Path: news.daimi.aau.dk!not-for-mail
From: Erik Ernst <eernst@fraxinus.daimi.aau.dk>
Newsgroups: comp.lang.beta,daimi.beta,comp.object,comp.lang.eiffel,comp.lang.sather,comp.lang.python
Subject: gbeta v0.5 released - free (g)BETA interpreter (GPL)
Followup-To: comp.lang.beta
Date: 18 Dec 1997 05:20:38 +0100
Organization: DAIMI, Computer Science Dept. of Aarhus Univ.
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Keywords: free BETA interpreter, GPL, OO programming language generalized
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Announcement of
			     ------------
			      gbeta v0.5
			     ------------


What is it?	
		gbeta is an interpreter of a generalized version of
		the BETA programming language.  BETA is a modern,
		object-oriented language in the Scandinavian
		tradition. It delivers great expressive power using
		only few language constructs: a useful, simple, and
		clean language.  It has a strong static typesystem and
		static name binding, general block-structure (nesting,
		true closures), virtual types, real type variables,
		expressive method combination, and a very flexible and
		expressive module and visibility control system.
		
		gbeta generalizes the BETA language in fundamental
		ways.  Firstly, the type system is based on
		constraints (the type denoted by a declaration is the
		most general class satisfying the constraints).
		Secondly, object metamorphosis is supported (take an
		existing object, apply a class as a constraint, and
		the object dynamically specializes ("inherits") such
		that it becomes an instance of a derivation of that
		class).  Thirdly, classes can be constructed at
		run-time (without sacrificing type correctness) and
		classes can be inherited from even if they are not
		known before run-time, such as with virtual classes or
		class variables.

		The constraint based inheritance system can e.g. be
		exploited to construct constraint graphs of types: set
		up a design in your library code such that a user of
		the library can "pull a handle" by adding a few
		constraints.  The changes propagate throughout your
		library code and allow for an ordered and maintainable
		specialization for a given application.

Changes since v0.13

		manymanymany, mostly concerning the usage, and fixing
		bugs; the language definition hasn't changed

Where can I get it?

		http://www.daimi.aau.dk/~eernst/gbeta/, (which refers to
		ftp://ftp.daimi.aau.dk/pub/empl/eernst/gbeta-0.5/...)

What platforms are supported?

		Linux (2.x.y/ELF)
		SunOS 5.5.1 (Solaris)
		HP-UX 9 (probably works on HP-UX 10)
		SGI IRIX 6 (6.2, 6.3, 6.4)
		Windows NT/95 (semi-supported!)

		Integration with Emacs (isn't that a platform? ;-)

What can I get?

		Source code (GPL), in BETA
		Binaries for the above platforms
		Soon: packaged web-site, for quick local browsing

WWW site?
		http://www.daimi.aau.dk/~eernst/gbeta/ contains
		many things, including a tutorial and an
		introduction to advances issues

Collaboration?
		Yes, please!  If you want to develop your own variant,
		or help me make this one faster/better, don't hesitate
		to contact me.  Suggestions are welcome, too.

--
Erik Ernst                            eernst@daimi.aau.dk
Computer Science Department of Aarhus University, Denmark