proposition: Lemma bin_nonneg_int (a b : int) : 0 <= b -> b <= a -> exists e : int, binomialz a b = e /\ e > 0.
proof: Proof. case: a b => [] a [] b //= _ leba. by exists (Posz 'C(a, b)); rewrite binz_nat_nat [_ < _]bin_gt0. Qed.
imports: mathcomp(all_ssreflect all_algebra) tactics