April 2011 - Libraries

Filemanip on Windows
by Dominic Steinitz 06 Apr '11

06 Apr '11

I tried to install filemanip on a windows system but it failed at the build stage: C:\temp\filemanip-0.3.5.2>runghc Setup.lhs build Preprocessing library filemanip-0.3.5.2... Building filemanip-0.3.5.2... System\FilePath\Manip.hs:25:7: Could not find module `System.Posix.Temp': Use -v to see a list of the files searched for. It seems that Manip.hs depends on System.Posix.Temp but the cabal file says it doesn't on windows: if !os(windows) build-depends: unix I amended Manip.hs to work on windows and I am pretty sure it will still work on unix. I've attached the amended source (I would have attached a patch but I'm not familiar with the source control system you are using). I also noticed that someone else had submitted a patch for windows support: https://bitbucket.org/bos/filemanip/issue/1/patch-for-windows-support. Did this every get incorporated? For some reason I wasn't able to look at it but it may be better than my patch. Dominic. {-# LANGUAGE FlexibleInstances, ScopedTypeVariables, TypeSynonymInstances #-} -- | -- Module: System.FilePath.Manip -- Copyright: Bryan O'Sullivan -- License: BSD3 -- Maintainer: Bryan O'Sullivan <bos(a)serpentine.com> -- Stability: unstable -- Portability: Unix-like systems (requires flexible instances) module System.FilePath.Manip ( Streamable(..) , renameWith , modifyWith , modifyWithBackup , modifyInPlace ) where import Control.Exception import Control.Monad (liftM) import Data.Bits ((.&.)) import System.Directory (removeFile, getTemporaryDirectory) import System.IO (Handle, IOMode(..), hClose, openFile, openTempFile) import System.PosixCompat.Files (fileMode, getFileStatus, rename, setFileMode) import qualified Data.ByteString.Char8 as B import qualified Data.ByteString.Lazy.Char8 as L import qualified System.IO as I -- | Use a renaming function to generate a new name for a file, then -- rename it. renameWith :: (FilePath -> FilePath) -- ^ function to rename with -> FilePath -- ^ file to rename -> IO () renameWith f path = rename path (f path) -- | Type class for string manipulation over files. class Streamable a where -- | Read the entire contents of a 'Handle'. readAll :: Handle -> IO a -- | Write an entire string to a 'Handle'. writeAll :: Handle -> a -> IO () instance Streamable B.ByteString where readAll = B.hGetContents writeAll = B.hPut instance Streamable L.ByteString where readAll = L.hGetContents writeAll = L.hPut instance Streamable String where readAll = I.hGetContents writeAll = I.hPutStr -- | Modify a file in place using the given function. This is -- performed by writing to a temporary file, then renaming it on top of -- the existing file when done. modifyInPlace :: Streamable a => (a -> a) -- ^ transformation function -> FilePath -- ^ name of file to modify -> IO () modifyInPlace = modifyWith (flip rename) -- | Modify a file in place using the given function. The original -- copy of the file is saved under a new name. This is performed by -- writing to a temporary file; renaming the original file to its new -- name; then renaming the temporary file to the original name. -- -- Example: -- -- @ -- -- save original file with a \".bak\" extension -- 'modifyWithBackup' (\<.\> \"bak\") -- @ modifyWithBackup :: Streamable a => (FilePath -> FilePath) -- ^ chooses new name for original file -> (a -> a) -- ^ transformation function -> FilePath -- ^ name of file to modify -> IO () modifyWithBackup f = modifyWith backup where backup path tmpPath = renameWith f path >> rename tmpPath path -- | Modify a file in place using the given function. The new content -- is written to a temporary file. Once this is complete, the file -- manipulation action is called. Its arguments are the names of the -- original and temporary files. -- -- Example: -- -- @ -- 'modifyInPlace' = 'modifyWith' (flip rename) -- @ modifyWith :: Streamable a => (FilePath -> FilePath -> IO ()) -- ^ file manipulation action -> (a -> a) -- ^ transformation function -> FilePath -> IO () modifyWith after transform path = bracket (openFile path ReadMode) hClose $ \ih -> do tmpDir <- getTemporaryDirectory (tmpPath, oh) <- openTempFile tmpDir "XXX.XXX" let ignore = return () nukeTmp = handle (\(_::IOException) -> ignore) (removeFile tmpPath) handle (\(e::IOException) -> nukeTmp >> throw e) $ do bracket_ ignore (hClose oh) $ readAll ih >>= return . transform >>= writeAll oh handle (\(_::IOException) -> nukeTmp) $ do mode <- fileMode `liftM` getFileStatus path setFileMode tmpPath (mode .&. 0777) after path tmpPath

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Conversion to git
by Ian Lynagh 06 Apr '11

06 Apr '11

Hi all, The latest GHC git conversion plan is to convert GHC and all associated repos to git on: *** Tuesday, March the 15th *** In some cases this will mean simply converting the master repos, while in others it'll mean setting up git (lagging) mirrors for the GHC build to use. We've made a list of which repos we suggest should be converted, and which should be mirrored, here: http://hackage.haskell.org/trac/ghc/wiki/DarcsConversion#Planforlibraries Can you please let us know if you think any of the repos have been put in the wrong category? Thanks Ian

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Data.HashTable performance
by Frank Kuehnel 06 Apr '11

06 Apr '11

Out of curiosity, I've tested a few Hashtable implementations: http://zufaellige-reflektion.blogspot.com/2011/04/associative-arrays-showdo… Are there any clues why Haskell's Data.HashTable doesn't perform better? I would have expected a similar performance like with F# on the Mono 2.0 platform. Thanks, Frank

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ANN: stm-chans: Additional types of channels for STM.
by wren ng thornton 06 Apr '11

06 Apr '11

-------------------------------------------- -- stm-chans 1.0.0 -------------------------------------------- The stm-chans package offers a collection of channel types, similar to Control.Concurrent.STM.TChan but with additional features. In particular it offers these types: * Control.Concurrent.STM.TBChan: Bounded FIFO channels. When the channel is full, writers will block/retry. This ensures that the writers do not get too far ahead of the readers, which helps to make sure that memory and cpu resources are used responsibly. * Control.Concurrent.STM.TMChan: Closeable FIFO channels. This is like TChan (Maybe a) but with a monotonicity guarantee that once Nothing is returned all future reads will be Nothing as well. * Control.Concurrent.STM.TBMChan: Bounded Closeable FIFO channels. This combines the capabilities of TBChan and TMChan. In addition, the stm-chans package offers a (partial) compatibility layer for some API improvements still making their way into the stm package[1]. These new functions include: * tryReadTChan :: TChan a -> STM (Maybe a) A version of readTChan which does not retry. Instead it returns Nothing if no value is available. * peekTChan :: TChan a -> STM a Get the next value from the TChan without removing it, retrying if the channel is empty. * tryPeekTChan :: TChan a -> STM (Maybe a) A version of peekTChan which does not retry. Instead it returns Nothing if no value is available. [1] http://article.gmane.org/gmane.comp.lang.haskell.libraries/15507 -------------------------------------------- -- Links -------------------------------------------- Homepage: http://code.haskell.org/~wren/ Hackage: http://hackage.haskell.org/package/stm-chans Darcs: http://community.haskell.org/~wren/stm-chans Haddock (Darcs version): http://community.haskell.org/~wren/stm-chans/dist/doc/html/stm-chans -- Live well, ~wren

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Show instance in System.Event.Manager causes conflicts
by Conal Elliott 04 Apr '11

04 Apr '11

System.Event.Manager [1] contains the following type alias and Show instance: -- | Callback invoked on I/O events. type IOCallback = FdKey -> Event -> IO () instance Show IOCallback where show _ = "IOCallback" This specialized instance conflicts with the more general instance Show (a -> b) defined in Text.Show.Functions. Stefan found this conflict when trying to compile the checkers package on ghc 7.0.3. I suspect it will arise with other packages as well. My suggestion is to remove the specialized Show instance and instead import Text.Show.Functions as needed. Other thoughts? [1] http://hackage.haskell.org/packages/archive/base/4.3.1.0/doc/html/src/Syste… - Conal

