Re: User-Defined Operators (ad-hoc overloading)

[Christian Maeder]

Andrew J Bromage wrote:
As a matter of interest, is there a known worst-case complexity for
the precomputation required by Earley's algorithm to handle arbitrary
CFGs?
Earley's algorithm handles exactly arbitrary (in particular ambiguous) 
CFGs without precomputation.

see i.e. Aho,Ullman, "The Theory of Parsing, Translation, and Compiling" 
Vol.1, 1972

I don't believe that expected-case O(N^3) behaviour counts as "not
hard", even if it's not exponential.  These things have a way of
biting you when you least expect it.
Right, this (worst-case) behaviour may be bad, but that can only be (and 
partly was already) answered in practice. (A constant factor or constant 
overhead for precomputations can spoil anything.)

Christian

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Announce: wxhaskell: macOSX binaries and bugfix.

[Daan Leijen]

Two announcements regarding wxHaskell:


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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HToolkit 1.0 released

[Krasimir Angelov]

+---+
|ANNOUNCEMENT: HToolkit 1.0 released  
 |
+---+
| author: Krasimir Angelov
 |
| www   : http://htoolkit.sourceforge.net 
 |
| forum :
mailto://[EMAIL PROTECTED] |
+---+

 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 çà 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

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Re: Announce: wxHaskell, a portable GUI library.

[Abraham Egnor]

Given your impending vacation, this might not be the best time to mention
it, but...

I can't seem to download any files for wxHaskell from sourceforge; this is
probably a misconfiguration on their part, but I thought it best to let
you know as well.

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varying function by typeclass

[Abraham Egnor]

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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