March 2009 - Haskell - Haskell.org

ACCOUNCE: storable 0.1 -- Storable type class for variable-sized data
by Tomáš Janoušek 05 Mar '09

05 Mar '09

I am pleased to announce that the first release of the storable library has been uploaded to Hackage. Let me describe it in a few sentences (copied from its haddock comments): This class fills the gap between Foreign.Storable and Data.Binary. It adds support for marshalling (finite) values of variable-sized data types, like lists or trees, while preserving the performance and memory efficiency one expects from the Storable class. It also provides a (monadic) syntactic sugar that takes care of alignment restrictions by itself and makes instance deriving easy. The performance goal has not been achieved yet, of course. We are using this class to serialize values of a data type representing vertices in a Haskell-generated graph for a model checker called DiVinE (C++). http://hackage.haskell.org/cgi-bin/hackage-scripts/package/storable -- Tomáš Janoušek, a.k.a. Liskni_si, http://work.lisk.in/

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ANN: pandoc 1.2
by John MacFarlane 05 Mar '09

05 Mar '09

I'm pleased to announce the release of pandoc version 1.2 (uploaded today to HackageDB). The most significant new feature is support for literate Haskell. You can now use pandoc directly on literate Haskell source files to produce syntax-highlighted HTML output: pandoc -s MyProg.lhs > MyProg.html Pandoc will interpret text sections as (extended) markdown. If you prefer to write literate Haskell using reStructuredText or LaTeX, pandoc supports that too: pandoc -s --from rst+lhs MyProg.lhs > MyProg.html pandoc -s --from latex+lhs MyProg.lhs > MyProg.html You can even convert from one style to another: pandoc -s --from markdown+lhs --to latex+lhs MyProg.hs This release also adds an '--email-obfuscation' option, so the user can select an email obfuscation method (or disable obfuscation), and support for citations using the latest version of Andrea Rossato's citeproc-hs. In addition, many bugs have been fixed. Thanks to everyone who filed bug reports. John

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ANN: Happstack 0.2 Released
by Matthew Elder 04 Mar '09

04 Mar '09

Happstack 0.2 has been released; it is available on Hackage. A lot of community effort has gone into it! For details, please see this post: http://blog.happstack.com/2009/03/04/happstack-02-released Regards, Matthew Elder -- Need somewhere to put your code? http://patch-tag.com Want to build a webapp? http://happstack.com

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ANNOUNCE: Extensible and Modular Generics for the Masses: emgm-0.3
by Sean Leather 03 Mar '09

03 Mar '09

============================================== Extensible and Modular Generics for the Masses ============================================== Extensible and Modular Generics for the Masses (EMGM) is a library for generic programming in Haskell using type classes and a sum-of-products view. ------- Updates ------- emgm-0.3 is the third major release, and it arrives a little over a month after emgm-0.2. Deriving is now greatly improved! Due to recent reports from users, we realized the current implementation just wasn't going to cut it. EMGM already supports a wide range of datatypes, so why not make the deriving code support just as many. Hopefully, it works well for you. Please let us know if your datatype is not supported. There are several new functions in the EMGM family. These include: cast (a type-safe, configurable, generic cast) and everywhere and everywhere' (functions similar to those of the same name in SYB that apply a transformation everywhere a certain type is found). ------- Changes ------- Changes from emgm-0.2 include: * Improved deriving can now handle datatype collections like this one: http://www.haskell.org/pipermail/generics/2009-February/000429.html * cast function > cast :: Rep (Map a) b => a -> b * everywhere and everywhere' > everywhere :: Rep (Everywhere a) b => (a -> a) -> b -> b > everywhere' :: Rep (Everywhere' a) b => (a -> a) -> b -> b They both perform transformations on a-values in a b-value. The former does them bottom-up, the latter top-down. The names come from similar functions in SYB that use rank-2 types. Note the difference. > everywhere :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a > everywhere' :: (forall a. Data a => a -> a) -> forall a. Data a => a -> a ------------ Known Issues ------------ Due to a problem with the template-haskell package and Cabal, you cannot cabal-install the emgm package with GHC 6.8. However, take heart! EMGM works very well with GHC 6.8. You merely have to download the tar.gz package from Hackage yourself, build it, and install it. Since it doesn't require any dependencies beyond what comes with GHC, installation is a breeze! ------------------- General Information ------------------- Visit the home page: http://www.cs.uu.nl/wiki/GenericProgramming/EMGM ---------------- General Features ---------------- The primary features of EMGM include: * Datatype-generic programming using sum-of-product views * Large collection of ready-to-use generic functions * Included support for standard datatypes: lists, Maybe, tuples * Easy to add support for new datatypes * Type classes make writing new functions straightforward in a structurally inductive style * Generic functions are extensible with ad-hoc cases for arbitrary datatypes * Good performance of generic functions The features of this distribution include: * The API is thoroughly documented with Haddock * Fully tested with QuickCheck and HUnit * Program coverage ensures that all useful code has been touched by tests * Tested on both Mac and Windows systems ------------ Requirements ------------ EMGM has the following requirements: * GHC 6.8.1 - It has been tested with versions 6.8.3 and 6.10.1 * Cabal library 1.2.1 - It has been tested with versions 1.2.4.0 and 1.6.0.1. ----------------- Download & Source ----------------- Use caball-install: cabal install emgm Get the package: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/emgm Check out the current source with Subversion: svn checkout https://svn.cs.uu.nl:12443/repos/dgp-haskell/EMGM/trunk Or view it online: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/ -------- Examples -------- Check out the examples: https://svn.cs.uu.nl:12443/viewvc/dgp-haskell/EMGM/trunk/examples/ -------------- Bugs & Support -------------- Report issues or request features: http://code.google.com/p/emgm/issues/list Discuss EMGM with the authors, maintainers, and other interested persons: http://www.haskell.org/mailman/listinfo/generics ------- Credits ------- The research for EMGM originated with Ralf Hinze. It was extended with work by Bruno Oliveira and Andres Löh. More details of the library functionality were explored by Alexey Rodriguez. We are very grateful to all of these people for the foundation on which this library was built. The current authors and maintainers of EMGM are: * Sean Leather * José Pedro Magalhães * Alexey Rodriguez * Andres Löh

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CFP: Submit a talk proposal to CUFP
by Kathleen Fisher 02 Mar '09

02 Mar '09

Hi all, This year CUFP will be held in Edinburgh, Scotland on 4 September. Bryan O'Sullivan, co-author of Real World Haskell, will deliver the keynote presentation, but we're now seeking proposals for regular presentations to complete the program. As you know, CUFP is the place to go to discuss real-world applications of functional programming and to meet the people involved. If you've got something interesting to say, please consider proposing a presentation. The complete call for presentations is below. Kind regards Kathleen Fisher (CUFP 2009 program committee member) Commercial Users of Functional Programming Workshop (CUFP) 2009 Functional Programming As a Means, Not an End Call for Presentations Sponsored by SIGPLAN Co-located with ICFP 2009 Edinburgh, Scotland, 4 September 2009 __________________________________________________________ Presentation proposals due 15 May 2009 http://cufp.galois.com/2009/call.html __________________________________________________________ Functional languages have been under academic development for over 25 years, and remain fertile ground for programming language research. Recently, however, developers in industrial, governmental, and open-source projects have begun to use functional programming successfully in practical applications. In these settings, functional programming has often provided dramatic leverage, including whole new ways of thinking about the original problem. The goal of the CUFP workshop is to act as a voice for these users of functional programming. The workshop supports the increasing viability of functional programming in the commercial, governmental, and open-source space by providing a forum for professionals to share their experiences and ideas, whether those ideas are related to business, management, or engineering. The workshop is also designed to enable the formation and reinforcement of relationships that further the commercial use of functional programming. Providing user feedback to language designers and implementors is not a primary goal of the workshop, though it will be welcome if it occurs. Speaking at CUFP If you use functional programming as a means, rather than as an end, we invite you to offer to give a talk at the workshop. Alternatively, if you know someone who would give a good talk, please nominate them! Talks are typically 25 minutes long, but can be shorter. They aim to inform participants about how functional programming played out in real-world applications, focusing especially on the re-usable lessons learned, or insights gained. Your talk does not need to be highly technical; for this audience, reflections on the commercial, management, or software engineering aspects are, if anything, more important. You do not need to submit a paper! If you are interested in offering a talk, or nominating someone to do so, send an e-mail to francesco(at)erlang-consulting(dot)com or jim(dot)d(dot)grundy(at)intel(dot)com by 15 May 2009 with a short description of what you'd like to talk about or what you think your nominee should give a talk about. Such descriptions should be about one page long. Program Plans CUFP 2009 will last a full day and feature a keynote presentation from Bryan O'Sullivan, co-author of Real World Haskell. The program will also include a mix of presentations and discussion sessions. Topics will range over a wide area, including: * Case studies of successful and unsuccessful uses of functional programming; * Business opportunities and risks from using functional languages; * Enablers for functional language use in a commercial setting; * Barriers to the adoption of functional languages, and * Mitigation strategies for overcoming limitations of functional programming. There will be no published proceedings, as the meeting is intended to be more a discussion forum than a technical interchange. This will be the sixth CUFP, for more information - including reports from attendees of previous events and video of recent talks - see the workshop web site: http://cufp.galois.com/ __________________________________________________

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ANNOUNCE: The Industrial Haskell Group
by Duncan Coutts 02 Mar '09

02 Mar '09

We are pleased to announce the creation of the Industrial Haskell Group (IHG). The IHG is an organisation to support the needs of commercial users of the Haskell programming language. For more information, please see http://industry.haskell.org/ Currently, the main activity of the IHG is a collaborative development scheme, in which multiple companies fund work on the Haskell development platform to their mutual benefit. The scheme has started with three partners of the IHG, including Galois and Amgen. More details are available at http://industry.haskell.org/collab If your company is interested in joining then please e-mail info(a)industry.haskell.org -- Duncan Coutts, Haskell Consultant Well-Typed LLP, http://www.well-typed.com/

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Take a break: write an essay for Onward! Essays
by Simon Peyton-Jones 01 Mar '09

01 Mar '09

Friends Writing papers is fun, we mostly only get to write one *kind* of paper. Here is an opportunity to write something in a totally different style: Submit an essay to Onward! Essays Deadline: 20 April 2009 http://onward-conference.org/calls/foressays An Onward! essay is a thoughtful reflection upon software-related technology. Its goal is to help the reader to share a new insight, engage with an argument, or wrestle with a dilemma. A successful essay is a clear and compelling piece of writing that explores a topic important to the software community. The subject area should be interpreted broadly, including the relationship of software to human endeavours, or its philosophical, sociological, psychological, historical, or anthropological underpinnings. An essay can be an exploration of its topic, its impact, or the circumstances of its creation; it can present a personal view of what is, explore a terrain, or lead the reader in an act of discovery; it can be a philosophical digression or a deep analysis. It can describe a personal journey, perhaps that by which the author reached an understanding of such a topic. I'm the program chair, and I'd love to get submissions from the POPL/ICFP/types community. Reflections on programming languages, types, testing, verification, software engineering, compilers, society, ... you name it. Anything to do with software. NB: Onward! is co-located with OOPSLA, but they are otherwise unrelated. OO is fine, but not required. Don't forget: 20th April. Simon PS: To get your imagination going, here are a couple of (strongly-contrasting) past essays: * Dan Grossman "The transactional memory / garbage collection analogy" http://www.cs.washington.edu/homes/djg/papers/analogy_oopsla07.pdf * Dick Gabriel "Designed as designer" http://dreamsongs.org/DesignedAsDesigner.html

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major speed improvement: regex-tdfa reaches 1.0.0
by ChrisK 01 Mar '09

01 Mar '09

Announcing the version 1.0.0 release of regex-tdfa. I am proud of this release. This is not just a bug fix release. It is a serious improvement in the asymptotic running time. The previous versions allowed bad combinations of pattern and searched text length to scale badly in the length of the text. Previously the worst case for text of length N was O(N^3). The new worst case asymptotic runtime scaled as O(N). There is never any backtracking. And the worst case storage space is independent of N. The package is on hackage at http://hackage.haskell.org/cgi-bin/hackage-scripts/package/regex-tdfa The darcs repository is at http://darcs.haskell.org/packages/regex-unstable/regex-tdfa/ All non-overlapping matches are found and returned, along with all captured (parenthesized) subexpressions. The result is precisely what Posix extended regular expressions are supposed to return. To be concrete, consider example text with length of N of (2^n)+2: > longInput = replicate (2^n) 'a' ++ "bc" And define 4 worst-case-scenario patterns. I wrote the code and I know how to kill it: > wcs0 = "a*b" > wcs1 = "a*c" > wcs2 = "(a|aa)*b" > wcs3 = "(a|aa)*c" wcs0 is easy. wcs1 causes the old code to backtrack. wcs2 causes the old code's storage to scale as O(N). wcs3 causes both backtracking and O(N) storage with the old code. The old code's time scales as O(N) for wcs0, O(N^2) for wcs1 and wcs2, and O(N^3) for wcs3. The new code is always O(N). The actual timings for the old code on my G4 laptop for wcs on 2^8 and 2^9 and 2^10 are: Reason:compare-tdfa chrisk$ time ./Test-TDFA-np wcs3 8 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA-np wcs3 8 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(257,1)),(1,(-1,0))]] 263,776,756 bytes allocated in the heap user 0m1.017s sys 0m0.058s Reason:compare-tdfa chrisk$ time ./Test-TDFA-np wcs3 9 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA-np wcs3 9 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(513,1)),(1,(-1,0))]] 1,998,647,452 bytes allocated in the heap user 0m7.083s sys 0m0.289s Reason:compare-tdfa chrisk$ time ./Test-TDFA-np wcs3 10 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA-np wcs3 10 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(1025,1)),(1,(-1,0))]] 15,653,277,200 bytes allocated in the heap user 0m53.350s sys 0m2.056s The doubling of length is causing a nearly eight-fold time increase. The heap allocation is also increasing nearly eight-fold. The new code with the same input pattern and texts gives: Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 wcs3 8 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA2-0.99.19-np2 wcs3 8 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(257,1)),(1,(-1,0))]] 2,135,324 bytes allocated in the heap user 0m0.017s sys 0m0.017s Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 wcs3 9 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA2-0.99.19-np2 wcs3 9 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(513,1)),(1,(-1,0))]] 3,588,656 bytes allocated in the heap user 0m0.024s sys 0m0.017s Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 wcs3 10 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA2-0.99.19-np2 wcs3 10 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(1025,1)),(1,(-1,0))]] 6,345,436 bytes allocated in the heap user 0m0.038s sys 0m0.018s Note that the heap allocation for the 1026 character example above is 2466 times less than the old code. That was too fast to prove the scaling, so take more input: Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 wcs3 20 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA2-0.99.19-np2 wcs3 20 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(1048577,1)),(1,(-1,0))]] 5,708,574,848 bytes allocated in the heap user 0m26.023s sys 0m0.985s Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 wcs3 21 +RTS -sstderr 2>&1 | head -4 ./Test-TDFA2-0.99.19-np2 wcs3 21 +RTS -sstderr Test for [Char] Right [array (0,1) [(0,(2097153,1)),(1,(-1,0))]] 11,416,354,056 bytes allocated in the heap user 0m52.656s sys 0m1.985s The length and time both doubled, as did the heap allocation. And the new code has searched two million characters in the time the old code searched one thousand. How about away from the worst case scenario? On the testing suite the new code is running slightly slower: Reason:compare-tdfa chrisk$ time ./Test-TDFA-np -r 1 100 > /dev/null user 0m4.841s sys 0m3.019s Reason:compare-tdfa chrisk$ time ./Test-TDFA2-0.99.19-np2 -r 1 100 > /dev/null user 0m5.970s sys 0m3.012s So that is an increase of execution time of 14%. This small dip in performance might be reclaimable with more optimization. I think the gain in worst case performance already offsets the slight cost. The code for String is complete. The strict and lazy bytestrings and the (Seq Char) are currently using the String code for matching. This will be improved in a future release. Cheers, Chris The small print: regex-tdfa will still behave badly in space and time if given a pathological pattern, e.g. "(((a|aa){0,100}){0,100}){0,100}". But, I am hopeful than I can improve regex-tdfa to behave well with the patterns like this one. That is my vague goal for a future version 2.0.0 release. The very small print: I have been using ghc-6.10.1, and I think I have carried over cabal switches to make ghc-6.8.3 also work. The library probably can work with ghc-6.6, but the cabal file will need editing first as well as fixes to "Text.Regex.TDFA.NewDFA.copySTU".

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haskell documentation
by ppk＠cse.iitk.ac.in 01 Mar '09

01 Mar '09

Hi, I am a Arch linux + GHC user. I found it difficult to download documentations for GHC and all the modules. The GHC site does not seem to have a single tar.gz file by which one could down load the entire documentation tree. Same problem for modules build via yaourt. Of course one could build it directly from the appropriate cabal package but is there an automatic way via pacman/yaourt for example ? Regards ppk

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Announcement: A Haskell binding for the Augeas API
by Jude 01 Mar '09

01 Mar '09

All, I've published a Haskell FFI binding for the Augeas configuration editing API on Hackage. Please let me know if you find any problems with anything. Cheers, Jude Links ===== Hackage http://hackage.haskell.org/cgi-bin/hackage-scripts/package/augeas Source: http://code.haskell.org/augeas/ Bugs: http://trac.haskell.org/augeas/ <http://hackage.haskell.org/trac/c2hs/>

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