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The System Event Manager
by Bas van Dijk 04 Apr '11

04 Apr '11

Hello, When you want to use the system event manager (the one started by the RTS) you currently have to do something like this: ----------------------------------------------------------------------- {-# LANGUAGE ForeignFunctionInterface #-} import System.Event (EventManager) import GHC.Conc.Sync (sharedCAF) import Foreign.Ptr (Ptr) import Data.IORef (IORef, newIORef, readIORef) import System.IO.Unsafe (unsafePerformIO) main = do Just mgr <- readIORef eventManager ... eventManager :: IORef (Maybe EventManager) eventManager = unsafePerformIO $ do em <- newIORef Nothing sharedCAF em getOrSetSystemEventThreadEventManagerStore {-# NOINLINE eventManager #-} foreign import ccall unsafe "getOrSetSystemEventThreadEventManagerStore" getOrSetSystemEventThreadEventManagerStore :: Ptr a -> IO (Ptr a) ----------------------------------------------------------------------- What about abstracting this ugliness in a function: getSystemEventManager :: IO EventManager getSystemEventManager = do Just mgr <- readIORef eventManager return mgr I'm not entirely comfortable about the partial pattern match. I guess it fails when the program is linked with the non-threaded RTS. Can we use #ifdef THREADED_RTS here? I'm also not sure from which module to export this function. The attached patch defines it in and exports it from System.Event.Thread. It also exports it from the public System.Event. However maybe it's better to export it from GHC.Conc instead. What do you think? Regards, Bas

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[commit: base] master: Document invariants on mkText{Decoder, Encoder} (54a0b49)
by Max Bolingbroke 04 Apr '11

04 Apr '11

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base On branch : master http://hackage.haskell.org/trac/ghc/changeset/54a0b4928967a350be687e17ff357… >--------------------------------------------------------------- commit 54a0b4928967a350be687e17ff3576f2af6e21fb Author: Max Bolingbroke <batterseapower(a)hotmail.com> Date: Mon Apr 4 14:45:13 2011 +0100 Document invariants on mkText{Decoder,Encoder} >--------------------------------------------------------------- GHC/IO/Encoding/Types.hs | 8 ++++++-- 1 files changed, 6 insertions(+), 2 deletions(-) diff --git a/GHC/IO/Encoding/Types.hs b/GHC/IO/Encoding/Types.hs index caffa24..ac9147a 100644 --- a/GHC/IO/Encoding/Types.hs +++ b/GHC/IO/Encoding/Types.hs @@ -90,8 +90,12 @@ data TextEncoding textEncodingName :: String, -- ^ a string that can be passed to 'mkTextEncoding' to -- create an equivalent 'TextEncoding'. - mkTextDecoder :: IO (TextDecoder dstate), - mkTextEncoder :: IO (TextEncoder estate) + mkTextDecoder :: IO (TextDecoder dstate), + -- ^ Creates a means of decoding bytes into characters: the result must not + -- be shared between several byte sequences or simultaneously across threads + mkTextEncoder :: IO (TextEncoder estate) + -- ^ Creates a means of encode characters into bytes: the result must not + -- be shared between several character sequences or simultaneously across threads } instance Show TextEncoding where

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[commit: directory] master: add notes about the non-thread-localness of the current directory (#4082) (d84494e)
by Simon Marlow 04 Apr '11

