- Haskell-Cafe - Haskell.org

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 08 Sep '10

08 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 08 Sep '10

08 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 08 Sep '10

08 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 08 Sep '10

08 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 08 Sep '10

08 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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Proposal: Form a haskell.org committee
by Ian Lynagh 07 Sep '10

07 Sep '10

Dear Haskellers, In recent years, haskell.org has started to receive assets, e.g. money from Google Summer Of Code, donations for Hackathons, and a Sparc machine for use in GHC development. We have also started spending this money: on the community server, on a server to take over hosting haskell.org itself, and on the haskell.org domain name. There is also interest in running fundraising drives for specific things such as Hackathon sponsorship and hosting fees. However, it is not currently clear who is responsible for determining what the haskell.org money should be spent on, or what are and are not acceptable uses of the domain name and hardware. To fix this problem, we propose that we create a "haskell.org committee", which is responsible for answering these sorts of questions, although for some questions they may choose to poll the community at large if they think appropriate. We suggest that the committee be composed of 5 representatives from the community, with committee members standing down after at most 3 years. Each year the committee will appoint one of their members to be the chair. As membership of "the Haskell community" is not well-defined, and voting would potentially be open to abuse if anyone were able to vote, we propose that the committee should choose their replacements from open nominations. Unfortunately, this gives us a bootstrapping problem, so we suggest that the initial committee be chosen from open nominations by some of the people who currently de-facto end up making the decisions currently: Duncan Coutts, Isaac Jones, Ian Lynagh, Don Stewart and Malcolm Wallace. These 5 would still be elligible to nominate themselves. Two of the initial members will stand down after one year, and two after two years, in order to bootstrap rolling membership turnover. We would love to hear feedback from you about this proposal, so that we can see whether the proposal, or something similar, has consensus amongst the community! A related issue is that haskell.org does not currently exist as a legal entity. We also hope to solve that problem, but we are still gathering information so that the community can make an informed decision, so I won't say more about that for now. Thanks Ian

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Re: [Haskell-cafe] Restricted type classes
by John Lato 07 Sep '10

07 Sep '10

> > > Message: 20 > Date: Sat, 04 Sep 2010 03:40:49 -0400 > From: wren ng thornton <wren(a)freegeek.org> > Subject: Re: [Haskell-cafe] Restricted type classes > To: Haskell Cafe <haskell-cafe(a)haskell.org> > Message-ID: <4C81F801.606(a)freegeek.org> > Content-Type: text/plain; charset=UTF-8; format=flowed > > On 9/3/10 12:16 AM, Ivan Lazar Miljenovic wrote: > > 2) How far should I go? Should I restrict myself to the > > "data-oriented" classes such as Functor, Traversable, etc. or should I > > try to make restricted versions of Applicative and Monad? Assuming I > > should: > > I'd say you should do as much as seems reasonable. I tend to take things > as far as I can, but that'd end up doing a lot of the same work as > category-extras. For a general collections library, I think it'd make > sense to try to keep things simpler than that if possible. The simpler > it is, the better the uptake will be, so long as it's still complex > enough to capture what it needs to. > > I'd say you should include: Functor, Foldable, Traversable, Pointed, > Applicative, Monad, and Monoid (both additive and multiplicative in > separate classes, as in the monoids package). Those eight make for a > really comprehensive toolkit that does most of the things people > frequently need. Of course, not every collection will have instances for > all of them. > Although I agree these do most things that people need, it's very rare that I need a data structure that guarantees *only* these features. Most often I need a map, a queue, etc. because I need either lookup by key, queue properties, etc. I think it's necessary to include classes like Indexable and Queue. Indexable may need to be split into two, one for ordered-Int indexes (i.e. lists) and one for Maps. Just a few days ago I wanted to change the priority queue implementation in some code. This was painful because the different available implementations all have varying APIs, so I couldn't just change the imports. I've wanted to do this in other contexts as well (e.g. maps and tries). The perhaps more important use is for coding algorithms that depend upon map properties, queue properties, etc., but leaving the actual implementation polymorphic so it can be chosen by a higher level. If the purpose of this project is to present a common interface for containers, then I think you should start by seeing what are the most common containers (I would guess lists, sets, maps, and queues) with a goal of providing their specific functionality through classes. Then all the common stuff can be stripped out and provided by superclasses. Of course we already know a great deal of the common operations, e.g. Traversable and Foldable, and we make use of those abstractions. It's this last step of a common map interface, queue interface, etc. that's missing. If you're just going to provide stuff we already have, I don't really see the point. > > > 2c) Should I keep the classes as-is, or should I explicitly put in the > > constraints mentioned in the Typeclassopedia (e.g. make Applicative an > > explicit superclass of Monad, and define return = pure for > > compatability reasons)? If so, should I bring over Pointed, etc. from > > category-extras to round out the set or just stick with classes that > > are already in base? > > If you're defining a new hierarchy, I'd say you should do it correctly, > i.e. > > class Functor where fmap > class Functor => Pointed where unit -- or point > class Pointed => Applicative where (<*>) ; (<*) ; (*>) > class Applicative => Monad where (>>=) ; join > Shouldn't it be: class Functor where fmap class Pointed where point class (Functor f, Pointed f) => PointedFunctor f where class PointedFunctor f => Applicative f where (<*>); --etc. class Applicative f => Monad f where (>>=); --etc. even I might omit PointedFunctor, though, because it doesn't add anything. If it is omitted, that just means your Applicative contexts are slightly longer. But please don't make Pointed depend on Functor - we've already seen that it won't work for Bloom filters. Cheers, John

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circular imports
by Evan Laforge 07 Sep '10

07 Sep '10

Lately I've been spending more and more time trying to figure out how to resolve circular import problems. I add some new data type and suddenly someone has a new dependency and now the modules are circular. The usual solution is to move the mutually dependent definitions into the same module, but sometimes those threaten to drag in a whole zoo of other dependencies, *all* of which would have to go into the same module, which is already quite large anyway. Of course this requires lots of thought and possibly refactoring and is a big pain all around. I feel like the circular imports problem is worse in haskell than other languages. Maybe because there is a tendency to centralize all state, since you need to define it along with your state monad. But the state monad module must be one of the lower level ones, since all modules that use it must import it. However, the tendency for bits of typed data to migrate into the state means it's easy for it to eventually want to import one of its importers. And the state monad module gets larger and larger (the largest modules in my system are those that define state monads: 1186 lines, 706 lines, 1156 lines---the rest tend to be 100--300 lines). I haven't really had this problem in other languages. Maybe it's because I just don't write very big programs in other languages, or maybe because some other languages are dynamically typed and don't make you import a module to use its types, or maybe because some other languages support forward declaration (actually, ghc haskell does support a form of forward declaration in hs-boot files). I have a few techniques to get out: - Replace Things with ThingIds which have no big dependencies, and can then be looked up in a Map later. This replaces direct access with lookup and thows some extra Maybes in there, which is not very nice. - Cleverly use type variables to try to factor out the problematic type. Then I can stitch the data structure back together at a higher level with a type alias. This is sort of complicated and awkward. - Move the declarations that must be moved to the low level module, re-export them from the module that defines their (smart) constructors, and pretend like they belong to that module. This works well when it can work, but makes the code awkward to navigate and doesn't let you hide their implementation unless you give up and move the rest of the code in as well. - Just use an hs-boot. The main problem I've noticed with this so far is that you wind up with a lot of recompilation, since ghc always seems to want to start with the boot files and then recompile the loop. This makes ghci use a little more annoying. Actually, sometimes :r simply reloads the changed module, but sometimes it wants to start again at the hs-boots and recompiles a whole pile, I'm not sure what makes the difference. Probably making the loop as small as possible would help here. Is this a problem others have noticed? Any other ideas or solutions? thanks!

