proposition: Lemma mulIr : {in @unit R, left_injective *%R}.
proof: Proof. by move=> x Ux; apply: can_inj (mulrK Ux). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)