April 2009 - Haskell - Haskell.org

seeking papers with good examples of the use of GADTs
by nr＠cs.tufts.edu 13 Apr '09

13 Apr '09

I have a class of beginning functional programmers; we're approaching end of term, and I'd like them to learn about GADTs. One of my goals in the class is to give students practice learning by reading papers, so I am asking for recommendations of papers that have good examples of GADTs in action. Papers I've used in the past have included Pottier and Gauthier 2005: Polymorphic Typed Defunctionalization and Concretization, in Higher-Order and Symbolic Computation Pottier and Régis-Gianas 2006: Towards Efficient, Typed LR Parsers, in Electr. Notes Theor. Comput. Sci and Peyton Jones et al. 2006: Simple unification-based type inference for GADTs, in the 11th ACM SIGPLAN International Conference on Functional Programming. Unfortunately the first two rely on concepts in which my students have little background (LR parsing and defunctionalization respectively), and the the third, while it opens with a nice example, is primarily about the (now obsolete) type-inference algorithm, rather than about how to use GADTs. I am hoping some of you may have suggestions about other papers that would be good tutorials in the use of GADTs. Norman

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how can I refer to a symbol in a module that is imported 'qualified'?
by nr＠cs.tufts.edu 12 Apr '09

12 Apr '09

I need to resolve a name clash between two different Haskell modules that want to use the same infix operator (<*>). The Haskell 98 report says that modid.varsym is permitted, but I can't get it to work. In their entirety here are Test.hs: module Test where import qualified Test2 as T three = T.<*> and Test2.hs: module Test2 where (<*>) = 3 But trying to compile results in an error message: Test.hs:6:12: parse error on input `T.<*>' I tried T.(<*>) but that doesn't work either (as indeed the Haskell 98 report says it should not). How can I refer to a symbolic name defined in a module imported by `import qualified`? Norman

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ANN xmobar-0.9.2
by Andrea Rossato 11 Apr '09

11 Apr '09

Hi, I'm glad to announce xmobar-0.9.2. What's new: - Norbert Zeh tracked and fixed a longstanding bug that made xmobar leak X resources. This alone makes it worth this release and its public announcement, with the advice to users to upgrade.[*] - Norbert also overhauled the template parser to allow nested color definitions; - Norbert, once again, added the possibility to add color definitions in the monitors' templates. Many thanks to Norbert!! I've read that xmobar lists in the top 25 most downloaded Hackage packages. This is very cool: thanks to all the xmobar users. Hope you'll enjoy. Andrea [*] I tend to believe the same issue affects xmonad, even though it should be visible only after a huge number of restarts. Things get far worse when it comes to the xmonad-contrib library, especially if you use fancy decorations in your layouts: if you see colors you are probably leaking them.

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Hac5 is almost upon us!
by Sean Leather 11 Apr '09

11 Apr '09

In six days, tens of crazy/obsessed, type-safe, functional programmers will be converging on Utrecht to commence execution of... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The 5th Haskell Hackathon April 17 - 19, 2009 Utrecht, The Netherlands ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The local organizing team welcomes you all and looks forward to all of the new developments that come out of everyone's undying quest to write more and better code. As always, you can find lots of useful information on the wiki: http://haskell.org/haskellwiki/Hac5 == Sponsors == We have sponsors! The following companies were very gracious to provide us with support during these tough economic times. * Galois - http://galois.com/ * Microsoft Research - http://research.microsoft.com/ * Tupil - http://tupil.com/ The organizers are incredibly grateful to Galois, MSR, and Tupil for helping to encourage and promote more Haskell hacking. == More To Come == Hopefully, you have already registered, booked your room, and bought your ticket. If not, don't forget that you can keep in touch with the attendees via IRC on Freenode: #haskell-hac5 All registered attendees will soon be receiving an email with more details. Let us know if you have any questions. Happy Hacking! == Organizers == Andres Löh, Utrecht University (UU) José Pedro Magalhães, UU Sean Leather, UU Eelco Lempsink, UU + Tupil Chris Eidhof, UU + Tupil ... and more ...

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Re: Hi-res/vector version of logo?
by Brian Sniffen 11 Apr '09

11 Apr '09

> Sure, I'm happy to convert the PSDs (available in the src/ directory, > here [1]) into SVG, but I will have to do so through tracing them in > InkScape unless somebody has another solution. Many of those are on one basic template. I have no expertise to advice on the choice of greys, but I do like MetaPost. I have created a basic metapost encoding of your logo7, and placed it at <http://evenmere.org/~bts/haskell-logo/>. I'm not entirely thrilled with its use of explicit constants to end the equal sign or place the groin of the lambda, but this'll do for a first draft. A PDF generated from that MetaPost file is there as logo-0.pdf for easy evaluation. I experimented with the PDF-to-SVG converter at <http://www.tlhiv.org/MetaPost/tools/mptosvg/>, but do not expect anyone to be thrilled with the results who must edit them. I also experimented with potrace. The results will are wiggly. They may be inspected at .../potrace/. -Brian -- Brian T. Sniffen bts(a)alum.mit.edu or brian.sniffen(a)gmail.com http://www.evenmere.org/~bts

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Ann: Yogurt-0.4
by Martijn van Steenbergen 10 Apr '09

10 Apr '09

Bonsoir café, It is my pleasure to announce version 0.4 of Yogurt, a functional MUD client. Version 0.4 makes Yogurt available as a standalone executable that is able to dynamically load and reload Yogurt scripts. Here is a small example of such a script: > module Minimal where > > import Network.Yogurt > > newmoon :: Session > newmoon = session > { hostName = "eclipse.cs.pdx.edu" > , portNumber = 7680 > , mudProgram = \reload -> do > mkCommand "reload" reload > } Valid scripts define at least one session which is used to connect to the MUD. mudProgram fields are provided with a reload action that when invoked reloads the script without interrupting the MUD connection. Of course, Yogurt also still offers hooks, timers, logging, variables and more. The executable is released as a separate package so that developers wishing to use just the "pure" machinery can do that without inheriting dependencies on the GHC API or readline library. To install the executable, run: $ cabal update $ cabal install Yogurt -freadline $ cabal install Yogurt-Standalone Yogurt's new home page can be found at: http://code.google.com/p/yogurt-mud/ And on hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Yogurt http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Yogurt-Standalone I would love to hear your feedback! Suggestions, complaints, comments, bug reports, experiences et cetera are all welcome. Kind regards, Martijn.

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CFP Haskell Symposium 2009
by Stephanie Weirich 10 Apr '09

10 Apr '09

Reminder: there are only 4 weeks until the submission deadline for the 2009 Haskell Symposium. Please do submit. Hope to see you in Edinburgh! Stephanie --------------------------------------------------------------- Haskell 09 ACM SIGPLAN Haskell Symposium 2009 Edinburgh, Scotland, UK September 3, 2009 CALL FOR PAPERS http://haskell.org/haskell-symposium/2009/ The ACM SIGPLAN Haskell Symposium 2009 will be co-located with the 2009 International Conference on Functional Programming (ICFP). The purpose of the Haskell Symposium is to discuss experiences with Haskell and future developments for the language. The scope of the symposium includes all aspects of the design, semantics, theory, application, implementation, and teaching of Haskell. Topics of interest include, but are not limited to, the following: * Language Design, with a focus on possible extensions and modifications of Haskell as well as critical discussions of the status quo; * Theory, in the form of a formal treatment of the semantics of the present language or future extensions, type systems, and foundations for program analysis and transformation; * Implementations, including program analysis and transformation, static and dynamic compilation for sequential, parallel, and distributed architectures, memory management as well as foreign function and component interfaces; * Tools, in the form of profilers, tracers, debuggers, pre-processors, and so forth; * Applications, Practice, and Experience, with Haskell for scientific and symbolic computing, database, multimedia and Web applications, and so forth as well as general experience with Haskell in education and industry; * Functional Pearls, being elegant, instructive examples of using Haskell. Papers in the latter two categories need not necessarily report original research results; they may instead, for example, report practical experience that will be useful to others, re-usable programming idioms, or elegant new ways of approaching a problem. The key criterion for such a paper is that it makes a contribution from which other Haskellers can benefit. It is not enough simply to describe a program! Before 2008, the Haskell Symposium was known as the Haskell Workshop. The name change reflects both the steady increase of influence of the Haskell Workshop on the wider community as well as the increasing number of high quality submissions. The acceptance process is highly competitive. After eleven Haskell Workshops between 1995 and 2007, the first Haskell Symposium was held in Victoria in 2008. Submission Details * Submission Deadline: Friday, May 8th 2009 (3:00 pm, Eastern US Time) * Author Notification: Monday, June 1st 2009 * Final Papers Due : Monday, June 15th 2009 Submitted papers should be in portable document format (PDF), formatted using the ACM SIGPLAN style guidelines (http://www.acm.org/sigs/sigplan/authorInformation.htm) The length is restricted to 12 pages, and the font size 9pt. Each submission must adhere to SIGPLAN's republication policy, as explained on the web. Violation risks summary rejection of the offending submission. Accepted papers will be published by the ACM and will appear in the ACM Digital Library. If there is sufficient demand, we will try to organize a time slot for system or tool demonstrations. If you are interested in demonstrating a Haskell related tool or application, please send a brief demo proposal to Stephanie Weirich, sweirich(a)cis.upenn.edu. Links * http://haskell.org/haskell-symposium, the permanent homepage of the Haskell Symposium. * http://haskell.org/haskell-symposium/2009/, the 2009 Haskell Symposium web page. * http://www.icfpconference.org/icfp2009, the ICFP 2009 web page. Program Committee * Jeremy Gibbons, Oxford University * Bastiaan Heeren, Open Universiteit Nederland * John Hughes, Chalmers/Quviq * Mark Jones, Portland State University * Simon Marlow, Microsoft Research * Ulf Norell, Chalmers * Chris Okasaki, United States Military Academy * Ross Paterson, City University London * Alexey Rodriguez Yakushev, Vector Fabrics * Don Stewart, Galois * Janis Voigtlaender, TU Dresden * Stephanie Weirich, University of Pennsylvania (Chair)

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Re: Hi-res/vector version of logo?
by Jeff Wheeler 08 Apr '09

08 Apr '09

On Wed, 2009-04-08 at 23:48 +0200, Eelco Lempsink wrote: > Could you email / upload to the wiki / put online a vector or hi-res > version of the logo(s) you made? That will make it easier for people > to actually use the logo or make derivates from it. (Preferably in an > Open format, such as SVG, if Photoshop can do that.) I'm not a > licensing guru, but it probably be nice if you make the logo available > under some free license or at least put a message there that you allow > such usage ;) (I've CC'd haskell@, as I feel this discussion might be useful there.) Sure, I'm happy to convert the PSDs (available in the src/ directory, here [1]) into SVG, but I will have to do so through tracing them in InkScape unless somebody has another solution. Rather than converting every one of these (it takes some time to get it right), it'd be easier for me to only convert the ones the community decides to use. Will further voting happen on these soon? If you're looking for one right now, please reply and I'll try to take care of that one. Also, I claim no copyright on these in any form. I am presently placing all these images in the Public Domain, and I suspect Darrin feels the same way for the concept. Jeff Wheeler [1] http://media.nokrev.com/junk/haskell-logos/

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Local Haskell meeting, Halle/Saale, Germany, June 12
by Janis Voigtlaender 08 Apr '09

08 Apr '09

[Apologies for German announcement text...] --------------------------------------------- HaL4 : Haskell - Tutorial + Workshop + Party am Freitag, dem 12. Juni 2009, in Halle/Saale --------------------------------------------- Das traditionsreiche HaL-Treffen bietet eine gute Mischung von Haskell-bezogenen Themen aus Forschung, Anwendung und Lehre mit vielen Möglichkeiten zu Diskussion und Unterhaltung bei der anschließenden Party. Der Workshop wird in diesem Jahr ergänzt durch Tutorien für Haskell-Ein- und Umsteiger. Diesmal findet das Treffen in Halle/Saale im Institut für Informatik der Martin-Luther-Universität Halle-Wittenberg statt. Wir planen: 10 - 13 Uhr: Tutorien 15 - 19 Uhr: Fachvorträge 19 - 22 Uhr: Grillparty Wir freuen uns auf rege Teilnahme sowie spannende Vorträge mit heißen Diskussionen und bitten um Vortragsanmeldungen bis zum 8. Mai. Gedacht sind 4 mal je 30 min Vortrag + 30 min Diskussion. Weitere Informationen auf http://www.iba-cg.de/hal4.html -- Dr. Janis Voigtlaender http://wwwtcs.inf.tu-dresden.de/~voigt/ mailto:voigt@tcs.inf.tu-dresden.de

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CFP: JFP Special Issue on Generic Programming
by Matthew Fluet (ICFP Publicity Chair) 07 Apr '09

07 Apr '09

OPEN CALL FOR PAPERS JFP Special Issue on Generic Programming Deadline: 1 October 2009 http://www.comlab.ox.ac.uk/ralf.hinze/JFP/cfp.html Scope ----- Generic programming is about making programs more adaptable by making them more general. Generic programs often embody non-traditional kinds of polymorphism; ordinary programs are obtained from them by suitably instantiating their parameters. In contrast to normal programs, the parameters of a generic program are often quite rich in structure; for example they may be other programs, types or type constructors, classes, concepts, or even programming paradigms. This special issue aims at documenting state-of-the-art research, new developments and directions for future investigation in the broad field of Generic Programming. It is an outgrowth of the series of Workshops on Generic Programming, which started in 1998 and which continues this year with an ICFP affiliated workshop in Edinburgh. Participants of the workshops are invited to submit a suitably revised and expanded version of their paper to the special issue. The call for papers is, however, open. Other contributions are equally welcome and are, indeed, encouraged. All submitted papers will be subjected to the same quality criteria, meeting the standards of the Journal of Functional Programming. The special issue seeks original contributions on all aspects of generic programming including but not limited to o adaptive object-oriented programming, o aspect-oriented programming, o case studies, o concepts (as in the STL/C++ sense), o component-based programming, o datatype-generic programming, o generic programming with dependent types, o meta-programming, o polytypic programming, and o programming with modules. Submission details ------------------ Manuscripts should be unpublished works and not submitted elsewhere. Revised versions of papers published in conference or workshop proceedings that have not appeared in archival journals are eligible for submission. Deadline for submission: 1 October 2009 Notification of acceptance or rejection: 15 January 2010 Revised version due: 15 March 2010 For submission details, please consult http://www.comlab.ox.ac.uk/ralf.hinze/JFP/cfp.html or see the Journal's web page http://journals.cambridge.org/jfp Guest Editor ------------ Ralf Hinze University of Oxford Computing Laboratory Wolfson Building, Parks Road, Oxford OX1 3QD, UK. Telephone: +44 (1865) 610700 Fax: +44 (1865) 283531 Email: ralf.hinze(a)comlab.ox.ac.uk WWW: http://www.comlab.ox.ac.uk/ralf.hinze/ -------------------------------------------------------------------------------

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