Section Pdigit.
(* n is the base *)
Variable n : Z.
(* and it is greater or equal to 2 *)
Hypothesis nMoreThan1 : (1 < n)%Z.
Let nMoreThanOne := Zlt_1_O _ (Zlt_le_weak _ _ nMoreThan1).
Hint Resolve nMoreThanOne: zarith.
intros q; elim q; simpl in |- *;
auto with zarith.
Qed.
Hint Resolve Zpower_nat_less: zarith.
intros p; rewrite <- (Zmult_1_l (Zpower_nat n p)); replace (S p) with (1 + p);
[ rewrite Zpower_nat_is_exp | auto with zarith ].
rewrite Zpower_nat_1; auto with zarith.
apply Zmult_gt_0_lt_compat_r; auto with zarith.
apply Z.lt_gt; auto with zarith.
Qed.
intros p q H'; elim H'; simpl in |- *; auto.
apply Zpower_nat_monotone_S.
intros m H H0; apply Z.lt_trans with (1 := H0).
apply Zpower_nat_monotone_S.
Qed.
Hint Resolve Zpower_nat_monotone_lt: zarith.
intros p q H'.
case (le_or_lt q p); auto; (intros H'1; generalize H'; case H'1).
intros H'0; Contradict H'0; auto with zarith.
intros m H'0 H'2; Contradict H'2; auto with zarith.
Qed.

Theorem Zpower_nat_monotone_le :
forall p q : nat, p <= q -> (Zpower_nat n p <= Zpower_nat n q)%Z.