- Haskell - Haskell.org

Re: no continuations
by Amr A Sabry 30 Dec '03

30 Dec '03

Kevin S. Millikin <kmillikin(a)atcorp.com> wrote: > Oh, sure. I didn't mean to quibble with the idea that continuations > are computational effects. Just wanted to point out that (I think) you > can't macro express mutation with call/cc, unless you've already got > mutation anyway. That's right: call/cc alone can't express assignments. But shift + reset will give you assignments. See Gunter, Remy, and Riecke, FPCA 95 for a clever encoding. --Amr

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RE: no continuations
by Kevin S. Millikin 30 Dec '03

30 Dec '03

On Tuesday, December 30, 2003 3:10 PM, Ben Rudiak-Gould [SMTP:benrg@dark.darkweb.com] wrote: > Interesting. > > This still violates referential transparency, though. (c 'get) returns > a value or errors out depending on whether (c 'set) has been called yet. Oh, sure. I didn't mean to quibble with the idea that continuations are computational effects. Just wanted to point out that (I think) you can't macro express mutation with call/cc, unless you've already got mutation anyway. > And take a look at this! > > > (define c (make-cell)) > > (define d c) > > ((d 'set) 9) > > (d 'get) > > Error in car: #<procedure> is not a pair. > Type (debug) to enter the debugger. > > Something very nasty is going on here. I'm not sure exactly what it > is, but I think at least one of the define statements is getting executed > at least twice. Yup. If you do that, you can use d as your setter and c as your getter: > (define c (make-cell)) > (define d c) > ((d 'set) 9) > (c 'get) 9 > ((d 'set) 17) > (c 'get) 17 Does this help?: > (define c (let ((cell (make-cell))) (display "Hi, Ben.") (newline) cell)) Hi, Ben. > (define d c) > ((d 'set) 9) Hi, Ben.

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RE: no continuations
by Kevin S. Millikin 30 Dec '03

30 Dec '03

On Tuesday, December 30, 2003 12:39 PM, Ben Rudiak-Gould [SMTP:benrg@dark.darkweb.com] wrote: > > With letrec and unrestricted call/cc you can implement ML-style refs: With an *implementation of letrec that uses mutation* and unrestricted call/cc, you can implement ML-style ref cells: Petite Chez Scheme Version 6.0a Copyright (c) 1998 Cadence Research Systems > (define-syntax letrec^ (syntax-rules () ((_ ((Var Exp)) Body Bodies ...) (let ((Y (lambda (f) ((lambda (g) (f (g g))) (lambda (g) (f (lambda (x) ((g g) x)))))))) (let ((Var (Y (lambda (Var) Exp)))) Body Bodies ...))))) > (letrec^ ((fact (lambda (n) (if (zero? n) 1 (* n (fact (- n 1))))))) (fact 5)) 120 > (define (make-cell) (call/cc (lambda (return-from-make-cell) (letrec^ ((state (call/cc (lambda (return-new-state) (return-from-make-cell (lambda (op) (case op ((set) (lambda (value) (call/cc (lambda (return-from-access) (return-new-state (list value return-from-access)))))) ((get) (car state))))))))) ((cadr state) 'done))))) > (define c (make-cell)) > ((c 'set) 3) > (c 'get) 3 > ((c 'set) 7) done > (c 'get) 3

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CFP for LDTA 2004
by jas＠di.uminho.pt 29 Dec '03

29 Dec '03

Apologies if you receive multiple copies of this message. ********************************************************** *** Fourth Workshop on *** *** Language Descriptions, Tools and Applications *** *** LDTA 2004 *** *** *** *** Satellite event of ETAPS 2004 *** *** *** *** In Co-Operation with ACM SIGPLAN (approved) *** *** *** *** APRIL, 3, 2004 *** *** BARCELONA, SPAIN *** *** *** *** http://www.di.uminho.pt/LDTA04 *** ********************************************************** IMPORTANT DATES December 1st 2003 Submission of full paper (closed) --> January 5th 2004 Submission of a tool demo paper (OPENED) January 15th 2004 Notification February 15th 2004 Final version due April 3rd 2004 LDTA 2004

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Perspectives on learning and using Haskell
by Graham Klyne 29 Dec '03

29 Dec '03

I've spent part of the past few months learning Haskell and developing a moderately sized application. I came to this from a long background (20 years or so) of "conventional" programming in a variety of languages (from Fortran and Algol W to Java and Python). For me, learning Haskell has been one of the steepest learning curves of any new language that I have ever learned. Before this project, I was aware of some aspects of functional programming, but had never previously done any "in anger" (i.e. for real). Throughout this period, I've been accumulating some notes about some things that I found challenging along the way. The notes are not organized in any way, and they're certainly not complete. I've published them on my web site [1] in case the perspective might be useful to any "old hands" here. [1] http://www.ninebynine.org/Software/Learning-Haskell-Notes.html ... Also on the topic of perspectives: In recent conversation with a colleague, he mentioned to me that the term "functional programming" has an image problem. He suggested that the term conveys an impression of an approach that is staid, non-progressive or lacking novelty, and is prone to elicit a response of "been there, done that" from programmers who don't realize the full significance of the term "functional". I've also noticed that when I talk about "functional programming", some people tend to think I'm talking about using techniques like functions in C or Pascal (which is course is very desirable, but old hat and not worthy of great excitement). #g ------------ Graham Klyne For email: http://www.ninebynine.org/#Contact

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How to make reading an array from disk more efficient
by andrew cooke 25 Dec '03

25 Dec '03

Hi, I have some code (http://www.acooke.org/andrew/ReadTest.hs) that reads data from a file (an image in ppm format; example data (256*256 pixels) at http://www.acooke.org/andrew/test.ppm) and stores it in an array of Word8 values. The aim is to read a file that contains 5000 * 5000 * 3 Word8 values. I think this should take under 100Mb of memory, if the Array implementation is efficient. However, when I run the code on a file of that size it looks like it will need several days to complete. This seems rather slow - the GIMP can read the same file maybe 30 seconds). How do I make the Haskell code faster while keeping it flexible? My requirements are: - machine limited to 1Gb memory - display "status bar" - the possibility to filter the pixel stream so that the image is subsampled (see "everyN" in the code) - the possibility to filter the pixel strean so that a subsection of the image is selected. All that is possible in the code I have now, but it's slow. Thanks, Andrew -- personal web site: http://www.acooke.org/andrew personal mail list: http://www.acooke.org/andrew/compute.html

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ANNOUNCE: GHC version 6.2
by Simon Marlow 25 Dec '03

25 Dec '03

============================================================ The (Interactive) Glasgow Haskell Compiler -- version 6.2 ============================================================ We are pleased to announce a new major release of the Glasgow Haskell Compiler (GHC), version 6.2. Highlights include: * Arrows syntax * New pragma: UNPACK for selectively unpacking strict constructor fields. * New option -e for giving an expression to evaluate on the command-line. * Portability improvements. GHC has been ported to a few new platforms. * Removal of obsolete features: _ccall_, _casm_, ``...''. * Many bugs fixed See the release notes for a full list of the changes: http://www.haskell.org/ghc/docs/latest/html/users_guide/release-6.2.html 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.

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First CFP: GPCE'04 -- Generative Programming and Component Engineering
by Eelco Visser 23 Dec '03

23 Dec '03

FIRST CALL FOR PAPERS ---------------------------------------------------------------------- Third International Conference on Generative Programming and Component Engineering (GPCE'04) Vancouver, October 24-28, 2004 co-located with OOPSLA 2004 http://gpce04.gpce.org ---------------------------------------------------------------------- ------------------------------------ Important Dates ------------------------------------ * Pre-submission: March 12, 2004 * Submission: March 19, 2004 ------------------------------------ Scope ------------------------------------ Generative and component approaches have the potential to revolutionize software development in a similar way as automation and components revolutionized manufacturing. Generative Programming (developing programs that synthesize other programs), Component Engineering (raising the level of modularization and analysis in application design), and Domain-Specific Languages (elevating program specifications to compact domain-specific notations that are easier to write and maintain) are key technologies for automating program development. GPCE arose as a joint conference, merging the prior conference on Generative and Component-Based Software Engineering (GCSE) and the Workshop on Semantics, Applications, and Implementation of Program Generation (SAIG). The goal of GPCE is to provide a meeting place for researchers and practitioners interested in cutting edge approaches to software development. We aim to foster further cross-fertilization between the software engineering research community on the one hand, and the programming languages community on the other, in addition to supporting the original research goals of both the GCSE and the SAIG communities. We seek papers both in software engineering and in programming languages, and especially those that bridge the gap and are accessible to both communities at the same time. ------------------------------------ Topics of Interest ------------------------------------ The conference solicits submissions related (but not limited) to: * Generative programming o Reuse, meta-programming, partial evaluation, multi-stage and multi-level languages, step-wise refinement o Semantics, type systems, symbolic computation, linking and explicit substitution, in-lining and macros, templates, program transformation o Runtime code generation, compilation, active libraries, synthesis from specifications, development methods, generation of non-code artifacts, formal methods, reflection * Generative techniques for o Product lines and architectures o Embedded systems o Model-driven architecture * Component-based software engineering o Reuse, distributed platforms, distributed systems, evolution, analysis and design patterns, development methods, formal methods * Integration of generative and component-based approaches * Domain engineering and domain analysis o Domain-specific languages (DSLs) including visual and UML-based DSLs * Separation of concerns o Aspect-oriented programming, feature-oriented programming, o Intentional programming, and multi-dimensional separation of concerns * Industrial applications Reports on applications of these techniques to real-world problems are especially encouraged, as are submissions that relate ideas and concepts from several of these topics, or bridge the gap between theory and practice. The program committee is happy to advise on the appropriateness of a particular subject. ------------------------------------ Paper Submission ------------------------------------ Authors are invited to submit a title and abstract by March 12, 2004, and a full paper by March 19, 2004. These deadlines are firm. Simultaneous submission to other venues and submission of previously published material are not allowed. Electronic submission will be required, except by special arrangement with the program chairs. Authors will be notified of acceptance by May 17, 2004. Final versions of accepted papers must be submitted by July 25, 2004. Accepted papers will appear in the conference proceedings published in the Springer-Verlag Lecture Notes in Computer Science (LNCS) series http://www.springer.de/comp/lncs/index.html. Submissions must be in PDF, must conform to the LNCS style, and be no longer than 15 pages. For the formatting details see http://www.springer.de/comp/lncs/authors.html. ------------------------------------ Other Contributions ------------------------------------ Work related to generative programming and component engineering can also be presented in other forms than papers. GPCE has separate days for tutorials and workshops. During the conference there are sessions for tool demonstrations and poster presentations. If you want to organize a workshop, present a tutorial, demonstration, or poster, see the information on the conference website for details about format and submission. Contact the relevant chair for more information. ------------------------------------ Important Dates ------------------------------------ Technical papers * Pre-submission: March 12, 2004 * Submission: March 19, 2004 * Notification: May 17, 2004 * Final version: July 25, 2004 Submissions of proposals * Workshops: March 19, 2004 * Practitioners: April 30, 2004 * Tutorials: April 30, 2004 * Demonstrations: July 2, 2004 Conference * Tutorials: October 24, 2004 * Workshops: October 25, 2004 * Papers: October 26-28, 2004 ------------------------------------ Organization ------------------------------------ General chair * Tim Sheard (OGI School of Science & Engineering at OHSU) Program committee chairs * Gabor Karsai (Vanderbilt University) * Eelco Visser (Utrecht University) Program committee * Uwe A�mann (Linkopings Universitet) * Don Batory (University of Texas) * Jan Bosch (Universiteit Groningen) * Jean Bezivin (Universit� de Nantes) * Jim Cordy (Queen's University) * Krzysztof Czarnecki (University of Waterloo) * Mathew Flatt (University of Utah) * Robert Glueck (University of Copenhagen) * George Heineman (Worcester Polytechnic Institute) * Michael Leuschel (University of Southampton) * Karl Lieberherr (Northeastern University) * Simon Peyton Jones (Microsoft Research) * Douglas R. Smith (Kestrel Institute) * Gabriele Taentzer (Technical University of Berlin) * Todd Veldhuizen (Indiana University) * Kris de Volder (University of Britisch Columbia) * Dave Wile (Teknowledge Corp.) * Alexander Wolf (University of Colorado at Boulder) Workshop Chair * Zino Benaissa (Intel) Tutorial Chair * Jeff Gray (University of Alabama at Birmingham) Demonstrations Chair * Simon Helsen (University of Waterloo) Contact * gpce-chairs(a)cs.uu.nl

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let-where difference
by Serge D. Mechveliani 22 Dec '03

22 Dec '03

The program f = [ 1, 2, (a+b where a = 1 b = 2 ) ] is qualified by some compilers as a wrong syntax. And f = [ 1, 2, (let a = 1 b = 2 in a+b ) ] is accepted. What may be the reason for such difference, is this a `bug' in Haskell-98 ? (Usually `let' and `where' are moved out of such a list construct, but for a large list with non-trivial expressions for the members, it may be natural to remain them). Thank you in advance for the explanation. Copy, please, the answer to mechvel(a)botik.ru ----------------- Serge Mechveliani mechvel(a)botik.ru

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HOR'04: first call for abstracts
by femke＠few.vu.nl 22 Dec '03

22 Dec '03

******************************** * * * HOR'04 CALL FOR ABSTRACTS * * * ******************************** 2nd international Workshop on Higher-Order Rewriting http://www-i2.informatik.rwth-aachen.de/HOR04/ IMPORTANT DATES: Mar 17 2004 : deadline electronic submission of paper Apr 9 2004 : notification of acceptance of papers Apr 23 2004 : deadline for final version of accepted papers The aim of HOR is to provide an informal and friendly setting to discuss recent work and work in progress concerning higher-order rewriting. INVITED TALKS: Mark-Oliver Stehr Hamburg (confirmed) (another person, to be confirmed) TOPICS of interest include (but are not limited to): APPLICATIONS: proof checking, theorem proving, generic programming, declarative programming, program transformation. FOUNDATIONS: pattern matching, unification, strategies, narrowing, termination, syntactic properties, type theory. FRAMEWORKS: term rewriting, conditional rewriting, graph rewriting, net rewriting, comparisons of different frameworks. IMPLEMENTATION: explicit substitution, rewriting tools, compilation techniques. SEMANTICS: semantics of higher-order rewriting, higher-order abstract syntax PROGRAM/ORGANIZING COMMITTEE: Delia Kesner Paris kesner(a)pps.jussieu.fr Femke van Raamsdonk Amsterdam femke(a)cs.vu.nl Joe Wells Edinburgh jbw(a)macs.hw.ac.uk HOR'04 SUBMISSIONS: Abstracts between 2 and 5 pages. As HOR is meant to be a platform to discuss ongoing research we are also interested in abstract describing work in progress, or problems in higher-order rewriting. PUBLICATION: The proceedings of HOR 2004 will be published as a technical report of the Computer Science Department of RWTH Aachen. LOCAL ARRANGEMENTS: Juergen Giesl RWTH Aachen, Germany giesl(a)informatik.rwth-aachen.de

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