May 2007 - Haskell - Haskell.org

ambiguous record field names which actually aren’t ambigious
by Wolfgang Jeltsch 28 May '07

28 May '07

Hello, I have the following modules: module A where data A = A { label :: Int } module B where data B = B { label :: Int } b :: B b = B { label = 0 } x :: B -> () x B { label = 0 } = () GHC reports an ambiguity for both usages of label. However, it should be clear that both usages can only refer to B.label since a field name in record syntax can only be one that is defined in the same module as the corresponding record type. Hugs accepts the above code. Is there a way to make GHC accept it too? Best wishes, Wolfgang

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ANN: Data.Derive 0.1
by Neil Mitchell 27 May '07

27 May '07

Hi I am pleased to announce Data.Derive. Webpage: http://www-users.cs.york.ac.uk/~ndm/derive/ Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/derive-0.1 Manual: http://www.cs.york.ac.uk/fp/darcs/derive/derive.htm >From the Manual: "Data.Derive is a library and a tool for deriving instances for Haskell programs. It is designed to work with custom derivations, SYB and Template Haskell mechanisms. The tool requires GHC, but the generated code is portable to all compilers. We see this tool as a competitor to DrIFT." To take a very small example, imagine you define your data structure: data Foo = ... Now you can derive instances using derive with --derive=Eq,Data,Serial etc. You can also use deriving ({-! Typeable, Show !-}) and $( derive makeEq ''Foo ). Advantages over DrIFT: * No need for a preprocessor with GHC * Easy to add new derivations outside of the library * Can often automatically infer instances from examples (see the manual) * A different set of instance derivations Thanks Neil (Co-authored with Stefan O'Rear, thanks to many others for code contributions!)

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Haskell Meeting in Leipzig, Germany, July 10th
by Johannes Waldmann 25 May '07

25 May '07

The second HAL (Haskell in Leipzig) meeting: Tuesday, July 10th. Including the release party for the Cohatoe project (= contributing Haskell to Eclipse), presented by author Leif Frenzel. More info, registration: http://www.iba-cg.de/haskell.html Looking forward to seeing you (again), Alf Richter, iba consulting; and Johannes Waldmann, HTWK Leipzig.

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Piffle, a Packet Filter Language
by Jaap Weel 25 May '07

25 May '07

I have written a compiler for a packet filter language in Haskell. I think this is a good example of how Haskell can be used in an application domain (low level computer networking) where people tend to use C for everything, including writing compilers. The language itself is not very fancy, from a Haskell programmer's point of view, but maybe you will still find this worth having at least a glance at. This is a very early release. Expect it to blow up in your face, or, more likely, fail to compile. Please report bugs. Thanks. /jaap --------------------------------------------------------------------------- PIFFLE, A PACKET FILTER LANGUAGE http://code.google.com/p/piffle What is Piffle? * "Piffle" is a pronounceable form of PFL, that is, Packet Filter Language. ("Piffle" is also an obscure word for "chatter".) * Piffle is a programming language for writing network packet filters. * The Piffle compiler accepts resource limits on the processor time and memory used for processing each packet of input; simply pass the -C or -M option, and it will check at compile time that your program cannot not exceed the limits you specify. * Piffle is easy to learn, because it is built around the familiar abstractions of procedural languages such as C and Pascal. * Piffle programs can be compiled with interchangeable back-ends called "boilerplates". The pcap boilerplate, which comes with the Piffle compiler, allows Piffle programs to read and write pcap/tcpdump dump files, to read packets from network devices, and to preprocess packets with Berkeley Packet Filters. You can write your own boilerplates to talk to other network monitoring interfaces, such as tun/tap. * Piffle runs on GNU/Linux systems, and is designed to be portable to other POSIX-compliant systems that run the GNU C Compiler gcc and the Glasgow Haskell Compiler ghc. * Hopefully, Piffle will in the future become available as an operation in Streamline, an advanced network monitoring framework, formerly known as FFPF, the fairly fast packet filter. Streamline is being developed at the VU Amsterdam Computer Systems Section. Within Streamline, Piffle will coexist with Ruler, a regular-expression based packet rewriting language. The author Piffle was designed and implemented by Jaap Weel as part of the Compiler Construction Practical course at the VU Amsterdam CS department. Read the code Feel free to have a look at the source and do with it as you please (within the bounds of the GPL, of course). Download the code For the most recent tarball release, which may still be broken, check the downloads page. For the latest (and even more possibly broken) version of Piffle, you will have to use subversion. Read the documentation Be sure to have a look at the latest published version of the manual. Contribute I would very much appreciate if people could try to compile and run Piffle (in particular make test) on their own machines, and report any problems on the issues page or by e-mail. Get in touch with the author You can contact the author at weel at ugcs dot caltech dot edu , or visit his web site at http://www.ugcs.caltech.edu/~weel.

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IFL 2007: Symposium on Implementation and Application of Functional Languages
by Olaf Chitil 25 May '07

25 May '07

********************************************************************** Announcement and Call for Papers for the 19th International Symposium on Implementation and Application of Functional Languages IFL 2007 27th-29th September 2007, Freiburg, Germany co-located with ICFP 2007 http://proglang.informatik.uni-freiburg.de/IFL2007/ ********************************************************************** The aim of the IFL symposium is to bring together researchers actively engaged in the implementation and application of functional and function-based programming languages. The symposium provides an open forum for researchers who wish to present and discuss new ideas and concepts, work in progress, preliminary results, etc. related primarily but not exclusively to the implementation and application of functional languages. Topics of interest include (but are not limited to): * language concepts * type checking * compilation techniques * (abstract) interpretation * generic programming techniques * automatic program generation * array processing * concurrent/parallel programming * concurrent/parallel program execution * heap management * runtime profiling * performance measurements * debugging and tracing * (abstract) machine architectures * verification * formal aspects * tools and programming techniques Papers on applications or tools demonstrating the suitability of novel ideas in any of the above areas and contributions on related theoretical work are also welcome. The change of the symposium name adding the term "application", introduced in 2004, reflects the broader scope IFL has gained over the years. Contributions Prospective authors are encouraged to submit papers to be published in the draft proceedings and present them at the symposium. All contributions must be written in English, conform to the Springer-Verlag LNCS series format and not exceed 16 pages. The draft proceedings will appear as a technical report. Every attendee of IFL 2007 will have the opportunity to submit a revised version of their paper for post-symposium reviewing. As in previous years, selected papers will be published by Springer Verlag in the Lecture Notes in Computer Science (LNCS) Series. Important Dates Submission for Draft Proceedings 31 August 2007 Early Registration Deadline 1 September 2007 Symposium 27-29 September 2007 Submission for post-refereeing 2 November 2007 Notification of acceptance / rejection 14 December 2007 Submission of camera-ready version 25 January 2008 Programme Committee Peter Achten Radboud University Nijmegen, The Netherlands Kenichi Asai Ochanomizu University, Japan Manuel Chakravarty The University of New South Wales, Australia Olaf Chitil (chair) University of Kent, UK Martin Erwig Oregon State University, Oregon, USA Marc Feeley Université de Montréal, Canada Martin Gasbichler Zühlke Engineering AG, Switzerland Kevin Hammond University of St. Andrews, Scotland Zoltán Horváth Eötvös Loránd University, Budapest, Hungary John Hughes Chalmers University of Technology, Sweden Ken Friis Larsen University of Copenhagen, Denmark Rita Loogen Philipps-Universität Marburg, Germany Michel Mauny ENSTA, France Sven-Bodo Scholz University of Hertfordshire, UK Clara Segura Universidad Complutense de Madrid, Spain Tim Sheard Portland State University, Oregon, USA Glenn Strong Trinity College, Dublin, Ireland Doaitse Swierstra Utrecht University, The Netherlands Malcolm Wallace The University of York, UK Local Organisation Markus Degen Universität Freiburg, Germany Peter Thiemann Universität Freiburg, Germany Stefan Wehr Universität Freiburg, Germany Further Information http://proglang.informatik.uni-freiburg.de/IFL2007/

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New book: Real-World Haskell!
by dons＠cse.unsw.edu.au 24 May '07

24 May '07

Bryan O'Sullivan, Don Stewart and John Goerzen are pleased, and frankly, very excited to announce that were developing a new book for O'Reilly, on practical Haskell programming. The working title is Real-World Haskell. The plan is to cover the major techniques used to write serious, real-world Haskell code, so that programmers can just get to work in the language. By the end of the book readers should be able to write real libraries and applications in Haskell, and be able to: * design data structures * know how to write, and when to use, monads and monad transformers * use Haskells concurrency and parallelism abstractions * be able to write parsers for custom formats in Parsec. * be able to do IO and binary IO of all forms * be able to bind Haskell to foreign functions in C * be able to do database, network and gui programming * know how to do exception and error handling in Haskell * have a good knowledge of the core libraries * be able to use the type system to track and prevent errors * take advantage of tools like QuickCheck, Cabal and Haddock * understand advanced parts of the language, such as GADTs and MPTCs. That is, you should be able to just write Haskell! The existing handful of books about Haskell are all aimed at teaching programming to early undergraduate audiences, so they are ill-suited to people who already know how to code. And while theres a huge body of introductory material available on the web, you have to be both tremendously motivated and skilled to find the good stuff and apply it to your own learning needs. The time has come for the advanced, practical Haskell book. Heres the proposed chapter outline: 1. Why functional programming? Why Haskell? 2. Getting started: compiler, interpreter, values, simple functions, and types 3. Syntax, type system basics, type class basics 4. Write a real library: the rope data structure, cabal, building projects 5. Typeclasses and their use 6. Bringing it all together: file name matching and regular expressions 7. All about I/O 8. I/O case study: a DSL for searching the filesystem 9. Code case study: barcode recognition 10. Testing the Haskell way: QuickCheck 11. Handling binary files and formats 12. Designing and using data structures 13. Monads 14. Monad case study: refactoring the filesystem seacher 15. Monad transformers 16. Using parsec: parsing a bioinformatics format 17. Interfacing with C: the FFI 18. Error handling 19. Haskell for systems programming 20. Talking to databases: Data.Typeable 21. Web client programming: client/server networking 22. GUI programming: gtk2hs 23. Data mining and web applications 24. Basics of concurrent and parallel Haskell 25. Advanced concurrent and parallel programming 26. Concurrency case study: a lockless database with STM 27. Performance and efficiency: profiling 28. Advanced Haskell: MPTCs, TH, strong typing, GADTs 29. Appendices We're seeking technical reviewers from both inside and outside the Haskell community, to help review and improve the content, with the intent that this text will become the standard reference for those seeking to learn serious Haskell. If you'd like to be a reviewer, please drop us a line at book-review-interest(a)realworldhaskell.org, and let us know a little about your background and areas of interest. Finally, a very exciting aspect of this project is that O'Reilly has agreed to publish chapters online, under a Creative Commons License! Well be publishing chapters incrementally, and seeking feedback from our reviewers and readers as we go. You can find more details and updates at the following locations: * The web site, http://www.realworldhaskell.org/blog/welcome/ * The authors, http://www.realworldhaskell.org/blog/about/ * The blog, http://www.realworldhaskell.org/blog/ -- Bryan O'Sullivan, Don Stewart and John Goerzen.

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boilerplate boilerplate
by Alex Jacobson 23 May '07

23 May '07

Consider this module for a blog entry that I will want to put in various generic collections that require Ord {-# OPTIONS -fglasgow-exts #-} module Blog.Types where import Data.Typeable import Data.Generics data BlogEntry = Entry EpochSeconds Name Email Title Body deriving (Eq,Ord,Read,Show,Typeable) newtype Name = Name String deriving (Eq,Ord,Read,Show,Typeable) newtype Title = Title String deriving (Eq,Ord,Read,Show,Typeable) newtype Body = Body String deriving (Eq,Ord,Read,Show,Typeable) It seems really unnecessarily verbose. Having to add the OPTION header AND import Data.Typeable and Data.Generics just to derive Typeable is a beat-down. It is even more of a beat-down to have to add a deriving clause for every newtype to make this all work nicely. Is there a way to make all types automatically derive everything unless there is an explicit instance declaration otherwise? {-# OPTIONS -fglasgow-exts -fgenerics -fderiving#-} module Blog.Types where data BlogEntry = Entry EpochSeconds Name Email Title Body newtype Name = Name String newtype Title = Title String newtype Body = Body String Isn't that much nicer? -Alex-

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PhD Studentship in Functional Programming
by Graham Hutton 23 May '07

23 May '07

---------------------------------------------------------------------+ PHD STUDENTSHIP IN FUNCTIONAL PROGRAMMING School of Computer Science and IT University of Nottingham, UK Applications are invited for a fully-funded PhD studentship on the EPSRC project "Reasoning About Exceptions and Interrupts", starting on 1st October 2007 for a period of three years. Most modern programming languages provide special features for detecting and managing unexpected events, in the form of exception and interrupt handling primitives. Despite their importance, the issue of provable correctness for programs involving these features has received little attention, but is particularly crucial given the difficulty of writing correct programs in this setting. The aim of this project is to address this problem within the context of a modern functional programming language such as Haskell and Epigram. Applicants for this position will require a first-class Honours degree (or equivalent) in Computer Science and/or Mathematics, some experience in functional programming, and an aptitude for mathematical subjects. Additional desirable attributes include a higher degree (e.g. Masters), and/or some experience in formal semantics, program verification, concurrency theory, or theorem provers. The successful applicant will work under the supervision of Dr Graham Hutton in the Foundations of Programming group in Nottingham, a leading centre for research on formal approaches to software construction and verification. The group currently comprises 7 academic staff, 5 research staff, and 13 PhD students. The position is open to UK and EU applicants, but particularly strong candidates from outside the EU may also be considered, subject to additional funding being available. Further details regarding the position and how to apply are available from Dr Graham Hutton, http://www.cs.nott.ac.uk/~gmh. Closing date for applications: 15th June 2007 +--------------------------------------------------------------------+ | Dr Graham Hutton Email : gmh(a)cs.nott.ac.uk | | School of Computer Science and IT | | University of Nottingham Web : www.cs.nott.ac.uk/~gmh | | Jubilee Campus, Wollaton Road | | Nottingham NG8 1BB, UK Phone : +44 (0)115 951 4220 | +--------------------------------------------------------------------+ 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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Composing channels
by Setzer, Sebastian (ext) 22 May '07

22 May '07

Hi, Suppose you've got two tasks, A and B, A wants sends a request to B, B sends a response. Both are sent through Control.Concurrent.Chan: +---+ +---+ | A |<--aChan bChan-->| B | +---+ +---+ A writes to bChan, B writes to aChan. Because B gets requests from several tasks, the request (and the type of bChan) includes aChan. As long as these tasks are threads of the same process, that's fine. But what can you do if there's a network (or some other kind of IPC) in between? If you didn't need to respond, you could try something like this: +---+ +---+ +---+ +---+ | A | cChan-->| C |--network--| D | bChan-->| B | +---+ +---+ +---+ +---+ A sends to cChan. C serializes the request, D deserializes it and sends to bChan. If you want to respond, it gets difficult. In order to send aChan through the network, you have to serialize it. When deserializing it, you have to create a channel in the process of D and B, which you can write into bChan and which B uses to respond. This channel will be read by a task which serializes the response, sends it through the network to the process of A and C, where it will be deserialized and written to aChan. Of course, you need to keep the serializing/deserializing in both processes consistent. For example by using the same shared object. Looks quite difficult. Are there any simpler solutions for typesafe network-communications? Are there plans to include some kind of "network transparent channels" in the haskell library (or are they already there and I overlooked them)? Sebastian Setzer

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Final APLAS'07 CFP
by Henrik Nilsson 22 May '07

22 May '07

On Behalf of Zhong Shao. Sorry for any duplicates! /Henrik ---------- Title: Final APLAS 2007 CFP (Deadline: June 15, 2007) [Recent updates: (1) Submission site is now open: <http://www.easychair.org/APLAS2007> (2) New info about invited speakers. (3) Deadline is just 3-week away. ] -------------------------------------------------------------------------- The Fifth ASIAN Symposium on Programming Languages and Systems (APLAS 2007) CALL FOR PAPERS Singapore November 29 - December 1, 2007 http://flint.cs.yale.edu/aplas2007/ APLAS aims at stimulating programming language research by providing a forum for the presentation of recent results and the exchange of ideas and experience in topics concerned with programming languages and systems. APLAS is based in Asia, but is an international forum that serves the worldwide programming languages community. The APLAS series is sponsored by the Asian Association for Foundation of Software (AAFS), which has recently been founded by Asian researchers in cooperation with many researchers from Europe and the USA. The past formal APLAS symposiums were successfully held in Sydney (2006, Australia), Tsukuba (2005, Japan), Taipei (2004, Taiwan) and Beijing (2003, China) after three informal workshops held in Shanghai (2002, China), Daejeon (2001, Korea) and Singapore (2000). Proceedings of the past symposiums were published in Springer-Verlag's LNCS 2895, 3302, 3780, and 4279. TOPICS: The symposium is devoted to both foundational and practical issues in programming languages and systems. Papers are solicited on, but not limited, to the following topics: * semantics, logics, foundational theory * type systems, language design * program analysis, optimization, transformation * software security, safety, verification * compiler systems, interpreters, abstract machines * domain-specific languages and systems * programming tools and environments Original results that bear on these and related topics are solicited. Papers investigating novel uses and applications of language systems are especially encouraged. Authors concerned about the appropriateness of a topic are welcome to consult with the program chair <aplas2007(a)easychair.org> prior to submission. INVITED SPEAKERS: Vincent Danos (University of Paris VII & CNRS, France) Sriram Rajamani (Microsoft Research, India) Vijay Saraswat (IBM TJ Watson Research Lab, USA) IMPORTANT DATES: Paper Submission Deadline: 11:00 AM (in Samoan Time), June 15, 2007 Author Notification: August 17, 2007 Camera Ready: September 7, 2007 Conference: November 29-December 1, 2007 SUBMISSIONS INFORMATION: Papers should be submitted electronically online via the conference submission web page at URL <http://www.easychair.org/APLAS2007>. Acceptable formats are PostScript or PDF, viewable by Ghostview or Acrobat Reader. Submissions should not exceed 16 pages in LNCS format, including bibliography and figures. Submitted papers will be judged on the basis of significance, relevance, correctness, originality, and clarity. They should clearly identify what has been accomplished and why it is significant. Submitted papers must be unpublished and not submitted for publication elsewhere. The proceedings of the symposium is planned to be published as a volume in Springer-Verlag's Lecture Notes in Computer Science series. GENERAL CHAIR Joxan Jaffar (National University of Singapore, Singapore) PROGRAM CHAIR Zhong Shao (Yale University, USA) PROGRAM COMMITTEE Lars Birkedal (IT University of Copenhagen, Denmark) Martin Hofmann (Univ of Munich, Germany) Kohei Honda (Queen Mary, University of London, UK) Atsushi Igarashi (Kyoto University, Japan) Suresh Jagannathan (Purdue University, USA) Annie Liu (State University of New York at Stony Brook, USA) Shin-Cheng Mu (Academia Sinica, Taiwan) Henrik Nilsson (University of Nottingham, UK) Michael Norrish (NICTA, Australia) Jens Palsberg (University of California, Los Angeles, USA) G. Ramalingam (Microsoft Research, India) Zhong Shao (Yale University, USA) Zhendong Su (University of California, Davis, USA) Martin Sulzmann (National University of Singapore, Singapore) Eijiro Sumii (Tohoku University, Japan) Jérôme Vouillon (CNRS, France) Kwangkeun Yi (Seoul National University, Korea) Jian Zhang (Chinese Academy of Sciences, China) LOCAL ARRANGEMENT CHAIR Wei-Ngan Chin (National University of Singapore, Singapore) -- Henrik Nilsson School of Computer Science and Information Technology The University of Nottingham nhn(a)cs.nott.ac.uk 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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