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1 Preface

The XMod package provides functions for the computation with finite

It is loaded with the command

gap> LoadPackage( "xmod" ); 

XMod was originally implemented in 1997 using the GAP 3 language. 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 2.006, released on September 6th 2004.

Many of the function names have been changed during the conversion, for example ConjugationXMod has become XModByNormalSubgroup. For a list of name changes see the file names.pdf in the doc directory.

  • InfoXMod V

    In order that the user has some control of the verbosity of the XMod package's functions, an InfoClass InfoXMod is provided (see Chapter Info Functions in the GAP Reference Manual for a description of the Info mechanism). By default, the InfoLevel of InfoXMod is 0; progressively more information is supplied by raising the InfoLevel to 1, 2 and 3, e.g.

    gap> SetInfoLevel( InfoXMod, 1); #sets the InfoXMod level to 1
    

    The following test file (from the ``xmod'' directory) runs all the manual commands.

    gap> ReadTest("tst/xmod_manual.tst");
    + Testing constructions of crossed modules and cat1-groups
    + GAP4stones: 0
    true
    

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    XMod manual
    September 2004