March 2004 - Haskell - Haskell.org

Mixing monadic and non-monadic functions
by Sean E. Russell 17 Sep '05

17 Sep '05

Hello, I posted this question to comp.lang.functional, and someone suggested that I try this group instead. I'm struggling with monads. Well, not monads themselves, but mixing them with non-monadic functions. Here's my base case: someFunc :: String -> IO [a] ... ax <- someFunc a bx <- someFunc b assertBool "fail" $ length ax == length bx I don't like the assignments; the typing is redundant, if I have a lot of asserts like this, and the "variables" are temporary. What I'd much rather have is: ... assertBool "fail" $ (length $ someFunc a) == (length $ someFunc b) which is more readable, to my eye. The only solution which has been suggested that may work is liberal use of the liftM variants, but this gets *really* tedious and obtuse. Is there an elegant way to do what I want to do, or am I stuck with procedural-style assignments and bunches of temp vars? Thanks! -- ### SER ### Deutsch|Esperanto|Francaise|Linux|XML|Java|Ruby|Aikido ### http://www.germane-software.com/~ser jabber.com:ser ICQ:83578737 ### GPG: http://www.germane-software.com/~ser/Security/ser_public.gpg

23 37

WS-FM 2004 Call For Participation
by Mario Bravetti 20 Jul '05

20 Jul '05

---------------------------------------------------------------------- We apologize if you receive multiple copies of this announcement. ---------------------------------------------------------------------- ====================================================================== 1st International Workshop on Web Services and Formal Methods (WS-FM 2004) February 23-24, 2004, Pisa, Italy Workshop affiliated to COORDINATION 2004, February 24-27, 2004 WS-FM 2004 homepage: http://www.cs.unibo.it/~lucchi/ws-fm04/ ====================================================================== - The technical program is available at: http://www.cs.unibo.it/~lucchi/ws-fm04/ - Information about registration, travel and accomodation can be found at the COORDINATION 2004 web site: http://www.di.unipi.it/Coordination2004/ If you intend to participate, we recommend you to register and book the hotel as soon as possible. The Coordination 2004 Organizing Committee informed us that hotels are going to be fully booked in short time.

1 1

CfP: SNPD'03 Workshop on High-Level Approaches to Parallel and Distributed Computing
by Clemens Grelck 08 Jul '04

08 Jul '04

Please apologize in case you receive multiple copies of this information. ========================================================================== CALL FOR PAPERS Workshop on High-Level Approaches to Parallel and Distributed Computing held in the context of the Fourth ACIS International Conference on Software Engineering, Artificial Intelligence, Networking, and Parallel/Distributed Computing (SNPD'03) October 16th - 18th, 2003 Luebeck, Germany http://www.isp.uni-luebeck.de/snpd03/Workshop/ws02/index.htm ========================================================================== Scope and Topics: ================== Today parallel and distributed computing systems are readily available and provide a continuously improving price/performance ratio. However, this technological breakthrough in hardware is not accompanied by similar progress in software technology. Parallel and distributed programming is still dominated by low-level techniques such as explicit message passing. This low level of abstraction makes programming these systems exceedingly difficult, time-consuming, and error-prone. Hence, parallel and distributed computing requires new programming models which liberate programmers from low-level concerns and increase programming productivity while maintaining reasonable trade-offs between level of abstraction and runtime performance. Topics of interest include, but are not limited to - methodologies for high-level parallel programming, - parallel programming languages, - high-level libraries for parallel computing, - compilers and runtime systems for parallel computing, - implementation aspects of high-level parallel programming environments, - compiler-based optimization and parallelization, - experience with high-level parallel programming environments, - support for debugging and performance analysis, - concurrent array programming, - programming concepts for the grid. This workshop provides a forum for researchers and practitioners interested in the design, implementation, and evaluation of high-level parallel programming concepts. It aims at creating some focus within the otherwise broad spectrum of the SNPD'03 conference. Workshop Chair and Organizer: ============================== Clemens Grelck University of Luebeck Institute of Software Technology and Programming Languages Seelandstr. 1A 23569 Luebeck, Germany E-Mail: grelck(a)isp.uni-luebeck.de Papers and Publication: ======================== Original, unpublished papers in English not exceeding 8 pages in ACIS double column format are solicited. For detailed formatting instructions see the SNPD'03 conference web site at http://www.isp.uni-luebeck.de/snpd03/index.htm Please send your papers as PDF documents by electronic mail directly to the workshop chair: grelck(a)isp.uni-luebeck.de Please indicate your paper submission by the subject SNPD03 WORKSHOP SUBMISSION Accepted papers will be published in the conference proceedings with ISBN. A selection of excellent papers presented at the conference including its workshops will be published in a special issue of the International Journal of Computer and Information Science. Important Deadlines: ===================== Full paper submission due: August, 30th Notification of acceptance: September, 10th Camera-ready papers due: September, 24th

1 3

ICFP Poster Session
by Amr A Sabry 17 Jun '04

17 Jun '04

The 2004 ICFP Poster Session http://abstract.cs.washington.edu/~djg/icfp-poster.html Part of the 2004 International Conference on Functional Programming http://www.cs.indiana.edu/icfp04/ The 2004 International Conference on Functional Programming (ICFP) will include a poster session during the first day of the conference. The poster session aims to give students and professionals an opportunity to gain experience presenting technical material to the research community, and to get technical advice from leading researchers in the field. PARTICIPANT OBLIGATIONS: * Sign-up via the on-line form below by June 30, 2004. * Submit a one-page abstract summarizing the poster topic by July 15, 2004. * Register for ICFP 2004. (There is no separate poster registration beyond the on-line sign-up form.) * Prepare a poster and attend the session on September 19, 2004. In addition, participants are strongly encouraged to prepare a short article (roughly 2 or 3 pages) for peer feedback and to provide feedback for some other participants' articles. This process should improve the quality of the posters. Articles should be submitted by August 1, 2004. NUMBER OF PARTICIPANTS: * We hope to accomodate everyone wishing to participate, but may restrict participation (based on relevance and interest to the community) in the case of unmanageably high interest. * We may need to cancel the session if there is too little interest, roughly fewer than ten participants. * To ensure we know there is interest, please sign-up promptly. Somebody has to be first and there is no danger you will be the sole participant. POSTER PRESENTATIONS: In the poster session, each participant will be provided with a space for posting their diagrams and short descriptions of their research (approximately 3x6 feet, or 1x2 meters). Contact with your audience happens through casual conversation. Count on only a reasonable attention span when describing your work. Over five minutes is usually overdoing it. Prepare a list of questions that you would like help getting answered. Please feel free to direct any questions that you might have to: Dan Grossman, ICFP2004 Poster Session Chair http://www.cs.washington.edu/homes/djg

2 1

[Haskell] Programming language shootout (completing the Haskell entry)
by Sean E. Russell 14 Jun '04

14 Jun '04

Hiya, I know it is silly, but I'm interested in helping to complete the Haskell entry in the Programming Language Shootout page[1] (http://www.bagley.org/~doug/shootout/craps.shtml) The Haskell entry is missing 5 (out of 13) entries, and since no points are "scored" for missing entries, this skews Haskell's rank downwards. Since I'm not the worlds Best Haskell Programmer -- and I'm certainly not adept at optimizing, and since I'd like to provide the fastest Haskell code that I can, I thought I'd run it through my code through this list and see if anybody would like to suggest improvements. The implementations for this particular test must be written in the "same way"; this is defined to be that the submissions "use the same logic and data structures", the goal being to "try to measure languages doing the same operations, as closely as possible." The "description" of the test is: "In this test, we create 10000 hash entries, then add them into a new hash N times. " The correct output for this code where N=10 must be: 1 9999 10 99990 I chose to use (lookup) and associative arrays. I create a *bunch* of hashes, rather than just two that I re-use because, honestly, I'm such a novice I don't know how to do it otherwise. Anyway, as I said, any suggestions for optimization are appreciated. This is just for fun. ===== BEGIN hash2.hs module Main where import System (getArgs) import Numeric (readDec) import Maybe main = do argv <- getArgs let h1 = hash1 9999 [] h2 = hash2 (fst $ head $ readDec $ argv!!0) h1 [] print h1 h2 where hash1 0 x = x hash1 n xs = hash1 (n-1) ((mkentry n):xs) mkentry y = ( "foo_"++(show y), y ) hash2 0 _ x2 = x2 hash2 n x1 x2 = hash2 (n-1) x1 [ (k1, v1+(get k1 x2)) | (k1, v1) <- x1 ] print x1 x2 = putStrLn ( (show $ get "foo_1" x1)++" "++ (show $ get "foo_9999" x1)++" "++ (show $ get "foo_1" x2)++" "++ (show $ get "foo_9999" x2) ) get :: String -> [(String, Int)] -> Int get key hash = fromMaybe 0 $ lookup key hash ===== END hash2.hs [1] The page is entirely tounge-in-cheek, but I find it interesting, nonetheless. -- ### SER ### Deutsch|Esperanto|Francaise|Linux|XML|Java|Ruby|Aikido ### http://www.germane-software.com/~ser jabber.com:ser ICQ:83578737 ### GPG: http://www.germane-software.com/~ser/Security/ser_public.gpg

9 12

ANNOUNCE: GHC version 6.2.1
by Simon Marlow 26 Apr '04

26 Apr '04

============================================================ The (Interactive) Glasgow Haskell Compiler -- version 6.2.1 ============================================================ We are pleased to announce a new patchlevel release of the Glasgow Haskell Compiler (GHC), version 6.2.1. As usual for patchlevel releases, this is mainly a bugfix release and should not break any code that was working with the previous major release (6.2). We did sneak a couple of new features into the compiler: - The "threaded runtime system" is included by default. To link a program with this variant of the RTS, add the -threaded option when linking. The main advantage of the threaded RTS is that it allows calls to foreign functions which block, while allowing other concurrent Haskell threads to continue running. - A debugging variant of the RTS is also included. Use -debug when linking to get it. The debugging RTS includes lots of sanity checking and has some extra options for producing debugging output while your Haskell program is running. How to get it ~~~~~~~~~~~~~ The easy way is to go to the WWW page, which should be self-explanatory: http://www.haskell.org/ghc/ We supply binary builds in the native package format for various flavours of Linux and BSD, and in Windows Installer (MSI) form for Windows folks. Binary builds for other platforms are available as a .tar.gz which can be installed wherever you want. The source distribution is also available from the same place. Packages will appear as they are built - if the package for your system isn't available yet, please try again later. Background ~~~~~~~~~~ Haskell is a standard lazy functional programming language; the current language version is Haskell 98, agreed in December 1998 and revised December 2002. GHC is a state-of-the-art programming suite for Haskell. Included is an optimising compiler generating good code for a variety of platforms, together with an interactive system for convenient, quick development. The distribution includes space and time profiling facilities, a large collection of libraries, and support for various language extensions, including concurrency, exceptions, and foreign language interfaces (C, whatever). GHC is distributed under a BSD-style open source license. A wide variety of Haskell related resources (tutorials, libraries, specifications, documentation, compilers, interpreters, references, contact information, links to research groups) are available from the Haskell home page (see below). On-line GHC-related resources ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Relevant URLs on the World-Wide Web: GHC home page http://www.haskell.org/ghc/ Haskell home page http://www.haskell.org/ comp.lang.functional FAQ http://www.cs.nott.ac.uk/~gmh/faq.html System requirements ~~~~~~~~~~~~~~~~~~~ To compile programs with GHC, you need a machine with 64+MB memory, GCC and perl. This release is known to work on the following platforms: * i386-unknown-{linux,*bsd,mingw32} * sparc-sun-solaris2 * alpha-dec-osf3 * powerpc-apple-darwin (MacOS/X) Ports to the following platforms should be relatively easy (for a wunderhacker), but haven't been tested due to lack of time/hardware: * hppa1.1-hp-hpux{9,10} * i386-unknown-solaris2 * mips-sgi-irix{5,6} * {rs6000,powerpc}-ibm-aix The builder's guide on the web site gives a complete run-down of what ports work; it can be found at http://www.haskell.org/ghc/docs/latest/html/building/building-guide.html Mailing lists ~~~~~~~~~~~~~ We run mailing lists for GHC users and bug reports; to subscribe, use the web interfaces at http://www.haskell.org/mailman/listinfo/glasgow-haskell-users http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs There are several other haskell and ghc-related mailing lists on www.haskell.org; for the full list, see http://www.haskell.org/mailman/listinfo/ Please report bugs using our SourceForge page at http://sourceforge.net/projects/ghc/ or send them to glasgow-haskell-bugs(a)haskell.org. GHC users hang out on glasgow-haskell-users(a)haskell.org. Bleeding edge CVS users party on cvs-ghc(a)haskell.org.

3 2

Announcing Pan# 1.0
by John Peterson 01 Apr '04

01 Apr '04

Announcing Pan# 1.0 Pan# is a new front end for Conal Elliott's Pan system. Pan# is a stand-alone system that displays interactive functional images expressed in a slightly augmented Haskell subset. Pan# is ideal for demonstrating the core principles of functional programming in an interesting and creative manner. Features of this release include: * All examples from Conal's Fun of Programming chapter * Many examples stolen from Jerzy Karczmarczuk's functional textures work * Full type checking * New user interface controls (random numbers, Haskore timing tracks) * More Haskell features * Movie making capabilities * Improved viewer * Simplified syntax for monadic code Pan# runs on Windows and uses the .NET system for dynamic compilation. It has not yet been ported to Linux or Macs but if you're familiar with the open source .NET systems we would be glad to help someone move Pan# to other operating systems. Pan# is easy to install and use. It has been tested with high school students and has proven to be an effective vehicle for introducing novices to the basics of computer programming without getting wrapped up in the endless details of visual Basic or other "industrial strength" computer languages. Because functional programming is very close to mathematics, Pan# does not need to introduce unfamiliar computational paradigms to students. We are also investigating the use of Pan# as an instructional tool for high school mathematics - some examples of this are included in the distribution. You can download Pan# at http://haskell.org/edsl/pansharp.html Thanks to Microsoft Research for supporting this project. John Peterson, Yale Haskell Group peterson-john(a)cs.yale.edu

2 2

ANNOUNCE: HaskellDB 0.7
by Bjorn Bringert 31 Mar '04

31 Mar '04

We are pleased to announce the third alpha release of our "remake" of HaskellDB, version 0.7. HaskellDB is available for download from http://haskelldb.sourceforge.net/ HaskellDB is a Haskell library for expressing database queries and operations in a type safe and declarative way. HaskellDB compiles a relational algebra-like syntax into SQL, submits the operations to the database for processing, and returns the results as ordinary Haskell values. The original version of HaskellDB was written by Daan Leijen and is available at http://www.haskell.org/haskellDB/. The implementation is based on his paper which can be found at: http://www.cs.uu.nl/people/daan/download/papers/dsec.ps New in HaskellDB 0.7: - Added functions for creating and dropping tables and databases. Too be improved in future releases. - Support for wxHaskell with GHC. - Untyped support for SQLite, thanks to a patch from Jeremy Shaw. - Overloaded (!) can be used for both (!) and (!.). - Compiling for Hugs does not require GHC. - Added function for converting from nullable types. Suggested by Shae Erisson. - Added case construct. - A GenericConnect is now available. Uses similar syntax to DBDirect. - Backend interface changed to make function types backend independent. - Queries now return records instead of backend specific types. NOTE: Due to changes in DbDirect, any files generated using the old version of HaskellDB may have to be regenerated. The developers can be reached at haskelldb-users(a)lists.sourceforge.net or on #haskelldb at irc.freenode.net. / The HaskellDB development team

1 0

RE: [Haskell] Programming language shootout (completing the Haskell entry)
by Simon Marlow 31 Mar '04

31 Mar '04

> On Tue, 30 Mar 2004, Simon Marlow wrote: > > > The upshot of what he found is that we could benefit from some > > prefetching, perhaps on the order of 10-20%. Particularly > prefetching > > in the allocation area during evaluation, to ensure that > memory about to > > be written to is in the cache, and similar techniques > during GC could > > help. However, actually taking advantage of this is quite hard - > > prefetching instructions aren't standard, and even when > they are getting > > any benefit can depend on cache architecture and other effects which > > vary between processor families. Getting things wrong > often results in > > a slowdown. It's just too brittle. > > Exactly: prefetching sucks, particularly for a compiler supporting > multiple architectures, using native and via-C compilation. > > Simon, did you ever try separating the code and data for each closure? Not recently. But I'd be very surprised if things have changed: the cache benefits need to be pretty big to outweigh the slowdown caused by the extra indirection when entering a closure. Cheers, Simon

1 0

[Haskell] insufficiently laziness@pattern -- more counterintuitive stuff
by S. Alexander Jacobson 31 Mar '04

31 Mar '04

I would assume that this function: foo list@(h:t) = list is equivalent to foo list = list where (h:t)=list But passing [] to the first generates an error even though h and t are never used! Passing [] to the second works just fine. At this point, I sort of understand the reason for MR and not having partially applied type synonyms, but this seems entirely like an issue of syntactic sugar.... FYI, I encountered this issue attempting to write code that merges the content of two lists of tuples e.g. merge left@((xL,yL):restL) right@((xR,yR):restR) | left==[] = .... I imagine this issue is fairly common so perhaps its another idiom issue. -Alex- PS This code is part of a joinSets function for data.Sets _________________________________________________________________ S. Alexander Jacobson mailto:me@alexjacobson.com tel:917-770-6565 http://alexjacobson.com

8 7