proposition: Lemma open_interior (A : set T) : open A^°.
proof: Proof. rewrite openE => p; rewrite /interior nbhsE => - [B [Bop Bp]]. by rewrite open_subsetE //; exists B. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed