August 2010 - Haskell

ANNOUNCE: iteratee-0.3.6, iteratee-0.4.0.1
by John Lato 25 Aug '10

25 Aug '10

Hello, I am very pleased to announce the release of iteratee-0.4.0.1. This release features several breaking changes from prior versions, including a new low-level implementation. Type names have been changed to bring them closer in line to Oleg's publications, the iteratee type has been simplified and requires fewer type variables, WrappedByteString is no longer necessary or provided, and many of the special combinators such as ($$) are no longer required. Another very powerful feature is a user-extensible mechanism for iteratees to alter enumerator behavior, enabled by the new exception mechanism and the callback-based enumerator interface. A simple example of this feature is the provided "seek" implementation. Other improvements include re-written documentation and new example files in the Examples folder (available after unpacking the hackage distribution). There is also a new tutorial in the Examples folder provided by Ben Lee, which details the new CPS-based implementation. If you've tried iteratee before but had trouble understanding it, please consider having another look. I have also released the package "iteratee-mtl", which is identical to the main package except it is based upon mtl. Due to the type name changes, iteratee-0.4 is incompatible with prior releases. Updating code to this release can be as simple as changing types/imports, although in many cases the conversion will be more involved. For those users who are unable to update to this release, I am also pleased to announce Iteratee-0.3.6, the final release of the 0.3.x line. It has been somewhat cleaned up and features several powerful new functions contributed by Conrad Parker and Brian Lewis, including "ioIter", "mapM_", and "enumFdFollow". These functions will be migrated to the 0.4 line in due course. I am most grateful to many people who contributed to this release. Thanks especially to Conrad Parker, Antoine Latter, Ben Lee, Paulo Tanimoto, and Edward Yang for many significant improvements. Thank you, John Lato

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[Haskell] ANNOUNCE: Sifflet visual programming language, release 1.1
by gdweber＠iue.edu 24 Aug '10

24 Aug '10

Sifflet-lib 1.1 and sifflet 1.1 are now available on Hackage. Sifflet is a visual, functional programming language and support system for students learning about recursion. Sifflet programmers define functions by drawing diagrams, and the Sifflet interpreter uses diagrams to show how the function calls are evaluated. Sifflet-lib is the library containing many modules of the sifflet application. New in This Release ------------------- - Relaxed versioned dependencies on cairo, gtk, glib (== 0.11.* instead of == 0.11.0) should make it possible to build with slightly newer versions of these libraries (and pango). - Sifflet export to Haskell now removes most unnecessary parentheses. - The module Sifflet.Data.Number is now Data.Number.Sifflet. - Many undocumented API changes in sifflet-lib. (I really hope nobody is using this library for development but me! But if you are, contact me, and I'll send a partial list of the changes.) About Sifflet ------------- Sifflet is a visual, functional programming language intended as an aid for learning about recursion. * A picture explains Sifflet better than words: please see the screenshot showing how to evaluate 3!: http://mypage.iu.edu/~gdweber/software/sifflet/home.html * Features: - Visual editor. - Visual tracer/debugger which shows how recursive and other function calls are evaluated. To support active learning and avoid screen clutter, Sifflet displays only as much of the computation as the user requests. - A carefully crafted tutorial with 31 pictures and about as many pages. - Number, string, and list data types. - A small collection of primitive functions. - Runnable examples of compound functions. - Sifflet functions can be "exported" to Scheme, Python 3, and Haskell. * Download: http://hackage.haskell.org/package/sifflet-lib http://hackage.haskell.org/package/sifflet * Home page: http://mypage.iu.edu/~gdweber/software/sifflet/home.html * Tutorial: http://mypage.iu.edu/~gdweber/software/sifflet/doc/tutorial.html -- ___ ___ __ _ / _ \ / _ \| | | | Gregory D. Weber, Associate Professor / /_\// / | | | /\ | | Indiana University East / /_\\/ /__| | |/ \| | http://mypage.iu.edu/~gdweber/ \____/\_____/\___/\__/ Tel. (765) 973-8420; FAX (765) 973-8550

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arrow syntax with LaTeX
by Lambdor 24 Aug '10

24 Aug '10

\leftY from "MnSymbol" package has the same thickness as \leftarrow, but compared to \leftarrowtail it isn't curled

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Second Call for Copy: Monad.Reader Issue 17
by Brent Yorgey 23 Aug '10

23 Aug '10

Whether you're an established academic or have only just started learning Haskell, if you have something to say, please consider writing an article for The Monad.Reader! The submission deadline for Issue 17 is **Friday, October 1, 2010** That's little more than a month away! Get started on your article now! =) The Monad.Reader ~~~~~~~~~~~~~~~~ The Monad.Reader is a electronic magazine about all things Haskell. It is less formal than journal, but somehow more enduring than a wiki- page. There have been a wide variety of articles: exciting code fragments, intriguing puzzles, book reviews, tutorials, and even half-baked research ideas. Submission Details ~~~~~~~~~~~~~~~~~~ Get in touch with me if you intend to submit something -- the sooner you let me know what you're up to, the better. Please submit articles for the next issue to me by e-mail (byorgey at cis.upenn.edu) Articles should be written according to the guidelines available from http://themonadreader.wordpress.com/contributing/ Please submit your article in PDF, together with any source files you used. The sources will be released together with the magazine under a BSD license. If you would like to submit an article, but have trouble with LaTeX please let me know and we'll work something out.

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ICFP '10: Final call for participation
by Wouter Swierstra 23 Aug '10

23 Aug '10

===================================================================== Final Call for Participation The 15th ACM SIGPLAN International Conference on Functional Programming (ICFP 2010) http://www.icfpconference.org/icfp2010/ Baltimore, Maryland September 25 – October 2 ===================================================================== ICFP 2010 provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. The conference covers the entire spectrum of work, from practice to theory, including its peripheries. ** Not that the early registration deadline and discount hotel rates expire next week. ** * Program: http://www.icfpconference.org/icfp2010/program.html * Invited speakers: - Mike Gordon ML: Metalanguage or Object Language? - Matthias Felleisen TeachScheme!: A Checkpoint - Guy Blelloch Functional Parallel Algorithms Schedule including related events: * September 25: Workshop on Mechanizing Metatheory (WMM) Workshop on Mathematically Structured Functional Programming (MSFP) Workshop on High-Level Parallel Programming and Applications (HLPP) * September 26: Workshop on ML Workshop on Generic Programming (WGP) * September 27-29: ICFP 2010 * September 30: Haskell Symposium Erlang Workshop * October 1: Commercial Users of Functional Programming – Day 1 (CUFP Tutorials) Haskell Implementors' Workshop * October 2: Commercial Users of Functional Programming – Day 2 (CUFP Talks) This year there will also be a special series of Birds-of-a-Feather sessions associated with CUFP. More information can be found at: http://cufp.org/bofs-2010 Registration information: * Registration link: https://regmaster3.com/2010conf/ICFP10/register.php Local arrangements (including travel and accommodation): * http://www.icfpconference.org/icfp2010/local.html * Conference reservation/rate deadline: September 1st Conference organizers: * General Chair: Paul Hudak, Yale University * Program Chair: Stephanie Weirich, University of Pennsylvania * Local Arrangements Chair: Michael Hicks, University of Maryland * Workshop Co-Chairs: Derek Dreyer, Max Planck Institute for Software Systems Christopher Stone, Harvey Mudd College * Programming Contest Chair: Johannes Waldmann, Hochschule für Technik, Wirtschaft und Kultur, Leipzig * Video Chair: Scott Smith, Johns Hopkins University * Publicity Chair: Wouter Swierstra, Vector Fabrics =====================================================================

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ANNOUNCE: enumerator, an alternative iteratee package
by John Millikin 21 Aug '10

21 Aug '10

Most of you have probably read Oleg's essays on using left-fold enumerators for incremental IO. In short, by encapsulating monadic left-folds in an "Iteratee" type, incremental pure processing is possible without using lazy IO. Sources to read: Oleg: Streams and Iteratees < http://okmij.org/ftp/Streams.html > Magnus Therning: Trying to work out iteratees < http://therning.org/magnus/archives/735 > cdsmith: Iteratees Step By Step (Part 1) < http://cdsmith.wordpress.com/2010/05/23/iteratees-step-by-step-part-1/ > John Millikin (me): Understanding Iteratees < http://ianen.org/articles/understanding-iteratees/ > Currently, the primary package for left-fold enumerators is John Lato's "iteratee". It is based on Oleg's original code, extended to support various forms of containers, platform-specific IO, and codecs for the WAV and TIFF formats. While I appreciate Mr. Lato's development of the package, I find it far too large, and its documentation too sparse, to effectively use. To correct this, I've written the "enumerator" package. It is also derived from Oleg's IterateeM.hs , but with a simplified API and significantly reduced dependency list. Hackage entry: http://hackage.haskell.org/package/enumerator Haddock docs: http://ianen.org/haskell/enumerator/api-docs/ Source code (literate PDF): http://ianen.org/haskell/enumerator/enumerator.pdf darcs get http://ianen.org/haskell/enumerator/ Additionally, I've included examples of using enumerators to implement simplified versions of the "cat" and "wc" utilities. These should serve as a useful starting point for anybody who wants to use enumerators in their own code: http://patch-tag.com/r/jmillikin/enumerator/snapshot/current/content/pretty… http://patch-tag.com/r/jmillikin/enumerator/snapshot/current/content/pretty… There are already a few libraries using the existing "iteratee" package (snap, attoparsec-iteratee, hexpat-iteratee); I am very interested in advice from the authors of these libraries. In particular, are any of the removed features (ListLike, WrappedByteString, seeking) something your libraries depend on? Are there any useful combinators you'd like to see included?

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Programming language opening at Oxford
by Simon Peyton-Jones 16 Aug '10

16 Aug '10

Oxford is advertising a tenure-track faculty position in programming languages: http://www.comlab.ox.ac.uk/news/231-full.html This is the same type of position as, say, Oege de Moor holds, so I can guarantee it's a nice job! Simon

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Programming Languages opening at Oxford
by Oege.de.Moor＠comlab.ox.ac.uk 16 Aug '10

16 Aug '10

FACULTY POSITION IN PROGRAMMING LANGUAGES AT OXFORD The University of Oxford is offering a tenure-track faculty position in the area of programming languages. Full details can be found at: http://www.comlab.ox.ac.uk/news/231-full.html The closing date for applications is September 24.

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Fwd: [Haskell-cafe] Question about memory usage
by Alberto G. Corona 16 Aug '10

16 Aug '10

It is not repeated because fiblist is pure and has no arguments. Otherwise it would be repeated. 2010/8/14 Tako Schotanus <tako(a)codejive.org> > I was reading this article: > > http://scienceblogs.com/goodmath/2009/11/writing_basic_functions_in_has.php > > And came to the part where it shows: > > > > fiblist = 0 : 1 : (zipWith (+) fiblist (tail fiblist)) > > > Very interesting stuff for somebody who comes from an imperative world of > course. > But then I read that "Once it's been referenced, then the list up to where > you looked is concrete - the computations *won't* be repeated." > and I started wondering how that works. > Because this seems to mean that functions could have unknown (to the > caller) memory requirements. > How does one, programming in Haskell, keep that in check? > And when does that memory get reclaimed? > > Cheers, > -Tako > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe > >

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Gtk2Hs 0.11.1 released
by Axel Simon 14 Aug '10

14 Aug '10

Dear all, after a few months of shaking out bugs, we've released a new patch- level version of Gtk2Hs, the binding to the Gtk+ GUI library suite. Notable changes: - several bug fixes with respect to concurrency on a variety of platforms - linking problems in ghci have been resolved - pango now includes functions to draw text on Cairo surfaces; this makes it possible to render Unicode text into PDF/PS/SVG/PNG documents without the need for the GUI part in the gtk package - we included the demos in the tar balls (we forgot that last time...) - other bug fixes Please see our web-site http://www.haskell.org/gtk2hs/ for further information and read http://code.haskell.org/gtk2hs/INSTALL if you plan to give it a go! Cheers, Axel

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