Re: [Haskell-cafe] Beginner: IORef constructor?
Thanks. I've been reading the docs and examples on State (in Control.Monad.State), but I can't understand it at all. ticks and plusOnes... All they seem to do is return their argument plus 1... On 12/1/06, Bernie Pope [EMAIL PROTECTED] wrote: On 01/12/2006, at 6:08 PM, TJ wrote: First of all, sorry if this is a really silly question, but I couldn't figure it out from experimenting in GHCi and from the GHC libraries documentation (or Google). Is there an IORef consturctor? Or is it just internal to the Data.IORef module? I want a global variable, so I did the following: -- module VirtualWorld where import Data.IORef theWorld = IORef [] -- This will be writeIORef'ed with a populated list as the user modifies the world. - It doesn't work. GHCi says that the IORef constructor is not in scope. I did a :module Data.IORef and then IORef [] and it still gives me the same error. I'm using GHC 6.6 on Windows. Hi TJ, IORef is an abstract data type, so you cannot refer to its constructors directly. Instead you must use: newIORef :: a - IO (IORef a) which will create an IORef on your behalf. Note that the result is in the IO type, which limits what you can do with it. If you want a global variable then you can use something like: import System.IO.Unsafe (unsafePerformIO) global = unsafePerformIO (newIORef []) But this is often regarded as bad programming style (depends who you talk to). So you should probably avoid this unless it is really necessary (perhaps you could use a state monad instead?) Read the comments about unsafePerformIO on this page: http://www.haskell.org/ghc/docs/latest/html/libraries/base/System- IO-Unsafe.html especially the notes about NOINLINE and -fno-cse Cheers, Bernie. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Beginner: IORef constructor?
tjay.dreaming:
Thanks. I've been reading the docs and examples on State (in
Control.Monad.State), but I can't understand it at all. ticks and
plusOnes... All they seem to do is return their argument plus 1...
Here's a little demo. (I agree, the State docs could have nicer demos)
Play around with the code, read the haddocks, and it should make sense
eventually :)_
-- Don
import Control.Monad.State
--
-- the type for a 'global' 'variable'
--
data T = T { ref :: Int }
-- Run code with a single global 'ref', initialised to 0
main = evalStateT g $ T { ref = 0 }
-- set it to 10
g = do
printio g
putRef 10
printio modified state
f
-- read that ref, print it
f = do
r - getRef
printio r
return ()
getRef = gets ref
putRef x = modify $ \_ - T { ref = x }
printio :: Show a = a - StateT T IO ()
printio = liftIO . print
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RE: [Haskell-cafe] ANNOUNCE: Visual Haskell prerelease0.2
From: Krasimir Angelov [mailto:[EMAIL PROTECTED] Visual Haskell is packaged with just the core libraries. Control.Monad.* modules are part of mtl and Test.HUnit is part of HUnit which aren't core libraries and aren't installed. It was long time ago when I was using the official Windows installer for last time. Is it still packaged with all libraries? Krasimir It certainly is. Is it possible to configure VisualHaskell so that it uses the existing ghc-6.6 installation, rather than it's own? Or is there some way I can copy over the HS*.o, libHS*.a, and libHS*_p.a files and register them? Comparing the installations indicates that ghc-6.6 has the following packages, which Visual Haskell lacks (I'm just comparing the HS*.o files in c:\ghc\ghc-6.6 and C:\Program Files\Visual Haskell): cgi fgl GLUT (and GLUT_cbits) haskell-src html HUnit mtl network objectio OpenGL (and OpenGL_cbits) QuickCheck readline time xhtml Alistair * Confidentiality Note: The information contained in this message, and any attachments, may contain confidential and/or privileged material. It is intended solely for the person(s) or entity to which it is addressed. Any review, retransmission, dissemination, or taking of any action in reliance upon this information by persons or entities other than the intended recipient(s) is prohibited. If you received this in error, please contact the sender and delete the material from any computer. * ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
Hi Krasimir, On Fri, 01 Dec 2006 16:56:02 +0900, Krasimir Angelov [EMAIL PROTECTED] wrote: http://www.cygwin.com/ml/cygwin/1998-04/msg00133.html I wonder whether this may cause the problem. I have uploaded a new vs_haskell.dll here: http://www.haskell.org/visualhaskell/vs_haskell.zip It is the same dll but without stripped debug symbols. Could you try to replace it in your installation? I tried to replace vs_haskell.dll after Windows Installer (MSI), no error occur during devenv.exe /Setup command or using Visual Haskell. I can make new Haskell project. On Fri, 01 Dec 2006 03:48:49 +0900, Justin Bailey [EMAIL PROTECTED] wrote: I am having similar problems with the Visual Haskell install, and the commands given did not help. When I open Visual Studios Help | About dialog, I get an error about the package failing to initialize. I am installing to an English copy, however. And I can open Studios Help | About dialog without any error. After exit Visual Haskell, Microsoft Development Environment opened error dialog about devenv.dll sometimes. Anyway, this error is harmless and I reported to Microsoft by form. Best Regards, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: Visual Haskell prerelease0.2
Hi Alistair, On Fri, 01 Dec 2006 18:13:45 +0900, Bayley, Alistair [EMAIL PROTECTED] wrote: It certainly is. Is it possible to configure VisualHaskell so that it uses the existing ghc-6.6 installation, rather than it's own? I think you can install extra libraries by cabal (and sometime you also need MSYS and MSYS Developer Tool Kit (autotools) for configuration). cgi fgl GLUT (and GLUT_cbits) haskell-src html HUnit mtl network objectio OpenGL (and OpenGL_cbits) QuickCheck readline time xhtml And I proposed to bundle OpenAL and ALUT packages. http://www.haskell.org/pipermail/glasgow-haskell-users/2006-October/011283.html These packages are in extra libraries. And I think that - OpenAL library is LGPL and OpenAL package is BSD3, so there is no reason avoiding to include this package. OpenAL site notices that OpenAL can become Creative's licese when using on Creative Device. http://www.openal.org/platforms.html But if you look at Creative's OpenAL SDK header files, you can find al.h and eft.h are LGPL. So I think we can use OpenAL library under LGPL on Windows, if we don't use Creative specific extentions. http://opensource.creative.com/pipermail/openal/2004-March/007309.html Best Reagrds, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
Thanks. In the mail that I mentioned there was a sugesstion to use -s option during dll linking. This has the advantage that the produced dll will be smaller but still correct. I will try to build a new dll again with this option this time. If it works I will prepare a new installer with the updated dll. Cheers, Krasimir On 12/1/06, shelarcy [EMAIL PROTECTED] wrote: Hi Krasimir, On Fri, 01 Dec 2006 16:56:02 +0900, Krasimir Angelov [EMAIL PROTECTED] wrote: http://www.cygwin.com/ml/cygwin/1998-04/msg00133.html I wonder whether this may cause the problem. I have uploaded a new vs_haskell.dll here: http://www.haskell.org/visualhaskell/vs_haskell.zip It is the same dll but without stripped debug symbols. Could you try to replace it in your installation? I tried to replace vs_haskell.dll after Windows Installer (MSI), no error occur during devenv.exe /Setup command or using Visual Haskell. I can make new Haskell project. On Fri, 01 Dec 2006 03:48:49 +0900, Justin Bailey [EMAIL PROTECTED] wrote: I am having similar problems with the Visual Haskell install, and the commands given did not help. When I open Visual Studios Help | About dialog, I get an error about the package failing to initialize. I am installing to an English copy, however. And I can open Studios Help | About dialog without any error. After exit Visual Haskell, Microsoft Development Environment opened error dialog about devenv.dll sometimes. Anyway, this error is harmless and I reported to Microsoft by form. Best Regards, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANNOUNCE: Visual Haskell prerelease0.2
I will build these libraries for the final installer. On 12/1/06, shelarcy [EMAIL PROTECTED] wrote: Hi Alistair, On Fri, 01 Dec 2006 18:13:45 +0900, Bayley, Alistair [EMAIL PROTECTED] wrote: It certainly is. Is it possible to configure VisualHaskell so that it uses the existing ghc-6.6 installation, rather than it's own? I think you can install extra libraries by cabal (and sometime you also need MSYS and MSYS Developer Tool Kit (autotools) for configuration). cgi fgl GLUT (and GLUT_cbits) haskell-src html HUnit mtl network objectio OpenGL (and OpenGL_cbits) QuickCheck readline time xhtml And I proposed to bundle OpenAL and ALUT packages. http://www.haskell.org/pipermail/glasgow-haskell-users/2006-October/011283.html These packages are in extra libraries. And I think that - OpenAL library is LGPL and OpenAL package is BSD3, so there is no reason avoiding to include this package. OpenAL site notices that OpenAL can become Creative's licese when using on Creative Device. http://www.openal.org/platforms.html But if you look at Creative's OpenAL SDK header files, you can find al.h and eft.h are LGPL. So I think we can use OpenAL library under LGPL on Windows, if we don't use Creative specific extentions. http://opensource.creative.com/pipermail/openal/2004-March/007309.html Best Reagrds, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Beginner: IORef constructor?
