proposition: Fact ffun_mul_1r : right_id ffun_one ffun_mul.
proof: Proof. by move=> f; apply/ffunP=> i; rewrite !ffunE mulr1. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)