Re: [Haskell-cafe] Can a GC delay TCP connection formation?
Jeff Are you certain that all the delay can be laid at the GHC runtime? How much of the end-to-end delay budget is being allocated to you? I recently moved a static website from a 10-year old server in telehouse into AWS in Ireland and watched the access time (HTTP GET to check time on top index page) increase by 150ms. Neil On 27 Nov 2012, at 19:02, Jeff Shaw shawj...@gmail.com wrote: Hello Timothy and others, One of my clients hosts their HTTP clients in an Amazon cloud, so even when they turn on persistent HTTP connections, they use many connections. Usually they only end up sending one HTTP request per TCP connection. My specific problem is that they want a response in 120 ms or so, and at times they are unable to complete a TCP connection in that amount of time. I'm looking at on the order of 100 TCP connections per second, and on the order of 1000 HTTP requests per second (other clients do benefit from persistent HTTP connections). Once each minute, a thread of my program updates a global state, stored in an IORef, and updated with atomicModifyIORef', based on query results via HDBC-obdc. The query results are strict, and atomicModifyIORef' should receive the updated state already evaluated. I reduced the amount of time that query took from tens of seconds to just a couple, and for some reason that reduced the proportion of TCP timeouts drastically. The approximate before and after TCP timeout proportions are 15% and 5%. I'm not sure why this reduction in timeouts resulted from the query time improving, but this discovery has me on the task of removing all database code from the main program and into a cron job. My best guess is that HDBC-odbc somehow disrupts other communications while it waits for the DB server to respond. To respond to Ertugrul, I'm compiling with -threaded, and running with +RTS -N. I hope this helps describe my problem. I c an probably come up with some hard information if requested, E.G. threadscope. Jeff On 11/27/2012 10:55 AM, timothyho...@seznam.cz wrote: Could you give us more info on what your constraints are? Is it necessary that you have a certain number of connections per second, or is it necessary that the connection results very quickly after some other message is received? ___ 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] Conduit and pipelined protocol processing using a threadpool
On Wed, 2012-11-28 at 09:17 +0200, Michael Snoyman wrote: On Tue, Nov 27, 2012 at 7:25 PM, Nicolas Trangez nico...@incubaid.com wrote: Michael, On Tue, 2012-11-27 at 17:14 +0200, Michael Snoyman wrote: I think the stm-conduit package[1] may be helpful for this use case. Each time you get a new command, you can fork a thread and give it the TBMChan to write to, and you can use sourceTBMChan to get a source to send to the client. That's +- what I had in mind. I did find stm-conduit before and did try to get the thing working using it, but these attempts failed. I attached an example which might clarify what I intend to do. I'm aware it contains several potential bugs (leaking threads etc), but that's beside the question ;-) If only I could figure out what to put on the 3 lines of comment I left in there... Thanks for your help, Nicolas The issue is that you're trying to put everything into a single Conduit, which forces reading and writing to occur in a single thread of execution. Since you want your writing to be triggered by a separate event (data being available on the Chan), you're running into limitations. The reason network-conduit provides a Source for the incoming data and a Sink for outgoing data is specifically to address your use case. You want to take the data from the Source and put it into the Chan in one thread, and take the data from the other Chan and put it into the Sink in a separate thread. Something like: myApp appdata = do chan1 - ... chan2 - ... replicateM_ 5 $ forkIO $ worker chan1 chan2 forkIO $ appSource appdata $$ sinkTBMChan chan1 sourceTBMChan chan2 $$ appSink appdata You'll also want to make sure to close chan1 and chan2 to make sure that your threads stop running. Thanks, I +- figured that out last night. Only thing left is managing the handshake before forking off the workers, if possible (otherwise things become very messy IMHO), but ResumableSources etc might be of use here. Maybe there's a library somewhere in here... Thanks a bunch, Nicolas ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How to incrementally update list
Problem is following short program:list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = srun n s = run (n-1) $ advance s main = dolet s = run 5000 listputStrLn $ show s I want to incrementally update list lot of times, but don't knowhow to do this.Since Haskell does not have loops I have to use recursion,but problem is that recursive calls keep previous/state parameterleading to excessive stack.and memory usage.I don't know how to tell Haskell not to keep previousstate rather to release so memory consumption becomesmanagable. Is there some solution to this problem as I think it is rathercommon? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to incrementally update list
TCO + strictnesses annotations should take care of your problem. On 28 Nov 2012 11:44, Branimir Maksimovic bm...@hotmail.com wrote: Problem is following short program: list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = s run n s = run (n-1) $ advance s main = do let s = run 5000 list putStrLn $ show s I want to incrementally update list lot of times, but don't know how to do this. Since Haskell does not have loops I have to use recursion, but problem is that recursive calls keep previous/state parameter leading to excessive stack.and memory usage. I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomes managable. Is there some solution to this problem as I think it is rather common? ___ 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] How to incrementally update list
Here's a version that works: *import Control.DeepSeq* list = [1,2,3,4,5] advance l = *force $* map (\x - x+1) l run 0 s = s run n s = run (n-1) $ advance s main = do let s = run 5000 list putStrLn $ show s The problem is that you build of a huge chain of updates to the list. If we just commit each update as it happens, we'll use a constant amount of memory. Haskell's laziness is tricky to understand coming from imperative languages, but once you figure out its evaluation rules, you'll begin to see the elegance. Ηope this helps, - Clark On Wed, Nov 28, 2012 at 7:07 AM, Benjamin Edwards edwards.b...@gmail.comwrote: TCO + strictnesses annotations should take care of your problem. On 28 Nov 2012 11:44, Branimir Maksimovic bm...@hotmail.com wrote: Problem is following short program: list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = s run n s = run (n-1) $ advance s main = do let s = run 5000 list putStrLn $ show s I want to incrementally update list lot of times, but don't know how to do this. Since Haskell does not have loops I have to use recursion, but problem is that recursive calls keep previous/state parameter leading to excessive stack.and memory usage. I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomes managable. Is there some solution to this problem as I think it is rather common? ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to incrementally update list
I want to incrementally update list lot of times, but don't know how to do this. Are you using the right data structure for the job? Maybe you want an array instead? -- Kim-Ee On Wed, Nov 28, 2012 at 6:43 PM, Branimir Maksimovic bm...@hotmail.comwrote: Problem is following short program: list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = s run n s = run (n-1) $ advance s main = do let s = run 5000 list putStrLn $ show s I want to incrementally update list lot of times, but don't know how to do this. Since Haskell does not have loops I have to use recursion, but problem is that recursive calls keep previous/state parameter leading to excessive stack.and memory usage. I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomes managable. Is there some solution to this problem as I think it is rather common? ___ 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] OpenAL - compiling problem
Dear Haskell Cafe, I tried installing the haskell openal library via cabal install openal I get the following error: ... [ 7 of 30] Compiling Sound.OpenAL.ALC.QueryUtils ( Sound/OpenAL/ALC/QueryUtils.hs, dist/build/Sound/OpenAL/ALC/QueryUtils.o ) Sound/OpenAL/ALC/QueryUtils.hs:66:1: Unacceptable argument type in foreign declaration: ALCdevice When checking declaration: foreign import ccall unsafe static alcGetString alcGetString :: ALCdevice - ALCenum - IO (Ptr ALCchar) Sound/OpenAL/ALC/QueryUtils.hs:102:1: Unacceptable argument type in foreign declaration: ALCdevice When checking declaration: foreign import ccall unsafe static alcGetIntegerv alcGetIntegerv :: ALCdevice - ALCenum - ALCsizei - Ptr ALCint - IO () Sound/OpenAL/ALC/QueryUtils.hs:120:1: Unacceptable argument type in foreign declaration: ALCdevice When checking declaration: foreign import ccall unsafe static alcIsExtensionPresent alcIsExtensionPresent_ :: ALCdevice - Ptr ALCchar - IO ALCboolean Failed to install OpenAL-1.4.0.1 cabal: Error: some packages failed to install: OpenAL-1.4.0.1 failed during the building phase. The exception was: ExitFailure 1 The version of my openal installation is 1.14-1. I also tried to install via darcs, but the error is the same. Any ideas? Greets Gary ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How to incrementally update list
Thank you very much! That solved it ;)I had to put explicit type signature in front of advance in order to compile From: cgae...@uwaterloo.ca Date: Wed, 28 Nov 2012 08:01:38 -0500 Subject: Re: [Haskell-cafe] How to incrementally update list To: edwards.b...@gmail.com CC: bm...@hotmail.com; haskell-cafe@haskell.org Here's a version that works: import Control.DeepSeq list = [1,2,3,4,5] advance l = force $ map (\x - x+1) l run 0 s = srun n s = run (n-1) $ advance s main = dolet s = run 5000 listputStrLn $ show s The problem is that you build of a huge chain of updates to the list. If we just commit each update as it happens, we'll use a constant amount of memory. Haskell's laziness is tricky to understand coming from imperative languages, but once you figure out its evaluation rules, you'll begin to see the elegance. Ηope this helps, - Clark On Wed, Nov 28, 2012 at 7:07 AM, Benjamin Edwards edwards.b...@gmail.com wrote: TCO + strictnesses annotations should take care of your problem. On 28 Nov 2012 11:44, Branimir Maksimovic bm...@hotmail.com wrote: Problem is following short program:list = [1,2,3,4,5] advance l = map (\x - x+1) l run 0 s = srun n s = run (n-1) $ advance s main = dolet s = run 5000 listputStrLn $ show s I want to incrementally update list lot of times, but don't knowhow to do this. Since Haskell does not have loops I have to use recursion,but problem is that recursive calls keep previous/state parameterleading to excessive stack.and memory usage.I don't know how to tell Haskell not to keep previous state rather to release so memory consumption becomesmanagable. Is there some solution to this problem as I think it is rathercommon? ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] SOX - play simple
Dear Cafe, after installing the Sox library (cabal install sox) I wanted to let run a minimal example from http://hackage.haskell.org/packages/archive/sox/0.2.2.2/doc/html/Sound-Sox-Play.html module Main where import Sound.Sox.Play import Sound.Sox.Signal.List --import Sound.Sox.Option.Format import Data.Int main = do simple Sound.Sox.Signal.List.put Option.none 11025 (iterate (1000+) (0::Data.Int.Int16)) in this version, I get the error: Not in scope: `Option.none' So, I imported Sound.Sox.Option.Format, because there is a none with the right type. I also changed Option.none to none. Then the program compiles and I get the runtime error: fd:4: hClose: resource vanished (Broken pipe) What is wrong here? I appreciate your help! Best regards, Gary ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can a GC delay TCP connection formation?
Jeff, this is somewhat off topic, but interesting. Are telehouse and AWS physically close? Was this latency increase not expected due to geography? Alexander On 28 November 2012 06:21, Neil Davies semanticphilosop...@gmail.comwrote: Jeff Are you certain that all the delay can be laid at the GHC runtime? How much of the end-to-end delay budget is being allocated to you? I recently moved a static website from a 10-year old server in telehouse into AWS in Ireland and watched the access time (HTTP GET to check time on top index page) increase by 150ms. Neil On 27 Nov 2012, at 19:02, Jeff Shaw shawj...@gmail.com wrote: Hello Timothy and others, One of my clients hosts their HTTP clients in an Amazon cloud, so even when they turn on persistent HTTP connections, they use many connections. Usually they only end up sending one HTTP request per TCP connection. My specific problem is that they want a response in 120 ms or so, and at times they are unable to complete a TCP connection in that amount of time. I'm looking at on the order of 100 TCP connections per second, and on the order of 1000 HTTP requests per second (other clients do benefit from persistent HTTP connections). Once each minute, a thread of my program updates a global state, stored in an IORef, and updated with atomicModifyIORef', based on query results via HDBC-obdc. The query results are strict, and atomicModifyIORef' should receive the updated state already evaluated. I reduced the amount of time that query took from tens of seconds to just a couple, and for some reason that reduced the proportion of TCP timeouts drastically. The approximate before and after TCP timeout proportions are 15% and 5%. I'm not sure why this reduction in timeouts resulted from the query time improving, but this discovery has me on the task of removing all database code from the main program and into a cron job. My best guess is that HDBC-odbc somehow disrupts other communications while it waits for the DB server to respond. To respond to Ertugrul, I'm compiling with -threaded, and running with +RTS -N. I hope this helps describe my problem. I c an probably come up with some hard information if requested, E.G. threadscope. Jeff On 11/27/2012 10:55 AM, timothyho...@seznam.cz wrote: Could you give us more info on what your constraints are? Is it necessary that you have a certain number of connections per second, or is it necessary that the connection results very quickly after some other message is received? ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Equality test between types that returns type-level Bool ?
By tracing how unittyped produced the 'True-s and 'False-s in the error messages, and by Oleg's lecture, 1 meter + 5 second interactive:17:9: Couldn't match type 'False with 'True When using functional dependencies to combine UnitTyped.And 'False 'False 'False, arising from the dependency `a b - c' in the instance declaration in `UnitTyped' UnitTyped.And 'False 'False 'True, arising from a use of `+' at interactive:17:9 In the expression: 1 meter + 5 second In an equation for `it': it = 1 meter + 5 second I understood how type-level equalities https://github.com/nushio3/dimensional-tf/blob/master/attic/typeeq-01.hs and type-level list lookups https://github.com/nushio3/dimensional-tf/blob/master/attic/typeeq-03.hs can be implemented using overlapped instances. Thank you for the instructions. and I'm looking forward to see TYPEREP with ghc7.6.1's promoted integers and TH pretty soon! 2012/11/27 Takayuki Muranushi muranu...@gmail.com Dear Gábor, Erik, and Oleg, Thank you for your advices. Also what I have wanted, the extensible dimensional type system, has just been released. http://hackage.haskell.org/package/unittyped-0.1 Now I have homeworks to test these, thank you! 2012/11/27 Erik Hesselink hessel...@gmail.com If you're up for it, Oleg has a lot of interesting material about this subject [1]. Regards, Erik [1] http://okmij.org/ftp/Haskell/typeEQ.html On Sun, Nov 25, 2012 at 9:36 AM, Takayuki Muranushi muranu...@gmail.comwrote: Is it possible to write type family SameType a b :: Bool which returns True if a and b are the same type, and False otherwise? I encountered this problem when I was practicing promoted lists and tuples in ghc-7.6.1. One of my goal for practice is to write more modular version of extensible-dimensional calculations, and to understand whether ghc-7.6.1 is capable of it. http://hackage.haskell.org/packages/archive/dimensional/0.10.2/doc/html/Numeric-Units-Dimensional-Extensible.html Some of my attempts: https://github.com/nushio3/dimensional-tf/blob/master/attic/list-02.hs This fails because :==: is not an equality test between a and b, but is a equality test within a (promoted) kind. https://github.com/nushio3/dimensional-tf/blob/master/attic/list-03.hs This fails because type instance declarations are not read from top to bottom. (not like function declarations.) https://github.com/nushio3/dimensional-tf/blob/master/attic/map-03.hs I could define a lookup using class constraints, but when I use it, results in overlapping instances. So, will somebody teach me which of the following is correct? * We can write a type family SameType a b :: Bool * We cannot do that because of theoretical reason (that leads to non-termination etc.) * We cannot write SameType, but there are ways to write functions like 'filter' and 'merge' , over type-level lists, without using SameType. Always grateful to your help, -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] delete http://www.haskell.org/haskellwiki/Haskell_IDE
Hi. There is more verbose page http://www.haskell.org/haskellwiki/IDEs . I registered on http://www.haskell.org/haskellwiki/ , but have not found the Delete Page command, wiki software help pages, or feedback channel, so I'm writing here. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Can not use ST monad with polymorphic function
Hi Cafe, I try to implement some sort of monadic fold, where traversing is polymorphic over monad type. The problem is that the code below does not compile. It works with any monad except for ST. I suspect that monomorphism is at work here, but it is unclear for me how to change the code to make it work with ST. fold :: Monad m = (Int - m ()) - m () fold f = mapM_ f [0..20] selectFold :: Monad m = String - IO ((Int - m ()) - m ()) selectFold method = do -- in real program I'd like to choose between -- different fold methods, based on some IO context return fold useFold :: Monad m = ((Int - m ()) - m ()) - m () useFold fold' = fold' f where f _ = return () -- some trivial iterator main = do fold'' - selectFold some-method-id print $ runST $ useFold fold'' Thank you! Dmitry ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] computation over containers, greatly simplified notation.
Dear all, I came up with an idea to greatly simplify some kinds of array computations. It should work well with many kinds of arrays. Is this new? https://gist.github.com/4162375 These few days, I've been trying to rewrite a hydrodynamic simulation code that used Data.Vector (~250 lines), to Repa [1] . It seemed promising, but soon I realized that I needed to use Repa.map and Repa.zipWith almost everywhere. I need careful thinking to transform every lines (that used vector's indexing) to Repa's point-free stile. Is there any better ways? Then I realized that I was the author of Paraiso [2], a DSL for stencil computation. One of its feature is to write down array computation just as if it were scalar computation. Basically what I need is ZipList-like Applicative instances for vectors and Repa arrays. Why not they support ZipVector? Because 'pure' of zipList was an infinite list and you can't do infinite vectors. Then I came up with this idea. https://gist.github.com/4162375 the wrapper W does several things: it represents the 'pure,' homogeneous array in a space-efficient manner, and also serves as a newtype-wrapper of Num (and possibly Fractional, Floating...) instances. Questions are: is this technology new? or promising? doomed? It seems to me like a free-Applicative, like the free-Monad theory. Are they related? The function 'backend' helps to mix in the non-zip-like computations. How can we remove the 'undefined' in the 'backend?' Some of Repa computations are Monads. W needs to be a monad transformer to incooperate this. Also I'm grateful to past cafe discussion on existing Zippable implementations [3][4] . [1] hackage.haskell.org/package/repa [2] http://hackage.haskell.org/package/Paraiso [3] http://www.haskell.org/pipermail/haskell-cafe/2009-July/064403.html [4] http://hackage.haskell.org/packages/archive/category-extras/latest/doc/html/Control-Functor-Zip.html -- Takayuki MURANUSHI The Hakubi Center for Advanced Research, Kyoto University http://www.hakubi.kyoto-u.ac.jp/02_mem/h22/muranushi.html ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenAL - compiling problem
Hi Gary Which version of GHC are you using? My suspicion is that ALCdevice might be a newtype falling foul of recent changes to GHC... v7.4.1: GHC now requires, as per the standard, that if a newtype is used in an FFI declaration, then the constructor for that type must be in scope. For now you only get a warning if it is not, but in the future this will be an error. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenAL - compiling problem
On 11/28/2012 07:01 PM, Stephen Tetley wrote: Hi Gary Which version of GHC are you using? My suspicion is that ALCdevice might be a newtype falling foul of recent changes to GHC... v7.4.1: GHC now requires, as per the standard, that if a newtype is used in an FFI declaration, then the constructor for that type must be in scope. For now you only get a warning if it is not, but in the future this will be an error. Thank you for answering. Maybe you're right, I'm using v7.6.1. So I can only wait for a patch or use an older version of ghc, right? ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] OpenAL - compiling problem
I think OpenAL is now unmaintained. You could try to find AndrewMiller who updated the last version, otherwise you might have to patch it yourself or ask a developer of a dependent package if they would consider pushing another unmaintained release to Hackage. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] How can I avoid buffered reads?
I have some code that reads (infrequently) small amounts of data from
/dev/urandom, and because this is pretty infrequent, I simply open the
handle and close it every time I need some random bytes.
The problem is that I recently discovered that, thanks to buffering within
GHC, I was actually reading 8096 bytes when I only need 16 bytes, and
thus wasting entropy. Moreover calling hSetBuffering handle NoBuffering
did not change this behavior.
I'm not sure if this behavior is a bug or a feature, but in any case it's
unacceptable for dealing with /dev/urandom. Probably the simplest way to
fix this is to write a little C helper function that will read from
/dev/urandom for me, so that I have precise control over the system calls
involved. But I'm curious if GHC can manage this use case correctly;
I've just started digging into the GHC.IO code myself.
Best,
Leon
{-# LANGUAGE BangPatterns, ViewPatterns #-}
import Control.Applicativeimport Data.Bitsimport
Data.Word(Word64)import qualified Data.ByteString as Simport
qualified Data.ByteString.Lazy as Limport
Data.ByteString.Internal (c2w)import qualified System.IOas
IOimport qualified Data.Binary.Getas Get
showHex :: Word64 - S.ByteStringshowHex n = s
where
(!s,_) = S.unfoldrN 16 f n
f n = Just (char (n `shiftR` 60), n `shiftL` 4)
char (fromIntegral - i)
| i 10= (c2w '0' - 0) + i
| otherwise = (c2w 'a' - 10) + i
twoRandomWord64s :: IO (Word64,Word64)twoRandomWord64s =
IO.withBinaryFile /dev/urandom IO.ReadMode $ \handle - do
IO.hSetBuffering handle IO.NoBuffering
Get.runGet ((,) $ Get.getWord64host * Get.getWord64host) $
L.hGet handle 16
main = do
(x,y) - twoRandomWord64s
S.hPutStrLn IO.stdout (S.append (showHex x) (showHex y))
{- Relevant part of strace:
open(/dev/urandom, O_RDONLY|O_NOCTTY|O_NONBLOCK) = 3
fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 9), ...}) = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL
(Invalid argument)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL
(Invalid argument)
read(3,
N\304\4\367/\26c\\3218\237f\214yKg~i\310\r\262\\224H\340y\n\376V?\265\344...,
8096) = 8096
close(3)= 0
-}
___
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Haskell-Cafe@haskell.org
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Re: [Haskell-cafe] How can I avoid buffered reads?
As an alternative, If there existed a Haskell package to give you fast
cryptographically secure random numbers or use the new Intel RDRAND
instruction (when available) would that interest you?
Also, what you are doing is identical to the entropy package on
hackage, which probably suffers from the same bug/performance issue.
Cheers,
Thomas
On Wed, Nov 28, 2012 at 11:38 AM, Leon Smith leon.p.sm...@gmail.com wrote:
I have some code that reads (infrequently) small amounts of data from
/dev/urandom, and because this is pretty infrequent, I simply open the
handle and close it every time I need some random bytes.
The problem is that I recently discovered that, thanks to buffering within
GHC, I was actually reading 8096 bytes when I only need 16 bytes, and
thus wasting entropy. Moreover calling hSetBuffering handle NoBuffering
did not change this behavior.
I'm not sure if this behavior is a bug or a feature, but in any case it's
unacceptable for dealing with /dev/urandom. Probably the simplest way to
fix this is to write a little C helper function that will read from
/dev/urandom for me, so that I have precise control over the system calls
involved. But I'm curious if GHC can manage this use case correctly;
I've just started digging into the GHC.IO code myself.
Best,
Leon
{-# LANGUAGE BangPatterns, ViewPatterns #-}
import Control.Applicative
import Data.Bits
import Data.Word(Word64)
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import Data.ByteString.Internal (c2w)
import qualified System.IOas IO
import qualified Data.Binary.Getas Get
showHex :: Word64 - S.ByteString
showHex n = s
where
(!s,_) = S.unfoldrN 16 f n
f n = Just (char (n `shiftR` 60), n `shiftL` 4)
char (fromIntegral - i)
| i 10= (c2w '0' - 0) + i
| otherwise = (c2w 'a' - 10) + i
twoRandomWord64s :: IO (Word64,Word64)
twoRandomWord64s = IO.withBinaryFile /dev/urandom IO.ReadMode $ \handle -
do
IO.hSetBuffering handle IO.NoBuffering
Get.runGet ((,) $ Get.getWord64host * Get.getWord64host) $ L.hGet
handle 16
main = do
(x,y) - twoRandomWord64s
S.hPutStrLn IO.stdout (S.append (showHex x) (showHex y))
{- Relevant part of strace:
open(/dev/urandom, O_RDONLY|O_NOCTTY|O_NONBLOCK) = 3
fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 9), ...}) = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL (Invalid
argument)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL (Invalid
argument)
read(3,
N\304\4\367/\26c\\3218\237f\214yKg~i\310\r\262\\224H\340y\n\376V?\265\344...,
8096) = 8096
close(3)= 0
-}
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Re: [Haskell-cafe] delete http://www.haskell.org/haskellwiki/Haskell_IDE
On Wed, Nov 28, 2012 at 07:08:16PM +0200, Roman Beslik wrote: Hi. There is more verbose page http://www.haskell.org/haskellwiki/IDEs . I registered on http://www.haskell.org/haskellwiki/ , but have not found the Delete Page command, wiki software help pages, or feedback channel, so I'm writing here. Deleting pages is rather drastic and not enabled for normal users. It is probably not a good idea anyway -- what if there are other pages that link to it? Just delete all the content and replace it with a redirect to the IDEs page. -Brent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can not use ST monad with polymorphic function
Yes, monomorphism. do binding requires your fold'' to be of some monomorphic
type, but runST requires some polymorphism.
If you want, you can use special type like that:
data FoldSTVoid = FoldSTVoid {runFold :: forall a. (Int - ST a ()) - ST a ()}
fold :: Monad m = (Int - m ()) - m ()
fold f = mapM_ f [0..20]
selectFold :: String - IO FoldSTVoid -- ((Int - m ()) - m ())
selectFold method = do
-- in real program I'd like to choose between
-- different fold methods, based on some IO context
return $ FoldSTVoid fold
useFold :: FoldSTVoid - ST a ()
useFold fold' = runFold fold' f
where f _ = return () -- some trivial iterator
main = do
fold'' - selectFold some-method-id
print $ runST $ useFold fold''
On Nov 28, 2012, at 9:52 PM, Dmitry Kulagin dmitry.kula...@gmail.com wrote:
Hi Cafe,
I try to implement some sort of monadic fold, where traversing is polymorphic
over monad type.
The problem is that the code below does not compile. It works with any monad
except for ST.
I suspect that monomorphism is at work here, but it is unclear for me how to
change the code to make it work with ST.
fold :: Monad m = (Int - m ()) - m ()
fold f = mapM_ f [0..20]
selectFold :: Monad m = String - IO ((Int - m ()) - m ())
selectFold method = do
-- in real program I'd like to choose between
-- different fold methods, based on some IO context
return fold
useFold :: Monad m = ((Int - m ()) - m ()) - m ()
useFold fold' = fold' f
where f _ = return () -- some trivial iterator
main = do
fold'' - selectFold some-method-id
print $ runST $ useFold fold''
Thank you!
Dmitry
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Re: [Haskell-cafe] How can I avoid buffered reads?
On 11/28/2012 08:38 PM, Leon Smith wrote: I have some code that reads (infrequently) small amounts of data from /dev/urandom, and because this is pretty infrequent, I simply open the handle and close it every time I need some random bytes. The problem is that I recently discovered that, thanks to buffering within GHC, I was actually reading 8096 bytes when I only need 16 bytes, and thus wasting entropy. Moreover calling hSetBuffering handle NoBuffering did not change this behavior. I'm not sure if this behavior is a bug or a feature, but in any case it's unacceptable for dealing with /dev/urandom. Probably the simplest way to fix this is to write a little C helper function that will read from /dev/urandom for me, so that I have precise control over the system calls involved. But I'm curious if GHC can manage this use case correctly; I've just started digging into the GHC.IO code myself. Use openFd, fdReadBuf and closeFd from the System.Posix.IO.ByteString module in the 'unix' package. Those correspond directly to system calls and are thus unbuffered. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] delete http://www.haskell.org/haskellwiki/Haskell_IDE
A humble link What links here to the right will help you find those pages. On 28.11.12 21:53, Brent Yorgey wrote: is probably not a good idea anyway -- what if there are other pages that link to it? On Wed, Nov 28, 2012 at 07:08:16PM +0200, Roman Beslik wrote: Hi. There is more verbose page http://www.haskell.org/haskellwiki/IDEs . I registered on http://www.haskell.org/haskellwiki/ , but have not found the Delete Page command, wiki software help pages, or feedback channel, so I'm writing here. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] delete http://www.haskell.org/haskellwiki/Haskell_IDE
On Wed, Nov 28, 2012 at 3:24 PM, Roman Beslik rabes...@gmail.com wrote: A humble link What links here to the right will help you find those pages. Only for wikipages, nowhere else on the Internet. -- gwern http://www.gwern.net ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can a GC delay TCP connection formation?
On 11/27/2012 4:59 PM, Nicolas Wu wrote: Hi, I'm the maintainer of HDBC. I haven't yet released this code since it hasn't yet been fully tested. However, if you're happy with it, I'll push the version with proper ffi bindings up to Hackage. Nick Nick, I pulled the latest version of HDBC-odbc, and it appears to be working MUCH better than before. I now have 0% timeouts from httperf with 50 connections/second and timeout set to 0.1 seconds. It's looking like the safe imports vastly improved IO blocking. I haven't seen any new problems since the new version went live. Jeff ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can I avoid buffered reads?
Quite possibly, entropy does seem to be a pretty lightweight dependency...
Though doesn't recent kernels use rdrand to seed /dev/urandom if it's
available? So /dev/urandom is the most portable source of random numbers
on unix systems, though rdrand does have the advantage of avoiding system
calls, so it certainly would be preferable, especially if you need large
numbers of random numbers.
Best,
Leon
On Wed, Nov 28, 2012 at 2:45 PM, Thomas DuBuisson
thomas.dubuis...@gmail.com wrote:
As an alternative, If there existed a Haskell package to give you fast
cryptographically secure random numbers or use the new Intel RDRAND
instruction (when available) would that interest you?
Also, what you are doing is identical to the entropy package on
hackage, which probably suffers from the same bug/performance issue.
Cheers,
Thomas
On Wed, Nov 28, 2012 at 11:38 AM, Leon Smith leon.p.sm...@gmail.com
wrote:
I have some code that reads (infrequently) small amounts of data from
/dev/urandom, and because this is pretty infrequent, I simply open the
handle and close it every time I need some random bytes.
The problem is that I recently discovered that, thanks to buffering
within
GHC, I was actually reading 8096 bytes when I only need 16 bytes, and
thus wasting entropy. Moreover calling hSetBuffering handle
NoBuffering
did not change this behavior.
I'm not sure if this behavior is a bug or a feature, but in any case
it's
unacceptable for dealing with /dev/urandom. Probably the simplest way
to
fix this is to write a little C helper function that will read from
/dev/urandom for me, so that I have precise control over the system
calls
involved. But I'm curious if GHC can manage this use case correctly;
I've just started digging into the GHC.IO code myself.
Best,
Leon
{-# LANGUAGE BangPatterns, ViewPatterns #-}
import Control.Applicative
import Data.Bits
import Data.Word(Word64)
import qualified Data.ByteString as S
import qualified Data.ByteString.Lazy as L
import Data.ByteString.Internal (c2w)
import qualified System.IOas IO
import qualified Data.Binary.Getas Get
showHex :: Word64 - S.ByteString
showHex n = s
where
(!s,_) = S.unfoldrN 16 f n
f n = Just (char (n `shiftR` 60), n `shiftL` 4)
char (fromIntegral - i)
| i 10= (c2w '0' - 0) + i
| otherwise = (c2w 'a' - 10) + i
twoRandomWord64s :: IO (Word64,Word64)
twoRandomWord64s = IO.withBinaryFile /dev/urandom IO.ReadMode $
\handle -
do
IO.hSetBuffering handle IO.NoBuffering
Get.runGet ((,) $ Get.getWord64host * Get.getWord64host) $
L.hGet
handle 16
main = do
(x,y) - twoRandomWord64s
S.hPutStrLn IO.stdout (S.append (showHex x) (showHex y))
{- Relevant part of strace:
open(/dev/urandom, O_RDONLY|O_NOCTTY|O_NONBLOCK) = 3
fstat(3, {st_mode=S_IFCHR|0666, st_rdev=makedev(1, 9), ...}) = 0
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL
(Invalid
argument)
ioctl(3, SNDCTL_TMR_TIMEBASE or TCGETS, 0x7367e528) = -1 EINVAL
(Invalid
argument)
read(3,
N\304\4\367/\26c\\3218\237f\214yKg~i\310\r\262\\224H\340y\n\376V?\265\344...,
8096) = 8096
close(3)= 0
-}
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Re: [Haskell-cafe] How can I avoid buffered reads?
On 11/28/2012 09:31 PM, Leon Smith wrote: Quite possibly, entropy does seem to be a pretty lightweight dependency... Though doesn't recent kernels use rdrand to seed /dev/urandom if it's available? So /dev/urandom is the most portable source of random numbers on unix systems, though rdrand does have the advantage of avoiding system calls, so it certainly would be preferable, especially if you need large numbers of random numbers. There's no much information on this i think, but if you need large number of random numbers you should build a PRNG yourself on top of the best random seed you can get, and make sure you reseed your prng casually with more entropy bytes. Also if you don't have enough initial entropy, you should block. /dev/urandom is not the same thing on every unix system. leading to various assumptions broken when varying the unixes. It also varies with the hardware context: for example on an embedded or some virtualized platform, giving you really terrible entropy. -- Vincent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can a GC delay TCP connection formation?
On Wed, Nov 28, 2012 at 8:36 PM, Jeff Shaw shawj...@gmail.com wrote: On 11/27/2012 4:59 PM, Nicolas Wu wrote: I pulled the latest version of HDBC-odbc, and it appears to be working MUCH better than before. I now have 0% timeouts from httperf with 50 connections/second and timeout set to 0.1 seconds. It's looking like the safe imports vastly improved IO blocking. I haven't seen any new problems since the new version went live. That's great to hear! I'll aim to push this version to Hackage over the weekend. Nick ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] How can I avoid buffered reads?
If you have rdrand, there is no need to build your own PRNG on top of rdrand. RdRand already incorporates one so that it can produce random numbers as fast as they can be requested, and this number is continuously re-seeded with the on-chip entropy source. It would be nice to have a little more information about /dev/urandom and how it varies by OS and hardware, but on Linux and FreeBSD at least it's supposed to be a cryptographically secure RNG that incorporates a PRNG to produce numbers in case you exhaust the entropy pool. On Wed, Nov 28, 2012 at 5:00 PM, Vincent Hanquez t...@snarc.org wrote: On 11/28/2012 09:31 PM, Leon Smith wrote: Quite possibly, entropy does seem to be a pretty lightweight dependency... Though doesn't recent kernels use rdrand to seed /dev/urandom if it's available? So /dev/urandom is the most portable source of random numbers on unix systems, though rdrand does have the advantage of avoiding system calls, so it certainly would be preferable, especially if you need large numbers of random numbers. There's no much information on this i think, but if you need large number of random numbers you should build a PRNG yourself on top of the best random seed you can get, and make sure you reseed your prng casually with more entropy bytes. Also if you don't have enough initial entropy, you should block. /dev/urandom is not the same thing on every unix system. leading to various assumptions broken when varying the unixes. It also varies with the hardware context: for example on an embedded or some virtualized platform, giving you really terrible entropy. -- Vincent ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Can a GC delay TCP connection formation?
