proposition: Lemma cmE_neq0 m i : (m i != 0%N) = (i \in finsupp m).
proof: Proof. by rewrite cmE_eq0 negbK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap