Hi Linden, This works for me in 9.1. So this was either fixed in a later version or possibly wasn't considered supported in version 8.9 (although probably the former). So I would recommend upgrading to the latest version of Sage.
Side note: if you would like to contribute to Sage, the (semi)simple Lie algebras should probably just return themselves as the derived subalgebra. Best, Travis On Tuesday, September 22, 2020 at 7:36:58 AM UTC+10, Linden Disney wrote: > > On the doc page for Lie subalgebras ( > https://doc.sagemath.org/html/en/reference/algebras/sage/algebras/lie_algebras/subalgebra.html) > > there is an example getting a subalgebra of sl3: > > sl3 = LieAlgebra(QQ, cartan_type=['A',2]) > D = sl3.derived_subalgebra() > > This throws the error > > TypeError: unsupported operand parent(s) for <: 'Coroot lattice of the > Root system of type ['A', 2]' and 'Root lattice of the Root system of type > ['A', 2]' > > The error persists when calculating general subalgebras (e.g. trying > sl3.subalgebra(list(sl3.e())) ) and seems to be related to the classical > Lie algebra, as I can get subalgebras working fine with, for example, the > Heisenberg algebra (see first example on the doc page). > > I am running SageMath version 8.9, Release Date: 2019-09-29 with system > details: > > Operating System: Ubuntu 18.04.4 LTS > Kernel: Linux 5.4.0-42-generic > Architecture: x86-64 > > -- You received this message because you are subscribed to the Google Groups "sage-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/sage-devel/bafad702-64c1-4cab-a0f9-33bb8cc99350o%40googlegroups.com.
