Dear Gap-Forum,

Thomas HGaeberlen wrote:

> In Gap3 there is a function IsomorphismAgGroup( series ) where series was a
> (subnormal) series for a group G. IsomorphismAgGroup( series ) returns an
[...]
> In Gap4 I can not find such a function, and

`IsomorphismAgGroup' was not ported since it turned out to be not needed:
In GAP3 all calculations are with respect to (what we would call in GAP4
the) `FamilyPcgs'. Thus it is necessary to create a new group, whenever one
changes the series and this is time- and memory consuming.
In GAP4 we have the more general concept of pcgs which permits to choose a
particular series without having to generate a new group and to translate
the problem.

You can simulate `IsomorphismAgGroup' by first forming a pcgs with the
desired generators and then using `PcGroupWithPcgs' to create a new group,
whose `FamilyPcgs' is isomorphic:

gap> pcgs:=PcgsByPcSequence(FamilyObj( () ), [(1,2),(1,2,3)]);
[ (1,2), (1,2,3) ]
gap> g:=PcGroupWithPcgs(pcgs);
<pc group of size 6 with 2 generators>

I hope this is of help,

Alexander Hulpke

-- Colorado State University, Department of Mathematics,
Weber Building, Fort Collins, CO 80523, USA
email: hulpke@math.colostate.edu, Phone: ++1-970-4914288