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random-fu confusion
by Alex Rozenshteyn 07 Sep '10

07 Sep '10

I seem to be having confusion at the runRVar level of random-fu. I can't figure out how to use the Data.Random.Source.PureMT module to get a meaningful random source (I can't get my code to type-check). I wrote a [trivial] flipCoin function > flipCoin = uniform False True and am trying to fill in the final place of runRVar > :t runRVar (replicateM 20 flipCoin) runRVar (replicateM 20 flipCoin) :: (RandomSource m s) => s -> m [Bool] -- Alex R

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Paralelism and Distribution in Haskell
by Ivan S. Freitas 07 Sep '10

07 Sep '10

Hi fellow haskellers, I'm interested in the performance of parallel and/or distributed implementations in haskell language. For example, supose I want to develop an application that distributes a computation between many multicore computers, what are the advantages I can take from haskell in that? Anyone who has experience doing distributed computing with haskell, and could point some diferences between haskell and other languages? Any feedback is very much apreciated. Thanks. Regards. -- ============================================== Ivan Sichmann Freitas Engenharia de Computação 2009 UNICAMP http://identi.ca/ivansichmann Grupo Pró Software Livre UNICAMP - GPSL ==============================================

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local-search
by R Senington 07 Sep '10

07 Sep '10

I was recently at IFL2010, where I gave a short presentation on my the attempts to put together a local search library for Haskell. This was reasonably well received, and I had a couple of requests for a library. After a couple of days sanitizing the code, and learning a bit about how to package libraries for Hackage I am now announcing that the library has been uploaded, version 0.0.1. Of course I managed to make an error in the summary so it start "AA first...." rather than just "A first". I hope that people find this interesting and I look forward to feedback. http://hackage.haskell.org/package/local-search RS

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Fwd: Searching for Haskell (was: [Haskell-cafe] Slightly humorous: Headhunters toolbox (example for Germany))
by Alberto G. Corona 07 Sep '10

07 Sep '10

Ooops Just after sending this I relized that it is possible to narrow the search using categories. Using the category programming: http://www.google.com/insights/search/?hl=en-US#&cat=31&q=haskell&cmpt=q <http://www.google.com/insights/search/?hl=en-US#&cat=31&q=haskell&cmpt=q>it is even possible to compare the evolution of the term against the whole category. Both go down with time (because technical people dominate less and less the wen searches) . But the slope of "Haskell" is lesser than the one of "programming". By the way, it is possible to compare two or more search terms. Within the category programming, monad, and "type class" are scarce compared with "object" but the slope of the former ones are clearly up while object is down. (press "growth compared with the programing category"). What happened in the first half of 2006? monads were high there!. An further example is lazy versus strict. Both are comparable in percentage, but lazy is scandalously up while strict is down at the same rate. http://www.google.com/insights/search/?hl=en-US#cat=31&q=lazy%2Cstrict%2C&c… By the way, the term "tired" has increasing share in the programming category ;) 2010/8/31 Henk-Jan van Tuyl <hjgtuyl(a)chello.nl> On Tue, 31 Aug 2010 13:57:42 +0200, Alberto G. Corona <agocorona(a)gmail.com> > wrote: > > Entering "haskell language" instead of "haskell" the ambiguity >> dissapears. Then, Jamaica no longer appears in the crude reality . The >> weigth of USA is hides all other country here. >> >> I think that a more appropriate term to look for haskell interest is >> "monad" although it may catch some crazy philosophers too. The result is >> interesting, >> >> > You can still get things like a page titled "Ben Haskell - Language > Technologies Institute - Carnegie Mellon", and of course, not all pages > about the programming language contain the word "language". To get proper > results you would need a good semantic search engine, but these search > engines seem to be in early research stage. > > Regards, > Henk-Jan van Tuyl > > > -- > http://Van.Tuyl.eu/ > http://members.chello.nl/hjgtuyl/tourdemonad.html > -- >

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ghc HEAD
by Johannes Waldmann 07 Sep '10

07 Sep '10

I was compiling ghc-6.13.20100831 from source (*) and then compiling repa-examples with that, and the generated executable says (when called with +RTS -N2): Most RTS options are disabled. Link with -rtsopts to enable them. Where? How? When? (Did I make some error earlier?) (*) that's the latest available src snapshot? (Sadly, it does not contain containers-0.4) How come there are binaries without sources at: http://www.haskell.org/ghc/dist/current/dist/ While "cabal install repa-examples" works nicely, it is still way too easy to break the system, since cabal install will happily (and silently) destroy ghc's libraries. (e.g. happens for me after installing syb) unfortunately, this means I cannot easily test ghc HEAD and/or containers-0.4 on my sources. J.W.

2 1

generating foreign Code (Java, C++, PHP)?
by Günther Schmidt 07 Sep '10

07 Sep '10

Hi list, I noticed that there are some libs / packages like atom and HJscript which allow you to write a program in a haskell EDSL and that then actually generates valid source code in another language. In the above example that would be JavaScript and C. I sure would love to be able to write PHP for instance like that but I cannot even fathom how a EDSL would have to be designed for it. Could someone here point me to literature on the topic? Günther

3 2

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

07 Sep '10

At first I regarded this as simply a bug in the Iteratee.map definition, but like Ben, it's started to bother me a lot. I think this is precisely the sort of issue a proper denotational semantics would fix. Unfortunately the only general solution I see is to abandon chunking and work strictly element-wise. I say unfortunately because my current best implementation is about 5 times slower than the main tree. I'm open to ideas. John > From: Ben <midfield(a)gmail.com> > > Sorry to be late coming into this conversation..... > > Something that has bothered me (which I have mentioned to John Lato > privately) is that it is very easy to write non-compositional code due > to the chunking. For example, there is a standard function > > map :: (a -> b) -> Enumeratee a b c > > whose meaning I hope is clear : use the function to transform the type > of a stream and pass it to an iteratee. However last I checked the > versions provided in both the iteratee and enumerator packages fail to > satisfy the equation > > map f (it1 >> it2) == (map f it1) >> (map f it 2) > > because of chunking, essentially. You can check this with f == id and > it1 and it2 are head: > > let r = runIdentity . runIteratee > > runIdentity $ run $ enumList 10 [1..100] $ r $ joinI $ map id $ r (head >> > head) > --> Right (Just 2) > > runIdentity $ run $ enumList 10 [1..100] $ r $ joinI $ (map id $ r > head) >> (map id $ r head) > --> Right (Just 11) > > It is possible to fix this behavior, but it complicates the "obvious" > definitions a lot. > > B > > On Wed, Sep 1, 2010 at 5:10 AM, Heinrich Apfelmus > <apfelmus(a)quantentunnel.de> wrote: > > Tilo Wiklund wrote: > >> > >> Daniel Fischer wrote: > >>> > >>> [...] > >>> Well, I just gave an example where one would want chunking for reasons > >>> other than performance. That iteratees don't provide the desired > >>> functionality is a different matter. > >>> [...] > >> > >> In the case of hashing, wouldn't it be more reasonable to consider > >> iterators over streams of fixed (or at least predictable) sized chunks > >> (where a set of chunks can themselves be chunked), with the chunking > >> behaviour being given by another iteratee over the original stream? > >> > >> It seems to me that one of the major points of iteratees is to provide > >> an abstraction from the kind of chunking irrelevant to the parsing > >> logic, otherwise I fail to see any difference (at least relevant to > >> chunking) to plain strict IO. > > > > I thought so, too, but I was informed[1] that iteratees are just a small > > step up the abstraction ladder. The difference compared to an ordinary > file > > Handle is that you can now reuse one and the same iteratee for reading > > from a String , for instance, without changing the source code of the > > iteratee. > > > > Furthermore, iteratees can be suspended, which facilities resource > > management like closing files handles after they've been read. > > > > [1]: > > > http://www.reddit.com/r/haskell/comments/ar4wb/understanding_iteratees/c0j0… > > > > > > > > Regards, > > Heinrich Apfelmus > > > > -- > > http://apfelmus.nfshost.com > > > > _______________________________________________ > > Haskell-Cafe mailing list > > Haskell-Cafe(a)haskell.org > > http://www.haskell.org/mailman/listinfo/haskell-cafe > > > >

1 0

Re: [Haskell-cafe] Restricted type classes
by John Lato 07 Sep '10

07 Sep '10

> > From: Stephen Tetley <stephen.tetley(a)gmail.com> > > On 6 September 2010 20:18, John Lato <jwlato(a)gmail.com> wrote: > > > Can you give an example of a Functor that doesn't have pure? I think > it's > > Pointed Functors which are useful; not Functor by itself. > > Strictly speaking is Pair one? The current implementation tacks on monoid. > Interesting example. I tend not to like implementations which rely on bottoms, so I think I'd agree. In a similar spirit, I would propose Data.Vector.Unboxed.Vector as a Pointed Functor (modulo element restrictions) which is not Applicative, since the necessary element restrictions mean <*> can't be defined. John

1 0

Oracle stored procedures
by Peter Marks 07 Sep '10

07 Sep '10

Are there any Haskell libraries that can call stored procedures in Oracle? I've been looking at Takusen which I like, but I can't find a way to call a stored procedure. Thanks Peter

2 1

Re: [Haskell-cafe] container-classes (was: Restricted type classes)
by John Lato 07 Sep '10

07 Sep '10

I'd like to make one more argument in favor of my preference for more splitting of type classes. IMO it's beneficial to split up classes to minimize unnecessary dependencies. That is, while e.g. Monoid is very useful for containers, many container methods won't need it, e.g. "elem" or "filter". When you divide the type classes so only what's necessary is required, more data structures will be able to meet those criteria, which in turn makes the class more generally useful. As an example, I have an extension to iteratee which uses raw buffers for holding data. This allows it to operate in truly constant memory (only one allocation, deallocated when it's finished), which has resulted in performance benefits. Unfortunately there is not a good Monoid instance for this type because appending buffers is not possible. By introducing the NullPoint class (equivalent to mempty of Monoid) in iteratee, my raw buffer extension is able to re-use several iteratee functions which it would not be able to if I had require Monoid instead of NullPoint. I think I've made my arguments as well as I can, so I'm going to be quiet now unless something new comes up. Cheers, John

3 3

overloaded list literals?
by Johannes Waldmann 07 Sep '10

07 Sep '10

I think left-biased (= singly linked) lists are much overrated in Haskell coding (and teaching). The language (syntax and Prelude) makes it just too easy to use them, and old habits (from LISP) die hard. Sure, lists serve a purpose: * they model (infinite, lazy) streams, used in the producer/transformer/consumer pattern * they are an algebraic data type, so you can use them to teach recursion ((co-)induction); but more often, lists are (mis-)used when actually * you want some efficiently index-able and concat-able sequence type * or you don't need the indexing, just membership, so you actually want Data.Set (disregarding strictness and unwanted Ord instances for the moment). It is an empirical law that in 90 percent of the cases where a computer science student says "list" he means "set". * you avoid/forget to tell your students about algebraic data types in general. Hypothetically now ... We have overloaded numerical literals (Num.fromInteger) and we can overload string literals (IsString.fromString), so how about using list syntax ( [], : ) for anything list-like (e.g., Data.Sequence)? Of course some "minor details" would need to be worked out, like what methods should go in the hypothetical "class IsList" (is is Foldable?) and what to do about pattern matching (perhaps we don't need it?) IIRC there was a time when list comprehension would actually mean monad comprehension (when there was no "do" notation) but that's not what I'm getting at here. Or is it? Do we have a "Haskell museum" of ideas from the past? Best - J.W.

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Projects that could use student contributions?
by Brent Yorgey 07 Sep '10

07 Sep '10

Hi all, This fall I'll be teaching a half-credit introduction to Haskell to some undergrads. As a final project I am thinking of giving them the option of (instead of developing some program/project of their own) contributing to an existing open-source Haskell project. Of course, this requires the existence of projects they could contribute to. I'm sure they exist, but need your help to figure out what they are. So, do you maintain, or know of, any projects with the following characteristics? * might conceivably be interesting to undergraduate CS majors * simple enough that someone could make some non-trivial contributions in the space of 3 or 4 weeks * could use some help! This is a little non-traditional, so we'll see how it goes! -Brent

7 6

running ghci simply
by Johann Bach 07 Sep '10

07 Sep '10

Is there a way to run a Haskell module via ghci with a single command on the command-line? Note: I'm on Windows XP. If I have the module test.hs, I can type "test.hs" and that will load it into ghci. However, I need to then type "main" to run it, and then manually exit ghci. I would like to do all this in one step.

4 6

ANN: hledger 0.12.1
by Simon Michael 07 Sep '10

07 Sep '10

I'm pleased to announce hledger 0.12.1, with a new web interface and bugfixes. Thanks to Ben Boeckel and David Patrick for their help this time around. Installation docs, linux/mac/windows binaries and more are at http://hledger.org and http://hackage.haskell.org/package/ hledger . Release notes: 2010/9/6 hledger 0.12.1 * web: new, better web ui; accounts are now a permanent sidebar; add form uses auto-completing combo fields * installing: fix a build error with parsec 3 (#22) * installing: require exactly matching hledger-lib version for more robust builds * installing: explicit data-object dependency to ensure hledger and hledger-lib use the same time version * installing: explicit hamlet dependency for more robust building * installing: build threaded and with warnings * installing: drop -fweb610 flag * installing: add gtk2hs-buildtools dependency needed to build with -fchart * installing: require cabal 1.6 or greater * add -D/--daily flag * register: with --depth, clip account names or aggregate postings rather than excluding them * fix !include with deeply nested directories (#21) * fix obscured date parse errors with parsec 3 * handle unicode better in errors * fix a ghc 6.12.3 error when running interpreted Stats: 50 days and 90 commits since last release, now at 5741 lines of code with 136 tests and 41% unit test coverage. Goals for the next release are: 1. implement a plugin mechanism, probably by searching for hledger-* named binaries in $PATH at startup and handing over control. This should make packaging easier and more scalable. 2. move web/vty/chart features into their own packages. 3. developer docs 4. a public project ledger tracking expenses/income/resources Problem reports and all help are welcome; additional bugfix releases will appear on hackage if needed. Best, -Simon

1 0

Graphics.Drawing
by han 07 Sep '10

07 Sep '10

I think there should be Graphics.Drawing (along with Graphics.Rendering) and many graphics packages should go into it. So * Graphics.Rendering will contain more technical and rendering-engine-level packages (OpenGL, GD, ...) * while Graphics.Drawing will be for higher-level and user-friendlier drawing tools. (gloss, graphics-drawingcombinators, hieroglyph, Chart, ...) Currently most graphics packages are thrown into Graphics.Rendering or even Graphics. I think we all agree that having a standalone package right under Graphics is undesirable. There needs to be at least one subcategory. (which is why I also think Win32 and X11 should be moved from Graphics to Graphics.UI.) What do you think?

5 6

Update gtk2hs!
by Andy Stewart 06 Sep '10

06 Sep '10

Hi all, I'm working on update gtk2hs APIs. 'gio' has update to newest version, all patches has push to repo, i need more test before release gio-0.12.0 About `gtk` packages, i have push some gtk+-2.18/gtk+-2.20 patches to repo but not all, i plan finish all APIs before release gtk-0.12.0. If anyone interested this, welcome to join! :) We can release gtk-0.12.0 quicker if more people join us. GTK+-2.18 new modules have *finish* at http://www2.in.tum.de/~simona/gtk2hs-2.18/gtk/Graphics/UI/Gtk/ Because have some bugs in those code (my fault), you need review every APIs before send patch, but it's much simple than build those module by yourself. Below are missing modules in gtk+-2.18: gtk/Graphics/UI/Gtk/Printing/PageSetup.chs gtk/Graphics/UI/Gtk/Printing/PaperSize.chs gtk/Graphics/UI/Gtk/Printing/PrintContext.chs gtk/Graphics/UI/Gtk/Printing/PrintOperation.chs gtk/Graphics/UI/Gtk/Printing/PrintOperationPreview.chs gtk/Graphics/UI/Gtk/Printing/PrintSettings.chs gtk/Graphics/UI/Gtk/Recent/RecentChooser.chs gtk/Graphics/UI/Gtk/Recent/RecentChooserDialog.chs gtk/Graphics/UI/Gtk/Recent/RecentChooserMenu.chs gtk/Graphics/UI/Gtk/Recent/RecentChooserWidget.chs gtk/Graphics/UI/Gtk/Recent/RecentFilter.chs gtk/Graphics/UI/Gtk/Recent/RecentInfo.chs gtk/Graphics/UI/Gtk/Recent/RecentManager.chs gtk/Graphics/UI/Gtk/Special/HRuler.chs gtk/Graphics/UI/Gtk/Special/Ruler.chs gtk/Graphics/UI/Gtk/Special/VRuler.chs gtk/Graphics/UI/Gtk/Selectors/HSV.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/Action.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/ActionGroup.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/Activatable.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/RadioAction.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/RecentAction.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/ToggleAction.chs gtk/Graphics/UI/Gtk/ActionMenuToolbar/UIManager.chs gtk/Graphics/UI/Gtk/Buttons/gtk/Graphics/UI/Gtk/LinkButton.chs gtk/Graphics/UI/Gtk/Buttons/gtk/Graphics/UI/Gtk/ScaleButton.chs gtk/Graphics/UI/Gtk/Buttons/gtk/Graphics/UI/Gtk/VolumeButton.chs gtk/Graphics/UI/Gtk/Display/InfoBar.chs gtk/Graphics/UI/Gtk/Entry/EntryBuffer.chs gtk/Graphics/UI/Gtk/Gdk/AppLaunchContext.chs gtk/Graphics/UI/Gtk/Gdk/Colormap.chs gtk/Graphics/UI/Gtk/Gdk/Device.chs gtk/Graphics/UI/Gtk/Gdk/DisplayManager.chs gtk/Graphics/UI/Gtk/Gdk/Keymap.chs gtk/Graphics/UI/Gtk/Gdk/PixbufLoader.chs gtk/Graphics/UI/Gtk/Gdk/Visual.chs gtk/Graphics/UI/Gtk/General/AccelGroup.chs gtk/Graphics/UI/Gtk/General/AccelMap.chs gtk/Graphics/UI/Gtk/General/Binding.chs gtk/Graphics/UI/Gtk/General/IconInfo.chs gtk/Graphics/UI/Gtk/General/Paint.chs gtk/Graphics/UI/Gtk/MenuComboToolbar/Item.chs gtk/Graphics/UI/Gtk/MenuComboToolbar/ToolShell.chs gtk/Graphics/UI/Gtk/Misc/IMContextSimple.chs gtk/Graphics/UI/Gtk/ModelView/CellEditable.chs gtk/Graphics/UI/Gtk/ModelView/CellRendererAccel.chs gtk/Graphics/UI/Gtk/ModelView/CellRendererSpin.chs GTK+2.20 just below APIs haven't finish: Index of new symbols in 2.20 C GtkCellEditable:editing-canceled, object property in GtkCellEditable GtkCellRendererSpinner:pulse, object property in GtkCellRendererSpinner GtkCellRendererSpinner:size, object property in GtkCellRendererSpinner gtk_cell_renderer_spinner_new, function in GtkCellRendererSpinner O gtk_offscreen_window_get_pixbuf, function in GtkOffscreenWindow gtk_offscreen_window_get_pixmap, function in GtkOffscreenWindow gtk_offscreen_window_new, function in GtkOffscreenWindow P gtk_paint_spinner, function in GtkStyle gtk_printer_get_hard_margins, function in GtkPrinter gtk_print_context_get_hard_margins, function in GtkPrintContext T GtkToolPalette::set-scroll-adjustments, object signal in GtkToolPalette GtkToolPalette:exclusive, object property in GtkToolPalette GtkToolPalette:expand, object property in GtkToolPalette GtkToolPalette:icon-size, object property in GtkToolPalette GtkToolPalette:icon-size-set, object property in GtkToolPalette GtkToolPalette:toolbar-style, object property in GtkToolPalette gtk_tool_item_get_ellipsize_mode, function in GtkToolItem gtk_tool_item_get_text_alignment, function in GtkToolItem gtk_tool_item_get_text_orientation, function in GtkToolItem gtk_tool_item_get_text_size_group, function in GtkToolItem gtk_tool_item_group_get_collapsed, function in GtkToolItemGroup gtk_tool_item_group_get_drop_item, function in GtkToolItemGroup gtk_tool_item_group_get_ellipsize, function in GtkToolItemGroup gtk_tool_item_group_get_header_relief, function in GtkToolItemGroup gtk_tool_item_group_get_item_position, function in GtkToolItemGroup gtk_tool_item_group_get_label, function in GtkToolItemGroup gtk_tool_item_group_get_label_widget, function in GtkToolItemGroup gtk_tool_item_group_get_nth_item, function in GtkToolItemGroup gtk_tool_item_group_get_n_items, function in GtkToolItemGroup gtk_tool_item_group_insert, function in GtkToolItemGroup gtk_tool_item_group_new, function in GtkToolItemGroup gtk_tool_item_group_set_collapsed, function in GtkToolItemGroup gtk_tool_item_group_set_ellipsize, function in GtkToolItemGroup gtk_tool_item_group_set_header_relief, function in GtkToolItemGroup gtk_tool_item_group_set_item_position, function in GtkToolItemGroup gtk_tool_item_group_set_label, function in GtkToolItemGroup gtk_tool_item_group_set_label_widget, function in GtkToolItemGroup gtk_tool_palette_add_drag_dest, function in GtkToolPalette gtk_tool_palette_get_drag_item, function in GtkToolPalette gtk_tool_palette_get_drag_target_group, function in GtkToolPalette gtk_tool_palette_get_drag_target_item, function in GtkToolPalette gtk_tool_palette_get_drop_group, function in GtkToolPalette gtk_tool_palette_get_drop_item, function in GtkToolPalette gtk_tool_palette_get_exclusive, function in GtkToolPalette gtk_tool_palette_get_expand, function in GtkToolPalette gtk_tool_palette_get_group_position, function in GtkToolPalette gtk_tool_palette_get_hadjustment, function in GtkToolPalette gtk_tool_palette_get_icon_size, function in GtkToolPalette gtk_tool_palette_get_style, function in GtkToolPalette gtk_tool_palette_get_vadjustment, function in GtkToolPalette gtk_tool_palette_new, function in GtkToolPalette gtk_tool_palette_set_drag_source, function in GtkToolPalette gtk_tool_palette_set_exclusive, function in GtkToolPalette gtk_tool_palette_set_expand, function in GtkToolPalette gtk_tool_palette_set_group_position, function in GtkToolPalette gtk_tool_palette_set_icon_size, function in GtkToolPalette gtk_tool_palette_set_style, function in GtkToolPalette gtk_tool_palette_unset_icon_size, function in GtkToolPalette gtk_tool_palette_unset_style, function in GtkToolPalette After finish above modules, gtk2hs will support all APIs to gtk+-2.20! Any suggestion and bug repot are welcome! Cheers, -- Andy

1 0

Operator precedence
by michael rice 06 Sep '10

06 Sep '10

Is there a handy list of operators and their precedence somewhere? Michael

5 9

Re: ANNOUNCE: countable-0.1
by Maciej Piechotka 06 Sep '10

06 Sep '10

On Mon, 2010-09-06 at 03:54 -0700, Ashley Yakeley wrote: > countable: Countable, Searchable, Finite, Empty classes. > > class Countable, for countable types > class AtLeastOneCountable, for countable types that have at least one > value > class InfiniteCountable, for infinite countable types > class Searchable, for types that can be searched over > class Finite, for finite types > class Empty, for empty types > data Nothing, an empty type > > Also includes these orphan instances: > > instance (Searchable a,Eq b) => Eq (a -> b) > instance (Finite a) => Foldable ((->) a) > instance (Finite a) => Traversable ((->) a) > instance (Show a,Finite a,Show b) => Show (a -> b) > > It turns out Searchable includes some infinite types. Specifically, > countable implements this: > > instance (Countable c,Searchable s) => Searchable (c -> s) > > using the algorithm described here: > > http://math.andrej.com/2007/09/28/seemingly-impossible-functional-programs/ > > I would welcome improvements. > > http://hackage.haskell.org/package/countable-0.1 > cabal install countable > darcs get http://code.haskell.org/countable/ > > See also this thread: > http://thread.gmane.org/gmane.comp.lang.haskell.cafe/73275 > Hmm. 1. Code formatting is very C#-like. At least for me it is hard to read the code that way (it IS matter of preference however) 2. countMaybeNext seems to need documentation. If I understand it correctly: countMaybeNext Nothing = 'minimalValue' countMaybeNext (Just x) = x + 1 Wouldn't be split it to: countNext :: a -> Maybe a initial :: Maybe a 3. Regards

