proposition: Lemma minmaxset P A : minset P A = maxset [pred B | P (~: B)] (~: A).
proof: Proof. by rewrite /maxset unlock setCK; apply: minset_eq => B /=; rewrite setCK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop)