- Libraries - Haskell.org

Some QuickCheck Instances
by Dominic Steinitz 25 Oct '08

25 Oct '08

I often find I need to use QuickCheck & SmallCheck with e.g. Word8 but there don't seem to be standard instances. Would these be worth adding? If so, what would I need to do? Just send a patch to the maintainers? Thanks, Dominic. > > instance Serial Word8 where > series d = drawnFrom (map fromIntegral [0..d]) > instance Arbitrary Word8 where > arbitrary = > do n <- choose ((fromIntegral (minBound::Word8))::Int, > (fromIntegral (maxBound::Word8))::Int) > return (fromIntegral n) > > instance Arbitrary Word64 where > arbitrary = > do n <- choose ((fromIntegral (minBound::Word64))::Integer, > (fromIntegral (maxBound::Word64))::Integer) > return (fromIntegral n) > > instance Arbitrary Word128 where > arbitrary = > do n <- choose ((fromIntegral (minBound::Word128))::Integer, > (fromIntegral (maxBound::Word128))::Integer) > return (fromIntegral n) >

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fgl version missing on hackage
by Christian Maeder 23 Oct '08

23 Oct '08

Hi Ross, on http://hackage.haskell.org/cgi-bin/hackage-scripts/package/fgl there are fgl-versions 5.3, 5.4.1.1 However, ghc-6.8.3 was shipped with fgl-5.4.2.0 fgl-5.4.2.0 exports more functions (ie. xdfsWith) and I would like to use it with other ghc versions, too. Could you upload fgl-5.4.2.0? Cheers Christian

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Proposal #2717: Add nubWith, nubOrd
by Bart Massey 23 Oct '08

23 Oct '08

Ok, I've killed the overly ambitious proposal #2629, and replaced it with the more modest proposal #2717 http://hackage.haskell.org/trac/ghc/ticket/2717 which just adds Data.List.nubWith and Data.Set.nubOrd as previously discussed ad nauseam. I know at least one person thought that adding these was a bad idea, but some others thought it was a fine thing to do. Hence the discussion on this list. Bart Massey bart(a)cs.pdx.edu

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Repair to floating point enumerations?
by Malcolm Wallace 22 Oct '08

22 Oct '08

Dear Haskell-Primers (and libraries). Recently, Phil Wadler has pointed out a weird anomaly in the Haskell'98 Prelude, regarding numeric enumerations for Floats/Doubles: Prelude> [0, 0.3 .. 1.1] [0.0,0.3,0.6,0.899999,1.2] What is odd is that the last value of the list is much larger than the specified termination value. But this is exactly as specified by the Haskell'98 Report. http://haskell.org/onlinereport/basic.html#sect6.3.4 "For Float and Double, the semantics of the enumFrom family is given by the rules for Int above, except that the list terminates when the elements become greater than e3+i/2 for positive increment i, or when they become less than e3+i/2 for negative i. We have discussed this question (and related ones, such as whether Float and Double belong in the Enum class at all) several times before, and I do not wish to rehash all of those points again e.g.: http://www.cse.unsw.edu.au/~dons/haskell-1990-2000/msg07289.html http://www.haskell.org/pipermail/haskell/2001-October/008218.html http://www.haskell.org/pipermail/haskell/2002-October/010607.html Phil proposes that, although retaining the instances of Enum for Float and Double, we simplify the definitions of the numericEnumFrom family: numericEnumFromThenTo :: (Fractional a, Ord a) => a -> a -> a -> [a] numericEnumFrom = iterate (+1) numericEnumFromThen n m = iterate (+(m-n)) n numericEnumFromTo n m = takeWhile (<= m) (numericEnumFrom n) numericEnumFromThenTo n m p = takeWhile (<= p) (numericEnumFromThen n m) The particular feature of note is that the odd fudge factor of (1/2 * the increment) is removed. The inexact nature of floating point numbers would therefore cause a specification like [ 0.0, 0.1 .. 0.3 ] to yield the sequence [ 0.0, 0.1, 0.2 ] that is, to omit the upper bound, because (3 * 0.1) is actually represented as 0.30000000000004, strictly greater than 0.3. Phil argues that this behaviour is more desirable: "the simple fix is that the user must add a suitable epsilon to the upper bound. The key word here is *suitable*. The old definitions included completely bizarre and often highly unsuitable choices of epsilon." This proposal seems to me to improve the consistency of the enumeration syntax across both the integral and floating types. Some users may still be surprised, but the surprise will be easier to explain. I am bringing this question to the attention of all who are interested in Haskell Prime, because it seems like a sensible and well-reasoned change. Discussion on whether to adopt this proposal for H' is welcome. But as maintainer and bug-fixer of the Haskell'98 Report, I have also been asked whether we should make this change retrospectively to the Haskell'98 language (as a "typo"). Since it involves not merely an ordinary library function, but a Prelude function, and moreover a function that is used in the desugaring of syntax, it is less clear to me whether to alter Haskell'98. Thoughts? Regards, Malcolm

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Arch Haskell News: Oct 18 2008
by Don Stewart 19 Oct '08

19 Oct '08

= News about Haskell on Arch Linux = Arch Linux now has 639 Haskell packages in AUR. That’s an increase of 15 new Haskell packages in the last 7 days. Growth appears to be holding steady at just over 2 new packages a day on Hackage this month. Noteworthy * haskell-gnuplot-0.2: “2D and 3D plots using gnuplot” * alex-2.3: “Alex is a tool for generating lexical analysers in Haskell” * happy-1.18.1: “Happy is a parser generator for Haskell” * haskell-tfp-0.1: “Type-level programming library using type families” Full details on the site. http://archhaskell.wordpress.com/2008/10/18/arch-haskell-news-oct-18-2008/

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Re: [Haskell-cafe] ANNOUNCE: Glob 0.1, globbing library
by Krzysztof Skrzętnicki 18 Oct '08

18 Oct '08

On Fri, Oct 17, 2008 at 22:02, Matti Niemenmaa <matti.niemenmaa+news(a)iki.fi> wrote: > Greetings to all, > > I hereby announce the release of Glob 0.1, a small library for glob-matching > purposes based on a subset of zsh's syntax. > > Web page at: http://iki.fi/matti.niemenmaa/glob/index.html > Hackage: http://hackage.haskell.org/cgi-bin/hackage-scripts/package/Glob > > Simple example: match (compile "foo*baz") "foobarbaz" == True. > > It can also group the contents of a directory given a list of patterns to match: > globDir [compile "foo*baz"] "<a directory containing foobarbaz and joe>" gives > (["dir/foobarbaz"],["dir/joe"]). > > Comments, complaints, feature requests, bug reports are all welcome. It should > work on both GHC 6.8 and 6.10, but I've only tested the latter. > Hello I tried out your package, but it doesn't seem to work correctly on Windows. I checked the code and it has directory separator hard coded, which seem to be the source of problems. Please see: http://www.haskell.org/ghc/docs/latest/html/libraries/filepath/System-FileP… All best Christopher Skrzętnicki

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Re: Compiling regex-posix-0.93.2 on windows
by Chris Kuklewicz 18 Oct '08

18 Oct '08

I am not sure what is going wrong. I have not been using Haskell on windows. I am also copying this reply to haskell-cafe and libaries mailing lists. Does anyone know? Parnell Flynn wrote: > I am having a terrible time compiling the 0.93.2 version of the > regex-posix library on windows XP. > > I have Cygwin and MinGW installed and I have a version of the regex.h > header in C:/cygwin/usr/include what shared libraries do I need? > > Here is a copy of the error it finds the include but is unable to link. > > This links to the standard c library version of regular expressions. > > The corresponding c header file is regex.h and there is a chance you > > will need to edit the end of the regex-posix.cabal file to find the > > include directory and/or library. > > Preprocessing library regex-posix-0.93.2... > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x85):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xc9):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0xf1):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x125):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x159):Wrap_hsc_make.c: > undefined reference to `_impure_ptr' > > dist/build/Text/Regex/Posix/Wrap_hsc_make.o(.text+0x18d):Wrap_hsc_make.c: > more undefined references to `_impure_ptr' follow > > collect2: ld returned 1 exit status > > linking dist\build\Text\Regex\Posix\Wrap_hsc_make.o failed > > command was: y:\ghc\ghc-6.8.2\bin\ghc.exe -optl-LC:/cygwin/lib > dist\build\Text\Regex\Posix\Wrap_hsc_make.o -o > dist\build\Text\Regex\Posix\Wrap_hsc_make.exe > > bash-3.2$ > > Thanks, > > Parnell > > Parnell Flynn • 230 South Lasalle Street • Suite 400 • Chicago, IL 60604 > • 312.244.5317 (o) • parnell___.flynn(a)ronin-capital.com_ > <mailto:parnell.flynn@ronin-capital.com> >

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OpenGL+GLUTwith ghc-6.10 ?
by Conal Elliott 18 Oct '08

18 Oct '08

Has anyone gotten OpenGL+GLUT to work with ghc-6.10? It crashes for me on createWindow (from Graphics.UI.GLUT.Window). I'm using the ghc-6.10.0.20081007 from a win32 installer, along with OpenGL-2.2.1.1 and GLUT-2.1.1.2 from Hackage. Thanks, - Conal

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2008-10-11 Hackage status with GHC 6.10
by Don Stewart 17 Oct '08

17 Oct '08

Daily update of the state of Hackage wrt. GHC 6.10 release candidates. Lots of packages were updated today, Cabal 1.6 and cabal-install 0.6 were also put out. Things are in a good shape. Note that you'll need a "soft dep" in your cabal index file, base < 4 parsec < 3 HaXml == 1.13.* QuickCheck < 2 for best results. Using GHC 6.10 RC, Cabal 1.6 and cabal-install 1.16, of 684 libraries and apps tried in total, 1 UnpackFailed 2 DownloadFailed 2 InstallFailed 16 ConfigureFailed 74 DependencyFailed 134 BuildFailed 455 InstallOk Compared to GHC 6.8.x's results, there are now *48* packages that produce different results, or *6%* (down 2% from yesterday). The most common issues are, * Changes to Arrow class definition * Changes to types of Map and Set functions * Cabal changes * Changes to ghc-api * Changes to when 'forall' is parsed (add Rank2Types) * GHC.Prim was moved, * Changes to -fvia-C and headers * GADT changes, * pragma warnings tightened * Integer constructors have moved * New warnings and used -Werror How to address these, as library maintainers, is addressed here, http://haskell.org/haskellwiki/Upgrading_packages Packages that have broken wrt. the new core library APIs are, ArrayRef-0.1.2 CLASE-2008.9.23.2 EdisonCore-1.2.1.2 HPDF-1.4 HaLeX-1.1 Hashell-0.15 Hipmunk-0.2 MemoTrie-0.0 NewBinary-0.1.1 PArrows-0.1 TypeCompose-0.5 WebBits-0.9.2 YamlReference-0.9.2 Yampa-0.9.2.2 arrows-0.4 bytestring-show-0.2 cabal-setup-1.2.1 chp-1.1.0 cmath-0.3 fixpoint-0.1 hasim-0.1 hask-home-2007.12.6 heap-0.4.0 hetris-0.2 hexpat-0.2 hinstaller-2008.2.16 hint-0.2.4.1 hslackbuilder-0.0.1 hxt-8.1.0 iException-0.0.1 libGenI-0.16.1 list-extras-0.2.2 logfloat-0.9.1 mage-1.1.0 numeric-prelude-0.0.4 plugins-1.3 quantum-arrow-0.0.4 regex-tdfa-0.94 streamproc-1.1 stringtable-atom-0.0.4 typalyze-0.1.1 unicode-prelude-0.1 xmonad-utils-0.1 yhccore-0.9 GHC bugs are suspected for, xmonad-contrib, stream-fusion, harpy, OpenAFP Tickets are open for these. Build reports for these packages were posted yesterday, http://article.gmane.org/gmane.comp.lang.haskell.glasgow.user/15430 -- Don

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Proposal #2659: Add sortOn and friends to Data.List
by Twan van Laarhoven 16 Oct '08

16 Oct '08

Hello list, Almost all uses of sortBy in user code use 'comparing', 'on' or a similar construction [1]. I think we should add a function that makes this common behavior more convenient: sortOn :: Ord b => (a -> b) -> [a] -> [a] For consistency we should also add *On for the other *By functions in Data.List: nubOn :: Eq b => (a -> b) -> [a] -> [a] deleteOn :: Eq b => (a -> b) -> a -> [a] -> [a] deleteFirstsOn :: Eq b => (a -> b) -> [a] -> [a] -> [a] unionOn :: Eq b => (a -> b) -> [a] -> [a] -> [a] intersectOn :: Eq b => (a -> b) -> [a] -> [a] -> [a] groupOn :: Eq b => (a -> b) -> [a] -> [[a]] sortOn :: Ord b => (a -> b) -> [a] -> [a] insertOn :: Ord b => (a -> b) -> a -> [a] -> [a] maximumOn :: Ord b => (a -> b) -> [a] -> a minimumOn :: Ord b => (a -> b) -> [a] -> a (nubSortOn :: Ord b => (a -> b) -> [a] -> [a]) -- see #2629 -- Naming -- "On": The reason for the "on" suffix is that it relates to the "on" function from Data.Function: "sortOn f = sort (compare `on` f)". In code, "sortOn fst" is reasonably natural, "sortBy fst" would be better but that is already taken. "With": Another possible choice is the "with" suffix. There is some precedence for this choice [2]. A big disadvantage is that the "with" suffix is commonly used for combining functions, as in Data.Map.unionWith. Making a Data.List.unionWith that does something completely different sounds like a bad idea. "ByComparing": Defining sortByComparing f = sortBy (comparing f) makes sense, naming wise. A disadvantage of this name is that it is too long. Also, we would get a distinction between "groupByEquating" and "sortByComparing". -- Variations -- When f is a slow function the call "sortOn f xs" recomputes f more than necessary. A version that caches the result of f is easy to define: sortOn' f = map fst . sortOn snd . map (\x -> (x,f x)) This is perhaps not the best name, since ' usually means strictness. -- Descending sort-- To be able to sort lists in reverse order, a simple newtype should be added to Data.Ord: newtype Down a = Down { getDown :: a } instance Ord a => Ord (Down a) where Down x < Down y = y < x Now "sortOn Down xs == reverse (sort xs)". The name Down comes from [2], maybe Desc is a better name? -- Proposal-- Ticket: #2659 (for sortOn and friends) Ticket: #2660 (for Down newtype) Deadline: now+2 weeks = 2008-10-20 Questions: 1. should sortOn be added to Data.List? 2. should all other *On functions be added as well? 3. what name should these functions get? 4. should the sortOn' variations be added? What about the naming? 5. should Down be added to Data.Ord? Note: The addition of sortOn was previously proposed as #2406 and rejected because it did not follow the library submission guidelines. Twan [1] http://www.google.com/codesearch?q=lang%3Ahaskell+sortBy [2] http://research.microsoft.com/~simonpj/papers/list-comp/index.htm

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