1 0

ANNOUNCE: Haddock version 2.8.0
by David Waern 06 Sep '10

06 Sep '10

-------------------------------------------- -- Haddock 2.8.0 -------------------------------------------- A new version of Haddock, the Haskell documentation tool, is out! The biggest news this time is that we have a shiny new XHTML backend, created by Mark Lentczner, which outputs semantically correct XHTML, making it much easier to create new themes for Haddock. Mark has made an extraordinary effort by going through and rewriting the old table based HTML backend, fixing non-standards-compliant quirks, and adding a bunch of new useful features on top of that. See the changelog for more details. Included is a new default CSS theme created by Thomas Schilling, Mark and Johan Tibell, as well as the classic theme converted to work with the new backend. Another great new feature is markup support for examples, contributed by Simon Hengel. The idea is to be able to write examples that function both as documentation and unit tests. Last but not least, we now also have a LaTeX backend. It was written by Simon Marlow and it was used to generate the libraries section of the Haskell 2010 report. This version is compatible with .haddock files produced by Haddock 2.6.1 and above, provided that the version of GHC used to build Haddock stays the same. -------------------------------------------- -- Changes in version 2.8.0 -------------------------------------------- * HTML backend completely rewritten to generate semantically rich XHTML using the xhtml package. * New default CSS based on the color scheme chosen for the new Haskell wiki, with a pull-out tab for the synopsis. * Theme engine based on CSS files. Themes can be switched from the header menu. (New flags --built-in-themes and --theme. The latter is an alias for --css which now has extended semantics). * Markup support for executable examples/unit-tests. To be used with an upcoming version of the DocTest program. * Addition of a LaTeX backend. * Frames-mode can be enabled from the header menu. * Path to source entities can be specified per package, so that source links work for cross-package documentation. * Support for a second form of enumerated lists (1. 2. etc). * Additions and changes to the Haddock API. * New flag --no-tmp-comp-dir to tell Haddock to read/write compilation files (.o, .hi, etc) to/from GHC's output directory instead of to/from a temporary directory. * Various bug fixes. -------------------------------------------- -- Links -------------------------------------------- Homepage: http://www.haskell.org/haddock Hackage page: http://hackage.haskell.org/package/haddock-2.8.0 Bugtracker and wiki: http://trac.haskell.org/haddock Mailing list: haddock(a)projects.haskell.org Code repository: http://code.haskell.org/haddock -------------------------------------------- -- Contributors -------------------------------------------- The following people contributed patches to this release: Simon Hengel Mark Lentczner Ian Lynagh Simon Marlow Simon Peyton-Jones Thomas Schilling David Waern -------------------------------------------- -- Get Involved -------------------------------------------- We would be very happy to get more contributors. To get involved, start by grabbing the code: http://code.haskell.org/haddock Then take a look at the bug and feature tracker for things to work on: http://trac.haskell.org/haddock

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Re: [Haskell-cafe] Unnecessarily strict implementations
by Daniel Fischer 06 Sep '10

06 Sep '10

On Friday 03 September 2010 12:28:43, Jan Christiansen wrote: > Hi, > > On 03.09.2010, at 01:32, Daniel Fischer wrote: > > No surprise, there aren't many 'ä's in Shakespeare's works, are there? > > nope > > > On the other hand, the current implementation of lines does not seem > > to > > suffer from Wadler's tuple space leak (according to one test I > > made), so > > I'd stick with the current implementation for the time being. > > Well, I think it does. Indeed. I botched my test, allowing it to drop the reference to the first line too early by not using enough of it, so although lines shows the leak, let { ds1_s1ts :: ([Char], [Char]) LclId ds1_s1ts = case $wbreak @ Char lvl_r1uj wild_B1 of _ { (# ww1_anp, ww2_anq #) -> (ww1_anp, ww2_anq) } } in : @ String (case ds1_s1ts of _ { (l_aij, _) -> l_aij }) (case ds1_s1ts of _ { (_, s'_ail) -> case s'_ail of _ { , I managed to conceal it. > But obviously one can argue that this is a rare application. Yes. Ordinarily, lines in text files aren't longer than a few hundred characters, leaking those, who cares? But. Occasionally, long lines occur, and avoiding the space leak seems more important to me than having lines (_|_ : _|_) = _|_ : _|_ instead of lines (_|_ : _|_) = _|_ > Hopefully I haven't made a mistake here? No. > > By accident I stumbled across an odd behaviour. If I use the following > definition and replace all occurrences of break by break' in the > program above the memory behaviour is bad if I compile it without > profiling. But if I compile the program with -prof -auto-all the > program runs in constant space. Is this a known behaviour? I can't reproduce that. For me, it leaks also with profiling. > > break' :: (a -> Bool) -> [a] -> ([a],[a]) > break' p xs = (ys,zs) > where > (ys,zs) = break p xs > > Cheers, Jan

3 6

AngloHaskell 2010 - Final Reminder + Wi-Fi Sign-Up
by Derek Wright 06 Sep '10

06 Sep '10

AngloHaskell 2010 is this week! AngloHaskell 2010 - 5th Annual Haskell Meeting in England Friday September 10th and Saturday September 11th, 2010 Microsoft Research, Cambridge, UK http://www.haskell.org/haskellwiki/AngloHaskell/2010 AngloHaskell is a free gathering of all people Haskell-related from beginners to seasoned hackers, both academic and industrial. AngloHaskell 2010 is generously hosted by Microsoft Research. As a result no charge is made for attending or speaking. Friday will be a day of talks and discussion at MSR followed by a more informal day of activities on Saturday somewhere else in Cambridge. AngloHaskell welcomes talks on all Haskell related subjects. From short comments (Functional Grit) to full presentations, all are welcome. Please add your name and the title of your talk to the wiki page (or email me and I will add it for you). If you want to attend please add your name to the wiki page, or let me know by email. Even if you can't attend you can add you name to the "Not this year, but hopefully next!" section. Wi-Fi accounts (at Microsoft Research on Friday) are available on request. The sign-up deadline is Wednesday 8th September so please sign-up on the wiki page or email me (with Full Name, Institution, Country of Residence and Email Address). Organisational discussions are on held on the #anglohaskell channel on the Freenode IRC network, feel free to drop in with questions or comments.

1 0

Re: [Haskell-cafe] help me evangelize haskell.
by Mathew de Detrich 06 Sep '10

06 Sep '10

I Think you misinterpreted what I said. I didn't say you should tell the programmers how to code, I said you should show the perl coders how Haskell has advantages over pearls without much cost On 06/09/2010 5:21 PM, "Stephen Tetley" <stephen.tetley(a)gmail.com> wrote: On 6 September 2010 03:46, Mathew de Detrich <deteego(a)gmail.com> wrote: > If they are perl programme... Now that's going to go down well... Maybe the original poster might want to soak up the company culture for a while before than telling co-workers how to do things. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org h...

2 1

Re: ANNOUNCE: countable-1.0
by Nicolas Pouillard 06 Sep '10

06 Sep '10

On Mon, 06 Sep 2010 03:46:18 -0700, Ashley Yakeley <ashley(a)semantic.org> wrote: > countable: Countable, Searchable, Finite, Empty classes. > > class Countable, for countable types > class AtLeastOneCountable, for countable types that have at least one > value > class InfiniteCountable, for infinite countable types > class Searchable, for types that can be searched over > class Finite, for finite types > class Empty, for empty types > data Nothing, an empty type > > Also includes these orphan instances: > > instance (Searchable a,Eq b) => Eq (a -> b) > instance (Finite a) => Foldable ((->) a) > instance (Finite a) => Traversable ((->) a) > instance (Show a,Finite a,Show b) => Show (a -> b) Could you put these instances in a dedicated module? In the same vein I would like to have a newtype wrapper over functions were intention is to be used extensionally. Nice package BTW! -- Nicolas Pouillard http://nicolaspouillard.fr

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PhD position at the Software Technology group at Utrecht University
by Atze Dijkstra 06 Sep '10