Thanks for the demo. I don't actually understand what's going on yet,
but your code doesn't really use a global variable, does it? From
what I can understand, the main function is passing the State to the
other functions.
I think I was careless about mixing IO functions and normal
functions. Now that I think about it, my global variable really
should only be available to IO functions, so the following should be
just fine:
--
module Global where
import Data.IORef
theGlobalVariable = newIORef []
testIt = do ref - theGlobalVariable
original - readIORef ref
print original
writeIORef ref [1,2,3]
new - readIORef ref
print new
--
I've got a lot to learn about Haskell...
On 12/1/06, Donald Bruce Stewart [EMAIL PROTECTED] wrote:
tjay.dreaming:
Thanks. I've been reading the docs and examples on State (in
Control.Monad.State), but I can't understand it at all. ticks and
plusOnes... All they seem to do is return their argument plus 1...
Here's a little demo. (I agree, the State docs could have nicer demos)
Play around with the code, read the haddocks, and it should make sense
eventually :)_
-- Don
import Control.Monad.State
--
-- the type for a 'global' 'variable'
--
data T = T { ref :: Int }
-- Run code with a single global 'ref', initialised to 0
main = evalStateT g $ T { ref = 0 }
-- set it to 10
g = do
printio g
putRef 10
printio modified state
f
-- read that ref, print it
f = do
r - getRef
printio r
return ()
getRef = gets ref
putRef x = modify $ \_ - T { ref = x }
printio :: Show a = a - StateT T IO ()
printio = liftIO . print
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Re: [Haskell-cafe] Beginner: IORef constructor?
tjay.dreaming: Thanks for the demo. I don't actually understand what's going on yet, but your code doesn't really use a global variable, does it? From what I can understand, the main function is passing the State to the other functions. Right, via the monad. The monad does all the threading. I think I was careless about mixing IO functions and normal functions. Now that I think about it, my global variable really should only be available to IO functions, so the following should be just fine: -- module Global where import Data.IORef theGlobalVariable = newIORef [] testIt = do ref - theGlobalVariable original - readIORef ref print original writeIORef ref [1,2,3] new - readIORef ref print new -- I've got a lot to learn about Haskell... Now, if you wanted to pass that ref to other functions, you'd have to thread it explicitly -- unless you store it in a state monad :) i.e. do ref - theGlobalVariable ... .. f ref ... f r = do ... .. g r ... I kind of jumped ahead that step, and went straight to the implicitly threaded version. -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re[2]: [Haskell-cafe] How to get subset of a list?
Hello Huazhi, Friday, December 1, 2006, 5:04:10 AM, you wrote: However, like I want to choose s[1,3,6,10] or something like this. Are there some straightforward function or operator for doing this job? The !! operator in haskell seems does not support multiple indecies. just change your mind, Neo ;) Hugs map (abcdefg !!) [1,3,6] bdg :: [Char] -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Beginner: IORef constructor?
tjay.dreaming: Donald: Now, if you wanted to pass that ref to other functions, you'd have to thread it explicitly -- unless you store it in a state monad :) i.e. do ref - theGlobalVariable ... .. f ref ... f r = do ... .. g r ... I kind of jumped ahead that step, and went straight to the implicitly threaded version. -- Don Tested my code again and it doesn't work as expected. I don't understand what threading means, but is that the reason I can't have this: -- module StateTest where import Data.IORef theGlobalVariable = newIORef [] modify1 = do ref - theGlobalVariable original - readIORef ref print original writeIORef ref $ original ++ [1] new - readIORef ref print new modify2 = do ref - theGlobalVariable original - readIORef ref print original writeIORef ref $ original ++ [2] new - readIORef ref print new doIt = do modify1 modify2 This doesn't mean what you think it means :) In particular, theGlobalVariable isn't a global variable, its a function that creates a new IORef, initialised to []. So you create two new iorefs, once in modify1, and again in modify2. For this kind of problem, I'd use a State transformer monad, layered over IO, as follows: import Control.Monad.State main = evalStateT doIt [] doIt = do modify1 modify2 modify1 = do orig - get printio orig put (1 : orig) new - get printio new modify2 = do orig - get printio orig put (2 : orig) new - get printio new printio :: Show a = a - StateT a IO () printio = liftIO . print Running this: $ runhaskell A.hs [] [1] [1] [2,1] Note that there's no need for any mutable variables here. If this isn't suitable, perhaps you could elaborate a bit on what effect you're trying to achieve? -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Draft MissingH Reorg Plan
John Goerzen [EMAIL PROTECTED] wrote: Please tell me if I should just go away or go to another list here. How about [EMAIL PROTECTED] http://software.complete.org/missingh/wiki/TransitionPlanning Your comments (and edits! -- must register/login first) are welcome. About Text.ParserCombinators.Parsec.RFC2234 and the like. Although I can't see what this code does (no links on the wiki, and port 70 is firewalled here), I would be prepared to bet that you do not in fact define any new combinators for parsing. What you have there is a parser for a specific little language. Even if it is implemented using parsec combinators, it does not belong with them. Alternative suggestions: Language.RFC2234.Parse Language.ABNF.RFC2234.Parse Network.SMTP.RFC2821.Parse Network.Email.RFC2822.Parse Regards, Malcolm ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Beginner: IORef constructor?
TJ wrote: -- module Global where import Data.IORef theGlobalVariable = newIORef [] testIt = do ref - theGlobalVariable original - readIORef ref print original writeIORef ref [1,2,3] new - readIORef ref print new -- Wrong. You get a fresh new variable everytime you access 'theGlobalVariable'. I've got a lot to learn about Haskell... Well, for starters: - there are no variables in ordinary Haskell, - there are variables in the ST and IO monads, but dragging IO everywhere is burdensome and you don't want to do that, - you can probably fake global variables using 'unsafePerformIO', and you definitely don't want to mess with that (yet), - you need to understand monads in general, the State monad, the ST monad and the IO monad, and in exactly this order. Whatever you're trying to do right now, just forget that there are variables in BASIC and do it without mutable state. -Udo -- They laughed at Einstein. They laughed at the Wright Brothers. But they also laughed at Bozo the Clown. -- attributed to Carl Sagan signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
On 11/30/06, Krasimir Angelov [EMAIL PROTECTED] wrote: I wonder whether this may cause the problem. I have uploaded a new vs_haskell.dll here: http://www.haskell.org/visualhaskell/vs_haskell.zip It is the same dll but without stripped debug symbols. Could you try to replace it in your installation? That new DLL worked for me, and I can also create new Haskell projects. Very cool - thanks! Justin ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Beginner: IORef constructor?
Donald: This doesn't mean what you think it means :) In particular, theGlobalVariable isn't a global variable, its a function that creates a new IORef, initialised to []. So you create two new iorefs, once in modify1, and again in modify2. Indeed, it's not what I thought it was at all! Bulat: you may be interested in looking at http://haskell.org/haskellwiki/IO_inside Thanks for the link. Udo: Whatever you're trying to do right now, just forget that there are variables in BASIC and do it without mutable state. Alrighty. But I'd like to set the record straight that it was C++ which screwed up my mind forever ;) Donald: Note that there's no need for any mutable variables here. If this isn't suitable, perhaps you could elaborate a bit on what effect you're trying to achieve? Yes I've come to the same conclusion. Thanks for the help, it really helps :) TJ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re[2]: How to get subset of a list?
Good. I personally perfer this solution... Bulat Ziganshin-2 wrote: Hello Huazhi, Friday, December 1, 2006, 5:04:10 AM, you wrote: However, like I want to choose s[1,3,6,10] or something like this. Are there some straightforward function or operator for doing this job? The !! operator in haskell seems does not support multiple indecies. just change your mind, Neo ;) Hugs map (abcdefg !!) [1,3,6] bdg :: [Char] -- Best regards, Bulatmailto:[EMAIL PROTECTED] ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- View this message in context: http://www.nabble.com/How-to-get-subset-of-a-list--tf2735647.html#a7637491 Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
The zip file is updated with .dll that is with stripped debug symbols but with --optdll-s as it is recommended. Could some one try whether it works? It is about two times smaller than the non stripped version. http://www.haskell.org/visualhaskell/vs_haskell.zip Cheers, Krasimir ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IFF reader and writer
Am Freitag, 1. Dezember 2006 16:30 schrieb Henning Thielemann: On AmigaOS there is a library called iffparse.library, which is used for processing the Interchange File Format, which is a binary container format developed by Electronic Arts for any kind of data. http://en.wikipedia.org/wiki/Interchange_File_Format The best known instances of this format are certainly the AIFF sampled sound format and WAV (which is RIFF, that is little endian IFF). Short question: Is there some Haskell library for parsing and constructing files of this format? I don't have any Haskell lib for (R)IFF, but as one of the freealut authors I have the pleasure to maintain a WAV reader, among other things. IMHO WAV is one of the most idiotic, redundant and underspecified format in the world, and most existing WAV files are broken in some respect. PNGs are a bit better, but all those chunked formats are a bit problematic in practice, because new chunk types are constantly being invented, contradict other chunks, etc. etc. Quite a few concrete (R)IFF instances can contain (R)IFF within chunks themselves, furthermore you have always be prepared to handle an unknown chunk type. So a general (R)IFF type can't be much more than a tree with a tagged bunch of bytes at each node, which is not really of much help IMHO. Separate libraries for handling WAV, TIFF, PNG, AVI, etc. might make more sense, as they can reflect the underlying structure much better. Cheers, S. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IFF reader and writer
On Fri, 1 Dec 2006, Sven Panne wrote: I don't have any Haskell lib for (R)IFF, but as one of the freealut authors I have the pleasure to maintain a WAV reader, among other things. IMHO WAV is one of the most idiotic, redundant and underspecified format in the world, and most existing WAV files are broken in some respect. PNGs are a bit better, but all those chunked formats are a bit problematic in practice, because new chunk types are constantly being invented, contradict other chunks, etc. etc. The idea is that unknown chunks can be ignored in most cases. Of course, this is not always possible, but there are several examples where it worked. Quite a few concrete (R)IFF instances can contain (R)IFF within chunks themselves, furthermore you have always be prepared to handle an unknown chunk type. So a general (R)IFF type can't be much more than a tree with a tagged bunch of bytes at each node, which is not really of much help IMHO. That's exactly what I ask for. Some of the features of the IFF like CAT and PROP chunks are rarely used, maybe because there were no libraries which support them. Separate libraries for handling WAV, TIFF, PNG, AVI, etc. might make more sense, as they can reflect the underlying structure much better. But they could all use a general IFF library. This way you can bundle different kinds of data in one file, say sounds and pictures for an animation. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] First Call for Papers: TFP 2007, New York
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 Articlesleading-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 [EMAIL PROTECTED] 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 MichaelsonHeriot-Watt University, UK Marco T. Morazán (Chair)Seton Hall University, USA Henrik NilssonUniversity of Nottingham, UK Chris OkasakiUnited 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 ReppyUniversity of Chicago, USA Ulrik P. Schultz
Re: [Haskell-cafe] Draft MissingH Reorg Plan
On Fri, Dec 01, 2006 at 01:56:34AM -0600, Taral wrote: On 12/1/06, Tomasz Zielonka [EMAIL PROTECTED] wrote: Do you accept contributions? I have some code I find very useful that Yes! would fit in the same places, like in Text.ParserCombinators.Parsec.Utils, Data.BitsUtils (btw, why not Data.Bits.Utils?), Control.Concurrent.*. Data.Bits.Utils would be fine too. I tried not to add a new level of hierarchy where none existed, but that may be more consistent. Hey, contributions. I'll throw in my haskell MIME parser if you want it. It's not the same as the one that most people use -- but I like it better. :) Hey Taral -- got a URL where I could take a look at it? MissingH currently has the one from WASH but if you've got a better one, I would certainly be interested. WASH brings a ton of weight along with it, and it would be nice to not have to carry that around. -- John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Draft MissingH Reorg Plan
On Fri, Dec 01, 2006 at 07:04:56AM +0100, Tomasz Zielonka wrote: http://software.complete.org/missingh/wiki/TransitionPlanning Your comments (and edits! -- must register/login first) are welcome. As for other code (say Data.Tree.Utils), I am not sure what's best: put it in some big library like yours, or publish as separate small libraries. There is more work with the latter, but it seems more clean, and easy to review for the user. Well, MissingH is going the direction of splitting up into smaller pieces, based on feedback received here, so I'd probably suggest that you keep that separate. Unless it's just one small/simple module. -- John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Re: Draft MissingH Reorg Plan
Malcolm Wallace wrote: John Goerzen [EMAIL PROTECTED] wrote: Please tell me if I should just go away or go to another list here. How about [EMAIL PROTECTED] Fair enough. Will do. http://software.complete.org/missingh/wiki/TransitionPlanning Your comments (and edits! -- must register/login first) are welcome. About Text.ParserCombinators.Parsec.RFC2234 and the like. Although I can't see what this code does (no links on the wiki, and port 70 is firewalled here), I would be prepared to bet that you do not in fact define any new combinators for parsing. What you have there is a parser Here's a snippet: This module provides parsers for the grammar defined in RFC2234, Augmented BNF for Syntax Specifications: ABNF, http://www.faqs.org/rfcs/rfc2234.html. The terminal called char in the RFC is called character here to avoid conflicts with Parsec's char function. alpha :: CharParser st Char bit :: CharParser st Char character :: CharParser st Char cr :: CharParser st Char This one is not email-specific. The other two are. (BTW, they were written by Peter Simons) for a specific little language. Even if it is implemented using parsec combinators, it does not belong with them. Alternative suggestions: Language.RFC2234.Parse Language.ABNF.RFC2234.Parse Network.SMTP.RFC2821.Parse Network.Email.RFC2822.Parse Does the above suggest a single good place for them to you? -- John ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Functional GUI combinators for arbitrary graphs of components?
