March 2010 - Haskell-Cafe

Takusen sqlite3 insert is very slow
by Vasyl Pasternak 26 Mar '10

26 Mar '10

Hi Cafe, I have another problem, please look at code: storeInDb = withSession (connect "test.db") (do execDDL (sql "create table x (y int)") forM_ ([1..10000] :: [Int]) (\x -> do execDML (cmdbind ("insert into x (y) values (?);") [bindP x]) return ())) This code runs 16 seconds which is very slow for this simple task. RTS output is below. After profiling this program I found that 85% of its time it spends in 'Database.Sqlite.SqliteFunctions.stmtFetch'. Currently I don't know how to make it faster, maybe anyone had this problem later? HDBC inserts very fast, so this is not sqlite error. RTS output: 156,195,264 bytes allocated in the heap 591,280 bytes copied during GC 3,952 bytes maximum residency (1 sample(s)) 10,968 bytes maximum slop 1 MB total memory in use (0 MB lost due to fragmentation) Generation 0: 295 collections, 0 parallel, 0.00s, 0.01s elapsed Generation 1: 1 collections, 0 parallel, 0.00s, 0.02s elapsed INIT time 0.00s ( 0.03s elapsed) MUT time 0.87s ( 16.09s elapsed) GC time 0.00s ( 0.02s elapsed) RP time 0.00s ( 0.00s elapsed) PROF time 0.00s ( 0.00s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 0.88s ( 16.14s elapsed) %GC time 0.5% (0.1% elapsed) Alloc rate 179,111,917 bytes per MUT second Productivity 99.5% of total user, 5.4% of total elapsed Regards, Vasyl

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Windows version of Haskell Platform containing ghc 6.12
by Han Joosten 26 Mar '10

26 Mar '10

Last weekend a new version of the haskell platform has been released. I was expecting that also for windows the ghc 6.12 would be in it. However, when I follow the link: http://hackage.haskell.org/platform/windows.html I still get the 'old' version (2009.2.0.2) which contains ghc 6.10 Is this intentional? If so, is there anything to say when a windows version of the platform will become available that contains ghc 6.12? Thanks! Han -- View this message in context: http://old.nabble.com/Windows-version-of-Haskell-Platform-containing-ghc-6.… Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.

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sendfile leaking descriptors on Linux?
by Bardur Arantsson 25 Mar '10

25 Mar '10

Hi all, I've been using the sendfile package off Hackage, but it seems to be leaking file descriptors when using the Linux-native build. What's happening in my specific case is the following: 1) client requests a range of a file 2) server starts sending the range 3) client disconnects before receiving the whole file This happens over and over with the client requesting different ranges of the file (so the client does make progress). If I use the portable build of the sendfile package, everything works fine for hours and hours of this happening. If I use the Linux-native build of the sendfile package, the server will eventually run out of file descriptors. According to "lsof" the files that are being kept open are the data files being sent in 2) above. This is on GHC 6.10.x (Ubuntu). Is anyone else seeing this? Anyone got any idea what's going on? Cheers,

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Is hGetLine lazy like hGetContents? And what about this todo item?
by Jason Dagit 25 Mar '10

25 Mar '10

Hello, I was trying to figure out if hGetLine is safe to use inside of withFile. Specifically, I want to return the line I read and use it later, without inspecting it before withFile calls hClose. If you want to understand the concern I have, look here: http://www.haskell.org/haskellwiki/Maintaining_laziness#Input_and_Output There is a bit of explanation showing that hGetContents can be problematic with withFile. I can tell from reading the source of hGetContents that it uses unsafeInterleaveIO so this make sense to me why that wiki page talks about hGetContents: http://www.haskell.org/ghc/docs/latest/html/libraries/base/src/GHC-IO-Handl… When I read the source of hGetLine, it is less clear to me if I need to be concerned. I believe it is not lazy in the sense of lazy IO above. Could someone else please comment? http://www.haskell.org/ghc/docs/latest/html/libraries/base/src/GHC-IO-Handl… Then I notice this 'todo' item in the description: -- ToDo: the unbuffered case is wrong: it doesn't lock the handle for -- the duration. The code itself looks to me like it only handles the buffered case. Perhaps this todo is obsolete and needs to be removed? If it's not obsolete, do we need to create a ticket for this? Thanks, Jason

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HLIst - how to use TIPTransform with functions that run in the IO monad?
by Andrew U. Frank 25 Mar '10

25 Mar '10

i use the TIPTransform module that Oleg has provided - very nice and easy to use! Thank you Oleg!! now i run into a problem, i seem not to be able to resolve: how to use TIPTransform with functions that use the IO monad? considering the example tip5 in Olegs communiation, where he uses a function with three arguments from the TIP (HList) and producing a result in the HList. i would like to use a similar functionality, getting the arguments from the HList and producing a result which is again stored in the HList - but the function has a signature like f :: Int -> String -> IO String. the resulting string should go int the HList. i assume i need a function like ttip: ttipM :: op -> db -> IO db? can somebody help me with this? i appreciate any help! andrew

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ANNOUNCE: cuboid 0.12: 3D Yampa/GLUT Puzzle Game
by Pedro Martins 25 Mar '10

25 Mar '10

Hi all, Recently, I have been playing around a bit with Yampa and GLUT, integrating them and trying to develop a simple 3D game within the framework. As it involved quite a bit of source code reading from Yampa and Frag (thanks to both!), I have decided to upload the game to Hackage, to help other people interested in using AFRP for game development. Overall, the experience of using Yampa was very pleasing, as it allowed me to describe the logic of the game in a more declarative fashion than usual. However, because there aren't many tutorials/examples on using Yampa for games, it involved a fair amount of experimentation and so my code might not be very idiomatic for Yampa. Please tell me if so and I'll fix it so this can be a good example. For playing instructions, see the Hackage description [1]. It currently only has 3 hardcoded easy levels, but the level definition is a simple Haskell ADT definition (Game.hs), and I plan on placing it in a separate data file in the future. This is my first upload to Hackage, so any comments or suggestions are welcome. Thanks, Pedro [1] http://hackage.haskell.org/package/cuboid

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existentially quantified data types - restrictions
by Ozgur Akgun 25 Mar '10

25 Mar '10

Dear Cafe, I need to use a language feature which is explicitly documented to be a restriction, and -even worse- I think I reasonably need to use it. f2 (Baz1 a b) (Baz1 p q) = a==q > It's ok to say a==b or p==q, but a==q is wrong because it equates the two > distinct types arising from the two Baz1 constructors. > [from *7.4.4.4. Restrictions* at > http://www.haskell.org/ghc/docs/latest/html/users_guide/data-type-extension… > ] > To simplify, let's say Baz is the only constructor of a data type, data Baz = forall a. Eq a => Baz a -- | this cannot be done: instance Eq (Baz a) where (Baz x) == (Baz y) = x == y I am quite tempted to use show functions for this equality comparison, but after trying to have a nicely type framework I really don't want to do that. What I simply want is, haskell to be able to compare them if they belong to the same type, and return False otherwise. (not that haskelly way of doing things, I know.) Any suggestions better than the following are very welcome: (==) = (==) `on` show Regards, -- Ozgur Akgun

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double existential type
by Ozgur Akgun 25 Mar '10

25 Mar '10

Hello all, I have a syntax issue (hopefully!) -- this is perfectly fine: data Unary = forall a. Unary a -- this one as well: data Binary = forall a. Binary a a -- but not this one -- parse error on input forall :( data Binary' = forall a. forall b. Binary' a b I tried different kinds of bracketings and orderings but no luck... Best, -- Ozgur Akgun

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Re: [Haskell-cafe] phonetic dictionnary
by Dupont Corentin 25 Mar '10

25 Mar '10

Thanks, this dictionnary is exactly what i wanted! Too bad it doesn't exists in French! On 3/25/10, Max Rabkin <max.rabkin(a)gmail.com> wrote: > There is the CMU phonetic dictionary for English at > http://www.speech.cs.cmu.edu/cgi-bin/cmudict but I know of nothing for > French. Perhaps there is an open-source text-to-speech engine that has > a free French pronouncing dictionary. > > --Max > > On Thu, Mar 25, 2010 at 2:59 PM, Dupont Corentin > <corentin.dupont(a)gmail.com> wrote: >> Hello, >> sorry if i ask a lot of questions these days! >> Do you know of a phonetic dictionnary? >> >> i'm very fond of enigmas. To solve certain enigmas, i've made a little >> program that search into a french dictionnary. >> But it would be much better if i could search into a phonetic >> dictionnary... >> The goal is to answer questions like "Wich word would rhyme with >> aligator?" >> >> Corentin >> _______________________________________________ >> Haskell-Cafe mailing list >> Haskell-Cafe(a)haskell.org >> http://www.haskell.org/mailman/listinfo/haskell-cafe >> >

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Re: [Haskell] ANN: Yi 0.6.2.2
by Jeff Wheeler 25 Mar '10

25 Mar '10

On Thu, Mar 25, 2010 at 7:48 AM, John Lato <jwlato(a)gmail.com> wrote: > Will it work if you set data-accessor-template < 0.2.1.3 in the .cabal > file? I think that version is acceptable to both ghc-6.10 and 6.12. It seems so, yes. Unfortunately, I've already made other changes to HEAD that are incompatible with 6.10. -- Jeff Wheeler Undergraduate, Electrical Engineering University of Illinois at Urbana-Champaign

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