proposition: Lemma cvg_close {F} {FF : ProperFilter F} x y : F --> x -> F --> y -> close x y.
proof: Proof. by move=> /sub_meets sx /sx; rewrite closeEnbhs; apply; apply/proper_meetsxx. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed