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ANN: Emping 0.4
by Hans van Thiel 07 Mar '08

07 Mar '08

Hello All, Emping 0.4, a utility which can derive heuristic rules from facts in Open Office Calc spreadsheet .csv format, has been released on HackageDB. Version 0.4 supports blank fields, treated as 'none of the others', which allows for split attribute values. For example, "Owns Car" could have values "Yes" or 'No", and then "Yes" could be split into "Make", "Price Range" and so on, while the fields for "No" could be blank for these attributes. Data still have to be in the spreadsheet format of rows and columns (and in OO Calc .csv). Version 0.4 has a Gtk2Hs based GUI and the code has been changed in several places. Compiled with GHC 6.8 it appears to be noticeably faster than version 0.3. The package comes with a user guide, a white paper, and two data files from the UCI Machine Learning Repository. To get an impression see: http://j-van-thiel.speedlinq.nl/emp/empug.html The compiled binary for Linux, with documentation, can also be downloaded directly from my web site. Thank you, Hans van Thiel

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Re: [Haskell-cafe] Analysing Haskell with Graph Theory
by Ivan Miljenovic 07 Mar '08

07 Mar '08

(CC'd to the list) On 07/03/2008, Dusan Kolar <kolar(a)fit.vutbr.cz> wrote: > I'm just wondering what algorithms you use for analysis. For instance, > clique is an NP complete problem. Do you use some approximation? If yes, > which? I'm particularly interested in the algorithm. I haven't gotten that far yet ;-) As it stands, my supervisor have discussed this slightly and I'll probably start off with a more-or-less brute-force approach. This should be OK as the graph will probably be reasonably sparse and (hopefully) not too big! -- Ivan Lazar Miljenovic

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CABAL: conditional executable?
by Magnus Therning 07 Mar '08

07 Mar '08

I'm putting together a package consisting of 2 executables. Only one of them is pure Haskell and thus buildable on all platforms, the other relies on Windows API calls and can only be built on that platform. I found the “if os(...)” conditional in the CABAL docs but I'm having problems getting it to do what I want. if os(mingw32) executable foo ... Results in the error “Section expected”. Swapping the two lines like this executable foo if os(mingw32) ... results in “Setup.hs: Error: No 'Main-Is' field found for executable foo”. Is there a way to get CABAL to do what I want or should I raise a feature request on the CABAL trac? /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus．therning＠gmail．com http://therning.org/magnus What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? -- Daveman

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"Hello World" in Haskell for web browser
by Dimitry Golubovsky 07 Mar '08

07 Mar '08

Hi, I have noticed that some people tried to compile a traditional Haskell program using IO monad to show "Hello World" using Yhc Web Service. Thanks for your interest, and here are some clues. The programming paradigm chosen for Haskell Web programming is not based on monads. It is based on CPS-style calls to DOM functions by Haskell code compiled to Javascript. Further on, additional layers may stack up (such as Haskell Web Toolkit) to provide more convenient APIs, but DOM is the basis. So here is an example of "Hello World" program written this way: -- begin pasteable code -- module HelloWorldDOM where import CPS import UnsafeJS import CDOM.Level2.DomUtils import DOM.Level2.Dom import DOM.Level2.Html2 import DOM.Level2.HTMLElement import DOM.Level2.HTMLDivElement main = getHTMLDocument $ \doc -> documentBody doc $ \body -> mkText doc "Hello World" $ \txt -> mkDiv doc $ \dv -> addChild txt dv $ \_ -> addChild dv body $ id -- end pasteable code -- The meaning of this: * get reference to the HTML document node first (it is the parent of everything), * extract the <BODY> tag node, create at text element with "Hello World", * create a <DIV> tag node, * insert the text node into div, * insert div into body Or, same in HTML: <html> <body> <div> Hello World </div> </body> </html> but filled in dynamically. Using Haskell Web Toolkit API, the same may be expressed in more compact fashion: -- begin pasteable code -- module HelloWorldHsWTK where import DOM.Level2.HTMLDivElement import Graphics.UI.HsWTK main = docBodyC (mkDiv |<< textP "Hello World") -- end pasteable code -- Here, docBodyC is roughly equivalent of the first two DOM calls, mkDiv is same as above, |<< means "insert into container", and textP is a wrapper around mkText. Earlier, I posted the link to Haddock-generated documentation which also includes the Haskell DOM API. Here it is again: http://www.golubovsky.org:5984/_utils/yhcws/index.html Hopefully this example along with the documentation provided helps shed some light on Haskell Web programming techniques. Feel free to ask questions. Thanks. -- Dimitry Golubovsky Anywhere on the Web

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Re: [Haskell-cafe] Connection helpers: for people interested in network code
by brad clawsie 06 Mar '08

06 Mar '08

"Gwern Branwen" <gwern0(a)gmail.com> writes: >> i offered some time ago to look at building a cabal package and >> documentation for this. i would offer up excuses as to why this hasn't >> appeared yet, but between kids, work and ski season i just haven't >> allocated the time yet. sorry to all. i still hope to look into this, >> but fair to say i dropped the ball. > > Dunno. I just downloaded the git repo, and I'm not sure what's > stopping anyone from uploading it to Hackage. It builds cleanly and > with essentially no warning on 6.8.2, the Haddock docs build, and so > on. The Cabal file itself is quite good; out of boredom, I tweaked it > a little: awesome! that means someone has indeed recognized my lameness and subbed in to do what i didn't. thanks to whoever you are! sorry again for promising and not delivering [gwern, hope you don't mind if i redirect your personally reply to the list for context preservation]

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If Version Control Systems were Airlines
by Justin Bailey 06 Mar '08

06 Mar '08

Way off topic, but this is the cafe. The below is well worth reading. http://changelog.complete.org/posts/698-If-Version-Control-Systems-were-Air… For the click-impaired, here's Darcs Airlines: "Darcs Airlines: Unlike every other airline, this one uses physicists instead of engineers to design its airplanes. One brilliant Darcs physicist has finally come up with The Theory of Everything, and as such, Darcs knows where you want to go before even you do. Darcs airlines prides itself on customer service, and asks your preference for even the tiniest details about your trip. Each seat pocket features a copy of the Theory of Everything for your reading enjoyment, but nobody actually understands it. Occasionally, you will find that Darcs pilots get into angry conflicts with the control tower in mid-flight. This results in the control tower revoking your permission to land. Legend has it that one Darcs pilot of a plane with exceptionally large fuel tanks actually resolved his conflict with the tower and landed two weeks after taking off. Experienced Darcs users board with several parachutes: one for themselves, and a few more for the newbies. The Darcs physicists claim that the Theory of Everything predicted the pilots would act this way, and that all pilots eventually act this way throughout the entire universe. They toil day and night finding a way to adjust the gravitational constant of the universe, thereby reducing the anger factor of the pilots. Main competitor: OS/2 airlines." Justin

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Re: [Haskell-cafe] Connection helpers: for people interested in network code
by brad clawsie 06 Mar '08

06 Mar '08

> I wonder, though, what happened to the curl bindings for Haskell? i offered some time ago to look at building a cabal package and documentation for this. i would offer up excuses as to why this hasn't appeared yet, but between kids, work and ski season i just haven't allocated the time yet. sorry to all. i still hope to look into this, but fair to say i dropped the ball.

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[GSoC] Project proposal: Hoogle 4
by Neil Mitchell 06 Mar '08

06 Mar '08

Hi I would like to be a Summer of Code student, doing the project "Hoogle 4" (http://haskell.org/hoogle/) PROJECT GOALS: There are two main themes: 1) Make Hoogle more useful to the community, along the same path as it is currently used. 2) Make Hoogle suitable to use as the standard interface to Hackage. This requires adding the following features to Hoogle, to form a Hoogle 4 release: * Faster searching (1000x faster at least, perhaps more like 1000000x for text searching) * Generalised text searching (i.e. searching .cabal fields) * Removal of all bugs :-) * Support for higher-kinded type classes (i.e. Monads) * Support for some Haskell type extensions (i.e. Multi-Parameter type classes) * Support for multiple packages * Generalised interface to all of Cabal Progress on Hoogle 4 has already started, but has currently stalled due to lack of time. I am writing up my PhD currently, and will be available to start at the beginning of the Summer to work on Hoogle. Duncan Coutts has agreed to mentor this project. The position of backup mentor is still available. I do not expect to need a great deal of supervision :-) Please respond with any suggestions, requests for further information or just general comments. Thanks Neil

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Google summer of code
by Malcolm Wallace 06 Mar '08

06 Mar '08

Reply-To: haskell-cafe(a)haskell.org Google Summer of Code As many of you will already know, Google is running its "Summer of Code" project again this year, and haskell.org is once again going to apply to be a mentoring organisation. Are you a student who would like to earn money for hacking in Haskell? Or are you a non-student who has a cool idea for a coding project but no time to do it yourself? Well, our wiki to gather ideas is now up-and-running again: http://hackage.haskell.org/trac/summer-of-code Add yourself to the list of interested people! Especially potential mentors. There are some ideas still there from last year, in the trac tickets. However, due to the amount of spam accumulating there, I suggest that this year, we use the haskell-cafe email list as a place to put out project ideas, solicit feedback on them, and look for interested people. Prefix any message subject line with with [GSoC] to help others find them. Google will start accepting student applications on 24th March, but now is the time to start gathering thoughts and matching up interesting ideas with interested people. The official timeline is as follows: March 12: Mentoring organization application deadline March 17: List of accepted mentoring organizations published March 24: Student application period opens March 31: Student application deadline Interim Period: we review and rank student proposals April 14: List of accepted student applications published Interim Period: Students learn more about their project communities May 26: Students begin coding; Google begins issuing initial payments July 14: Google begins issuing mid-term payments August 11: Suggested end of coding August 18: Definite end of coding Sept 1: Final evaluation deadline; Google begins issuing final payments Sept 3: Students upload code to Google (required) Regards, Malcolm

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SimpleArgs
by Ketil Malde 06 Mar '08

06 Mar '08

Hi, Often when I write small scripts, I find I just want a couple of command line arguments but don't want to go the whole GetOpt route. SimpleArgs is an attempt to make the raw getArgs somewhat less raw, and quick and dirty scripts a bit less dirty without sacrificing the quickness. Since I find this quite useful, I thought I'd advertise the code here, ask what people think, and invite suggestions for improvement. It's at: http://malde.org/~ketil/simpleargs -k -- If I haven't seen further, it is by standing in the footprints of giants

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