Function: qforbits
Section: linear_algebra
C-Name: qforbits
Prototype: GG
Help: qforbits(G,V): return the orbits of V under the action of the group
 of linear transformation generated by the set G, which must stabilize V.
Doc: return the orbits of $V$ under the action of the group
 of linear transformation generated by the set $G$.
 It is assumed that $G$ contains minus identity, and only one vector
 in $\{v, -v\}$ should be given.
 If $G$ does not stabilize $V$, the function return $0$.

 In the example below, we compute representatives and lengths of the orbits of
 the vectors of norm $\leq 3$ under the automorphisms of the lattice $\Z^{6}$.
 \bprog
 ?  Q=matid(6); G=qfauto(Q); V=qfminim(Q,3);
 ?  apply(x->[x[1],#x],qforbits(G,V))
 %2 = [[[0,0,0,0,0,1]~,6],[[0,0,0,0,1,-1]~,30],[[0,0,0,1,-1,-1]~,80]]
 @eprog
