Function: galoisisabelian
Section: number_fields
C-Name: galoisisabelian
Prototype: GD0,L,
Help: galoisisabelian(gal,{flag=0}): gal being as output by galoisinit,
return 0 if gal is not abelian, the HNF matrix of gal over gal.gen if
flag=0, 1 if flag is 1, and the SNF of gal is flag=2.
Doc: \var{gal} being as output by \kbd{galoisinit}, return $0$ if
\var{gal} is not an abelian group, and the HNF matrix of \var{gal} over
\kbd{gal.gen} if $fl=0$, $1$ if $fl=1$.
This command also accepts subgroups returned by \kbd{galoissubgroups}.