- Libraries - Haskell.org

Proposal: Make StateT in mtl lazy
by Ian Lynagh 05 Feb '07

05 Feb '07

http://hackage.haskell.org/trac/ghc/ticket/1127 Deadline: 28 February 2007. I propose we make StateT lazy, as I suspect was the intention all along and as has been discussed (without reaching a conclusion) before. The patch is simply (in the definition of (>>=)): hunk ./Control/Monad/State.hs 195 - (a, s') <- runStateT m s + ~(a, s') <- runStateT m s Thanks Ian

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Paramorphisms / Data.Scanable?
by Jim Apple 04 Feb '07

04 Feb '07

I understand that it may not be possible to give simple types to anamorphisms or hylomorphisms, but I don't see there can't be a Data.Scannable with paramorphisms. class Scannable t where scanr :: (a -> b -> b) -> b -> t a -> t b scanl :: (a -> b -> a) -> a -> t b -> t a scanr1 :: (a -> a -> a) -> t a -> t a scanl1 :: (a -> a -> a) -> t a -> t a Jim

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Catamorphisms for arrows?
by Jim Apple 04 Feb '07

04 Feb '07

Could Data.Foldable be extended to function types by way of Bananas in Space: Extending Fold and Unfold to Exponential Types [1][2] or Boxes Go Bananas: Encoding Higher-Order Abstract Syntax with Parametric Polymorphism [3][4]? 1. http://citeseer.ist.psu.edu/293490.html 2. http://www.cs.nott.ac.uk/~gmh//bananas.ps 3. http://repository.upenn.edu/cis_reports/43/ 4. http://www.seas.upenn.edu/%7Esweirich/abstracts.html#washburn+:bgb-journal Jim

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Gtk2Hs 0.9.11 RC2 available for testing
by Duncan Coutts 03 Feb '07

03 Feb '07

The second release candidate for Gtk2Hs 0.9.11 is now available. (The actual version number is 0.9.10.6) The source tarball and windows installer are available: http://haskell.org/gtk2hs/gtk2hs-0.9.10.6.tar.gz (md5sum 8842898cb1f6b595b5a3a057e66a810b) http://haskell.org/gtk2hs/gtk2hs-0.9.10.6.exe (md5sum 97ed838d88ee2d6a01e78d3fea26c18c) and the corresponding documentation: http://haskell.org/gtk2hs/docs/gtk2hs-docs-0.9.10.6/ Changes since 0.9.10: * works with GHC-6.6 and Gtk+ 2.10.x * new typed tree/list widget API * new OpenGL widget added * new cairo SVG package (for rendering SVG images on cairo surfaces) * new implementation of the Graphics.SOE API * new glade tutorial (and hopefully the new intro tutorial will be ready in time too) * many more demo programs (clock, graph, traffic congestion sim, fonts, noughts & crosses, opengl, svg and updated profile viewer and other tree/list demos) * much smaller binaries (thanks to the ghc 'split objs' feature) * many bugs fixed * various minor documentation improvements Changes since the first release candidate: * now works again in GHCi (even in Windows!) * new functions for working with the threaded RTS * new ./configure --enable-profiling flag * new ./configure --with-user-pkgconf flag * Windows version now uses the "MS Windows" theme by default * Windows version now comes with the Gtk+ OpenGL package * Windows version now supports GHCi (6.6 only) and profiling * minor fixes to various demo programs * the svgcairo package now uses librsvg rather than libsvg-cairo Please test this on your platform and report success or failures to the gtk2hs users list (gtk2hs-users(a)lists.sourceforge.net) So far we've tested on Linux (x86, x86-64, sparc), Windows and Solaris (sparc) with GHC 6.2.2, 6.4.1, 6.4.2, 6.6 and with Gtk+ 2.0 and 2.10. Build reports from people using *BSD, Mac OS X (ppc or x86), GHC 6.0.x or Gtk+ 2.4-2.8 would be particularly appreciated. Windows notes: The installer expects GHC 6.4.2 or 6.6. (As always if you need a build for a different version of GHC then that's possible by building from source.) The GHCi support is only for GHC-6.6 (due to the infamous relocs overflow bug in earlier versions). The installer now comes bundled with Gtk+ itself so there's no need to download it separately. Hopefully this should also make the installation process a bit more reliable if only by reducing the number of configuration combinations. The windows build doesn't include the svgcairo or sourceview packages since they introduce rather a large number of dependencies and would make the installer a much bigger download. Testing issues: I have enabled the 'split-objs' feature by default (for linking the Gtk2Hs libs such that the final binaries are much smaller). If you run into problems during during the build that you think are related to linking then try ./configure --disable-split-objs and report the problem and whether turning off split-objs fixed it. Depending on how it goes we'll decide whether to leave it on by default in the final release or not. For testing, try building, installing and then run: make installcheck This should build all the demo programs that are appropriate for your configuration. Running a selection of them would be good and if you have any other programs that use Gtk2Hs that you can test with, that'd be great. Packaging: For people preparing packages for distributions: note that there are three new packages, "gtkglext", "svgcairo" and "soegtk". For reference there is a Gentoo ebuild available: http://haskell.org/~gentoo/gentoo-haskell/dev-haskell/gtk2hs/ The mozembed package can now be built against firefox, seamonkey, xulrunner or mozilla. Just pass --enable-<thing> to ./configure. Duncan (on behalf of the Gtk2Hs team)

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UTF8 libraries
by Alistair Bayley 03 Feb '07

03 Feb '07

What is the state of UTF8 support in Haskell libraries (base or user-contributed)? I had a need for a UTF8 en & de-coder for Takusen, and after looking around couldn't find anything particularly satisfactory, so ended up writing (yet another) one. I'm interested mainly in marshalling to/from CStrings, so support for functions like peekUTF8String, newUTF8String, withUTF8String, etc is interesting. I realise that one can use one of the pure decoders after a peekCString, but that means building an intermediate list, which isn't strictly necessary. So far I've found the following: - John Meacham's UTF8 lib: http://repetae.net/repos/jhc/UTF8.hs (only handles codepoints < 65536, pure String <-> [Word8] so no direct CString marshalling) - HXT's Text.XML.HXT.DOM.Unicode: http://www.fh-wedel.de/~si/HXmlToolbox/ (full Unicode range - up to 6 bytes per char, pure String <-> String) - George Russell's: http://www.haskell.org/pipermail/glasgow-haskell-users/2004-April/006564.ht… (buggy - won't roundtrip chars > 127, pure String <-> String) The one I wrote, which is largely based on John Meacham's and HXT's code, can be seen here: http://darcs.haskell.org/takusen/Foreign/C/UTF8.hs Alistair

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ANN: Takusen 0.6
by Alistair Bayley 02 Feb '07

02 Feb '07

We are pleased to announce a new release of Takusen. There are a large number of changes and bug-fixes: - Oracle support for processing cursors returned from procedure calls - withContinuedSession supports connection reuse (e.g. for persistent connections and connection pooling) - new README file with useful information about getting started with Takusen - new UTF8 en/de-coder (the old one was buggy) - PostgreSQL support for CalendarTime - improved Cabal Setup.hs script, which does a better job of modifying the installation to reflect installed DBMS's. This gives good ghci support (PostgreSQL users on Windows have a small extra step) - prepared statement API requires that users distinguish between queries and DML Our long-term plans are the same as ever: - large objects - ODBC and MS Sql Server backends Release: http://darcs.haskell.org/takusen/takusen-0.6.tar.gz Source: darcs get --partial http://darcs.haskell.org/takusen Oleg and Alistair

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Unsafe aspects of ByteString
by Iavor Diatchki 01 Feb '07

01 Feb '07

Hello, The "packCString" function (and other similar functions) in the ByteString library break referential transperancy, which is one of the big selling points of Haskell (and its libraries). Here is an example: main = do x <- newCString "Hello" let s = packCString x h1 = B.head s print s -- print h1 poke x (toEnum 97) print s let h2 = B.head s print h1 print h2 Output: "Hello" "aello" 97 97 This is already confusing because the "pure" value 's' has magically changed. Also notice that the evaluation order of the program affects the output. If we include the commented out statement (which forces h1 to be evaluated earlier) the output becomes: "Hello" 72 "aello" 72 97 I think that because of this we should either remove these functions, or at least follow the convention of other libraries and give them "unsafe" names. -Iavor

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hackageDB
by Ross Paterson 31 Jan '07

31 Jan '07

The web interface to HackageDB (the repository of releases of Haskell packages) is still fairly crude, and much is yet to be added, but the basic functionality is working: http://hackage.haskell.org/packages/archive/pkg-list.html We now need more early adopters to add their packages and otherwise try it out. All comments welcome.

