Dear Forum,

Paul Benjamin asked about computing the Green relations for semigroups
of partial 1-1 functions in gap.

As far as I know there is no such package, but there are several
softwares computing Green relations of semigroups of functions, none
of them in gap.

I can cite four such programs:

automat - developed by Hansel and Champarnaud in Paris, they published
a paper about it. Contact Georges Hansel <gh@litp.ibp.fr> for more
details.

tor - a program written by myself. It is in Turbo Pascal (it has
been translated to C with the help of a utility program).
Unfortunately, the program is written in Portuguese, the
documentation is VERY scarce and also in portuguese. In any case it
is available from me (AS IS).

amore - a system developed in Aachen and Kiel. Contact Wolfgang
Thomas <wt@informatik.uni-kiel.dbp.de> for more information.

automata - a Mathematica package developed by Klaus Stutner; the
package is available from mathsource.wri.com in the Applications/Complexity
directory, as item 0205-197 "Automata".

There is also a version of tor, called lim, which computes the Green
relations for semigroups of matrices over a particular finite
semiring.

Yours,

Imre Simon