proposition: Fact ffun_addN : left_inverse (@ffun_zero _ _) ffun_opp (@ffun_add _ _).
proof: Proof. by move=> f; apply/ffunP=> a; rewrite !ffunE addNr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)