January 2008 - Libraries

There are too many error handling conventions used in library code!
by dons＠cse.unsw.edu.au 13 Aug '11

13 Aug '11

This article on the 8 different error handling strategies various common Haskell libs use: http://www.randomhacks.net/articles/2007/03/10/haskell-8-ways-to-report-err… got me thinking: we need to standardise/recommend a small set of methods for library error handling. The lack of consistent error reporting between libs results in verbose code, as we're not able to use a single error handling technique when gluing together code from different libs (i.e. we can't just use Maybe or Either/ErrorT). (It's always nice when you *can* use, say, a Maybe monad to glue code from a number of sources, but eventually you reach code with a different error system, and the Maybe monad breaks down). So, some questions I think we can tackle: * can we identify error handling strategies from the list that should not be used anymore? (throwDyn?) * can we move some of the outlying libraries to a more consistent error framework? * do we need more support for gluing together our different error systems? (it should be easier to glue code using , say, Maybe/Either). * what role does MonadError play here, as a generic error handler? * can we make precise recommendations about which error strategies to use? -- Don

11 16

Arrow without `>>>'
by Valery V. Vorotyntsev 03 Sep '08

03 Sep '08

Hi, friends, I've built GHC from darcs, and... Could anybody tell me, what's the purpose of Arrow[1] not having `>>>' method? 1. http://darcs.haskell.org/packages/base/Control/Arrow.hs $ ghci GHCi, version 6.9.20080104: http://www.haskell.org/ghc/ :? for help Loading package base ... linking ... done. Prelude> :m + Control.Arrow Prelude Control.Arrow> :i Arrow class (Control.Category.Category a) => Arrow a where arr :: (b -> c) -> a b c pure :: (b -> c) -> a b c first :: a b c -> a (b, d) (c, d) second :: a b c -> a (d, b) (d, c) (***) :: a b c -> a b' c' -> a (b, b') (c, c') (&&&) :: a b c -> a b c' -> a b (c, c') -- Defined in Control.Arrow instance Arrow (->) -- Defined in Control.Arrow instance (Monad m) => Arrow (Kleisli m) -- Defined in Control.Arrow Prelude Control.Arrow> Leaving GHCi. I can't build[2] arrows-0.3 package without `>>>' in Arrow. 2. vvv@fun:~/src/arrows$ darcs w { hunk ./Control/Arrow/Operations.hs 36 +import Control.Category ((>>>)) hunk ./Control/Arrow/Transformer/CoState.hs 23 +import Control.Category ((>>>)) } vvv@fun:~/src/arrows$ runhaskell Setup build Preprocessing library arrows-0.3... Building arrows-0.3... [ 3 of 12] Compiling Control.Arrow.Transformer.CoState ( Control/Arrow/Transformer/CoState.hs, dist/build/Control/Arrow/Transformer/CoState.o ) Control/Arrow/Transformer/CoState.hs:29:7: `>>>' is not a (visible) method of class `Arrow' The question arises "should I?", but this is one of lambdabot's[3] depencies. 3. http://code.haskell.org/lambdabot/ Thanks a lot! -- vvv

4 5

QuickCheck properties for IntSet
by David Benbennick 01 May '08

01 May '08

Here's a patch to IntSet.hs that adds many QuickCheck properties. It adds properties testing almost all of the public interface of IntSet, and also properties testing that the data type invariants are never broken. (The patch doesn't test the Data, Eq, Monoid, Read, or Typeable instances.) Also, this patch removes a helper function, foldlStrict, and replaces it with calls to Data.List.foldl'. I have two questions: 1) Is this the right way to submit patches? 2) Is there a good reason that IntSet doesn't use "deriving Eq", and instead manually implements the Eq instance?

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Libraries need a new owner
by Adrian Hey 27 Mar '08

27 Mar '08

Hello Folks, As some of you will be aware, I have been working on various Map implementations that currently live here.. http://code.haskell.org/collections/collections-ghc6.8 The libs in question being Data.Tree.AVL, Data.Trie.General and a few other bits like Data.COrdering and the AVL based Data.Map/Set clones. Well, I have decided to stop work on these. So they need a new owner if they're going to go anywhere. If anyone is interested in the job then I suggest they contact myself or Jean-Philippe Bernardy. Of course I will be happy to provide any help or advise anyone who takes over these libs may feel they need from me. I might even contribute a few patches from time to time myself :-) Thanks -- Adrian Hey

4 12

Data.Map, Data.IntMap documentation
by Andriy Palamarchuk 19 Mar '08

19 Mar '08

Improved, fixed documentation for Data.Map, Data.IntMap. Moved time complexity Big-O values to the end of function descriptions. Added examples. For the initial review I submitted only changes for Data.Map. I'll update IntMap for the final review. Deadline - August 27 (two weeks). Ticket: http://hackage.haskell.org/trac/ghc/ticket/1611 Haddock output: http://hackage.haskell.org/trac/ghc/attachment/ticket/1611/Data-Map.html?fo… The module source and diff are also attached to the ticket. Andriy ____________________________________________________________________________________ Pinpoint customers who are looking for what you sell. http://searchmarketing.yahoo.com/

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Readline read_history and write_history addition
by Alexander Dunlap 20 Feb '08

20 Feb '08

Hello all, I'd like to propose the addition of read_history and write_history bindings to the readline library. I believe I've followed the instructions on the Haskell wiki appropriately and I've set up a ticket (with a patch) at http://hackage.haskell.org/trac/ghc/ticket/2053. Essentially, the patch adds simple bindings so that Haskell programs can use Readline's read_history and write_history functions. This will be useful for the implementation of http://hackage.haskell.org/trac/ghc/ticket/2050 (add persistent history to GHCi) and potentially other applications. Thanks for your time and consideration. Alex

11 39

HSQL defunct?
by Frederik Eaton 18 Feb '08

18 Feb '08

Hello all, Is there going to be a new maintainer for HSQL? I have submitted a number of patches to fix some painful bugs. It's been almost a year since my previous enquiry and the last release was December 15, 2005, over two years ago: https://sourceforge.net/project/showfiles.php?group_id=65248 The software no longer compiles with the latest version of GHC, due to some (seemingly gratuitous) changes in the Cabal libraries (I see there is a September 2007 thread on libraries@). Unfortunately, I am too busy to maintain it myself; I was probably even too busy to write the patches in the first place, but it is sad to see them go to waste... Frederik P.S. Quan Ta: regarding your July 20, 2006 query, "HSQL-MySQL: non-standard port", my first patch adds the ability to specify a non-standard port with the server host name, if you are still interested I can send it. On Sun, Mar 25, 2007 at 06:55:21PM +0200, Björn Bringert wrote: > I found this very old mail in my inbox, sorry for not responding sooner. > Yeah, a new HSQL release would be a good idea, IMO. Krasimir is the > maintainer, so it's really up to him. > > /Björn > > Frederik Eaton wrote: > > Hi Bjorn, > > > > The sourceforge page for HSQL shows a most recent release date of > > December 15, 2005 - over a year ago, presumably not including the > > timezone patch which I think fixes a rather serious bug, which caused > > a lot of problems for me when I tried to use HSQL for my master's > > project. Perhaps it might be helpful to other users if the fix were > > made available to them as well? > > > > Thanks, > > > > Frederik > > > > On Fri, Aug 25, 2006 at 11:20:55AM +0200, Björn Bringert wrote: > >> Sorry for the delay, I've been on vacation. The timezone patch has been > >> committed. I haven't added the Makefile, since I think that some cabal > >> tools that will come with GHC 6.6 could make it obsolete. > >> > >> /Björn > >> > >> Frederik Eaton wrote: > >>> Hi, > >>> > >>> Oops, sorry, there was a bug. Here's a more-tested patch. Stay tuned! > >>> > >>> (if you've already applied the last one, change HSQL.hsc's > >>> > >>> ctMonth = toEnum $ mon, > >>> > >>> to > >>> > >>> ctMonth = toEnum $ (mon-1), > >>> > >>> ) > >>> > >>> Frederik > >>> > >>> On Thu, Aug 17, 2006 at 01:49:40AM +0100, Frederik Eaton wrote: > >>> > >>>> I'm attaching a patch which I've tested. > >>>> > >>>> I'm also attaching a Makefile derived from Bulat's IIRC, it might be > >>>> good to include it in those directories which contain a .cabal file. > >>>> > >>>> Thanks, > >>>> > >>>> Frederik > >>>> > >>>> On Thu, Aug 17, 2006 at 01:17:11AM +0100, Frederik Eaton wrote: > >>>> > >>>>> Hi, in > >>>>> > >>>>> HSQL/Database/HSQL.hsc > >>>>> > >>>>> instance SqlBind ClockTime where > >>>>> ... > >>>>> > >>>>> all of the 'fromSqlValue' functions convert with respect to the local > >>>>> timezone, while 'toSqlValue' converts with respect to UTC. Thus the > >>>>> values being written are not the same, it would seem, as those being > >>>>> read. Certainly that is the case for me. > >>>>> > >>>>> If the three appearances of currTZ within the body of that instance > >>>>> (and not elsewhere) are changed to 0, it should fix the problem (but I > >>>>> haven't tested). > >>>>> > >>>>> Also, I don't understand why a custom function 'mkClockTime' has been > >>>>> written in that module (it calls 'mktime' via FFI), rather than > >>>>> calling the standard library function toClockTime which seems to do > >>>>> the same thing. > >>>>> > >>>>> Frederik > >>>>> > >>>>> On Thu, Aug 10, 2006 at 04:19:36PM +0100, Frederik Eaton wrote: > >>>>> > >>>>>> In HSQL, why are 'datetime' columns interpreted as being in the local > >>>>>> timezone? > >>>>>> > >>>>>> I would think that UTC would be more useful. If the local timezone is > >>>>>> used, then it makes it more difficult to move a server between > >>>>>> timezones, or to have multiple servers in multiple