06 Sep '10

There is currently a PhD position available at he Software Technology group, Department of Information and Computing Sciences, Utrecht University, Netherlands. The ST group focusses its research on programming methodologies, compiler construction, and program analysis. In this area the research will take place, in particular the topic is semi-automatic incrementalization of programs narrowed down to our Utrecht Haskell Compiler (UHC), using our Attribute Grammar system (UUAG). For more details and application see http://www.academictransfer.com/employer/UU/vacancy/6114/lang/en/ The application deadline is October 5, 2010. Please contact Prof. Dr. S.D. Swierstra at doaitse(a)cs.uu.nl for more information. The project is funded by a research grant from the Netherlands 'Organization for Scientific Research’ (NWO). Best regards, - Atze - Atze Dijkstra, Department of Information and Computing Sciences. /|\ Utrecht University, PO Box 80089, 3508 TB Utrecht, Netherlands. / | \ Tel.: +31-30-2534118/1454 | WWW : http://www.cs.uu.nl/~atze . /--| \ Fax : +31-30-2513971 .... | Email: atze(a)cs.uu.nl ............ / |___\

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help me evangelize haskell.
by Michael Litchard 06 Sep '10

06 Sep '10

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.

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Re: [Haskell-cafe] Unnecessarily strict implementations
by Henning Thielemann 06 Sep '10

06 Sep '10

Ivan Lazar Miljenovic schrieb: > On 3 September 2010 04:57, Arie Peterson <ariep(a)xs4all.nl> wrote: >> On Thu, 2 Sep 2010 19:30:17 +0200, Daniel Fischer >> <daniel.is.fischer(a)web.de> wrote: >>> Why would one consider using Ord for Map an abuse? >>> A kludge, for performance reasons, but an abuse? >> Because it forces one to declare Ord instances for types which have no >> natural ordering. It is useful to *not* have such instances, in order to >> catch programming errors. > > What precisely do you mean by natural ordering? E.g. I wanted to have a Set of Gaussian (complex) integers, but I did not want to define an Ord instance for them, because writing a < (b :: Gaussian) is a bug with high probability. >> A separate type class for types which can be ordered in some (possibly >> arbitrary) way, for use in Data.Map, would remedy this. > > Sure... except that the way Data.Map and Data.Set are implemented is > by a binary tree, and you typically want some kind of ordering for > those. > > How is a type class that represents arbitrary ordering any different > from what we already have? The notation might not be the best if you > consider the ordering to be arbitrary, but what else would you use? > "isArbitrarilyBefore :: (ArbitraryOrdering a) => a -> a -> Bool" ? Yes, something this way. (<) suggests a notion of magnitude for me, which some orderings do not have.

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base-3 -> base-4
by Johannes Waldmann 05 Sep '10

05 Sep '10

Is there a "conversion guide" for switching from base-3 to base-4? I noticed that ghc-HEAD (6.13) comes with base-4.3 (and no base-3). This will break an awful lot of packages (?), in fact the breakage starts with cabal-install (since it depends on HTTP which depends on base-3). PS: I use gmane.org for posting, and they have these seemingly random "text captchas", and for this post, it reads "continuity"...

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variable definition according to input
by Maria Merit 05 Sep '10

05 Sep '10

Hello, Is it possible to define variable names according to input data? For instance: input = "I k" => Int k input = "I m" => Int m input = "S s" => String s Of course, the real application is much more complicated, but the basic question is the same. Many thanks, Maria

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ANNOUNCE: darcs 2.5 beta 5
by Reinier Lamers 05 Sep '10

05 Sep '10

The darcs team would like to announce the immediate availability of darcs 2.5 beta 5 (also known as darcs 2.4.98.5 due to Cabal restrictions). Important changes since darcs 2.4.4 are: * trackdown can now do binary search with the --bisect option * darcs always stores patch metadata encoded with UTF-8 * diff now supports the --index option * amend-record now supports the --ask-deps option * apply now supports the --match option * amend-record has a new --keep-date option * inventory-changing commands (like record and pull) now operate in constant time with respect to the number of patches in the repository * the push, pull, send and fetch commands no longer set the default repository by default * the --edit-description option is now on by default for the send command Changes since the last beta release are: * document that GHC 6.10 is required to build darcs 2.5 * the --index flag is now disabled for amend-record because it was broken * clean up documentation for trackdown * no longer require a specific version of the hashed-storage package If you have installed the Haskell Platform or cabal-install, you can install this beta release by doing: $ cabal update $ cabal install darcs-beta Alternatively, you can download the tarball from http://darcs.net/releases/darcs-2.4.98.5.tar.gz and build it by hand as explained in the README file. Kind Regards, the darcs release manager, Reinier Lamers

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Re: [Haskell-cafe] Announce: lhae
by abau＠imn.htwk-leipzig.de 05 Sep '10

05 Sep '10

> Seems cool, but I do not really get it : why write it in haskell ? I > thought at first that your "formula language" was haskell, but it > looks more like a php derivative. This "formula language" is just a very simple language to insert formulas into cells. It has nothing to do with haskell. > Does it do more than the spreadsheet thing in openoffice ? I don't know the spreadsheet in openoffice, but I don't think that lhae does anything more or better than openoffice. > Also, maybe you could do the same with gnuplot, it would be really > cool to be able to use a friendlier language for defining functions > other than polynomials or the few standard floating point functions. Sorry, but I don't understand this point. I thought gnuplot is just for plotting graphs. But lhae is a (low level) spreadsheet application. But I may got something wrong on your question? _____________________________________________ HTWK Leipzig FIMN Webmail https://webmail.imn.htwk-leipzig.de/nocc/

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Re: [Haskell-cafe] Announce: lhae
by abau＠imn.htwk-leipzig.de 05 Sep '10

05 Sep '10

Serguey Zefirov <sergueyz(a)gmail.com> wrote: > You had selected wxWidgets because of what? Because of the neat grid class in wxWidgets. I did not find anything comparable in gtk. > Also, how long did it took (especially GUI part)? Hard to say, because I work on that project on irregular times in my spare time. But the GUI part was not the big deal, because wxhaskell is such a handy library. [1] http://docs.wxwidgets.org/stable/wx_wxgrid.html _____________________________________________ HTWK Leipzig FIMN Webmail https://webmail.imn.htwk-leipzig.de/nocc/

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autocomplete using hoogle
by Yuras Shumovich 05 Sep '10

