proposition: Lemma mclosure_invo s : mclosure (mclosure s) = mclosure s.
proof: Proof. apply/eqP; rewrite eqEsubset mclosure_sub andbT. apply/subsetP=> x; rewrite !inE mclosure_mrank => /eqP rkxsE. rewrite eqn_leq -[X in (_ <= X) && _]rkxsE !mrank_subset //; first by apply: subsetUr. by apply/setUS/mclosure_sub. Qed.
imports: mathcomp(all_ssreflect)