- Haskell-Cafe - Haskell.org

Benchmarks game updated to ghc 6.12.2
by Isaac Gouy 05 May '10

05 May '10

Ketil Malde <ketil at malde.org> writes: > As for code size, the programs are heavily tuned for speed. iirc there was a community effort 2 or 3 years ago, but now ghc has changed enough that the compiler and runtime parameters seem to need re-tuning. > Is it an idea to go back a few steps to more idiomatic code? Perhaps as a separate "track"? There's always room for 2 or 3 Haskell programs per task - not necessarily The Good, the Bad and the Ugly - but you'll already find the cliched example of a faster more convoluted Haskell program and a more concise but slower Haskell program. (Idiomatic code? Aren't there idioms for writing fast Haskell too?) > I also worry a bit that source code optimization for a specific > compiler makes it more difficult to take advantage of compiler > optimization improvements. These are tiny tiny programs - when those compiler optimization improvements arrive re-write the programs to take advantage of them ;-)

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ANNOUNCE: happstack 0.5.0
by Jeremy Shaw 05 May '10

05 May '10

(Note: Reply-to is set to haskell-cafe(a)haskell.org) Hello, I am very pleased to announce Happstack 0.5.0. It should install cleanly from hackage via: cabal install happstack If it does not, please report errors to the happstack mailing list: http://groups.google.com/group/HAppS (You will, unfortunately, need to be subscribed due to SPAM issues). Here are the official release notes: Release Notes: This release should fix many (hopefully all) known cabal install related issues. It also includes many other improvements detailed below. Known issues: * dropped support for GHC 6.8. GHC 6.10 and 6.12 currently supported. * happstack-data compiled with -O0 due to bug in cabal http://thread.gmane.org/gmane.comp.lang.haskell.cafe/69215 You may be able to change that to -O2 if you first do: cabal install --reinstall syb-with-class --disable-documentation But we need a solution that works automatically when people run, cabal install happstack. Changes since 0.4.1: * many IxSet improvements by Gracjan Polak - hide IxSet constructor. use ixSet instead. - improved efficiency of gteTLE, getGTE, and getRange - get rid of Dynamic, just use Data.Typeable (internal change) - added deleteIx - Eq and Ord instances for IxSet - removed a bunch of cruft - greatly improved documentation - added stats function - Protect user from using unindexed keys in searches in IxSet - Runtime safeguard for badly formed inferIxSet indexes - Fixed IxSet Default instance - More detailed error messages in IxSet * work around bug in bytestring which causes the server to hang (http://hackage.haskell.org/trac/ghc/ticket/3808) * support for uincode Text and lazy Text types - Serialize/Version instances now provided automatically by happstack-data - instances of EmbedAsChild and EmbedAsAttr for Text for Identity, IdentityT, ServerPartT, and WebT. - patches sent upstream to HSP, waiting on acceptance * Added Serialize/Version instances for time / Data.Time library * Improvements to GuestBook demo by Gracjan Polak - better handling of Ctrl-C - simplified .cabal to only build executable * Improvements to GuestBook demo by Gracjan Polak - nice command line interface with help message and version information - restructured parsing of command line to make it scale better with further parameters - added reference to Paths_guestbook module to enable incorporating version and path information generated by cabal. - added withLogger transformer guaranteeing clean setup and teardown of loggers - Added clean shutdown to logging component. * fail instance for WebT now includes location of pattern match failure. e.g. src\AppControl.hs:43:24: Pattern match failure in do expression * added expireCookie function * Improvements to documentation * Additional test cases * Fixes many build failures * Experimental: Added proof of concept port of happstack-server to WAI. http://www.haskell.org/pipermail/haskell-cafe/2010-March/ 074142.html * added 'dirs' guard. (Similar to dir, but for a list of path components). * set SO_KEEPALIVE so that dropped connections will eventually time out * happstack-util only depends on QuickCheck when compiled with -ftests. This is wrong but solves a lot of annoy install failures. * file serve functions now use MonadPlus instead of setting explicit 404 * XMLMetaData for webHSP * Allow colons in cookie names Contributors: A big thanks to everyone who contributed patches for this release, including: Gracjan Polak (25 patches in this release!) Simon Meier Paulo Tanimoto Joachim Fasting Antoine Latter Simon Michael Adam Vogt Joe Edmonds Andrea Vezzosi Nils Schweinsberg

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Anglohaskell preparations?
by Philippa Cowderoy 05 May '10

05 May '10

Hi everyone. It's just over three months until the traditional time for Anglohaskell, so I wanted to ask: is anyone willing to step up and run it this year? We had a volunteer at last year's event, but I've forgotten who. It was also suggested that emails about the organisation and planning of the event be sent to the Hackathon mailing list, though it might be an idea to keep this thread on -cafe for now. If the event's going to run, we really need to try for dates and a venue in the next month or so. It's been a great event in previous years, and I'd love for it to happen again! -- flippa(a)flippac.org

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Re: Learning about Programming Languages (specifically Haskell)
by Samuel Williams 05 May '10

05 May '10

Also, one more thing - if someone could write some comments to go along with the source code that explain what it is doing, that would be really helpful. I can see the general structure, but I don't know the ins and outs of Haskell. If someone could augment the example with comments explaining what the functions do that would be great! data Door = Open | Closed deriving Show toggle Open = Closed toggle Closed = Open pass k = zipWith ($) (cycle $ replicate k id ++ [toggle]) run n = foldl (flip pass) (replicate n Closed) [0..n] Do I need to add run 100 to the end of the example for it to actually do something?

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ANNOUNCE: happstack-hamlet: compile-time HTML templates for the Haskell application server stack
by Jeremy Shaw 05 May '10

05 May '10

Hello, I am pleased to announce the availability of happstack-hamlet: http://hackage.haskell.org/package/happstack-hamlet http://patch-tag.com/r/mae/happstack/snapshot/current/content/pretty/happst… Happstack is a web application development framework. Hamlet provides HTML templates which are checked for correctness at compile time. This package add support for using Hamlet templates with Happstack. A simple demo is available here: http://patch-tag.com/r/mae/happstack/snapshot/current/content/pretty/happst… Please report any issues with the happstack-hamlet package itself to the happs mailing list (You will need to be subscribed): http://groups.google.com/group/happs Big thanks to Michael Snoyman for writing Hamlet! Hamlet homepage: http://docs.yesodweb.com/hamlet/ Happstack homepage: http://www.happstack.com/ happy hacking! - jeremy p.s. Reply-to is set to haskell-cafe

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Installing ghc in an OpenSolaris Zone
by Günther Schmidt 05 May '10

05 May '10

Hello, has anyone yet managed to install ghc (6.10.4) into an OpenSolaris zone? Günther

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Cabal-install: bus error
by Chris Eidhof 04 May '10

04 May '10

Hey everyone, After I upgraded to a newer cabal-install my cabal-install broke again: I get a Bus Error when doing "cabal update" or "cabal install something". The version that was bundled with the Haskell platform worked fine, but now it's broken again. I'm not sure what it was that went wrong or how to debug this. The previous time I had Bus Errors I upgraded to the newest available Haskell Platform release and started from scratch. I would prefer not to do that again. However, I don't really know how to solve the Bus Error. Does anyone have a clue where to start? Or is there a way to undo my cabal-install upgrade? -chris

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gtk2hs for 2010.1.0.0
by Maciej Piechotka 04 May '10

04 May '10

Does anyone have installer for gtk2hs for Haskell Platform 2010.1.0.0? Regards

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Re: Haskell and scripting
by Pierre-Etienne Meunier 04 May '10

04 May '10

Hi, You do not need a DSL at all, in fact. The simplest way to do this, if you use GHC, is to use the GHC api. This can compile everything for you, and return a value with type "Dynamic", from Data.Dynamic and Data.Typeable. It is type-safe, you can write within very little time (even if the documentation for the GHC api is not -- yet -- perfect), and use a real language whose users are still alive. Cheers, PE ps : by the way, if you are interested by this kind of programming, I saw that someone was writing a shell in haskell, called hashell I think. If you want to help him... > Hello Café, > > I don't know if you know > conky<http://en.wikipedia.org/wiki/Conky_%28software%29>. > It's a well-known open-source system monitor (a software that displays > information on the desktop, like CPU frequency, disk usage, network rate, > etc.). > It is quite good, but it's very descriptive, and even if you can call shell > commands it's clearly not made for being scripted. > What I would do is to make a similar system monitor, which base would be > compiled Haskell code, but that would be scriptable with some DSL, or > already existing interpreted language. > I've thought about a Lisp/Scheme language, since those languages are > functional, dynamically typed and simple (so enable a quick scripting) and > I'm not very keen on making my own DSL > > What I would like to know is: > 1) If you have other solutions > 2) How do haskellers usually script their applications

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eclipse, haskell-platform and windows. Installation problem.
by Han Joosten 04 May '10

04 May '10

Hi all I have been using an old version of eclipsepf for quite some time now on my windows machine. Recently I saw that there is a newer version, as well as a newer version of haskell. However, I am not able to get it all to work. I wonder if you are able to help me out. First, I installed the newest version of ghc by means of the haskell-platform. Then I installed git, so I was able to download the special variant of scion, as specified at http://sourceforge.net/projects/eclipsefp/files/EclipseFP%202%20branch/1.11… Then I tried to build the downloaded scion: C:\data\gitRepository\scion>runhaskell Setup.hs configure Configuring scion-0.1.0.2... Setup.hs: At least the following dependencies are missing: binary ==0.5.*, ghc-paths ==0.1.*, ghc-syb ==0.1.*, hslogger ==1.0.*, json ==0.4.*, list-tries ==0.1.*, multiset >=0.1 && <0.3, uniplate ==1.2.* As you can see, this failed. However, since I have the new cabal, that comes with the haskell platform, I figured that the above dependancies should not be a problem. So I used cabal: Cabal install binary (and then I cabal installed all other missing packages. ) All cabal install commands completed succesfully. Then, again i tried 'runhaskell setup.hs configure', but this failed again with exactly the same message as before. It seems that all packages that I installed dissapeared! I probably do something stupid, but I cannot figure out what I should do. Any help is welcome! Thanks! Han Joosten -- View this message in context: http://old.nabble.com/eclipse%2C-haskell-platform-and-windows.-Installation… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Release: rangemin-2.0
by Louis Wasserman 04 May '10

04 May '10

The original rangemin project was my first Haskell package, and definitely my first attempt at super-advanced algorithms work in Haskell. (I here define "super-advanced" as "not in MIT OpenCourseWare undergraduate algorithms lecture notes from any year.") Here's the problem: Suppose we have an array of length n. Preprocess the array in O(n) time such that we can look up the minimum element of any slice in the array in O(1) time. Coming back to this project after two years, and especially rewriting the approach with the vector package, was *spectacularly* fun. rangemin-2.0<http://hackage.haskell.org/package/rangemin>is now on Hackage, with a new API as well. The constant factor on the O(n) preprocessing is, based on criterion benchmarks, 88 milliseconds per million elements, on my 2.5GHz Ubuntu laptop, with GHC HEAD and -O2 -fvia-c -optc-O3. I've spent the past three days unsuccessfully trying to get the LLVM backend to work, because this algorithm has a *lot* of the sort of tight loops that LLVM excels at. Unfortunately, I haven't been able to install the LLVM backend, which is very disappointing. That said, GHC with the C backend is about 10x slower than an optimized C++ implementation, which is all right considering that the algorithm plays so much to C++'s strengths. (If anybody has LLVM working and would be willing to help, I'd massively appreciate it if you could benchmark both the C++ implementation -- not mine, but included in a tarball inside the rangemin distribution package -- and my implementation, with LLVM -O2. Benchmarking code is here<http://hpaste.org/fastcgi/hpaste.fcgi/view?id=25309#a25309> .) Louis Wasserman wasserman.louis(a)gmail.com http://profiles.google.com/wasserman.louis

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Building regex-posix for windows
by Станислав Черничкин 03 May '10

03 May '10

I'm having trouble building regex-posix for Windows under MinGW because MinGW does not include regex.h. As far as I know Haskell Platform uses MinGW and it includes regex-posix. I'd like to build regex-posix by myself, like Haskell Platform does. I would appreciate it if someone suggests some resources about building regex-posix and other packages for windows. I’m also looking for Haskell Platform developer’s blog or something similar, where I can read about porting Haskell on Windows. Thanks.

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Learning about Programming Languages (specifically Haskell)
by Samuel Williams 03 May '10

03 May '10

Dear Friends, I'm looking for some help from the Haskell community. I hope this is the right place to ask for information. I'm putting together a website aimed at high school students and teachers, and would like to add a few paragraphs to the following page: http://programming.dojo.net.nz/languages/haskell/index ... explaining why one would want to learn Haskell. I don't know the answer to this since I don't use Haskell extensively. What are the main application areas and how is it useful? Any other suggestions or ideas for the Haskell page would be fantastic, and any suggestions to other pages in general is also very helpful. http://programming.dojo.net.nz/ Kind regards, Samuel

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Re: FRP for game programming / artifical life simulation
by Ben 03 May '10

03 May '10

slightly off topic, but how does one handle pausing / saving / restarting in the FRP framework, especially the arrowized version? i've only been able to do this via explicit (or monadic) state-passing, e.g. imperative / piecemeal versus declarative / wholemeal, which seems against the spirit of FRP. b

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MonadPlus or Alternative or ...?
by Sean Leather 03 May '10

03 May '10

I want to generalize a set of functions from lists to some functor type. I require the following three operation types. f a a -> f a f a -> f a -> f a Should I choose MonadPlus and use these? mzero return mplus Or should I choose Alternative and use these? empty pure (<|>) Or should I make my own class? Or is there another option? Thanks, Sean

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FRP for game programming / artifical life simulation
by Ben Christy 03 May '10

03 May '10

I have an interest in both game programming and artificial life. I have recently stumbled on Haskell and would like to take a stab at programming a simple game using FRP such as YAMPA or Reactive but I am stuck. I am not certain which one I should choose. It seems that Reactive is more active but is it suitable for game programming. Also has anyone attempted to implement neural networks using FRP if so again which of these two approaches to FRP would you suggest?

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are forkIO threads event-driven?
by Aran Donohue 03 May '10

03 May '10

Hi Cafe, In GHC, if a thread spawned by forkIO blocks on some network or disk IO, is the threading system smart enough not to wake the thread until an IO event occurs on its input/output? The Control.Concurrent documentation doesn't specify, and the previous discussions I could find on this topic are out-of-date. There is a years-old GHC ticket, too, recently revived[2]. Put another way, is it possible yet to use forkIO for making a server to handle tens of thousands of concurrent network connections? If not, what is the best current Haskell/GHC way? Thanks, Aran [1] http://www.monkey.org/~provos/libevent/ [2] http://hackage.haskell.org/trac/ghc/ticket/635

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Leibniz equality can be made injective
by oleg＠okmij.org 03 May '10

03 May '10

We show that type families let us write Leibniz equality witnesses of the injectivity of type constructors. We may use Leibniz equality not only for introduction but also for elimination. The paper on ``Typing Dynamic Typing'' (Baars and Swierstra, ICFP 2002) demonstrated the first implementation and application of Leibniz equality witnesses in Haskell: > newtype EQU a b = EQU{subst:: forall c. c a -> c b} A term (eq :: EQU a b) witnesses the equality of the types a and b: in any context c, the type a can be substituted with the type b. The context is represented by the type constructor c. The witness gives the constructive prove of substitutability: given a term of the type c a, we can always obtain a term of the type c b. Since we don't know anything about the context c, such a substitution can only happen if the two types are indeed equal. Hence the sole non-bottom witness is > refl :: EQU a a > refl = EQU id testifying that equality is reflexive. Leibniz equality became quite popular since it lets us represent GADTs to a large extent. The power of Leibniz equality comes from the fact that the context c may indeed be anything we want. The following example illustrates that power, by concisely proving that the equality is transitive. The proof of transitivity is very short > tran :: EQU a u -> EQU u b -> EQU a b > tran au ub = subst ub au We treat the type EQU a u as (EQU a) u, that is, as an application of the `type constructor' (EQU a) to the type 'u'. We then use the witness EQU u b to replace the type u with the type b in the context (EQU a), giving us the desired EQU a b. When writing type checkers and type inferencers in Haskell along the lines of typing dynamic typing, we also need to know that two arrow types are equal if and only if their components are equal. In one direction, > eq_arr :: EQU a1 a2 -> EQU b1 b2 -> EQU (a1->b1) (a2->b2) if the argument and result types of two arrow types are equal, the arrow types themselves are equal. Fortunately, for this, commonly used direction, the proof is easy, after we define suitable type-level combinators F1 and F2 to place the types being equated in the right context: > newtype F1 t b a = F1{unF1:: EQU t (a->b)} > newtype F2 t a b = F2{unF2:: EQU t (a->b)} > eq_arr :: EQU a1 a2 -> EQU b1 b2 -> EQU (a1->b1) (a2->b2) > eq_arr a1a2 b1b2 = > unF2 . subst b1b2 . F2 . unF1 . subst a1a2 . F1 $ refl In the type EQU (a1->b1) (a2->b2), the type `constructor' (F1 (a1->b1) b2) represents the context of the type a2, and the type constructor (F2 (a1->b1) a2) is the context of the type b2. Leibniz equality only applies if the context of a type is represented as a type constructor; therefore, we sometimes have to define auxiliary newtypes to put the contexts in the required form. In the reverse direction, we have to prove that if two arrow types are equal, their components (e.g., the argument types) are equal as well. The proof will witness the injectivity of the arrow type constructor. It is thought that injectivity cannot be proven with Leibniz equality at all. For example, the paper ``Implementing Cut Elimination: A Case Study of Simulating Dependent Types in Haskell'' by Chen, Zhu and Xi, PADL'04, needed the reverse, elimination direction and found it impossible to obtain with Leibniz equality witnesses. We demonstrate that type families help. Type families let us define ``subtractive contexts'', so that we can view a type 'a' as the type (a->b) placed into the context that removes (->b). Again we use an auxiliary newtype to make the subtractive context appear as a type constructor. > type family Fst a :: * > type instance Fst (x->y) = x > type instance Fst (x,y) = x > -- etc. > newtype FstA a b = FstA{unFstA :: EQU (Fst a) (Fst b)} > eq_arr1 :: EQU (a1->b1) (a2->b2) -> EQU a1 a2 > eq_arr1 eq = unFstA . subst eq $ ra > where > ra :: FstA (a1->b1) (a1->b1) > ra = FstA refl The complete code is available at http://okmij.org/ftp/Haskell/LeibnizInjective.hs The code includes a simple test of the injectivity.

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Happy: PATH issue
by Limestraël 03 May '10

03 May '10

Hello Café, When I was trying to cabal-install haskell-src, I came up with: cabal: The program happy is required but it could not be found However, the happy package was actually installed and the 'happy' executable was in ~/.cabal/bin (which was in my PATH) I had to link ~/.cabal/bin/happy to /usr/bin/happy so that cabal-install may finally find it.

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Re: LLVM backend building segfault (Louis Wasserman)
by Jonathan Fischoff 03 May '10

03 May '10

I got this too, on windows. On linux I got a similiar issue, but I think the message was different. I ran the ghc stage2 with valgrind and it complained about there being an invalid instruction. I wonder if it is a 64bit thing. Anyone been able to build the LLVM backend with a 64 bit machine? -Jonathan Fischoff > Hokay, so I've installed LLVM 2.7, > gotten ghc-HEAD-2009-10-23-ghc- > corelibs.tar.bz2, run ./darcs-all pull -a, > run ./boot, applied > add-new-llvm-code-generator-to-ghc_.dpatch > ghc-llvmbackend-20100328.dpatch > and written the following in mk/build.mk: > > GhcWithLlvmCodeGen = YES > GhcEnableTablesNextToCode = NO > SRC_HC_OPTS = -H64m -O0 -fasm > GhcStage1HcOpts = -O -fasm > GhcStage2HcOpts = -O0 -fasm > GhcLibHcOpts = -O -fasm > SplitObjs = NO > HADDOCK_DOCS = NO > > And when I run make, > > make -r --no-print-directory -f ghc.mk all > "inplace/bin/ghc-stage2" -H64m -O0 -fasm -i -iutils/ghctags/. > -iutils/ghctags/dist/build -iutils/ghctags/dist/build/autogen > -Iutils/ghctags/dist/build -Iutils/ghctags/dist/build/autogen > -package ghc -no-user-package-conf -rtsopts -odir > utils/ghctags/dist/build -hidir utils/ghctags/dist/build -stubdir > utils/ghctags/dist/build -hisuf hi -osuf o -hcsuf hc -c > utils/ghctags/./Main.hs -o utils/ghctags/dist/build/Main.o > "inplace/bin/ghc-stage2" -H64m -O0 -fasm -package-name dph-base-0.4.0 > -hide-all-packages -i -ilibraries/dph/dph-base/. > -ilibraries/dph/dph-base/dist-install/build > -ilibraries/dph/dph-base/dist-install/build/autogen > -Ilibraries/dph/dph-base/dist-install/build > -Ilibraries/dph/dph-base/dist-install/build/autogen > -Ilibraries/dph/dph-base/include -optP-include > -optPlibraries/dph/dph-base/dist-install/build/autogen/cabal_macros.h > -package array-0.3.0.0 -package base-4.2.0.0 -package ghc-prim-0.2.0.0 > -package random-1.0.0.2 -Odph -funbox-strict-fields -haddock -fcpr-off > -XTypeFamilies -XGADTs -XRankNTypes -XBangPatterns -XMagicHash > -XUnboxedTuples -XTypeOperators -O -fasm -fno-warn-deprecated-flags -Wwarn > -odir libraries/dph/dph-base/dist-install/build -hidir > libraries/dph/dph-base/dist-install/build -stubdir > libraries/dph/dph-base/dist-install/build -hisuf hi -osuf o -hcsuf hc -c > libraries/dph/dph-base/./Data/Array/Parallel/Base/DTrace.hs -o > libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/DTrace.o > "inplace/bin/ghc-stage2" -H64m -O0 -fasm -package-name dph-base-0.4.0 > -hide-all-packages -i -ilibraries/dph/dph-base/. > -ilibraries/dph/dph-base/dist-install/build > -ilibraries/dph/dph-base/dist-install/build/autogen > -Ilibraries/dph/dph-base/dist-install/build > -Ilibraries/dph/dph-base/dist-install/build/autogen > -Ilibraries/dph/dph-base/include -optP-include > -optPlibraries/dph/dph-base/dist-install/build/autogen/cabal_macros.h > -package array-0.3.0.0 -package base-4.2.0.0 -package ghc-prim-0.2.0.0 > -package random-1.0.0.2 -Odph -funbox-strict-fields -haddock -fcpr-off > -XTypeFamilies -XGADTs -XRankNTypes -XBangPatterns -XMagicHash > -XUnboxedTuples -XTypeOperators -O -fasm -fno-warn-deprecated-flags -Wwarn > -odir libraries/dph/dph-base/dist-install/build -hidir > libraries/dph/dph-base/dist-install/build -stubdir > libraries/dph/dph-base/dist-install/build -hisuf hi -osuf o -hcsuf hc -c > libraries/dph/dph-base/./Data/Array/Parallel/Base/Hyperstrict.hs -o > > libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/Hyperstrict.o > Segmentation fault > make[1]: *** > > [libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/Hyperstrict.o] > Error 139 > make[1]: *** Waiting for unfinished jobs.... > Segmentation fault > make[1]: *** [utils/ghctags/dist/build/Main.o] Error 139 > Segmentation fault > make[1]: *** > > [libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/DTrace.o] > Error 139 > make: *** [all] Error 2 > > I get segfaults. Segfaults make me unhappy. Halp plz? > > Louis Wasserman > wasserman.louis(a)gmail.com > http://profiles.google.com/wasserman.louis >

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Problems with HStringTemplate UTF8 templates in ghc-6.12
by Dmitry Simonchik 03 May '10

03 May '10

Hi all, I need your help I have something i can't understand with hstringtemplate. I'm using this library in my project to render UTF-8 encoded templates. Everything was fine when I were using ghc-6.10 and hstringtemplate-0.6.1 But recently I upgraded to ghc-6.12 and hstringtemplate-0.6.2 and the output of my program now broken. I can see correctly only UTF8 values that I pass to template from database. It seems that toString method produces not UTF-8 encoded string, because if i use Codec.Binary.UTF8.String.encodeString i get correct output except for values from database. Any ideas how to solve the problem?

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LLVM backend building segfault
by Louis Wasserman 02 May '10

02 May '10

Hokay, so I've installed LLVM 2.7, gotten ghc-HEAD-2009-10-23-ghc-corelibs.tar.bz2, run ./darcs-all pull -a, run ./boot, applied add-new-llvm-code-generator-to-ghc_.dpatch ghc-llvmbackend-20100328.dpatch and written the following in mk/build.mk: GhcWithLlvmCodeGen = YES GhcEnableTablesNextToCode = NO SRC_HC_OPTS = -H64m -O0 -fasm GhcStage1HcOpts = -O -fasm GhcStage2HcOpts = -O0 -fasm GhcLibHcOpts = -O -fasm SplitObjs = NO HADDOCK_DOCS = NO And when I run make, make -r --no-print-directory -f ghc.mk all "inplace/bin/ghc-stage2" -H64m -O0 -fasm -i -iutils/ghctags/. -iutils/ghctags/dist/build -iutils/ghctags/dist/build/autogen -Iutils/ghctags/dist/build -Iutils/ghctags/dist/build/autogen -package ghc -no-user-package-conf -rtsopts -odir utils/ghctags/dist/build -hidir utils/ghctags/dist/build -stubdir utils/ghctags/dist/build -hisuf hi -osuf o -hcsuf hc -c utils/ghctags/./Main.hs -o utils/ghctags/dist/build/Main.o "inplace/bin/ghc-stage2" -H64m -O0 -fasm -package-name dph-base-0.4.0 -hide-all-packages -i -ilibraries/dph/dph-base/. -ilibraries/dph/dph-base/dist-install/build -ilibraries/dph/dph-base/dist-install/build/autogen -Ilibraries/dph/dph-base/dist-install/build -Ilibraries/dph/dph-base/dist-install/build/autogen -Ilibraries/dph/dph-base/include -optP-include -optPlibraries/dph/dph-base/dist-install/build/autogen/cabal_macros.h -package array-0.3.0.0 -package base-4.2.0.0 -package ghc-prim-0.2.0.0 -package random-1.0.0.2 -Odph -funbox-strict-fields -haddock -fcpr-off -XTypeFamilies -XGADTs -XRankNTypes -XBangPatterns -XMagicHash -XUnboxedTuples -XTypeOperators -O -fasm -fno-warn-deprecated-flags -Wwarn -odir libraries/dph/dph-base/dist-install/build -hidir libraries/dph/dph-base/dist-install/build -stubdir libraries/dph/dph-base/dist-install/build -hisuf hi -osuf o -hcsuf hc -c libraries/dph/dph-base/./Data/Array/Parallel/Base/DTrace.hs -o libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/DTrace.o "inplace/bin/ghc-stage2" -H64m -O0 -fasm -package-name dph-base-0.4.0 -hide-all-packages -i -ilibraries/dph/dph-base/. -ilibraries/dph/dph-base/dist-install/build -ilibraries/dph/dph-base/dist-install/build/autogen -Ilibraries/dph/dph-base/dist-install/build -Ilibraries/dph/dph-base/dist-install/build/autogen -Ilibraries/dph/dph-base/include -optP-include -optPlibraries/dph/dph-base/dist-install/build/autogen/cabal_macros.h -package array-0.3.0.0 -package base-4.2.0.0 -package ghc-prim-0.2.0.0 -package random-1.0.0.2 -Odph -funbox-strict-fields -haddock -fcpr-off -XTypeFamilies -XGADTs -XRankNTypes -XBangPatterns -XMagicHash -XUnboxedTuples -XTypeOperators -O -fasm -fno-warn-deprecated-flags -Wwarn -odir libraries/dph/dph-base/dist-install/build -hidir libraries/dph/dph-base/dist-install/build -stubdir libraries/dph/dph-base/dist-install/build -hisuf hi -osuf o -hcsuf hc -c libraries/dph/dph-base/./Data/Array/Parallel/Base/Hyperstrict.hs -o libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/Hyperstrict.o Segmentation fault make[1]: *** [libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/Hyperstrict.o] Error 139 make[1]: *** Waiting for unfinished jobs.... Segmentation fault make[1]: *** [utils/ghctags/dist/build/Main.o] Error 139 Segmentation fault make[1]: *** [libraries/dph/dph-base/dist-install/build/Data/Array/Parallel/Base/DTrace.o] Error 139 make: *** [all] Error 2 I get segfaults. Segfaults make me unhappy. Halp plz? Louis Wasserman wasserman.louis(a)gmail.com http://profiles.google.com/wasserman.louis

1 0

WGP 2010 Second Call for Papers (Apologies for multiple copies)
by Bruno Oliveira 02 May '10

02 May '10

====================================================================== CALL FOR PAPERS WGP 2010 6th ACM SIGPLAN Workshop on Generic Programming Baltimore, Maryland, US Sunday, September 26th, 2010 http://osl.iu.edu/wgp2010 Collocated with the International Conference on Functional Programming (ICFP 2010) ====================================================================== Goals of the workshop --------------------- Generic programming is about making programs more adaptable by making them more general. Generic programs often embody non-traditional kinds of polymorphism; ordinary programs are obtained from them by suitably instantiating their parameters. In contrast with normal programs, the parameters of a generic program are often quite rich in structure; for example they may be other programs, types or type constructors, class hierarchies, or even programming paradigms. Generic programming techniques have always been of interest, both to practitioners and to theoreticians, and, for at least 20 years, generic programming techniques have been a specific focus of research in the functional and object-oriented programming communities. Generic programming has gradually spread to more and more mainstream languages, and today is widely used in industry. This workshop brings together leading researchers and practitioners in generic programming from around the world, and features papers capturing the state of the art in this important area. We welcome contributions on all aspects, theoretical as well as practical, of * polytypic programming, * programming with dependent types, * programming with type classes, * programming with (C++) concepts, * generic programming, * programming with modules, * meta-programming, * adaptive object-oriented programming, * component-based programming, * strategic programming, * aspect-oriented programming, * family polymorphism, * object-oriented generic programming, * and so on. Organizers ---------- Co-Chair Bruno C. d. S. Oliveira, Seoul National University Co-Chair Marcin Zalewski, Indiana University Programme Committee ------------------- Alley Stoughton, Kansas State University Andrei Alexandrescu, Facebook Bruno C. d. S. Oliveira (Co-Chair), Seoul National University Doug Gregor, Apple Gilad Bracha, I am a Computational Theologist Emeritus Magne Haveraaen, Universitetet i Bergen Marcin Zalewski (Co-Chair), Indiana University Neil Mitchell, Standard Chartered Ralf Lämmel, University of Koblenz-Landau Shin-Cheng Mu, Academia Sinica Thorsten Altenkirch, University of Nottingham Ulf Norell, Chalmers University Important Information --------------------- We plan to have formal proceedings, published by the ACM. Submission details Deadline for submission: Sunday 2010-06-13 Notification of acceptance: Monday 2010-07-12 Final submission due: Tuesday 2010-07-27 Workshop: Sunday 2010-09-26 Authors should submit papers, in postscript or PDF format, formatted for A4 paper, to the WGP09 EasyChair instance by 13th of June 2010. The length should be restricted to 12 pages in standard (two-column, 9pt) ACM format. Accepted papers are published by the ACM and will additionally appear in the ACM digital library. History of the Workshop on Generic Programming ---------------------------------------------- This year: * Baltimore, Maryland, US 2010 (affiliated with ICFP10) Earlier Workshops on Generic Programming have been held in * Edinburgh, UK 2009 (affiliated with ICFP09) * Victoria, BC, Canada 2008 (affiliated with ICFP), * Portland 2006 (affiliated with ICFP), * Ponte de Lima 2000 (affiliated with MPC), * Marstrand 1998 (affiliated with MPC). Furthermore, there were a few informal workshops * Utrecht 2005 (informal workshop), * Dagstuhl 2002 (IFIP WG2.1 Working Conference), * Nottingham 2001 (informal workshop), There were also (closely related) DGP workshops in Oxford (June 3-4 2004), and a Spring School on DGP in Nottingham (April 24-27 2006, which had a half-day workshop attached). Additional information: The WGP steering committee consists of J Gibbons, R Hinze, P Jansson, J Jarvi, J Jeuring, B Oliveira, S Schupp and M Zalewski

1 0

Haskell Jaskell Interface?
by John Creighton 02 May '10

02 May '10

I was wondering if a good approach to java interoperability might be a Haskell Jaskell Interface. Jaskell allows some haskell programs to run on the java virtual machine and dealt with some of the issues with regards to interfacing haskell with java on the virtual machine side of things. Therefore if their was say a GHC bridge between haskell and jaskell their would be two similar languages talking to each other. Code ment to be more closely coupled with java could be coded in jaskell and code that requires say GHC extensions could be written in haskell and perhaps some io interface between the two languages.

1 0

FGL instance constraint
by Kevin Quick 02 May '10

02 May '10

I need help understanding how to express the following: > data (Cls a) => B a = B [a] > data GrB a b = GrB (B a) > instance Graph GrB where ... In the methods for the instance specification, I need to perform Cls a operations on a. * As shown, the compiler complains that it cannot deduce (Cls a) from the context () on those methods. * I can't redefine the Graph methods to introduce the (Cls a) constraint [reasonable] * If I try to express the constraint as part of the Graph instance: "instance (Cls a) => Graph GrB where ..." then it says it's an ambiguous constraint because 'a' isn't mentioned. * I've tried specifying a functional constraint: "instance (Cls a) => Graph GrB | GrB -> a where ..." but that's not valid for an instance declaration. * I can't include a in the GrB instance: "instance (Cls a) => Graph (GrB a b) where ..." because that's a kind conflict. Suggestions/solutions are appreciated. Thanks! -- -KQ

6 22

Build problems (hsp, trhsx, ultimately Happstack)
by Alexander Solla 02 May '10

02 May '10

Consider the following bash session: [ ajs@kizaru:~/ ]$ which trhsx /home/ajs/.cabal/bin/trhsx [ ajs@kizaru:~/ ]$ trhsx Usage: trhsx <infile> [<outfile>] [ ajs@kizaru:~/ ]$ cabal install hsp Resolving dependencies... Configuring hsp-0.4.5... Preprocessing library hsp-0.4.5... Building hsp-0.4.5... ghc: could not execute: trhsx cabal: Error: some packages failed to install: hsp-0.4.5 failed during the building phase. The exception was: ExitFailure 1 Does anybody have any suggestions? I'm trying to install Happstack on Arch Linux (GHC 6.12.1). ~/.cabal/bin/ is in my path and trhsx runs. I've had this problem before, and I think I ran cabal as root for the HSP package. That's not working this time. I get the same failure.

7 19

Benchmarks game updated to ghc 6.12.2
by Don Stewart 02 May '10

02 May '10

The benchmarks game has been updated to use 6.12.2 Please dive in and help tweak/improve/spot any regressions. Esp. with respect to multicore flags/options/... ----- Forwarded message from Isaac Gouy ----- Subject: fyi benchmarks game updated to ghc 6.12.2 http://shootout.alioth.debian.org/u64q/haskell.php best wishes, Isaac ----- End forwarded message -----

6 9

GTKHS mailing list:
by John Creighton 02 May '10

02 May '10

Something needs to be done about the GTKhs mailing list. It is flooded with spam that no one would want coming to their in box: http://haskell.org/pipermail/gtkhs/

1 0

Functional Dependencies Help
by John Creighton 02 May '10

02 May '10

I've been trying to apply some stuff I learned about functional dependencies, but I run into one of two problems. I either end up with inconsistent dependencies (OverlappingInstances doesn't seem to apply) or I end up with infinite recursion. I want to be able to do simple things like if a is a subset of b and b is a subset of c then a is a subset of c. If a is a is a subset of b and b is a c then a is a c. Before I added the equality functions I had infinite recursion. Once I put them them in then I have trouble with overlapping isntances. {-# LANGUAGE TypeOperators #-} {-# LANGUAGE OverlappingInstances #-} {-# LANGUAGE UndecidableInstances #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE FunctionalDependencies #-} {-# LANGUAGE FlexibleInstances #-} {-# LANGUAGE FlexibleContexts #-} data Noun = Noun deriving (Show) --10 data Verb = Verb deriving (Show) -- data Adjactive = Adjactive deriving (Show) data Animal=Animal deriving (Show) data Feline=Feline deriving (Show) data Cat = Cat deriving (Show) data Taby_Cat=Taby_Cat deriving (Show) data T=T deriving (Show) data F=F deriving (Show) --20 class Isa a b c | a b->c where isa::a->b->c instance Isa Animal Noun T where isa a b = T --25 class IsSuperSet a b c | a b->c where isSuperSet :: a->b->c instance IsSuperSet Feline Cat T where --30 isSuperSet a b=T instance IsSuperSet Animal Feline T where isSuperSet a b=T instance IsSuperSet a Animal F where isSuperSet a b=F --35 class TypeNotEq d b c | d b->c where typeNotEq :: a->b->c instance (IsSuperSet d b c, --40 IsSuperSet a d c, TypeNotEq a d T, TypeNotEq b d T, TypeEq c T T )=> IsSuperSet a b c where isSuperSet a b=undefined::c instance TypeNotEq a a c where typeNotEq a b = undefined::c --50 instance TypeNotEq a b c where typeNotEq a b = undefined::c class TypeEq a b c | a b->c where typeEq :: a->b->c instance TypeEq a a c where typeEq a b = undefined::c instance TypeEq a b c where typeEq a b = undefined::c class ToBool a where toBool :: a->Bool instance ToBool T where toBool a = True instance ToBool F where toBool a = False myCat=Cat bla=isSuperSet Animal Cat

