December 2009 - Haskell

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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Nominations for the Haskell 2011 committee
by Simon Marlow 29 Dec '09

29 Dec '09

So that the Haskell 2011 cycle can get underway, we are soliciting nominations for new committee members. Since this is the first time we've done this, the procedure is still somewhat unsettled and things may yet change, but the current guidelines are written down here: http://hackage.haskell.org/trac/haskell-prime/wiki/Committee In particular, on the makeup of the commitee: The committee should represent each class of stakeholders with roughly equal weight. These classes are * Implementers (compiler/tool writers) * Commercial users * Non-commercial users (e.g. open source) * Academic users (using Haskell in research) * Teachers * Authors In addition, members of the committee should be long-standing users with a deep knowledge of Haskell, and preferably with experience of language design. The committee should contain at least some members with a comprehensive knowledge of the dark corners of the Haskell language design, who can offer perspective and rationale for existing choices and comment on the ramifications of making different choices. To nominate someone (which may be yourself), send a message to haskell-prime(a)haskell.org. Please give reasons for your nomination. The current committee will appoint new commitee members and editors starting in the new year, so the deadline for nominations is 31 December 2009. During discussion amongst the current commitee, we realised that the choice of committee should be informed not just by the criteria above, but also by the particular proposals that are expected to be under consideration during this cycle. With that in mind, we plan that following the nominations the current committee will choose a "core commitee" of up to 10 members, and further members may be appointed during the year based on expertise needed to consider particular proposals. Accordingly, now would be a good time to start discussing which proposals should be considered in the Haskell 2011 timeframe, as that may affect the choice of commitee members. More details on the current Haskell Prime process are here: http://hackage.haskell.org/trac/haskell-prime/wiki/Process Cheers, Simon

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ANN: vty-4.2.1.0
by Corey O'Connor 28 Dec '09

28 Dec '09

http://hackage.haskell.org/package/vty 4.2.1.0 * GHC 6.12.1 support * API changes: * Attr record accessor fore_color changed to attr_fore_color * Attr record accessor back_color changed to attr_back_color * Attr record accessor style changed to attr_style * Added an "inline" display attribute changing DSL: * put_attr_change applies a display attribute change immediately to a terminal * For instance, can be used to change the display attrbiutes of text output via putStrLn and putStr. EX: "put_attr_change $ back_color red" will set the background color to red. * Changes do not apply to a Picture output via output_picture. * See Graphics.Vty.Inline * Moved all IO actions into any monad an instance of MonadIO Short example of Graphics.Vty.Inline: import Graphics.Vty import Graphics.Vty.Inline main = do t <- terminal_handle putStr "Not styled. " put_attr_change t $ back_color red >> apply_style underline putStr " Styled! " put_attr_change t $ default_all putStrLn "Not styled." release_terminal t return () Cheers, Corey O'Connor

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ANN: stm-io-hooks-0.6.0
by Peter Robinson 27 Dec '09

27 Dec '09

A new announcement, as the interface has changed quite a bit (e.g. 'onRetry' is gone) and previous versions had a rare but annoying bug due to the unpredictability of 'unsafeIOToSTM'. >From the package description: ----- This library provides an STM monad with commit and retry IO hooks. A retry-action is run (at least once) if the transaction retries, while commit-actions are executed iff the transaction commits. The AdvSTM monad also gives some atomicity guarantees for commit-actions: * When a TVar is modified in a transaction and this transaction commits, the update remains invisible to other threads until the corresponding onCommit action is run. * If the onCommit action throws an exception, the original values of the modified TVars are restored. Note: This library was inspired by the AdvSTM monad on the Haskell Wiki (see http://haskell.org/haskellwiki/?title=New_monads/MonadAdvSTM) Feedback is welcome! -----

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ANNOUNCE: CPython / libpython bindings
by John Millikin 27 Dec '09

27 Dec '09

CPython, the primary implementation of the Python language, has a C API for embedding Python into applications and writing extension modules[1]. The cpython[2] package is a binding to this API. It's not a complete binding yet -- there's a couple areas where I haven't figured out how to represent the C-ish idioms -- so it's not yet possible to do things like implement extension modules[3], run code directly from a file[4], or compile Python strings to code[4]. Hackage can't build docs because it doesn't have the Python development libraries installed, so I've uploaded them to <http://ianen.org/haskell/bindings/cpython/api-documentation/>. If you encounter any build errors, or have wishes / ideas on which parts of the API to add to the binding, please say so. I will add parts as I figure them out, but wanted to get a working version out ASAP so people can play with it. [1] http://docs.python.org/3.1/c-api/ [2] http://hackage.haskell.org/package/cpython/ [3] http://docs.python.org/3.1/c-api/module.html#initializing-c-modules [4] http://docs.python.org/3.1/c-api/veryhigh.html

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ANNOUNCE: graphviz-2999.8.0.0
by Ivan Lazar Miljenovic 26 Dec '09

26 Dec '09

I am pleased to announce the latest release of my graphviz [1] library, which provides bindings and helper functions for use with the Graphviz [2] suite of graph visualisation programs. [1] http://hackage.haskell.org/package/graphviz [2] http://www.graphviz.org/ For the most part, this release has a compatible API with the 2999.7.0.0 version; the only exceptions to this are the runGraphviz and runGraphvizCommand functions in Data.GraphViz.Commands; I released after the last release that it might be useful to have these return the filenames of the files created rather than just indicating success, especially when using addExtension (from the same module) to add the correct extension to a provided filename. The rest of the changes to this release are: * Added support for generalised DotGraphs; this optional representation removes the restriction of ordering of Dot statements. This allows for greater flexibility of how to specify Dot code. As an offshoot from this, most relevant functions now utilise a new DotRepr class that work with both DotGraphs and the new GDotGraphs; this shouldn't affect any code already in use. * With the prompting of Noam Lewis, the augmentation functions have been revamped in two ways: - Now contains support for multiple edges. - The ability to perform "manual" augmentation if greater control is desired. * Add a preview function to quickly render and visualise an FGL graph using the Xlib canvas. * Added a pseudo-inverse of the FGL -> Dot functions (a graph is created, but the original node and edge labels are unrecoverable). * The Printing and Parsing modules have been moved (from Data.GraphViz.Types to Data.GraphViz). In the near future, this library is also likely to contain support for record shapes for graph nodes thanks to Minh Thu. If you want/require any additional features in graphviz, you too can do what countless (well, OK, not actually countless per-se) people like Noam and Thu have done: bug me to do it or send me a patch! ;-) (I hope that I don't have to make yet another release soon fixing an obvious flaw as soon as I actually start using this release myself...) -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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ANNOUNCE: hecc-0.2
by Marcel Fourné 25 Dec '09

25 Dec '09

Hi again, this is the second release of hecc, the Elliptic Curve Cryptography Library for Haskell, to be found at http://hackage.haskell.org/package/hecc There are only some smaller changes since the first release **3... * license change to the more common BSD3 * proper benchmarking * speed improvements * timing-attack resistant default point multiplication * simple key generation (given a generator on the curve used) En Detail: There are now 2 algorithms for point multiplication, the classic double-and-add (dnadd) and a montgomery ladder(montgladder). Dnadd varies in speed between 200us (degenerate case: long rows of zeroes) and 4.6ms while montgomery ladder (almost, see **1) always takes its 4.6ms. **2 Notes: **1 except when multiplying by binary numbers with trailing long rows of zeroes (e.g. 2^254), in which case it also takes 200us (cache?... anybody got more ideas how to fix this?) **2 Test HW: 2.4Ghz Core2, accompanying src/bench.hs, projective coordinates used **3 (due to an annoyingly complicated fracture of my main hand) This library still uses plain Haskell, in case anybody wants to ask... ;-) Still considered alpha, so beware of dragons! Almost enjoying holidays, welcoming feedback, Marcel -- Marcel Fourné OpenPGP-Key-ID: 0x74545C72 A good library is preferable to a tool, except when you just need that one tool.

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ghc-6.12.1 binary package for OpenSolaris b129
by Michael Lee 23 Dec '09

23 Dec '09

If anyone is interested in a binary package of ghc-6.12.1 for OpenSolaris, one can find said package at http://code.google.com/p/opensolaris-lang/. Please let me know how it works out for you. Thanks, -m

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Final Call for Participation: TLDI'10
by Andrew Kennedy 22 Dec '09

22 Dec '09

********************************************************************* FINAL CALL FOR PARTICIPATION TLDI 2010 ACM SIGPLAN Workshop on Types in Language Design and Implementation 23 January 2010 Madrid, Spain To be held in conjunction with POPL 2010 http://research.microsoft.com/~akenn/tldi2010/ ********************************************************************* IMPORTANT DATES Early registration deadline for POPL: December 22, 2009 (TODAY!) Hotel reservation deadline: December 28, 2009 (Monday) VENUE TLDI'10 and all POPL'10 affiliated events will take place at the Melia Castilla Hotel, Madrid. REGISTRATION To register for TLDI'10, follow the link from the POPL 2010 page, at http://www.cse.psu.edu/popl/10/ SCOPE The role of types and proofs in all aspects of language design, compiler construction, and software development has expanded greatly in recent years. Type systems, type-based analyses and type-theoretic deductive systems have been central to advances in compilation techniques for modern programming languages, verification of safety and security properties of programs, program transformation and optimization, and many other areas. The ACM SIGPLAN Workshop on Types in Language Design and Implementation brings researchers together to share new ideas and results concerning all aspects of types and programming, and is now an annual event. INVITED SPEAKER Matthias Felleisen, Northeastern University, Boston PRELIMINARY PROGRAM ---------------------- Opening remarks: 9:20-9:30 Invited talk 9:30-10:30 *** Adding Types to Untyped Languages Matthias Felleisen, Northeastern University, Boston ---------------------- ** Session I 11:00-12:30 *** Effects for Cooperable and Serializable Threads Jaeheon Yi and Cormac Flanagan *** Race-free and Memory-safe Multithreading: Design and Implementation in Cyclone Prodromos Gerakios, Nikolaos Papaspyrou and Konstantinos Sagonas *** Distributed programming with distributed authorization Kumar Avijit, Anupam Datta and Robert Harper ---------------------- ** Session II 2:30-4:00 *** let should not be generalized Dimitrios Vytiniotis, Simon Peyton Jones and Tom Schrijvers *** Pointwise Generalized Algebraic Data Types Chuan-kai Lin and Tim Sheard *** Verifying Event-Driven Programs using Ramified Frame Properties Neelakantan Krishnaswami, Lars Birkedal and Jonathan Aldrich ---------------------- ** Session III 4:30-5:30 *** Lightweight Linear Types in System F^o Karl Mazurak, Jianzhou Zhao and Steve Zdancewic *** F-ing Modules Andreas Rossberg, Claudio Russo and Derek Dreyer ---------------------- GENERAL CHAIR Andrew Kennedy, Microsoft Research, Cambridge PROGRAM CHAIR Nick Benton, Microsoft Research, Cambridge PROGRAM COMMITTEE Gilles Barthe, IMDEA Software, Spain Viviana Bono, University of Torino, Italy Giorgio Ghelli, University of Pisa, Italy Dan Grossman, University of Washington, USA Atsushi Igarashi, Kyoto University, Japan Conor McBride, University of Strathclyde, UK Jeremy Siek, University of Colorado at Boulder, USA Zhong Shao, Yale University, USA Matthieu Sozeau, Harvard University, USA Chris Stone, Harvey Mudd College, USA Kristian Støvring, ITU Copenhagen, Denmark

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Haskell Web News: Looking back on 2009
by Don Stewart 21 Dec '09

21 Dec '09

The Haskell Web News is a monthly summary of the hottest news about the Haskell programming language, as found in our online communities. If you want to catch up with what’s been happening in Haskell, this might be the journal for you. In this edition, we look back on the major events of 2009. http://haskellwebnews.wordpress.com/2009/12/20/the-year-in-haskell/ -- Don

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