[GAP Forum] Problem with ComplementClasses

[Kasper Andersen]

Hi!

As a test for a more serious application I want to use GAP to find the 
conjugacy classes of complements of the normal subgroup A_4/V_4 in 
S_4/V_4. The following piece of code sets up the quotient S_4/V_4 and 
the normal subgroup A_4/V_4:

S4:=SymmetricGroup(4);
A4:=DerivedSubgroup(S4);
V4:=DerivedSubgroup(A4);
pi:=NaturalHomomorphismByNormalSubgroup(S4,V4);
S4modV4:=Image(pi,S4);
A4modV4:=Image(pi,A4);

After this the result should be obtainable by

ComplementClasses(S4modV4,A4modV4)

but this gives the error

Error, no method found! For debugging hints type ?Recovery from 
NoMethodFound
Error, no 1st choice method found for `PcpsOfEfaSeries' on 1 arguments 
called \
from
PcpsOfEfaSeries( N ) called from
<function>( <arguments> ) called from read-eval-loop
Entering break read-eval-print loop ...
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue

on my system. Why does this happen? Is there an easy way to solve it?

thanks in advance,

Kasper Andersen