proposition: Lemma mulr0 : @right_zero R R 0 mul.
proof: Proof. by move=> x; apply: (addIr (x * 1)); rewrite -mulrDr !add0r mulr1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)