proposition: Lemma mx_ent_inv A : mx_ent A -> mx_ent (A^-1)%classic.
proof: Proof. move=> [B entB sBA]; exists (fun i j => ((B i j)^-1)%classic). by move=> i j; apply: entourage_inv. by move=> MN BMN; apply: sBA. Qed.
imports: HB(structures) mathcomp(all_ssreflect all_algebra finmap generic_quotient) mathcomp(boolp classical_sets functions) mathcomp(cardinality mathcomp_extra fsbigop) reals signed