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

[Lisette Brillemans]

Dear Max,

You're right. If you look at it this way you can say the answer given is
of course entirely correct. However I am still wondering why the
ordering of the second line in my example is somehow "unlogical"
compared to the other lines. Is there some inconsistency in the
algorithm? (I mean, why only when a = 2?)
But if that's not the case then I apologize.

Best regards,

Lisette

> 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
> > 
> > 
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