I have discoverd a useful trick for multiplying transformation
represented as image liists in GAP. Since a number of people have
been enquiring about this and related subjects I thought it might be
appropriate to mention it here.

The obvious way to multiply lits images1 and images2,
returning a list imagesProd is something like

imagesProd := [];
for i in images1 do
Add(imagesProd,images2[i]);
od;

However the same result can be achieved rather faster by

imagesProd := images2{images1};

where the loop is provided by the kernel.

Steve