proposition: Lemma mul0cm : left_id onecm mulcm.
proof: Proof. by move=> m; apply/eqP/cmP=> i; rewrite mulcmE onecmE add0n. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap