- Haskell - Haskell.org

Power series in a nutshell
by Doug McIlroy 17 Jul '07

17 Jul '07

For lovers of things small and beautiful, http://www.cs.dartmouth.edu/~doug/powser.html boils down basic operations on power series with numeric coefficients to the bare minimum--each is a one-liner. Included are overloaded arithmetic operators, integration, differentiation, functional composition, functional inverse and coercion from scalars. --A telling demonstration of the power of lazy evaluation and of Haskell's attunement to math. Doug McIlroy

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(Succ Haskell') `and` $ dependent types
by Vivian McPhail 17 Jul '07

17 Jul '07

Hello, As the authors point out [1], coal-face time needs to be expended before real world adoption of Dependently-Typed functional programming. But let's get the ball rolling. They say that haskell programmers are normally averse to dependent types. Is this true? It seems to me that one of the appeals of Haskell is the ability to program in a "prove perfect, write once" (elegant) style. Is not dependent typing a good move towards this goal?. It addresses a problem [2] with which we, in our everyday common inter-hominem usage, can deal -- with which (ideal) Haskell should deal. While the major Haskell implementations would require a substantial overhaul, the change at the syntactic level appears to be minimal. There also needs to be advance with respect to programmer development (automatic edit-time inference of (some) types). What are peoples' thoughts on adding dependent types to haskell as a non-incremental evolutionary step? Does the haskell community want to stick with conservative additions to Haskell and a static base, or does the haskell community want to stay in step with the best theoretical developments? Vivian [1] http://www.informatik.uni-bonn.de/~loeh/LambdaPi.html [2] http://thread.gmane.org/gmane.comp.lang.haskell.cafe/21314

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ANNOUNCE: Haskell Hackathon 07 II: Freiburg: Oct 5-7
by dons＠cse.unsw.edu.au 17 Jul '07

17 Jul '07

------------------------------------------------------------------------ Hac 2007 II Haskell Hackathon 2007 II October 5-7, 2007 Freiburg, Germany http://haskell.org/haskellwiki/Hac_2007_II ------------------------------------------------------------------------ We are pleased to announce the 2nd Haskell Hackathon for 2007! The event will be held over 3 days, October 5-7 2007, at the University of Freiburg, in Germany, after ICFP. The plan is to hack on serious Haskell infrastructure, tools, libraries and compilers. To attend please register, and get ready to hack those lambdas! Code to hack on: * Hackage * Cabal * Porting foreign libraries * Bug squashing * You decide! At the last Hackathon, in January at Oxford, resulted in: * Cabal, Hackage, Haddock improvements * Data.Binary and DeferedBinary libraries * GHCi debugger improvements * ghc-api interface from Emacs * Crypto lirbary improvments * A native Haskell 'tar' implementation * And more And we hope to be similarly productive this time around. Before you attend, do start thinking and familiarising yourself with 1 or 2 projects you wish to work on, to ensure no wasted effort during the Hackathon. A list of possible projects is available on the website == Registration: We ask that you register you interest. Follow the instructions on the registration page: http://haskell.org/haskellwiki/Hac_2007_II/Register Once you've registered, do add your info to the attendees self-organising page, http://haskell.org/haskellwiki/Hac_2007_II/Attendees if you are looking to share costs, or meet up prior to the hackathon, with other attendees. N.B. if you already expressed interest via the wiki, do confirm by registering `officially' anyway. == Important dates: Hackathon: October 5-7, 2007 == Organisers: Duncan Coutts Ian Lynagh Don Stewart With local arrangements courtesy: Stefan Wehr Phillip Heidegger

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ANNOUNCE: CC-delcont-0.1; Delimited continuations for Haskell
by Dan Doel 15 Jul '07

15 Jul '07

Hello, After a bit of hacking, and much documenting, I'm pleased to announce a preliminary release of a delimited continuation library for Haskell. The implementation is drawn from "A Monadic Framework for Delimited Continuations"[1] by Dybvig, Petyon Jones and Sabry, although it has some abstraction available over said implementation (there is both a monad and a transformer; control operations will work interchangeably with either. In addition, all four control operators from "Shift to Control"[2] are implemented). In addition, I have done the adaptation necessary to include the Haskell implementation of the dynamic scoping investigated in "Delimited Dynamic Binding"[3] by Kiselyov, Shan and Sabry, and it has been included. One can think of it as embeddings of the reader or state monads into the delimited control monads (only more flexible). In the future, I'd like to also, possibly, include something like Oleg's generic zippers, and possibly other useful abstractions based on delimited continuations, if I find them. But that's work for another day, I suppose. If you wish to try it out, a package is available on hackage: Page: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/CC-delcont-0.1 Tabrall: http://hackage.haskell.org/packages/archive/CC-delcont/0.1/CC-delcont-0.1.t… However, I should warn that it's fairly dependent on GHC HEAD at the moment: 1) It uses the Unsafe.Coerce module 2) It uses GADTs to store type class evidence 3) It uses GHC-features that haddock will choke on, so haddock.ghc will be required for docs (and I haven't gotten that working yet to check that the haddock is bug-free), which in turn requires GHC HEAD. 1 & 2 could be relaxed if there's interest. Please feel free to let me know if you find any bugs, or have any suggestions for improvements. I'll follow up this message with a message containing an example program and a discussion thereof. Cheers, Dan Doel 1: http://www.cs.indiana.edu/~sabry/papers/monadicDC.pdf 2: http://www.cs.rutgers.edu/~ccshan/recur/recur.pdf 3: http://okmij.org/ftp/papers/DDBinding.pdf

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Cabal, Haddock, and the location of documentation
by Matthias Kilian 15 Jul '07

15 Jul '07

Hi, probably a PEBCAK, but working on updating all our Haskell-related OpenBSD ports, I've currently the problem, that, e.g. for Crypto the Haddock-generated documentation doesn't gets installed where I want it installed ;-) The default obviously is something like $prefix/share/Crypto-$VERSION/doc/html, but I want $prefix/share/doc/Crypto-$VERSION, or, even preferrable, just $prefix/share/doc/Crypto. That's: - $prefix/share/doc as base directory for all documentation, since that's the default on OpenBSD. - no html subdirectory if not strictly necessary, because I don't like a doc directory containing nothing but a html directory. - no version number in the directory name, because typically we don't have different versions of the same software installed at the same time -- there are exceptions from this rule, but I really don't plan to start maintaining several versions of one ore more Haskell packages ;-) Is this configurable at Cabal/Haddock runtime? I'd try to play with --datadir, but this appears a little bit dangerous as a general approach, since some packages my actually come with real data, which should *not* go into $prefix/share/doc, of course. Or do I have to patch Cabal? If so, what about adding just another FilePath like docdir to Distribution.SimpleLocalBuildInfo and use it for the documentation? Ciao, Kili

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AngloHaskell 2007, dates and venue confirmed
by Neil Mitchell 14 Jul '07

14 Jul '07

Hi, We are pleased to announce AngloHaskell 2007 http://www.haskell.org/haskellwiki/AngloHaskell Dates: 10th-11th of August (Friday-Saturday) Location: Cambridge, with talks at Microsoft Research on Friday All the details are on the wiki page, along with free registration. Everyone is invited, we will have a day of talks at MSR, then a day of other activities. There will be plenty of chance for general discussions on anything. If anyone in Cambridge is able to accommodate a few people for the Friday or Saturday night, please add your name to the wiki, and accept our thanks in advance. All that is needed is floor space. Thanks Neil and Philippa

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CFP: International Symposium on Functional and Logic Programming (FLOPS 2008)
by Jacques Garrigue 10 Jul '07

10 Jul '07

[We apologize for the multiple postings of this announce] FIRST CALL FOR PAPERS Ninth International Symposium on Functional and Logic Programming (FLOPS 2008) April 14-16, 2008 Ise, Japan Submission deadline: October 10, 2007 http://www.math.nagoya-u.ac.jp/~garrigue/FLOPS2008/ FLOPS is a forum for research on all issues concerning declarative programming, including functional programming and logic programming, and aims to promote cross-fertilization and integration between the two paradigms. Previous FLOPS meetings were held in Fuji Susono (1995), Shonan Village (1996), Kyoto (1998), Tsukuba (1999), Tokyo (2001), Aizu (2002), Nara (2004), and Fuji Susono (2006). TOPICS FLOPS solicits original papers in all areas of functional and logic programming, including (but not limited to): Declarative Pearls: new and excellent declarative programs with illustrative applications; Language issues: language design and constructs, programming methodology, integration of paradigms, interfacing with other languages, type systems, constraints, concurrency and distributed computing; Foundations: logic and semantics, rewrite systems and narrowing, type theory, proof systems; Implementation issues: compilation techniques, memory management, program analysis and transformation, partial evaluation, parallelism; Applications: case studies, real-world applications, graphical user interfaces, Internet applications, XML, databases, formal methods and model checking. The proceedings are expected to be published as an LNCS volume. The proceedings of the previous meeting (FLOPS2006) were published as LNCS 3945. INVITED SPEAKERS To be announced PC CO-CHAIRS Jacques Garrigue (Nagoya, Japan) Manuel Hermenegildo (Madrid, Spain and New Mexico, US) PC MEMBERS Maria Alpuente (Valencia, Spain) Sergio Antoy (Portland, OR, USA) Matthias Blume (TTI, Chicago, USA) Tyng-Ruey Chuang (Academia Sinica, Taiwan) Zhenjiang Hu (Tokyo, Japan) Oleg Kiselyov (FNMOC, Monterey, USA) Herbert Kuchen (Muenster, Germany) Dale Miller (INRIA, Palaiseau, France) Atsushi Ohori (Tohoku, Japan) Enrico Pontelli (New Mexico, USA) Kristoffer Rose (IBM Watson, USA) Kazunori Ueda (Waseda, Japan) Peter Van Roy (Louvain-la-Neuve, Belgium) Benjamin Werner (INRIA, Palaiseau, France) LOCAL CHAIR Shoji Yuen, Nagoya University SUBMISSION Submissions must be unpublished and not submitted for publication elsewhere. Work that already appeared in unpublished or informally published workshops proceedings may be submitted. Submissions should fall into one of the following categories: Regular research papers: they should describe new results and will be judged on originality, correctness, and significance. System descriptions: they should contain a link to a working system and will be judged on originality, usefulness, and design. All submissions must be written in English and can be up to 15 proceedings pages long. Authors are strongly encouraged to use LaTeX2e and the Springer llncs class file, available at http://www.springer.de/comp/lncs/authors.html Regular research papers should be supported by proofs and/or experimental results. In case of lack of space, this supporting information should be made accessible otherwise (e.g. a link to a web page, or an appendix). Submission is Web-based. Please visit the conference site. IMPORTANT DATES Submission deadline: October 10, 2007 Author notification: December 21, 2007 Camera-ready copy: January 21, 2008 Conference: April 14-16, 2008 PLACE Ise, Japan Previous FLOPS: FLOPS 2006, Fuji Susono: http://hagi.is.s.u-tokyo.ac.jp/FLOPS2006/ FLOPS 2004, Nara: http://logic.cs.tsukuba.ac.jp/FLOPS2004/ FLOPS 2002, Aizu: http://www.ipl.t.u-tokyo.ac.jp/FLOPS2002/ FLOPS 2001, Tokyo: http://www.ueda.info.waseda.ac.jp/flops2001/ SPONSOR Japan Society for Software Science and Technology (JSSST) SIG-PPL IN COOPERATION with Asian Association for Foundation of Software (AAFS) (pending) Association for Logic Programming (ALP) INQUIRIES to Jacques Garrigue (garrigue at math.nagoya-u.ac.jp)

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ANNOUNCE: HCL v1.0 -High-level library for building command line interfaces
by Justin Bailey 10 Jul '07

10 Jul '07

I'm please to announce HCL 1.0 - a library for building command line interfaces. The library exports a mix of low and high-level functions for building programs which gather simple values, ask yes/no questions, or present hierarchical menus. The library is not intended to do complex, full-screen UIs ala ncurses - it is intended for line-oriented interfaces. Included with the library is a hangman game, so if nothing else you can enjoy that. Where do I get it? ============= Download from Hackage at: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/HCL-1.0 How do I use it it? ============= It's Cabal-ized so, after downloading and unpacking: runghc Setup.hs configure runghc Setup.hs build runghc Setup.hs install Note I had some inconsistent results building with HEAD cabal, but the version distributed with GHC works great (1.1.6.2). To play hangman, execute 'hangman'. Once installed, you can look at it in GHCi by loading the "HCL" module. Tell me more! ========== This library lets you do a lot of cool things. For example, here's a simple guess a number game: guess_num_fun = do target <- reqIO $ getStdRandom (randomR (1::Integer,100)) let guessed val = case compare target val of GT -> do { reqIO $ putStrLn "Too low!"; return False } LT -> do { reqIO $ putStrLn "Too high!"; return False } EQ -> do { reqIO $ putStrLn "You win!"; return True } reqUntil guessed (prompt "Enter a number between 1 and 100: " reqInteger) "reqUntil" takes a predicate and asks for a response until the predicate is true. In the case above, the user is asked to enter an integer. Once they guess the number, the program ends. The library makes it easy to gather structured values. For example, imagine this data structure: data Taxpayer = Taxpayer { name :: String, age :: Int, ssn :: String } deriving (Read, Show) One way to use HCL to get Taxpayer values from the user is to take advantage of its Read instance: reqTaxpayer :: Request Taxpayer reqTaxpayer = prompt "Please enter tax payer information: " (reqRead reqResp) But that is ugly because the user has to type a "Read"-able string: > getTaxpayer reqTaxpayer Please enter tax payer information: Taxpayer {name="John", age = 30, ssn = "" } However, we can build a form of sorts and make life much easier for the user: reqTaxpayerEasy :: Request Taxpayer reqTaxpayerEasy = do name <- prompt "Please enter the tax payer's name: " reqResp age <- prompt "Please enter their age: " reqInt ssn <- prompt "What is their SSN/ASN: " reqResp return (Taxpayer name age ssn) Which looks like this: > getTaxpayer reqTaxpayerEasy Please enter the tax payer's name: Bob Please enter their age: 50 Please enter their SSN/ASN: 111-11-1111 The library also makes simple hierarchical menus easy to build. The below defines the menu structure for a hypothetical PIM: reqMenu $ reqSubMenu topMenu "Manage contacts" manageContactsMenu $ reqSubMenu topMenu "Manage calendar" (reqMenuItem "Add an event" ... $ ... reqMenuExit "Return to previous menu" reqMenuEnd) $ -- End the menu definition reqMenuEnd -- Defines a partial menu manageContactsMenu = reqMenuItem "Add a contact" ... $ ... reqMenuExit "Return to previous menu" reqMenuEnd These and more examples are distributed with the library in the examples directory. Anything else? =========== Feedback, praise and criticism are welcome. Feedback regarding 'idiomatic' usage is especially desired. This is a first for me so any responses are appreciated. The library was developed on Windows using GHC - please let me know of any odd *nix and Hugs bugs. This library was inspired in part by the Ruby HighLine library (http://highline.rubyforge.org/) Many thanks Mark Jones for his input on HCL's design and implementation.

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ANNOUNCE: logict-0.2
by Dan Doel 08 Jul '07

08 Jul '07

Hello all, I've just completed a library adapting the logic programming monad from the "Backtracking, Interleaving, and Terminating Monad Transformers" paper[1] into a format typical of the hierarchical libraries (based on MTL). It uses the two-continuation passing implementation described therein. Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/logict-0.2 Tarball: http://hackage.haskell.org/packages/archive/logict/0.2/logict-0.2.tar.gz Feel free to let me know if your find any bugs, or have suggestions. Dan Doel [1]: http://okmij.org/ftp/papers/LogicT.pdf

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ANN: functorm-1.0.1
by Stefan O'Rear 07 Jul '07

07 Jul '07

This is an update to remove a spurious dependency on the unix package (thanks to Andrea Vezzosi for the quick spot). I had used the vty cabal file as a template but forgot to fix the depenencies. Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/functorm-1.0.1 Tarball: http://hackage.haskell.org/packages/archive/functorm/1.0.1/functorm-1.0.1.t… Darcs: http://members.cox.net/stefanor/functorm Stefan

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