proposition: Fact ffun_mulC : commutative (@ffun_mul aT R).
proof: Proof. by move=> f1 f2; apply/ffunP=> i; rewrite !ffunE mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)