- Haskell-Cafe - Haskell.org

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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Parsec: Where's +++?
by Greg Fitzgerald 02 Dec '06

02 Dec '06

Koen Claessen's "Parallel Parsing Processes," suggests their parsing combinators have been integrated into Parsec. If so, where is the +++ operator hiding? If not, does anyone know of a parsing library with a choice operator that does breadth-first search? Also, how do I determine what instances a datatype supports? Is Parsec an instance of Applicative? Thanks, Greg

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The Data.Array.* hierarchy is unsafe (or, Segfaulting for fun and profit)
by Spencer Janssen 02 Dec '06

02 Dec '06

I've discovered a problem in the array libraries that allows one to read arbitrary memory locations without the use of any unsafeFoo functions. Both GHC and Hugs are affected. > import Data.Array.IArray > import Data.Array.Unboxed Here is a poorly behaved instance of Ix: inRange and index ignore the bounds supplied. > newtype EvilIx = E Int deriving (Eq, Ord) > instance Ix EvilIx where > inRange _ _ = True > index _ (E i) = i > range (E x, E y) = map E $ range (x, y) One can read arbitrary memory locations, eventually indexing far enough to cause a segmentation fault. > main = print [a ! E (2^i) | i <- [0..]] > where > a :: UArray EvilIx Int > a = array (E 0, E 0) [] This problem is not specific to UArrays: > main' = print [a ! E (2^i) | i <- [0..]] > where > a :: Array EvilIx String > a = array (E 0, E 0) [] The issue is that the array operators trust the Ix instance to manage boundaries correctly. The solution is to double check the value returned by index with the actual length of the array. I volunteer to write the fix, if I can extract some hints from more knowledgeable folk. There's sizeOfByteArray#, is there an analog for an Array#? I need to know how to find the length of Hugs array primitives too. Cheers, Spencer Janssen

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Command line utility that shrinks/simplifies functions applications ?
by Jason Dagit 02 Dec '06

02 Dec '06

On 11/30/06, Pepe Iborra <mnislaih(a)gmail.com> wrote: > > > On 30/11/2006, at 17:04, Spencer Janssen wrote: > > > I believe you're talking about the `pl' plugin for lambdabot. Lambdabot has > an offline mode, visit the homepage for the source: > > http://www.cse.unsw.edu.au/~dons/lambdabot.html > > > > > There is also a web interface to lambdabot, but I can't seem to find the > link. > http://lambdabot.codersbase.com/ > > It's really nice, I use it all the time. Thanks, we had fun putting lambdabot on the web (I have some other plans for it now too, but no time!). It had been a long time since I updated that instance of lambdabot but your email prompted me to do that today. The instance at that url now supports, redo, undo and unpl and has been synched with the official version of lambdabot 4p284. Thanks, Jason

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why are implicit types different? (cleanup)
by S. Alexander Jacobson 01 Dec '06

01 Dec '06

Why do g and g' have different types? g x y = let ?f = \x-> x in ?f x ++ (show (?f y)) g :: [Char] -> [Char] -> [Char] g' :: (Show t) => [Char] -> t -> [Char] g' x y = let f = \x-> x in f x ++ (show (f y)) Is there a way I can use implicit types and let g be as general as g'? -Alex- ______________________________________________________________ S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

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First Call for Papers: TFP 2007, New York
by TFP 2007 01 Dec '06

