- Haskell-Cafe - Haskell.org

Partially applied functions
by Ozgur Akgun 28 Nov '09

28 Nov '09

Hi cafe, Is such a thing possible, add :: Int -> Int -> Int add x y = x + y -- a list of partially applied functions adds = [add 3, add 5, add 7, add 3, add 5, add 8] -- an example usage of the list k = map (\ f -> f 10 ) adds add3s = filter (?) adds -- add3s = [add 3, add 3] addEvens = filter (?) adds --addEvens = [add 8] I want to have functions in place of the ? signs. I guess one would need a way of extracting the applied value from a partially applied function (or totally, doesn't matter) I came across such a structure while designing an algotihm and used data structures to represent functions and solved the problem. But this doesn't seem very *cute* to me and requires some bolier-plate (if you have a lot of this structure everywhere) , that's why I am asking for your precious suggestions. Best, -- Ozgur Akgun

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cabal-install binary for FreeBSD
by Michael Snoyman 28 Nov '09

28 Nov '09

Hi all, I'm trying out NearlyFreeSpeech.net for hosting my Haskell apps. They use FreeBSD 7.2, but I can't get cabal-install to compile since it runs out of memory during the link phase. So far I haven't had trouble manually installing packages, but it would be nice to just do cabal install... Anyway, I don't have FreeBSD installed locally, and I was wondering if anyone out there might have a cabal binary for FreeBSD that they could send over. Thanks, Michael

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ANNOUNCE: deepseq-1.0.0.0
by Simon Marlow 28 Nov '09

28 Nov '09

I've just uploaded deepseq-1.0.0.0 to Hackage http://hackage.haskell.org/package/deepseq This provides a DeepSeq class with a deepseq method, equivalent to the existing NFData/rnf in the parallel package. I'll be using this in a newly revamped parallel package, which I hope to upload shortly. Cheers, Simon

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Custom cabal languages (hooks?)
by Svein Ove Aas 28 Nov '09

28 Nov '09

I'm currently working on a binding to Brian Gladman's C/assembler AES implementation. This code is sufficiently small that it makes little sense to create a separate C library for it; furthermore, it isn't typically packaged by the various linux distributions, never mind other OSs. As a result, I'd like to make it part of the cabalized AES package. This works well enough with the pure-C variant of the implementation, but it also has assembly-based implementations of the core encryption routines for x86 and x86_64, specifically using yasm, which I would like to use when possible. So, two problems.. - First, I need to make cabal detect yasm's presence, and call out to it when appropriate. The former I can do with a configure script; the latter, I'm not quite sure how to do. Currently, cabal can only do C; basically, I'm looking for a way to let it use any language that can be compiled to .o files. - Second, having manually compiled the C/asm bits to .a and .so form, I did eventually get cabal to link (seemingly) correctly against it, but it then did not proceed to copy libaes.so into ~/.cabal/lib/AES/.... I'm not sure how to make it do that, either. I suppose I'll have to use hooks, but I'd appreciate a little advice on how, exactly Well, I've put a snapshot of my current code at http://brage.info/~svein/aes/, so you can have a look. I'd really appreciate the help. -- Svein Ove Aas

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hoogle down
by Keith Sheppard 28 Nov '09

28 Nov '09

hoogle is down for me: "Internal Server Error" Thanks Keith -- keithsheppard.name

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HWN This week
by Joe Fredette 28 Nov '09

28 Nov '09

Hey folks, I'm at home this weekend, and the internet is somewhat dodgey, so I'm going to delay the special Thanksgiving episode of the HWN till sunday afternoon... I suppose the Turkey-coma isn't helping either, but I'll never admit it... /Joe

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FastCGI under Windows
by Kevin Jardine 28 Nov '09

28 Nov '09

I'm attempting to get FastCGI working with Haskell under Windows XP. However, all the sample code I've tried always fails with: user error (FCGX_Accept_r failed with error code: -9999) unknown listenType (0) Has anyone seen this before? Any ideas on what I could try to get this to work? Kevin

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Re: [Haskell-cafe] ANN: mecha-0.0.4
by Tom Hawkins 28 Nov '09

28 Nov '09

On Fri, Nov 27, 2009 at 12:09 PM, Serge Le Huitouze <serge.lehuitouze(a)gmail.com> wrote: > Hi Tom! > >> Mecha is a little constructive solid modeling language intended for 3D >> CAD. This release adds animation capabilities, which use POVRay and >> FFmpeg behind the scenes. At work we've used Mecha to illustrated the >> kinematics of a new hydraulic pump design -- I wish I could post the >> animation, it's pretty cool to watch. >> >> http://hackage.haskell.org/package/mecha/ > > It would be great if you could forge a simple example illustrating the > capabilities, > even it's not as cool as your "real" hydraulic pump. > Since you're the creator of the software, I imagine it's very easy for you to > find a simple, yet significant, example (you may even have some already > available, e.g. that you developed for your unit tests...). Sure. I started a simple model of a bent-axis pump. It will probably take me a few days to complete. In the mean time, you can pull down the latest snapshot from patch-tag.com. Currently the model has 3 parts finished: a timing plate, a barrel group, and a piston. No animation, but the CAD views provide decent visualization. > > > Best regards. > > --Serge Le Huitouze >

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Re: [Haskell-cafe] Atom - help.
by Tom Hawkins 28 Nov '09

28 Nov '09

Calling foreign functions that return values is problematic for the compiler -- I haven't invested enough time to come up with a good solution. The work around is to assign the result to an external variable. The drawback is the result will not be available until the rule executing the action has completed. results <- bool' "result" -- Global, external variable to capture result. action (\ [a, b, c] -> printf "result = function(%s, %s %s)" a b c) [a, b, c] -Tom On Sat, Jun 13, 2009 at 5:03 AM, Radamés Ajna<radamajna(a)gmail.com> wrote: > hi there, > > I've been working with haskell and atom dsl, however I'm new to haskell.. > John Van Enk inspired me with programming arduino->atmegas , with haskell, > So here is my problem. > With an action , action :: ([String] -> String) -> [UE] -> Atom () , > it's possible make calls to some precoded C functions like, > > setLED v = action (\[x] -> "setLED(" ++ x ++ ")") [v'] > where v' = ue . value $ v > > where setLed is a precode function. > > I want call a precoded C function that returns some value, but action > always give me Atom () , > that's I would like to do but I don't know how .. > > Atom (V Int8) < ---- "int read()" > > > thanks... > related links > http://hackage.haskell.org/package/atom-0.0.5 > http://blog.sw17ch.com/wordpress/?p=111 > http://leepike.wordpress.com/2009/05/05/an-atomic-fibonacci-server-explorin… > > > > Radamés > _______________________________________________ > Haskell-Cafe mailing list > Haskell-Cafe(a)haskell.org > http://www.haskell.org/mailman/listinfo/haskell-cafe >

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ANN: package-vt-0.1.3.3, Haskell Package Versioning Tool
by Krzysztof Skrzętnicki 28 Nov '09

28 Nov '09

Hi! I'm pleased to announce the first release of my program package-vt. It's role is to detect changes between two versions of package that should cause version bump. Recommended versioning policy for Haskell packages is on the wiki [1]. The ultimate goal is to get as good approximation of the algorithm specified there as possible. Currently the tool is far from being complete: it only detects changes to exports in .cabal and module files, but doesn't take any types into consideration, not to mention other possible heuristics. This tool is not meant as a replacement for developer's own brain. It can only detect a subset of changes, and there will always be some important changes it won't catch, like adding such line: head (_:y:_) = y However, it can be used for some quality checks. Thing that needs improving is user interface. No options are currently accepted. This, and a lot more, will change in future versions. You can find a Git repo here [2]. The repo contains 'tests' directory with two useful scripts. You can use them to run package-vt on anything from Hackage. Here are a few random usage examples: 1) Detect small change within module package-vt packages/HCL/1.1/HCL-1.1/HCL.cabal packages/HCL/1.2/HCL-1.2/HCL.cabal Single changes: ChangeABC : Entity added to module ModuleName "HCL" --- EVar (UnQual (Ident "prompt1")) --- Biggest change comes from: ChangeABC : Entity added to module ModuleName "HCL" --- EVar (UnQual (Ident "prompt1")) 2) Detect new module added to .cabal package-vt 0.2.0/AERN-Net-0.2.0/AERN-Net.cabal 0.2.1/AERN-Net-0.2.1/AERN-Net.cabal Single changes: ChangeABC : Entity added to module ModuleName "Control.ERNet.Foundations.Process" --- EThingAll (UnQual (Ident "ERProcessAction")) ---ChangeABC : Module(s) added.(Consider AB change if new modules are likely to cause name collisions) --- "Control/ERNet/Blocks/Real/LFT" --- Biggest change comes from: ChangeABC : Module(s) added.(Consider AB change if new modules are likely to cause name collisions) --- "Control/ERNet/Blocks/Real/LFT" --- 3) Using testing script: package-vt correctly detects that AERN-RnToRM-0.4.9 should rather be 0.5.0 because the module Data.Number.ER.RnToRm.UnitDom.ChebyshevBase.Polynom.Field has been removed. ./test-on-package.lhs AERN-RnToRm --cut-- >>> Testing package-vt on AERN-RnToRm-0.4.2 and AERN-RnToRm-0.4.9 Parse error: VarSym "#" : SrcLoc {srcFilename = "0.4.2/AERN-RnToRm-0.4.2/src/Data/Number/ER/RnToRm/Approx/DomTransl.hs", srcLine = 174, srcColumn = 1} Single changes: ChangeABC : Entity added to module ModuleName "Data.Number.ER.RnToRm.Approx" --- EVar (UnQual (Ident "keyPointsConsistencyCheck")) EVar (UnQual (Ident "keyPointsPointwiseConsistencyCheck")) ---ChangeABC : Entity added to module ModuleName "Data.Number.ER.RnToRm.UnitDom.Approx" --- EVar (UnQual (Ident "keyPointsConsistencyCheck")) EVar (UnQual (Ident "keyPointsPointwiseConsistencyCheck")) ---ChangeAB : Module(s) removed/renamed. --- "Data/Number/ER/RnToRm/UnitDom/ChebyshevBase/Polynom/Field" --- Biggest change comes from: ChangeAB : Module(s) removed/renamed. --- "Data/Number/ER/RnToRm/UnitDom/ChebyshevBase/Polynom/Field" --- ExitSuccess --cut-- In case of any trouble please email me or report an issue here [3]. In the near future I'll post more specific plans about development on my blog [4]. I hope you will find it useful. Best regards, Krzysztof Skrzętnicki [1] http://www.haskell.org/haskellwiki/Package_versioning_policy [2] http://github.com/Tener/haskell-package-vt [3] http://github.com/Tener/haskell-package-vt/issues [4] http://mostlycode.wordpress.com

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GLFW Textures (bloxorz)
by jean legrand 27 Nov '09

27 Nov '09

Hi Haskellers, I have two issues with the bloxorz game (current version bloxorz-0.1 on hackage). Perhaps they're mutually related. You tell me. First, it seems that there is no refresh on the successive block positions. Look at http://img524.imageshack.us/img524/5945/bloxissue1.png to see what I mean. Second, any resize gives me a black window. Everything else is fine (levels, game rules, keys ...) To produce the exe, I did : ghc --make -O2 -o bloxorz Main.hs and, as I think it deals with the textures, here is what I get with ghci : Loading package syb ... linking ... done. Loading package base-3.0.3.1 ... linking ... done. Loading package ObjectName-1.0.0.0 ... linking ... done. Loading package OpenGLRaw-1.1.0.1 ... linking ... done. Loading package GLURaw-1.1.0.0 ... linking ... done. Loading package StateVar-1.0.0.0 ... linking ... done. Loading package Tensor-1.0.0.1 ... linking ... done. Loading package OpenGL-2.4.0.1 ... linking ... done. Loading package GLFW-0.4.1 ... linking ... done. and I use GHC6.10.4 with Kubuntu 9.10. Any ideas ?

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Re: [Haskell] ANN: NoSlow - Microbenchmarks for array libraries
by Henning Thielemann 27 Nov '09

27 Nov '09

On Fri, 27 Nov 2009, Roman Leshchinskiy wrote: > It compiles and runs (using Brian's criterion) a fairly random collection of very small loop kernels for each of those and produces a lot of data which it then uses to generate ugly HTML tables. In the future, it will have more benchmarks, more complex benchmarks and much prettier tables. > > You can get more information (including the ugly tables) from my blog > > http://unlines.wordpress.com/2009/11/27/noslow > > and NoSlow itself from Hackage > > http://hackage.haskell.org/package/NoSlow Is there also a darcs repository? I want to note, that storablevector requires Quickcheck only for tests. In the darcs repository, this is better handled by the Cabal file: http://code.haskell.org/storablevector/ There you get the dependency on QuickCheck (1) only when building with buildTests flag set. Now I have to get NoSlow running, but surprisingly it needs cairo and gtk, which I assume are not so easy to install.

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Other instances of Integral
by Tsunkiet Man 27 Nov '09

27 Nov '09

Hello, I would like to ask wheter there are other instances of the class Integral? And I would like to ask what the difference is between the following functions: SomeFunctionA :: (Integral a) => a -> a, SomeFunctionB (Integer a) => a -> a, SomeFunctionC (Int a) => a -> a. What I do know is, that the Int can have underflow and overflows, however I don't actually see the difference (and I can't really find a difference on Google as it gives me results that aren't really relevant to my question) between prefering to use an Integral a when I've already got an Integer. (Assuming I didn't missed the definiton of a Integral, which has by definition (I looked it up on Google: http://www.zvon.org/other/haskell/Outputprelude/Integral_c.html) has two instances) What I also know is that operatons on a Int is faster than operations on a Integral or Integer. Can someone explain to me what kind of advantages and disadvantages I would get when substituting SomeFunctionB for someFunctionA? Thank you for your help!

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Reducing Latency - Reducing the Size of Larger Data Structures
by Casey Hawthorne 27 Nov '09

27 Nov '09

An idea to reduce memeory latency, is to have a complex dual/quad/etc. core CPU surrounded by four or more simpler CPUs. The simpler CPUs have a simpler instruction set and do less context switching. So any operations (e.g. folding, filtering) that reduce the size of a larger data structure and that can be done on the simpler CPU instruction sets are shunted off to the simpler CPUs. So, the complex CPUs receive less data and therefore can have better cacheing performance, less latency and better throughput. -- Regards, Casey

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Re: [Haskell] ANN: NoSlow - Microbenchmarks for array libraries
by Henning Thielemann 27 Nov '09

27 Nov '09

Roman Leshchinskiy schrieb: > I'm pleased to announce NoSlow, a nascent benchmark suite for various array (and list) libraries with particular emphasis on finding out how well they fuse things. At the moment, it knows about > > * standard lists > * primitive DPH arrays (dph-prim-seq) > * uvector > * vector > * storablevector > > It compiles and runs (using Brian's criterion) a fairly random collection of very small loop kernels for each of those and produces a lot of data which it then uses to generate ugly HTML tables. In the future, it will have more benchmarks, more complex benchmarks and much prettier tables. > > You can get more information (including the ugly tables) from my blog > > http://unlines.wordpress.com/2009/11/27/noslow > > and NoSlow itself from Hackage > > http://hackage.haskell.org/package/NoSlow > > Any help would be highly appreciated as I don't have a lot of time to work on it. Since storablevector is in no way optimized for fusion, I'd like to see how well it compares with Fusion-Streams that are fused into strict and lazy storablevectors by http://hackage.haskell.org/package/storablevector-streamfusion . Thanks for the benchmarking effort!

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Re: [Haskell] ANN: NoSlow - Microbenchmarks for array libraries
by Henning Thielemann 27 Nov '09

27 Nov '09

Roman Leshchinskiy schrieb: > I'm pleased to announce NoSlow, a nascent benchmark suite for various array (and list) libraries with particular emphasis on finding out how well they fuse things. At the moment, it knows about > > * standard lists > * primitive DPH arrays (dph-prim-seq) > * uvector > * vector > * storablevector > > It compiles and runs (using Brian's criterion) a fairly random collection of very small loop kernels for each of those and produces a lot of data which it then uses to generate ugly HTML tables. In the future, it will have more benchmarks, more complex benchmarks and much prettier tables. > > You can get more information (including the ugly tables) from my blog > > http://unlines.wordpress.com/2009/11/27/noslow > > and NoSlow itself from Hackage > > http://hackage.haskell.org/package/NoSlow > > Any help would be highly appreciated as I don't have a lot of time to work on it. Since storablevector is in no way optimized for fusion, I'd like to see how well it compares with Fusion-Streams that are fused into strict and lazy storablevectors by http://hackage.haskell.org/package/storablevector-streamfusion . Thanks for the benchmarking effort!

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Show function a -> String
by Tsunkiet Man 27 Nov '09

27 Nov '09

Hello, let's say I'm defining function that does the following: ShowFloat -> Floating -> String, at what kind of userinput (assuming you insert some floating number) will I get an error? (Please do not post overflow, because I already know that =)). Thanks for your help again guys!

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ANN: wumpus-core-0.13.0
by Stephen Tetley 27 Nov '09

27 Nov '09

Hello All Wumpus-core is a library for drawing 2D vector pictures, supporting output to PostScript and SVG. It has no FFI dependencies, so should be portable across operating systems (assuming GHC with type families). Wumpus-core is functional, though quite low-level - its similar to PostScript but with a more 'coordinate free' style. I'm working on a complementary package for higher-level stuff, but it will be some time before it is release ready. Many thanks to Conal Elliott and Iavor S. Diatchki for their invaluable libraries (VectorSpace and MonadLib/xml respectively). Best wishes Stephen http://hackage.haskell.org/package/wumpus-core

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I really donot know how to use `newtype` ?
by zaxis 27 Nov '09

27 Nov '09

import Control.Monad.State import Control.Monad.Reader data XConf = XConf {} data XState = XState {} newtype X a = X (ReaderT XConf (StateT XState IO) a) > :t StateT StateT :: (s -> m (a, s)) -> StateT s m a > :t ReaderT ReaderT :: (r -> m a) -> ReaderT r m a then how to use `X` ? Would you mind explaining the newtype X in detail ? Sinerely! ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/I-really-donot-know-how-to-use-%60newtype%60---tp2654… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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Re: Iteratee question
by Valery V. Vorotyntsev 27 Nov '09

27 Nov '09

On Fri, Nov 27, 2009 at 4:04 AM, John Lato <jwlato(a)gmail.com> wrote: > My apologies for not replying; I have been traveling and am only now > working through my email. > > Oleg's response is much better than anything I would have written. > I'd like to add one point. > > stream2list is very inefficient as he mentioned, however only for > large values of 'n'. For small n it should be fine. Assuming you're > using Word8 elements, "small" means "< 4096". This is because the > default chunk size reading from a file is 2048 elements, so for any n > < 4096 you have at most two concatenations in producing the > stream2list. > > Sincerely, > John Lato > > PS for one example of a binary data parser, please see > http://inmachina.net/~jwlato/haskell/iter-audio/ > > This is similar to the audio codec included with iteratee, but much > more efficient. In particular, the functions "convFunc" and > "unroller" in Sound.Iteratee.Codecs.Common are pretty highly > optimized. Wonderful! Sample code is very helpful to get familiar with iteratees. Thank you, John. Thanks to both of you. -- vvv

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Types
by Tsunkiet Man 27 Nov '09

27 Nov '09

Hello, I´ve a small question about Haskell. It´s really vague explained in "Haskell in 10 minutes" and sometimes it's really detailed explained which is very hard for people who just got into Haskell to read. Can someone explain me something about the type Integral? What exactly is it? I know that 2 is something of the type Integral, however what does this differ from Int? The same question goes for Fractional and Floating, what exactly is their commonality and what exactly is their difference? Thank you for explaining these basic things to me.

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Possible FGL bug
by Ivan Lazar Miljenovic 27 Nov '09

27 Nov '09

When developing my QuickCheck-2 test-suite for graphviz, I wrote the following Arbitrary instance for FGL graphs (which needs FlexibleInstances): ,---- | instance (Graph g, Arbitrary n, Arbitrary e, Show n, Show e) => Arbitrary (g n e) where | arbitrary = do ns <- liftM nub arbitrary | let nGen = elements ns | lns <- mapM makeLNode ns | trace ("Nodes: " ++ show lns) (return ()) | les <- listOf $ makeLEdge nGen | trace ("Edges: " ++ show les) (return ()) | return $ mkGraph lns les | where | makeLNode n = liftM ((,) n) arbitrary | makeLEdge nGen = liftM3 (,,) nGen nGen arbitrary | | shrink gr = map (flip delNode gr) (nodes gr) `---- However, when I try to run this, I occasionally get irrefutable pattern match failures as follows: ,---- | *Data.GraphViz.Testing.Instances.FGL Data.Graph.Inductive.Tree> sample (arbitrary :: Gen (Gr Int Char)) | | | 0:0->[] | | 0:-2->[] | 1:0->[('\a',0)] | 2:0->[] | | -4:-3->[('U',-3),('#',1)] | -3:3->[] | 1:-1->[('}',-3)] | | -8:8->[] | -3:2->[] | -1:-5->[('\US',-3),('&',0)] | 0:5->[('F',-1),('p',4)] | 4:-1->[] | | -2:8->[('\177',-2),('(',-2),('d',-2),('4',-2),('D',-2),('\US',-2),('d',-2),('u',-2)] | | -16:11->[] | -2:-2->[] | 0:11->[('@',1)] | 1:13->[('u',11)] | 9:-11->[('\231',11)] | 11:12->[('\226',1)] | 16:15->[] | | -10:2->[] | -4:8->[] | 1:30->[] | 26:26->[('<',1),('K',-4)] | 31:-21->[] | | -35:51->[('@',-29)] | -29:21->[('\132',-11)] | -11:-31->[('j',61)] | -4:40->[('a',-29)] | 0:6->[('z',-35),('9',28),('\170',-11),('\SUB',28)] | 23:8->[('P',-29),('(',61),('\\',28)] | 28:60->[] | 61:44->[('q',61)] | *** Exception: Data/Graph/Inductive/Graph.hs:250:26-59: Irrefutable pattern failed for pattern (Data.Maybe.Just (pr, _, la, su), g') `---- The actual error comes from the definition of insEdge: ,---- | -- | Insert a 'LEdge' into the 'Graph'. | insEdge :: DynGraph gr => LEdge b -> gr a b -> gr a b | insEdge (v,w,l) g = (pr,v,la,(l,w):su) & g' | where (Just (pr,_,la,su),g') = match v g `---- with the Graph instance for Tree-based graphs using this for its mkGraph method: ,---- | mkGraph vs es = (insEdges' . insNodes vs) empty | where | insEdges' g = foldl' (flip insEdge) g es `---- So, is this really a bug in FGL, or am I using mkGraph wrong? On another note, why doesn't the PatriciaTree graph type have a Show instance? :( -- Ivan Lazar Miljenovic Ivan.Miljenovic(a)gmail.com IvanMiljenovic.wordpress.com

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separate cabal installations on separate machines
by Brian Denheyer 27 Nov '09

27 Nov '09

Hello, I have server where my home directory resides. I use cabal from (at least) two machines with different processors (i386, powerpc) and the common home directory. I noticed that there is a --global option which does the right thing and places the installs in /usr/local, but it looks like it still stores some info, particularly about configuration state, in /home/${USER}/.cabal. How do I invoke cabal to make sure that the entire installation is machine specific ? Thanks, Brian

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some help on do and preservingMatrix
by Zsolt Ero 26 Nov '09

26 Nov '09

Sorry to ask such a basic question here, but I am trying to write my first Haskell OpenGL animation and just encontered with these questions: Could someone point me to some help on how does "do" work and how does preservingMatrix? I am trying to write a program starting from the OpenGL tutorial on the wiki, but I never used do's before. My very basic question is that how do I generally repeat a command many times? I understand "do" can do it, but it's not clear to me how to use it and how it works. So if I would like to write the following in one line, how could I write it?: spiral 0.7 spiral 0.8 spiral 0.9 spiral 1.0 I don't understand in which cases I can use "map something [0.7,0.8..1]" and in which cases I need do and how could I map using do. >From the tutorial, I could write this line, which works, but I don't really know what does mapM_ and preservingMatrix do. mapM_ (\x -> preservingMatrix $ do scale x x (1::GLfloat) rotate (x*(200)) $ Vector3 0 0 (1::GLfloat) spiral ((sin(a/50))^2/2+0.5) ) $ ([0.5,0.6..1::GLfloat]) Zsolt

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hackage unix broken
by Brian Denheyer 26 Nov '09

26 Nov '09

System/Posix/Process/Internals.hs:10:17: Module `GHC.Conc' does not export `Signal' The breakage is reported on hackage. The GHC.Conc page is still showing Signal, so it seems like this shouldn't be a problem. Is this a ghc library bug, i.e. should I start a ticket, or has it simply moved somewhere else ? Thanks, Brian

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How does cabal determine version ranges in the dependencies?
by David Fries 26 Nov '09

26 Nov '09

Hi everyone I recently started porting cabal-install to Freebsd. When I looked at its dependencies on hackage, I noticed HTTP (>=4000.0.2 && <4001). However the latest HTTP version on hackage is 4000.0.8. That struck me as kinda odd. How can cabal tell that it won't be compatible with HTTP version 4001? regards david -- Preisknaller: GMX DSL Flatrate für nur 16,99 Euro/mtl.! http://portal.gmx.net/de/go/dsl02

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ANN: Elerea 1.1
by Patai Gergely 26 Nov '09

26 Nov '09

Hello all, Elerea is a simple pull-based FRP library, which allows you to do stream-oriented programming using a primarily applicative style. Unlike traditional stream-based languages, streams (which I call 'signals' in the library) are first-class entities. I uploaded a new version with an experimental branch that reimplements the original idea in a completely different way: - without unsafePerformIO (although with some restructuring it could be used to make the interface 'more applicative') or existential types - signals are Monad instances, so you can use do notation to sample them - for the same reason the 'sampler' combinator is gone; you can use join instead, which is also well-behaved in comparison (i.e. the output of signals doesn't depend any more on how you observe them) - since the library didn't build on the time step being a Double in any way, I relaxed its type (see the Param branch) - the semantics is cleaned up somewhat (I plan to elaborate on this point later in a blog post, but until then you can check the Simple branch for a general idea) Gergely -- http://www.fastmail.fm - Accessible with your email software or over the web

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Re: Iteratee question
by oleg＠okmij.org 26 Nov '09

26 Nov '09

Valery V. Vorotyntsev wrote: > The following pattern appears quite often in my code: > > results <- map someConversion `liftM` replicateM nbytes Iter.head > > The meaning is: take `nbytes' from stream, apply `someConversion' to > every byte and return the list of `results'. > But there's more than one way to do it: > > > i1, i2, i3 :: Monad m => Int -> IterateeG [] Word8 m [String] > > i1 n = map conv `liftM` replicateM n Iter.head > > i2 n = map conv `liftM` joinI (Iter.take n stream2list) > > i3 n = joinI $ Iter.take n $ joinI $ mapStream conv stream2list > Of those i1, i2, i3 which one is "better" and why? Or is there another - > preferable - way of applying iteratees to this task? > My nai:ve guess is that i1 will have worse performance with big n's. It > looks like `i1' is reading bytes one by one, while `i2' takes whole > chunks of data... I'm not sure though. You are correct: i2 and i3 can process a chunk of elements at a time, if an enumerator supplies it. That means an iteratee like i2 or i3 can do more work per invocation -- which is always good. Since you have to get the results as a list, you pretty much have to use stream2list. It should be noted that stream2list isn't very efficient: it returns the accumulated list only when it is done -- which happens when the stream is terminated, normally or abnormally. So, stream2list has a terrible latency, and is useful only at the last stage of processing. I found it is most useful for testing (to see the resulting stream) and for writing Unit tests (to compare the produced results with the expected). For incremental processing, it is better to stay within Iteratees. Although I think i2 and i3 should be close in performance (only benchmarking can tell for sure, of course), i3 is more extensible because stream2list is at the end of the chain. If later on further processing is required (or, the latency imposed by stream2list becomes noticeable), the chain can be easily extended. The advantage of the arrangement of i3 is that if some Iteratee further down the chain decided that it has had enough (elements), Iter.take can quickly skip the remaining elements without the need to convert them.

2 1

haskell-mode.el mailing list (+ dpatch)
by valery.vv＠gmail.com 26 Nov '09

26 Nov '09

Is there anybody except me feeling the need for mailing list and issue tracker for emacs' haskell-mode? Mailing list is a forum to discuss ideas _and_ the area of patch authors' self-advertisement. And issue tracker is a TODO list; it may be useful or annoying, and I think we can live without one for a while. But I vote for haskell-mode.el mailing list. Examples: http://www.haskell.org/mailman/listinfo/xmonad http://code.google.com/p/xmonad/issues/list -- Description of the attached dpatch: * make `inferior-haskell-find-project-root' respect export lists A "hierarchical module" (one or more dots in module name) with an export list cannot be loaded (`C-c C-l') unless there is .cabal file available. That is because regexp current in `inferior-haskell-find-project-root' does not match module headers with export lists. Like this one: module Codec.Binary.MSCP ( -- * Data structures FileHeader(..), CDR(..), -- * Parsing readFile ) where This patch makes the regexp less strict. Have fun! -- vvv <#part type="application/octet-stream" filename="/tmp/XXX/respect-export-lists.dpatch" disposition=attachment description=respect-export-lists.dpatch> <#/part>

10 15

Re. I miss OO
by Philippos Apolinarius 26 Nov '09

26 Nov '09

My experience with objects comes from Common List, Clean, Hasekell and Nice. In all these languages, the function behavior is determined by many objects. I think that this is more powerful and clear than the Java way. In Nice one can see the superiority of type-driven behavior over the Java dot notation, since the dot notation is a particular case of the type driven behavior. To make a long story short, one can apply the dot notation to the first argument, or put it together with the other arguments. For instance, consider the followin init() function (entirely in dot notation): c l a s s DrawLines ext ends Applet { Button ext = new Button ( ”Exi t ” ) ; Button dbutton= new Button ( ”Exec” ) ; TextFi e ld t f= new TextFi e ld ( 1 5 ) ; i n t xx= 5 ; i n i t ( ) { this.setBackground ( Color . l ightGray ) ; t h i s . add ( dbutton ) ; t h i s . add ( t f ) ; t h i s . add ( ext ) ; t h i s . setLayout ( n u l l ) ; ext . r e shape (50 , 30 , 50 , 2 0 ) ; dbutton . r e shape ( 50 , 80 , 80 , 3 0 ) ; t f . r e shape (140 , 80 , 200 , 3 0 ) ; } ... etc. } However, in Nice the method is selected not only by the dotted object, but by all arguments. This becomes clear by placing the dotted object inside the argument list: c l a s s DrawLines ext ends Applet { Button ext = new Button ( ”Exi t ” ) ; Button dbutton= new Button ( ”Exec” ) ; TextFi e ld t f= new TextFi e ld ( 1 5 ) ; i n t xx= 5 ; i n i t ( ) { setBackground (this, Color . l ightGray ) ; add (this, dbutton ) ; t h i s . add ( t f ) ; add (this, ext ) ; setLayout (this, n u l l ) ; reshape (ext, 50 , 30 , 50 , 2 0 ) ; reshape (dbutton, 50 , 80 , 80 , 3 0 ) ; reshape (tf, 140 , 80 , 200 , 3 0 ) ; } ... etc. } In order to see how useful and practical is the generalization of dot selection, let us suppose that one needs to write Lisp-like lists in Nice. I am using Nice because it has both the simpler, more restricted dot notation as Java and Python, and the argument selection, more general and powerful, as Haskell and Lisp. Here is the Nice definition of polymorphic lists: import java . i o . * ; class Lst<T> { T head ; ?Lst<T> t a i l ; } ?Lst<int> cons ( i n t x , ?Lst<int> xs ) { ?Lst<int> newList= new Lst ( head : x , tail : xs ) ; return ( newList ) ; } ?Lst<String> cons ( String x , ?Lst<String> xs ) { ?Lst<String> newList= newLst ( head : x , tail : xs ) ; return ( newList ) ; } String car (? Lst<String> xs ) { if ( xs==null ) return ( "" ) ; else return ( xs.head ) ; } int car (? Lst<int> xs ) { if ( xs==null ) return ( 0 ) ; else return ( xs.head ) ; } boolean isEmpty (? Lst<String> xs )= xs==null ; ?Lst<String> cdr (? Lst<String> xs ) { if ( xs== null ) return ( xs ) ; else return ( xs.tail ) ; } ?Lst<String> cdr (? Lst<String> xs ) { if ( xs== null ) return ( xs ) ; else return ( xs.tail ) ; } ?Lst<int> cdr (? Lst<int> xs ) { if ( xs== null ) return ( xs ) ; else return ( xs.tail ) ; } void main ( String [ ] args ) { InputStreamReader converter = new InputStreamReader ( System.in ) ; Buf feredReader in = new BufferedReader ( converter ) ; ?String s= "Type a sentence and press <Enter>" ; println ( s ) ; s= in.readLine ( ) ; ?Lst<String> words=null ; StringTokenizerst = new StringTokenizer ( s ) ; while ( st.hasMoreTokens ( ) ) { words= cons ( st.nextToken ( ), words ) ; } var xs= words ; while ( ! isEmpty ( xs ) ) { println ( car ( xs ) ) ; xs= cdr ( xs ) ; } } If you want to see how the above program can be generalized into a full fledged Lisp like stucture, take a look at my page on Nice: www.discenda.org. In any case, since Haskell has the more general method selection, there is no need to have the more restricted dot selector. Nice has both method selectors, but I seldom use the dot selector. --- On Wed, 11/25/09, Michael Mossey <mpm(a)alumni.caltech.edu> wrote: From: Michael Mossey <mpm(a)alumni.caltech.edu> Subject: [Haskell-cafe] I miss OO To: haskell-cafe(a)haskell.org Received: Wednesday, November 25, 2009, 1:51 PM I'm fairly new to Haskell, and starting to write some big projects. Previously I used OO exclusively, mostly Python. I really miss the "namespace" capabilities... a class can have a lot of generic method names which may be identical for several different classes because there is no ambiguity. In my musical application, many "objects" (or in Haskell, data) have a time associated with them. In Python I would have an accessor function called "time" in every class. So if I have objects/data note1, cursor1, and staff1, Python: note1.time() cursor1.time() staff1.time() Haskell needs something like note_time note1 cursor_time cursor1 staff_time staff1 which is a lot more visually disorganized. What's worse, I have a moderate case of RSI (repetitive strain injury) so I type slowly and depend on abbreviations a lot. I use the souped-up abbreviation capabilities of Emacs. Let's say I have a field/member-variable called orientedPcSet that is used across many classes. In Python, I can create an abbreviation for that and it is useful many times. In Haskell, I might need someType_orientedPcSet someOtherType_orientedPcSet thirdType_orientedPcSet which prevents me from using abbreviations effectively (especially the dynamic-completion feature). (It would help to make the underscore not part of word syntax, but that's not ideal.) So I'm thinking of moving to a scheme in Haskell using modules, most types being defined in their own modules, and doing qualified imports. Generic names like 'time' can be defined in each module w/o clashing. Then I have Note.time note1 Cursor.time cursor1 Staff.time staff1 This is very useful because I can define abbreviations for the type name and for oft-used accessor function names and these abbrevs are more organized, easier to remember, and easier to combine. I would be interested in comments... is this a good way to do things? Am I trying too hard to impose OO on Haskell and is there a better way? Thanks, Mike _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe(a)haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe resizeLeftPane();gLaunchProfile.start('RT_AD_FOOT'); __________________________________________________________________ The new Internet Explorer® 8 - Faster, safer, easier. Optimized for Yahoo! Get it Now for Free! at http://downloads.yahoo.com/ca/internetexplorer/

1 0

ANNOUNCE: feldspar-language
by Emil Axelsson 25 Nov '09

25 Nov '09

I'm happy to announce the first release of Feldspar, which is an embedded domain-specific language with associated code generator mainly targeting DSP algorithms. The language is developed in cooperation by Ericsson, Chalmers University and Eötvös Loránd University. Feldspar stands for *F*unctional *E*mbedded *L*anguage for *DSP* and *PAR*allelism. The language front-end is available on Hackage: http://hackage.haskell.org/package/feldspar-language The back-end C code generator will be uploaded and announced shortly. For more information, see: http://feldspar.sourceforge.net/ / Emil

5 13

ANN: mecha-0.0.4
by Tom Hawkins 25 Nov '09

25 Nov '09

Mecha is a little constructive solid modeling language intended for 3D CAD. This release adds animation capabilities, which use POVRay and FFmpeg behind the scenes. At work we've used Mecha to illustrated the kinematics of a new hydraulic pump design -- I wish I could post the animation, it's pretty cool to watch. http://hackage.haskell.org/package/mecha/

1 0

ANN: atom-0.1.2
by Tom Hawkins 25 Nov '09

25 Nov '09

Atom is a DSL for designing hard realtime embedded software with Haskell. This release adds guarded division operations, 'phase', a new scheduling constraint, and a new rule scheduling algorithm. Many thanks to Lee Pike for his contributions! (Lee, sorry it took so long to get this out.) http://hackage.haskell.org/package/atom/

1 0

Scrap your boilerplate traversals
by rodrigo.bonifacio 25 Nov '09

25 Nov '09

2 1

Pointfree rank-2 typed function
by Bas van Dijk 25 Nov '09

25 Nov '09

Hello, Given this program: ------------------------------------------------------------ {-# LANGUAGE Rank2Types #-} newtype Region s a = Region a unRegion :: forall a s. Region s a -> a unRegion (Region x) = x runRegionPointfull :: forall a. (forall s. Region s a) -> a runRegionPointfull r = unRegion r ------------------------------------------------------------ Is it possible to write the rank-2 typed function 'runRegionPointfull' in pointfree style? Unfortunately the following doesn't typecheck: runRegionPointfree :: forall a. (forall s. Region s a) -> a runRegionPointfree = unRegion Couldn't match expected type `forall s. Region s a' against inferred type `Region s a1' In the expression: unRegion In the definition of `runRegionPointfree': runRegionPointfree = unRegion Why can't the typechecker match `forall s. Region s a' and `Region s a1'? Thanks, Bas

4 5

surrogate code points in a Char
by Manlio Perillo 25 Nov '09

25 Nov '09

Hi. The Unicode Standard (version 4.0, section 3.9, D31 - pag 76) says: """Because surrogate code points are not included in the set of Unicode scalar values, UTF-32 code units in the range 0000D800 .. 0000DFFF are ill-formed""" However GHC does not reject this code units: Prelude> print '\x0000D800' '\55296' Is this a correct behaviour? Note that Python, too (2.5.4, UCS4 build, Linux Debian), accept these code units. Thanks Manlio

4 3

HOpenGL and freeglut rendering problems
by Eitan Goldshtrom 25 Nov '09

25 Nov '09

Hello. I'm new to this mailing list, so I apologize if this question is inappropriate for this list, but I've been looking for a solution to this problem for weeks and I've had no luck. I am trying to write a program with HOpenGL and freeglut, but I can't seem to get it to render. I'm running Ubuntu 9.10 on a DELL 1555 with an ATI Radeon HD 4500. Right now my program just creates a window with a black background. However, when I try to run the program I get the following error: "Unable to create direct context rendering for window 'IGL' This may hurt performance." I've read that this is because of the fglrx driver. The driver uses indirect rendering for OpenGL, but freeglut requires direct rendering? Is there a way to force freeglut to function with indirect rendering? -Eitan

2 1

Machine Learning Library (SVM)
by Hector Guilarte 25 Nov '09

25 Nov '09

Hello cafe, Does anybody knows if there is a Machine Learning Library for Haskell? I looked in hackage and couldn't find anything but something for Data Mining but that's not what I need, however, googling I saw a ticket for google summer of code for writing such library proposed by Ketil Malde. Ketil, has any progress been made on that library? Specially in the SVM part which is what I'm really looking for... Thanks to everyone in advance, Hector Guilarte

3 2

ANNOUNCE managing cabal dependencies using nix and hack-nix
by Marc Weber 25 Nov '09

25 Nov '09

First of all: This is a release (very) early and often release announcment. So expect that there are some minor glitches [5]. Linux is only supported at this moment. [1] summary: ======== main goal: provide an environment (= list dependencies) to build a haskell package with minimal efforts. The two repositories git://github.com/MarcWeber/haskell-nix-overlay.git git://github.com/MarcWeber/hack-nix.git enable you to build dependencies required to build a specific cabal project automatically. In some way its similar to what cabal-install provides. However haskell packages are installed using the nix package manager which allows you installing arbitrary versions of the same packages at the same time on the same system. Follow their READMEs to get latest updates. what is nix? ============ See http://nixos.org. Brief: its a package manager utilizing a lazy, interpreted language called nix to describe package dependencies. Packages can be installed into user environments. Atomic updates and rollbacks are some of its key features as well as allowing the user / or system to install additional versions of a package without breaking previously installed software. [2] I won't go into details here. repo haskell-nix-overlay: ===================== This contains a sketchy implementation of a dependency solver for cabal packages using a brute force algorithm [6]. It also contains a set of patches to make hackage packages compile. hack-nix creates a copy of the hackage index file 00-index.tar called hackage/hackage-nix-db.nix which can be read by the nix language applying some optimizations. You run the solver by telling it about your target packages and their cabal flags. [3] globalFlags = { base4 = true; } packageFlags = { Cabal-1.4.4.splitBase = true; }; targetPackages = [ "happy" "HAppS-Server" "haskell-src" ]; I only pasted the most important parameters here. So what is this all for? Many existing package managers assume that there is only one true way to install packages - using the versions which got packaged. You want to switch from base-3 to base-4 ? You want to use both? Some package build with parsec-2 others require parsec-3? Out of luck(?) Maybe you end up using different users, installing all packages manually into local (user) databases. Also determining which packages must be recompiled is a tedious job. So you updated a package and you have recompiled depending packages. Then you notice that you want to fix a small bug in an app you didn't update for ages.. however the old versions of your libraries have been replaced with newer ones.. usage example ============== Let me introduce you to a small hack-nix workflow showing you how I think you should use it: # get a cabal package. vcs clone xxxx # tell hack-nix about package profiles. A profile is a name associated # with cabal flags: echo "default:-split-base" > .hack-nix-cabal-config # run hack-nix to build all dependencies required by xxxx [3] # and create a file exporting PATH and GHC_PACKAGE_PATH # you should source that in your bash or zsh session hack-nix --build-env default source hack-nix-envs/default/source-me/haskell-env ghc --make Setup.hs ./Setup configure # optionally repeat the cabal flags here [4] ./Setup build # the package bulids? fine. Now you can register it at your nix # configuration file ~/.nixpkgs/config.nix after creating a dist file # and an unmodified representation of the cabal file: hack-nix --to-nix cat >> ~/.nixpkgs/config.nix << EOF {pkgs, ... }: { hackNix.additionalPackages = [ (import $PATH_TO_CABAL_REPO/dist/$CABAL_PROJECT_NAME.nix) # repeat the line above for each package ]; } EOF >From now on nix will know about your (dev version?) of the pkg xxxx and it can be used when running hack-nix --build-env in other cabal directories. Let's compare it to cabal install --user here: base -> lib -> otherlib -> target you build a dev version of lib. When running hack-nix --build-env default in the target cabal directory otherlib will be rebuild automatically. nix can also create tag files for you. This is implemented but it's not supported by hack-nix --build-env yet. (TODO) Now you want to clean those many builds get rid of them and tidy up. Just run nix-collect-garbage to remove all packages managed by nix which are no longer referenced by any environment or their previous generations. Generations? This means that if updating an environment causes more trouble to than it solves you can temporarily switch back to the environment you were using before. How to get started? =================== See [5], read those READMEs. Tell me about your problems. Right now HAppS-Server and hack-nix can be built easily. More work has to be done to make all packages compile. This usally means replacing "base < 4" by "base < 5" or such. Another cause of failure is that C-lib dependencies such as gtk, zlib or happ & alex have to be added manually once only. issues: nix will install its own glibc which dosen't cope with all kernels. You an use kind of native builds. I don't have experiences using them. I'm using nixos so I don't care anyway. speed: for speed reasons I propase only adding latest hackage packages. However you can have different databases or a filter can be implemented to disable certain packages to speed up calculations. Last resort: reimplement it in C putting code aside nix interpreter code. random notes: you can build many packages at the same time utilizing multiple cores using the nix-env -j flag of course many processes are started to build each package. So it definitely is a lot slower than using cabal-install which doesn't spawn processes for each cabal built. Maybe cabal-install and haskell-nix-overlay can be made sharing some patches. [..] If you're interested reply or contact me on irc to make me post about updates and major changes. Thanks for listening and for any feedback in advance. Marc Weber NOTES: [1]: Of course nix runs on cygwin as well. However nothing has been tested so quite some effort has to be spent making this work on Windows as well. [2]: If you have a dependency chain glibc -> lib -> executable ` -> executable2 and lib got some security reinstalling executable will yield: glibc -> lib -> executable `-> lib' -> executable2 so you have to update executable to make it use executable2 as well. This all is done by putting each packgae into its own /nix/store/hash-name/ directory where hash is based on all build inputs. You can think about those hashes similar you do when thinking about git hashes. If a patch / package changes all hashes of depending packages / patches will change. If you want to have more details read about nix on the official homepage.G [3] hack-nix --build-env does a lot of stuff: - it reads the cabal file and writes a nix file containing the cabal contents - it creates more nix files in hack-nix-envs/nix Example: http://github.com/MarcWeber/hack-nix/tree/master/hack-nix-envs/nix/ I committed those so that you can bootstrap hack-nix. default9.nix is the nix representation of the cabal package. However the version has been changed to 9999. This is done to identify your development version of this package. Thus default.nix wants to build this version: targetPackages = [{ n = "hack-nix"; v = "99999"; }]; hack-nix itself isn't built. But it's used to gather its dependencies. - then it realises that env derivation. Right now the solver will output many debugging lines to help you find out why it failed finding a solution. You can this off by debugS = false; [4] this can be done more convenient using scion. [5] help about nix: try #nixos on irc.freenode.net or its mailinglist. help about hack-nix: contact me on irc or by mail. I will try to keep the READMEs up to date. [6] At the first glance this sounds bad because: Each package can have different flag settings defining a different sets of dependencies. Each dependency declaration be satisfied by different versions of a package. So the amount of solutions to be inspected explodes. Nix isn't the best fit to write such a solver so it's quite slow. However limiting the ways a package can be built by - only adding latest package versions from hackage - setting some global flags (such as use base-4.*) seems to make the system fast enough for everydays use. I'm sorry that I didn't manage to find a better algorithm in reasonable time. If I had to say thank you to some people this list would include dccouts (for his support on Cabal), Saizan (who helped me by talking to me), the nix(os) dev team, nominolo (for his work on scion), and many others I don't even know about.

1 0

Where is `newTVarIO` defined ?
by zaxis 25 Nov '09

25 Nov '09

I cannot hoogle it. It appears in Pugs: run' ("-d":rest) = do info <- fmap Just (io $ newTVarIO Map.empty) let ?debugInfo = info run' rest Sincerely! ----- fac n = foldr (*) 1 [1..n] -- View this message in context: http://old.nabble.com/Where-is-%60newTVarIO%60-defined---tp26504967p2650496… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

3 3

Haskell Weekly News: Issue 140 - November 22, 2009
by jfredett＠gmail.com 24 Nov '09

24 Nov '09

--------------------------------------------------------------------------- Haskell Weekly News http://sequence.complete.org/hwn/20091122 Issue 140 - November 22, 2009 --------------------------------------------------------------------------- Welcome to issue 140 of HWN, a newsletter covering developments in the [1]Haskell community. Apologies for the somewhat late edition, I got back late from the NES/MAA conference yesterday in Springfield, MA, and was generally too exhausted from all the math competing and giving of talks that HWN could not compete with the appeal of sleeping... This week there was a new edition of the HCAR, plenty of good discussion about Iteratee's and the Type Directed Name Resolution proposal, altogether a busy week. So here it is, your Haskell Weekly News! Announcements [BostonHaskell] Next meeting: November 24th at MIT (32-G882). Ravi Nanavati [2]announced the next meeting of BAHUG. Haskell Communities and Activities Report (17th ed., November 2009). Janis Voigtlaender [3]announced the new edition of the Haskell Communities and Activities Report. Call for Participation - PEPM'10 (co-located with POPL'10). Janis Voigtlaender [4]announced a call for participation for PEPM 2010. LambdaCube engine and Bullet physics binding. Csaba Hruska [5]announced a binding to the LambdaCube and Bullet engines. ICFP '10: Second call for workshop proposals. Wouter Swierstra [6]announced a second call for workshop proposals for ICFP 2010. deepseq-1.0.0.0. Simon Marlow [7]announced version 1.0.0.0 of `deepseq` wcwidth-0.0.1. Jason Dusek [8]announced a small package which provides binding to wchar.h, which assigns a column width to unicode characters. gnome-keyring 0.1 (bindings to libgnome-keyring). John Millikin [9]announced a set of bindings to the GNOME keyring libraries. attempt. Michael Snoyman [10]announced a new release of the `attempt` package. control-monad-failure and safe-failure. Michael Snoyman [11]also announced a new version of `control-monad-failure` and `safe-failure`. Announcing the GHC Bug Sweep. Simon Marlow [12]announced the GHC bug sweep, to help weed out the GHC Trac of old bugs, and also to get warm fuzzy feelings from helping everyone's favorite compiler devs. New Industrial Haskell Group membership options. Duncan Coutts [13]announced some new membership options for the the Industrial Haskell Group (IHG) bindings-SDL 1.0.2, the domain specific language for FFI description. Mauricio Antunes [14]announced a new version of the bindings-SDL package. wxHaskell 0.12.1.2. Jeremy O'Donoghue [15]announced a release of the wxHaskell package, including new improved support for installation via cabal on any system, with only a minor caveat on Windows. TFP 2010 - Call for Papers. TFP 2010 [16]announced a call for papers for TFP 2010, the 11th symposium on Trends in Functional Programming. Reminder: Fun in the afternoon, MSR Cambridge, 26 Nov. Simon Marlow [17]announced a final reminder for the `Fun in the Afternoon` meeting, which will be at MSR Cambridge on the 26th of November (ED: Thanksgiving for us Americans, if only there were some way to combine turkey-oriented gluttony with Functional programming...). Job at the University of Technology in Cottbus. Wolfgang Jeltsch [18]announced a job opening at the University of Technology in Cottbus. Scottish Category Theory Seminar. Conor McBride [19]announced the first meeting of Scottish Category Theory Seminar, a forum for discussion of all aspects of Category Theory, be they pure or applied. (ED: I am fighting very hard to not make some sort of Braveheart Joke...) Discussion Iteratee question. Valery V. Vorotyntsev [20]asked about using iteratee's in his binary data parser code. Haskell as an alternative to Java. Philippos Apolinarius [21]wondered whether Haskell would make for a good Java alternative. Status of TypeDirectedNameResolution proposal? Levi Greenspan [22]asked about the status of the TDNR proposal. Typef*ck: Brainf*ck in the type system. Johnny Morrice [23]showed us his implementation of everyone's favorite profane programming language... in the type system. Could someone teach me why we use Data.Monoid? Magicloud Magiclouds [24]requested some insight to why we use monoids so much in Haskell, leading to a fantastic discussion of all the myriad places Monoids pop up in both Haskell and in Math in general. Blog noise [25]Haskell news from the [26]blogosphere. Blog posts from people new to the Haskell community are marked with >>>, be sure to welcome them! * Neil Brown: [27]The Operators and Monoids of CHP. * Philip Wadler: [28]A list is an odd creature, take 2. * Darcs: [29]darcs hacking sprint 3 report. * Mikael Vejdemo Johansson (Syzygy-): [30][MATH198] Lecture 9 posted and lectured. * Gergely Patai: [31]LambdaCube and Bullet on Hackage at last. * David Amos: [32]Three new modules in HaskellForMaths. * Darcs: [33]darcs weekly news #46. * Christophe Poucet (vincenz): [34]Setting up iptables to throttle incoming ssh. * Ivan Lazar Miljenovic: [35]Waddaya know, testing WORKS!. * Neil Mitchell: [36]Reviewing View Patterns. * Neil Brown: [37]An Introduction to Communicating Sequential Processes. * Joachim Breitner: [38]Darcs Hacking Sprint: Mission Complete. * Ivan Lazar Miljenovic: [39]Past, Present and PEPM. * Erik de Castro Lopo: [40]Hacking DDC.. * Dan Piponi (sigfpe): [41]Haskell Monoids and their Uses. * Joachim Breitner: [42]Arrived at the Darcs hacking sprint. Quotes of the Week * Apocalisp: You can't have your baby and eat it too * tensorpudding: so you boil lisp for an hour to sift out the parentheses and impurities, make a whitespace sauce with liberal syntactic sugar, and you have haskell a la mode * ddarius: I'm not aware of anything (including C++) that can seamlessly talk to C++ code. * ksf: is Data.Data.Data some kind of reference to swedish chefs? * IceDane: [on escaping an imperative mindset]: <kmc> i recommend heavy drinking <IceDane> I've tried that. I just have fun and wake up and feel like shit the day after. but still think in loops. * jpet: Ok, after studying the generated core a bit, I can conclude that generated core is somewhat hard to follow. * Adamant: [on the update complexity of Data.Map] I read that as 'Oleg(n)' * skorpan: I did not have impure relations with that language About the Haskell Weekly News New editions are posted to [43]the Haskell mailing list as well as to [44]the Haskell Sequence and [45]Planet Haskell. [46]RSS is also available, and headlines appear on [47]haskell.org. To help create new editions of this newsletter, please see the information on [48]how to contribute. Send stories to jfredett . at . gmail . dot . com. The darcs repository is available at darcs get [49]http://patch-tag.com/r/jfredett/HWN2/pullrepo HWN2 . References 1. http://haskell.org/ 2. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66609 3. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66594 4. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66530 5. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66523 6. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66510 7. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66445 8. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66441 9. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66440 10. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66413 11. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66408 12. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66396 13. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66395 14. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66383 15. http://article.gmane.org/gmane.comp.lang.haskell.cafe/66279 16. http://thread.gmane.org/gmane.comp.lang.haskell.general/17631 17. http://article.gmane.org/gmane.comp.lang.haskell.general/17627 18. http://article.gmane.org/gmane.comp.lang.haskell.general/17625 19. http://article.gmane.org/gmane.comp.lang.haskell.general/17623 20. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/66601 21. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/66511 22. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/66431 23. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/66398 24. http://thread.gmane.org/gmane.comp.lang.haskell.cafe/66223 25. http://planet.haskell.org/ 26. http://haskell.org/haskellwiki/Blog_articles 27. http://chplib.wordpress.com/2009/11/20/the-operators-and-monoids-of-chp/ 28. http://wadler.blogspot.com/2009/11/list-is-odd-creature-take-2.html 29. http://blog.darcs.net/2009/11/darcs-hacking-sprint-3-report.html 30. http://blog.mikael.johanssons.org/archive/2009/11/math198-lecture-9-posted-… 31. http://just-bottom.blogspot.com/2009/11/lambdacube-and-bullet-on-hackage-at… 32. http://haskellformaths.blogspot.com/2009/11/three-new-modules-in-haskellfor… 33. http://blog.darcs.net/2009/11/darcs-weekly-news-46.html 34. http://blog.poucet.org/2009/11/setting-up-iptables-to-throttle-incoming-ssh/ 35. http://ivanmiljenovic.wordpress.com/2009/11/17/waddaya-know-testing-works/ 36. http://neilmitchell.blogspot.com/2009/11/reviewing-view-patterns.html 37. http://chplib.wordpress.com/2009/11/16/an-introduction-to-communicating-seq… 38. https://www.joachim-breitner.de/blog/archives/350-Darcs-Hacking-Sprint-Miss… 39. http://ivanmiljenovic.wordpress.com/2009/11/15/past-present-and-pepm/ 40. http://www.mega-nerd.com/erikd/Blog/CodeHacking/DDC/hacking_ddc.html 41. http://blog.sigfpe.com/2009/01/haskell-monoids-and-their-uses.html 42. https://www.joachim-breitner.de/blog/archives/349-Arrived-at-the-Darcs-hack… 43. http://www.haskell.org/mailman/listinfo/haskell 44. http://sequence.complete.org/ 45. http://planet.haskell.org/ 46. http://sequence.complete.org/node/feed 47. http://haskell.org/ 48. http://haskell.org/haskellwiki/HWN 49. http://patch-tag.com/r/jfredett/HWN2/pullrepo%20HWN2

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Status of TypeDirectedNameResolution proposal?
by Levi Greenspan 24 Nov '09

24 Nov '09

What's the status of the TDNR proposal [1]? Personally I think it is a very good idea and I'd like to see it in Haskell'/GHC rather sooner than later. Working around the limitations of the current record system is one of my biggest pain points in Haskell and TDNR would be a major improvement. Thus I wonder if someone is actively working on this proposal? Thanks, Levi. ---------------- [1] http://hackage.haskell.org/trac/haskell-prime/wiki/TypeDirectedNameResoluti…

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Re: [Haskell] Announcing Haskell 2010
by Simon Marlow 24 Nov '09

