proposition: Fact mull_fun_is_semi_additive : semi_additive (a \*o f).
proof: Proof. by split=> [|x y]; rewrite /= ?raddf0 ?mulr0// raddfD mulrDr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)