[GAP Forum] Different output from Action function in GAP 4.5.5

[Burkhard Höfling]

On 2012-09-25, at 00:10 , William DeMeo wrote:

> Dear Forum,
> 
> I recently tried to reproduce some GAP output for an example that
> appears in a manuscript that was recently accepted in final form by
> the publisher.  However, using GAP 4.5.5 I now get different output
> than what appears in my paper.  (I wrote the paper while using GAP
> 4.4.12.)

Seems that GAP 4.5.5 uses a different list of elements when computing the action. If you use an explicit list of elements, you'll get the previous action:

gap> g:=Group([(1,2),(1,2,3)]);;
gap>  G := Action (g,[ (), (1,2,3), (1,3,2), (2,3), (1,2), (1,3) ], OnRight);
Group([ (1,5)(2,4)(3,6), (1,2,3)(4,5,6) ])
gap> for b in AllBlocks(G) do Print(Orbit(G,b,OnSets)-1,"\n"); od;
[ [ 0, 4 ], [ 1, 5 ], [ 2, 3 ] ]
[ [ 0, 1, 2 ], [ 3, 4, 5 ] ]
[ [ 0, 3 ], [ 1, 4 ], [ 2, 5 ] ]
[ [ 0, 5 ], [ 2, 4 ], [ 1, 3 ] ]

Actually, you could have used `Enumerator(G)' instead of the elements list, but then that enumerator could also change in the future.

Cheers

Burkhard.