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<!--  intro.xml             KAN documentation             Chris Wensley  -->
<!--                                                    & Anne Heyworth  -->
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<!--  $Id: intro.xml,v 0.97 2008/11/18 gap Exp $                         -->
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  <!-- <M>Id: intro.xml,v 0.97  Exp <M> -->

<Chapter Label="intro">
<Heading>Introduction</Heading>

The &kan; package started out as part of Anne Heyworth's thesis 
<Cite Key="anne-thesis" />}, and was designed to compute 
induced actions of categories (see also <Cite Key="BrHe" />). 
<P/>
This version of &kan; only provides functions for the computation of
normal forms of representatives of double cosets of finitely presented groups, 
and is made available in support of the paper <Cite Key="BrGhHeWe" />. 
Existing methods for computing double cosets in &GAP; are described 
in <Cite Key="SteveL" />.
<P/>
The package is loaded into &GAP; with the command
<Example>
<![CDATA[
gap> LoadPackage( "kan" ); 
]]>
</Example>

This version of &kan; has been prepared for &GAP; 4.4.11. 
Some of the functions in the <Package>automata</Package> package 
are used to compute word acceptors and regular expressions 
for the languages they accept.
<P/>
The <Package>kbmag</Package> package is also used 
to compute a word acceptor of a group <C>G</C> 
when <C>G</C> has no finite rewriting system. 
If <Package>kbmag</Package> is not available 
(the user is not on a UNIX system, or the C-programs have not been compiled), 
the file <File>dckbmag.gi</File> will not be read, 
so methods for the functions detailed in section 2.4.1 will not be available.
<P/>
The information parameter <C>InfoKan</C> takes default value <C>0</C>.
When raised to a higher value, additional information is printed out.
<P/>
Once the package is loaded, it is possible to check the installation 
is correct by running the test suite of the package with the
following command.
(The test file itself is <F>tst/kan_manual.tst</F>.)
<Example>
<![CDATA[
gap> ReadPackage( "kan", "tst/testall.g" );
+ setting AssertionLevel to 0 to avoid recursion in Automata
+ Testing all example commands in the Kan manual
+ GAP4stones: 6
true
]]>
</Example>
(If <Package>kbmag</Package> is not loaded then a collection of 
error lines for Example 3 will be printed out.)
<P/>
Please send bug reports, suggestions and other comments to the second author.
<P/>
The &kan; package is subject to the &GAP; copyright regulations as 
detailed in the copyright notice in the &GAP; manual.

</Chapter>