1 3

Asynchronous exception wormholes kill modularity
by Bas van Dijk 01 May '10

01 May '10

Dear all, (sorry for this long mail) When programming in the IO monad you have to be careful about asynchronous exceptions. These nasty little worms can be thrown to you at any point in your IO computation. You have to be extra careful when doing, what must be, an atomic transaction like: do old <- takeMVar m new <- f old `onException` putMVar m old putMVar m new If an asynchronous exception is thrown to you right after you have taken your MVar the putMVar will not be executed anymore and will leave your MVar in the empty state. This can possibly lead to dead-lock. The standard solution for this is to use a function like modifyMVar_: modifyMVar_ :: MVar a -> (a -> IO a) -> IO () modifyMVar_ m io = block $ do a <- takeMVar m a' <- unblock (io a) `onException` putMVar m a putMVar m a' As you can see this will first block asynchronous exceptions before taking the MVar. It is usually better to be in the blocked state as short as possible to ensure that asynchronous exceptions can be handled as soon as possible. This is why modifyMVar_ unblocks the the inner (io a). However now comes the problem I would like to talk about. What if I want to use modifyMVar_ as part of a bigger atomic transaction. As in: block $ do ... modifyMVar_ m f ... >From a quick glanse at this code it looks like asynchronous exceptions can't be thrown to this transaction because we block them. However the unblock in modifyMVar_ opens an asynchronous exception "wormhole" right into our blocked computation. This destroys modularity. Besides modifyMVar_ the following functions suffer the same problem: * Control.Exception.finally/bracket/bracketOnError * Control.Concurrent.MVar.withMVar/modifyMVar_/modifyMVar * Foreign.Marshal.Pool.withPool We can solve it by introducing two handy functions 'blockedApply' and 'blockedApply2' and wrapping each of the operations in them: > import Control.Exception > import Control.Concurrent.MVar > import Foreign.Marshal.Pool > import GHC.IO ( catchAny ) > blockedApply :: IO a -> (IO a -> IO b) -> IO b > blockedApply a f = do > b <- blocked > if b > then f a > else block $ f $ unblock a > blockedApply2 :: (c -> IO a) -> ((c -> IO a) -> IO b) -> IO b > blockedApply2 g f = do > b <- blocked > if b > then f g > else block $ f $ unblock . g Control.Exception: > finally :: IO a -> IO b -> IO a > a `finally` sequel = blockedApply a $ \a' -> do > r <- a' `onException` sequel > _ <- sequel > return r > bracket :: IO a-> (a -> IO b) -> (a -> IO c) -> IO c > bracket before after thing = blockedApply2 thing $ \thing' -> do > a <- before > r <- thing' a `onException` after a > _ <- after a > return r > bracketOnError :: IO a -> (a -> IO b) -> (a -> IO c) -> IO c > bracketOnError before after thing = blockedApply2 thing $ \thing' -> do > a <- before > thing' a `onException` after a Control.Concurrent.MVar: > withMVar :: MVar a -> (a -> IO b) -> IO b > withMVar m io = blockedApply2 io $ \io' -> do > a <- takeMVar m > b <- io' a `onException` putMVar m a > putMVar m a > return b > modifyMVar_ :: MVar a -> (a -> IO a) -> IO () > modifyMVar_ m io = blockedApply2 io $ \io' -> do > a <- takeMVar m > a' <- io' a `onException` putMVar m a > putMVar m a' > modifyMVar :: MVar a -> (a -> IO (a,b)) -> IO b > modifyMVar m io = blockedApply2 io $ \io' -> do > a <- takeMVar m > (a',b) <- io' a `onException` putMVar m a > putMVar m a' > return b Foreign.Marshal.Pool: > withPool :: (Pool -> IO b) -> IO b > withPool act = blockedApply2 act $ \act' -> do > pool <- newPool > val <- catchAny > (act' pool) > (\e -> do freePool pool; throw e) > freePool pool > return val I'm not proposing to make this change (yet) because I first would like to have some discussion on this. Thanks for reading this rather long mail, Bas

13 46

Location of library documentation with 6.12.1?
by Roly Perera 01 May '10

01 May '10

Hi, I've just upgraded from 6.10.1 to 6.12.1 and can't seem to find all the library documentation. This page is apparently the documentation root: http://www.haskell.org/ghc/docs/6.12.1/html/ but if I click through to the Haskell Hierarchical Libraries page http://www.haskell.org/ghc/docs/6.12.1/html/libraries/index.html I can't for example find Control.Monad.State. I guess I'm missing something obvious about how things are organised? thanks in advance, Roly

4 6

Typing Haskell in Haskell
by Aaron Gray 01 May '10

01 May '10

Hi, I am relatively new to Haskell. I am attempting to get "Typing Haskell in Haskell" to work on HUGS or GHC. http://web.cecs.pdx.edu/~mpj/thih/ I am getting an error on loading SourcePrelude :- Hugs> :l SourcePrelude ERROR ".\PPrint.hs" - Can't find imported module "Pretty" And I cannot find a Pretty module, the module and "Language.Haskell.Pretty" does not seem to be what is required. Any help welcome, Aaron

3 2

profiling uniplate
by Ozgur Akgun 01 May '10

01 May '10

Hi all, I have a code which makes use of the uniplate package. When I try to compile with profiling enabled, I get the following error: $$ ghc --make -O2 -prof -auto-all test.hs test.hs:10:7: Could not find module `Data.Generics.Uniplate.Data': Perhaps you haven't installed the profiling libraries for package `uniplate-1.5.1'? Use -v to see a list of the files searched for. And of course I do have uniplate installed, and everything works fine if I don't compile with profiling enabled. I guess I either need to install profiling libraries for uniplate, or disable profiling of those functions coming from uniplate. Any suggestion is welcome. Best, -- Ozgur Akgun

3 3

Fwd: [Haskell-cafe] Re: Simple game: a monad for each player
by Limestraël 01 May '10

01 May '10

Okay, I just understood that 'Prompt' was just a sort of view for 'Program'. >I'd like to make it very accessible, so please don't hesitate to report >any difficulties with finding and understanding documentation and examples! Then I think the name 'Prompt' may be misleading for those who doesn't know the MonadPrompt package. Maybe something like 'ProgramView' ? >> What have we achieved? Both players still can only access functions from >> whatever monad m turns out to be. But now each strategy can pile its own >> custom monad stack on the Player m monad! And of course, the use of >> the m Monad is completely optional. > >Of course, the custom monad stack has to provide a projection back to >the Player m a type > > runMyStackT :: MyStackT (Player m) a -> Player m a According to what Bertram said, "each strategy can pile its own custom monad stack ON the (Player m) monad". Here, you are stacking the (Player m) monad ON the custom monad stack. What is then the use of the 'm', in (Player *m*)? Is it not supposed to be a custom monad? (MonadIO for human, Identity for AI, etc.) But then, I don't see how the game function could work: > game :: Monad m => Player m () -> Player m () -> m () As it is written, it requires both players to run in the SAME monad. And if have a network player ( e.g.* Player (StateT Handle IO)* ) and an AI storing former opponent's moves ( e.g. *(Monad m) => Player (StateT [Move] m)* ), then they can't be in the same monad... * * 2010/4/14 Heinrich Apfelmus <apfelmus(a)quantentunnel.de> > Limestraël wrote: > > > I have some difficulties to see the use of PromptT, because in the > tutorial, > > this type is never mentioned, and its operations (Return and :>>=) are > > instead constructors of ProgramT... > > > > Would you have some concrete examples? Because there I'm a bit lost > (since > > the tutorial doesn't match the operational package as it is, because of > the > > type PromptT)... > > The project page > > http://projects.haskell.org/operational/ > > links to documentation that describes the differences to "The > Operational Monad Tutorial", in particular the new Prompt and PromptT > types. It also links to several examples. Two small examples are also > included in the Haddock documentation. > > > I'd like to make it very accessible, so please don't hesitate to report > any difficulties with finding and understanding documentation and examples! > > > Regards, > Heinrich Apfelmus > > -- > http://apfelmus.nfshost.com > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

3 9

Writing C libraries in Haskell
by Richard G. 01 May '10

01 May '10

Hello I have a few questions about using Haskell (GHC, in particular) to write self-contained libraries with a C interface. ---- If libraries foo and bar are compiled using the same version of GHC, is is possible to link the two libraries into the same executable? Does anything special need to be done? ---- If library foo was compiled using GHC 6.10.4 and library bar was compiled using 6.12.1, is it possible to link the two libraries into the same executable? ---- I'm using the following code to initialize the GHC runtime: hs_init(&argc, &argv); hs_add_root(__stginit_CabalProjectzm0zi0zi2zi0_SimpleModule); where SimpleModule is a module that exports functions via FFI. Is it safe to add more modules after I call a function exported by this module? ---- Also, once hs_exit() has been called, is it possible to reinitialize the GHC runtime? Thanks, Richard

2 1

Writing Mac OS X Plug-Ins in Haskell
by Richard G. 01 May '10

01 May '10

Hello I'm trying to write self-contained Mac OS X plug-ins (http://developer.apple.com/mac/library/documentation/CoreFoundation/Concept…) using GHC. I want the plug-in to be usable on a clean system (i.e., GHC and XCode are not installed). Does anyone have experience with this or does anyone know of some resources on this? I've gotten something working with GHC 6.10.4 and XCode but I found that it requires a lot of work to find and link all of the necessary libraries and the result in not portable. Is there a simple way to take care of all of the dependencies? Thanks, Richard

1 0

How to make way into a hadoop infrastructure
by C K Kashyap 01 May '10

01 May '10

Dear Haskellers, A big part of my new job requires tuning app's on Hadoop. I was wondering if there is a way to push some Haskell code in the mix. I did some googling on "Hadoop/Haskell" and came across Holumbus - but looks like that is parallel to Hadoop. I was thinking in the lines of doing a Haskell implementation that could run in a Hadoop cluster - has anyone tried anything like that? -- Regards, Kashyap

2 2

why does Data.Text.Lazy.IO.readFile return the internal type Data.Text.Lazy.Internal.Text, when Data.Text.IO.readFile returns plain IO Data.Text.Text?
by Thomas Hartman 01 May '10

01 May '10

*Main> :t Data.Text.IO.readFile Data.Text.IO.readFile :: FilePath -> IO T.Text but *Main> :t Data.Text.Lazy.IO.readFile Data.Text.Lazy.IO.readFile :: FilePath -> IO text-0.7.1.0:Data.Text.Lazy.Internal.Text why does the lazy version use the internal type, whereas the strict version of Text IO just using plain Data.Text type? and how can I get from internal type to regular type when using Data.Text? also the internal type doesn't appear to be reflected in the haddock: http://hackage.haskell.org/packages/archive/text/0.7.1.0/doc/html/Data-Text… ghc-pkg list | grep -i text text-0.7.1.0 thanks for any help!

5 9

64-bit code on OSX?
by Gregory Crosswhite 30 Apr '10

30 Apr '10

Hey everyone, Just out of curiosity, does anyone know the story on what is holding up the ability of GHC to generate 64-bit code on OSX? Cheers, Greg

1 0

ANN: Combinatorrent v0.3.0
by Jesper Louis Andersen 30 Apr '10

30 Apr '10

We are pleased to announce Combinatorrent v0.3.0 Combinatorrent is a bittorrent client, written in Haskell and with an emphasis on concurrency. This version has the following changes from v0.2.0: - Numerous space leak fixes. The client doesn't leak memory anymore for typical runs. - A number of performance optimizations. In particular the number of CPU seconds per downloaded megabyte went down considerably compared to earlier versions. - Lowered allocation rate of the client so the garbage collector has less work to do. - Support BEP 0027 implicitly. - Add support for compiling with GHC HEAD (6.13.yyyymmdd series). - Change the parser in the incoming direction to attoparsec and use its incremental features to simplify the receiver loop. Outgoing direction still uses cereal. - Claim BEP 0006 support by implementing the Fast-extension. - Add (untested) BEP 0007 support: Handle IPv6 addresses as well as IPv4 addresses. - Fix a bug where interest updates were not considered correctly. Also lower the amount of interest communication to peers to save bandwidth. Looking ahead, the goal is to support at least the extended messaging protocol. The EMP is a dependency prerequisite for many of the other extensions, hence it is an important building block for further work. As always, the source code and issue tracker is at github: http://github.com/jlouis/combinatorrent -- J.

1 0

Using the Clipboard under Windows
by Günther Schmidt 30 Apr '10

30 Apr '10

Hello, is there some sample code on how to use the Graphics.Win32.GDI.Clip? Günther

3 5

maling-list manager in haskell?
by Günther Schmidt 30 Apr '10

30 Apr '10

Hi, is there a mailing-list manager written in haskell? Best regards Günther

2 1

REMINDER: Haskell Communities and Activities Report
by Janis Voigtländer 30 Apr '10

30 Apr '10

Dear all, It is not yet too late to contribute to the 18th edition of HCAR. If you haven't already, please write an entry for your new project or update your old entry, and send to me this weekend or early next week. More information about format etc. can be found in the original call: http://www.haskell.org/pipermail/haskell/2010-April/022012.html I am looking forward to receiving your contributions, Janis (current editor) -- Jun.-Prof. Dr. Janis Voigtländer http://www.iai.uni-bonn.de/~jv/ mailto:jv@iai.uni-bonn.de

1 0

Rank-2 polymorphism and overloading
by Thomas van Noort 30 Apr '10

30 Apr '10

Hello all, I'm having difficulties understanding rank-2 polymorphism in combination with overloading. Consider the following contrived definition: f :: (forall a . Eq a => a -> a -> Bool) -> Bool f eq = eq True True Then, we pass f both an overloaded function and a regular polymorphic function: x :: forall a . Eq => a -> a -> Bool x = \x y -> x == y y :: forall a . a -> a -> Bool y = \x y -> True g :: (Bool, Bool) g = (f x, f y) Could someone explain to me, or point me to some reading material, why g is correctly typed? I understand that x's type is what f expects, but why does y's polymorphic type fulfill the overloaded type of f's argument? I can imagine that it is justified since f's argument type is more restrictive than y's type. However, it requires y to throw away the provided dictionary under the hood, which seems counter intuitive to me. Regards, Thomas

4 5

MySQL and Haskell on Windows
by gladstein＠gladstein.com 29 Apr '10

29 Apr '10

cabal install hdbc-mysql almost works on windows, but errors because the mysql_config command isn't part of the windows MySQL install. Has anyone been able to get a Haskell interface to MySql going on Windows, either directly or via odbc? cabal install haskelldb-hsql-odbc fails because it can't find an 'odbc' library. There are any number of odbc dll's installed by the MySQL odbc connector, but they all have slightly different names. As always, a precompiled binary would be preferable but I'm happy to compile stuff under Cygwin or MINGW if need be. Thanks in advance for your help.

