October 2007 - Haskell

pretty-printing Haskell with automatic parens?
by Conal Elliott 15 Oct '07

15 Oct '07

The haskell-src package contains a pretty-printer for Haskell syntax that requires parentheses to be explicitly placed in the (abstract) syntax representation. I have some code for automatically inserting parentheses where necessary (for use before pretty-printing), but I'm guessing someone else has done so better than I. Does anyone have pointers? I'm glad to share my version as well. Cheers, - Conal

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Fingerprints and hashing
by Simon Peyton-Jones 15 Oct '07

15 Oct '07

Dear Haskellers Here's a challenge. We are all familiar with the idea of an MD5 checksum, which provides a reliable "fingerprint" for a file, usually 128 bits or so. If the file changes, the fingerprint is (almost) certain to do so too. There are lots of techniques: CRC, shar?, MD5, etc. For various applications (including identifying common sub-expressions, and version tracking in GHC), I'd like a Haskell library that supports simple fingerprint operations. Below I give an informal specification of such a library. I can think of any number of implementations, but I'd like one that is (a) robust and (b) efficient. By "robust" I meant that with, say, a 128-bit fingerprint the chance of accidental collision is truly low; a non-robust implementation uses the 128-bit space in a non-uniform way [trivial example: gets stuck on zero]. Any takers? I bet some of you have this already, in some form. Simon The module signature would be something like this: data Fingerprint instance Eq Fingerprint instance Ord Fingerprint initialPrint :: Fingerprint class Fingerprintable t where fingerPrint :: t -> Fingerprint -> FingerPrint instance Fingerprintable Char instance Fingerprintable Int instance Fingerprintable Word32 -- etc The fingerPrint operation here is expressed in the traditional way: an accumulator (say 128 bits) into which one stuffs successive values (e.g. a byte stream). However, very important, I also want a more compositional form: instance Fingerprintable Fingerprint so that I can do something like fp :: Expr -> Fingerprint fp (App e1 e2) = fp e1 `fingerPrint` fp e2 Yes, I could thread the accumulator, thus: fp' :: Expr -> Fingerprint -> Fingerprint fp' (App e1 e2) p = fp' e1 (fp' e2 p) but I can't *always* do that; or even if I can, I may already *have* a fingerprint for e1 in my hand, and it's painful to re-traverse e1. Think of hash-consing. An obvious implementation of "instance Fingerprintable Fingerprint" is to divide one fingerprint into words, and feed it into the other via the Word32 instance. But it's not clear to me whether or not that is robust. (Incidentally, one could define the class thus: class Fingerprintable t where fingerPrint :: t -> FingerPrint plus plusFP :: Fingerprint -> Fingerprint -> Fingerprint But I think it'd be less efficient if that was the only way, because of all those now-compulsory plusFP operations.) I'd like one other thing: to be able to trade cost for accuracy. I'd like a 128-bit fingerprint with essentially zero chance of having two distinct values that map to the same fingerprint; and a one-word fingerprint that was a lot more efficient, but where collisions would be entirely possible (again hash-consing is an example).

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PLAN-X 2008 Deadline approaching
by Peter Thiemann 15 Oct '07

15 Oct '07

Call for Papers and Demos ========================= ****** Abstract deadline: Oct. 17, 2007 ****** Paper deadline: Oct. 22, 2007 PLAN-X 2008 --- Programming Language Techniques for XML ACM SIGPLAN Workshop colocated with POPL 2008 San Francisco, California, USA - 9 January 2008 http://gemo.futurs.inria.fr/events/PLANX2008/ The PLAN-X 2008 workshop is the forum to present and discuss bleeding-edge research at the intersection of programming language and data base technology with an emphasis on tree-shaped data structures and their XML representation. Topics of interest are all aspects of XML processing and querying: theories, methodologies, paradigms, language designs, types, analyses, runtime aspects, implementations, tools, applications. This edition of PLAN-X is particularly interested in blending the XML processing approaches developed by the programming languages and data management communities. Expressive power and high performance are among the common goals that these communities pursue. We encourage the submission of crosscutting contributions that apply techniques from one community to problems from the other. The primary criteria for paper selection are originality, relevance, and timeliness to ensure that we can enjoy reports on ongoing and unfinished work with high potential in the workshop. Submissions =========== We seek submissions in two categories * regular papers (10 pages, 30 minutes presentation) * demo papers (4 pages, 10 minutes plenary presentation + 30 minutes slot for individual discussions shared with other demos) For details see the submission instructions on http://gemo.futurs.inria.fr/events/PLANX2008/?page=subm Important Dates =============== Abstract deadline *** 17 October 2007 Submission deadline *** 22 October 2007 Notification 30 November 2007 Final papers due 14 December 2007 Program Committee ================= Veronique Benzaken Université de Paris-Sud 11, France Alin Deutsch University of California, San Diego, USA Wenfei Fan University of Edinburgh, UK Mary Fernandez ATT Research, USA Haruo Hosoya University of Tokyo, Japan Ralf Lämmel Universität Koblenz, Germany Sebastian Maneth National ICT and UNSW, Sydney, Australia Jim Melton Oracle Corporation, USA Michael Schwartzbach University of Aarhus, Denmark Jérôme Vouillon CNRS, France Ioana Manolescu (general chair) Gemo group, INRIA Futurs, France Peter Thiemann (program chair) University of Freiburg, Germany

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C++ bindings
by Wolfgang Jeltsch 12 Oct '07

12 Oct '07

Hello, what are good approaches for creating Haskell bindings to C++ libraries? The most promising so far seems to create C wrappers around the C++ libraries and then bind to them. Is it feasible to bind directly to C++ using ccall by relying on some standardized C++ ABI? What about H/Direct? Are there any other good ways? Thank you for any hints. Best wishes, Wolfgang

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[Fwd: Re: CFP - DAMP 2008 - Declarative Aspects of Multicore Programming]
by Simon Marlow 12 Oct '07

12 Oct '07

[ posting on behalf of Manuel Hermenegildo <herme(a)fi.upm.es>] Subject: CFP - DAMP 2008 - Declarative Aspects of Multicore Programming DAMP 2008: Workshop on Declarative Aspects of Multicore Programming San Francisco, CA, USA (colocated with POPL 2008) January 9, 2008 SUBMISSION DEADLINE: OCTOBER 26 Parallelism is going mainstream. Many chip manufactures are turning to multicore processor designs rather than scalar-oriented frequency increases as a way to get performance in their desktop, enterprise, and mobile processors. This endeavor is not likely to succeed long term if mainstream applications cannot be parallelized to take advantage of tens and eventually hundreds of hardware threads. Multicore architectures will differ in significant ways from their multisocket predecessors. For example, the communication to compute bandwidth ratio is likely to be higher, which will positively impact performance. More generally, multicore architectures introduce several new dimensions of variability in both performance guarantees and architectural contracts, such as the memory model, that may not stabilize for several generations of product. Programs written in functional or (constraint-)logic programming languages, or even in other languages with a controlled use of side effects, can greatly simplify parallel programming. Such declarative programming allows for a deterministic semantics even when the underlying implementation might be highly non-deterministic. In addition to simplifying programming this can simplify debugging and analyzing correctness. DAMP is a one-day workshop seeking to explore ideas in programming language design that will greatly simplify programming for multicore architectures, and more generally for tightly coupled parallel architectures. The emphasis will be on functional and (constraint-)logic programming, but any programming language ideas that aim to raise the level of abstraction are welcome. DAMP seeks to gather together researchers in declarative approaches to parallel programming and to foster cross fertilization across different approaches. Specific topics include, but are not limited to: * suitability of functional and (constraint-)logic programming languages to multicore applications; * run-time issues such as garbage collection or thread scheduling; * architectural features that may enhance the parallel performance of declarative languages; * type systems and analysis for accurately knowing or limiting dependencies, aliasing, effects, and nonpure features; * ways of specifying or hinting at parallelism; * ways of specifying or hinting at data placement which abstract away from any details of the machine; * compiler techniques, automatic parallelization, automatic granularity control; * experiences of and challenges arising from making declarative programming practical; * technology for debugging parallel programs; * design and implementation of domain-specific declarative languages for multi-core; Submission: Submitted papers papers should not exceed 15 pages in LLNCS format. Submission is electronic via: http://www.easychair.org/DAMP2008/ Important dates: Paper submission: Oct 26 Notification to authors: Nov 30 Camera ready: Dec 14 Program Chair: Manuel Hermenegildo Technical University of Madrid / IMDEA-Software -- herme(a)fi.upm.es University of New Mexico -- herme(a)unm.edu Program Committee: Koen De Bosschere (U. of Gent, Belgium) Manuel Carro (Tech. U. of Madrid, Spain) Manuel Chakravarty (U. of New S. Wales, Australia) Clemens Grelck (U. of Luebeck, Germany) Dan Grossman (U. of Washington, USA) Suresh Jagannathan (Purdue U., USA) Pedro Lopez-Garcia (Tech. U. of Madrid, Spain) Lee Naish (Melbourne University, Australia) Leaf Petersen (Intel Corporation, USA) Enrico Pontelli (New Mexico State U., USA) John Reppy (U. of Chicago, USA) Vitor Santos-Costa (U. of Porto, Portugal) General Chairs: Leaf Petersen Neal Glew Intel Corporation Santa Clara, CA, USA leaf.petersen(a)intel.com neal.glew(a)intel.com URL: http://www.cliplab.org/Conferences/DAMP08 Past DAMPs: http://glew.org/damp2006 http://www.cs.cmu.edu/~damp -- -- ------------------------------------------------------------------------------- Manuel Hermenegildo | Prof., C.S. Department Director, IMDEA-Software and CLIP Group | T.U. of Madrid (UPM) http://www.cliplab.org/herme | +34-91-336-7435 (W) -352-4819 (Fax) -------------------------------------------------------------------------------

