## &XMod;

Crossed modules and cat1-groups in &GAP;
Version 2.12
Murat Alp malp@dumlupinar.edu.tr

          Dumlupinar Universitesi,

          Fen-Edebiyat Fakultesi, Matematik Bolumu

          Merkez Kampus, Kutahya, Turkey.

Chris Wensley c.d.wensley@bangor.ac.uk http://www.bangor.ac.uk/~mas023/

          School of Computer Science, Bangor University,

          Dean Street, Bangor, Gwynedd, LL57 1UT, U.K.

November 2008

The XMod package provides functions for computation with finite crossed modules and cat1-groups, and morphisms of these structures; finite pre-crossed modules, pre-cat1-groups, and their Peiffer quotients; derivations of crossed modules and sections of cat1-groups; the actor crossed square of a crossed module; and crossed squares and their morphisms (experimental version).

&XMod; was originally implemented in 1997 using the &GAP;3 language. when the first author was studying for a Ph.D. in Bangor.

In April 2002 the first and third parts were converted to &GAP;4, the pre-structures were added, and version 2.001 was released. The final two parts, covering derivations, sections and actors, were included in the January 2004 release 2.002 for {\GAP}~4.4.

The current version is 2.12, released on 24th November 2008.

Bug reports, suggestions and comments are, of course, welcome. Please contact the second author at c.d.wensley@bangor.ac.uk.

&copyright; 1997-2008 Murat Alp and Chris Wensley
This `xmod` package is released under the GNU General Public License (GPL). This file is part of `xmod`, though as documentation it is released under the GNU Free Documentation License (see http://www.gnu.org/licenses/licenses.html#FDL).

xmod
is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

xmod
is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with `xmod`; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.

For more details, see http://www.fsf.org/licenses/gpl.html.

This documentation was prepared with the `GAPDoc` package of Frank L\"ubeck and Max Neunh\"offer.

The first author wishes to acknowledge support from Dumlupinar University and the Turkish government.
<#Include SYSTEM "intro.xml"> <#Include SYSTEM "gp2obj.xml"> <#Include SYSTEM "gp2map.xml"> <#Include SYSTEM "gp2up.xml"> <#Include SYSTEM "gp2act.xml"> <#Include SYSTEM "gp2ind.xml"> <#Include SYSTEM "gp3obj.xml"> <#Include SYSTEM "util.xml"> <#Include SYSTEM "history.xml">