05 Sep '10

Hello, Just want to share some results of my weekend hacking. It is clear that haskell type checker can help to build a list of suggestions for autocomplete (very old idea). I tried to create a very basic prototype to play with the idea. The approach I used: The task can be divided into the next two parts: - find the most general type of the word we are trying to complete that will satisfy the type checker - find all the symbols that "match" the found type The first task can be solved using ghc. Just replace the word with "()" and ghc will tell you something like Couldn't match expected type `m String' against inferred type `()' The second task can be solved using hoogle. Just ask it to find everything that matches "base :: type", where base -- already known part of the word; type -- the type that ghc expects. Source code is attached (linux only at a moment) haskell.vim -- very basic ftplugin for vim Place it into your ~/.vim/ftplugin directory (don't forget to backup an existent file if any) complete.hs -- simple script that does actual work. How to use it. cd to the cabal package you are working on at a moment mkdir dist/hscomplete copy complete.hs file to the dist/hscomplete edit complete.hs (at least change the package name, it is hard coded) create hoogle database for your package: cabal haddock --hoogle hoogle --convert=dist/doc/html/<packageName>/<packageName>.hoo +base +directory +... (all packages you depend on) start vim (you should be in the directory where <package>.cabal file is placed!) Use C-X C-O to auto complete Example: cabalized package "tmp" contains two modules Data.Tmp and Data.Tmp1 Data.Tmp1 imports Data.Tmp Data/Tmp.hs contains veryLongLongName1 :: Int veryLongLongName1 = 1 veryLongLongName2 :: Char veryLongLongName2 = 'c' veryLongLongName3 :: String veryLongLongName3 = "Hello" vim src/Data/Tmp1.hs import Data.Tmp tmp1 :: Monad m => [a] -> m Int tmp1 a = very<C-x C-O> suggests veryLongLongName1 tmp2 :: Monad m => [a] -> m Char tmp2 a = very<C-x C-O> suggests veryLongLongName2 and veryLongLongName3 tmp3 :: Monad m => [a] -> m String tmp3 a = very<C-x C-O> suggests veryLongLongName3 Warning: not ready for real use (no error handling, a lot of hard codes, slow, etc). Just for playing Yuras

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Crypto-API is stabilizing
by Thomas DuBuisson 05 Sep '10

05 Sep '10

All, Crypto-API - a unified interface to which I hope hash and cipher algorithms will adhere - has recently gotten a reasonable amount of polish work. I continue to welcome all comments! A blog on its current interface is online [1] as are darcs repositories of the crypto-api package [2]. Recent changes includes added block cipher modes, platform-independent RNG, tests, a simplistic benchmark framework, and minor tweaks of the classes. I've made experimental hash, block cipher and stream cipher instances. Almost no optimizations have been made as of yet! Thanks to everyone for their past comments! I have made numerous changes based on input received. If you feel I didn't respond properly to your suggestion then please ping me again - this is purely a spare time effort and things do fall through the cracks. Cheers, Thomas [1] http://tommd.wordpress.com/2010/08/23/a-haskell-api-for-cryptographic-algor… [2] http://community.haskell.org/~tommd/crypto/ (If you're wondering why you're BCCed its probably because you worked on a crypto-related Haskell package)

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help me evangelize haskell
by Leonel Fonseca 05 Sep '10

05 Sep '10

Michael: Hi. I take the risk to mention some facts you might already be working on. I speculate on three perceptions in the mind of decision makers related to the adoption of a new language in a shop. This perceptions can be modified in stages. First Stage: Awareness. Why programming in that language matters? Once you can justified this, advance to the following stage. Haskell is nice, quick to develop, brings tools to make abstractions at any level and has tools and libraries. And community support is really awesome! If you invest more in learning, you can strive to use it as formal programming method and earn safety guarantees. Please, see elsewere for success stories that help you to motivate and encourage management to test the new alternative. Second Stage: Small term engagment. Why your shop should do little investment in trying a new language in a small but representative project? Here you can make two arguments to gain support in this stage: 2.A) The shortcommings of the current tools/languages. 2.B) Small concept programs of how your current language/tool would fail where the new one would success. You can gain credibility by showing how your new tool could be short on some aspect that it's well mastered in the old one. (i.e. be impartial). Someone has already pointed how fragile interpreted programs are. In this stage you must gain both decision makers and peers recognition of the problem the shop is facing with the current language versus the improvements of using the new language. A project must be acomplished and reviewed, so a decision can be made over the facts of costs and benefits. Third Stage: Adoption. Is it really better to adopt a new language? At this point you have evidence of possible benefits and costs. And a decision is made. Among other costs, please take in account that embracing any new language in a shop will require formalised (funded, time alloted to, machines, any other resource) learning and coaching activities. Haskell has long learning curve. And you must consider this cost of being less productive than in your current language. There's too the risk of hitting walls in a tight-schedule situation. You can lower this risk of failure if you arrange to have a mentor (master) who can lead, provide hints to co-workers, discuss approaches and solve hard issues whenever they appear. Counter-arguments that you must deal with: c1) Why not... Erlang? F#? See Jon Harrop's claims. Scala or Clojure? c2) Performance predictability. c3) On the fly script generation and execution. c4) Will your co-workers be happy of embracing a new paradigm of solving problems? Will type signatures appear as pain or a valuable thing to them? -- Leonel Fonseca.

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Why does ghci recompile the module compiled in different OS ?
by zaxis 05 Sep '10

05 Sep '10

Both linux and freebsd has the same .ghci file. >cat ~/.ghci :def hoogle \str -> return $ ":! hoogle --count=15 \"" ++ str ++ "\"" :cd /media/G/www/qachina/db/doc/money the money.hs has many functions i need to use. On freebsd, i use the following command to compile it: >ghc -c -O2 money.hs >ls Money.hi Money.hs Money.o When entering ghci, it indeed doesnot recompile the module. >ghci ... Ok, modules loaded: Money However, when i use the same module in archlinux, the ghci does recompile the module: >ghci ... [1 of 1] Compiling Money ( Money.hs, interpreted ) Ok, modules loaded: Money. Any suggestion is appreciated! ----- e^(π⋅i) + 1 = 0 -- View this message in context: http://old.nabble.com/Why-does-ghci-recompile-the-module-compiled-in-differ… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Haskell Platform on Windows - cabal update problems.
by Serguey Zefirov 05 Sep '10

05 Sep '10

I've installed recent Haskell Platform and tried to wrap my head around cabal to finally figure out how to use it. First thing I bumped into is that cabal.exe does not know about any remote repositories, even about hackage. So after googling I found that I should add a line "remote-repo: hackage.haskell.org:http://hackage.haskell.org/packages/archive" into my cabal config file. So I did. And now I have "cabal update" command trying to download packages list from hackage. To no avail. Now it gives me even more interesting error: "cabal.EXE: fromFlag NoFlag. Use fromFlagOrDefault" Googling doesn't help here. What does it mean and how to get rid of it?

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New .hs File Icons
by Christian Eltges 05 Sep '10

05 Sep '10

Hello, I was wondering why the File-Icon installed by GHC with the lambda for .hs files hasn't changed to the new bind+lambda icon used on haskel.org. Is this because it should be the same as the icon used by hugs? I've created a new icon myself, which I use on my pc (using the svg file from the haskell wiki). So if the only reason for using the old icon was, that there is no new one, then you can use this. Best regards Christian

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