proposition: Lemma mf_eq0 m : (mf m == 0%N) = (m == 1%M).
proof: Proof. by apply/eqP/eqP=> [|->]; rewrite ?mf0 // => /mf_eq0I. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap