proposition: Fact mulr_fun_is_semi_additive : semi_additive (a \o* f).
proof: Proof. by split=> [|x y]; rewrite /= ?raddf0 ?mul0r// raddfD mulrDl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)