[GAP Forum] [GAP Support] I think I found a bug.

[Max Neunhoeffer]

Dear Lisette,

as far as I see there is nothing incorrect. The documentation of
"Orbit" says that the result is the *list of all images* and not the
*set of all images*. Therefore it is OK that the list is not sorted.
The order of the elements you see depends on the starting point and
the generators of your group in general. Also, it is not guaranteed by
the documentation.

If you need the orbit as a set just use
  Set(Orbit(S,a))
instead.

I hope this is useful, if there are any other questions please do not
hesitate to ask again.

Best regards,
  Max Neunhoeffer

On Tue, Jul 13, 2010 at 01:28:43PM +0200, Lisette Brillemans wrote:
> LS
> 
> 
> I'm using the latest version of GAP on linux and have read all the
> bugfixes but didn't find this one:
> 
> If you type this:
> 
> 
> S:=SymmetricGroup(9);
> for a in [1..9] do
>  Print(Orbit(S,a),"\n");
> od;
> 
> The output is as follows:
> 
> [1,2,3,4,5,6,7,8,9]
> [2,3,1,4,5,6,7,8,9]
> [3,4,5,6,7,8,9,1,2]
> [4,5,6,7,8,9,1,2,3]
> [5,6,7,8,9,1,2,3,4]
> [6,7,8,9,1,2,3,4,5]
> [7,8,9,1,2,3,4,5,6]
> [8,9,1,2,3,4,5,6,7]
> [9,1,2,3,4,5,6,7,8]
> 
> The problem is the second line:
> 
> [2,3,1,4,5,6,7,8,9]
> 
> Which, according to me, is incorrect.
> 
> But apart from that GAP is a splendid program which possibilities still
> surprise me everyday.
> 
> With regards.
> 
> Lisette Brillemans
> Rotterdam, Holland
> 
> 
> _______________________________________________
> Support mailing list
> Support at gap-system.org
> http://mail.gap-system.org/mailman/listinfo/support

-- 
Max Neunhoeffer              http://www-groups.mcs.st-and.ac.uk/~neunhoef/
> > > > > > > > > > >  May the Source be with you! < < < < < < < < < < < < 
The University of St Andrews is a registered Scottish charity: No SC013532