Thanks everyone for your helpful posts, which came in overnight. We have the classical groups (GL, SL,...) from GAP as groups of matrices (in a natural way) and we have the projective versions (PGL, PSL,...) from GAP as permutation groups. Testing indicates you cannot switch it around (projective versions as matrices, plain versions as groups of matrices, from GAP). Maybe GAP has an efficient conversion between the two implementations, but I'm not seeing it. We have an interesting, but incomplete, collection of permutation groups. So it seems that we have implementations tied tightly to the groups themselves right now. I was suggesting loosening this up some (though that was not the point of my question).
Simon - I was not aware of "parents with multiple realisations", so I will pursue that. Thanks, Little Nicolas, for the introduction. It will be helpful as I am still at level 0.5 with categories. (And I'm glad to see that *somebody* in France is working during the holiday season!) Finally, Javier, I have not kept up with the group presentations ticket, which will be a great addition, so I'm glad to see that progressing. Rob -- -- To post to this group, send an email to [email protected] To unsubscribe from this group, send an email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
