Dear Members of the GAP Forum,

It is a pleasure to announce the acceptance of XGAP (Version 4),
a GAP4 share package by Frank Celler and Max Neunhoeffer at
Lehrstuhl D fuer Mathematik of the University of Aachen. XGAP
provides a graphical user interface, allowing, for certain
applications, a menu oriented interactive dialog with GAP4.
Function calls, which in a usual interactive GAP4 session are
typed in from a keyboard, are replaced by mouse-clicks. XGAP
graphic sheets picture mathematical objects, such as groups,
and relations between them, by graphical objects, such as circles,
rectangles and lines.

Its major applications include the graphical representation of
(partial) subgroup lattices, for finite groups as well as for
finitely presented groups. Through a link to Michael Ringe's
Meat-Axe, submodule lattices of modules for finite dimensional
algebras can also be handled.
But XGAP is not limited to the display of lattices. It can be
used to implement your own applications for visualization of
objects and structures. The object oriented design of GAP4 and
XGAP makes re-usage of existing code particularly easy. A typical
example of this is the interactive Todd-Coxeter algorithm currently
ported from GAP3 to GAP4 and extended by Volkmar Felsch.

XGAP comes along with a comprehensive on-line manual, containing
clear installation instructions and a wealth of examples to play
with in order to get used to the system.

XGAP requires a Unix type operating system with the X window system
Version 11 Release 5 or higher. It can be obtained from the web page

http://www-gap.dcs.st-and.ac.uk/~gap/Info4/share.html

and from the GAP4 share packages ftp directory:

ftp://ftp-gap.dcs.st-and.ac.uk/pub/gap/gap4/share

Questions concerning the package or its installation should be
addressed to:

Max.Neunhoeffer@Math.RWTH-Aachen.DE.

Gerhard Hiss
August 2, 1999