August 2005 - Haskell

problems with RegEx
by Srinivas Nedunuri 03 Aug '05

03 Aug '05

hello, I'm trying to use the Text.Regex library from Hugs. However, Hugs doesn't recognize any of the methods in there. For example if I try to use the mkRegex function I get the error message "Undefined variable "mkRegex". I have imported Text.Regex into the module. I looked at the contents of the module in the HUGS library but couldnt make out too much. It looked basically empty although Text.Regex.Posix had some includes. Any help would be appreciated cheers

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Haskell Weekly News: August 2, 2005
by John Goerzen 02 Aug '05

02 Aug '05

Haskell Weekly News: August 2, 2005 Greetings, and thanks for reading the first issue of HWN, a weekly newsletter for the Haskell community. HWN is an experiment inspired by [1]Debian Weekly News and [2]Linux Weekly News. Each Tuesday, new editions will be posted (as text) to [3]the Haskell mailing list and (as HTML) to [4]The Haskell Sequence. Since this is the first issue, it covers a few items more than one week old. 1. http://www.debian.org/News/weekly 2. http://www.lwn.net/ 3. http://www.haskell.org/mailman/listinfo/haskell 4. http://sequence.complete.org/ Discussion Updating the Haskell Standard? This [5]question was posed on haskell-cafe and reaction was mixed. 5. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/7879 Best way to assemble strings? Andy Gimblett [6]inquired about building up strings. The discussion covered options such as printf, (++), concat, and even some sample code for interpolation inside strings. 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/7869 FFI, Threading, and Callbacks. John Goerzen [7]asked some questions about using FFI together with threading. Simon Marlow has written a [8]paper on the topic that is useful background. Duncan Coutts [9]described why some GUI toolkits presently do polling. 7. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/7862 8. http://www.haskell.org/~simonmar/papers/conc-ffi.pdf 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/7903 Haskell Toolchain GHC 6.4.1 release candidate is available. Simon Marlow has [10]announced the availability of GHC 6.4.1 release candidate and the beginning of testing for 6.4.1. 6.4.1 includes many fixes, including some performance enhancements, and also introduces support for a native code generator for amd64. 10. http://www.haskell.org/pipermail/glasgow-haskell-users/2005-August/008840.h… Results of GHC Performance Week. Simon Marlow posted [11]a summary of the results of the GHC performance week. They found a number of things that improve the performance of GHC, and some are already fixed in 6.4.1. 11. http://www.haskell.org/pipermail/glasgow-haskell-users/2005-August/008839.h… [12]Cabal was a hot topic this week. Brian Smith started a discussion about [13]conditional code in Cabal. It seems to be a common problem when porting software to Windows. Duncan Couts asked about [14]automated platform building of Haskell packages based on their Cabal descriptions. 12. http://www.haskell.org/cabal 13. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/3487 14. http://thread.gmane.org/gmane.comp.lang.haskell.libraries/3487 GHC in Debian unstable. Due to a C++ transition going on, GHC is currently uninstallable in Debian unstable. If you want to use it on unstable, you can grab the libgmp3 package from stable. More details in Debian bug [15]319222. 15. http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=319222 Conferences The 2005 Haskell Workshop is coming up on September 30 in Tallin, Estonia. David Roundy, author of darcs, will be a feature presenter this year. More information is available from the [16]conference page. 16. http://www.cs.uu.nl/~daan/hw2005 Darcs Corner Darcs 1.0.4pre2 released. David Roundy [17]announced the availability of Darcs 1.0.4pre2. Major updates since 1.0.3 include reduced memory usage, and experimental support for git archives. 17. http://article.gmane.org/gmane.comp.version-control.darcs.user/7987 darcsweb. Alberto Bertogli [18]announced darcsweb, a replcement for darcs.cgi modeled after gitweb. 18. http://thread.gmane.org/gmane.comp.version-control.darcs.user/7841 Darcs Success Story. Mark Stosberg wrote about a [19]success using Darcs for just-in-time branching. 19. http://article.gmane.org/gmane.comp.version-control.darcs.user/7928 Darcs on SourceForge. Eric S. Johansson [20]wondered if any SourceForge-like Darcs-friendly sites existed. Thomas Zander [21]suggested simply using public web space on SourceForge itself. 20. http://thread.gmane.org/gmane.comp.version-control.darcs.user/7899 21. http://thread.gmane.org/gmane.comp.version-control.darcs.user/7899 Centralized development with Darcs. A question was raised about [22]using Darcs for centralized development in a specific scenario. Several solutions were mentioned. Remko Troncon linked to a recipe for [23]centralized logging on the Darcs wiki. Mark Stosberg pointed out his article, [24]Benefits from a real world switch from CVS to Darcs, and also pointed out the RSS support in Darcs. 22. http://thread.gmane.org/gmane.comp.version-control.darcs.user/7929 23. http://darcs.net/DarcsWiki/HintsAndTips#head-ca5f360a0038ec704eed560a82a23a… 24. http://mark.stosberg.com/Tech/darcs/cvs_switch/ New Releases * hsffig, a new FFI binding generator, was [25]announced by Dimitry Golubovsky. Download via its Darcs [26]repository. The main unique feature of hsffig is that it can parse C .h files without any human assistance whatsoever. Version 1.0 was also [27]announced just yesterday. 25. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/7498 26. http://www.golubovsky.org/repos/hsffig 27. http://www.haskell.org/pipermail/haskell-cafe/2005-August/010941.html * c2hs version 0.14.1 is [28]out. It has a new parser system and its build system is now based upon Cabal. 28. http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/8415 * [29]MissingH 0.11.3 is out, and now supports Windows. MissingH is a library of pure-Haskell utility functions relating to strings, logging, and I/O. Darcs [30]repository also available. 29. http://quux.org/devel/missingh 30. http://darcs.complete.org/missingh * MissingH LGPL/BSD branch was announced. This branch is a stripped-down version of MissingH, with all GPL'd code either re-licensed or removed. It is available from a Darcs [31]repository only. 31. http://darcs.complete.org/missingh.lgpl Quotes of the Week <Speck> "That's like cheating. It isn't even programming. You just tell it what to do and it does it." -- My friend upon seeing some Haskell code <autrijus> Perl: "Easy things are easy, hard things are possible" <autrijus> Haskell: "Hard things are easy, the impossible just happened" About Haskell Weekly News Want to continue reading HWN? Please help us create new editions of this newsletter. Please see the [32]contributing information, or send stories to [33]hwn@complete.org. There is also a Darcs repository available. 32. http://sequence.complete.org/hwn-contrib 33. mailto:hwn@complete.org