04 Apr '11

Repository : ssh://darcs.haskell.org//srv/darcs/packages/directory On branch : master http://hackage.haskell.org/trac/ghc/changeset/d84494e2bc50fd97d78681cbfa119… >--------------------------------------------------------------- commit d84494e2bc50fd97d78681cbfa11961b7903b93c Author: Simon Marlow <marlowsd(a)gmail.com> Date: Mon Apr 4 08:52:00 2011 +0100 add notes about the non-thread-localness of the current directory (#4082) >--------------------------------------------------------------- System/Directory.hs | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/System/Directory.hs b/System/Directory.hs index d264583..6c28eef 100644 --- a/System/Directory.hs +++ b/System/Directory.hs @@ -862,6 +862,11 @@ Insufficient resources are available to perform the operation. * 'UnsupportedOperation' The operating system has no notion of current directory. +Note that in a concurrent program, the current directory is global +state shared between all threads of the process. When using +filesystem operations from multiple threads, it is therefore highly +recommended to use absolute rather than relative `FilePath`s. + -} #ifdef __GLASGOW_HASKELL__ getCurrentDirectory :: IO FilePath @@ -902,6 +907,11 @@ current directory cannot be dynamically changed. The path refers to an existing non-directory object. @[ENOTDIR]@ +Note that in a concurrent program, the current directory is global +state shared between all threads of the process. When using +filesystem operations from multiple threads, it is therefore highly +recommended to use absolute rather than relative `FilePath`s. + -} setCurrentDirectory :: FilePath -> IO ()

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[commit: base] encoding: Implement surrogate-byte error handling mode for TextEncoding (e60a79b)
by Max Bolingbroke 04 Apr '11

04 Apr '11

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base On branch : encoding http://hackage.haskell.org/trac/ghc/changeset/e60a79b8e093c4b5748642867eaa2… >--------------------------------------------------------------- commit e60a79b8e093c4b5748642867eaa24fbd7781639 Author: Max Bolingbroke <batterseapower(a)hotmail.com> Date: Mon Apr 4 11:29:21 2011 +0100 Implement surrogate-byte error handling mode for TextEncoding This implements PEP383-like behaviour so that we are able to roundtrip byte strings through Strings without loss of information. GHC/IO/Encoding.hs | 1 + GHC/IO/Encoding/CodePage.hs | 20 +++++--- GHC/IO/Encoding/Failure.hs | 66 ++++++++++++++++++++++++ GHC/IO/Encoding/Iconv.hs | 52 ++++++++++++++---- GHC/IO/Encoding/Latin1.hs | 14 +++-- GHC/IO/Encoding/Types.hs | 29 +---------- GHC/IO/Encoding/UTF16.hs | 107 ++++++++++++++++++++++++++------------- GHC/IO/Encoding/UTF32.hs | 119 ++++++++++++++++++++++++++++--------------- GHC/IO/Encoding/UTF8.hs | 66 ++++++++++++++---------- base.cabal | 1 + 10 files changed, 320 insertions(+), 155 deletions(-) Diff suppressed because of size. To see it, use: git show e60a79b8e093c4b5748642867eaa24fbd7781639

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[commit: base] encoding: Implement coding failure modes: ignore, throw error, transliterate (239d24c)
by Max Bolingbroke 04 Apr '11

04 Apr '11

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base On branch : encoding http://hackage.haskell.org/trac/ghc/changeset/239d24cd0401c659f4aac65fe4715… >--------------------------------------------------------------- commit 239d24cd0401c659f4aac65fe47156b890e44571 Author: Max Bolingbroke <batterseapower(a)hotmail.com> Date: Mon Apr 4 09:18:11 2011 +0100 Implement coding failure modes: ignore, throw error, transliterate GHC/IO/Encoding.hs | 43 ++++++++---- GHC/IO/Encoding/CodePage.hs | 80 ++++++++++++++-------- GHC/IO/Encoding/Iconv.hs | 153 +++++++++++++++++++++++++------------------ GHC/IO/Encoding/Latin1.hs | 46 +++++++++---- GHC/IO/Encoding/Types.hs | 27 ++++++++ GHC/IO/Encoding/UTF16.hs | 104 ++++++++++++++++++++--------- GHC/IO/Encoding/UTF32.hs | 104 ++++++++++++++++++++--------- GHC/IO/Encoding/UTF8.hs | 75 +++++++++++++--------- 8 files changed, 414 insertions(+), 218 deletions(-) Diff suppressed because of size. To see it, use: git show 239d24cd0401c659f4aac65fe47156b890e44571

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