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Cabal package with BSD3 library and LGPL executable?
by Stephen Tetley 29 Apr '10

29 Apr '10

Hello all How do I mark a Cabal package as containing a BSD3 library and an LGPL executable? I'm using CppHs (LGPL) from the exe but have no dependencies on it in the library; as the library might be independently useful I want it to be BSD3. As a caveat - I don't want two packages... Thanks Stephen

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Problem about pattern matching.
by Magicloud Magiclouds 29 Apr '10

29 Apr '10

Hi, I have code as below. How come "case" version works wrong and gives me "overlap" compiling warning? Thanks. if dayOfMonth == firstDayOfMonth then v day (x, y) else if dayOfMonth == lastDayOfMonth then not_ $ v day (x, y) else Mider day (x, y) case dayOfMonth of firstDayOfMonth -> v day (x, y) lastDay -> not_ $ v day (x, y) _ -> Mider day (x, y) -- 竹密岂妨流水过山高哪阻野云飞

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GSoC: Improving Cabal's Test Support
by Thomas Tuegel 29 Apr '10

29 Apr '10

Hello community! I've been working on a proposal for Google Summer of Code 2010 to work on improving Cabal's test support, as described on the Haskell SoC Trac [1]. Today I'm looking for feedback to see if what I intend is what people want/need. As you read this, I kindly ask that you consider: 1) Would you use the facility I describe, were it available? and 2) What additional features would you like to see? There have been two separate suggestions (of which I am aware) of ways to integrate tests into Cabal. One is to build the tests into their own executable which uses an error code on exit to indicate test failure. The second is to have package authors write modules which Cabal will load (dynamically?) and run the tests from. The former method has the advantage of being simpler to implement, but is probably too granular. Although the second suggestion avoids some security concerns, it seems to me that a malicious party could simply put nefarious code into their Setup.hs file anyway, or even in the library being tested. I propose to build a test suite as its own executable, but to avoid the problem of granularity by producing an output file detailing the success or failure of individual tests and any relevant error messages. The format of the file would be standardized through library routines I propose to write; these routines would run tests with HUnit or QuickCheck and process them into a common format. Cabal, or any other utility, could read this file to determine the state of the test suite. Perhaps Cabal could even warn the user about installing packages with failing tests. Under this proposal, a test suite would look something like this (suppose I am writing a test suite for a module Foo, which has an existing test suite in QuickCheck): > module Main where > > import Foo > import Test.QuickCheck > import Distribution.Test -- This module is part of the project I propose > > main = runTests > [ ("testBar", wrap $ testBar), ("testBaz", wrap $ testBaz) ] -- (name, test) 'runTests' and 'wrap' would be provided by 'Distribution.Test'. 'wrap' would standardize the output of test routines. For QuickCheck tests, it would probably look like: > wrap :: Testable a => a -> IO (Bool, String) where the Bool indicates success and the String can be an error message the test produced. 'runTests' would take the list of tests, format their results, and write the output to a file: > runTests :: [(String, IO (Bool, String))] -> IO () I would probably gather the test results into a value of type '[(String, Bool, String)]' -- the name, status, and messages associated with each test -- and use 'show' to produce a nice, human-readable, machine-parsable file. The test suite would be included in the package description file with a stanza such as: > Test > main-is: Test.hs > build-depends: foo, QuickCheck, Cabal This would take all the same options as an 'Executable' stanza, but would tell Cabal to run this executable when './Setup test' is invoked. This of course requires Cabal to support building executables that depend on the library in the same package. Since version 1.8, Cabal supposedly supports this, but my experiments indicate the support is a little broken. (GHC is invoked with the '-package-id' option, but Cabal only gives it the package name. Fixing this would naturally be on the agenda for this project.) At this point, the package author need only run: $ ./Setup configure $ ./Setup build $ ./Setup test to produce a file detailing the results of the test suite. I apologize for taking up your time with a such a lengthy message, and eagerly await your feedback! Thanks! -- Thomas Tuegel [1] http://hackage.haskell.org/trac/summer-of-code/ticket/1581

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Re: [Haskell-cafe] ANN: CPSA - Cryptographic Protocol Shapes Analyzer
by John D. Ramsdell 29 Apr '10

29 Apr '10

>> We are working towards a version of CPSA with the property that >> whenever it successfully terminates, every possible execution is >> described by its output. However, the current implementation >> occasionally fails to find some executions. > > That is concerning - is it due to ... We have formally specified the algorithm, but we haven't been able to prove the algorithm finds all solutions. In fact, we now have an example in the test suite that shows it misses an answer. The example is in the source distribution in tst/missing-contraction.scm. There should be two answers, but CPSA only finds one. We have a fix you can try out in 2.0.4. In src/CPSA/Lib/Strand.hs, you can change the flag useDisplacement from False to True, and CPSA will find both answers. We don't know if this fix is all one needs to ensure CPSA finds every answer. By the way, the algorithm is in doc/cpsaspec.pdf, which can be build from a source distribution of CPSA. > What is the current status of development both wrt openness and future direction? Our highest priority is to resolve the correctness issue you just raised. As for openness, the sources are available to you. We haven't thought about other forms of openness. > I'm wondering if you plan to add MQV or other non-trivial primitives. I don't know what MQV is, so I can't say. Thanks for your interest, Thomas. John

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Lazy Parsing (ANN: vcd-0.1.4)
by Tom Hawkins 29 Apr '10

29 Apr '10

I had been using Parsec to parse VCD files, but needed to lazily parse streaming data. After stumbling on this thread below, I switch to polyparse. What a great library! I was able to migrate from a strict to a semi-lazy parser and many of my parse reductions didn't even need to change. Thanks Malcolm! In addition to lazy VCD parsing, this version of vcd [1] also includes step', which forces a step regardless if variables have changed or not -- helpful for realtime simulation. (BTW, parsec is a great library too.) -Tom [1] http://hackage.haskell.org/package/vcd-0.1.4 On Sun, May 31, 2009 at 6:41 AM, Malcolm Wallace <malcolm.wallace(a)cs.york.ac.uk> wrote: > > I don't know whether you will be willing to change over to polyparse > library, but here are some hints about how you might use it. > > Given that you want the input to be a simple character stream, rather than > use a more elaborate lexer, the first thing to do is to specialise the > parser type for your purposes: > >> type TextParser a = Parser Char a > > Now, to recognise a "mere digit", > >> digit :: TextParser Char >> digit = satisfy Char.isDigit > > and for a sequence of digits forming an unsigned integer: > >> integer :: TextParser Integer >> integer = do ds <- many1 digit >> return (foldl1 (\n d-> n*10+d) >> (map (fromIntegral.digitToInt) ds)) >> `adjustErr` (++("expected one or more digits")) > >> I mean I'd like to be able to turn "12.05.2009" into something like (12, >> 5, 2009) and got no clue what the code would have to look like. I do know >> almost every variation what the code must not look like :). > >> date = do a <- integer >> satisfy (=='.') >> b <- integer >> satisfy (=='.') >> c <- integer >> return (a,b,c) > > Of course, that is just the standard (strict) monadic interface used by many > combinator libraries. Your original desire was for lazy parsing, and to > achieve that, you must move over to the applicative interface. The key > difference is that you cannot name intermediate values, but must construct > larger values directly from smaller ones by something like function > application. > >> lazydate = return (,,) `apply` integer `discard` dot >> `apply` integer `discard` dot >> `apply` integer >> where dot = satisfy (=='.') > > The (,,) is the constructor function for triples. The `discard` combinator > ensures that its second argument parses OK, but throws away its result, > keeping only the result of its first argument. > > Apart from lazy space behaviour, the main observable difference between > "date" and "lazydate" is when errors are reported on incorrect input. For > instance: > > > fst $ runParser date "12.05..2009" > *** Exception: In a sequence: > Parse.satisfy: failed > expected one or more digits > > > fst $ runParser lazydate "12.05..2009" > (12,5,*** Exception: In a sequence: > Parse.satisfy: failed > expected one or more digits > > Notice how the lazy parser managed to build the first two elements of the > triple, whilst the strict parser gave no value at all. > > I know that the error messages shown here are not entirely satisfactory, but > they can be improved significantly just by making greater use of the > `adjustErr` combinator in lots more places (it is rather like Parsec's <?>). > Errors containing positional information about the input can be constructed > by introducing a separate lexical tokenizer, which is also not difficult. > > Regards, > Malcolm > > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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