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RE: [Haskell] Files and lazyness
by Simon Marlow 02 Aug '05

02 Aug '05

On 01 August 2005 16:05, Cale Gibbard wrote: > Your problem is, as you pointed out, that readFile does lazy IO. > Although the semantics of it can be a bit confusing at times, it is > useful for applications where you have a large file which is being > consumed, and you don't want to allocate all of the memory for it > before doing any processing. Laziness lets you read the file as needed > -- you may not even need it all, depending on what is being done. This > is quite helpful when you have something like a couple gigabytes of > data on disk which needs processing. It can however be confusing at > first that it may not finish reading the file before the file is > altered, or, in situations involving handles, before the handle is > closed. > > You can write a strict IO version of readFile in Haskell as follows: > > import IO > > hGetContents' hdl = do e <- hIsEOF hdl > if e then return [] > else do c <- hGetChar hdl > cs <- hGetContents' hdl > return (c:cs) > > readFile' fn = do hdl <- openFile fn ReadMode > xs <- hGetContents' hdl > hClose hdl > return xs > > If you use readFile', it will ensure that the entire file is read and > memory for the string is allocated before continuing. This ought to > solve your problem. Note that hGetContents' is likely to be slow, because it does repeated hGetChar. Also it is not tail-recursive, so it will run out of stack for a large file. It would be better to read the whole file into memory but lazilly convert it to a String, like so: import System.IO import System.IO.Unsafe import Foreign import Data.Char readFile' f = do h <- openFile f ReadMode s <- hFileSize h fp <- mallocForeignPtrBytes (fromIntegral s) len <- withForeignPtr fp $ \buf -> hGetBuf h buf (fromIntegral s) lazySlurp fp 0 len lazySlurp :: ForeignPtr Word8 -> Int -> Int -> IO String lazySlurp fp ix len | ix == len = return [] | otherwise = do c <- withForeignPtr fp $ \p -> peekElemOff p ix cs <- unsafeInterleaveIO (lazySlurp fp (ix+1) len) return (chr (fromIntegral c) : cs) Actually, I recommend always using this version unless you need to deal with really large files. Performance won't be quite as good as readFile, but I've attached a tweaked version that performs much better. Cheers, Simon

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Files and lazyness
by Diego y tal 02 Aug '05

02 Aug '05

I was developing a web site using haskell programs as cgi's, and I found a strange behavior that I would like to know whether it is normal. I have reduced the "problem" to the next program: fEntrada = "fich.txt" fSalida = "fich.txt" creaFich :: IO() creaFich = writeFile fEntrada "me molo" main :: IO () main = do x <- readFile fEntrada -- print x -- In the second try, uncomment this line writeFile fSalida "" writeFile fSalida x Running the next commands (suposing that $ is the prompt of a linux shell and main> is the prompt of hugs) main> creaFich main> main $ cat fich.txt will give us different results if we comment or uncomment the second line of the main body, although the meaning of the program is the same. I understand that this is caused by the lazyness, that doesn't evaluate the expression "x <- readFile fEntrada" until it's necessary, but.. is it normal that we have to think about this "problem" when programming? In my case, this behavior caused my program to fail (and it was really complicated to find why) and the only solution I found was indeed printing to a scratch file the string I was reading inmediatly after reading it (really, after telling hugs to read it). I find this a great disadvantage as oppose of the imperative paradigm, overall because is like having to control something (near to concurrence if you ask me) that has not been asked for! I 'll be thankful of any comments or replies you send to me. Greetings, Diego y tal <deigote(a)gmail.com>

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Formal Methods 2006
by Jeffery Zucker 01 Aug '05

01 Aug '05

FM'06: 14TH INTERNATIONAL SYMPOSIUM ON FORMAL METHODS 21 - 27 August 2006 McMaster University, Hamilton, Canada http://fm06.mcmaster.ca/ ANNOUNCEMENT AND CALL FOR SUBMISSIONS FM'06 is the fourteenth in a series of symposia organized by Formal Methods Europe, http://www.fmeurope.org, an independent association whose aim is to stimulate the use of, and research on, formal methods for software development. The symposia have been notably successful in bringing together innovators and practitioners in precise mathematical methods for software development, industrial users as well as researchers. Submissions are welcomed in the form of original papers on research and industrial experience, proposals for workshops and tutorials, entries for the exhibition of software tools and projects, and reports on ongoing doctoral work. FM'06 welcomes all aspects of formal methods research, both theoretical and practical. We are particularly interested in the experience of applying formal methods in practice. The broad topics of interest of this conference are: * Tools for formal methods: tool support and software engineering, environments for formal methods. * Theoretical foundations: specification and modelling, refining, static analysis, model-checking, verification, calculation, reusable domain theories. * Formal methods in practice: experience with introducing formal methods in industry, case studies. * Role of formal methods: formal methods in hardware and system design, method integration, development process. TECHNICAL PAPERS Full papers should be submitted via the web site. Papers will be evaluated by the Program Committee according to their originality, significance, soundness, quality of presentation and relevance with respect to the main issues of the symposium. Accepted papers will be published in the Symposium Proceedings, to appear in Springer's Lecture Notes in Computer Science series, http://www.springeronline.com/lncs . Submitted papers should have not been submitted elsewhere for publication, should be in Springer's format, (see Springer's web site), and should not exceed 16 pages including appendices. A prize for the best technical paper will be awarded at the symposium. INDUSTRIAL USAGE REPORTS One day will be dedicated to sharing the experience -- both positive and negative -- with using formal methods in industrial environments. The Industry Day is organized by ForTIA, the Formal Techniques Industry Association, http://www.fortia.org . This year's Industry Day investigates the use of formal methods in security and trust. Invited papers on organizational and technical issues will be presented. Inquiries should be directed to the Industry Day Chairs; see the web site for details. WORKSHOPS We welcome proposals for one-day or one-and-a-half-day workshops related to FM'06. In particular, but not exclusively, we encourage proposals for workshops on various application domains. Proposals should be directed to the Workshop Chair. TUTORIALS We are soliciting proposals for full-day or half-day tutorials. The tutorial contents can be selected from a wide range of topics that reflect the conference themes and provide clear utility to practitioners. Each proposal will be evaluated on importance, relevance, timeliness, audience appeal and past experience and qualification of the instructors. Proposals should be directed to the Tutorial Chair. POSTER AND TOOL EXHIBITION An exhibition of both research projects and commercial tools will accompany the technical symposium, with the opportunity of holding scheduled presentations of commercial tools. Proposals should be directed to the Poster and Tools Exhibition Chair. DOCTORAL SYMPOSIUM For the first time, FM'06 will feature a doctoral symposium. Students are invited to submit work in progress and to defend it in front of "friendly examiners". Participation for students who are accepted will be subsidized. Submissions should be directed to the Doctoral Symposium Chair. SUBMISSION DATES Technical Papers, Workshops, Tutorials: Friday, February 24, 2006 Posters and Tools, Doctoral Symposium: Friday, May 26, 2006 NOTIFICATION DATES Technical Papers: Friday, April 28, 2006 Workshops, Tutorials: Friday, March 10, 2006 Posters and Tools, Doctoral Symposium: Friday, June 9, 2006 ORGANIZATION General Chair: Emil Sekerinski (McMaster) Program Chairs: Jayadev Misra (U. Texas, Austin), Tobias Nipkow (TU Munich) Workshop Chair: Tom Maibaum (McMaster) Tutorial Chair: Jin Song Dong (NUS) Tools and Poster Exhibition Chair: Marsha Chechik (U. Toronto) Industry Day Chairs: Volkmar Lotz (SAP France), Asuman Suenbuel (SAP US) Doctoral Symposium Chair: Augusto Sampaio (U. Pernambuco) Sponsorship Chair: Juergen Dingel (Queens U.) PROGRAM COMMITTEE Jean-Raymond Abrial (ETH Zurich) Alex Aiken (Stanford U.) Keijiro Araki (Kyushu U.) Ralph Back (Abo Akademi) Gilles Barthe (INRIA) David Basin (ETH Zurich) Ed Brinksma (U. Twente) Michael Butler (U. Southampton) Rance Cleaveland (U. Stony Brook) Jorge Cuellar (Siemens) Werner Damm (U. Oldenburg) Frank de Boer (U. Utrecht) Javier Esparza (U. Stuttgart) Jose Fiadeiro (U. Leicester) Susanne Graf (VERIMAG) Ian Hayes (U. Queensland) Gerard Holzmann (JPL) Cliff Jones (U. Newcastle) Gary T. Leavens (Iowa State U.) Rustan Leino (Microsoft) Xavier Leroy (INRIA) Dominique Mery (LORIA) Carroll Morgan (UNSW) David Naumann (Stevens) E.-R. Olderog (U. Oldenburg) Paritosh Pandya (TIFR) Sriram Rajamani (Microsoft) John Rushby (SRI) Steve Schneider (U. Surrey) Vitaly Shmatikov (U. Texas, Austin) Bernhard Steffen (U. Dortmund) P.S. Thiagarajan (NUS) Axel van Lamsweerde (U. Louvain) Martin Wirsing (LMU Munich) Pierre Wolper (U. Liege) LOCAL ORGANIZATION Publicity: Wolfram Kahl, Alan Wassyng, Jeff Zucker Tools, Posters, Book Exhibition: Spencer Smith Social Events: Ridha Khedri Local Arrangements:: William Farmer, Mark Lawford Events Co-ordinator: Ryszard Janicki

