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Announce: wxHaskell, a portable GUI library.
by Daan Leijen 23 Jul '03

23 Jul '03

Announcement: wxHaskell 0.1 --------------------------- <http://wxhaskell.sourceforge.net> wxHaskell is a new portable GUI library for Haskell. The goal of the project is to provide an industrial strength portable GUI library, but without the burden of developing (and maintaining) one ourselves. wxHaskell is therefore build on top of wxWindows -- a comprehensive C++ library that is portable across all major GUI platforms; including GTK, Windows, X11, and MacOS X. Furthermore, it is a mature library (in development since 1992) that supports a wide range of widgets with native look-and-feel, and it has a very active community (ranked among the top 25 most active projects on sourceforge). Since most of the interface is automatically generated from the wxEiffel binding, the current release of wxHaskell already supports about 75% of the wxWindows functionality -- about 2500 methods in 500 classes with 1200 constant definitions. wxHaskell has been build with GHC 6.0 on Windows, MacOS X and Unix systems with GTK. A binary distribution is available for Windows (and we are working on a binary release for MacOS X). And even if you don't intend to write GUI's yourself, it will be fun to check out the screenshots at <http://wxhaskell.sourceforge.net>. All the best, Daan Leijen.

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varying function by typeclass
by Abraham Egnor 23 Jul '03

23 Jul '03

I have a function that takes, among other things, a (wrapped) generic type, i.e. "forall a. a". My function can possible produce an error message; is there any way to set up the function so that if the type is an instance of Show include the value along with the error message? I can't think of any, and this is honestly the first time I've been directly frustrated by Haskell's typesystem, so it's bugging me more than it might otherwise. Any suggestions? Abe

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HToolkit 1.0 released
by Krasimir Angelov 22 Jul '03

22 Jul '03

+-------------------------------------------------------+ | ANNOUNCEMENT: HToolkit 1.0 released | +-------------------------------------------------------+ | author: Krasimir Angelov | | www : http://htoolkit.sourceforge.net | | forum : mailto://htoolkit-users@lists.sourceforge.net | +-------------------------------------------------------+ The HToolkit is a package primary intended for development and designing of platform independent graphical user interface. The package gives you an abstract API for many platforms while for each platform are used only libraries which are native for the platform. This release supports only Windows and Linux platforms, but the chosen model allows support for other platforms. Under Windows the package use only native Win32 API and under Linux are used GTK/GNOME libraries. The difference between HToolkit and most of other libraries is that the latter uses only controls and dialog elements which are native under target plaform. The advantage of this is that the application looks like more native. Similar model is chosen from wxWindows for C++ and SWT for Java. The disadvantage of this libraries is that they are written in high level languages and this makes difficult to use them from other languages. The main part of HToolkit is written in C and the used model simplifies FFI interface between the HToolkit core and high level languages (most languages proposes only FFI to C). The current release gives only interface to Haskell. There is plan to build GUI libraries based on HToolkit core for C#, SmallTalk and Python. HToolkit for Haskell -------------------- HToolkit �� Haskell is divided in two libraries: GIO and Port. The Port library is a low level interface and it is not intended to be used for development. Port includes modules written in C and FFI for them written in Haskell. GIO is a high level API intended for application development. The HToolkit is divided in high and low level in order to allow development of experimental high level interfaces without sacrifice of low level API. For the time beings HToolkit gives all features proposed from ObjectIO with exception of ToolBar and CustomControl. Many of ObjectIO features are extened, but there are also many new features which does't exists in ObjectIO. Relatively all controls supported from wxHaskell are supported from HToolkit. Still missing controls like Panel, Gauge and Notebook but they are planned for the next release of HToolkit. Currently the HToolkit is the only package for Haskell which allows to create, load, edit and save images at runtime. Another interesting feature is that the toolkit allows to display icons in menu items. The feature is native under GTK/GNOME but is hard to implement under Windows. NOTE: The ToolBar support is included in the package but still doesn't work. This is because under Windows it still requires a bit of development while under GTK/GNOME the package uses the new API for GtkToolbar which will be part of the next GTK release. Krasimir Angelov __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free, easy-to-use web site design software http://sitebuilder.yahoo.com

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Announce: wxhaskell: macOSX binaries and bugfix.
by Daan Leijen 22 Jul '03

22 Jul '03

Two announcements regarding wxHaskell: <http://wxhaskell.sourceforge.net> 1) I have created a binary release for MacOS X. Installation details can be found on the download page. 2) I have fixed a small bug in the configuration script for Linux. The source release has been updated. (and I promise I won't do that again as I go tomorrow on a holiday for two weeks :-) All the best, Daan.

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Superclass Defaults
by Ashley Yakeley 21 Jul '03

21 Jul '03

This seems to be a frequently requested feature of Haskell: the ability to declare default members in a superclass for a particular class. Here's an example: class Functor f where fmap :: (a -> b) -> f a -> f b class (Functor f) => Monad f where ... The idea is that it should be possible to declare a type an instance of both Monad and Functor without having to provide a definition for 'fmap'. Instead, a default would be used: fmap ab fa = fa >>= (return . ab) Well I don't doubt this would be a very useful extension to the Haskell language: indeed it would eliminate code in all my Haskell projects. But before we can propose this, we have to work out what the syntax would look like. Here are some properties I think such a mechanism should have: 1. It should be possible to declare types as instances of Monad and Functor with a different definition of fmap overriding the default. 2. It should be possible to declare another subclass of Functor that also has a default for fmap. 3. The members of any existing class should be subclass-defaultable in another module; i.e., no special syntax should be involved in the class declaration of the superclass. 4. It should be possible to distinguish between different appearances of the same class in the superclass context. For instance: class C a where c :: Int -> a class (C a,C b,C (a -> b)) => D a b where ... Any ideas? -- Ashley Yakeley, Seattle WA

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HScheme Status
by Ashley Yakeley 20 Jul '03

20 Jul '03

HScheme, my Scheme interpreter, is mostly done. I've put up the latest build as a CGI program, together with lists of features and issues standing before release. See: <http://hscheme.sourceforge.net/> Curiously (or not), parsing is by far the biggest time hit. I hope to do a bit more profiling to see if I can find out just why. -- Ashley Yakeley, Seattle WA

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RE: referring to deeply embedded definitions
by Hal Daume 18 Jul '03

18 Jul '03

Please ignore my stupid question :) -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume > -----Original Message----- > From: Hal Daume > Sent: Friday, July 18, 2003 10:23 AM > To: haskell(a)haskell.org > Subject: referring to deeply embedded definitions > > > Suppose I have: > > > module M1 where > > import M2 > > foo = 'a' > > and > > module M2 where > > import M3 > > and > > > module M3 where > > foo = True > > Now, inside M1, I want to write something like: > > > bar = if M2.foo then M1.foo else 'b' > > or > > > bar = if M3.foo then M1.foo else 'b' > > but neither of these is valid. Is there any way to get at > the definition from M3? > > - Hal > > -- > Hal Daume III | hdaume(a)isi.edu > "Arrest this man, he talks in maths." | www.isi.edu/~hdaume >

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referring to deeply embedded definitions
by Hal Daume 18 Jul '03

18 Jul '03

Suppose I have: > module M1 where > import M2 > foo = 'a' and > module M2 where > import M3 and > module M3 where > foo = True Now, inside M1, I want to write something like: > bar = if M2.foo then M1.foo else 'b' or > bar = if M3.foo then M1.foo else 'b' but neither of these is valid. Is there any way to get at the definition from M3? - Hal -- Hal Daume III | hdaume(a)isi.edu "Arrest this man, he talks in maths." | www.isi.edu/~hdaume

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How to use functions in dll file in Haskell program?
by Liu Junfeng 18 Jul '03

18 Jul '03

Hi， If there is a function named "func" with type a->b in a win32 dll file. In Hugs use the primitive declaration: ------------------------------- primitive prim_func :: a -> b func = prim_func ------------------------------- Then the func can be exported to be used in other modules. The question is how to do it in GHC? Cheers, Liu Junfeng liujf(a)softhome.net 2003-07-18

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Announce: buddha 0.9 released
by Bernard James POPE 18 Jul '03

18 Jul '03

Announcing the release of buddha version 0.9 -------------------------------------------- www.cs.mu.oz.au/~bjpop/buddha Buddha is a declarative debugger for Haskell 98. It is based on program transformation and relies on GHC version 5.04 or greater (but not version 6 yet). It also needs GHC's libraries compiled for profiling. New in this release: - support for record syntax - debugging versions of all the standard Haskell 98 libraries - some minor improvements in the transformation (for efficiency and usability) Features still missing: - mutually recursive modules, - deriving Ix. Platforms supported: - tested on linux - (should work in any unix-like environment), - not tested on Windows (sorry). Note that buddha does not yet work with GHC version 6.0. This will be fixed in coming releases. Cheers, Bernie.

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