Re: [Haskell-cafe] Conduit Error Output: Control.Monad.Trans.Resource.stateCleanup
Hi Lyndon, Outputting nothing *is* the desired result. When you run something like: bar - runResourceT $ lazyConsume $ sourceFile foo.txt print bar The steps that occur are roughly[1]: * ResourceT is initialized * File handle is opened, release action is registered to close the file handle * unsafeInterleaveIO is called, which creates a thunk that will pull from the Handle * runResourceT is called, which calls all release actions, including closing the file handle * The thunk is evaluated. It checks if the ResourceT is open. Since it isn't, it returns a []. The problem previously is that the last step was not checking if the ResourceT was still open, which could result in pulling from a closed handle. Michael On Tue, Feb 21, 2012 at 9:57 AM, Lyndon Maydwell maydw...@gmail.com wrote: Hi Michael, The behaviour of my original code has now changed to output nothing with no errors. I'm not sure of the significance of this as my code was incorrect, however, using the code you demonstrated gives the desired results. Thanks for the blindingly quick response! On Tue, Feb 21, 2012 at 3:30 PM, Michael Snoyman mich...@snoyman.com wrote: On Tue, Feb 21, 2012 at 7:40 AM, Michael Snoyman mich...@snoyman.com wrote: On Tue, Feb 21, 2012 at 5:46 AM, Lyndon Maydwell maydw...@gmail.com wrote: Hi Michael, Café. I'm writing some code using the conduit library and am encountering the following error output (while the program appears to function correctly) when using Data.Conduit.Lazy. The error given is: profile_simple_test_data: Control.Monad.Trans.Resource.stateCleanup: There is a bug in the implementation. The mutable state is being accessed after cleanup. Please contact the maintainers. A reduced code snippet that generates this error is (also attached): import Control.Monad import System.Environment import Control.Monad.IO.Class (liftIO) import System.IO import Data.Conduit.Lazy import Data.List (sort) import Data.Conduit import Prelude hiding (map) main = getArgs = process process args = mapM_ sorted args sorted x = runResourceT (lazyConsume $ sourceFeed x) = (mapM_ print . id) sourceFeed :: ResourceIO m = FilePath - Source m String sourceFeed file = sourceIO (openFile file ReadMode) hClose (\h - liftIO $ do eof - hIsEOF h if eof then return IOClosed else fmap IOOpen $ hGetLine h) when run over any text file. I may be doing something inconsistent with the correct use of sourceIO or lazyConsume, however, I tried to follow the example at http://www.yesodweb.com/home/snoyberg/blogs/conduit/conduit/source/source.ditamap?nav=nav-2 as closely as possible. Is this a bug, or simply an incorrect use of Conduit? I haven't fully debugged this yet. There's certainly a bug in the implementation of ResourceT, but the sample program is also wrong. You can't pass the result from a call to lazyConsume outside the scope of its ResourceT; the correct way to write sorted would be: sorted x = runResourceT $ lazyConsume (sourceFeed x) = mapM_ (liftIO . print) My guess is that this is a fallout from the transition away from mutable variables: lazyConsume no longer has any way of knowing that its ResourceT has already been terminated. Perhaps a simple solution would be to expose a primitive that checks if the ResourceT block has already been finalized. Michael I've added a test case for this bug, and fixed it. The commit is: https://github.com/snoyberg/conduit/commit/87e890fe7ee58686d20cabba15dd37f18ba66620 The basic idea is to add an extra constructor to represent when the ResourceT has already been closed, and expose a function resourceActive to check the state. Can you check if this solves your problem? Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Conduit Error Output: Control.Monad.Trans.Resource.stateCleanup
That makes a lot of sense. The diff was a bit beyond my skimming abilities :-) On Tue, Feb 21, 2012 at 4:15 PM, Michael Snoyman mich...@snoyman.com wrote: Hi Lyndon, Outputting nothing *is* the desired result. When you run something like: bar - runResourceT $ lazyConsume $ sourceFile foo.txt print bar The steps that occur are roughly[1]: * ResourceT is initialized * File handle is opened, release action is registered to close the file handle * unsafeInterleaveIO is called, which creates a thunk that will pull from the Handle * runResourceT is called, which calls all release actions, including closing the file handle * The thunk is evaluated. It checks if the ResourceT is open. Since it isn't, it returns a []. The problem previously is that the last step was not checking if the ResourceT was still open, which could result in pulling from a closed handle. Michael On Tue, Feb 21, 2012 at 9:57 AM, Lyndon Maydwell maydw...@gmail.com wrote: Hi Michael, The behaviour of my original code has now changed to output nothing with no errors. I'm not sure of the significance of this as my code was incorrect, however, using the code you demonstrated gives the desired results. Thanks for the blindingly quick response! On Tue, Feb 21, 2012 at 3:30 PM, Michael Snoyman mich...@snoyman.com wrote: On Tue, Feb 21, 2012 at 7:40 AM, Michael Snoyman mich...@snoyman.com wrote: On Tue, Feb 21, 2012 at 5:46 AM, Lyndon Maydwell maydw...@gmail.com wrote: Hi Michael, Café. I'm writing some code using the conduit library and am encountering the following error output (while the program appears to function correctly) when using Data.Conduit.Lazy. The error given is: profile_simple_test_data: Control.Monad.Trans.Resource.stateCleanup: There is a bug in the implementation. The mutable state is being accessed after cleanup. Please contact the maintainers. A reduced code snippet that generates this error is (also attached): import Control.Monad import System.Environment import Control.Monad.IO.Class (liftIO) import System.IO import Data.Conduit.Lazy import Data.List (sort) import Data.Conduit import Prelude hiding (map) main = getArgs = process process args = mapM_ sorted args sorted x = runResourceT (lazyConsume $ sourceFeed x) = (mapM_ print . id) sourceFeed :: ResourceIO m = FilePath - Source m String sourceFeed file = sourceIO (openFile file ReadMode) hClose (\h - liftIO $ do eof - hIsEOF h if eof then return IOClosed else fmap IOOpen $ hGetLine h) when run over any text file. I may be doing something inconsistent with the correct use of sourceIO or lazyConsume, however, I tried to follow the example at http://www.yesodweb.com/home/snoyberg/blogs/conduit/conduit/source/source.ditamap?nav=nav-2 as closely as possible. Is this a bug, or simply an incorrect use of Conduit? I haven't fully debugged this yet. There's certainly a bug in the implementation of ResourceT, but the sample program is also wrong. You can't pass the result from a call to lazyConsume outside the scope of its ResourceT; the correct way to write sorted would be: sorted x = runResourceT $ lazyConsume (sourceFeed x) = mapM_ (liftIO . print) My guess is that this is a fallout from the transition away from mutable variables: lazyConsume no longer has any way of knowing that its ResourceT has already been terminated. Perhaps a simple solution would be to expose a primitive that checks if the ResourceT block has already been finalized. Michael I've added a test case for this bug, and fixed it. The commit is: https://github.com/snoyberg/conduit/commit/87e890fe7ee58686d20cabba15dd37f18ba66620 The basic idea is to add an extra constructor to represent when the ResourceT has already been closed, and expose a function resourceActive to check the state. Can you check if this solves your problem? Michael ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
Austin Seipp: The only two things not clear at this point, at least to me, are: 1) Will Apple require the paid development program, as opposed to the free one, if you only want to self-sign applications with a cert they trust? You can self-sign applications with a certificate that you get with a free developer ID. Cf. http://daringfireball.net/2012/02/mountain_lion Apple is calling it “Gatekeeper”. It’s a system whereby developers can sign up for free-of-charge Apple developer IDs which they can then use to cryptographically sign their applications. If an app is found to be malware, Apple can revoke that developer’s certificate, rendering the app (along with any others from the same developer) inert on any Mac where it’s been installed. In effect, it offers all the security benefits of the App Store, except for the process of approving apps by Apple. 2) What will the default Gatekeeper setting in Mountain Lion be? The default is the middle option — i.e., AppStore and self-signed apps run. From the same source, The default for this setting is, I say, exactly right: the one in the middle, disallowing only unsigned apps. This default setting benefits users by increasing practical security, and also benefits developers, preserving the freedom to ship whatever software they want for the Mac, with no approval process. In an ideal world, you won't require the paid dev ID (I don't know the expense of giving out certs however,) and the default setting would be App store + Dev signed. It is an ideal world :) Manuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
Austin Seipp: On Sun, Feb 19, 2012 at 8:39 PM, Tom Murphy amin...@gmail.com wrote: On the other hand, it's impossible for a software company to maintain a sense of professionalism, when a user has to know a weird secret handshake to disable what they may perceive as equivalent to antivirus software. I'll also just add that if you're an actual software company, large or small, the $100 for the developer ID, certificate, ability to do iOS/App store apps, whatever, is a business expense, that is utterly dominated by a million other factors, as developing high quality applications isn't exactly cheap, and the price of a license is really the last thing you're going to worry about. If you're more worried about the potential to impact individual developers and small open source teams who want to get their work out there, you are right it's a concern. I think, Apple has made their stance quite clear by releasing the command line dev tools: http://kennethreitz.com/xcode-gcc-and-homebrew.html Manuel ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] (no subject)
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Re: [Haskell-cafe] ANNOUNCE: HaskellDB 2.0: Scrap your SQL strings
You mentioned that haskelldb was the first library where you weren't forced to break the abstraction. Do you have a solution to a situation where you might want to retreive the last inserted id after an insert? -- Mats Rauhala MasseR pgp8ofM61Yw5k.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] how to add monad-stack to network-conduit
Hello. I have got next problem: I want to have database connection pool in server based on network-conduit. So I wanted to be able to do runTCPServer options action where action src snk = pool - ask In this situation I can make pool `action's parameter, but in more difficult situations (many methods inside) is would be painfull. Also I wanted to have some kind of State for each thread, e.g. action src snk = src $= act1 $= act2 $= act3 $$ snk in act1, act2, act3 I want to read and change state. Is it possible? And how to do it if it is? -- Alexander Vershilov signature.asc Description: Digital signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] types and number of evaluation steps
My understanding was that the reason is that CSE can cause things to be shared that take up a lot of space when normally they would be garbage collected sooner. On Feb 18, 2012 11:57 AM, Roman Cheplyaka r...@ro-che.info wrote: It doesn't matter. Laziness would be affected if, for instance, something is not evaluated without CSE and is evaluated with it. In your example either all or none of 'a' and 'b' get evaluated, depending on whether the top-level expression is evaluated. * Victor Gorokgov m...@rkit.pp.ru [2012-02-18 18:23:19+0400] example = a + b + a + b exampleCSE = x + x where x = a + b With CSE we are introducing new thunk: x. 18.02.2012 17:38, Roman Cheplyaka пишет: * Holger Siegelholgersiege...@yahoo.de [2012-02-18 12:52:08+0100] You cannot. Common subexpression elimination is done by GHC very conservatively, because it can not only affect impure programs: it can also affects strictness/lazyness and worsen memory usage of pure code. Like the HaskellWiki says: If you care about CSE, do it by hand. How can it affect strictness or laziness? -- Roman I. Cheplyaka :: http://ro-che.info/ ___ 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] podcast?
On 09:05 Wed 15 Feb , serialhex wrote: Does anybody know of any good haskell/fp podcasts out there? i dont know if my googling skillz are just failing me, but i can't seem to find anything. thanks all! hex Out of my head I can think of ThinkRelevance podcast at http://thinkrelevance.com/blog/tags/podcast pgpSaQMQOTtoX.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] podcast?
I recently thought it would be Pretty Cool to make an FP podcast, sort of a spoken Haskell Weekly News but covering all FP, blogs, packages, conferences, papers, standards, mailing lists, even stackoverflow, whatever's interesting in FP. We could use Gtalk or Mumble (both quite high quality audio) to conduct it and cut it up in audacity. On 21 February 2012 15:00, Mats Rauhala mats.rauh...@gmail.com wrote: On 09:05 Wed 15 Feb , serialhex wrote: Does anybody know of any good haskell/fp podcasts out there? i dont know if my googling skillz are just failing me, but i can't seem to find anything. thanks all! hex Out of my head I can think of ThinkRelevance podcast at http://thinkrelevance.com/blog/tags/podcast ___ 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] podcast?
On 15:15 Tue 21 Feb , Christopher Done wrote: I recently thought it would be Pretty Cool to make an FP podcast, sort of a spoken Haskell Weekly News but covering all FP, blogs, packages, conferences, papers, standards, mailing lists, even stackoverflow, whatever's interesting in FP. We could use Gtalk or Mumble (both quite high quality audio) to conduct it and cut it up in audacity. I for one would be an interested listener -- Mats Rauhala MasseR pgpmnNX9qw0my.pgp Description: PGP signature ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad laws in presence of bottoms
On 2/21/12 2:17 AM, Roman Cheplyaka wrote: * Sebastian Fischerfisc...@nii.ac.jp [2012-02-21 00:28:13+0100] On Mon, Feb 20, 2012 at 7:42 PM, Roman Cheplyakar...@ro-che.info wrote: Is there any other interpretation in which the Reader monad obeys the laws? If selective strictness (the seq combinator) would exclude function types, the difference between undefined and \_ - undefined could not be observed. This reminds me of the different language levels used by the free theorem generator [1] and the discussions whether seq should have a type-class constraint.. It's not just about functions. The same holds for the lazy Writer monad, for instance. That's a similar sort of issue, just about whether undefined == (undefined,undefined) or not. If the equality holds then tuples would be domain products[1], but domain products do not form domains! In order to get a product which does form a domain, we'd need to use the smash product[2] instead. Unfortunately we can't have our cake and eat it too (unless we get rid of bottom entirely). Both this issue and the undefined == (\_ - undefined) issue come down to whether we're allowed to eta expand functions or tuples/records. While this is a well-studies topic, I don't know that anyone's come up with a really pretty answer to the dilemma. [1] Also a category-theoretic product. [2] Aka: data SmashProduct a b = SmashProduct !a !b -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Preventing leaked open file descriptors when catching exceptions
Hi all, I'm trying to run a loop that repeatedly attempts to open a file until it succeeds. The file is a named pipe in nonblocking mode, so the writer can only connect after the reader has connected. (Perhaps there is some way to determine this by stat'ing the pipe, but I don't know it yet.) Thus I do something like the following: tryUntilNoIOErr $ do performGC -- The reader must connect first, the writer here spins with backoff. PIO.openFd filename PIO.WriteOnly Nothing fileFlags I'm running GC between iterations to try to make sure I get rid of open files. Also, in the tryUntilNoIOErr code below I have some debugging messages which indicate that ioeGetHandle reports no handles associated with the exceptions I'm getting back. (If there were handles provided I could close them explicitly.) In spite of these attempted precautions I'm seeing too many open files exceptions in simple benchmarks that should only have a maximum of ONE file open. Any hints / pointers? Thanks, -Ryan mkBackoff :: IO (IO ()) mkBackoff = do tref - newIORef 1 return$ do t - readIORef tref writeIORef tref (min maxwait (2 * t)) threadDelay t where maxwait = 50 * 1000 tryUntilNoIOErr :: IO a - IO a tryUntilNoIOErr action = mkBackoff = loop where loop bkoff = handle (\ (e :: IOException) - do bkoff BSS.hPutStr stderr$ BSS.pack$ got IO err: ++ show e case ioeGetHandle e of Nothing - BSS.hPutStrLn stderr$ BSS.pack$ no hndl io err. Just x - BSS.hPutStrLn stderr$ BSS.pack$ HNDL on io err! ++ show x loop bkoff) $ action ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preventing leaked open file descriptors when catching exceptions
FYI, lsof confirms that there are indeed many many open connections to the same FIFO: Is there some other way to get at (and clean up) the file descriptor that is left by System.Posix.IO.openFD after it throws an exception? PingPipes 25115 rrnewton 124r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 125r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 126r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 127r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 128r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 129r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 130r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 131r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 132r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 133r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 134r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 135r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 136r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 137r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 PingPipes 25115 rrnewton 138r FIFO8,2 0t0 25166171 /tmp/pipe_9083984821255795683 On Tue, Feb 21, 2012 at 11:13 AM, Ryan Newton rrnew...@gmail.com wrote: Hi all, I'm trying to run a loop that repeatedly attempts to open a file until it succeeds. The file is a named pipe in nonblocking mode, so the writer can only connect after the reader has connected. (Perhaps there is some way to determine this by stat'ing the pipe, but I don't know it yet.) Thus I do something like the following: tryUntilNoIOErr $ do performGC -- The reader must connect first, the writer here spins with backoff. PIO.openFd filename PIO.WriteOnly Nothing fileFlags I'm running GC between iterations to try to make sure I get rid of open files. Also, in the tryUntilNoIOErr code below I have some debugging messages which indicate that ioeGetHandle reports no handles associated with the exceptions I'm getting back. (If there were handles provided I could close them explicitly.) In spite of these attempted precautions I'm seeing too many open files exceptions in simple benchmarks that should only have a maximum of ONE file open. Any hints / pointers? Thanks, -Ryan mkBackoff :: IO (IO ()) mkBackoff = do tref - newIORef 1 return$ do t - readIORef tref writeIORef tref (min maxwait (2 * t)) threadDelay t where maxwait = 50 * 1000 tryUntilNoIOErr :: IO a - IO a tryUntilNoIOErr action = mkBackoff = loop where loop bkoff = handle (\ (e :: IOException) - do bkoff BSS.hPutStr stderr$ BSS.pack$ got IO err: ++ show e case ioeGetHandle e of Nothing - BSS.hPutStrLn stderr$ BSS.pack$ no hndl io err. Just x - BSS.hPutStrLn stderr$ BSS.pack$ HNDL on io err! ++ show x loop bkoff) $ action ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad laws in presence of bottoms
Ehm... why exactly don't domain products form domains? On 21 Feb 2012, at 19:44, wren ng thornton wrote: On 2/21/12 2:17 AM, Roman Cheplyaka wrote: * Sebastian Fischerfisc...@nii.ac.jp [2012-02-21 00:28:13+0100] On Mon, Feb 20, 2012 at 7:42 PM, Roman Cheplyakar...@ro-che.info wrote: Is there any other interpretation in which the Reader monad obeys the laws? If selective strictness (the seq combinator) would exclude function types, the difference between undefined and \_ - undefined could not be observed. This reminds me of the different language levels used by the free theorem generator [1] and the discussions whether seq should have a type-class constraint.. It's not just about functions. The same holds for the lazy Writer monad, for instance. That's a similar sort of issue, just about whether undefined == (undefined,undefined) or not. If the equality holds then tuples would be domain products[1], but domain products do not form domains! In order to get a product which does form a domain, we'd need to use the smash product[2] instead. Unfortunately we can't have our cake and eat it too (unless we get rid of bottom entirely). Both this issue and the undefined == (\_ - undefined) issue come down to whether we're allowed to eta expand functions or tuples/records. While this is a well-studies topic, I don't know that anyone's come up with a really pretty answer to the dilemma. [1] Also a category-theoretic product. [2] Aka: data SmashProduct a b = SmashProduct !a !b -- Live well, ~wren ___ 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] Monad laws in presence of bottoms
On Tue, Feb 21, 2012 at 10:44 AM, wren ng thornton w...@freegeek.org wrote: That's a similar sort of issue, just about whether undefined == (undefined,undefined) or not. If the equality holds then tuples would be domain products[1], but domain products do not form domains! ... [1] Also a category-theoretic product. This doesn't make much sense to me, either. If it's a category theoretic product in a category of domains, then the product must be a domain, no? In order to get a product which does form a domain, we'd need to use the smash product[2] instead. Unfortunately we can't have our cake and eat it too (unless we get rid of bottom entirely). You don't have to get rid of bottom entirely (I think). If you make matches against products irrefutable, then you're again in the situation of seq being the only thing able to distinguish between _|_ and (_|_, _|_), so we could keep the current implementation (which is efficient) without it being possible to observe within the language. You just have to make seq not be magic on products. Miranda did this, except it still had a seq which exposed the lie. The problem with this is that you can easily build up a product that is a bunch of thunks and cause a stack overflow; I _think_ that's more of a concern than doing the same with a function. So in practice it might be harder to do without seq on tuples. -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preventing leaked open file descriptors when catching exceptions
On Tue, Feb 21, 2012 at 8:16 AM, Ryan Newton rrnew...@gmail.com wrote: FYI, lsof confirms that there are indeed many many open connections to the same FIFO: Like all of the lowest-level I/O functions, openFD just gives you back an integer, and the Fd type has no notion that there's an underlying system resource associated with it. It's your responsibility to manage it (i.e. clean up manually when catching an exception). ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preventing leaked open file descriptors whencatching exceptions
Quoth Bryan O'Sullivan b...@serpentine.com, On Tue, Feb 21, 2012 at 8:16 AM, Ryan Newton rrnew...@gmail.com wrote: FYI, lsof confirms that there are indeed many many open connections to the same FIFO: Like all of the lowest-level I/O functions, openFD just gives you back an integer, and the Fd type has no notion that there's an underlying system resource associated with it. It's your responsibility to manage it (i.e. clean up manually when catching an exception). What's more - if I understood the hypothesis correctly, that the exception occurs during openFd - that fails to return an Fd because the open(2) system call fails to return one, so it would presumably be an OS level bug if there's really an open file descriptor left from this. Donn ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Preventing leaked open file descriptors whencatching exceptions
Ah, thanks Bryan. I hadn't looked into it enough to realize that FDs are just ints and not ForeignPtrs w/ finalizers. Re: Donn's point. Well, yes, that would seem to be the case! But since I think a linux bug is unlikely, I'm afraid that there's something else going on here which I am not thinking of. I'll make a self contained test of this and send it out. On Tue, Feb 21, 2012 at 12:53 PM, Donn Cave d...@avvanta.com wrote: Quoth Bryan O'Sullivan b...@serpentine.com, On Tue, Feb 21, 2012 at 8:16 AM, Ryan Newton rrnew...@gmail.com wrote: FYI, lsof confirms that there are indeed many many open connections to the same FIFO: Like all of the lowest-level I/O functions, openFD just gives you back an integer, and the Fd type has no notion that there's an underlying system resource associated with it. It's your responsibility to manage it (i.e. clean up manually when catching an exception). What's more - if I understood the hypothesis correctly, that the exception occurs during openFd - that fails to return an Fd because the open(2) system call fails to return one, so it would presumably be an OS level bug if there's really an open file descriptor left from this. Donn ___ 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
[Haskell-cafe] Second Monad.Reader #20 call for copy
Second Call for Copy: The Monad.Reader - Issue 20 - Whether you're an established academic or have only just started learning Haskell, if you have something to say, please consider writing an article for The Monad.Reader! The submission deadline for Issue 20 will be: **Monday, March 5** The Monad.Reader The Monad.Reader is a electronic magazine about all things Haskell. It is less formal than journal, but somehow more enduring than a wiki- page. There have been a wide variety of articles: exciting code fragments, intriguing puzzles, book reviews, tutorials, and even half-baked research ideas. Submission Details ~~ Get in touch with me if you intend to submit something -- the sooner you let me know what you're up to, the better. Please submit articles for the next issue to me by e-mail (ezy...@mit.edu). Articles should be written according to the guidelines available from http://themonadreader.wordpress.com/contributing/ Please submit your article in PDF, together with any source files you used. The sources will be released together with the magazine under a BSD license. If you would like to submit an article, but have trouble with LaTeX please let me know and we'll work something out. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: network-socket-options 0.1
On 21 February 2012 14:57, Joey Adams joeyadams3.14...@gmail.com wrote:
I added a new package containing wrappers for getsockopt and setsockopt:
http://hackage.haskell.org/package/network-socket-options
The network package already has getSocketOption and setSocketOption.
The problem is, these don't work for socket options that aren't
represented by integers, such as SO_LINGER:
http://trac.haskell.org/network/ticket/23
Another, less serious problem is that getSocketOption and
setSocketOption don't leverage the type system as well as they could.
Many options are boolean values; it'd be better to get and set them
with 'Bool's instead of 'Int's.
network-socket-options implements options using getter and setter
functions, e.g.:
getLinger :: HasSocket sock = sock - IO (Maybe Seconds)
setLinger :: HasSocket sock = sock - Maybe Seconds - IO ()
type Seconds = Int
The HasSocket type class is defined to overload the getters and
setters to work on raw file descriptors, not just Socket objects.
This functionality should probably go in the network package itself.
However, I decided to release it as a separate package so I could
start using it sooner. If people like it enough, perhaps the network
package can absorb it, as was done with network-bytestring.
Hi Joey,
awesome! I've prepared some patches for network to add this module and
its tests, in this branch:
https://github.com/kfish/network/tree/options
I didn't modify any other modules, perhaps Network.Socket.Options
should be re-exported from Network.Socket, and perhaps
{get,set}SocketOption should be deprecated?
network$ autoreconf
network$ cabal configure --enable-tests
network$ cabal build
network$ cabal test
Running 3 test suites...
Test suite options: RUNNING...
Test suite options: PASS
Test suite logged to: dist/test/network-2.3.0.11-options.log
Test suite uri: RUNNING...
Test suite uri: PASS
Test suite logged to: dist/test/network-2.3.0.11-uri.log
Test suite simple: RUNNING...
Test suite simple: PASS
Test suite logged to: dist/test/network-2.3.0.11-simple.log
3 of 3 test suites (3 of 3 test cases) passed.
Conrad.
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Re: [Haskell-cafe] ANN: network-socket-options 0.1
On Tue, Feb 21, 2012 at 7:36 PM, Conrad Parker con...@metadecks.org wrote:
awesome! I've prepared some patches for network to add this module and
its tests, in this branch:
https://github.com/kfish/network/tree/options
Cool, thanks!
I didn't modify any other modules, perhaps Network.Socket.Options
should be re-exported from Network.Socket, and perhaps
{get,set}SocketOption should be deprecated?
I agree with deprecating getSocketOption and setSocketOption. Don't
remove them, just deprecate them. Network.Socket.Options doesn't
implement all of the options {get,set}SocketOption has, yet (e.g.
RecvLowWater).
I'm not sure about re-exporting Network.Socket.Options, though.
That's a lot to dump into the namespace. Particularly worrisome names
include:
* getError
* getType
Note the following:
* I'm going to release network-socket-options 0.1.1 pretty soon. It
will add higher-level functions for setting socket timeouts, to work
around the lack of a proper IO manager for Windows:
http://trac.haskell.org/network/ticket/2
http://trac.haskell.org/network/ticket/31#comment:1
* Network.Socket has a getPeerCred function, which gets the
SO_PEERCRED socket option. Perhaps it should be moved to
Network.Socket.Options (re-exported in Network.Socket for backward
compatibility) and generalized with HasSocket like the other options.
* A couple of the tests in my test suite require root access.
Consider them optional, as they cover ground already pretty
well-covered by the other tests.
Thanks for the integration work.
-Joey
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Re: [Haskell-cafe] network-2.3.0.10 compiled for ghc 7.4.1 windows
Hi Alberto. Do we need cygwin to install your compiled package? I thought not (I'm not very versed on this) but when I tried cabal install network after extracting it I got: Configuring network-2.3.0.11... cabal: The package has a './configure' script. This requires a Unix compatibility toolchain such as MinGW+MSYS or Cygwin. cabal: Error: some packages failed to install: network-2.3.0.11 failed during the configure step. The exception was: ExitFailure 1 Best regards, and thanks for any help! - Matias ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Need Help.
Hello On Tue, Feb 21, 2012 at 8:32 PM, Manoj Chaudhari manoj...@gmail.com wrote: Hi, We are looking for senior technical resources with skills in Haskell/Functional programming. Experience : 6 to 20 years, Job Location : Pune (India). Out of curiosity, what will the job involve? Also, it is bad netiquette to use bcc when you don't need to -- next time, try entering Haskell Cafe in the to field instead. Chris Regards! Manoj ___ 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] network-2.3.0.10 compiled for ghc 7.4.1 windows
Hello Matias On Wed, Feb 22, 2012 at 4:02 PM, Matias Hernandez mhern...@gmail.com wrote: Hi Alberto. Do we need cygwin to install your compiled package? I don't believe you do. If memory doesn't fail me, the Haskell Platform includes a compiler (MinGW), but not a shell (MSYS). This page explains all: http://trac.haskell.org/haskell-platform/ticket/165 Chris I thought not (I'm not very versed on this) but when I tried cabal install network after extracting it I got: Configuring network-2.3.0.11... cabal: The package has a './configure' script. This requires a Unix compatibility toolchain such as MinGW+MSYS or Cygwin. cabal: Error: some packages failed to install: network-2.3.0.11 failed during the configure step. The exception was: ExitFailure 1 Best regards, and thanks for any help! - Matias ___ 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] network-2.3.0.10 compiled for ghc 7.4.1 windows
Hi, you do need msys or cygwin for cabal installing network msys at http://sourceforge.net/projects/mingw/files/MSYS/Base/msys-core/msys-1.0.11/MSYS-1.0.11.exe/download You will then have to follow the instructions at http://www.mingw.org/wiki/MSYS. Please make sure that it uses ghc's mingw thanks Hemanth K On Wed, Feb 22, 2012 at 8:32 AM, Matias Hernandez mhern...@gmail.comwrote: Hi Alberto. Do we need cygwin to install your compiled package? I thought not (I'm not very versed on this) but when I tried cabal install network after extracting it I got: Configuring network-2.3.0.11... cabal: The package has a './configure' script. This requires a Unix compatibility toolchain such as MinGW+MSYS or Cygwin. cabal: Error: some packages failed to install: network-2.3.0.11 failed during the configure step. The exception was: ExitFailure 1 Best regards, and thanks for any help! - Matias ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- I drink I am thunk. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: hp2html, a tool for viewing GHC heap-profiles
On Tue, Feb 21, 2012 at 7:36 PM, Iavor Diatchki iavor.diatc...@gmail.com wrote: Hello, I made a new version of `hp2html` (0.2), which shows the legend by default (take a look at at the attached screen shot). If the legend is in the way, you can turn it off (and on) by clicking on the button at the top of the screen. Nice! -- Johan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] ANN: network-socket-options 0.1
I released network-socket-options 0.2, adding setSocketTimeouts and setHandleTimeouts. I'll post an announcement in a separate thread once the Haddock documentation is generated. -Joey ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
On 2/19/12 10:44 PM, Jack Henahan wrote: (or any other method which applies the quarantine flag) And you can always use xattr in order to delete that flag, if need be. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Haskell development in Mac OS X after Gatekeeper
On 2/20/12 4:31 PM, Richard O'Keefe wrote: On 20/02/2012, at 5:53 PM, Brandon Allbery wrote: Bzuh? Since you are running Lion and I am not, it isn't _that_ surprising that we see different things. It remains surprising that in 10.6.8 the xattr command is there but its manual page is not. The manpage is also missing on earlier versions (like my 10.5.8 laptop). Though usually for things like this you can just pass -? and either (1) it'll be recognized so a help message will be displayed, or (2) it won't be recognized and hence a help message will be displayed. Passing -? is safer than trying to run the program with no options, since many programs will do stuff even without options/arguments. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad laws in presence of bottoms
On 2/21/12 11:27 AM, MigMit wrote:
Ehm... why exactly don't domain products form domains?
One important property of domains[1] is that they have a unique bottom
element. Given domains A and B, let us denote the domain product as:
(A,B) def= { (a,b) | a - A, b - B }
Which will inherit an ordering in the obvious/free way from the domain
orderings on A and B. Since both A and B are domains, they have bottom
elements:
exists a0:A. forall a:A. (a0 =_A a)
exists b0:B. forall b:B. (b0 =_B b)
However, there is no free ordering on:
{ (a0,b) | b - B } \cup { (a,b0) | a - A }
So all of those are minimal elements of (A,B) but none of them is a
unique minimum; hence (A,B) is not a domain.
The smash product gets around this because it takes all those elements
and makes them equal, just like a strict tuple would in Haskell.
[1] This is in the sense of domain theory. It has nothing (per se) to do
with the many other uses of the term domain in mathematics.
--
Live well,
~wren
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Re: [Haskell-cafe] Monad laws in presence of bottoms
On 2/21/12 11:54 AM, Dan Doel wrote: On Tue, Feb 21, 2012 at 10:44 AM, wren ng thorntonw...@freegeek.org wrote: That's a similar sort of issue, just about whether undefined == (undefined,undefined) or not. If the equality holds then tuples would be domain products[1], but domain products do not form domains! ... [1] Also a category-theoretic product. This doesn't make much sense to me, either. If it's a category theoretic product in a category of domains, then the product must be a domain, no? It's a category-theoretic product, but not for the category of domains. Let Set be the category of sets and set-theoretic functions. And let pDCPO be the category of (pointed) domains and their homomorphisms. The category-theoretic product of A and B is just some triple (C, pi_A : C - A, pi_B : C - B) such that forall D, forall f : D - A, and forall g : D - B, there exists a unique h : D - C such that f = pi_A . h and g = pi_B . h ---in other words, it's the limit of a functor from the category with two objects and no morphisms which maps one object to A and the other object to B. The (domain-theoretic) domain product was discussed in my previous message to MigMit. It's a category-theoretic product in Set (among other categories) because the necessary morphisms exist and they satisfy the necessary equations. Moreover, in Set the domain product coincides with the cartesian product (we just forget about the orderings on the input domains and the resulting product). Hence, since the cartesian product is a category-theoretic product for Set, we know that the domain product must be a category-theoretic product in Set. However, the domain product is not a category-theoretic product in pDCPO. First off, the objects in pDCPO are domains, but since the domain product of A and B has no bottom it can't be a domain, so it can't be an object in pDCPO. Moreover, the morphisms in pDCPO will preserve the domain structure--- but there's no way to do that for a map from some domain C to the domain product of A and B, because there's no way to map the bottom of C to the bottom of the domain product (because there isn't one!). Conversely, the smash product is a category-theoretic product in pDCPO, but not in Set. Since every domain homomorphism must map bottoms to bottoms, it follows that f(d0) = a0 and g(d0) = b0. From this we have the necessary continuity to ensure that C, pi_A, and pi_B all exist in pDCPO. However, since there exist set-theoretic functions f and g which do not have that special property, the smash product is going to lose information about the non-bottom component of the product and so it cannot satisfy the necessary category-theoretic equations (in Set). For more on the category-theoretic study of domain theory, see http://www.cs.bham.ac.uk/~axj/pub/papers/handy1.pdf. You can search the pdf for pointed dcpo to jump to the relevant sections. Of course there are many different category-theoretic formalizations of domain theory, pDCPO is just one of them. To get a survey of the terrain, you may want to take a look at http://seclab.web.cs.illinois.edu/wp-content/uploads/2011/04/Gunter85.pdf. For a more direct introduction to domain theory and its application to lazy languages, see Geoffrey Burn's _Lazy Functional Languages: Abstract Interpretation and Compilation_. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad laws in presence of bottoms
22.02.2012, 09:30, wren ng thornton w...@freegeek.org:
On 2/21/12 11:27 AM, MigMit wrote:
Ehm... why exactly don't domain products form domains?
