README for gbeta
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Since these files are under the GNU GENERAL PUBLIC LICENSE, the source
files are made available to you per the terms of that copyright.
For more information refer to the file COPYING, which you should have
received as part of this package; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

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This is an implementation of the programming language gbeta, which is
a generalization of the language BETA.  For more information about
gbeta and this implementation, please take a look at the web site:

  http://www.cs.au.dk/~eernst/gbeta/

A snapshot of this site is also distributed in this package, in the 
directory html.  Details about installation and getting started are
also given in the pages of this web site.

The language gbeta is (essentially) backwards compatible with the 
language BETA, which is a direct successor to the first OO language,
Simula.  To learn more about the language BETA, check out this site:

  http://www.cs.au.dk/~beta/

Compared to BETA, gbeta is built on a more general semantic foundation 
(based on full-fledged mixins), and this enhances the expressive 
power and flexibility of the language and its type system.  For 
instance, the combination of (generalized) virtual attributes and 
general block structure gives rise to a phenomenon which is called 
propagating combinations or deep mixin composition.  More details
can be found in the paper "Propagating Class and Method Combination",
Proceedings ECOOP'99.  Some important properties of the type system
are presented in the paper "Family Polymorphism", Proceedings ECOOP'01,
and others are presented in "Higher-Order Hierarchies", Proceedings 
ECOOP'03.  Soundness of a small core of the static analysis is shown
in 'A Virtual Class Calculus', POPL 2006 (joint work with Klaus
Ostermann and William Cook).

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There is a man page in the distribution (the file doc/gbeta.1) which 
documents the command line arguments/options, as well as the command
language which is used during interactive sessions.

Feed back about gbeta is highly appreciated, both about the language
design effort that it incarnates and its implementation.  You are
welcome to perform experiments based on gbeta---in that case, do not 
hesitate to contact me for help or discussions!  The USENET news 
group comp.lang.beta would also be an appropriate place for 
such discussions.

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This implementation of gbeta is written in the Mjolner BETA System (an
implementation of BETA with a compiler, a structure editor, a
debugger, and much more).  This means that you would need the Mjolner
BETA System in order to recompile gbeta.

The Mjolner BETA System used to be for sale only, but it can now be
downloaded for free, so you can compile gbeta and experiment with
variations as you like.

Version 1.9.11 of gbeta was developed with release 5_2_2c of the Mjolner
BETA System, but probably a number of other releases will work just
as well.

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                                        -- Erik Ernst 
                                           eernst@cs.au.dk