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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] IFF reader and writer
This parser was quick to write and works on AIFF files. It does not do much
validation, and bits from 2 to 4 GB in length will cause errors.
module LoadIFF(IFF(..),parseIFF,IDType,FormType,ContentsType) where
import Data.List(unfoldr,span)
import Data.Bits((.|.),shiftL)
import Data.Word(Word32)
import Data.ByteString(ByteString)
import qualified Data.ByteString as B(take,drop,splitAt,length,unpack)
type IDType = String
type FormType = String
type ContentsType = String
data IFF = IFF_Form {len :: Word32
,typeID :: FormType
,parts :: [IFF]
}
| IFF_List {len :: Word32
,typeID :: ContentsType
,props :: [IFF]
,parts :: [IFF]
}
| IFF_Cat {len :: Word32
,typeID :: ContentsType
,parts :: [IFF]
}
| IFF_Prop {len :: Word32
,typeID :: FormType
,parts :: [IFF]
}
| IFF_Chunk {len :: Word32
,typeID :: IDType
,rawContent :: ByteString
}
instance Show IFF where
show IFF_Form { typeID = name, len = size, parts = p } =
IFF_Form {typeID=++show name++,size=++show size++,parts=++show p++}
show IFF_List { typeID = name, len = size, props = ps, parts = p } =
IFF_List {typeID=++show name++,size=++show size++,props++show
ps++,parts=++show p++}
show IFF_Cat { typeID = name, len = size, parts = p } =
IFF_Cat {typeID=++show name++,size=++show size++,parts=++show p++}
show IFF_Prop { typeID = name, len = size, parts = p } =
IFF_Prop {typeID=++show name++,size=++show size++,parts=++show p++}
show IFF_Chunk { typeID = name, len = size } = IFF_Chunk {typeID=++show
name++,size=++show size++}
b2s = map (toEnum . fromEnum) . B.unpack
isProp IFF_Prop {} = True
isProp _ = False
parseIFF :: ByteString - Maybe (IFF,ByteString)
parseIFF b | B.length b =8 = Nothing
| otherwise =
let (bID,b') = B.splitAt 4 b
(bLEN,b'') = B.splitAt 4 b'
(bTypeID,content) = B.splitAt 4 b''
[x1,x2,x3,x4] = map fromIntegral (B.unpack bLEN)
iLEN = (shiftL x1 24) .|. (shiftL x2 16) .|. (shiftL x3 8) .|. x4
toNext = (if odd iLEN then succ else id) (fromIntegral iLEN)
rest = B.drop toNext b''
in if iLEN fromIntegral (B.length b'')
then Nothing
else let iff = case b2s bID of
FORM - IFF_Form {len = iLEN
,typeID = b2s bTypeID
,parts = unfoldr parseIFF content}
LIST - let (ps,cs) = span isProp (unfoldr parseIFF
content)
in IFF_List {len = iLEN
,typeID = b2s bTypeID
,props = ps
,parts = cs}
CAT - IFF_Cat {len = iLEN
,typeID = b2s bTypeID
,parts = unfoldr parseIFF content}
Prop - IFF_Prop {len = iLEN
,typeID = b2s bTypeID
,parts = unfoldr parseIFF content}
chunkID - IFF_Chunk {len = iLEN
,typeID = chunkID
,rawContent = content}
in Just (iff,rest)
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Re: [Haskell-cafe] Functional GUI combinators for arbitrary graphs ofcomponents?
