- Libraries - Haskell.org

Release Candidates for Haskell Platform 2012.4.0.0
by Mark Lentczner 26 Oct '12

26 Oct '12

The second release candidate of HP 2012.4.0.0 is now available: - Source tarball: haskell-platform-2012.4.0.0-rc2.tar.gz<http://ozonehouse.com/mark/platform/haskell-platform-2012.4.0.0-rc2.tar.gz> - Mac 32-bit installer: Haskell Platform 2012.4.0.0 32bit rc2 signed.pkg<http://ozonehouse.com/mark/platform/Haskell%20Platform%202012.4.0.0%2032bit…> - Mac 64-bit installer: Haskell Platform 2012.4.0.0 64bit rc2 signed.pkg<http://ozonehouse.com/mark/platform/Haskell%20Platform%202012.4.0.0%2064bit…> - Windows installer: HaskellPlatform-2012.4.0.0-rc1-setup.exe<http://code.haskell.org/~refold/HaskellPlatform-2012.4.0.0-rc1-setup.exe> Tickets closed for this release: http://trac.haskell.org/haskell-platform/query?status=closed&group=componen… If you can, please test the release candidate and let us know how it works out. We are on track for final release on November 5th. - Mark

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Re: [Haskell-cafe] Release Candidate 2: HP 2014.4.0.0
by Mark Lentczner 19 Oct '12

19 Oct '12

On Fri, Oct 19, 2012 at 9:30 AM, Colin Adams <colinpauladams(a)gmail.com>wrote: > That's VERY efficient (2014 editions out in 2012). Silly me! Of course, the links are correct: no time travel this cycle - just plain ole' 20*12*.4.0.0 .. aaaaaand: Mac OS 64-bit candidate is out: Haskell Platform 2012.4.0.0 64bit rc2 signed.pkg<http://www.ozonehouse.com/mark/platform/Haskell%20Platform%202012.4.0.0%206…> *NOTE:* You can only have one architecture per HP version at a time installed on Mac OS X. If you want to switch architectures within the same version of the platform, please use the *uninstaller-hs* utility to remove the one you have *before* installing the other one. If you don't, you'll get an installer error at the end -- it will all work, but your documentation will be less than perfect. *NOTE:* If you use macports <http://www.macports.org/> or homebrew<http://mxcl.github.com/homebrew/>, then be sure that you choose the same architecture (32bit / 64bit) as macports or brew is using, since I believe those systems do not install universal libs (both architectures) by default. - Mark

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Release Candidate 2: HP 2014.4.0.0
by Mark Lentczner 19 Oct '12

19 Oct '12

Haskellistas - The second release candidate of HP 2014.4.0.0 is now available: - Source tarball: haskell-platform-2012.4.0.0-rc2.tar.gz<http://ozonehouse.com/mark/platform/haskell-platform-2012.4.0.0-rc2.tar.gz> - Mac 32-bit installer: Haskell Platform 2012.4.0.0 32bit rc2 signed.pkg<http://ozonehouse.com/mark/platform/Haskell%20Platform%202012.4.0.0%2032bit…> Mac notes: This version is now digitally signed by me, and so will install without fuss on OS X 10.8. I'll put up 64-bit version soon. - Mark Changes since RC1: TODO ---- [x] update vector and primitive versions (they had a point release to fix a bad bug, and the fix was very very simple) [x] remove Build.hs - it did all its work by shelling out anyway! [x] main .cabal file should not have versions commented out [x] this will require a way to extract the list of packages that need to be part of the source release [x] why not also extract the list of packages needed for core.packages [x] fix to build.hs (ticket #195) [x] bugs in build.sh (ticket #197) [x] build instructions in the tarball (ticket #207) [x] merge in shared library patch (ticket #198) MAC TODO -------- [x] mac cabal script needs to quote things with $HOME or ~ in them (ticket #192) [x] If the cabal command is "update" then the wrapper script shouldn't do an update the first time through! [x] sign Mac installers (ticket #203)

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haddock, instances and defining modules
by Daniel Gorín 18 Oct '12

18 Oct '12

Hi The haddock page for Data.Either lists an instance Functor (Either a). However, this instance doesn't get in scope when importing Data.Either. E.g., the following program fails to compile: > import Data.Either > > main = print $ fmap not $ Right "hello" AFAIK, one needs to import Control.Monad.Instances instead to get such an instance; but there is nothing in the haddock page of Data.Either that suggests it. This can be quite frustrating for beginners! It would be good if the docs could be improved here, but I'm not sure what to suggest (maybe haddock should be generating something else in these cases?)… Any thoughts? Thanks, Daniel

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Adding dataCast1 and dataCast2 methods to the Data instances of Ptr, ForeignPtr, and Array
by José Pedro Magalhães 17 Oct '12

17 Oct '12

Hello all, This email is to draw your attention to http://hackage.haskell.org/trac/ghc/ticket/7256. Missing dataCast1 and dataCast2 methods in Data instances results in incorrect behaviour when using SYB's ext1/ext2 functions. The proposed fix adds the methods, but it requires adding additional Data constraints to these instances. Here's the relevant part of the diff: -instance Typeable a => Data (Ptr a) where > +instance (Data a, Typeable a) => Data (Ptr a) where > > -instance Typeable a => Data (ForeignPtr a) where > +instance (Data a, Typeable a) => Data (ForeignPtr a) where > > -instance (Typeable a, Data b, Ix a) => Data (Array a b) > +instance (Typeable a, Data a, Data b, Ix a) => Data (Array a b) > Does anyone find this change problematic? Cheers, Pedro

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Foldable & Traversable instances for ((,) a)
by Merijn Verstraaten 16 Oct '12

16 Oct '12

I noticed (to my great dismay!) that ((,) a) doesn't appear to have Foldable or Traversable instance anywhere, even though it is an (almost trivial) instance of both: instance Foldable ((,) a) where foldMap f (_, x) = f x instance Traversable ((,) a) where traverse f (a, x) = (,) a <$> f x I guess the most appropriate place for either would be Data.Tuple of Data.Foldable and Data.Traversable respectively. Kind regards, Merijn Verstraaten

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Strictness of modify in Control.Monad.State.Strict
by Ben Gamari 12 Oct '12

12 Oct '12

Is there a reason there is no `modify` operation in Control.Monad.State.Strict (and the transformers analogue) which is truly strict in the state? That is, modify' :: Monad m => (a -> a) -> StateM a m () modify' f = get >>= (\x -> put $! f x) While this is admittedly not a difficult piece of code to write, even the suggestion in the documentation that `modify` isn't as strict as one might think would likely save many man-hours of debugging (especially for those who are less familiar with the language, for whom, speaking from experience, strictness issues can pose a major hurdle to adoption) In general it would be nice if the notion of strictness were better addressed in the major libraries' documentation. It's a nuanced issue which is not fully captured by a ".Lazy" or ".Strict" in the module name. Just a thought. Thanks, - Ben

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ANN: data-dword: Long binary words from short ones
by Mikhail Vorozhtsov 11 Oct '12

11 Oct '12

Hi. I'm pleased to announce my new little library, data-dword[1]. It provides Template Haskell utilities for defining binary word data types from low and high halves, e.g. data Word96 = Word96 Word32 Word64 -- strictness is configurable data Int96 = Int96 Int32 Word64 -- All instances are fully implemented (including `quotRem`, etc) instance Bounded, Enum, Eq, Integral, Num, Ord, Read, Real, Show, Ix, Bits, Hashable -- Extra bit-manipulating functions, unwrapped addition and -- multiplication, etc. instance BinaryWord, DoubleWord -- Rewrite rules for converting to/from the standard integral types {-# RULES "fromIntegral/..." ... #-} The library comes with a pretty thorough test suite (that ATM has some failures on x86-32 due to bug #7233[2] in the base library). [1] http://hackage.haskell.org/package/data-dword [2] http://hackage.haskell.org/trac/ghc/ticket/7233

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Haskell Platform proposal: Add the vector package
by Johan Tibell 08 Oct '12

08 Oct '12

Hi, I am, with Roman's support, making a formal proposal to have the vector package included in the Haskell Platform: http://trac.haskell.org/haskell-platform/wiki/Proposals/vector See the wiki page for details, and a list of open issues for discussion. The vector package itself can be found on Hackage: http://hackage.haskell.org/package/vector I have set the deadline to 13 August 2012 (~2 months' time), with comments due by 13 July 2012 (~one month). There's plenty of time before the next platform release anyway (scheduled for 12 November 2012). -- Johan

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Stricter WriterT monad transformer
by Gabriel Gonzalez 06 Oct '12

06 Oct '12

This is a suggestion I initially ran by Ross and he recommended that I post it to this mailing list. Here's the problem: WriterT always leaks space. I've tested three ways to fix the space leak, and only one works: * [DOES NOT WORK] Add a strictness annotation to the Monad instance for WriterT * [DOES NOT WORK] Use the StateT monad transformer *without* a strictness annotation * [WORKS] Use the StateT monad transformer *with* a strictness annotation I've hpasted the three different approaches and their test cases so you all can test it for yourselves: http://hpaste.org/75837 I'm requesting this because I need a WriterT monad transformer that does not leak space for defining folds for my pipes library. I can temporarily define the correct one within my own library but in the long run I believe it belongsin transformers. I also discovered another subtle advantage of using StateT to simulate WriterT. The traditional WriterT monad instance punishes the case where you use a free monad as the base monad because of the following bind in its monad instance: instance (Monad m, Monoid w) => Monad (WriterT w m) where return a = WriterT2 $ return (a, mempty) m >>= f = WriterT2 $ do (a, w) <- runWriterT m (b, w') <- runWriterT (k a) <= This bind is the problem return (b, w `mappend` w') This bind triggers a quadratic blowup when the base monad is a free monad, whereas the StateT simulation of WriterT runs in linear time. For these reasons, I suggest adding a "Control.Monad.Trans.Writer.Stricter" module to "transformers" that implements WriterT using the "WriterT4" implementation from the above hpaste.

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