This is the README file for the xmod share package, version 1.3.1, 13/ 1/97
intended as a share package for the GAP group theory system, and developed
at the University of Wales, Bangor, by Chris Wensley and Murat Alp.

A compressed version of the files is available as  xmod131.tar.gz
on the GAP ftp incoming directory.  This file should be copied to
your system  gap/  directory, then decompressed as follows:
   .../gap> gunzip xmod131.tar.gz
   .../gap> tar -xvf xmod131.tar
A directory  .../gap/gap3r4p3/pkg/xmod  is then created, together with
subdirectories  /lib, /doc, /tst.

After decompression, edit line 25 of the file init.g in directory ../xmod
so that the directory name fits that of your own installation.  
When running GAP it is then sufficient to:
   gap> RequirePackage( "xmod" );

The package comprises the following files:

in the .../xmod  directory :-
   init.g       header file to load the rest,
                this README file,

in subdirectory /lib :-
   xmod.g       for working with crossed modules,
   xmodmor.g    functions for morphisms of crossed modules,
   cat1.g       for functions with cat1-groups,
   cat1mor.g    functions for morphisms of cat1-groups,
   cat1list.g   data file of cat1-groups of size up to 47,
   deriv.g      for derivations and sections,
   induce.g     calculations of induced crossed modules,
   dispatch.g   dispatcher functions are all collected here,
   util.g       various utilities,
(the following three files should not be necessary with GAP 3.4.4 :- )
   felsch.g     modified version of the standard file: fptietze.g
   mytz.g       some more tietze functions
   pact.g       corrected PresentationAugmentedCosetTable (from fpsgpres.g)

in subdirectory /doc :-
   xmod.tex                                - LaTeX file for the XMOD chapter
   xmmanual.tex, xmmanual.dvi, xmmanual.ps - stand-alone version of the chapter
   xmabout.tex, xmabout.dvi, xmabout.ps    - short introduction to the package
                                             (15 pages rather than 80 pages)
   enumcat1.dvi, enumcat1.ps               - draft version, UWB preprint 96.05

in subdirectory /tst :-
   xmod.t                                  - GAP file which contains all
                                             the example code in the manual

The file xmmanual.tex contains the standard header material from the main
GAP manual.tex.  To LaTeX the stand-alone chapter yourself use:
   > latex xmmanual           (at least twice)
   > dvips -r xmmanual
and print the resulting PostScript file to a suitable printer.

To include the XMOD chapter in the complete manual:
 .  copy  xmod.tex  and  xmod.aux  to directory  ../gap/gap3r4p3/doc,
 .  add the line:   \Include{xmod}   after the other  \Include{...}  commands
    in the file  manual.tex  (in the same  ../doc  subdirectory),
 .  .../gap3r4p3/doc latex manual  (at least twice).
The GAP help system will then know about functions in this package.
   
This is still an experimental package, under continuous development.
If you find a use for this package, please email to: 
                        c.d.wensley@bangor.ac.uk
If you require a reference for this package, please cite:
  Enumeration of cat1-groups of low order,
  U.W.Bangor Preprint 96.05 (1996) 1-15.