One important property of domains[1] is that they have a unique bottom
element. Given domains A and B, let us denote the domain product as:
(A,B) def= { (a,b) | a - A, b - B }
Which will inherit an ordering in the obvious/free way from the domain
orderings on A and B. Since both A and B are domains, they have bottom
elements:
exists a0:A. forall a:A. (a0 =_A a)
exists b0:B. forall b:B. (b0 =_B b)
However, there is no free ordering on:
{ (a0,b) | b - B } \cup { (a,b0) | a - A }
What? By definition, since, a0 = a and b0 = b, we have (a0, b0) = (a0, b)
and (a0, b0) = (a0, b0), so, (a0, b0) is clearly the bottom of A\times B.
So all of those are minimal elements of (A,B) but none of them is a
unique minimum; hence (A,B) is not a domain.
The smash product gets around this because it takes all those elements
and makes them equal, just like a strict tuple would in Haskell.
[1] This is in the sense of domain theory. It has nothing (per se) to do
with the many other uses of the term domain in mathematics.
Sorry, isn't the domain theory a part of mathematics?
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Re: [Haskell-cafe] Monad laws in presence of bottoms
On 2/21/12 11:54 AM, Dan Doel wrote: You don't have to get rid of bottom entirely (I think). If you make matches against products irrefutable, then you're again in the situation of seq being the only thing able to distinguish between _|_ and (_|_, _|_), so we could keep the current implementation (which is efficient) without it being possible to observe within the language. You just have to make seq not be magic on products. Miranda did this, except it still had a seq which exposed the lie. I thought Miranda identified _|_ with (_|_,_|_) ...though I admit I never really played around with Miranda. In any case, the point is that the weirdness of Haskell's products and function spaces are related around this issue of eta expansion. Haskell's sums are also weird (they're not category-theoretic coproducts), but that's not clearly an issue with eta. When it comes to practical utility, I think the choices Haskell made are quite nice. I'd love for smash products to have built-in syntax like tuples do, so I could use them cleanly rather than doing (((,) $! a) $! b) or defining my own ADT for them; but I understand entirely about why the Haskell committee decided that having two different versions of products/tuples would lead to API bloat and user confusion. However, while Haskell's choices are quite nice from a practical perspective, when it comes to theoretical rigor they're quite ugly. And that's the issue we're running into here when trying to figure out a theoretically sound way of defining how monads should behave with respect to bottoms. -- Live well, ~wren ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Monad laws in presence of bottoms
On 2/22/12 1:45 AM, Miguel Mitrofanov wrote:
However, there is no free ordering on:
{ (a0,b) | b- B } \cup { (a,b0) | a- A }
What? By definition, since, a0= a and b0= b, we have (a0, b0)= (a0, b) and (a0,
b0)= (a0, b0), so, (a0, b0) is clearly the bottom of A\times B.
Sorry, the ordering relation on domain products is defined by:
(a1,b1) =_(A,B) (a2,b2) if and only if a1 =_A a2 and b1 =_B b2
[1] This is in the sense of domain theory. It has nothing (per se) to do
with the many other uses of the term domain in mathematics.
Sorry, isn't the domain theory a part of mathematics?
Sure, domain theory is a part of mathematics, but the term domain is
used to mean a bunch of different and largely unrelated things. For example:
* in type theory and set theory the domain of a function is the set of
inputs on which it's defined
* in domain theory a domain is a partial order with a least element
and the property that every non-empty countable chain has a least upper
bound
* in ring theory a domain is is a ring which has no left nor right
zero-divisors
* in analysis a domain is any connected open subset of a
finite-dimensional vector space
etc.
--
Live well,
~wren
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Re: [Haskell-cafe] Monad laws in presence of bottoms
On Wed, Feb 22, 2012 at 1:40 AM, wren ng thornton w...@freegeek.org wrote: It's a category-theoretic product, but not for the category of domains. Let Set be the category of sets and set-theoretic functions. And let pDCPO be the category of (pointed) domains and their homomorphisms. The (domain-theoretic) domain product was discussed in my previous message to MigMit. It's a category-theoretic product in Set (among other categories) because the necessary morphisms exist and they satisfy the necessary equations. Moreover, in Set the domain product coincides with the cartesian product (we just forget about the orderings on the input domains and the resulting product). Hence, since the cartesian product is a category-theoretic product for Set, we know that the domain product must be a category-theoretic product in Set. Well, like Miguel, I don't see the problem with choosing the ordering: (a,b) = (a', b') iff a = a' and b = b' This makes (a0, b0) the bottom element. The only difference with Haskell's tuple types is that it lacks an extra element below (a0, b0); it's unlifted. It also seems to me that this _is_ the correct product for domains, unless I'm still sketchy on what you mean by domain. I don't think it matters that we're only considering strict homomorphisms. Conversely, the smash product is a category-theoretic product in pDCPO, but not in Set. Since every domain homomorphism must map bottoms to bottoms, it follows that f(d0) = a0 and g(d0) = b0. From this we have the necessary continuity to ensure that C, pi_A, and pi_B all exist in pDCPO. However, since there exist set-theoretic functions f and g which do not have that special property, the smash product is going to lose information about the non-bottom component of the product and so it cannot satisfy the necessary category-theoretic equations (in Set). The smash product is not a product for domains (in general), either. You are not allowed to throw away the components for such a product, because given a homomorphism f that maps everything to a0, pi_B . f,g maps everything to b0, regardless of what g is. -- Dan ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