No - the difference is 6.5ms each way On 28 Nov 2012, at 14:44, Alexander Kjeldaas alexander.kjeld...@gmail.com wrote: Jeff, this is somewhat off topic, but interesting. Are telehouse and AWS physically close? Was this latency increase not expected due to geography? Alexander On 28 November 2012 06:21, Neil Davies semanticphilosop...@gmail.com wrote: Jeff Are you certain that all the delay can be laid at the GHC runtime? How much of the end-to-end delay budget is being allocated to you? I recently moved a static website from a 10-year old server in telehouse into AWS in Ireland and watched the access time (HTTP GET to check time on top index page) increase by 150ms. Neil On 27 Nov 2012, at 19:02, Jeff Shaw shawj...@gmail.com wrote: Hello Timothy and others, One of my clients hosts their HTTP clients in an Amazon cloud, so even when they turn on persistent HTTP connections, they use many connections. Usually they only end up sending one HTTP request per TCP connection. My specific problem is that they want a response in 120 ms or so, and at times they are unable to complete a TCP connection in that amount of time. I'm looking at on the order of 100 TCP connections per second, and on the order of 1000 HTTP requests per second (other clients do benefit from persistent HTTP connections). Once each minute, a thread of my program updates a global state, stored in an IORef, and updated with atomicModifyIORef', based on query results via HDBC-obdc. The query results are strict, and atomicModifyIORef' should receive the updated state already evaluated. I reduced the amount of time that query took from tens of seconds to just a couple, and for some reason that reduced the proportion of TCP timeouts drastically. The approximate before and after TCP timeout proportions are 15% and 5%. I'm not sure why this reduction in timeouts resulted from the query time improving, but this discovery has me on the task of removing all database code from the main program and into a cron job. My best guess is that HDBC-odbc somehow disrupts other communications while it waits for the DB server to respond. To respond to Ertugrul, I'm compiling with -threaded, and running with +RTS -N. I hope this helps describe my problem. I c an probably come up with some hard information if requested, E.G. threadscope. Jeff On 11/27/2012 10:55 AM, timothyho...@seznam.cz wrote: Could you give us more info on what your constraints are? Is it necessary that you have a certain number of connections per second, or is it necessary that the connection results very quickly after some other message is received? ___ 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 mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] A big hurray for lambda-case (and all the other good stuff)
Hi Everyone just wanted to drop by to say how much I like the new lambda case extension. I use it all the time and I just *love* how it relieves me from conjuring up dummy variables, which makes teh code not only esier to write but also to read. A big, huge thank you to the ghc developers. This has been so long on my wish list. Also much appreciated and long awaited: tuple sections (though I use them not quite as often). Both should *definitely* go into Haskell'13. Of course, thank you also for all the other beautiful stuff in ghc-7.6.1, especially PolyKinds, DataKinds etc. GHC is just simply amazing. You guys RULE THE WORLD! Cheers -- Ben Franksen () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
Tony Morris wrote: As a side note, I think a direct superclass of Functor for Monad is not a good idea, just sayin' class Functor f where fmap :: (a - b) - f a - f b class Functor f = Apply f where (*) :: f (a - b) - f a - f b class Apply f = Bind f where (=) :: (a - f b) - f a - f b class Apply f = Applicative f where unit :: a - f a class (Applicative f, Bind f) = Monad f where Same goes for Comonad (e.g. [] has (=) but not counit) ... and again for Monoid, Category, I could go on... Hi Tony even though I dismissed your mentioning this on the Haskell' list, I do have to admit that the proposal has a certain elegance. However, before I buy into this scheme, I'd like to see some striking examples for types with natural (or at least useful) Apply and Bind instances that cannot be made Applicative resp. Monad. Also, it is not clear to me what laws should hold for them. Cheers -- Ben Franksen () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] Why Kleisli composition is not in the Monad signature?
Dan Doel wrote: On Tue, Oct 16, 2012 at 10:37 AM, AUGER Cédric sedri...@gmail.com wrote: join IS the most important from the categorical point of view. In a way it is natural to define 'bind' from 'join', but in Haskell, it is not always possible (see the Monad/Functor problem). As I said, from the mathematical point of view, join (often noted μ in category theory) is the (natural) transformation which with return (η that I may have erroneously written ε in some previous mail) defines a monad (and requires some additionnal law). This is the way it's typically presented. Can you demonstrate that it is the most important presentation? I'd urge caution in doing so, too. For instance, there is a paper, Monads Need Not Be Endofunctors, that describes a generalization of monads to monads relative to another functor. And there, bind is necessarily primary, because join isn't even well typed. I don't think it's written by mathematicians per se (rather, computer scientists/type theorists). But mathematicians have their own particular interests that affect the way they frame things, and that doesn't mean those ways are better for everyone. Right. Mathematical /conventions/ can and should be questioned. Sometimes they are not appropriate to the application domain. Sometimes the conventions are just stupid or obsolete even in a purely mathematical context (a well-known example is the extra syntax sugar for binomial coefficients, but there are worse ones), and you still find them in modern text books. Talk about backwards compatibility... My preference for Kleisli composition is because it makes the monad