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Dear forum readers,

Paul Brown asks:

Has anyone out there written a routine that interfaces GAP and the

automatic groups software by D. Epstein, D. Holt, and S. Rees?If not, I will very likely attempt to do so myself, and I would

cheerfully share any successes if the matter is or general interest.

to which Werner Nickel replies:

Here is a short answer to the question. Since Derek Holt is a reader

of this forum he might want to give a more detailed answer.Derek has a new version of the automatic group software called KBMAG.

It includes a GAP interface. It can be obtained via Derek's web home

page http://www.maths.warwick.ac.uk/~dfh/ or from the Warwick

mathematics ftp server ftp.maths.warwick.ac.uk:/people/dfh/ via

anonymous ftp.

This is just to confirm what Werner says.

The current interfact of KBMAG with GAP is a little rudimentary, but it

can be made to work.

After making the package KBMAG, you go into a directory containing some

GAP library files, start up GAP and read in these files.

You then define a finitely presented group G, say, in GAP, and from it you

calculate an object known as a rewriting-system, which the KBMAG programs

use as input. You can then call the automata program as an external program

from within GAP. If successful, you can reduce words in G to their

normal form, and enumerate the set of words in normal form (usually

up to a given word-length). You can also examine the finite state automata

associated with the automatic structure of G from within GAP if you want to.

There are plans to make KBMAG into an official GAP share package, but some

details of the interface remain to be sorted out, so this may take a few

more months yet.

In the mean time, it would be very helpful if you could try out this

interface and let me know of any problems you have setting it up, anything

that doesn't appear to behave the way you think it should, and any

additional facilities that you feel could be usefully provided.

Regards,

Derek Holt.

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