stateless nature of HTTP. Through the netwire library it introduces some new design patterns, which appear to work amazingly well for web applications: * Powerful new design pattern for sessions: Through netwire's context-sensitive wires it becomes almost trivial to have separate subwires for every user. This way you can write your applications like you were in a dialog with the user. I'm planning to implement forms based on the same design pattern. * Feedback and choice make it easy to express complicated inter-request data dependencies. And together with webwire I have also released a new version of netwire. Changes include: * Generalized context wire transformers. * Generalized session functions. * Signal injection (reinject exhibited signals). Thanks go to: Cale Gibbard for support with AFRP, the Yesod team for lots of useful libraries. Keep the feedback coming! Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/

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Karatsuba Multiplication Parallel
by Burak Ekici 16 Sep '11

16 Sep '11

Dear All, I am trying to parallelize the below Karatsuba multiplication code. However, at each trial of mine the error message speaking of "incorrect indentation" is returned. I could not come up with ideas to solve the problem. I will be more than glad and appreciated, if any of you sheds light on the issue and point out the problem with its solution. Many thanks in advance, Cheers, Burak. import Control.Parallel import Control.Parallel.Strategies normalize [] = [] normalize (False : xs) = let ns = normalize xs in if ns == [] then [] else (False : ns) normalize (True : xs) = True : (normalize xs) mul [] _ = [] mul (False : xs) ys = False : (mul xs ys) mul (True : xs) ys = mul (False : xs) ys `add` ys mulk3 [] _ = [] mulk3 _ [] = [] mulk3 xs ys = (normalize (mulk3 xs0 ys0)) `add` (replicate l False ++ (((mulk3 (add xs0 xs1) (add ys0 ys1)) `sub` (normalize (mulk3 xs0 ys0)) `sub` (normalize (mulk3 xs1 ys1))) `add` (replicate l False ++ (normalize (mulk3 xs1 ys1))))) where l = (min (length xs) (length ys)) `div` 2 (xs0, xs1) = splitAt l xs (ys0, ys1) = splitAt l ys if l > 32 then (normalize (mulk3 xs0 ys0)) `par` (normalize (mulk3 xs1 ys1)) `par` ((mulk3 (add xs0 xs1) (add ys0 ys1)) `sub` (normalize (mulk3 xs0 ys0)) `sub` (normalize (mulk3 xs1 ys1))) else mul xs ys

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darcs checkin history?? forgot ....
by Vasili I. Galchin 16 Sep '11

16 Sep '11

Hello, If I have a URL for a darcs repository, how can I get a listing of activity ... mainly "checkin" history .... e.g. name, date timestamp? Thanks, Vasili

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Re: [Haskell-cafe] [Haskell] [ANNOUNCE] Haskdogs-0.1
by Ivan Lazar Miljenovic 15 Sep '11

15 Sep '11

Re-cc'ing -cafe: On 14 September 2011 14:29, yi huang <yi.codeplayer(a)gmail.com> wrote: > On Wed, Sep 14, 2011 at 11:32 AM, Ivan Lazar Miljenovic > <ivan.miljenovic(a)gmail.com> wrote: >> >> On 14 September 2011 13:27, yi huang <yi.codeplayer(a)gmail.com> wrote: >> > On Wed, Sep 14, 2011 at 10:18 AM, Ivan Lazar Miljenovic >> > <ivan.miljenovic(a)gmail.com> wrote: >> >> >> >> On 14 September 2011 11:24, yi huang <yi.codeplayer(a)gmail.com> wrote: >> >> > Cabal compains about "Unknown build tool hasktags". >> >> > It seems not necessary to set "Build-tools: hasktags" in cabal file? >> >> >> >> cabal-install isn't capable of automatically building and installing >> >> build-tools for you. So to install haskdogs, you need to do "cabal >> >> install hasktags && cabal install haskdogs". >> > >> > I have installed hasktags, and .cabal/bin is in my PATH, i can run >> > hasktags >> > directly from shell. >> > What else did i miss? >> >> How did you specify your PATH? You can't use ~/.cabal/bin, you need >> either $HOME/.cabal/bin or the fully expanded path. > > It is $HOME/.cabal/bin , and `which hasktags' can find it without problem. > Cabal 1.10.2, ghc 7.0.4, i'm trying to look into cabal source to find the > problem. Actually... looks like you're right. I can't build it either, he appears to have hard-coded some paths in and it appears that you need some kind of magic to register a program as a build tool (that's what the error is from: hasktags isn't a registered build-tool). -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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Categorized Weaknesses from the State of Haskell 2011 Survey
by Nick Knowlson 15 Sep '11

15 Sep '11

Hello all, I did a followup analysis of the free-form responses to "What is Haskell's most glaring weakness / blind spot / problem" in the State of Haskell 2011 Survey. The article is up at: http://nickknowlson.com/blog/2011/09/12/haskell-survey-categorized-weakness… I think it has a lot of interesting information in it - I hope some others will find it useful now too. Cheers, Nick

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