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Dear GAP-Forum,

to compute the intersections of the left cosets of the centre of a

group G with the G's derived subgroup I tried

gap> Glcs := LeftCosets( G, Centre(G));;

gap> List( Glcs, c -> Intersection( c, DerivedSubgroup(G) ) );

Applied to G=SymmetricGroup(4) these two lines did their job pretty

good. But why do they fail, when I define G as the cyclic group of

order 7 ?

In spite of any result here I only got the following error-message:

Error, usage: RightCoset( <U> [, <g>] ) in

RightCoset( arg[1] ) called from

Coset( G ) called from

GroupOps.Intersection( G, H ) called from

D.operations.Intersection( I, D ) called from

Intersection( c, DerivedSubgroup( G ) ) called from

...

I also tried calling

gap> List( Gcls ........, Elements( DerivedSubgroup(G) ) ... );

~~~~~~~~

and because of the fact that this did not yield an error-message,

but the correct result, I think the upper two lines won't work iff

G is an abelian group iff DerivedSubgroup(G) is trivial and so has

an empty generator set. Am I right?

Thanks in advance,

Mathias

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