proposition: Lemma mmorphM : {morph f : x y / (x * y)%M >-> (x * y)%R}.
proof: Proof. exact: mmorphism_subproof.1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap