December 2006 - Haskell-Cafe

Re: help with threadDelay
by Neil Davies 04 Dec '06

04 Dec '06

Ian/Simon(s) Thanks - looking forward to the fix. It will help with the real time enviroment that I've got. Follow on query: Is there a way of seeing the value of this interval from within the Haskell program? Helps in the calibration loop. Neil

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RE: Safe forking question
by Simon Marlow 04 Dec '06

04 Dec '06

[ duh, hit send by mistake, message continues... ] Chris Kuklewicz wrote: > forkInheritIO :: IO () -> IO ThreadId -- inherits parent's > block or unblock status > > forkBlockedIO :: IO () -> IO ThreadId -- starts the action in > "block" mode. Must manually "unblock" > Either of these is certainly possible, and I agree that forkBlockedIO is more generally useful than my forkCatchIO. One tantalising possibility is that we could make forkIO have the forkInheritIO behaviour without breaking much code, since I bet forkIO is almost never called inside block. Cheers, Simon

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HaXml problem
by Alexis Hazell 04 Dec '06

04 Dec '06

Hi all, Say i have data of type Content, and i want to put that data into a type which is an instance of XmlContent, so that i can use it with hPutXml. How can i do so? Does it involve the List1 type and its NonEmpty constructor? Thanks in advance, Alexis.

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Generate 50 random coordinates
by Huazhi (Hank) Gong 04 Dec '06

04 Dec '06

Hello,all My intention is to generate 50 random coordinates like (x,y). myrand :: Int myrand = randomRIO(1::Int, 100) rf=[(myrand, myrand) | a <- [1..50]] My short program is like this. However, GHCI say that the return type of randomRIO is IO a while the function defined by me is Int. Since I only need a integral type as my cooridinate, could you tell me how to fix this? Hank -- View this message in context: http://www.nabble.com/Generate-50-random-coordinates-tf2742242.html#a7651116 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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complex state code
by Tim Newsham 03 Dec '06

03 Dec '06

I'm working on some code where I have some complex state. This is the first time I've dealt with anything like this in haskell. If anyone would review my code and let me know if there are ways I could do this better, cleaner, in a more idiomatic way, etc, I would greatly appreciate it. http://www.thenewsh.com/~newsham/Market.hs Tim Newsham http://www.thenewsh.com/~newsham/

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compiler versus interpreter
by jepalomar23＠ono.com 03 Dec '06

03 Dec '06

I am programming an application with a lot of interactivity. When using x<-getChar the character corresponding to the pushed key is assigned to x immediately. Launching the module through runghc works properly. However, the compiled module through ghc requires to push return after the character key in order to complete the assignation procedure. It is a bug or there is some difference between compiler an interpreter? Thanks in advance. jepalomar

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Functional GUI combinators for arbitrary graphs of components?
by Brian Hulley 03 Dec '06

03 Dec '06

Hi, I've been looking at the Fudgets research (http://www.cs.chalmers.se/ComputingScience/Research/Functional/Fudgets/ ) as an example of a purely functional gui. Afaiu a brief summary is that a Fudget can represent a GUI widget or some other object, which can have some internal state, and which receives and passes messages to the other Fudgets it is connected to. Fudgets are connected to each other by combinators eg: second >==< first -- sequential (first sends messages to second) a >*< b -- parallel There is a continuation passing implementation such that the messages are passed and internal states of Fudgets are updated (by replacing each fudget with an updated fudget) as these expressions are evaluated hence the message passing and maintenance of state doesn't involve any IORefs though interaction with external devices such as the OS uses IO. Anyway to get to my point, though all this sounds great, I'm wondering how to construct an arbitrary graph of Fudgets just from a fixed set of combinators, such that each Fudget (node in the graph) is only mentioned once in the expression. To simplify the question, assume we have the following data structure to describe the desired graph: data LinkDesc a = Series a a | Broadcast a [a] | Merge [a] a type GraphDesc a = [LinkDesc a] and a function to compute a combined object (eg Fudget) corresponding to an arbitrary graph would be: mkObj :: Ord label => Map label Obj -> GraphDesc label -> Obj mkObj = -- ??? The result of mkObj will be some expression, composed from a finite set of combinators applied to the named objects, but with the all important property that each named object appears no more than once in the expression (this is what allows Fudgets to correspond to notional objects which maintain internal state - during evaluation each fudget gets replaced by an updated fudget hence can only appear once in the whole expression). As a very simple example using existing Fudgets combinators, type Map label value = [(label, value)] mkObj [("A", objA), ("B", objB), ("C", objC)] [Series "A" "B", Series "B" "C"] === objC >==< objB >==< objA and mkObj [("A", objA), ("B", objB), ("C", objC)] [Broadcast "A" ["B", "C"]] === (objB >*< objC) >==< objA However: mkObj [("A", objA), ("B", objB), ("C", objC), ("D", objD)] [Broadcast "A" ["B", "C"], Series "B" "D", Series "A" "D"] === ??? The Fudgets library provides many combinators eg for looping, but even so, I don't think there are sufficient combinators to express the above graph (though possibly extra nodes and tagging/untagging would solve this example), or more heavily connected graphs such as: [Series "A" "B", Series "B" "C", Series "C" "D", Series "D" "B", Series "C" "A"] This problem is so general (ie converting a cyclic graph into an expression tree such that each node appears no more than once) that I'm sure someone somewhere must already have determined whether or not there can be a solution, though I don't know where to look or what to search for. Any ideas? Thanks, Brian. -- http://www.metamilk.com

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Difficult memory leak in array processing
by Niko Korhonen 03 Dec '06

03 Dec '06

Hi everyone, I have the following code whose purpose is to add dither (noise) to a given array. The code looks very straightforward but apparently it has a memory leak somewhere. Here I try to run the algorithm for an array of 10,000,000 integers. Ten million unboxed strict integers should equal to 40MB which should pose no problems to any modern system. However, the program fails with a stack overflow error. I'm using GHC 6.6 on Windows with 1 GB of RAM. I've tried applying seq and some other strictness tricks (such as x == x) pretty much everywhere on the code with no results. Could you please help me understand what is going on here? Have I misunderstood something critical in how Haskell works? Here is the relevant portion of the code: module Main where import Data.Array.IO import System.Random type Buffer = IOUArray Int Int -- | Triangular Probability Density Function, equivalent to a roll of two dice. -- The number sums have different probabilities of surfacing. tpdf :: (Int, Int) -> IO Int tpdf (low, high) = do first <- getStdRandom (randomR (low, high)) second <- getStdRandom (randomR (low, high)) return ((first + second) `div` 2) -- | Fills an array with dither generated by the specified function. genSeries :: Buffer -> ((Int, Int) -> IO Int) -> (Int, Int) -> IO () genSeries buf denfun lims = let worker low i | i >= low = do r <- denfun lims writeArray buf i r worker low (i - 1) | otherwise = return () in do (lo, hi) <- getBounds buf worker lo hi main = do -- This should allocate a 40 MB array buf <- newArray_ (0, 10000000) :: IO Buffer -- Fill the array with dither genSeries buf tpdf (2, 12) -- niko.korhonen(a)gmail.com

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Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
by Krasimir Angelov 02 Dec '06

02 Dec '06

Hi Shelarcy, Could you check whether you have this registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\8.0\InstallDir and tell me its value? Typically its value should be such that the following script to work. Set shell = CreateObject("WScript.Shell") vstudioPath = shell.RegRead ("HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\VisualStudio\8.0\InstallDir") shell.Run ("""" & vstudioPath & "devenv.exe"" /Setup",0,true) Cheers, Krasimir On 11/30/06, shelarcy <shelarcy(a)gmail.com> wrote: > Hi Krasimir, > > > On 11/30/06, shelarcy <shelarcy(a)gmail.com> wrote: > >> But ... I can't install Visual Haskell prerelease 0.2. Near > >> the end of install process, Microsoft Development Environment > >> cause error. > On Thu, 30 Nov 2006 17:03:22 +0900, Krasimir Angelov <kr.angelov(a)gmail.com> wrote: > > Could you tell me what error message you see during the installation? > > If it is in Japan then translate it in English ;-). > > It's not good error message. Anyway, I translate it. > > Near the end of install process, error dialog opened and says: > > --- > The problem happende, so exit Microsoft Development Environment. > I'm sorry for causing inconvenience to you. > > (under its message, error dialog has form that send error report > for Microsoft or shows error detail. These messages are not > important, so I don't translate that.) > --- > > And click form that shows error detail, another dialog opened. > It shows: > > --- > :Error ditail: > An unhandled exception has been caught by the VSW exception filter. > :Error Signature: > AppName: devenv.exe AppVer: 7.10.6030.0 ModName: unknown > ModVer: 0.0.0.0 Offset: 00bbbacc > :Report Detail: > (Below meassage attetion to user that error report send what. > So these messages are not important, too.) > --- > > > Also it can help > > if you run the installer with logging: > > > > $ msiexec VSHaskell71.msi /l log.txt > > msiexec doesn't run its command. And error dialog noticed that > you forgot /i optio. So I used below command. > > $ msiexec /i VSHaskell71.msi /l log.txt > > I think log.txt is much more useful than previous messages. > log.txt also has Japanese messages. So I translated that part. > > --- > (snip) > > Action 20:38:17: CA_RegisterHelpFile.3643236F_FC70_11D3_A536_0090278A1BB8. > IHxRegisterSession::ContinueTransaction() returned 0. > Helpfile: C:\Program Files\Visual Haskell\doc\alex.HxS was successfully registered to namespace vs_haskell. > ????elpfile: C:\Program Files\Visual Haskell\doc\building.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\Cabal.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\haddock.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\happy.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\libraries.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\users_guide.HxS was successfully registered to namespace vs_haskell. > Helpfile: C:\Program Files\Visual Haskell\doc\vh.HxS was successfully registered to namespace vs_haskell. > Action 20:38:17: CA_RegisterPlugIn.3643236F_FC70_11D3_A536_0090278A1BB8. > IHxRegisterSession::ContinueTransaction() returned 0. > IHxPlugIn::RegisterHelpPlugIn() returned 0. > Namespace: vs_haskell was successfully plugged into namespace MS.VSCC.2003. > Action 20:38:17: CA_CommitHelpTransaction.3643236F_FC70_11D3_A536_0090278A1BB8. > Action 20:38:17: RegisterProduct. Registering product > RegisterProduct: {FEC3263A-9034-49C5-8C5D-902231009894} > Action 20:38:18: PublishFeatures. Publishing Product Features > PublishFeatures: Feature: Complete > Action 20:38:18: PublishProduct. Publishing product information > 1: {FEC3263A-9034-49C5-8C5D-902231009894} > Action 20:38:18: RollbackCleanup. Removing backup files > IHxRegisterSession::ContinueTransaction() returned 0. > Registration session: {FEC3263A-9034-49C5-8C5D-902231009894} was successfully committed. > RollbackCleanup: File: C:\Config.Msi\fc3d12.rbf > RollbackCleanup: File: C:\Config.Msi\fc3d13.rbf > RollbackCleanup: File: C:\Config.Msi\fc3d14.rbf > RollbackCleanup: File: C:\Config.Msi\fc3d15.rbf > RollbackCleanup: File: C:\Config.Msi\fc3d16.rbf > Action ended 20:38:18: InstallFinalize. Return value 1. > Action 20:38:18: CA_HxMerge_VSCC.3643236F_FC70_11D3_A536_0090278A1BB8. > Action start 20:38:18: CA_HxMerge_VSCC.3643236F_FC70_11D3_A536_0090278A1BB8. > ????tion ended 20:40:09: CA_HxMerge_VSCC.3643236F_FC70_11D3_A536_0090278A1BB8. Return value 1. > Action 20:40:09: CA_RemoveTempHxDs.3643236F_FC70_11D3_A536_0090278A1BB8. > Action start 20:40:09: CA_RemoveTempHxDs.3643236F_FC70_11D3_A536_0090278A1BB8. > Action ended 20:40:09: CA_RemoveTempHxDs.3643236F_FC70_11D3_A536_0090278A1BB8. Return value 1. > Action 20:40:09: VSHaskellInstall. Register Visual Haskell Plugin > Action start 20:40:09: VSHaskellInstall. > Error 1720. There is a problem with this Windows Installer package. A script required for this install to complete could not be run. Contact your support personnel or package vendor. Custom action VSHaskellInstall script error -2146828275, Microsoft VBScript Runtime Error: Couldn't match types.: 'Return' Line 55, Column 5, > MSI (s) (0C:D4) [20:51:43:359]: Product: Visual Haskell 0.2 for Visual Studio 2003 -- Error 1720. There is a problem with this Windows Installer package. A script required for this install to complete could not be run. Contact your support personnel or package vendor. Custom action VSHaskellInstall script error -2146828275, Microsoft VBScript Runtime Error: Couldn't match types.: 'Return' Line 55, Column 5, > > Action ended 20:51:43: VSHaskellInstall. Return value 3. > Action ended 20:51:43: INSTALL. Return value 3. > Action ended 20:51:43: ExecuteAction. Return value 3. > Action 20:51:43: FatalError. > Action start 20:51:43: FatalError. > Action 20:51:43: FatalError. Dialog created > Action ended 20:51:46: FatalError. Return value 2. > Action ended 20:51:46: INSTALL. Return value 3. > === Logging stopped: 2006/11/30 20:51:46 === > MSI (c) (B8:C4) [20:51:46:046]: Product: Visual Haskell 0.2 for Visual Studio 2003 -- Installation failed. > --- > > > > In the Visual Haskell\bin directory you can see one directory called > > 1033 with vs_haskell_ui.dll in it. vs_haskell_ui.dll contains various > > string resources used in Visual Haskell. For each supported language > > you need to have a different directory and 1033 is the code used for > > English. I don't know the code required for Japan but you can look at > > C:\Program Files\Microsoft Visual Studio 8\VC\bin directory and see > > what code VC++ is using. After that try to rename the 1033 directory > > to what is required for Japan. Tell me whether that works. > > Japanese diretory is 1041. > > After rename it, I tried to use Visual Haskell 0.2. But same error dialog > opened and exit Visual Studio, too. > > > -- > shelarcy <shelarcy capella.freemail.ne.jp> > http://page.freett.com/shelarcy/ >

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Haskell source transformer?
by Dimitry Golubovsky 02 Dec '06

02 Dec '06

Hi, In order to automatize the creation of W3C DOM typesafe wrapper (this is needed for my Haskell->Javascript stuff) I am processing the OMG IDL files that contain interface definitions for DOM methods and attributes with HDirect. It works in general (for some reason it didn't like "boolean" type, so I used a preprocessor to redefine it as "Boolean"), and outputs some Haskell code full of foreign calls, yet it contains what I need: type signatures. For example, for the method "appendChild" it outputs: appendChild :: Node a1 -> Node a0 -> Prelude.IO (Node ()) appendChild newChild iptr = do o_appendChild <- Com.invokeIt (\ methPtr iptr -> Foreign.ForeignPtr.withForeignPtr newChild (\ new unmarshallNode o_appendChild (above lines of code may be truncated, they are just for illustration) This is almost it, but I need to replace the return type (using the JS monad instead of IO), and replace the method implementation with something else, based on unsafeJS. In some other cases I may need to modify type declarations, etc. I know there is a Haskell syntax parser around (maybe, more than one). Does anybody know of any utility based on such parser that does things I need, or rather a library on top of the parser? I just would like to avoid reinventing the wheel. Last thing I want to do is to change sources of HDirect. Thanks. -- Dimitry Golubovsky Anywhere on the Web

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