proposition: Lemma entourage_split (z x y : M) A : entourage A -> split_ent A (x,z) -> split_ent A (z,y) -> A (x,y).
proof: Proof. by move=> /subset_split_ent sA ??; apply: sA; exists z. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed