April 2005 - Haskell - Haskell.org

2 Chairs at St Andrews
by Kevin Hammond 23 Apr '05

23 Apr '05

University of St Andrews As part of an ongoing programme of expansion, applications are invited for the following posts in Computer Science. 2 Chairs () You should have an outstanding international record of research and publication or the equivalent industrial experience. The new Chairs will play a leading role in the continuing development of the School's expansion and will be expected to form new research groups. The School currently has 2 professors, 2 readers, 4 senior lecturers, 7 lecturers, and 10 post-doctoral fellows and provides a stimulating environment for research and teaching. It has a Research Selectivity Rating of 5A and an SSR of about 10:1. A new Computer Science building has just been constructed. Further particulars are available as a Microsoft Word document at (http://www.dcs.st-and.ac.uk/news/CS_FP_2005.doc) Please quote the appropriate reference. Closing Date: 29 April 2005 Application forms available from http://www.st-andrews.ac.uk/hr/recruitment/vacancies or from Human Resources, University of St Andrews, College Gate, North Street, St Andrews, Fife KY16 9AJ, (tel: 01334 462571, by fax 01334 462570 or by e-mail Jobline(a)st-andrews.ac.uk) The University is committed to equality of opportunity.

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haddock -cpp ? Cabal support for haddock ?
by Johannes Waldmann 22 Apr '05

22 Apr '05

What is the preferred way to generate haddockumentation from code that must be preprocessed (ghc -cpp)? Would Cabal support this? I'd certainly welcome Cabal support for other haddock features as well (--source, --read-interface). I am not sure where to put all these arguments in the .cabal file. And ... could we have something in haddock like JavaDoc's "@since" tag? -- -- Johannes Waldmann -- Tel/Fax (0341) 3076 6479/80 -- ---- http://www.imn.htwk-leipzig.de/~waldmann/ -------

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RE: [Haskell] haddock -cpp ? Cabal support for haddock ?
by Simon Marlow 22 Apr '05

22 Apr '05

On 21 April 2005 18:21, Johannes Waldmann wrote: > What is the preferred way to generate haddockumentation > from code that must be preprocessed (ghc -cpp)? Either use ghc -E -cpp, or Cabal to preprocess the files. > Would Cabal support this? I'd certainly welcome Cabal support > for other haddock features as well (--source, --read-interface). > I am not sure where to put all these arguments in the .cabal file. > > And ... could we have something in haddock like JavaDoc's "@since" > tag? That's a reasonable suggestion... I doubt I'll have time to implement it soon, but patches are always welcome. Cheers, Simon

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cabal feature request
by Benjamin Franksen 22 Apr '05

22 Apr '05

I finally succeeded using cabal for a project that uses hsc2hs. My problem was/is I need to give special options to hsc2hs, for instance a different template header file to use. Cabal doesn't support this at the moment. I propose to give the user a bit more flexibility with regard to preprocessors, i.e. add some more tags to the .cabal file, like hsc2hs-options, cpp-options, ... I made the necessary changes for hsc2hs-options in a few minutes (thanks to the nicely structured cabal libraries :). Another question: Is there a proposal how to (better) support test executables for a library package? (I remember that this topic has been discussed but can't remember any conclusion). Cheers Ben

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Going nuts
by Alexandre Weffort Thenorio 21 Apr '05

21 Apr '05

As usual a beginner in Haskell. Trying to write a simple program in haskel shown below main :: IO() main =catch (do hexFile <- readFile "file" putStr "What is the key number (0 or 1)?\n" keyno <- getLine putStr "Input key.\n" key <- getLine newLine <- outputLine keyno key (lines(hexFile)) bla bla bla........ getLeft :: String -> String -> String getLeft _ [] = "" getLeft key line |key == "0" = take 9 line |otherwise = take 25 line getRight :: String ->String -> String getRight _ [] = "" getRight key line |key == "0" = drop 25 line |otherwise = drop 41 line outputLine keyno key orgFile = do part1 <- getLeft keyno orgFile part2 <- getRight keyno orgFile total <- part1 ++ (strUpper key) ++ part2 ++ "\n" newHexFile <- openFileEx "newfile" (BinaryMode WriteMode) hPutStrLn newHexFile (orgFile!!0 ++ "\n" ++ total ++ unlines (drop 2 orgFile)) strUpper :: String -> String strUpper [] = "" --strUpper x:xs = (toUpper x):(strUpper xs) And I keep getting the error changecode.hs:42: Couldn't match `[a]' against `Char' Expected type: [a] Inferred type: Char In the first argument of `(++)', namely `part1' In a 'do' expression: total <- part1 ++ ((strUpper key) ++ (part2 ++ "\n")) I have tried thousands and thousand of modifications (Originally getLeft and getRight didn't exist, the code was part of outputLine) but it keeps thinking that orgFile is a String when clearlly it is a [String]. Also I can get my function strUpper (Which simply puts strings to Upper case) to work. Can anybody see what is wrong here? Best Regards Alex

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ICLP 2005: Call for Papers
by ICLP 2005 21 Apr '05

21 Apr '05

Preliminary Call for Papers ------------------------------------------------------------ Twenty first International Conference on Logic Programming ICLP'05 2-5 October, 2005 Sitges (Barcelona) Spain Co-located with the International Conference on Principles and Practice of Constraint Programming (CP'05) ------------------------------------------------------------ http://www.iiia.csic.es/iclp2005/ [* Please note that ICLP'05 has a doctoral consortium for the first time as well as a special industrial paper session (details below). * Note that ICLP05's dates intersect with a solar eclipse visible in Barcelona ]. The Conference -------------- The 21st International Conference on Logic Programming will be held near Barcelona (Spain) from October 2nd to October 5th, 2005. ICLP'05 will be colocated with the International Conference on Principles and Practice of Constraint Programming (CP'05). Conference scope ---------------- Since the first conference held in Marseilles in 1982, ICLP has been the premier international conference for presenting research in logic programming. Contributions (papers and posters) are sought in all areas of logic programming including but not restricted to: Theory Implementation Semantic Foundations Compilation Formalisms Memory Management Nonmonotonic Reasoning Virtual Machines Knowledge Representation Parallelism Environments Alternative Paradigms Program Analysis Constraint Logic Programming Program Transformation Abductive Logic Programming Validation and Verification Inductive Logic Programming Debugging, Profiling Answer Set Programming Language Issues Applications Concurrency Semantic Web Objects Software Engineering Coordination Web Tools Mobility Internet Agents Higher Order Artificial Intelligence Types Deductive Databases Modes Natural Language Programming Techniques Specific attention will be given to work providing novel integrations of these different areas, and to new applications of logic programming in general. Contributions on applications will be assessed with an emphasis on their impact and synergy with other areas, as opposed to technical maturity. Applications of logic programming to the Semantic Web are especially encouraged. The technical program will include several invited talks and advanced tutorials, in addition to the presentations of the accepted papers and posters. A special session on industrial applications of logic programming is also planned and several workshops will be held in parallel with the conference. For the first time, a doctoral student consortium will be organized as part of ICLP. Papers ------- Papers must describe original, previously unpublished research, and must not be simultaneously submitted for publication elsewhere. They must be written in English and not exceed 15 pages in Springer LNCS format. The authors are encouraged, although not obliged, to submit their papers already in Springer LNCS format. General information about the Springer LNCS series and the LNCS authors' instructions are available at the Springer LNCS/LNAI home page (http://www.springer.de/comp/lncs/index.html) Papers should express their contribution clearly, both in general and technical terms. It is essential to identify what was accomplished, describe its significance, and explain how the paper compares with and advances previous work. Authors should make every effort to make the technical content understandable to a broad audience. The primary means of submission will be electronic, in pdf format. If electronic submission is not possible, five hard copies should be sent to one of the program co-chairs. More information on the submission procedure will be available at http://www.easychair.org/ICLP2005/submit/ Industrial Papers ----------------- A special session on industrial applications of logic programming is also planned during the conference. Papers accepted in this session will describe innovative applications of logic programming to industrial problems. The application's innovativeness and industrial impact will be the main criteria used for judging the paper. Papers accepted for this session will be published in the proceedings as shorter, (up to) 10 pages papers. Posters ------- Posters provide a forum for presenting work in an informal and interactive setting. They are ideal for discussing current work not yet ready for publication, for PhD thesis summaries and research project overviews. Accepted posters will also get a 10 minute slot for presentation during the conference. Extended abstract (2 pages) of each accepted poster will be published in the proceedings. Posters must be submitted electronically. More information on the submission procedure will be available at http://www.easychair.org/ICLP2005/submit/ Doctoral Student Consortium --------------------------- The Doctoral Consortium will provide an opportunity for students pursuing their doctoral thesis in logic programming and related areas to explore their research interests under the guidance of a panel of distinguished experts in the field. The Doctoral Consortium will also offer invited speakers and discussion groups. The Consortium will allow participants to interact with established researchers and with other students, through presentations, question-answer sessions, panel discussions, and invited presentations. A separate call-for-participation will be issued for the doctoral consortium. About 6 to 8 students will be selected for the consortium. Selected students will also present their research in the poster session. The abstract of the poster will be published in the conference proceedings. Financial support for selected students may be available. Publication ----------- The proceedings of the conference will be published by Springer-Verlag in the LNCS series. The proceedings will include the accepted papers and the abstracts of accepted posters. Sponsoring and prizes --------------------- The conference is sponsored by the Association for Logic Programming. The ALP has funds to assist financially disadvantaged participants. The ALP is planning to sponsor two prizes for ICLP'05: for the best technical paper and for the best application paper. Important dates --------------- POSTERS PAPERS Abstract submission deadline: 30 April Submission deadline: 1 June 6 May Notification of authors: 1 July 24 June Camera-ready copy due: 15 July 15 July Organization ------------ Conference Co-Chairs: Pedro Meseguer (IIIA-CSIC, Spain) Javier Larrosa (Technical University of Catalonia, Spain) Program Co-Chairs: Maurizio Gabbrielli (University of Bologna, Italy) Gopal Gupta (University of Texas at Dallas, USA) Workshop Chair: Hai-Feng Guo (University of Nebraska at Omaha, USA) Doctoral Consortium Chair: Enrico Pontelli (New Mexico State University, USA) Publicity Chair: Felip Manya (IIIA-CSIC, Spain) Program Committee: Roberto Bagnara University of Parma, Italy Maurice Bruynooghe KU Leuven, Belgium Giorgio Delzanno University of Genova, Italy Stefan Decker Digital Enterprise Research Institute, Ireland Thom Fruehwirth University of Ulm, Germany Maurizio Gabbrielli University of Bologna, Italy (Program Co-Chair) Gopal Gupta University of Texas at Dallas, USA (Program Co-Chair) Patricia Hill University of Leeds, UK Joxan Jaffar University of Singapore, Singapore Bharat Jayaraman SUNY Buffalo, USA Javier Larrosa Technical University of Catalonia, Spain (Conference Co-Chair) Michael Leuschel University of Dusseldorf, Germany Massimo Marchiori University of Venice, Italy and W3C, MIT, USA Pedro Meseguer IIIA-CSIC, Spain (Conference Co-Chair) Juan J. Moreno Navarro Technical University of Madrid, Spain Gopalan Nadathur University of Minnesota, USA Ilkka Niemela Helsinki U. of Tech. Finland Catuscia Palamidessi INRIA, France Enrico Pontelli New Mexico State Univeristy, USA I.V. Ramakrishnan SUNY Stony Brook, USA Vitor Santos Costa Federal U. of Rio de Janeiro, Brazil Harald Sondergaard University of Melbourne, Australia Peter Stuckey University of Melbourne, Australia Frank Valencia University of Uppsala, Sweden Contact addresses ----------------- Conference Chairs: Pedro Meseguer Javier Larrosa IIIA-CSIC Dep. LSI, UPC Campus UAB Jordi Girona 1-3 08193 Bellaterra, Spain 08034 Barcelona, Spain Program Co-chairs: iclp05-chairs(a)cs.unibo.it Maurizio Gabbrielli Gopal Gupta Department of Computer Science Department of Computer Sciences MS EC31 University of Bologna The University of Texas at Dallas Mura A. Zamboni 7 2601 N. Floyd Rd 40127 Bologna, Italy Richardson, TX 78050, USA

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compiling under osx
by Eli Jordan 21 Apr '05

21 Apr '05

hi im a first year computer science student, and we are currently learning haskell. We have recently begun to learn the IO functions and to compile programs. The problem i have is that when i execute the command ghc -o <exe-name> <name>.hs it is supposed to produce two files, when i do it <exe-name> is not produced. i am running under osx 10.3.9, and do not understand why this is happening, any help would be greatly appreciated. cheers Eli Jordan

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profiling and GHC6.4
by Ketil Malde 21 Apr '05

21 Apr '05

Hi, I have some problems getting profiling to work with a ghc-6.4 that I compiled from source. Everything seems to work all right, but the output doesn't contain any times; in time profiling (+RTS -p) times are all zeros, with heap profiling, I never get any 'samples' output, just an empty one. I can go back to see if there's anything I configured incorrectly, but this sounds weird enough that I thought I'd ask the list if this is a known problem (preferably with a known solution). Is it? (ghc 6.4 compiled from source with ghc 6.2.2 on Ubuntu 5.04, Linux 2.6.12-rc2) -kzm -- If I haven't seen further, it is by standing in the footprints of giants

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Variable arity function (VarArg)
by ChrisK 21 Apr '05

21 Apr '05

And while I'm posting to the list, I'll send something I wish I had found earlier. I had wanted to write show several things, and writing show 10 times was not clever. And so I initially created an infix operator to put between everything to do the showing, which was not much better. But this http://okmij.org/ftp/Haskell/types.html#polyvar-fn was the clever technique. {-# OPTIONS -fglasgow-exts #-} -- Techinque from http://okmij.org/ftp/Haskell/types.html#polyvar-fn -- canShowList and ssum will take a variable number of arguments data CanShow where { CanShow :: Show a => a -> CanShow ; CSLit::String->CanShow} instance Show CanShow where show (CanShow a) = show a show (CSLit s) = s -- The initial type is accumulator, here a simple list class (Show a) => ShowList a r where canShowList :: [CanShow] -> a -> r -- After accumulating last argument, you can apply a function, e.g. reverse instance (Show b) => ShowList b [CanShow] where canShowList l x = reverse $ (CanShow x):l -- Get next argument instance (Show a,ShowList b r) => ShowList a (b->r) where canShowList l x = canShowList ((CanShow x):l) -- Could eat initial fully typed arguments and make tuple with [] sL :: (ShowList a r) => a -> r sL = canShowList [] pio :: [CanShow]->IO() pio = putStr . unlines . (map show) eatFirstClass :: (forall a r.(ShowList a r)=>(a->r))->[CanShow] eatFirstClass s = s "and more" -- Using the same technique to do more work -- This example needs the "r->a" FunDep to work: class (Num a)=>ScaledSum a r | r->a where ssum' :: (a,a) -> a -> r instance ScaledSum Double Double where ssum' (s,t) x = (s*(t+x)) -- As an added bonus we get "context sensativity" instance ScaledSum Double Int where ssum' (s,t) x = floor (s*(t+x)) instance (ScaledSum a p) => ScaledSum a (a->p) where ssum' (s,t) x = ssum' (s,t+x) ssum a x = ssum' (a,0) x -- This fails since ::[Int] applies to (print $ build 1 2 3) --main = print $ build 1 2 3 ::[Int] -- Use parenthesis to control ::[Int] syntax main = do let empty :: [String] empty = [] full = [1,2,3] efc = eatFirstClass (sL empty full) eol = CSLit "\n" ssI = (ssum 12) 1 (1/2) (-3.5) :: Int ssD = (ssum 12) 1 (1/2) (-3.5) :: Double pio (sL "Hi!" (17,'a') eol (1,CSLit ['a']) empty (CSLit "ping\n") full efc ("ssum",ssI,ssD) "Bye!") let other = sL "Terminate with ::[CanShow]" full 1 eol 2 eol 3 ::[CanShow] putStrLn $ show other === GHCI === *Main> main "Hi!" (17,'a') (1,a) [] ping [1,2,3] [[],[1,2,3],"and more"] ("ssum",-24,-24.0) "Bye!" ["Terminate with ::[CanShow]",[1,2,3],1, ,2, ,3]

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RE: [Haskell] the wonders of lazy IO
by Simon Marlow 20 Apr '05

20 Apr '05

On 19 April 2005 06:30, Johannes Waldmann wrote: > Thanks for the comments. Indeed I knew the solution - > once I isolated the problem. > > Note that ghc(i) behaves differently when running main2 below > (it says "file is locked"). (hugs does not complain.) > > import System > > main1 = do > system "echo A > foo" > a <- readFile "foo" > system "echo B > foo" > b <- readFile "foo" > print (a == b) > > main2 = do > writeFile "foo" "A" > a <- readFile "foo" > writeFile "foo" "B" > b <- readFile "foo" > print (a == b) GHC is correct to complain about main2, FWIW. The Haskell report specifies single-writer/multiple-reader locking on files. Cheers, Simon

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