Brian Hulley wrote: 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] The above is more complicated than necessary. The problem can be captured by: type GraphDesc a = [(a,a)] Brian. -- http://www.metamilk.com ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] why are implicit types different? (cleanup)
On Tue, Nov 28, 2006 at 11:59:01AM -0500, S. Alexander Jacobson wrote: I ended up solving it by using a typeclass. My general experience of implicit types has been that they end up being a lot less useful than they appear. Getting the types right ends up being difficult and it is usually better just to be in a monad or as in this case to use typeclasses. I've begun to think of use of implicit types as a sign a bad smell in the code and if I have used one somewhere, I try to eliminate it because doing so usually results in better code overall. yes. they are just a bad idea for many reasons IMHO. I think they should be purposefully and forcefully retired so they don't trip up new users to haskell who think they are the right way to do things. John -- John Meacham - ⑆repetae.net⑆john⑈ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
Hi Krasimir, On Sat, 02 Dec 2006 02:14:26 +0900, Krasimir Angelov [EMAIL PROTECTED] wrote: The zip file is updated with .dll that is with stripped debug symbols but with --optdll-s as it is recommended. Could some one try whether it works? It is about two times smaller than the non stripped version. http://www.haskell.org/visualhaskell/vs_haskell.zip Is this file updated one? I downloaded it from above url again. But file size is same. So, I checked hash. It noticed that current and previous files are same. $ md5sum vs_haskell.dll \a968ac130932a9b38bd0da50e9ae865a *C:\\Documents and Settings\\ Administrator\\My Documents\\vs_haskell\\vs_haskell.dll $ md5sum C:\Doc\Haskell\vs_haskell\vs_haskell.dll \a968ac130932a9b38bd0da50e9ae865a *C:\\Doc\\Haskell\\vs_haskell\\ vs_haskell.dll Best Regards, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Parsec: Where's +++?
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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec: Where's +++?
garious: Koen Claessen's Parallel Parsing Processes, suggests their parsing combinators have been integrated into Parsec. If so, where is the +++ operator hiding? Hoogle says: Control.Arrow.(+++) :: ArrowChoice a = a b c - a b' c' - a (Either b b') (Either c c') Text.Html.(+++) :: (HTML a, HTML b) = a - b - Html Text.ParserCombinators.ReadP.(+++) :: ReadP a - ReadP a - ReadP a Text.ParserCombinators.ReadPrec.(+++) :: ReadPrec a - ReadPrec a - ReadPrec a Also, how do I determine what instances a datatype supports? Is Parsec an instance of Applicative? Try :info on your type in ghci: Prelude Control.Applicative :info Applicative class (Functor f) = Applicative f where pure :: a - f a (*) :: f (a - b) - f a - f b -- Defined in Control.Applicative instance (Monad m) = Applicative (WrappedMonad m) -- Defined in Control.Applicative instance Applicative Maybe -- Defined in Control.Applicative instance Applicative [] -- Defined in Control.Applicative instance Applicative IO -- Defined in Control.Applicative instance Applicative ((-) a) -- Defined in Control.Applicative instance Applicative ZipList -- Defined in Control.Applicative -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Command line utility that shrinks/simplifies functions applications ?
On 11/30/06, Pepe Iborra [EMAIL PROTECTED] 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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Parsec: Where's +++?
Text.ParserCombinators.ReadP.(+++) :: ReadP a - ReadP a - ReadP a Wow, fast and complete, Thanks Don!:) Would it make sense to derive instances of Applicable and Alternative for ReadP? Something like this maybe: instance Applicative ReadP where pure = return (*) = ap instance Alternative ReadP where empty = pfail (|) = (++) Thanks, Greg ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] The Data.Array.* hierarchy is unsafe (or, Segfaulting for fun and profit)
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 ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: Re: [Haskell-cafe] Parsec: Where's +++?
A agreed upon technique for dealing with typeclass hierarchies has
been slow to arrive. For instance, all monads are functors, but
providing a monad instance for your type doesn't automatically make it
a functor as well.
All monads are also applicative functors, and Control.Applicative does
have a newtype to recognize them as such:
Prelude :m + Control.Applicative
Prelude Control.Applicative :i WrapMonad
newtype WrappedMonad m a = WrapMonad {unwrapMonad :: m a}
-- Defined in Control.Applicative
Prelude Control.Applicative :i Applicative
class (Functor f) = Applicative f where
pure :: a - f a
(*) :: f (a - b) - f a - f b
-- Defined in Control.Applicative
instance (Monad m) = Applicative (WrappedMonad m)
-- Defined in Control.Applicative
...
Just wrap up your monad in WrapMonad, treat it like an applicative
functor, and then unwrap it with unwrapMonad.
