[GAP Forum] RootSystem returning fail?

[Dmitrii Pasechnik]

Dear all,
is the following a bug, or a feature?
gap> aa;
[ [ [ 1, 0, 0, 0 ], [ 0, 1, 0, 0 ], [ 0, 0, 1, 0 ], [ 0, 0, 0, 1 ] ],
  [ [ 0, 2, 0, 0 ], [ 1, 1, 0, 0 ], [ 0, 0, 0, 2 ], [ 0, 0, 1, 1 ] ],
  [ [ -2, 0, -4, -4 ], [ 0, 0, 0, 4 ], [ 1, 1, 0, 2 ], [ 0, -1, 0, -2 ] ],
  [ [ 0, 0, 0, 8 ], [ -2, 0, -4, 0 ], [ 0, -2, 0, -4 ], [ 1, 0, 0, 0 ] ] ]
gap> ll:=LieAlgebra(Rationals,aa);
<Lie algebra over Rationals, with 4 generators>
gap> RootSystem(ll);
fail
gap>

(In fact, I know that this algebra is isomorphic to gl(2,C), and I would like
to find its representation in M_2(C))

Thanks,
Dmitrii


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