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Call for Participation: Functional and Declarative Programming in Education 2005
by S.J.Thompson 01 Aug '05

01 Aug '05

Functional and Declarative Programming in Education 2005 http://www.cs.kent.ac.uk/people/staff/sjt/fdpe05/ A one day workshop on Sunday, 25 September at ICFP05. REGISTRATION Registration for the workshop is through the TFP/ICFP/GPCE site: http://www.cs.ioc.ee/tfp-icfp-gpce05/ CALL FOR PARTICIPATION The aim of this workshop is to bring together educators and others who are interested in exchanging ideas on how to use a functional or declarative programming style in the classroom or in e-learning environments. PROGRAMME 9:00 Invited Talk: How to Design Class Hierarchies, Matthias Felleisen, Northeastern University 11:00 From Functional to Object-oriented Programming -- A Smooth Transition for Beginners, Rudolf Berghammer, Frank Huch 11:30 Laziness Without All the Hard Work: Combining Lazy and Strict Languages for Teaching, Eli Barzilay, John Clements 12:00 Word Puzzles in Haskell, Sharon A. Curtis 2:30 Teaching of Image Synthesis in Functional Style, Jerzy Karczmarczuk 3:00 MinCaml: A Simple and Efficient Compiler for a Minimal Functional Language, Eijiro Sumii 3:30 Engineering Software Correctness, Rex Page 4:30 'Tips and Tricks' session: contributions from attendees. 5:15 Round table discussion on links between FDPE and CUFP. The Organisers Robby Findler, Michael Hanus and Simon Thompson

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