proposition: Lemma fmmul_eq1 m1 m2 : fmmul m1 m2 = fmone -> m1 = fmone /\ m2 = fmone.
proof: Proof. by case: m1 m2 => [[|? ?]] [[|? ?]]; rewrite !fmE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap