September 2010 - Haskell-Cafe

Did anyone manage to build glade hackage-package on Windows
by Daniel Kahlenberg 08 Sep '10

08 Sep '10

Hi list again, if there is anyone who managed to build the glade package on the Windows platform, could you please tell me the installer package for glade you used, possibly the version and download source too? Installing gtk2hs now seems made really simply by the guys providing it and I installed and tested it successfully on a Windows machine. Where I'm stucking is the glade/libglade thing. I took the version from http://ftp.gnome.org/pub/GNOME/binaries/win32/libglade/2.6/ for a start and installed some http://ftp.gnome.org/pub/GNOME/binaries/win32/dependencies/too, but when running the cabal-configure step it halts with the oh so familiar: * Missing C libraries: glade-2.0, gtk-win32-2.0, xml2, gdk-win32-2.0, atk-1.0, gio-2.0, gdk_pixbuf-2.0, pangowin32-1.0, gdi32, pangocairo-1.0, pango-1.0, cairo, gobject-2.0, gmodule-2.0, glib-2.0, intl This is my user ghc-pkg cache list: ...APPDATA...\ghc\i386-mingw32-6.12.3\package.conf.d: SDL-0.6.2 base64-bytestring-0.1.0.0 cairo-0.11.1 gio-0.11.1 glib-0.11.2 gtk-0.11.2 pango-0.11.2 random-1.0.0.2 And my pkg-config output: cmd> pkg-config --cflags --libs gtk+-2.0 libglade-2.0" -mms-bitfields -IH:/takeoffgw/i686-pc-mingw32/sys-root/mingw/include/libxml2 -IH :/takeoffgw/usr/local/include/gtk-2.0 -IH:/takeoffgw/usr/local/lib/gtk-2.0/inclu de -IH:/takeoffgw/usr/local/include/atk-1.0 -IH:/takeoffgw/usr/local/include/cai ro -IH:/takeoffgw/usr/local/include/pango-1.0 -IH:/takeoffgw/usr/local/include/g lib-2.0 -IH:/takeoffgw/usr/local/lib/glib-2.0/include -IH:/takeoffgw/usr/local/i nclude/freetype2 -IH:/takeoffgw/usr/local/include -IH:/takeoffgw/usr/local/inclu de/libpng14 -IH:/takeoffgw/usr/local/include/libglade-2.0 -LH:/takeoffgw/i686-p c-mingw32/sys-root/mingw/lib -LH:/takeoffgw/usr/local/lib -lglade-2.0 -lgtk-win3 2-2.0 -lxml2 -lgdk-win32-2.0 -latk-1.0 -lgio-2.0 -lgdk_pixbuf-2.0 -lpangowin32-1 .0 -lgdi32 -lpangocairo-1.0 -lpango-1.0 -lcairo -lgobject-2.0 -lgmodule-2.0 -lgt hread-2.0 -lglib-2.0 -lintl ExitSuccess

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ANNOUNCE: game-probability-1.1
by Neil Brown 08 Sep '10

08 Sep '10

Hi, I've just released version 1.1 of my game-probability library. It's intended to be an easy way to investigate the probability of various dice rolls and card draws (the latter is the new addition for the 1.1 release), using a Haskell library/EDSL. It has various examples in the documentation, plus a few blog posts on its design (all links below). Hackage: http://hackage.haskell.org/package/game-probability Docs (while waiting for Hackage to generate): http://twistedsquare.com/game-probability-1.1/ Blog posts: http://chplib.wordpress.com/2010/08/13/nice-dice-in-haskell/ http://chplib.wordpress.com/2010/08/23/sharp-cards-in-haskell-drawing-cards/ http://chplib.wordpress.com/2010/09/08/sharp-cards-in-haskell-the-odds/ As a quick taster, below are some examples of using the library. Showing the probabilities of a dice roll prints out a bar chart -- here is the sum of two six-sided dice: > show (2 * d6) 2 : # 3 : ## 4 : ### 5 : #### 6 : ##### 7 : ###### 8 : ##### 9 : #### 10: ### 11: ## 12: # Querying probabilities of the outcomes of dice rolls: > chancePred (>= 16) (3*d6) 5 % 108 The chance of drawing different numbers of Copper cards in a starting hand of 5 drawn from 7 Copper and 3 Estate (this is from the card game Dominion): > chanceMap (makeCards $ replicate 7 "Copper" ++ replicate 3 "Estate") (drawCount (== "Copper") 5) fromList [(2,1 % 12),(3,5 % 12),(4,5 % 12),(5,1 % 12)] Thanks, Neil.

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CnC Haskell
by Vasili I. Galchin 08 Sep '10

08 Sep '10

Hello, I have been reading work done at Rice University: http://habanero.rice.edu/cnc. Some work has been done by http://www.cs.rice.edu/~dmp4866/ on CnC for .Net. One component that David wrote a CnC translator that translates CnC textual form to the underlying language, e.g. F#. Is anybody working on a CnC textual form translator for Haskell so a Haskell user of CnC Haskell can write in a higher level?? Thanks, Vasili

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How to catch exception within the Get monad (the Binary package)
by Dimitry Golubovsky 07 Sep '10

07 Sep '10

Hi, The following function* is supposed to decode a list of some serialized objects following each other in a lazy Bytestring: many :: Get a -> Get [a] many prs = many' [] where many' a = do s <- prs r <- isEmpty case r of True -> return (reverse a) False -> many' (s:a) prs is a "parser" to decode a single object. If however something goes wrong, and prs fails, the whole function fails (error is thrown). Since [a] (result of decoding) is a lazy list, actual exception may be thrown at any moment the list is being processed, and exception handler may not be properly set. Is there any way to catch/detect failures inside the Get monad? It is not an instance of MonadError, so catchError does not work. Ideally, the function would keep decoding as long as it is possible, and upon the first failure of the parser, return whatever has been decoded. Thanks. ----------------------------------------------- * there is one intentional inaccuracy in this function: isEmpty is called _after_ decoding is tried, so an empty ByteString would cause parser failure and exception right away; this is used as a test case. -- Dimitry Golubovsky Anywhere on the Web

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Re: [Haskell-cafe] help me evangelize haskell.
by Gaius Hammond 07 Sep '10

07 Sep '10

My usual rhetoric is that one-off, throwaway scripts never are, and not only do they tend to stay around but they take on a life of their own. Today's 10-line file munger is tomorrow's thousand-line ETL batch job on which the business depends for some crucial data - yet the original author is long gone and no-one dares modify in case it breaks. So it is just good sense to use sound practices from the very beginning. One of the features of Perl is that it will try to work even if you make type errors (e.g. give it a scalar in place of a list, or a string instead of an int). One day, however, it WILL fail. Haskell finds these types of bugs upfront, and not when your pager goes off at 3am... Cheers, G ------Original Message------ From: Michael Litchard Sender: haskell-cafe-bounces(a)haskell.org To: haskell-cafe(a)haskell.org Subject: [Haskell-cafe] help me evangelize haskell. Sent: Sep 4, 2010 17:38 I'll be starting a new job soon as systems tool guy. The shop is a perl shop as far as internal automation tasks go. But I am fortunate to not be working with bigots. If they see a better way, they'll take to it. So please give me your best arguments in favor of using haskell for task automation instead of perl, or awk or any of those scripting lanugages. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ------------------

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PSA: using MySQL from Haskell programs
by Bryan O'Sullivan 07 Sep '10

07 Sep '10

If you are using HDBC-mysql or HDBC-odbc to access MySQL databases, you may have run into problems with your programs failing due to connection errors. In this blog posting, I describe what's happening and how to work around it: http://www.serpentine.com/blog/2010/09/04/dealing-with-fragile-c-libraries-…

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Re: Haskell-Cafe Digest, Vol 85, Issue 20
by Jeff Rubard 07 Sep '10

07 Sep '10

Do U like combinatory logic - or lambda calculus? It still matters, or something.

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[ANN] Crypto-API 0.0.0.1 Released
by Thomas DuBuisson 07 Sep '10

07 Sep '10

At long last and after much fruitful discussion on libraries(a)haskell.org, Crypto-API is having its first release, version 0.0.0.1! Crypto-API is a generic interface for cryptographic operations, platform independent & quality entropy acquisition, property tests and known-answer tests (KATs) for common algorithms, and a basic benchmark infrastructure. Maintainers of hash and cipher implementations are encouraged to add instances for the classes defined in Crypto.Classes. Crypto users are similarly encouraged to use the interfaces provided. Any concepts or functions of general use to more than one cryptographic algorithm (ex: padding) is within scope of this package. Hackage: http://hackage.haskell.org/package/crypto-api Haddock: http://web.cecs.pdx.edu/~dubuisst/crypto-api-0.0.0.1/html/index.html Blog: http://tommd.wordpress.com/2010/09/07/crypto-api-released/ At it's heart, Crypto-API is an interface to cryptographic algorithms allowing crypto developers to provide a minimal, low level interface and reuse generic higher-level functions while freeing crypto users from specifying a particular algorithm or implementation. ---- Highlights ---- * Five type classes of Hash, BlockCipher, AsymCipher, StreamCipher, and CryptoRandomGen * Generic algorithms implemented using these class interfaces (ex: block cipher modes of operation, hashing and HMAC) * Platform independent acquisition of entropy for cryptographic use (using /dev/urandom on *nix and the CryptoAPI on windows) * Test suite and parsing of NIST KAT files * Rudimentary benchmarking for BlockCipher, Hash, and RNGs ---- Hash Example ---- The hash developer defines a class instances: > instance Hash MD5Context MD5Digest where > outputLength = Tagged 128 > blockLength = Tagged 512 > initialCtx = md5InitialContext > updateCtx = md5Update > finalize = md5Finalize The hash user can remain agnostic about which type of hash is used: > authMessage :: Hash ctx dgst => B.ByteString -> MacKey -> dgst -> Bool > authMessage msg k = (==) (hmac' k msg) More examples can be found on the blog post. ----Versioning---- I don't intend to bump the version number for API changes in modules that aren't built by default (Test.Crypto, Benchmark.Crypto). Otherwise the PVP is in effect. Let me know if this isn't appreciated. ---- Changes Since Release Candidate ---- * Haddock documentation * Crypto.HMAC uses MacKey to help users keep the key and message separate ----Remaining TODO---- * Optimize block cipher modes and add new ones * Migrate Crypto.Random to the "random" package, pending conversation and agreement. * a signature class is planned for signature-only algorithms (DSA) class (Binary k, Serialize k) => Signing k where sign :: ... verify :: ... * Verify Crypto.Random works on Windows (more likely: fix it) once a Windows dev shows interest. * Build and test Crypto.Padding * Expand test suite. Include other hashes, modes, block algorithms, cipher properties. * Improve benchmarks, use CryptoRandomGen class in benchmark. * More Haddock documentation * Consider adding "buildIV :: (CryptoRandomGen g) => g -> Either GenError iv" routine to StreamCipher interface Cheers, Thomas M. DuBuisson

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Re: [Haskell] ANNOUNCE: reference 0.1
by Maciej Piechotka 07 Sep '10

07 Sep '10

On Tue, 2010-09-07 at 02:15 +0200, Bas van Dijk wrote: > On Mon, Sep 6, 2010 at 11:55 PM, Maciej Piechotka <uzytkownik2(a)gmail.com> wrote: > > Reference is class which generalizes references and monads they exists > > in. It means that IORef, STRef and others can be accessed by common > > interface. > > > > Currently it is of form: > > > > class Reference r m where > > > > 1. There was a proposal to rename the class to MonadRef or > > MonadReference. IMHO it would imply m -> r functional dependency and > > therefore disallow the instances for both MVar IO and IORef IO > > > > 2. Should the functional dependencies or type famillies be introduced? > > Personally I don't think so as I would like to allow all of the > > following: > > > > - IORef IO > > - MVar IO > > - IORef (ContT IO) > > - MVar (ContT IO) > > > > Any feedback mostly welcome. > > > > Regards > > PS. Darcs repository will be available soon > > > > _______________________________________________ > > Haskell mailing list > > Haskell(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell > > > > > First I'd like to say sorry for error in cafe mailing list address. The whole e-mail is included above. > I've played with a somewhat similar idea: > > darcs get http://code.haskell.org/~basvandijk/code/only-read-or-write-vars > > API Docs + Hyperlinked source: > http://code.haskell.org/~basvandijk/code/only-read-or-write-vars/doc/html/o… > > This is not released (yet) because I'm unsure about the design. > > Especially, I'm unsure whether parameterizing Readable with α is a good idea: > > class Readable v m α | v → m where read v → m α > > and whether parameterizing Writable with α and β is a good idea: > > class Writable v α m β | v → m where write v → α → m β > > They do allow some some nice instances like: > > instance Readable (TMVar α) STM (Maybe α) where > read = TMVar.tryTakeTMVar > > instance Writable (TMVar α) α STM Bool where > write = TMVar.tryPutTMVar > > instance Writable (Chan α) (End α) IO () where > write t = Chan.unGetChan t unEnd > > -- | Writing @End x@ to a 'Chan' or 'TChan' writes @x@ to the end of the channel > -- instead of to the front. Also see 'unGetChan' and 'unGetTChan'. > newtype End α = End {unEnd α} > > Regards, > > Bas > I guess they are to some extend like Foldable to FoldableLL and possibly describing different aspects. Yours seems to be a bit like StateVar[1] generalized for different monads. Support for ptr & others is additional bonus. I wanted clear 1-1 mapping with references - i.e. basic 2 operations with added third for 'atomic' support. For example one of unmentioned law is that: write r x >> read r === write r x >> return r -- If it's only thread write r x >> write r y === write r y -- If it's only thread read r >> read r === read r read r >>= write r === id -- If it's only thread read r >>= const f === f -- If it's only thread? In fact I guess each on them could be used as RULES as IMHO each case in which it is not necessary true it is undeterministic anyway. While Chan is clearly writable and readable it cannot be considered a reference - it do have it purposes but they are usually different then references. To sum up - I would not be willing to use Readable/Writable in place of Reference but I don't say they don't have their purposes. PS. I took the liberty of continuing sentence. [1] http://hackage.haskell.org/package/StateVar-1.0.0.0

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Re: [Haskell-cafe] Re: Fwd: Semantics of iteratees, enumerators, enumeratees?
by John Lato 07 Sep '10

07 Sep '10

> > From: Heinrich Apfelmus <apfelmus(a)quantentunnel.de> > > Jason Dagit wrote: > > Heinrich Apfelmus wrote: > >> > >> I'm curious, can you give an example where you want to be explicit about > >> chunking? I have a hard time imagining an example where chunking is > >> beneficial compared to getting each character in sequence. Chunking > >> seems to be common in C for reasons of performance, but how does that > >> apply to Haskell? > > > > [...] > > I think it basically comes down to this: We replace lazy io with explicit > > chunking because lazy io is unsafe, but explicit chunking can be safe. > > Ah, I mean to compare Iteratees with chunking to Iteratees with single > character access, not to lazy IO. > > In C, this would be a comparison between read and getchar . If I > remember correctly, the former is faster for copying a file simply > because copying one character at a time with getchar is too granular > (you have to make an expensive system call every time). Of course, this > reasoning only applies to C and not necessarily to Haskell. > > Do you have an example where you want chunking instead of single > character access? > I am unable to think of any examples where you want chunking for any reason other than efficiency. Yesterday I spent some time on an element-wise iteratee implementation, and unfortunately it's significantly slower than any of the chunked implementations. I'm certain there's room for optimization, but I don't know if it's possible to make up the whole difference. I'd need to make some examination of the core to figure out where it could be improved. It's also possible that certain other implementations, such as your ProgramT version or the simplified implementation John Millikin recently posted to this list, would be more amenable to compiler magic for this purpose. John

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