24 Nov '09

On 24/11/2009 15:19, David Leimbach wrote: > First off congratulations everyone! > > Second, Oh shit! Graham Hutton's excellent Haskell introduction book is > now not valid Haskell 2010 due to N+K patterns? Right, but it's still valid Haskell 98, and we have no immediate plans at least in GHC to drop support for Haskell 98. It will probably not be the default in 6.14.1, though. Cheers, Simon > I loaned that book to my boss and he's really enjoyed it. I guess I'll > have to buy a revised copy. Can we get an update to it? :-) > > I realize N+K was considered dangerous > > On Tue, Nov 24, 2009 at 2:50 AM, Simon Marlow <marlowsd(a)gmail.com > <mailto:marlowsd@gmail.com>> wrote: > > I'm very proud to announce a new revision of the Haskell language, > Haskell 2010. Over the last couple of months the committee has been > making final decisions about which extensions should be a part of > this revision. The final list is: > > DoAndIfThenElse > HierarchicalModules > EmptyDataDeclarations > FixityResolution > ForeignFunctionInterface > LineCommentSyntax > PatternGuards > RelaxedDependencyAnalysis > LanguagePragma > NoNPlusKPatterns > > You can read more about each one, including rationale for and > against, on its relevant wiki page, which are linked from the tickets: > > http://hackage.haskell.org/trac/haskell-prime/query?status=new&status=assig… > <http://hackage.haskell.org/trac/haskell-prime/query?status=new&status=assig…> > > Haskell 2010 is a small but significant step on the road that was > started by the Haskell' committee 4 years ago, The process has not > been a smooth one, and there have been several changes of direction, > but the current process is actually producing concrete results that > let us move the language forward in positive steps, so I feel we're > on the right track. > > We all owe the current committee a big thank-you for sticking with > the process this long: most of them didn't realise the magnitude of > what they were signing up for at the beginning. The short list of > changes above tells only a small part of the story, there is a > wealth of wiki content and mailing-list discussion that future > language revisions can draw on. > > So what now? > > * We will produce a revised version of the Haskell language report > incorporating these changes. That will happen over the next few > months. > > * Compilers can start implementing the changes, and flags to > select the Haskell 2010 revision. In GHC we expect to have > support in the next major release, i.e. 6.14.1. > > * Right now, we will start forming a Haskell 2011 committee to > mange the process of deciding on changes for next year's revision. > The current committee is still discussing how to go about > finding a new committee (the plan is to at least have open > nominations) but I expect to be able to announce more details > very soon. > > * Everyone can participate in the Haskell 2011 process, by discussing > and refining proposals. Information about how to do that is on > the Haskell Prime wiki: > http://hackage.haskell.org/trac/haskell-prime/wiki > > Remember: this is a community effort. The changes that get > adopted in each revision are drawn from the pool of fully-specified > proposals, and those proposals can be written by anyone. > > Thanks, > > Simon, on behalf of the Haskell 2010 committee > > _______________________________________________ > Haskell mailing list > Haskell(a)haskell.org <mailto:Haskell@haskell.org> > http://www.haskell.org/mailman/listinfo/haskell > >

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Re: Haskell-Cafe Digest, Vol 75, Issue 51
by Johnny Morrice 24 Nov '09

24 Nov '09

> 1) the uncensored version > 2) Monadam* > 3) Monada** > 4) Monad*** > 5) Mona**** Putting stars in place of letters in no way makes a word less offensive. Consider the word '****ing'. It's about context. I think it's wise that such a word have a star put in it in the weekly news or a journal article as it shows the author is less bombastic and doesn't want to use loud language - which counts for a lot in other's opinions. Johnny

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Idea for a very simple GUI llibrary
by Maurício CA 24 Nov '09

24 Nov '09

Hi, Here is a sketch for a library with these properties: -> Easy to test. All Haskell code can be tested in a text terminal. Also, testing code that uses the library can also be done without using a GUI. -> Extremely easy to document and use. -> Not even close to Gtk2hs power, but enough for small applications. -> Could be the first GUI to build on hackage :) What we need is: -> MyState. A user suplied type for application state. -> WidId. A user suplied type for widget identifiers. -> Gui wi. A type capable of describing an interface with all of its state. It's an instance of Eq. -> Event wi. A type for events. -> Prop. A type for properties than can related to a WidId. Running an application would be like this: main = runGUI initState -- An initial MyState. event -- :: MyState -> DiffTime -> Event WidId -> MyState props -- :: WidId -> [Prop] action -- :: MyState -> DiffTime -> IO (Maybe (MyState,Gui WidId)) timeout -- :: DiffTime DiffTime parameters for callbacks are always the time elapsed since application started. From initState and event, the implementation of runGUI can save a state that optionally changes with time. From props, it can get details on what to present in widgets associated with a WidId (selected state, picture to draw etc.). action presents a chance for using IO, and optionally change state and GUI description. timeout is the maximum time runGUI implementation is allowed to wait between calls to action. Examples for those types: newtype MyState = { lastUpdate :: DiffTime, builtGui :: Bool, earthCoordinates :: (Double,Double), map :: SVG, ... } data WidId = XCoord | YCoord | MapWindow | ReloadButton ... data Gui widid = TitleWindow (Gui widid) | Tabs [(String,Gui widid)] | PressButton String widid | Selection [String] widid | ... deriving Eq {- Eq is needed by runGUI to detect if GUI has changed after the last call to action. -} data Event widid = ButtonPressed widid | FileSelected String widid | OptionSelected String widid | ... data Prop widid = Active Bool | Text String | Draw SVG | ... I believe this can represent most kinds of simple applications, and be efficient enough for practical use. It's interesting that all of this can be designed, implemented and tested independent of runGUI implementation. Actually, if you want a pet project and want to write and design the Haskell part, I may probably be able to write runGUI for you :) Best, Maurício

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Some useful TH templates
by Yair Chuchem 23 Nov '09

23 Nov '09

Hi, I wrote some Template Haskell templates that I think may be of use to others. The first generates "in" and "with" functions for newtypes. For example, using it one can replace this code (from TypeCompose): > inFlip :: ((a~>b) -> (a' ~~> b')) -> (Flip (~>) b a -> Flip (~~>) b' a') > inFlip = (Flip .).(. unFlip) > > inFlip2 :: ((a~>b) -> (a' ~~> b') -> (a'' ~~~> b'')) > -> (Flip (~>) b a -> Flip (~~>) b' a' -> Flip (~~~>) b'' a'') > inFlip2 f (Flip ar) = inFlip (f ar) > > inFlip3 :: ((a~>b) -> (a' ~~> b') -> (a'' ~~~> b'') -> (a''' ~~~~> b''')) > -> (Flip (~>) b a -> Flip (~~>) b' a' -> Flip (~~~>) b'' a'' -> Flip (~~~~>) b''' a''') > inFlip3 f (Flip ar) = inFlip2 (f ar) with this code: > {-# LANGUAGE TemplateHaskell #-} > import Data.Newtype > $(mkInNewtypeFuncs [1..3] ''Flip) The second template is for accessing ADTs in the Maybe monad. For example: > {-# LANGUAGE TemplateHaskell #-} > import Data.ADT.Getters > data Blah a = NoBlah | YesBlah a | ManyBlah a Int > $(mkADTGetters ''Blah) Generates: > gNoBlah :: Blah a -> Maybe () > gYesBlah :: Blah a -> Maybe a > gManyBlah :: Blah a -> Maybe (a, Int) I'm more than willing to upload these templates to hackage (or rather, split them out of an unrelated package), but all I need is a suggestion for a package name :) For now you can find these here: http://hackage.haskell.org/package/peakachu Hoping someone else will find it useful, cheers, Yair

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Wiki software?
by Günther Schmidt 23 Nov '09

23 Nov '09

Hi, I'm finally about to organize myself, somewhat. And am going to use a wiki for it. Does there a good one exist that's written in Haskell? Günther

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Re: ANNOUNCE: deepseq-1.0.0.0
by Simon Marlow 23 Nov '09

23 Nov '09

On 19/11/2009 11:52, Sittampalam, Ganesh wrote: > Yitzchak Gale wrote: >> Simon Marlow wrote: >>> So then what shall we call the a -> () version? >>> One possibility is to go back to calling it rnf. >> >> In light of apfelmus' comment, I vote for rnf. >> >> And in that case, how about the analogous alternative for seq itself: >> >> hnf :: a -> () > > I think it would be whnf since it doesn't evaluate under lambdas. > > I also vote for rnf, because we should have a good reason for changing > names of things. Various people would prefer rnf. Ok, unless there are any further objections, I'll change the names back to class NFData a where rnf :: a -> () and also add deepseq :: a -> b -> b but I'll leave the module name as Control.DeepSeq. Cheers, Simon

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Kind polymorphism
by Martijn van Steenbergen 23 Nov '09

23 Nov '09

Hello, Are there currently any known problems that would hinder the implementation of kind polymorphism [1], e.g. unresolved inelegancies or technical limitations, or is it only a matter of finding the time to implement it? Thanks, Martijn. [1] http://hackage.haskell.org/trac/haskell-prime/wiki/KindInference

1 0

Graph drawing library for Haskell
by Victor Mateus Oliveira 22 Nov '09

22 Nov '09

Hi, Anyone knows a good library for graph diagram drawing? Or a haskell binding for one? Something like jgraph. http://www.jgraph.com/jgraph.html []s' Victor -- GNU/Linux user #446397 - http://counter.li.org

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