proposition: Lemma comRingMixin (R : comRingType) (T : ringType) (f : T -> R) : phant T -> injective f -> {morph f : x y / x * y} -> commutative (@mul T).
proof: Proof. by move=> _ inj_f fM x y; apply: inj_f; rewrite !fM mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)