Singular

LIB "ncpreim.lib";
ring r = 0,(e,f,h),dp;
matrix d[3][3];
d[1,2] = -h; d[1,3] = 2*e; d[2,3] = -2*f;
def A = nc_algebra(1,d);
setring A; A; // A is U(sl_2)
==> //   characteristic : 0
==> //   number of vars : 3
==> //        block   1 : ordering dp
==> //                  : names    e f h
==> //        block   2 : ordering C
==> //   noncommutative relations:
==> //    fe=ef-h
==> //    he=eh+2e
==> //    hf=fh-2f
// the subalgebra generated by e,f is not admissible since [e,f]=h
admissibleSub(1..2);
==> 0
// but the subalgebra generated by f,h is admissible since [f,h]=2f
admissibleSub(2..3);
==> 1