May 2006 - Haskell - Haskell.org

Announcing Djinn, version 2004-12-11, a coding wizard
by Lennart Augustsson 07 Apr '11

07 Apr '11

Howdy, y'all! I've written a small program that takes a (Haskell) type and gives you back a function of that type if one exists. It's kind of fun, so I thought I'd share it. It's probably best explained with a sample session. calvin% djinn Welcome to Djinn version 2005-12-11. Type :h to get help. # Djinn is interactive if not given any arguments. # Let's see if it can find the identity function. Djinn> f ? a->a f :: a -> a f x1 = x1 # Yes, that was easy. Let's try some tuple munging. Djinn> sel ? ((a,b),(c,d)) -> (b,c) sel :: ((a, b), (c, d)) -> (b, c) sel ((_, v5), (v6, _)) = (v5, v6) # We can ask for the impossible, but then we get what we # deserve. Djinn> cast ? a->b -- cast cannot be realized. # OK, let's be bold and try some functions that are tricky to write: # return, bind, and callCC in the continuation monad Djinn> type C a = (a -> r) -> r Djinn> returnC ? a -> C a returnC :: a -> C a returnC x1 x2 = x2 x1 Djinn> bindC ? C a -> (a -> C b) -> C b bindC :: C a -> (a -> C b) -> C b bindC x1 x2 x3 = x1 (\ c15 -> x2 c15 (\ c17 -> x3 c17)) Djinn> callCC ? ((a -> C b) -> C a) -> C a callCC :: ((a -> C b) -> C a) -> C a callCC x1 x2 = x1 (\ c15 _ -> x2 c15) (\ c11 -> x2 c11) # Well, poor Djinn has a sweaty brow after deducing the code # for callCC so we had better quit. Djinn> :q Bye. To play with Djinn do a darcs get http://darcs.augustsson.net/Darcs/Djinn or get http://darcs.augustsson.net/Darcs/Djinn/Djinn.tar.gz Then just type make. (You need a Haskell 98 implementation and some libraries.) And then start djinn. For the curious, Djinn uses a decision procedure for intuitionistic propositional calculus due to Roy Dyckhoff. It's a variation of Gentzen's LJ system. This means that (in theory) Djinn will always find a function if one exists, and if one doesn't exist Djinn will terminate telling you so. This is the very first version, so expect bugs. :) Share and enjoy. -- Lennart

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Haskell-mode 2.0
by Stefan Monnier 02 Feb '09

02 Feb '09

I have recently taken over maintainership of Haskell-mode, and after making a bunch of changes, I figured it would be a good idea to make a new release. You can find this new release at: http://www-perso.iro.umontreal.ca/~monnier/elisp/ If you think it should also be found at http://www.haskell.org/haskell-mode/, then please tell John Peterson to get back to me (my email to him seem to go straight to the bitbucket. John?). This release has several changes that have all been only lightly tested, especially w.r.t compatibility with various Emacsen. See appended the NEWS file that describes some of the notewirthy changes. Stefan Changes since 1.45: * keybindings C-c <char> have been replaced by C-c C-<char> so as not to collide with minor modes. * The following modules are now automatically activated without having to add anything to haskell-mode-hook: haskell-font-lock (just turn on global-font-lock-mode). haskell-decl-scan (just bind `imenu' to some key). * In recent Emacsen, haskell-doc hooks into eldoc-mode. * haskell-hugs and haskell-ghci are superceded by inf-haskell. * Indentation rules have been improved when using layout inside parens/braces. * Symbols like -> and \ can be displayed as actual arrows and lambdas. See haskell-font-lock-symbols. * Tweaks to the font-lock settings. Among other things paren-matching with things like \(x,y) should work correctly now. * New maintainer <monnier(a)gnu.org>.

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Compilation of big, computed tables
by Stefan Karrmann 24 Oct '06

24 Oct '06

Dear all, can ghc compile huge tables into efficient code if they are constant at compile time? Two examples may clearify the question: big1 :: UArray Int Char big1 = array (0,1000) $! map (\i -> (i,toEnum i)) [0..1000] big2 = sum [0..10000]::Int -- == 50005000 == n*(n+1)/2 where n = 10000 Both values are constant at compile time. As they are given by pure functions, the compiler could evaluate them and write the *result* into the object file 'foo.o'. This would save code size and run time. I peeked into 'foo.hc' but I didn't found 0x2fb0408 nor an array {0, 1, 2, 3, ..., 1000} or similar things. The function in big2 should show that the computation of the value could be very time consuming. If the compiler does not compute it, the source file could be generated by a helper program (or template Haskell?). The function in big1 should show that the conversion of the data into an array could be run-time, code-size and heap-size consuming. (You need the list (maybe explicitly - think of 1000 fixed pseudo-random numbers) and convert it into an array.) If the compiler generates the unboxed array directly it could be rather efficient. PS: I compiled with: ghc6 -c -O2 -keep-tmp-files -keep-hc-files foo.hs Regards, -- Stefan Karrmann

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"strange" behavior of Implicit Parameters
by Eike Scholz 08 Aug '06

08 Aug '06

Hi, I have just a short question, about the semantics of Implicit parameters on GHC 6.4. Given the following code: > (???) x f > = let ?foo = 1337 > in f x > fun :: (?foo::Int,Show x) => x -> String > fun x = "x = "++(show x)++"; ?foo = "++(show ?foo) > test = let ?foo = 23 > in 42 ??? fun I would expect: test == "x = 42; ?foo = 1337" Because I thought, that it gets reduced like: let ?foo = 23 in 42 ??? fun ~> let ?foo = 23 in (let ?foo = 1337 in fun 42) ~> ... ~> "x = 42; ?foo = 1337" however I get "x = 42; ?foo = 23" in ghci. Is there a special reason, why the implicit parameter is reduced first? Could it be a bug? Reducing it my way would be very useful for combinator-libraries, since it could be used passing around state info, or simple debug text, that tells where a Runtime-error occured? an odd example: > undef = error ?errstr > (<?>) x s = let ?errstr = ?errstr++"\n"++s in x -- annotate error tags so error annotations will accumulate and it would be easy to resolve runtime errors. best regards Eike Scholz

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CFP: APLAS 2006
by Eijiro Sumii 08 Jun '06

08 Jun '06

[sending on behalf of the program chair] **************************************************** *** The deadline of abstract submission: June 2 *** *** The deadline of paper submission: June 6 *** **************************************************** CALL FOR PAPERS The Fourth ASIAN Symposium on Programming Languages and Systems (APLAS 2006) Sydney, Australia, November 8-10, 2006 http://www.kb.ecei.tohoku.ac.jp/aplas2006/ 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 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, and 3780. 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 (koba(a)ecei.tohoku.ac.jp) prior to submission. GENERAL CO-CHAIRS Manuel Chakravarty (University of New South Wales, Australia) Gabriele Keller (University of New South Wales, Australia) PROGRAM CHAIR Naoki Kobayashi (Tohoku University) PROGRAM COMMITTEE Kung Chen (National Chengchi University, Taiwan) Wei-Ngan Chin (National University of Singapore, Singapore) Patrick Cousot (ENS, France) Masahito Hasegawa (Kyoto University, Japan) Jifeng He (United Nations University, Macau) Haruo Hosoya (University of Tokyo, Japan) Bo Huang (Intel China Software Center, China) Naoki Kobayashi (chair) (Tohoku University, Japan) Oege de Moor (Oxford University, UK) George Necula (University of California at Berkeley, USA) Martin Odersky (EPFL, Switzerland) Tamiya Onodera (IBM Research, Tokyo Research Laboratory, Japan) Yunheung Paek (Seoul National University, Korea) Sriram Rajamani (Microsoft Research, USA) Andrei Sabelfeld (Chalmers University of Technology, Sweden) Zhong Shao (Yale University, USA) Harald Sondergaard (University of Melbourne, Australia) Nobuko Yoshida (Imperial College London, UK) INVITED SPEAKERS Jens Palsberg (UCLA, USA) Peter Stuckey (University of Melbourne, Australia) SUBMISSIONS INFORMATION Papers should be submitted electronically online via the conference submission webpage. 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 will be published as a volume in Springer-Verlag's Lecture Notes in Computer Science series. Authors of accepted papers must provide all the electronic files of the final version of papers according to the instruction provided at the LNCS home page (www.springer.com/lncs) IMPORTANT DATES Abstract Submission: June 2, 2006 Paper Submission: June 6, 2006 Author notification: August 5, 2006 Camera Ready: August 25, 2006 Conference: November 8-10, 2006

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My summer of code project: HsJudy
by Caio Marcelo 04 Jun '06

04 Jun '06

Hey Haskell folks! I'm Caio Marcelo and my project for this Summer of Code is "Fast Mutable Collection Types for Haskell", I'll be implementing a lot of APIs for data collections (like Map and Arrays) using Judy library as backend. If you want to know more about it, take a look at my SoC blog at http://cmarcelo.blogspot.com. The repo is http://svn.openfoundry.org/pugs/third-party/HsJudy/. Comments, suggestions or ideas are all welcome. Thank you Haskell.org people for accepting my application! -- Caio Marcelo

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ANNOUNCE: Shellac and Lambda Shell 0.3
by Robert Dockins 31 May '06

31 May '06

Fellow Haskellers, I am pleased to announce the simultaneous release of Shellac 0.3 and Lambda Shell 0.3. Because I actually never got around to announcing the 0.2 releases, the following change lists are compared to versions 0.1. Shellac is a library for creating read-eval-print style shells. It makes binding to feature-rich shell packages (ie, readline) easier. Lambda shell is full-featured shell environment for evaluating terms of the pure untyped lambda calculus and a showcase/tutorial for Shellac's features. What's new in Shellac: * a revamped client API that doesn't suck * an API for plugable "backends". A basic backend which uses hGetLine is included. An optional package supplies a backend for readline. What's new in Lambda Shell: * Updated to use the new Shellac API * CPS transforms on terms The project homepages are: http://www.eecs.tufts.edu/~rdocki01/shellac.html http://www.eecs.tufts.edu/~rdocki01/lambda.html On these pages you will find links to source downloads, darcs repositories and, for Shellac, HTML documentation. The following is an example session with the lambda shell -------------------------------------------------------------- $ lambdaShell The Lambda Shell, version 0.3 Copyright 2005-2006, Robert Dockins The Lambda Shell comes with ABSOLUTELY NO WARRANTY; for details type ':nowarranty'. This is free software, and you are welcome to redistribute it under certain conditions; type ':gpl' for details > (\x y. x) (\a. a) (\b. b) \a. a > :load prelude.lam > :show four four = succ three > four \f x. f (f (f (f x))) > mul two three \f x. f (f (f (f (f (f x))))) > let x = plus six two > x == eight equal > x == nine not equal > one \f x. f x > [[ one ]] \f k. k (\x k_0. f x k_0) > :showcount showcount on > sub seven two \f x. f (f (f (f (f x)))) <<90 reductions>> > let l = insertSort (cons two (cons three (cons one nil))) > index zero l one <<463 reductions>> > index one l two <<2135 reductions>> > index two l three <<5720 reductions>> > :quit --------------------------------------------------------------- Enjoy! -- Rob Dockins Talk softly and drive a Sherman tank. Laugh hard, it's a long way to the bank. -- TMBG

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Importing things via the FFI?
by ihope 30 May '06

30 May '06

So I decided to pop into the FFI Report thing. I came up with this C file (which may or not actually be valid C; I'm not a C guy), called ffitest.h: > int add(Int x, Int y) { > return x+y; > } And ffitest.hs: > import Foreign.C.Types > > foreign import ccall "ffitest.h add" add :: CInt -> CInt -> CInt Ye error message: > During interactive linking, GHCi couldn't find the following symbol: > add > This may be due to you not asking GHCi to load extra object files, > archives or DLLs needed by your current session. (blah blah blah) Obviously I'm doing something wrong here, but what is it?

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CERTSOFT'06: Revised CFP
by Simon Marlow 29 May '06

29 May '06

[ posting on behalf of Jeffery Zucker <zucker(a)cas.mcmaster.ca>] ================================================================= CERTSOFT'06: AN INTERNATIONAL WORKSHOP ON SOFTWARE CERTIFICATION August 26 & 27, 2006 McMaster University, Hamilton, Ontario, Canada http://fm06.mcmaster.ca/certsoft In conjunction with FORMAL METHODS 2006 http://fm06.mcmaster.ca REVISED CALL FOR PAPERS [Note New Submission Deadline: June 16] GOAL OF THE WORKSHOP ==================== Software is currently used to control medical devices, automobiles, aircraft, manufacturing plants, nuclear generating stations, space exploration systems, elevators, electric motors, automated trains, banking transactions, telecommunications devices and a growing number of devices in industry and in our homes. Software is also mission critical for many organizations, even if the software does not `control' what happens. Clearly, many of these systems have the potential to cause physical harm if they malfunction. Even if they do not cause physical harm, their malfunctions are capable of causing financial and political chaos. Currently there is no consistent regulation of software, and society is starting to demand that software used in critical systems must meet minimum safety, security and reliability standards. Manufacturers of these systems are in the unenviable position of not having any clear guidelines as to what may be regarded as acceptable standards in these situations. Even where the systems are not mission critical, software producers and their customers are becoming interested in methods for assuring quality that may result in software supplied with guarantees. The purpose of the workshop is to discuss issues related to software certification. Possible topics include: - What is software certification, and what is its relation to system certification? - Methods, processes, and tools for developing certified software - Certifying safety-critical applications - Certifying embedded systems - Certifying non-critical but commercially significant applications - Certification of software components - Developing standards based on experimental analysis of methods - Formalization of Regulatory Requirements for Software - Repositories of assured/verified/validated software components - Using the Common Criteria for IT Security Evaluation as a model - Standardization of certification methods used in different industries - Evolutionary and incremental certification INVITED SPEAKERS ================ - David Parnas, University of Limerick - Rance Cleaveland, University of Maryland; Fraunhofer Center; Reactive Systems (Other speakers not yet confirmed) SUBMISSION INFORMATION ====================== Regular submissions should be no more than 15 pages and should be in PS or PDF file format. WE ESPECIALLY INVITE POSITION PAPERS, which should be no more than 10 pages. PROCEEDINGS OF THE WORKSHOP will be published and available at the workshop. If there is interest, and papers are felt to be of sufficient quality, we will seek publication of extended versions in a special issue of an appropriate journal. DEADLINES: Original submission: June 16, 2006 Notification of acceptance: July 3, 2006 Final version submission: July 28, 2006 PROGRAM COMMITTEE ================= Stefania Gnesi, ISTI-CNR, Italy -- Co-Chair Tom Maibaum, McMaster University, Canada -- Co-Chair Rance Cleaveland, University of Maryland, USA Alessandro Fantechi, University of Florence, Italy Jan Friso Groote, Eindhoven University of Technology, The Netherlands Connie Heitmeyer, Naval Research Laboratory, USA Paola Inverardi, University of L'Aquila, Italy Yoshiki Kinoshita, CVS-AIST, Japan Dino Mandrioli, Politecnico di Milano, Italy Jonathan Ostroff, York University, Canada Shankar, SRI International, USA David von Oheimb, Siemens AG, Germany (Additional members not yet confirmed) ORGANIZING COMMITTEE (all at McMaster University, Canada) ==================== Alan Wassyng -- Chair Wolfram Kahl Mark Lawford Jeff Zucker

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(.) . (.)
by Dominic Steinitz 29 May '06

29 May '06

Is this defined in some library? Thanks, Dominic.

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