November 2009 - Haskell-Cafe

Parsing Haskell
by Eric Macaulay 07 Nov '09

07 Nov '09

Hi all, I was hoping to use Language.Haskell.Parser to parse fragments of Haskell code. However, it appears that one can only use this module to parse complete Haskell programs. Is there anyway around this, or must I write a Haskell parser from scratch? Eric M.

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Re: [Haskell-cafe] Re: Parsing Haskell
by Eric Macaulay 07 Nov '09

07 Nov '09

It has indeed reached me. Thanks! At 16:23 06/11/2009, Niklas Broberg wrote: > > You'd have to modify the parser in haskell-src(-exts) to do add the entry > > points, though. > >Actually haskell-src-exts already defines entry points for Module, >Stmt, Exp, Pat and Type (as well as [Module] in 1.3.x). > >Not sure if this message reaches the original poster though. > >Cheers, > >/Niklas >_______________________________________________ >Haskell-Cafe mailing list >Haskell-Cafe(a)haskell.org >http://www.haskell.org/mailman/listinfo/haskell-cafe

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Haskell Weekly News: Issue 138 - November 07, 2009
by jfredett＠gmail.com 07 Nov '09

07 Nov '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20091107 Issue 138 - November 07, 2009 --------------------------------------------------------------------------- Welcome to issue 138 of HWN, a newsletter covering developments in the [1]Haskell community. Lots of discussion about [2]Clean this week. As well there was a new DSL, feldspar, announced. It deals with digital signal processing applications. Announcements MonadRandom-0.1.4. Brent Yorgey [3]announced a new version of MonadRandom which adds applicative instances for Rand and RantT, so you can write your code in applicative style. Criterion 0.2, an improved Haskell benchmarking library. Bryan O'Sullivan [4]announced a new version of Criterion, all the details of this release are available on his [5]blog feldspar-language. Emil Axelsson [6]announced feldspar, a DSL for digital signal processing. feldspar-compiler. Emil Axelsson [7]announced the C code backend for the `feldspar` language. fdo-notify 0.1, a client for the Desktop Notifications protocol. Max Rabkin [8]announced a library for FreeDesktop.org's Desktop Notifications Protocol. language-python version 0.2 now available. Bernie Pope [9]announced a new version of the language-python package, which provides an AST and parser for Python 2.x-3.x (previously, only 3.x was supported). timeplot. Eugene Kirpichov [10]announced timeplot, which is useful visualizing log files. Singapore FP Users Group First Meeting. Max Cantor [11]announced the first meeting of the Singapore FP Users Group, it will be Monday, November 2nd at 6pm. Advgame 0.1.1. Tim Wawrzynczak [12]announced his port of Conrad Barski's 'Casting SPELs in Lisp' to Haskell. BlogLiterately-0.2. Robert Greayer [13]announced version 0.2 of BlogLiterately, a simple tool for uploading posts written in markdown and Literate Haskell to blogs. haskell-mode 2.6. Svein Ove Aas [14]announced a bugfix release of the Emac's Haskell mode. Discussion A Problem Defining a Monad instance. Petr Pudlak [15]asked about how to defined an instance of the Monad class for a monad whose argument is restricted by another typeclass. Point Free Case Expressions. Sebastiaan Visser [16]suggested that a new syntax be added for 'point-free' case expressions. Master's thesis topic sought. Matus Tejiscak [17]asked for suggestions for possible Master's Thesis topics. What's the deal with Clean? Deniz Dogan [18]asked about the recent discussion on the -cafe list about Clean, another Pure, Lazy, Strictly Typed language. Blog noise [19]Haskell news from the [20]blogosphere. Blog posts from people new to the Haskell community are marked with >>>, be sure to welcome them! * Neil Brown: [21]Text.Printf and monad transformers. * Bryan O'Sullivan: [22]Criterion 0.2, an improved Haskell benchmarking library. * Galois, Inc: [23]Tech Talk: Hoare-Logic â fiddly details and small print. * Gtk2HS: [24]Writing concurrent programs.. * Tom Schrijvers: [25]Postdoc/PhD Positions on the Monadic Constraint Programming project. * Darcs: [26]darcs weekly news #45. * Tom Schrijvers: [27]Haskell Type Constraints unleashed. * Luke Plant: [28]Building GHC is fun.... * Manuel M T Chakravarty: [29]Status Update of the Glasgow Haskell Compiler, October 2009. * Chris Smith: [30]Monads from Two Perspectives. * Neil Brown: [31]Concurrent Testing and Tracing: Useful Output for Test Failures. * Dan Piponi (sigfpe): [32]Buffon's Needle, the Easy Way. Buffon's needle is a popular probability problem. Rule lines on the floor a distance d apart and toss a needle of length l Quotes of the Week * blackdog: [About Hubris] I tell the Ruby guys that Haskell will help them speed up their Ruby code and keep their apps going, and I tell Haskell guys that it'll Trojan Horse those poor unsuspecting rubyists... * lispy: Great, I leave the channel for a few hours and suddenly Haskell has a new found work ethic. * roconnor: ivanm: I will keep the fail in the code * lament: just remember to ask, 'What are your questions', as opposed to 'Do you have any questions' * mauke: @unpl const (flip const) lambdabot: (\ _ c d -> d) About the Haskell Weekly News New editions are posted to [33]the Haskell mailing list as well as to [34]the Haskell Sequence and [35]Planet Haskell. [36]RSS is also available, and headlines appear on [37]haskell.org. To help create new editions of this newsletter, please see the information on [38]how to contribute. Send stories to jfredett . at . gmail . dot . com. The darcs repository is available at darcs get [39]http://patch-tag.com/r/jfredett/HWN2/pullrepo HWN2 . References 1. http://haskell.org/ 2. http://en.wikipedia.org/wiki/Clean_(programming_language) 3. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65844 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65813 5. http://www.serpentine.com/blog/2009/11/06/criterion-0-2-an-improved-haskell… 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65617 7. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65741 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65686 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65656 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65575 11. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65471 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65462 13. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65567 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/65487 15. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/65834 16. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/65750 17. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/65706 18. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/65589 19. http://planet.haskell.org/ 20. http://haskell.org/haskellwiki/Blog_articles 21. http://chplib.wordpress.com/2009/11/06/text-printf-and-monad-transformers/ 22. http://www.serpentine.com/blog/2009/11/06/criterion-0-2-an-improved-haskell… 23. http://www.galois.com/blog/2009/11/04/chapman-hoare/ 24. http://haskell.org/gtk2hs/archives/2009/11/04/writing-concurrent-programs/ 25. http://tomschrijvers.blogspot.com/2009/11/postdocphd-positions-on-monadic.h… 26. http://blog.darcs.net/2009/11/darcs-weekly-news-45.html 27. http://tomschrijvers.blogspot.com/2009/11/haskell-type-constraints-unleashe… 28. http://lukeplant.me.uk/blog.php?id=1107301703 29. http://justtesting.org/post/232566357 30. http://cdsmith.wordpress.com/2009/11/02/monads-from-two-perspectives/ 31. http://chplib.wordpress.com/2009/11/02/concurrent-testing-and-tracing-usefu… 32. http://blog.sigfpe.com/2009/10/buffons-needle-easy-way.html 33. http://www.haskell.org/mailman/listinfo/haskell 34. http://sequence.complete.org/ 35. http://planet.haskell.org/ 36. http://sequence.complete.org/node/feed 37. http://haskell.org/ 38. http://haskell.org/haskellwiki/HWN 39. http://patch-tag.com/r/jfredett/HWN2/pullrepo%20HWN2

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[Haskell-beginners] Re: Is Haskell for me?
by Felipe Lessa 07 Nov '09

07 Nov '09

Sorry for not sending to the list. ----- Forwarded message from Felipe Lessa <felipe.lessa(a)gmail.com> ----- On Fri, Nov 06, 2009 at 07:58:30PM -0200, Felipe Lessa wrote: > On 11/6/09, Gaius Hammond <gaius(a)gaius.org.uk> wrote: > > To be fair, Python offloads its heavy lifting to C libraries - NumPy > > and SciPy run at very close to full C speed on large datasets. This is > > also how Matlab works. Unladen Swallow is an upcoming JIT compiler for > > Python. > > > > Where Haskell shines for computation is when you can leverage lazy > > evaluation. > > *If* you can offload most of your work to SciPy. Depending on what you > do this is at least difficult. I don't know how much of a neural > network can be represented as big fat matrix :). I would also like to add that Haskell shines for parallel computation, being easy and rewarding to use multiple cores or processors in a SMP machine. Parallel computing in Python is at least ugly because you need to use multiple processes, while the same task in C++ needs to be dealt with manually using concurrency. -- Felipe. ----- End forwarded message -----

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What's the new type ?
by zaxis 06 Nov '09

06 Nov '09

type Parser a = GenParser Char () a newtype GenParser tok st a = Parser (State tok st -> Consumed (Reply tok st a)) As i know, the Parser type is just an alias of GenParser. Then can the second line be replaced as below? newtype GenParser tok st a = GenParser Char () (State tok st -> Consumed (Reply tok st a)) If it can , then what is the new type ? Sincerely! ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/What%27s-the-new-type---tp26208600p26208600.html Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Is () a 0-length tuple?
by Pasqualino "Titto" Assini 06 Nov '09

06 Nov '09

Hi, I just noticed that the json library maps () to a JSON empty array: []. This makes sense if () is a 0-length tuple, the (2,"hi") tuple for example maps to [2,"hi"] But is it so in Haskell? In what sense () is a 0-length tuple? Thanks, titto

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ANN: MonadRandom-0.1.4
by Brent Yorgey 06 Nov '09

06 Nov '09

Just a quick note: I've uploaded a new version of the MonadRandom which adds Applicative instances for Rand and RandT. Now you can write your random code in an applicative style! -Brent

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ANNOUNCE: NetSNMP-0.1.6
by John Dorsey 06 Nov '09

06 Nov '09

I'm pleased to annonce the release of NetSNMP-0.1.6, a partial (but useful) binding to the net-snmp library.[1] NetSNMP is a simple and self-contained client interface for doing basic SNMP GET, NEXT, and WALK operations. As far as I know it should work with any version of the C library (net-snmp) from version 5. This release improves threaded performance, and the management of foreign memory objects. I've been using it successfully in a threaded polling daemon which I'm running on 32-bit and 64-bit Linux systems. If you try out NetSNMP, or if you decide it doesn't meet your need, please drop me a line! Regards, John Dorsey

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Fwd: [Haskell-cafe] What's the deal with Clean?
by Tracy Wadleigh 06 Nov '09

06 Nov '09

> I had to implement a ring buffer, and I wanted the code using it to be > written in Haskell. I ended up implementing the buffer in C, and wrapping > it in FFI from Haskell because implementing a destructive array in Haskell > is kind of unwieldy to someone of my experience level. In Clean, it looks > like the uniqueness typing allows for destructive updates in a very > controlled manner. > The ST monad provides this functionality. The never-instantiated-in-a-visible-way state parameter of the ST monad provides the "uniqueness" required for doing destructive updates in a pure way.

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Memory Leak - Artificial Neural Network
by Shelby Moore 06 Nov '09

06 Nov '09

wren ng thornton wrote: http://www.haskell.org/pipermail/haskell-cafe/2009-November/068728.html >...use matrices/arrays rather than lists... >...even just using an unboxed array for the matrices > will make it much faster to traverse through... Matrix multiplication is the sequential order inner or outer product of the columns/rows of one matrix and rows/columns of 2nd matrix: http://en.wikipedia.org/wiki/Matrix_multiplication#Relationship_with_the_in… Afaics, optimize matrix multiplication with lists. Random arrays incurs a huge performance penality in Haskell, unless you revert to non-lazy implementation, in which case you have voided multi-core speed ups for very large arrays (aren't ANNs huge matrices?).

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