laws so much easier to write down and understand. Everywhere it is said that = must be associative and then the laws are written down for = and return and it is very hard to see what this lambda grave has to do with associativity or units. When I started with Haskell, this was all I could find. It was years later that I stumbled over a text that explained it with = and suddenly it all became simple and clear and I finally understood the monad laws! So, maybe = is the better primitive operation w.r.t. implementation, but IMO = is *much* more efficient w.r.t. understanding the monad laws. Since it is natural to explain the laws of a class using only class methods, I would prefer if = was added to the class with default implementations for = in terms of = and vice versa, so that you can still use = as the primitive operation when implementing an instance. Cheers -- Ben Franksen () ascii ribbon campaign - against html e-mail /\ www.asciiribbon.org - against proprietary attachments ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
Re: [Haskell-cafe] delete http://www.haskell.org/haskellwiki/Haskell_IDE
On 29 November 2012 01:08, Roman Beslik rabes...@gmail.com wrote: Hi. There is more verbose page http://www.haskell.org/haskellwiki/IDEs . I registered on http://www.haskell.org/haskellwiki/ , but have not found the Delete Page command, wiki software help pages, or feedback channel, so I'm writing here. I think the right thing to do is replace the page contents with: #REDIRECT [[IDEs]] Conrad. ___ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
[Haskell-cafe] Haskell Weekly News: Issue 252
Welcome to issue 252 of the HWN, an issue covering crowd-sourced bits of information about Haskell from around the web. This issue covers the week of November 18 to 24, 2012. Quotes of the Week * rwbarton: edwardk now has Lens under Control * atriq: My son looks a bit like me, he can put away the plates after dinner now thanks to edwardk! * mgsloan: Lens got 99 operators, but a (|) ain't one. * hiptobecubic: I feel like this program is just a bunch of glue and duct tape holding a bottle of nitroglycerine off of the ground. * xplat: Some software is worth trying; most is just plain trying. * edwardk: Control.Lens is my secret ploy to get everyone to give up on Haskell and just move on to Agda as they find the Haskell types too complicated by comparison. * rwbarton: alpha reduction is what happens when you let edwardk maintain your module * edwardk: er that was a tongue sticking out, not an operator suggestion Top Reddit Stories * [Haskell] Leaving Microsoft Domain: haskell.org, Score: 139, Comments: 24 On Reddit: [1] http://goo.gl/DnzZF Original: [2] http://goo.gl/eVcXi * Help Nikki (Game written in Haskell) jump on Steam! Domain: joyridelabs.de, Score: 77, Comments: 8 On Reddit: [3] http://goo.gl/EzLh8 Original: [4] http://goo.gl/H84Nl * Gaussian distributions are monoids Domain: izbicki.me, Score: 46, Comments: 24 On Reddit: [5] http://goo.gl/i4keo Original: [6] http://goo.gl/C0gnN * Getting Started with Lenses Domain: newartisans.com, Score: 42, Comments: 32 On Reddit: [7] http://goo.gl/nv4ab Original: [8] http://goo.gl/h2zCa * Designing the Haskell IDE Domain: fpcomplete.com, Score: 41, Comments: 112 On Reddit: [9] http://goo.gl/yz1Rf Original: [10] http://goo.gl/gpJd7 * Putting haskell down Domain: b7j0c.org, Score: 33, Comments: 279 On Reddit: [11] http://goo.gl/8JWmr Original: [12] http://goo.gl/tZcbj * London Haskell Video (24-Oct-2012) – Why Do Monads Matter? Domain: youtube.com, Score: 33, Comments: 5 On Reddit: [13] http://goo.gl/uWH6w Original: [14] http://goo.gl/KqDji * Combinatorial species definition (Brent Yorgey) Domain: byorgey.wordpress.com, Score: 31, Comments: On Reddit: [15] http://goo.gl/0llrA Original: [16] http://goo.gl/PWIep * PhD Positions in Functional Programming at Chalmers (appl. deadline 2012-12-12) Domain: chalmers.se, Score: 28, Comments: On Reddit: [17] http://goo.gl/WAmYP Original: [18] http://goo.gl/JenYO * Video of the presentations at the first NYC Haskell User's Group meetup. Domain: vimeo.com, Score: 25, Comments: 10 On Reddit: [19] http://goo.gl/rxN75 Original: [20] http://goo.gl/uV4wc Top StackOverflow Questions * Where to start with dependent type programming? votes: 16, answers: 1 Read on SO: [21] http://goo.gl/HXdOu * What other ways can state be handled in a pure functional language besides with Monads? votes: 13, answers: 3 Read on SO: [22] http://goo.gl/D86hV * Why are some Prelude functions defined in terms of foldl? votes: 8, answers: 3 Read on SO: [23] http://goo.gl/wewrb * cabal FFI dependency votes: 8, answers: 1 Read on SO: [24] http://goo.gl/JFtJM * How to write Ctrl-C handler in Haskell? votes: 7, answers: 1 Read on SO: [25] http://goo.gl/pS651 * Why does the 2-tuple Functor instance only apply the function to the second element? votes: 5, answers: 2 Read on SO: [26] http://goo.gl/qGgSv * Type Families with GHC.Generics or Data.Data votes: 5, answers: 0 Read on SO: [27] http://goo.gl/mERdP * Haskell Programmatically/Dynamically Define Functions votes: 5, answers: 6 Read on SO: [28] http://goo.gl/22Wf0 * is this implementation of merge sort good? votes: 5, answers: 1 Read on SO: [29] http://goo.gl/Skznl * Railroad diagrams for Haskell? votes: 5, answers: 1 Read on SO: [30] http://goo.gl/ZeJa9 * Is FRP a proper way to implement most “event-driven” things? votes: 5, answers: 1 Read on SO: [31] http://goo.gl/QglPp * Stack overflow in very simple code votes: 5, answers: 1 Read on SO: [32] http://goo.gl/wB0kg * Mapping over Either's Left votes: 5, answers: 3 Read on SO: [33] http://goo.gl/oJX4v * Haskell - strict vs non-strict with foldl votes: 5, answers: 2 Read on SO: [34] http://goo.gl/3ElzK Until next time, Daniel Santa Cruz References 1. http://www.haskell.org/pipermail/haskell/2012-November/023566.html 2. http://www.reddit.com/r/haskell/comments/13m8eu/haskell_leaving_microsoft/ 3. http://joyridelabs.de/blog/?p=1548 4. http://www.reddit.com/r/haskell/comments/13muex/help_nikki_game_written_in_haskell_jump_on_steam/ 5. http://izbicki.me/blog/gausian-distributions-are-monoids