01 Dec '06

CALL FOR PAPERS Trends in Functional Programming 2007 New York, USA April 2-4, 2007 http://cs.shu.edu/tfp2007/ OR http://tltc.shu.edu/tfp2007/ The symposium on Trends in Functional Programming (TFP) is an international forum for researchers with interests in all aspects of functional programming languages, focusing on providing a broad view of current and future trends in Functional Programming. It aspires to be a lively environment for presenting the latest research results through acceptance by extended abstracts. A formal post-symposium refereeing process then selects the best articles presented at the symposium for publication in a high-profile volume. TFP 2007 is co-hosted by Seton Hall University and The City College of New York (CCNY) and will be held in New York, USA, April 2-4, 2007 at the CCNY campus. SCOPE OF THE SYMPOSIUM The symposium recognizes that new trends may arise through various routes. As part of the Symposium's focus on trends we therefore identify the following five article categories. High-quality articles are solicited in any of these categories: Research Articles leading-edge, previously unpublished research work Position Articles on what new trends should or should not be Project Articles descriptions of recently started new projects Evaluation Articles what lessons can be drawn from a finished project Overview Articles summarizing work with respect to a trendy subject Articles must be original and not submitted for simultaneous publication to any other forum. They may consider any aspect of functional programming: theoretical, implementation-oriented, or more experience-oriented. Applications of functional programming techniques to other languages are also within the scope of the symposium. Articles on the following subject areas are particularly welcomed: o Dependently Typed Functional Programming o Validation and Verification of Functional Programs o Debugging for Functional Languages o Functional Programming and Security o Functional Programming and Mobility o Functional Programming to Animate/Prototype/Implement Systems from Formal or Semi-Formal Specifications o Functional Languages for Telecommunications Applications o Functional Languages for Embedded Systems o Functional Programming Applied to Global Computing o Functional GRIDs o Functional Programming Ideas in Imperative or Object-Oriented Settings (and the converse) o Interoperability with Imperative Programming Languages o Novel Memory Management Techniques o Parallel/Concurrent Functional Languages o Program Transformation Techniques o Empirical Performance Studies o Abstract/Virtual Machines and Compilers for Functional Languages o New Implementation Strategies o any new emerging trend in the functional programming area If you are in doubt on whether your article is within the scope of TFP, please contact the TFP 2007 program chair, Marco T. Morazan, at tfp2007(a)shu.edu. SUBMISSION AND DRAFT PROCEEDINGS Acceptance of articles for presentation at the symposium is based on the review of extended abstracts (6 to 10 pages in length) by the program committee. Accepted abstracts are to be completed to full papers before the symposium for publication in the draft proceedings and on-line. Further details can be found at the TFP 2007 website. POST-SYMPOSIUM REFEREEING AND PUBLICATION In addition to the draft symposium proceedings, we intend to continue the TFP tradition of publishing a high-quality subset of contributions in the Intellect series on Trends in Functional Programming. IMPORTANT DATES Abstract Submission: February 1, 2007 Notification of Acceptance: February 20, 2007 Registration Deadline: March 2, 2007 Camera Ready Full Paper Due: March 9, 2007 TFP Symposium: April 2-4, 2007 PROGRAMME COMMITTEE John Clements California Polytechnic State University, USA Marko van Eekelen Radboud Universiteit Nijmegen, The Netherlands Benjamin Goldberg New York University, USA Kevin Hammond University of St. Andrews, UK Patricia Johann Rutgers University, USA Hans-Wolfgang Loidl Ludwig-Maximilians Universität München, Germany Rita Loogen Philipps-Universität Marburg, Germany Greg Michaelson Heriot-Watt University, UK Marco T. Morazán (Chair) Seton Hall University, USA Henrik Nilsson University of Nottingham, UK Chris Okasaki United States Military Academy at West Point, USA Rex Page University of Oklahoma, USA Ricardo Pena Universidad Complutense de Madrid, Spain Benjamin C. Pierce University of Pennsylvania, USA John Reppy University of Chicago, USA Ulrik P. Schultz University of Southern Denmark, Denmark Clara Segura Universidad Complutense de Madrid, Spain Jocelyn Sérot Université Blaise Pascal, France Zhong Shao Yale University, USA Olin Shivers Georgia Institute of Technology, USA Phil Trinder Heriot-Watt University, UK David Walker Princeton University, USA ORGANIZATION Symposium Chair: Henrik Nilsson, University of Nottingham, UK Programme Chair: Marco T. Morazan, Seton Hall University, USA Treasurer: Greg Michaelson, Heriot-Watt University, UK Local Arrangements: Marco T. Morazan, Seton Hall University, USA ************************************************************************************ Dr. Marco T. Morazan TFP 2007 Program Committee Chair http://tltc.shu.edu/tfp2007/ http://cs.shu.edu/tfp2007/

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