timezones. > >>>>>> > >>>>>> Frederik > >>>>>> > >>>>>> On Sat, Aug 05, 2006 at 06:59:21PM +0100, Frederik Eaton wrote: > >>>>>> > >>>>>>> Thanks! > >>>>>>> > >>>>>>> On Sat, Aug 05, 2006 at 05:27:04PM +0200, Bjorn Bringert wrote: > >>>>>>> > >>>>>>>> On Aug 5, 2006, at 3:34 PM, Frederik Eaton wrote: > >>>>>>>> > >>>>>>>> > >>>>>>>>> On Sat, Aug 05, 2006 at 11:15:19AM +0200, Bjorn Bringert wrote: > >>>>>>>>> > >>>>>>>>>> On Jul 31, 2006, at 12:55 PM, Frederik Eaton wrote: > >>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>>> Hi, > >>>>>>>>>>> > >>>>>>>>>>> I'm attaching another HSQL patch. > >>>>>>>>>>> > >>>>>>>>>>> It allows users to specify a port number with the server name in the > >>>>>>>>>>> MySQL client. > >>>>>>>>>>> > >>>>>>>>>>> Frederik > >>>>>>>>>> Hi Frederik, > >>>>>>>>>> > >>>>>>>>>> the patch doesn't apply cleanly against the current CVS version. Is > >>>>>>>>>> there any chance you could make a patch against the CVS version > >>>>>>>>>> instead? > >>>>>>>>> It's a very simple modification, can't you just copy and paste from > >>>>>>>>> the patch? > >>>>>>>> It appears to have been a simple whitespace mismatch problem (tabs in the original HSQL source). I > >>>>>>>> have committed your patch to CVS. > >>>>>>>> > >>>>>>>> Thanks! > >>>>>>>> > >>>>>>>> /Björn > >>>> -- > >>>> http://ofb.net/~frederik/ > >>> > >>>> diff -ur HSQL-1.7-modified/HSQL/Database/HSQL.hsc HSQL-1.7-modified-2/HSQL/Database/HSQL.hsc > >>>> --- HSQL-1.7-modified/HSQL/Database/HSQL.hsc 2005-12-15 20:57:18.000000000 +0000 > >>>> +++ HSQL-1.7-modified-2/HSQL/Database/HSQL.hsc 2006-08-17 01:43:19.000000000 +0100 > >>>> @@ -304,28 +304,17 @@ > >>>> > >>>> toSqlValue d = show d > >>>> > >>>> -mkClockTime :: Int -> Int -> Int -> Int -> Int -> Int -> Int -> ClockTime > >>>> mkClockTime year mon mday hour min sec tz = > >>>> - unsafePerformIO $ do > >>>> - allocaBytes (#const sizeof(struct tm)) $ \ p_tm -> do > >>>> - (#poke struct tm,tm_sec ) p_tm (fromIntegral sec :: CInt) > >>>> - (#poke struct tm,tm_min ) p_tm (fromIntegral min :: CInt) > >>>> - (#poke struct tm,tm_hour ) p_tm (fromIntegral hour :: CInt) > >>>> - (#poke struct tm,tm_mday ) p_tm (fromIntegral mday :: CInt) > >>>> - (#poke struct tm,tm_mon ) p_tm (fromIntegral (mon-1) :: CInt) > >>>> - (#poke struct tm,tm_year ) p_tm (fromIntegral (year-1900) :: CInt) > >>>> - (#poke struct tm,tm_isdst) p_tm (-1 :: CInt) > >>>> - t <- mktime p_tm > >>>> -#if __GLASGOW_HASKELL__ >= 603 > >>>> - return (TOD (fromIntegral (fromEnum t) + fromIntegral (tz-currTZ)) 0) > >>>> -#else > >>>> - return (TOD (fromIntegral t + fromIntegral (tz-currTZ)) 0) > >>>> -#endif > >>>> -foreign import ccall unsafe mktime :: Ptr () -> IO CTime > >>>> - > >>>> -{-# NOINLINE currTZ #-} > >>>> -currTZ :: Int > >>>> -currTZ = ctTZ (unsafePerformIO (getClockTime >>= toCalendarTime)) -- Hack > >>>> + toClockTime $ CalendarTime { > >>>> + ctYear = year, > >>>> + ctMonth = toEnum $ mon, > >>>> + ctDay = mday, > >>>> + ctHour = hour, > >>>> + ctMin = min, > >>>> + ctSec = sec, > >>>> + ctPicosec = 0, > >>>> + ctTZ = tz > >>>> + } > >>>> > >>>> parseTZ :: ReadP Int > >>>> parseTZ = (char '+' >> readDecP) `mplus` (char '-' >> fmap negate readDecP) > >>>> @@ -373,14 +362,14 @@ > >>>> getTime :: ReadP ClockTime > >>>> getTime = do > >>>> (hour, minutes, seconds) <- readHMS > >>>> - return (mkClockTime 1970 1 1 hour minutes seconds currTZ) > >>>> + return (mkClockTime 1970 1 1 hour minutes seconds 0) > >>>> > >>>> fromSqlValue SqlDate s = f_read getDate s > >>>> where > >>>> getDate :: ReadP ClockTime > >>>> getDate = do > >>>> (year, month, day) <- readYMD > >>>> - return (mkClockTime year month day 0 0 0 currTZ) > >>>> + return (mkClockTime year month day 0 0 0 0) > >>>> > >>>> fromSqlValue SqlDateTimeTZ s = f_read getDateTimeTZ s > >>>> where > >>>> @@ -400,7 +389,7 @@ > >>>> getDateTime :: ReadP ClockTime > >>>> getDateTime = do > >>>> (year, month, day, hour, minutes, seconds) <- readDateTime > >>>> - return (mkClockTime year month day hour minutes seconds currTZ) > >>>> + return (mkClockTime year month day hour minutes seconds 0) > >>>> > >>>> fromSqlValue _ _ = Nothing > >>>> > >>> > >>>> # This Makefile is mostly a wrapper around Setup.hs for people who > >>>> # just want to type make. > >>>> > >>>> CAS=runhaskell Setup.lhs > >>>> CONFOPTS ?= --user --prefix=${HOME} > >>>> INSTOPTS ?= --user > >>>> > >>>> all: build > >>>> > >>>> configure: .setup-config > >>>> .setup-config: HSQL.cabal > >>>> ${CAS} configure ${CONFOPTS} > >>>> > >>>> build: configure > >>>> ${CAS} build > >>>> > >>>> install: build > >>>> ${CAS} install ${INSTOPTS} > >>>> > >>>> uninstall: unregister > >>>> unregister: configure > >>>> ${CAS} unregister > >>>> > >>>> clean: > >>>> -runhaskell Setup.hs clean > >>>> -rm -rf dist > >>>> -rm -f .setup-config > >>>> > >>>> .PHONY: all configure build install uninstall unregister clean > >>> > >>> > >>> > >>> ------------------------------------------------------------------------ > >>> > >>> diff -ur HSQL-1.7-modified/HSQL/Database/HSQL.hsc HSQL-1.7-modified-2/HSQL/Database/HSQL.hsc > >>> --- HSQL-1.7-modified/HSQL/Database/HSQL.hsc 2005-12-15 20:57:18.000000000 +0000 > >>> +++ HSQL-1.7-modified-2/HSQL/Database/HSQL.hsc 2006-08-17 22:04:23.000000000 +0100 > >>> @@ -304,28 +304,17 @@ > >>> > >>> toSqlValue d = show d > >>> > >>> -mkClockTime :: Int -> Int -> Int -> Int -> Int -> Int -> Int -> ClockTime > >>> mkClockTime year mon mday hour min sec tz = > >>> - unsafePerformIO $ do > >>> - allocaBytes (#const sizeof(struct tm)) $ \ p_tm -> do > >>> - (#poke struct tm,tm_sec ) p_tm (fromIntegral sec :: CInt) > >>> - (#poke struct tm,tm_min ) p_tm (fromIntegral min :: CInt) > >>> - (#poke struct tm,tm_hour ) p_tm (fromIntegral hour :: CInt) > >>> - (#poke struct tm,tm_mday ) p_tm (fromIntegral mday :: CInt) > >>> - (#poke struct tm,tm_mon ) p_tm (fromIntegral (mon-1) :: CInt) > >>> - (#poke struct tm,tm_year ) p_tm (fromIntegral (year-1900) :: CInt) > >>> - (#poke struct tm,tm_isdst) p_tm (-1 :: CInt) > >>> - t <- mktime p_tm > >>> -#if __GLASGOW_HASKELL__ >= 603 > >>> - return (TOD (fromIntegral (fromEnum t) + fromIntegral (tz-currTZ)) 0) > >>> -#else > >>> - return (TOD (fromIntegral t + fromIntegral (tz-currTZ)) 0) > >>> -#endif > >>> -foreign import ccall unsafe mktime :: Ptr () -> IO CTime > >>> - > >>> -{-# NOINLINE currTZ #-} > >>> -currTZ :: Int > >>> -currTZ = ctTZ (unsafePerformIO (getClockTime >>= toCalendarTime)) -- Hack > >>> + toClockTime $ CalendarTime { > >>> + ctYear = year, > >>> + ctMonth = toEnum $ (mon-1), > >>> + ctDay = mday, > >>> + ctHour = hour, > >>> + ctMin = min, > >>> + ctSec = sec, > >>> + ctPicosec = 0, > >>> + ctTZ = tz > >>> + } > >>> > >>> parseTZ :: ReadP Int > >>> parseTZ = (char '+' >> readDecP) `mplus` (char '-' >> fmap negate readDecP) > >>> @@ -373,14 +362,14 @@ > >>> getTime :: ReadP ClockTime > >>> getTime = do > >>> (hour, minutes, seconds) <- readHMS > >>> - return (mkClockTime 1970 1 1 hour minutes seconds currTZ) > >>> + return (mkClockTime 1970 1 1 hour minutes seconds 0) > >>> > >>> fromSqlValue SqlDate s = f_read getDate s > >>> where > >>> getDate :: ReadP ClockTime > >>> getDate = do > >>> (year, month, day) <- readYMD > >>> - return (mkClockTime year month day 0 0 0 currTZ) > >>> + return (mkClockTime year month day 0 0 0 0) > >>> > >>> fromSqlValue SqlDateTimeTZ s = f_read getDateTimeTZ s > >>> where > >>> @@ -400,7 +389,7 @@ > >>> getDateTime :: ReadP ClockTime > >>> getDateTime = do > >>> (year, month, day, hour, minutes, seconds) <- readDateTime > >>> - return (mkClockTime year month day hour minutes seconds currTZ) > >>> + return (mkClockTime year month day hour minutes seconds 0) > >>> > >>> fromSqlValue _ _ = Nothing > > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys-and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > htoolkit-users mailing list > htoolkit-users(a)lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/htoolkit-users > -- http://ofb.net/~frederik/

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Re: [Haskell] ANNOUNCE: Haddock version 2.0.0.0
by Ross Paterson 13 Feb '08

13 Feb '08

On Tue, Jan 08, 2008 at 01:28:50PM +0100, David Waern wrote: > * Format of module attributes has changed. The only way of specifiying > module attributes is via a new OPTIONS_HADDOCK pragma. Example: > {-# OPTIONS_HADDOCK hide, prune #-} Unfortunately the old-style attributes are widely used: over 400 modules in hackage, including 100 shipped with GHC. The vast majority of these are #hide, which ideally should be unnecessary if the modules are not exposed. However some packages expose modules for use in the internals of other packages, but don't want to show those modules in the documentation. For example, most of the GHC.* modules in the base package, which are used in the internals of many of the packages split from base. If I add the new-style attributes to the base package, it hides those modules in the documentation for base, but packages that depend on base seem to generate links to locations in those hidden modules, e.g. uses of IO point at GHC.IOBase.IO. Also, the new haddock rejects some modules the old one accepted. For example, it doesn't like extra doc comments that aren't attached to anything. It also rejects data Pair = Pair {-# UNPACK #-} !Int -- ^ first field {-# UNPACK #-} !Int -- ^ second field

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Proposal: Add concatMapM function (#2042)
by Twan van Laarhoven 06 Feb '08

06 Feb '08

Hello library people, I have noticed that many projects include a 'concatMapM' function: concatMapM :: (Monad m) => (a -> m [b]) -> [a] -> m [b] I think this is useful in general, so let's add it to Control.Monad. Trac ticket: http://hackage.haskell.org/trac/ghc/ticket/2042 Deadline for discussion: 2 weeks from now, January 28 Twan

25 94

Proposal: Add variants of tails & inits not returning empty lists
by Maxime Henrion 31 Jan '08

31 Jan '08

Hi all, I just opened a Trac ticket (#1979), to suggest the addition of the inits1 and tails1 functions, which don't return empty lists unlike their counterpart. They're defined as such : inits1 = tail . inits tails1 = init . tails I've needed them a few times so I thought they would make a nice addition to the base package. And, I've got to say, the symmetry in this code is is nice :-). http://hackage.haskell.org/trac/ghc/ticket/1979 Cheers, Maxime

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