proposition: Lemma mul0r : @left_zero R R 0 mul.
proof: Proof. by move=> x; apply: (addIr (1 * x)); rewrite -mulrDl !add0r mul1r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)