- Haskell - Haskell.org

Waiting on multiple Chan-nels
by Setzer, Sebastian (ext) 12 Dec '06

12 Dec '06

Hi, How do you wait on multiple channels, but read only from one of them (the first that gets an entry)? Is there a library-function I missed which already does this? What do you think of this solution? Sebastian Setzer -------------------------------------------------------------- -- ghc chantest.hs -o chantest -- Usage: Enter "1", "2" or "0" to exit. import System.IO import Control.Concurrent import Control.Concurrent.Chan main :: IO() main = do chan1 <- newChan chan2 <- newChan c1Thread <- forkIO (printChan "c1" chan1) c2Thread <- forkIO (printChan "c2" chan2) c12Thread <- forkIO (printChannels "c12" [chan1, chan2]) mainloop chan1 chan2 mainloop :: Chan String -> Chan String -> IO () mainloop chan1 chan2 = do c <- getChar command c where -- chan1 and chan2 are in scope, here. go_on :: IO() go_on = mainloop chan1 chan2 command :: Char -> IO() command '0' = do print "done" command '1' = do writeChan chan1 "main: 1" go_on command '2' = do writeChan chan2 "main: 2" go_on command '\n' = do -- ignore go_on command c = do print ("illegal: " ++ [c]) go_on -- return microseconds seconds :: Int -> Int seconds = (* 1000000) printChan :: String -> (Chan String) -> IO() printChan name chan = do -- threadDelay (seconds 3) -- print (name ++ " ready") s <- readChan chan printString name s printChan name chan printChannels :: String -> [Chan String] -> IO() printChannels name channels = do -- select (zip channels (repeat (printString name))) select $ zip channels $ repeat $ printString name printChannels name channels printString :: String -> String -> IO () printString name s = print (name ++ ": " ++ s) select :: [(Chan a, a -> IO())] -> IO () select channel_handler_pairs = do threadDelay (seconds 3) print "TODO: implement select" {- TODO: implement select. - create MVar - For each element of the channel_handler_pairs - list, fork a thread. - wait on an MVar for the signal "I'm done" - kill all helper threads (just to free the resources. They wouldn't do any harm) In the helper-threads: - readChan - try to signal "I'm ready" on the MVar. If another thread was faster, unGetChan and exit - call the handler - signal "I'm done" and exit Problems: - If the Thread gets killed between readChan and unGetChan, the message is lost. - if another thread reads between readChan and unGetChan, its no fifo anymore (unlikely, because why would you want to read with multiple threads on the same Chan? - You'd use dupChan for that purpose. Unless you want every "event" to be handled only once. But then you would'nt use multiple threads, would you?) - "a" must be the same for every channel-handler-pair Thats easy: instead of channel-handler-tuples, put functions MVar -> IO() into the list and provide a nice-looking operator to create them - Probably inefficient (lots of helper threads) -}

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Reading from two fifos
by Setzer, Sebastian (ext) 12 Dec '06

12 Dec '06

Hi, Why doesn't this program start reading from one fifo until the second fifo gets opened (with cat), too? (It doesn't matter which fifo is opened first.) Why doesn't it print "forked" before "fifo1" is opened? After both fifos are open, it works as expected. I have ghc 6.6-3 on debian-linux (testing) Sebastian Setzer ------------------------------------------------------------------ -- Compile: ghc twofifo.hs -o twofifo -threaded -package unix-1.0 -- Usage: -- mkfifo fifo1 -- mkfifo fifo1 -- ./twofifo -- in two separate xterms: -- cat > fifo1 -- ... -- cat > fifo2 -- ... import System.IO import System.Posix.IO import System.Posix.Types import Control.Concurrent main :: IO() main = do f1Thread <- forkOS (openAndShowFile "fifo1") print "forked" hFlush stdout openAndShowFile "fifo2" openAndShowFile :: String -> IO() openAndShowFile name = do fd <- openFd name ReadOnly Nothing defaultFileFlags showFile name fd showFile :: String -> Fd -> IO() showFile name fd = do threadWaitRead fd (s, count) <- fdRead fd 1024 print (name ++ ": " ++ s) hFlush stdout showFile name fd

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The Monad.Reader call for copy
by Wouter Swierstra 12 Dec '06

12 Dec '06

It's still not too late to write something for the next issue of The Monad.Reader! We have a nice issue slowly shaping up, but your contribution is still very welcome. * The Monad.Reader * There are a large number of conferences and journals that accept research papers related to Haskell; unfortunately, the platform for non-academic publications is far less developed. This is where The Monad.Reader fits in. I believe that there are lots of people on these mailing lists that have plenty of ideas that might not be suitable for the the Haskell Workshop, for instance, but are nonetheless worth writing about. Sometimes such ideas end up as posts on a Haskell mailing list; sometimes they get posted on personal blogs; sometimes they disappear altogether. A lot of e-mails to these mailing lists deserve a more lasting place. * 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 by e-mail (wss at cs.nott.ac.uk) to me before **January 19th, 2007** . Articles should be written according to the guidelines available from http://www.haskell.org/haskellwiki/TheMonadReader Please submit your article PDF format. If you would like to submit an article, but have trouble with LaTeX please let me know and we'll sort something out. After a bit of deliberation, I decided it may be best to ask authors to make their source .tex source files available under a BSD license. This seems to "play nice" with other licenses; the originally proposed Creative Commons license caused some trouble. All the best, Wouter This message has been checked for viruses but the contents of an attachment may still contain software viruses, which could damage your computer system: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation.

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Haskell Weekly News: December 12, 2006
by dons＠cse.unsw.edu.au 11 Dec '06

11 Dec '06

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/ Issue 53 - December 12, 2006 --------------------------------------------------------------------------- Welcome to issue 53 of HWN, a weekly newsletter covering developments in the Haskell community. Lots of new, practical Haskell libraries released this week, including support for ogg sound file parsing, a new user interface library, ftp clients and servers, database bindings as well as config files and logging. Announcements Visual Haskell 0.2. Krasimir Angelov [1]announced the final version of [2]Visual Haskell 0.2 is available! This is the first version that is: available for both VStudio 2003 and VStudio 2005; distributed with a stable GHC version (6.6). Additionally the plugin itself is much more stable than its first 0.0 version. 1. http://article.gmane.org/gmane.comp.lang.haskell.general/14608 2. http://www.haskell.org/visualhaskell Phooey: functional user interfaces for Haskell. Conal Elliott [3]announced Phooey, [4]a functional UI library for Haskell. GUIs are usually programmed in an 'unnatural' style, in that implementation dependencies are inverted, relative to logical dependencies. This reversal results directly from the imperative orientation of most GUI libraries. While outputs depend on inputs from a user and semantic point of view, the imperative approach imposes an implementation dependence of inputs on outputs. Phooey ('Phunctional ooser ynterfaces') retains the functional style, in which outputs are expressed in terms of inputs. In addition, Phooey supports dynamic input bounds, flexible layout, and mutually-referential widgets. It is [5]available via darcs. 3. http://article.gmane.org/gmane.comp.lang.haskell.general/14635 4. http://darcs.haskell.org/packages/phooey/doc 5. http://darcs.haskell.org/packages/phooey HOgg 0.2.0. Conrad Parker [6]announced HOgg 0.2.0. The [7]HOgg package provides a commandline tool for manipulating Ogg files, and a corresponding Haskell library. This is the initial public release. The focus is on correctness of Ogg parsing and production. The capabilities of the hogg commandline tool are roughly on par with those of the [8]oggz* tools, although hogg does not yet provide an equivalent to oggz-validate. HOgg supports chained and multiplexed Ogg bitstreams conformant with [9]RFC3533. HOgg can parse headers for CMML, FLAC, OggPCM, Speex, Theora and Vorbis media codecs, and can read and write Ogg Skeleton bitstreams. 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17102 7. http://snapper.kfish.org/~conrad/software/hogg/ 8. http://www.annodex.net/software/liboggz/index.html 9. http://www.ietf.org/rfc/rfc3533.txt 10. http://article.gmane.org/gmane.comp.lang.haskell.general/14610 ftphs. John Goerzen [10]announced ftphs, [11]an FTP client and server library for Haskell. Its features include: easy to use operation; full support of text and binary transfers; optional lazy interaction; server can serve up a real or a virtual filesystem tree; Standards compliant. ftphs was previously a part of the MissingH library. The code in this release is unchanged from its state in MissingH, other than the changes necessary to make it a standalone package. 11. http://software.complete.org/ftphs AnyDBM 1.0.0. John Goerzen [12]announced AnyDBM, a generic DBM-type interface. [13]AnyDBM provides a generic infrastructure for supporting storage of hash-like items with String-to-String mappings. It can be used for in-memory or on-disk storage. Two simple backend drivers are included with this package: one that is RAM-only, and one that is persistent and disk-backed. The hdbc-anydbm package provides another driver, which lets you use simple tables in any SQL database to provide a DBM-like interface. MissingPy also provides a Python driver which lets you use any Python anydbm driver under Haskell AnyDBM. 12. http://article.gmane.org/gmane.comp.lang.haskell.general/14613 13. http://software.complete.org/anydbm ConfigFile 1.0.0. John Goerzen [14]announced ConfigFile, a parser and writer for handling sectioned config files in Haskell. The [15]ConfigFile module works with configuration files in a standard format that is easy for the user to edit, easy for the programmer to work with, yet remains powerful and flexible. It is inspired by, and compatible with, Python's ConfigParser module. It uses files that resemble Windows .INI-style files, but with numerous improvements. 14. http://article.gmane.org/gmane.comp.lang.haskell.general/14612 15. http://software.complete.org/configfile hslogger. John Goerzen [16]announced hslogger, a logging framework for Haskell. [17]hslogger's features include: each log message has a priority and a source associated with it; multiple log writers can be on the system; configurable global actions based on priority and source; extensible log writers (handlers); default handlers that write to the console, file handles, or syslog; easy to use operation. hslogger is the first package to be split off from the MissingH source. 16. http://article.gmane.org/gmane.comp.lang.haskell.general/14611 17. http://software.complete.org/hslogger MissingH 0.18.0. John Goerzen [18]announced MissingH 0.18.0. [19]MissingH is a large collection of assorted utility libraries for Haskell. Its primary audience is Haskell programmers that want to get practical things done fast. This release implements the first part of the MissingH transition. The major changes are: most code from other sources that had been merged into MissingH has been split off; stable, mostly standalone components of MissingH have been split off: hslogger, ftphs, ConfigFile, AnyDBM, and all modules renamed to more closely follow current Haskell naming practices. 18. http://article.gmane.org/gmane.comp.lang.haskell.general/14614 19. http://software.complete.org/missingh ZMachine 0.0. Samuel Bronson [20]announced a (partial) Z-machine interpreter in Haskell. It uses gtk2hs for the interface, though other interfaces could be implemented without actually changing the interpreter proper. The Z-machine is a virtual machine that was developed by Joel Berez and Marc Blank in 1979 and used by Infocom for its text adventure games. 20. http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/11397 Halp: Haskell Logic Prover. Dan Mead [21]announced the release of Halp, the simple logic prover. Right now it only supports simple first order logic but predicates are on the way. Theres also a simple gui written in Java 5 which is in the [22]darcs repository. 21. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17104/ 22. http://taz.cs.wcupa.edu/~dmead/code/halp/ DList 0.1. Don Stewart [23]announced dlist 0.1, a library for difference lists in Haskell. Difference lists are a Haskell idiom for implementing O(1) append on lists, using functions to represent the lists. 23. http://article.gmane.org/gmane.comp.lang.haskell.general/14623 Haskell' This section covers the [24]Haskell' standardisation process. * [25]Infix multiparameter type classes * [26]Type sections * [27]Are pattern guards obsolete? 24. http://hackage.haskell.org/trac/haskell-prime 25. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1948/focus=1948 26. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1955/focus=1955 27. http://thread.gmane.org/gmane.comp.lang.haskell.prime/1956/focus=1956 Discussion Ninety Nine Haskell Problems. Andrew Wagner [28]mentioned that 99 Lisp exercises have been [29]ported to Haskell. Solving these exercises is a great way for relatively new haskell programmers to contribute something, since most of the problems are relatively simple. So have at them! All you need to do is write a canonical Haskell solution, and add it to the wiki. Please follow the instructions for 'reserving' a problem so we're not all duplicating each others' work. We should be able to knock these problems out in a matter of hours! 28. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17324 29. http://haskell.org/haskellwiki/99_Haskell_exercises MissingH status. John Goerzen [30]announced that MissingH now has [31]a new Trac-based homepage, complete with wiki, Darcs repository information, source browser, bug tracker, and the various pieces of MissingH have been split off already into separate packages. The full list of changes is [32]available. 30. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17156 31. http://software.complete.org/missingh 32. http://software.complete.org/missingh/wiki/TransitionPlanning Reversing a string of words: C# v Perl v Ruby v Haskell. Andrew Savige [33]invoked the Haskell cafe magicians with a comparison of string processing support across languages. 33. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17197/focus=17197 Unlifted type variables in GHC. Brian Alliet [34]asked about the intricacies of supporting type variables with an unlifted kind. 34. http://thread.gmane.org/gmane.comp.lang.haskell.glasgow.user/11397/focus=11… Wanted: libraries. Don Stewart [35]asked for information about missing or substandard libraries to be documented on the wiki. 35. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17222/focus=17222 Haskell for Dummies. Kirsten Chevalier [36]launched an interesting discussion to produce a new 'Practical Haskell' or 'Haskell for Dummies' textbook. 36. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17240/focus=17240 Stratified monads. Mark Carroll [37]asked about experience with Espinosa's stratified monads in Haskell. 37. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/17266/focus=17266 Conference roundup hal: Haskell in Leipzig. [38]More than 25 Haskellers from all over Germany gathered in Leipzig for the first HaL, Haskell in Leipzig, meeting. The range of different backgrounds was broad and spanned both the academic and the business worlds, encompassing seasoned Haskell programmers as well as beginners. There were five talks and two discussion sessions, and a functional breakfast. One of the discussion sessions had IDE support (in particular, in Eclipse) as its topic, the other focused on the possibilities for promoting Haskell in the software industry. The talk topics ranged from the use of Haskell in web technology and in climate research, to specifics of programming (MonadFix, coding guidelines). A very Haskell-like language (CAL Quark) that offers access to Java libraries and can be compiled to JVM bytecode was also introduced. A second 'Haskell in Leipzig' meeting is planned for early spring 2007. [39]Summaries of the talks are available. 38. http://iba-cg.de/haskell.html 39. http://iba-cg.de/haskell.html The Haskell Hackathon. The Hac organisers [40]announced that extended registration for Hac 07, the Haskell libraries and infrastructure hackathon is open, via the [41]Hac website. 40. http://article.gmane.org/gmane.comp.lang.haskell.cafe/17132 41. http://haskell.org/haskellwiki/Hac_20007 Blog noise [42]Haskell news from the blogosphere. * [43]A Tree Grows Up in Haskell: Building a Dictionary Type * [44]Functional programming is a silver bullet * [45]Silver Bullets Incoming! * [46]The Division Bell Tolls for Me, Part One * [47]The Division Bell Tolls for Me, Part Two * [48]The Division Bell Tolls for Me, Part Three * [49]The Division Bell Tolls for Me, Part Four (Conclusion) * [50]The Divisive Aftermath * [51]Non-standard analysis, automatic differentiation, Haskell, and other stories * [52]Adventures in Haskell: parsing the game world * [53]Generalised Haskell * [54]Haskell tool tips * [55]Reconsidering my approach to learning Haskell * [56]A Sermon on Programming Languages * [57]Polyglot Programming * [58]Fibonacci series one-liner in Haskell * [59]An infinite list in Java * [60]The beauty of Haskell * [61]On Unit Testing and Type Safety * [62]Rewriting PLEAC Haskell? * [63]A newbie in Haskell land : The (->) monad * [64]Quick interpreters with the Reader monad * [65]bhc: Basic Haskell Compiler * [66]The lambda revolution: how you can help 42. http://planet.haskell.org/ 43. http://scienceblogs.com/goodmath/2006/12/a_tree_grows_up_in_haskell_bui_1.p… 44. http://cogito.blogthing.com/2006/12/06/no-silver-bullet-and-functional-prog… 45. http://cogito.blogthing.com/2006/12/08/silverbulletsincoming/ 46. http://praisecurseandrecurse.blogspot.com/2006/12/division-bell-tolls-for-m… 47. http://praisecurseandrecurse.blogspot.com/2006/12/division-bell-tolls-for-m… 48. http://praisecurseandrecurse.blogspot.com/2006/12/division-bell-tolls-for-m… 49. http://praisecurseandrecurse.blogspot.com/2006/12/division-bell-tolls-for-m… 50. http://praisecurseandrecurse.blogspot.com/2006/12/divisive-aftermath.html 51. http://vandreev.wordpress.com/2006/12/04/non-standard-analysis-and-automati… 52. http://jpmoresmau.blogspot.com/2006/12/adventures-in-haskell-parsing-game.h… 53. http://neilmitchell.blogspot.com/2006/12/generalised-haskell.html 54. http://monad.carnalreason.org/wordpress/?p=21 55. http://monad.carnalreason.org/wordpress/?p=20 56. http://www.dailyspeculations.com/ 57. http://memeagora.blogspot.com/2006/12/polyglot-programming.html 58. http://gimbo.org.uk/archives/2006/12/#001887 59. http://jpmoresmau.blogspot.com/2006/12/in-haskell-you-can-define-infinite.h… 60. http://clemens.endorphin.org/weblog/archives/2006-06.shtml#e2006-06-23T09_1… 61. http://blogs.teamb.com/craigstuntz/archive/2006/12/08/UnitTestingAndTypeSaf… 62. http://koweycode.blogspot.com/2006/12/rewriting-pleac-haskell.html 63. http://www.alpheccar.org/en/posts/show/61 64. http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/11#interpreters-with-reader-m… 65. http://neilmitchell.blogspot.com/2006/12/bhc-basic-haskell-compiler.html 66. http://www.cse.unsw.edu.au/~dons/blog/2006/12/11#release-a-library-today Quotes of the Week * Jim Apple: The Haskell list probably has the widest 'knowledge bandwidth' of any mailing list I've ever seen, from total beginner questions to highly abstruse stuff which probably represents the cutting edge of PhD research. All are answered with detail and good humour. * [Seen on the Haskell mailing list]: Wow! I found your help terrific! Thank you! Can I give you some money? * Paul Johnson: Is functional programming an actual bona-fide silver bullet as defined by Brooks? I believe it is. Functional programming is based on a sound theory of scalable software engineering, and the empirical evidence clearly and consistently supports the theory. * Clemens Fruhwirth: After all the elegance I have to conclude that Haskell definitely deserves to be looked at. * sorear: Haskell is amazing. I'm still working on my infinite-types unifier, and in a day I've added sums, products, and lambda abstractions, refactored the code until there was a net *decrease* in LOC, and helped man #haskell all at the same time. This'd take me a week in C, no doubt. * Claus Reinke: The aim of update programming is to transform a store whose contents describe a problem into a store whose contents describe a solution. The aim of functional programming is to transform a program which describes a problem into a program which describes a solution. * Daveman: What if I don't want to obey the laws? Do they throw me in jail with the other bad monads? * Stinger: Sometimes Haskell seems like an arms race between weird mathematical constructs and my brain * astrolabe: Below a certain level of competence, coding is a destructive act. Like playing the violin. * dons: Gimme some lambda warez! * wy: [wy] lennart: Wow. You won the IOCCC three times! [augustss] I'm bad at C programming ;) * shapr: I think the Haskell approach works fine. That is, stick with research and do the best you can. Then after fifteen years of gestation, take over the world. * edwinb: Where does 'Oleg cornered me in a pub and explained delimited continuations to me' fit in? * emu: Design patterns are what you choose for wallpaper and carpets * kyevan: My skull is already mostly duct tape. And I'm only on page 25 of YAHT! * shapr: There's an important niche market for OSes that don't crash. Code Watch Tue Dec 5 23:18:45 PST 2006. Simon Peyton Jones. [67]Improve dependency analysis makes more dictionaries inlinable. 67. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/18123 Sat Dec 9 09:42:03 PST 2006. Ian Lynagh. [68]Add PowerPC to the list of SMP arches 68. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/18173 Mon Dec 11 14:25:34 PST 2006. Wolfgang Thaller. [69]Support MO_WriteBarrier in PowerPC NCG (lwsync instruction). 69. http://article.gmane.org/gmane.comp.lang.haskell.cvs.ghc/18217 About the Haskell Weekly News Each week, new editions are posted to [70]the Haskell mailing list as well as to [71]the Haskell Sequence and [72]Planet Haskell. [73]RSS is also available, and headlines appear on [74]haskell.org. Headlines are available as [75]PDF. The Haskell Weekly News is also [76]available in Spanish translation. To help create new editions of this newsletter, please see the [77]contributing information. Send stories to dons at cse.unsw.edu.au. The darcs repository is available at darcs get [78]http://www.cse.unsw.edu.au/~dons/code/hwn 70. http://www.haskell.org/mailman/listinfo/haskell 71. http://sequence.complete.org/ 72. http://planet.haskell.org/ 73. http://sequence.complete.org/node/feed 74. http://haskell.org/ 75. http://www.cse.unsw.edu.au/~dons/code/hwn/archives/20061212.pdf 76. http://haskell.org/haskellwiki/HWN/es 77. http://haskell.org/haskellwiki/HWN 78. http://www.cse.unsw.edu.au/~dons/code/hwn

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[newbie]any nice code to read?
by 云杨 11 Dec '06

11 Dec '06

hello,all, I am new to haskell,and have read some tutorial, but I would like to read some "real" code from "real" haskell project, I believe this will help me study and use haskell quickly. would anyone please give me some suggestion about opensource project that a new haskell user should study? thanks you.

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ANNOUNCE: dlist, difference lists supporting O(1) append
by dons＠cse.unsw.edu.au 11 Dec '06

11 Dec '06

This is DList, 0.1 I've cabalised, and packed up a small difference lists module. In case you've not used them, they are a Haskell idiom for implementing O(1) append and snoc, using functions to represent lists. I use them from time to time, and thought it a good idea to finally pack them into a library for all to share. Home: http://www.cse.unsw.edu.au/~dons/dlist.html Docs: http://www.cse.unsw.edu.au/~dons/dlist/Data-DList.html Source: http://www.cse.unsw.edu.au/~dons/code/dlist/ I've also described the entire process of releasing this library here: http://cgi.cse.unsw.edu.au/~dons/blog/2006/12/11#release-a-library-today Cheers, Don P.S. If you love Haskell, you'll write a library today!

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Call for papers -- FOAL: Foundations of Aspect-Oriented Languages 2007
by Ralf Lammel 11 Dec '06

11 Dec '06

[Added a subject. Please accept my apologies! Foundations of AOP and AO languages have benefitted from the functional programming community for a while now. Haskellers, please have a look. Thanks! Ralf] Call For Papers FOAL: Foundations of Aspect-Oriented Languages 2007 A one day workshop affiliated with AOSD 2007 in Vancouver, British Columbia. Submission Deadline: 23:00 GMT, 10 January 2007 Notification of Acceptance: 2 February 2007 Final Versions of Papers Due: 1 March 2007 Workshop: 13 March 2007 Themes and Goals FOAL is a forum for research in foundations of aspect-oriented programming languages. Areas of interest include but are not limited to: * Semantics of aspect-oriented languages * Specification and verification for such languages * Type systems * Static analysis * Theory of testing * Theory of aspect composition * Theory of aspect translation (compilation) and rewriting The workshop aims to foster work in foundations, including formal studies, promote the exchange of ideas, and encourage workers in the semantics and formal methods communities to do research in the area of aspect-oriented programming languages. All theoretical and foundational studies of this topic are welcome. The goals of FOAL are to: * Make progress on the foundations of aspect-oriented programming languages. * Exchange ideas about semantics and formal methods for aspect-oriented programming languages. * Foster interest within the programming language theory and types communities in aspect-oriented programming languages. * Foster interest within the formal methods community in aspect-oriented programming and the problems of reasoning about aspect-oriented programs. Workshop Format The planned workshop format is primarily presentation of papers and group discussion. Talks will come in three categories: long (30 minutes plus 15 minutes of discussion), regular (20 minutes plus 5 minutes of discussion) and short (7 minutes plus 3 minutes of discussion). The short talks will allow for presentations of topics for which results are not yet available, perhaps for researchers who are seeking feedback on ideas or seek collaborations. We also plan to ensure sufficient time for discussion of each presentation by limiting the overall number of talks. Submissions Invitation to the workshop will be based on papers selected by the program committee; those wishing to attend but not having a paper to submit should contact the organizers directly to see if there is sufficient space in the workshop. FOAL solicits long, regular, and short papers on all areas of formal foundations of AOP languages. Submissions will be read by the program committee and designated reviewers. Papers will be selected for long, regular, and short presentation at the workshop based on their length, scientific merit, innovation, readability, and relevance. Papers previously published or already being reviewed by another conference are not eligible. Some papers may not be selected for presentation, and some may be selected for presentation in shorter talks than their paper length would otherwise command. We will limit the length of paper presentations and the number of papers presented to make sure that there is enough time for discussion. Papers presented at the workshop will be included in a technical report (from Iowa State University). Authors will retain their own copyright to the papers. Publication of papers at other venues will thus remain possible. We will also investigate having a special issue of a journal for revisions of selected papers after the workshop. Authors should note the following details: * Submissions are due no later than 23:00 GMT, 10 January 2007. (This is a firm deadline.) * Authors must indicate whether they wish to be considered for a long, regular, or short presentation. * Papers for long presentations must not exceed 10 pages in length; those for regular presentations must not exceed 7 pages in length, and those for short presentations must not exceed 3 pages in length. * Some papers may not be selected for presentation, and some may be selected for presentation in shorter talks than requested. * We encourage use of the ACM Conference format <http://www.acm.org/sigs/pubs/proceed/template.html> for submissions, as this will be required for accepted papers. You must add page numbers (which are not part of the standard format) to your submissions, to make adding comments easier. * Submissions are to be made to the following URL: http://continue.cs.brown.edu/servlets/foal07/continue.ss We will notify the corresponding author of papers that are selected for presentation at the workshop by 2 February 2006. Early registration for AOSD (you must register for AOSD to attend the workshop) is 9 February 2006. Final versions of papers for the proceedings will be due on 1 March 2006. Important Dates Submission Deadline: 23:00 GMT, 10 January 2007 Notification of Acceptance: 2 February 2007 Final Versions of Papers Due: 1 March 2007 Workshop: 13 March 2007 For more information, visit the FOAL Workshop home page (at http://www.cs.iastate.edu/FOAL)

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(no subject)
by Ralf Lammel 11 Dec '06

11 Dec '06

[Foundations of AOP and AO languages have benefitted from the functional programming community for a while now. Haskellers, please have a look. Thanks! Ralf] Call For Papers FOAL: Foundations of Aspect-Oriented Languages 2007 A one day workshop affiliated with AOSD 2007 in Vancouver, British Columbia. Submission Deadline: 23:00 GMT, 10 January 2007 Notification of Acceptance: 2 February 2007 Final Versions of Papers Due: 1 March 2007 Workshop: 13 March 2007 Themes and Goals FOAL is a forum for research in foundations of aspect-oriented programming languages. Areas of interest include but are not limited to: * Semantics of aspect-oriented languages * Specification and verification for such languages * Type systems * Static analysis * Theory of testing * Theory of aspect composition * Theory of aspect translation (compilation) and rewriting The workshop aims to foster work in foundations, including formal studies, promote the exchange of ideas, and encourage workers in the semantics and formal methods communities to do research in the area of aspect-oriented programming languages. All theoretical and foundational studies of this topic are welcome. The goals of FOAL are to: * Make progress on the foundations of aspect-oriented programming languages. * Exchange ideas about semantics and formal methods for aspect-oriented programming languages. * Foster interest within the programming language theory and types communities in aspect-oriented programming languages. * Foster interest within the formal methods community in aspect-oriented programming and the problems of reasoning about aspect-oriented programs. Workshop Format The planned workshop format is primarily presentation of papers and group discussion. Talks will come in three categories: long (30 minutes plus 15 minutes of discussion), regular (20 minutes plus 5 minutes of discussion) and short (7 minutes plus 3 minutes of discussion). The short talks will allow for presentations of topics for which results are not yet available, perhaps for researchers who are seeking feedback on ideas or seek collaborations. We also plan to ensure sufficient time for discussion of each presentation by limiting the overall number of talks. Submissions Invitation to the workshop will be based on papers selected by the program committee; those wishing to attend but not having a paper to submit should contact the organizers directly to see if there is sufficient space in the workshop. FOAL solicits long, regular, and short papers on all areas of formal foundations of AOP languages. Submissions will be read by the program committee and designated reviewers. Papers will be selected for long, regular, and short presentation at the workshop based on their length, scientific merit, innovation, readability, and relevance. Papers previously published or already being reviewed by another conference are not eligible. Some papers may not be selected for presentation, and some may be selected for presentation in shorter talks than their paper length would otherwise command. We will limit the length of paper presentations and the number of papers presented to make sure that there is enough time for discussion. Papers presented at the workshop will be included in a technical report (from Iowa State University). Authors will retain their own copyright to the papers. Publication of papers at other venues will thus remain possible. We will also investigate having a special issue of a journal for revisions of selected papers after the workshop. Authors should note the following details: * Submissions are due no later than 23:00 GMT, 10 January 2007. (This is a firm deadline.) * Authors must indicate whether they wish to be considered for a long, regular, or short presentation. * Papers for long presentations must not exceed 10 pages in length; those for regular presentations must not exceed 7 pages in length, and those for short presentations must not exceed 3 pages in length. * Some papers may not be selected for presentation, and some may be selected for presentation in shorter talks than requested. * We encourage use of the ACM Conference format <http://www.acm.org/sigs/pubs/proceed/template.html> for submissions, as this will be required for accepted papers. You must add page numbers (which are not part of the standard format) to your submissions, to make adding comments easier. * Submissions are to be made to the following URL: http://continue.cs.brown.edu/servlets/foal07/continue.ss We will notify the corresponding author of papers that are selected for presentation at the workshop by 2 February 2006. Early registration for AOSD (you must register for AOSD to attend the workshop) is 9 February 2006. Final versions of papers for the proceedings will be due on 1 March 2006. Important Dates Submission Deadline: 23:00 GMT, 10 January 2007 Notification of Acceptance: 2 February 2007 Final Versions of Papers Due: 1 March 2007 Workshop: 13 March 2007 For more information, visit the FOAL Workshop home page (at http://www.cs.iastate.edu/FOAL)

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Num is such a fat and greedy class
by Dan Weston 11 Dec '06

11 Dec '06

The following observations are not new, insightful, or gracious, but I was lusting after the innocent +,-,* operators for my own evil ends and was mildly curious why... Num is such a fat and greedy class. If you want to marry Cinderella, you have to take her ugly stepsisters too. 1) Groups may only want to define addition. Why can't they use + (instead of <+>, >++++?&**+>, or other such perversion)? 2) Affine spaces have a (-) but no (+). Worse, the signature might be (-) :: Point -> Point -> Vector, which doesn't unify with (a -> a -> a). Wouldn't the following be more useful/general? class Subtraction a b | a -> b where (-) :: a -> a -> b Or would this require needless type annotation for the common subset of (a -> a -> a) instances? 3) Quaternions have no signum, unit quaternions have (*), (/) but no (+) or (-), abs would have a different signatures (Quaternion -> Double) which doesn't unify with (a -> a), and fields cannot be scaled with (*) as in (*) :: (Field f) => Double -> f -> f Would it not make sense to put each of these operators (division too) into their own individual superclasses that Num inherits? My (obviously naive) philosophy about type classes is that operations should be bundled only when they are mutually recursive (i.e. there is more than one useful minimal definition). If there is just one minimal set of operations, they can be in their own parent class too. Then again, I should get over my lust and stick with my own operators <+++++++++>, <---------------------->, and <*******>. Not too pretty, but they have a wonderful personality all their own! Dan

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Re: [Haskell] ANNOUNCE: ZMachine 0.0
by Samuel Bronson 09 Dec '06

09 Dec '06

On 12/9/06, Neil Mitchell <ndmitchell(a)gmail.com> wrote: > Hi Samuel, > > For future releases can you put up a little description of what a Z > Machine is in the email? Hmm. That would probably be a good idea ;-). But I don't see why I can't do that now, too. Except I actually want to describe the Z-machine, because apparantly the Z machine is a big giant machine covered in what looks like lightning. Anyway, here is the description from Wikipedia: The Z-machine is a virtual machine that was developed by Joel Berez and Marc Blank in 1979 and used by Infocom for its text adventure games. Infocom compiled game code to files containing Z-machine instructions (called story files, or Z-code files), and could therefore port all its text adventures to a new platform simply by writing a Z-machine implementation for that platform. With the large number of incompatible home computer systems in use at the time, this was an important advantage over using native code (or developing some compiler for each system). And I'll also note that, since then, a lot of people have used Graham Nelson's Inform compiler to write their own "text adventure games" (or "interactive fiction", as they like to call it) for the Z-machine, many of which are available at the IF archive (ifarchive.org)

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