proposition: Lemma closedI (D E : set T) : closed D -> closed E -> closed (D `&` E).
proof: Proof. by move=> Dcl Ecl p clDEp; split; [apply: Dcl|apply: Ecl]; move=> A /clDEp [q [[]]]; exists q. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed