proposition: Lemma fdegM : {morph fdeg: m1 m2 / (m1 * m2)%M >-> (m1 + m2)%N }.
proof: Proof. by move=> m1 m2; rewrite !fdegE fmM size_cat. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap