September 2005 - Haskell

A Gentle Introduction to Haskell Version 98
by Wolfgang Jeltsch 14 Sep '05

14 Sep '05

Hello, the web page under http://haskell.org/tutorial/ says: This is the master HTML version of the Gentle Introduction To Haskell, version 98. Revised June, 2000 by Reuben Thomas. However, the Postscript, gezipped PDF, PDF and DVI versions don't mention Reuben Thomas as co-author and have October 1999 as their date. The downloadable HTML version doesn't mention Reuben Thomas too and has September 28, 1999 as its date. So what is true? Ist the online version different from the download versions and is the downloadable HTML version different from the other download versions? Did Reuben Thomas modify the tutorial? Which versions do contain his modifications, which not? Best wishes, Wolfgang

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RE: [Haskell] reading call graphs
by Simon Marlow 13 Sep '05

13 Sep '05

On 24 August 2005 11:10, Malcolm Wallace wrote: > "Scherrer, Chad" <Chad.Scherrer(a)pnl.gov> writes: > >> individual inherited >> COST CENTRE MODULE no. entries %time %alloc %time %alloc >> >> >> MAIN MAIN 1 0 0.0 0.0 100.0 100.0 >> main Main 228 92329 0.2 0.9 99.8 99.8 >> step Main 259 679 38.4 26.6 56.6 39.2 >> >> I'm trying to understand the "entries" column. I thought this was the >> number of times a given function is called. But "main" is >> nonrecursive, and only calls "step" (also nonrecursive) once. Where >> are the 92329 and 679 coming from? > > Perhaps these functions are split into smaller chunks by the > compiler/optimiser? Then the profiler would aggregate the data for > the individual chunks back up into the original cost centre. That's a plausible hypothesis. Each time an expression of the form ({-# SCC "foo" #-} e) is evaluated, the entries count for "foo" is incremented. The effect of -auto-all is to wrap each top-level function in an {-# SCC #-} expression, so you would normally get one entry per call of the function. However, the optimiser can change the structure of the code. Optimisations are supposed to retain the cost attribution model, but they don't necessarily retain the same entry counts. Basically I find the entries figure is a useful sanity check (i.e. "is this function called at all?"), but not much more than that. Cheers, Simon

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StringMaps available
by Adrian Hey 13 Sep '05

13 Sep '05

Hello, I've put the first release of Data.StringMap here.. http://homepages.nildram.co.uk/~ahey/HLibs/Data.StringMap/ The implementation is a bit different than what was discussed earlier as I decided the first version would burn heap unecessarily. It's still based on Tries though. I'm afraid I won't be able to do much Haskelling for a few months so not much will be added in the near future. But if anybody would like to use this but finds the absence of some function or other a show stopping issue then let me know and I'll add it. Regards -- Adrian Hey

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OOHaskell -- major release of report and library
by Ralf Lammel 13 Sep '05

13 Sep '05

An extended technical report has been released at: TR & software: http://homepages.cwi.nl/~ralf/OOHaskell/ TR: http://arxiv.org/abs/cs.PL/0509027 "Haskell's overlooked object system" 10 September 2005, 79 pages by O. Kiselyov (FNMOC, Monterey, CA, USA) and R. Laemmel (Microsoft Corp., WA, USA) Some recently added topics: - Many Haskell 98 encodings - Safe value recursion - Safe downcasts - Safe co-variant method arguments - Nominal subtyping - Iso-recursive object types - With and depth subtyping The report describes and classifies all principled, to our best knowledge, object encodings in Haskell98, with and without common extensions. On the one hand, this report covers many advanced topics, as to make it interesting for programming language researchers. On the other hand, the report is detailed and lightweight enough to be useful as an OO-FP tutorial. Regards, Oleg and Ralf

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ANNOUNCE: fps -- fast packed strings
by dons＠cse.unsw.edu.au 12 Sep '05

12 Sep '05

Hey. I've cabalised the FastPackedString module from darcs, used in h4sh, as the `fps' library. fps provides mmapped and malloc'd packed strings (byte arrays held by a ForeignPtr), along with a list interface to these strings. It lets you do extremely fast IO in Haskell. For example, the shell identity function written in Haskell (i): $ time cat 200M > /dev/null 0.00s user 0.19s system 2% cpu 6.481 total $ time i 200M > /dev/null 0.00s user 0.00s system 0% cpu 0.172 total $ time cat 200M > /tmp/f 0.00s user 0.38s system 1% cpu 27.932 total $ time i 200M > /tmp/f 0.00s user 0.48s system 7% cpu 6.454 total The FastPackedString module was originally written by Bryan O'Sullivan, it was rewritten to use UArray by Simon Marlow, then rewritten and extended to support slices, mmapping, ForeignPtrs and lots of other stuff by David Roundy and the darcs team. This version fixes a couple of bugs related to conformance to List, adds a testsuite, and makes the code conveniently available as a cabalised library. Get it: http://www.cse.unsw.edu.au/~dons/fps.html darcs get http://www.cse.unsw.edu.au/~dons/code/fps -- Don Stewart

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Uniqueness types for Haskell?
by Christian Stork 10 Sep '05

10 Sep '05

After looking at the language Clean (http://www.cs.ru.nl/~clean/) I wonder why there does not seem to be the desire to integrate uniquness typing into Haskell. Any ideas, pointers, comments? -- Chris Stork <> Support eff.org! <> http://www.ics.uci.edu/~cstork/ OpenPGP fingerprint: B08B 602C C806 C492 D069 021E 41F3 8C8D 50F9 CA2F

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SPACE 2006: Call for Papers
by David Walker 09 Sep '05

09 Sep '05

SPACE 2006 Third workshop on SEMANTICS, PROGRAM ANALYSIS, AND COMPUTING ENVIRONMENTS FOR MEMORY MANAGEMENT January 14, 2006 Charleston, South Carolina Sponsored by ACM/SIGPLAN http://www.itu.dk/research/plt/space2006/ ------------------------------------------------------------------------ Memory management is a difficult engineering task. We desperately need new tools and analyses that can identify memory management errors in low-level C/C++ code, such as dereferencing a pointer to an object that has been recycled or failing to reclaim an object. We also need new data structures and algorithms to avoid overheads such as fragmentation and synchronization. High-level languages such as Java or ML insulate the programmer from many of these problems through automatic memory management techniques (e.g., garbage collection). But standard GC techniques are not always suitable for all domains. For instance, programmers for embedded and real-time systems need static guarantees about resource requirements that are difficult to meet with standard collection algorithms. New languages, logics, analyses, and type systems are needed that let us reason about the management of memory, time, and other critical resources, whether using manual or automatic methods. The aim of this workshop is to bring together researchers for a fruitful exchange of ideas on semantics, program analysis and computing environments for memory management. SCOPE: Topics of interest include but are not limited to: * alternative memory management strategies (.e.g, region- or reap-based) * memory management for constrained (embedded, real-time, etc.) systems * analyses for optimization of memory management * analyses for faults in manual memory management * types, semantics, logics, and calculi for memory management * applications of statically controlled memory management * empirical results for new or existing memory management strategies TIME AND PLACE: The workshop takes place in Charleston, South Carolina on January 14, 2006. It is co-located with POPL 2006, which takes place January 11-13, 2006. IMPORTANT DATES: * Submission deadline: midnight EST, Thursday, November 10, 2005 * Electronic PC meeting: Monday/Tuesday, November 28/29, 2005 * Notification: Tuesday, December 2, 2005 * Final copy: midnight, Friday, December 16, 2005 * Workshop: Saturday, January 14, 2006 FORMAT: The workshop will consist of: * 25-minute presentations by authors of selected, peer-reviewed papers * 10-minute short presentations (non-peer reviewed) * two 45-minute invited talks (to be determined) * a series of "5-minute madness" talks as time permits The long papers will be selected by a program committee and only "lightly" reviewed. Our goal in selecting papers is to meet our time requirements and present a balanced program. We hope to include all of the short presentations, but may be forced to select a subset depending on the number of submissions. Again, our goal is to have a productive, interactive workshop. At lunch-time, participants will be able to sign up for a "5-minute madness" talk slot (as time permits). These talks will be limited to at most 2 viewgraphs and are meant to give a brief, perhaps provocative, viewpoint on the research issues in memory management and to spark conversation. A moderator will limit time according to the excitement generated by the presentation. INFORMAL PROCEEDINGS: We will distribute an informal proceedings at the workshop only. We do not consider the proceedings to be a formal (citable) publication so that any works in progress presented here may be submitted later for formal publication. The informal proceedings for the workshop will consist of the accepted papers, and titles and abstracts for the short presentations. LONG PAPERS: Authors should submit a 12 page extended abstract formatted using the ACM LaTeX sig-alternate format (http://www.acm.org/sigs/pubs/proceed/template.html) Accepted final papers will be allowed to be longer (up to 20 pages). SHORT PRESENTATIONS: Authors should submit a 2-3 page abstract formatted using the ACM LaTeX sig-alternate format (http://www.acm.org/sigs/pubs/proceed/template.html) The title should start with "Short Presentation: ". INFORMATION: Please refer to the workshop home page at http://www.itu.dk/research/plt/space2006 for up-to-date information on location, invited talks, participation, and so on. REGISTRATION: For information on registration, accommodation etc, please refer to the POPL 2006 conference web pages. STEERING COMMITTEE: * Fritz Henglein, Dept. of Computer Science, University of Copenhagen * Richard Jones, Computing Laboratory, University of Kent * Greg Morrisett, Division of Engineering and Applied Science, Harvard University * Peter O'Hearn, Dept. of Computer Science, Queen Mary, University of London PROGRAM CHAIRS: * Martin Elsman, IT University of Copenhagen * David Walker, Princeton University PROGRAM COMMITTEE: * Amal Ahmed, Harvard University * Perry Cheng, IBM (T.J. Watson Research Center) * Martin Elsman, IT University of Copenhagen * Philippa Gardner, Imperial College * Michael Hicks, University of Maryland * Martin Hofmann, Ludwig-Maximilians-Universität München * Atsushi Igarashi, Kyoto University * Mooly Sagiv, Tel-Aviv University * David Walker, Princeton University PREVIOUS SPACE WORKSHOPS: The first SPACE workshop was held in connection with POPL 2001 at Imperial College, London, January 15-16, 2001. The second SPACE workshop was held in connection with POPL 2004 in Venice, Italy, January 12, 2004.

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ANNOUNCE: Gtk2Hs special release with cairo support
by Duncan Coutts 09 Sep '05

09 Sep '05

To mark the end of Paolo Martini’s project to add support for the cairo vector graphics library (cairographics.org) we are pleased to announce a special “tech preview” release of Gtk2Hs including Paolo’s contributions. Here’s a screenshot from a demo program Paolo and others wrote to show off the combination of Haskell, cairo and Gtk+. http://haskell.org/gtk2hs/gallery/Cairo-demo/Cairo_demo_13 You can see more of his latest screenshots in his blog. http://haskell.org/gtk2hs/archives/category/cairo/ As of version 2.8, Gtk+ now depends on cairo and uses it for much of it’s drawing. It is a great advance over Gtk’s previous drawing API. The cairo website describes it thusly: Cairo is a 2D graphics library with support for multiple output devices. Currently supported output targets include the X Window System, win32, and image buffers. Experimental backends include OpenGL (through glitz), Quartz, XCB, PostScript and PDF file output. Cairo is designed to produce consistent output on all output media while taking advantage of display hardware acceleration when available (for example, through the X Render Extension). The cairo API provides operations similar to the drawing operators of PostScript and PDF. Operations in cairo including stroking and filling cubic Bézier splines, transforming and compositing translucent images, and antialiased text rendering. All drawing operations can be transformed by any affine transformation (scale, rotation, shear, etc.). We encourage anyone who has Gtk+ 2.8 installed to give this Gtk2Hs release a try and to experiment with using the cairo drawing API. Bug reports and cool screenshots will be gratefully accepted. Download: http://haskell.org/gtk2hs/gtk2hs-0.9.9.5.tar.gz The release includes some demos showing how to use cairo in a stand alone fashion to produce PNG image files and also demos showing how to use the cairo API for drawing in a Gtk+ GUI (both real-time and non-real-time). There is also some preliminary reference documentation available: http://haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.9.5/ This release is not intended for packaging for distros. The next ordinary release will of course retain the cairo support. It is intended that the cairo package will eventually be distributed separately since it is useful in non-GUI programs too. This project was undertaken by Paolo as part of Google’s Summer of Code programme. In our opinion his project has been a success and so we would like to recommend to Paolo’s official mentor at Google and the judges that he be counted amongst the successful SoC programme participants and awarded the full project grant. Duncan (on behalf of the Gtk2Hs team)

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mailing list headaches
by Frederik Eaton 08 Sep '05

08 Sep '05

Hi all, I've been trying for some time to get threading to work properly on this mailing list. The problem is that I don't want to thread by subject in all of my folders, because then messages with short subjects like "hi", "hey", etc., in my personal folders will end up together. However, threading by "References", which RFC 2822 says SHOULD be possible, and which works on my other folders, doesn't work well on Haskell mailing lists. Presumably the issue is that there are a large number of Windows users with strange mail clients which don't insert "References" headers. After some weeks of squinting, I've ended up settling with the following partial solution in my configuration files (I use Mutt): set strict_threads=yes folder-hook folders/haskell set strict_threads=no folder-hook folders/libraries set strict_threads=no folder-hook folders/glasgow-haskell set strict_threads=no folder-hook folders/glasgow-haskell-bugs set strict_threads=no I thought I'd share this feature because a lot of people use Mutt and it makes the Haskell mailing lists a bit easier to follow. It isn't perfect, because threads organized by subject are only one layer deep - you end up getting a list instead of a tree, except that since Mutt uses References where possible it ends up being a list of trees, where at the root of each tree is either a reply to the first message of the thread, or someone with a non-conforming mail client. Of course, another problem is the mailing list archives, which also try to organize threads by "References" but fail on these lists: http://www.haskell.org/pipermail/glasgow-haskell-users/2005-June/thread.html Thus it seems the list archive software also requires fixing or reconfiguration... Frederik -- http://ofb.net/~frederik/

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ESOP 2006 Call for papers
by Peter Sestoft 07 Sep '05

07 Sep '05

Call for Papers ESOP 2006: The European Symposium on Programming http://www.itu.dk/research/esop06/ Affiliated with ETAPS'06 Vienna, Austria, 25 March to 2 April 2006 CONFERENCE DESCRIPTION ESOP is an annual conference devoted to fundamental issues in the specification, analysis, and implementation of programming languages and systems. This includes: * design of programming languages and calculi and their formal properties * techniques, methods, and tools for their implementation * exploitation of programming styles within different programming paradigms * automatic and manual methods for generating and reasoning about programs * the design and invention of systems and tools to assist in exploitation of the languages Contributions bridging the gap between theory and practice are particularly welcome. Topics traditionally covered by ESOP include programming paradigms and their integration, semantics, calculi of computation, security and privacy, advanced type systems, program analysis, program transformation, and practical algorithms based on theoretical developments. More information about ESOP can be found at ESOP's home page: http://www.imm.dtu.dk/~riis/esop.html ESOP'06 is one of the main conferences of ETAPS'06 with sister events CC, FASE, FOSSACS, TACAS, see: http://www.complang.tuwien.ac.at/etaps06/ IMPORTANT DATES Friday 7 October 2005 Submission deadline for abstracts Friday 14 October 2005 Submission deadline for full papers (strict) Friday 9 December 2005 Notification of acceptance/rejection Friday 6 January 2006 Camera-ready version due Saturday 25 March to Sunday 2 April 2006 ETAPS 2006 SUBMISSION INFORMATION ETAPS conferences accept two types of contributions: research papers and tool demonstration papers. Both types will appear in the proceedings and have presentations during the conference. A condition of submission is that, if the submission is accepted, one of the authors attends the conference to give the presentation. All submitted papers must be unpublished and not submitted for publication elsewhere. In particular, simultaneous submission of the same contribution to multiple ETAPS conferences is forbidden. Papers should be submitted electronically in PDF (preferably) or PS (using Type 1 fonts). The proceedings will be published in the Springer-Verlag Lecture Notes in Computer Science series. Final papers will be in the format specified by Springer-Verlag at the URL: http://www.springer.de/comp/lncs/authors.html It is recommended that submissions adhere to the specified format and length. Submissions that are clearly too long may be rejected immediately. A link to the electronic submission system will available shortly on the ESOP 2006 home page (http://www.itu.dk/research/esop06/) RESEARCH PAPERS: Final papers will be not more than 15 pages long, and should present original research. Additional material intended for the referee but not for publication in the final version - for example details of proofs - may be placed in a clearly marked appendix that is not included in the page limit. TOOL DEMONSTRATION PAPERS: Submissions should consist of two parts: The first part, at most four pages, should describe the tool presented. Please include the URL of the tool (if available) and provide information which illustrates the maturity and robustness of the tool. (This part will be included in the proceedings.) The second part, at most six pages, should explain how the demonstration will be carried out and what it will show, including screen dumps and examples. (This part will be not be included in the proceedings, but will be evaluated.) ESOP 2006 INVITED SPEAKER Sophia Drossopoulou, Imperial College London, UK ETAPS 2006 JOINT INVITED SPEAKERS Carlo Ghezzi, Politecnico di Milano, Italy Benjamin Pierce, University of Pennsylvania, USA ESOP 2006 PROGRAM COMMITTEE Anindya Banerjee, Kansas State University, USA Anton Ertl, Technische Universität Wien, Austria David Warren, Stony Brook University, USA Didier Rémy, INRIA Rocquencourt, France Erik Meijer, Microsoft Corporation, USA Eugenio Moggi, University of Genova, Italy German Vidal, Technical University of Valencia, Spain Giuseppe Castagna, École Normale Supérieure, France Joe Wells, Heriot-Watt University, UK Kostis Sagonas, Uppsala University, Sweden Michele Bugliesi, University of Venezia, Italy Mooly Sagiv, Tel-Aviv University, Israel Nick Benton, Microsoft Research, UK Peter O'Hearn, Queen Mary, University of London, UK Peter Sestoft, KVL and IT University Copenhagen, Denmark Peter Stuckey, Melbourne University, Australia Peter Thiemann, Freiburg University, Germany Pieter Hartel, Twente University, Netherlands Reinhard Wilhelm, Saarland University, Germany Stephanie Weirich, University of Pennsylvania, USA Susan Eisenbach, Imperial College London, UK Todd Veldhuizen, Indiana University, USA Ulrik Pagh Schultz, University of Southern Denmark Chair: Peter Sestoft, KVL and IT University Copenhagen, Denmark

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