HTH,
Nick
On 12/1/06, Greg Fitzgerald [EMAIL PROTECTED] wrote:
Text.ParserCombinators.ReadP.(+++) :: ReadP a - ReadP a - ReadP a
Wow, fast and complete, Thanks Don!:)
Would it make sense to derive instances of Applicable and Alternative
for ReadP? Something like this maybe:
instance Applicative ReadP where
pure = return
(*) = ap
instance Alternative ReadP where
empty = pfail
(|) = (++)
Thanks,
Greg
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Re: [Haskell-cafe] IFF reader and writer
On Fri, 1 Dec 2006, Chris Kuklewicz wrote: This parser was quick to write and works on AIFF files. It does not do much validation, and bits from 2 to 4 GB in length will cause errors. Nice. But it doesn't handle the semantics of PROP, does it? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Re: [Haskell] ANNOUNCE: Visual Haskell prerelease 0.2
Sorry. I was sleeping and I uploaded it to darcs.haskell.org instead to haskell.org. Try it now. Cheers, Krasimir On 12/2/06, shelarcy [EMAIL PROTECTED] wrote: Hi Krasimir, On Sat, 02 Dec 2006 02:14:26 +0900, Krasimir Angelov [EMAIL PROTECTED] wrote: The zip file is updated with .dll that is with stripped debug symbols but with --optdll-s as it is recommended. Could some one try whether it works? It is about two times smaller than the non stripped version. http://www.haskell.org/visualhaskell/vs_haskell.zip Is this file updated one? I downloaded it from above url again. But file size is same. So, I checked hash. It noticed that current and previous files are same. $ md5sum vs_haskell.dll \a968ac130932a9b38bd0da50e9ae865a *C:\\Documents and Settings\\ Administrator\\My Documents\\vs_haskell\\vs_haskell.dll $ md5sum C:\Doc\Haskell\vs_haskell\vs_haskell.dll \a968ac130932a9b38bd0da50e9ae865a *C:\\Doc\\Haskell\\vs_haskell\\ vs_haskell.dll Best Regards, -- shelarcy shelarcycapella.freemail.ne.jp http://page.freett.com/shelarcy/ ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Generate 50 random coordinates
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. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generate 50 random coordinates
On 12/2/06, Huazhi (Hank) Gong [EMAIL PROTECTED] wrote: myrand :: Int myrand = randomRIO(1::Int, 100) rf=[(myrand, myrand) | a - [1..50]] do let myrand = randomRIO (1 :: Int, 100) rf - replicateM 50 (liftM2 (,) myrand myrand) -- Taral [EMAIL PROTECTED] You can't prove anything. -- Gödel's Incompetence Theorem ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generate 50 random coordinates
hankgong: 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? Try initialising your random generator in 'main' , creating a list of infinite randoms, take the number you need, then feed that to the functions that need the list: import System.Random import Text.Printf import Data.Word main = do g - newStdGen -- intialise a random generator let (a,b) = split g -- create two separate generators as = randoms a -- one infinite list of randoms bs = randoms b -- another rs = zip as bs -- an infite list of pairs dump (take 50 rs) -- take 50, and consume them dump :: [(Int,Int)] - IO () dump s = mapM_ (uncurry (printf (%d,%d)\n)) s And running this: $ runhaskell A.hs (639240856,75173658) (-979753698,2004752008) (1514872498,-686799980) (1122012756,-645055058) ... -- Don ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Functional GUI combinators for arbitrary graphs of components?
On 12/1/06, Brian Hulley [EMAIL PROTECTED] wrote: 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. I suggest you check the Functional Graph Library (FGL). It's shipped as part of GHC. -- Taral [EMAIL PROTECTED] You can't prove anything. -- Gödel's Incompetence Theorem ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell source transformer?
On 11/30/06, Dimitry Golubovsky [EMAIL PROTECTED] wrote: 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. There's haskell-src and haskell-src-exts ( http://www.cs.chalmers.se/~d00nibro/haskell-src-exts/ ). -- Cheers, Lemmih ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Generate 50 random coordinates
Hello, On 12/1/06, Huazhi (Hank) Gong [EMAIL PROTECTED] wrote: Hello,all My intention is to generate 50 random coordinates like (x,y). myrand :: Int myrand = randomRIO(1::Int, 100) When we look at the type of randomRIO we see: randomRIO :: forall a. (Random a) = (a, a) - IO a You're giving it a tuple of Int, so we can substitute Int for 'a' in that type signature: myrand :: IO Int rf=[(myrand, myrand) | a - [1..50]] Here you are creating a list of tuples. We see from above that the type of the tuples would be (IO Int, IO Int), so rf :: [(IO Int, IO Int)]. This is because we have not run the IO action to generate the Int yet. 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? Your type signature tries to make a claim that myrand has type Int, but the compiler will disagree because of that pesky IO type. Yet Another Haskell Tutorial[1] seems to have a section on the pesky IO type. [1] http://www.cs.utah.edu/~hal/docs/daume02yaht.pdf I hope that helps, Jason ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
