[GAP Forum] Cosets and intersection

[Mathieu Dutour]

Dear Gap forum,

Suppose that xH is a right coset and G is a group.
Then the intersection of xH and G is:
--either emptyset [ ]
--or a right coset of the form y (H inter G)

One may want that the corresponding gap command
take this into account, but this is not the case:
V:=RightCoset(SymmetricGroup(4), (4,5));
Intersection(SymmetricGroup(5), V);
returns a list of 24 elements.

Is there a way to avoid the creation of a list?
As a matter of fact, I just want to know if the
intersection is empty or not and if not to have
one element in the intersection.

  Mathieu

-- 
Mathieu Dutour Sikiric		Researcher in Math
Tel. (+972)2 65 84 103		and Computer Science
Fax. (+972)2 56 30 702		Einstein Institute of Mathematics
E-mail: Mathieu.Dutour at ens.fr	Hebrew University of Jerusalem
http://www.liga.ens.fr/~dutour	Israel