proposition: Fact ffun1_nonzero : ffun_one != 0.
proof: Proof. by apply/eqP => /ffunP/(_ a)/eqP; rewrite !ffunE oner_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)