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Abstract syntax representation
by paolot＠informatik.uni-bremen.de 11 Oct '07

11 Oct '07

Hi, I am writing translations of Haskell to specification languages. I was wondering whether there already exist a representation of Haskell syntax that, in contrast with standard abstract syntax, is "light" on structure (few data-types, few constructors) and has no dictionary parameters. Thanks, -paolo

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CFP: Intl Conf on Eval'n of Novel Approaches to Soft Eng
by Tony Sloane 10 Oct '07

10 Oct '07

[Apologies for multiple copies of this announcement that you may receive.] ENASE 2008 CALL FOR PAPERS 3rd International Conference on Evaluation of Novel Approaches to Software Engineering http://www.enase.org Funchal, Madeira, 4 - 7 May, 2008 organized by the Institute for Systems and Technologies of Information, Control and Communication (INSTICC) IMPORTANT DATES: Full Paper Submission: November 9, 2007 Authors Notification: January 4, 2008 Final Paper Submission and Registration: January 25, 2008 ENASE 2008 will be held in conjunction with WEBIST 2008 (http://www.webist.org) Mission The mission of the ENASE (Evaluation of Novel Approaches to Software Engineering) series of working conferences is to be a prime international forum to discuss and publish research findings and IT industry experiences with relation to evaluation of novel approaches to software engineering. By comparing novel approaches with established traditional practices and by evaluating them against software quality criteria, ENASE conferences advance knowledge and research in software engineering, identify most hopeful trends and propose new directions for consideration by researchers and practitioners involved in large-scale software development and integration. Goals and Topics of Interest ENASE provides a yearly forum for researchers and practitioners to review and evaluate relatively new and original in conception SE methods, practices, architectures, technologies and tools. An important underpinning and assumption of ENASE is that in software engineering "novel" turns out frequently to be just new hype. An objective of ENASE is to reveal any such hype as soon as feasible. This means that ENASE does not exclude more traditional approaches to software development and integration. On the contrary, ENASE endeavors to compare novel with traditional, also to discover if novel is not just traditional in disguise. Consequently, ENASE accepts also papers concentrating on a critique of more established and popular SE approaches. Against that background, ENASE undertakes to provide fast but careful scientific and empirical evaluation of new as well as more established approaches to software engineering. Of particular interest are experience reports and evaluations (qualitative and quantitative) of existing approaches as well as new ideas and proposals for improvements. The conference solicits experiments, case studies, surveys, meta-analyses, empirical studies, systematic reviews, conceptual explorations, innovative ideas, critical appraisals, etc. related to: * agile software development, * aspect-oriented software development, * agent-oriented software engineering, * multi-agent systems, * model-driven engineering, * component-based software engineering, * evolutionary design, * intentional software, * example centric programming, * meta programming systems, * knowledge management and engineering, * architectural design and meta architectures, * business process management, engineering and reengineering, * process-centric paradigms, * service-oriented architectures, * application integration technologies, * enterprise integration strategies and patterns, * e-business technologies, * requirements engineering frameworks and models, * collaborative requirements management systems, * business and software modeling languages, * software quality management, * software change and configuration management, * geographically distributed software development environments, * cross-feeding between data engineering and software engineering, * design thinking as a paradigm for software development, * formal methods, * software process improvement, * metamodelling, * software development methodologies Conference Format There will be full papers presented to the conference by the authors, poster papers available for viewing and discussions, and demo papers available for viewing and related to the demonstrations of software tools and products. Conference Publications All accepted papers will be published in the conference proceedings, under an ISBN reference, in paper and in CD-ROM support. A book including a selection of the best full papers will be edited and published by Springer-Verlag. Conference Chairs Joaquim Filipe (Polytechnic Institute of Setúbal / INSTICC, Portugal) Leszek A. Maciaszek (Macquarie University ~ Sydney, Australia) Program Chairs Cesar Gonzalez-Perez (Neco, Spain) Stefan Jablonski (University of Bayreuth, Germany)

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Converting Double from String
by bjornie 08 Oct '07

08 Oct '07

Hi! I'm kind of new to functional programming with Haskell, I'm reading a university course you see. Now I'm having some problems with one of our lab assignments, we're supposed to write a program handling numeric operations (addition, multiplication, and some functionality like sin and cos). I've made a data type; data Expr = Num Double | Add Expr Expr | Mul Expr Expr... I.e for representing the expression: 2.4 * (4.0 + 1.5) The Haskell representation is: Mul (Num 2.4) (Add (Num 4.0) (Num 1.5)) My problem is to convert a String to an expression like the one above. I.e the String: "2.4*(4.0+1.5)" If we would use plain Integers there would not be a problem, since the Prelude function 'digitToInt' :: Char -> Int does nearly what I would like to do. But I'm stuck on the Doubles! How can I solve this in a smooth way? -- View this message in context: http://www.nabble.com/Converting-Double-from-String-tf4586633.html#a13092415 Sent from the Haskell - Haskell mailing list archive at Nabble.com.

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Haskell Applications - reg
by Ganesh Narayan 07 Oct '07

07 Oct '07

Hi List, I am planning a study on statistical properties of (static) call graphs for programs written in different languages; the idea is to compute a handful of "relevant" graph structural metrics and see what they have to say about the software/language. In this lieu, I am studying following languages - C, C++, Haskell, OCaml and hopefully Scheme and Java. I picked up a handful of Haskell applications from Haskell Apps repository [0] and computed the call graph for them [1]. But am not quite sure if the applications are representative; for one, the graphs are quantitatively distinct! In addition, this difference appears consistent across the Haskell applications I tried. Am not sure if its GHC compiler/runtime effect or Haskell effect though. Should the effects are artifact of disassembly, likely that OCaml graphs would have exhibited them too. Is there any particular application(s) that is quintessentially Haskell'sh that I could convince myself that my samples are representative?! I am fledging new to Haskell and would appreciate some pointers in picking up the "few, but ripe" ones. Hope it's fine. In case any list member is curious, I have got some preliminary plots hosted at http://agni.csa.iisc.ernet.in/nganesh/plots ; horizontal dividers represent language boundaries [top, bottom) and in/out/total stand for degrees. I have five Haskell applications enlisted: Yarrow, Frown, DrIFT, HaXml.{Validate/Extract}. Thanks -ganesh [0] http://www.haskell.org/haskellwiki/Applications_and_libraries; I picked up whatever I could compile. I am yet to get cabal running. [1] Am presently constructing the call graphs from disassembled application binaries; resultant graph includes ghc runtime library calls.

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ANNOUNCE: network-bytestring 0.1.1: Fast and memory efficient low-level networking
by Johan Tibell 07 Oct '07

07 Oct '07

network-bytestring: Fast and memory efficient low-level networking ---------------------------------------------------------------------- Strict ByteString versions of the recv/send family of functions, now available from Hackage: tarball: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/network-bytestri… darcs: darcs get http://code.haskell.org/network-bytestring The 'network-bytestring' package provides more efficient networking by using strict ByteStrings instead of Strings for sending and receiving data. -- Johan

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