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Proposal: Add Data.String, containing IsString(fromString), to base
by Ian Lynagh 30 Jan '07

30 Jan '07

http://hackage.haskell.org/trac/ghc/ticket/1126 Proposal to create a new module Data.String, containing IsString(fromString), in the base package. This would be used by the overloaded strings extension (-foverloaded-strings in GHC). Deadline: 28 Feb 2007 Here's the meat of the patch: hunk ./Data/String.hs 1 +{-# OPTIONS_GHC -fno-implicit-prelude #-} +----------------------------------------------------------------------------- +-- | +-- Module : Data.String +-- Copyright : (c) The University of Glasgow 2007 +-- License : BSD-style (see the file libraries/base/LICENSE) +-- +-- Maintainer : libraries(a)haskell.org +-- Stability : experimental +-- Portability : portable +-- +-- Things related to the String type. +-- +----------------------------------------------------------------------------- + +module Data.String ( + IsString(..) + ) where + +#ifdef __GLASGOW_HASKELL__ +import GHC.Base +#endif + +-- | Class for string-like datastructures; used by the overloaded string +-- extension (-foverloaded-strings in GHC). +class IsString a where + fromString :: String -> a + +instance IsString [Char] where + fromString xs = xs Thanks Ian

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Problems with Cabal
by Marco Túlio Gontijo e Silva 29 Jan '07

29 Jan '07

Hello, I'm having some problems with cabal. I don't know if here is the better place to ask, in http://www.haskell.org/cabal/ sais to ask here. There are two things. One of them is simpler, and it's in haskell-cafe. Shouldn't include-dirs: . be default? The other is about setup clean. It's leaving some things behind. The dist directory is not removed, and is kept empty. Other files that are not removed are the c2hs generated files .h and .chi. Is this a bug? marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ find | grep -v _darcs . ./AUTHORS ./Algebra ./Algebra/Geometric ./Algebra/Geometric/Gpc.chs ./COPYING ./README ./Setup.hs ./ToDo ./haskellgpc.cabal ./send.sh marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ ./Setup.hs configure Configuring HaskellGPC-0.0.1... configure: /usr/bin/ghc-pkg configure: Dependency base-any: using base-2.0 configure: Using install prefix: /usr/local configure: Binaries installed in: /usr/local/bin configure: Libraries installed in: /usr/local/lib/HaskellGPC-0.0.1/ghc-6.6 configure: Private binaries installed in: /usr/local/libexec configure: Data files installed in: /usr/local/share/HaskellGPC-0.0.1 configure: Using compiler: /usr/bin/ghc configure: Compiler flavor: GHC configure: Compiler version: 6.6 configure: Using package tool: /usr/bin/ghc-pkg configure: Using ar found on system at: /usr/bin/ar configure: Using haddock found on system at: /usr/bin/haddock configure: No pfesetup found configure: Using ranlib found on system at: /usr/bin/ranlib configure: Using runghc found on system at: /usr/bin/runghc configure: No runhugs found configure: No happy found configure: No alex found configure: Using hsc2hs: /usr/bin/hsc2hs configure: Using c2hs: /usr/bin/c2hs configure: No cpphs found configure: No greencard found marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ ./Setup.hs build Preprocessing library HaskellGPC-0.0.1... Building HaskellGPC-0.0.1... [1 of 1] Compiling Algebra.Geometric.Gpc ( Algebra/Geometric/Gpc.hs, dist/build/Algebra/Geometric/Gpc.o ) /usr/bin/ar: creating dist/build/libHSHaskellGPC-0.0.1.a marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ ./Setup.hs clean cleaning... marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ find | grep -v _darcs . ./AUTHORS ./Algebra ./Algebra/Geometric ./Algebra/Geometric/Gpc.chi ./Algebra/Geometric/Gpc.chs ./Algebra/Geometric/Gpc.h ./COPYING ./README ./Setup.hs ./ToDo ./dist ./haskellgpc.cabal ./send.sh marcot@quindinho:~/codigo/haskell/haskellgpc/haskellgpc$ Thanks. -- malebria Marco Túlio Gontijo e Silva Correio (MSN): malebria(a)riseup.net Jabber (GTalk): malebria(a)jabber.org Ekiga: malebria(a)ekiga.net IRC: malebria(a)irc.freenode.net malebria(a)irc.oftc.org Skype: marcotmarcot Telefone: 33346720 Celular: 98116720 Endereço: Rua Paula Cândido, 257/201 Gutierrez 30430-260 Belo Horizonte/MG Brasil

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