proposition: Lemma closed_subspaceW (U : set T) : closed (U : set T) -> closed (U : set (subspace A)).
proof: Proof. by move=> /closed_openC/open_subspaceW/open_closedC; rewrite setCK. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed