October 2012 - Haskell-Cafe

Safe lens?
by Greg Fitzgerald 31 Oct '12

31 Oct '12

Why are getters from the 'lens' package unsafe? Is there a subset like Data.Label.Pure from 'fclabels' that can be imported safely? $ cat a.hs {-# LANGUAGE Safe #-} import Control.Lens.Getter main = print 123 $ runghc a.hs a.hs:3:1: Control.Lens.Getter: Can't be safely imported! The module itself isn't safe. Thanks, Greg

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ANNOUNCE: network-house
by Niklas Hambüchen 30 Oct '12

30 Oct '12

In absence of a library that easily parses network packages from recorded raw data (not sockets), I have taken the network stack from the House project and put it into a separate package, network-house. http://hackage.haskell.org/package/network-house This library allows you to parse Ethernet, TCP, UDP, IPv4, IPv6, ICMP, DHCP and TFTP packages from raw data (e.g. recorded traffic). I have left the source code almost unmodified (apart from the relocation of one module and a few necessary LANGUAGE pragmas). As House development itself seems dormant, I invite you to collaborate on the network stack on https://github.com/nh2/network-house. If you would like to contribute, these are the things it definitely needs: * A ByteString interface (it currently works on UArrays). If you know what the most performant way is to convert a UArray to a ByteString, please let me know. * Some examples how to use it * Haddock documentation and code cleanup * Somebody should ask the original authors if they would like to relax the license from GPL to BSD. Cheers Niklas

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Optimal line length for haskell
by Rustom Mody 30 Oct '12

30 Oct '12

There was a recent discussion on the python list regarding maximum line length. It occured to me that beautiful haskell programs tend to be plump (ie have long lines) compared to other languages whose programs are 'skinnier'. My thoughts on this are at http://blog.languager.org/2012/10/layout-imperative-in-functional.html. Are there more striking examples than the lexer from the standard prelude? [Or any other thoughts/opinions :-) ] Thanks, Rusi

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GHC maintenance on Arch
by timothyhobbs＠seznam.cz 30 Oct '12

30 Oct '12

Hello, Who is in charge of the ghc and haskell packages on Arch linux? The current system isn't working. Arch linux tends to update packages very quickly. For ghc, always having the latest ghc isn't a good thing. At least if you actually want to get some work done. A majority of the time the latest GHC is unusable. This is because the packages in hackage simply don't keep up. With the current ghc version(7.6.1) even some basic packages in hackage are not upgraded yet. Right now, a large number of other haskell related packages are in the arch repos. Other than gtk2hs, I think these packages are pointless duplications. In the other cases, it has been my experience that it is simpler to maintain these packages through cabal rather than through pacman. Support for these packages in Arch should probably be dropped. If you want to get work done in Arch with haskell, you should only install ghc and cabal-install(right now, you'll have to search the Internet for the old binaries, because the arch repos usually don't keep the old versions around). Then you should add these packages to "IgnorePkg =" in pacman.conf this way things won't break every couple of months. You can then choose to upgrade when you wish. I hope that someone who is involved with the haskell Arch stuff reads this. The current model needs to be rethought. Linux should be sane by default, but I've lost many many hours learning that arch's relationship with haskell is not so :( Probably the best solution would be to make Arch automatically keep two versions of ghc around at any given time. Thank you for your time, Timothy Hobbs

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TAP 2013: 1st Call for Papers
by Achim D. Brucker 30 Oct '12

30 Oct '12

(Apologies if you receive this announcement multiple times. We also apologize for resending the first call for papers, the original announcement contained an incorrect URL to easychair.) **************************************************** *** *** *** TAP 2013 *** *** *** *** Abstract submission: January 25, 2013 *** *** Paper submission: February 1, 2013 *** **************************************************** *** TAP 2013 solicits both full papers and *** *** (industrial) experience/tool papers *** *** in combining proofs and (security) testing *** **************************************************** CALL FOR PAPERS 7th INTERNATIONAL CONFERENCE ON TESTS AND PROOFS (TAP 2013) http://www.spacios.eu/TAP2013 Budapest, Hungary, June 17-21, 2013 The TAP conference is devoted to the synergy of proofs and tests, to the application of techniques from both sides and their combination for the advancement of software quality. Testing and proving seem to be contradictory techniques: once you have proved your program to be correct then additional testing seems pointless; on the other hand, when such a proof in not feasible, then testing the program seems to be the only option. This view has dominated the research community since the dawn of computer science, and has resulted in distinct communities pursuing the seemingly orthogonal research areas. However, the development of both approaches has lead to the discovery of common issues and to the realization of potential synergy. Perhaps, use of model checking in testing was one of the first signs that a counterexample to a proof may be interpreted as a test case. Recent breakthroughs in deductive techniques such as satisfiability modulo theories, abstract interpretation, and interactive theorem proving, have paved the way for new and practically effective methods of powering testing techniques. Moreover, since formal, proof-based verification is costly, testing invariants and background theories can be helpful to detect errors early and to improve cost effectiveness. Summing up, in the past few years an increasing number of research efforts have encountered the need for combining proofs and tests, dropping earlier dogmatic views of incompatibility and taking instead the best of what each of these software engineering domains has to offer. The TAP conference aims to bring together researchers and practitioners working in the converging fields of testing and proving, and will offer a generous allocation of papers, panels and informal discussions. Topics of interest cover theory definitions, tool constructions and experimentations, and include (other topics related to TAP are welcome): - Bridging the gap between concrete and symbolic techniques, e.g. using proof search in satisfiability modulo theories solvers to enhance various testing techniques - Transfer of concepts from testing to proving (e.g., coverage criteria) and from proving to testing - Program proving with the aid of testing techniques - New problematics in automated reasoning emerging from specificities of test generation - Verification and testing techniques combining proofs and tests - Generation of test data, oracles, or preambles by deductive techniques such as: theorem proving, model checking, symbolic execution, constraint logic programming - Model-based testing and verification - Generation of specifications by deduction - Automatic bug finding - Debugging of programs combining static and dynamic analysis - Formal frameworks - Tool descriptions and experience reports - Case studies combining tests and proofs - Domain specific applications of testing and proving to new application domains such as validating security protocols, vulnerability detection of programs, security Important Dates: ================ Abstract submission: January 25, 2013 Paper submission: February 1, 2013 Notification: March 3, 2013 Camera ready version: April 5, 2013 TAP conference: June 17-21, 2013 Program Chairs: =============== Margus Veanes (Microsoft Research, USA) Luca Vigano` (University of Verona, Italy) Program Committee: ================== TBA Submission: =========== Please submit your papers via easychair https://www.easychair.org/conferences/?conf=tap2013 (submission page to be opened in due time) TAP 2013 will accept two types of papers: - Research papers: full papers with at most 16 pages in LNCS format (pdf), which have to be original, unpublished and not submitted elsewhere. - Short contributions: work in progress, (industrial) experience reports or tool demonstrations, position statements; an extended abstract with at most 6 pages in LNCS format (pdf) is expected. Subject to final approval by Springer, accepted papers will be published in the Springer LNCS series and will be available at the conference. The contents of previous TAP proceedings is available at: http://www.informatik.uni-trier.de/~ley/db/conf/tap/ -- Dr. Achim D. Brucker, SAP AG, SAP Research Vincenz-Priessnitz-Str. 1, D-76131 Karlsruhe, Phone: +49 6227 7-52595 http://www.brucker.ch

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[Off-topic] How unimportant it is whether submarines can swim (EWD1056)
by Henk-Jan van Tuyl 30 Oct '12

30 Oct '12

L.S., I thought you might be interested to know, that I have translated one of prof. Edsger W. Dijkstra's writings to English[0]. I will submit this translation to the E. W. Dijkstra Archive of the University of Texas[1]. Some of the highlights: - can submarines swim? - redefining mathematics - something unimaginably unimaginable - a baby faster than fighter jets Regards, Henk-Jan van Tuyl [0] http://members.chello.nl/hjgtuyl/computing/EWD1056.html [1] http://www.cs.utexas.edu/users/EWD/welcome.html -- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html Haskell programming --

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Teaching Haskell @ MOOCs like Coursera or Udacity
by niket 30 Oct '12

30 Oct '12

I am a novice in Haskell but I would love to see the gurus out here teaching Haskell on MOOCs like Coursera or Udacity. Dr Martin Odersky is doing it for Scala here: https://www.coursera.org/course/progfun I would love to see Haskell growing on such new platforms! Regards, Niket

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Segment Tree based Set
by Tony Morris 29 Oct '12

29 Oct '12

Hi, I was wondering if anyone knows of a package implementing a fast lookup for an element in ranges. For example, this operation: Ord a => a -> [(a, a)] -> Bool ...can be implemented: \a rs -> let s = Set.fromList rs in a `member` s This is not particularly efficient. A segment tree seems like a more appropriate data structure to store the ranges. Does such a library exist? -- Tony Morris http://tmorris.net/

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Empirically comparing strict vs. lazy evaluation
by Kristopher Micinski 29 Oct '12

29 Oct '12

Hello Haskellers! I wonder if you know of benchmarks that attempt to compare, empirically, lazy vs. eager evaluation. Pointers to papers and/or code would be most appreciated. Our group (at UMD) is working on a paper that develops some technology for lazy programs, and we would like to choose benchmarks for evaluating it that span the gamut of computations that perform well when done lazily, vs. those that do not perform as well when evaluated lazily. Then we want to look at the best case and worst case for our technology WRT laziness, and see how it stacks up. Thanks in advance for any ideas you have! Kris Micinski

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ICFP 2013: Call for workshops and co-located events
by David Van Horn 29 Oct '12

29 Oct '12

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2013 18th ACM SIGPLAN International Conference on Functional Programming September 22 - 28, 2013 Boston, Massachusetts, USA http://icfpconference.org/icfp2013/ The 18th ACM SIGPLAN International Conference on Functional Programming will be held in Boston, Massachusetts on September 22-28, 2013. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as tutorials) to be affiliated with ICFP 2013 and sponsored by SIGPLAN. These events should be more informal and focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered. The workshops are scheduled to occur on September 22-24 (the three days before ICFP) and September 28 (the day after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: December 7, 2012 Notification of acceptance: January 7, 2013 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2013 workshop co-chairs (Patrik Jansson and Sam Tobin-Hochstadt), via email to icfp13-workshops(a)ccs.neu.edu by December 7, 2012. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by January 7, 2013, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2013/icfp13-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://acm.org/sigplan/sigplan_workshop_proposal.htm ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2013 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Patrik Jansson (Chalmers University of Technology) Workshop Co-Chair: Sam Tobin-Hochstadt (Northeastern University) General Chair : Greg Morrisset (Harvard University) Program Chair: Tarmo Uustalu (Tallinn University of Technology) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Patrik Jansson and Sam Tobin-Hochstadt), via email to icfp13-workshops(a)ccs.neu.edu

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