Library Float.Digit
Require Export ZArithRing.
Require Export Omega.
Require Export Faux.
Section Pdigit.
Variable n : Z.
Hypothesis nMoreThan1 : (1 < n)%Z.
Let nMoreThanOne := Zlt_1_O _ (Zlt_le_weak _ _ nMoreThan1).
Hint Resolve nMoreThanOne: zarith.
Theorem Zpower_nat_less : ∀ q : nat, (0 < Zpower_nat n q)%Z.
intros q; elim q; simpl in |- *;
auto with zarith.
Qed.
Hint Resolve Zpower_nat_less: zarith.
Theorem Zpower_nat_monotone_S :
∀ p : nat, (Zpower_nat n p < Zpower_nat n (S p))%Z.
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 Zlt_gt; auto with zarith.
Qed.
Theorem Zpower_nat_monotone_lt :
∀ p q : nat, p < q → (Zpower_nat n p < Zpower_nat n q)%Z.
intros p q H'; elim H'; simpl in |- *; auto.
apply Zpower_nat_monotone_S.
intros m H H0; apply Zlt_trans with (1 := H0).
apply Zpower_nat_monotone_S.
Qed.
Hint Resolve Zpower_nat_monotone_lt: zarith.
Theorem Zpower_nat_anti_monotone_lt :
∀ p q : nat, (Zpower_nat n p < Zpower_nat n q)%Z → p < q.
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 :
∀ p q : nat, p ≤ q → (Zpower_nat n p ≤ Zpower_nat n q)%Z.
intros p q H'; case (le_lt_or_eq _ _ H'); auto with zarith.
intros H1; rewrite H1; auto with zarith.
Qed.
Theorem Zpower_nat_anti_monotone_le :
∀ p q : nat, (Zpower_nat n p ≤ Zpower_nat n q)%Z → p ≤ q.
intros p q H'; case (le_or_lt p q); intros H'0; auto with arith.
Contradict H'; auto with zarith.
Qed.
Theorem Zpower_nat_anti_eq :
∀ p q : nat, Zpower_nat n p = Zpower_nat n q → p = q.
intros p q H'; apply le_antisym; apply Zpower_nat_anti_monotone_le;
rewrite H'; auto with zarith.
Qed.
Fixpoint digitAux (v r : Z) (q : positive) {struct q} : nat :=
match q with
| xH ⇒ 0
| xI q' ⇒
match (n × r)%Z with
| r' ⇒
match (r ?= v)%Z with
| Datatypes.Gt ⇒ 0
| _ ⇒ S (digitAux v r' q')
end
end
| xO q' ⇒
match (n × r)%Z with
| r' ⇒
match (r ?= v)%Z with
| Datatypes.Gt ⇒ 0
| _ ⇒ S (digitAux v r' q')
end
end
end.
Definition digit (q : Z) :=
match q with
| Z0 ⇒ 0
| Zpos q' ⇒ digitAux (Zabs q) 1 (xO q')
| Zneg q' ⇒ digitAux (Zabs q) 1 (xO q')
end.
Hint Unfold digit.
Theorem digitAux1 :
∀ p r, (Zpower_nat n (S p) × r)%Z = (Zpower_nat n p × (n × r))%Z.
intros p r; replace (S p) with (1 + p);
[ rewrite Zpower_nat_is_exp | auto with arith ].
rewrite Zpower_nat_1; ring.
Qed.
Theorem Zcompare_correct :
∀ p q : Z,
match (p ?= q)%Z with
| Datatypes.Gt ⇒ (q < p)%Z
| Datatypes.Lt ⇒ (p < q)%Z
| Datatypes.Eq ⇒ p = q
end.
intros p q; unfold Zlt in |- *; generalize (Zcompare_EGAL p q);
(CaseEq (p ?= q)%Z; simpl in |- *; auto).
intros H H0; case (Zcompare_Gt_Lt_antisym p q); auto.
Qed.
Theorem digitAuxLess :
∀ (v r : Z) (q : positive),
match digitAux v r q with
| S r' ⇒ (Zpower_nat n r' × r ≤ v)%Z
| O ⇒ True
end.
intros v r q; generalize r; elim q; clear r q; simpl in |- *; auto.
intros q' Rec r; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite H1; rewrite Zpower_nat_O; auto with zarith.
intros r'; rewrite digitAux1; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite Zpower_nat_O; auto with zarith.
apply Zle_trans with (m := r); auto with zarith.
intros r'; rewrite digitAux1; auto.
intros q' Rec r; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite H1; rewrite Zpower_nat_O; auto with zarith.
intros r'; rewrite digitAux1; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite Zpower_nat_O; auto with zarith.
apply Zle_trans with (m := r); auto with zarith.
intros r'; rewrite digitAux1; auto.
Qed.
Theorem digitLess :
∀ q : Z, q ≠ 0%Z → (Zpower_nat n (pred (digit q)) ≤ Zabs q)%Z.
intros q; case q.
intros H; Contradict H; auto with zarith.
intros p H; unfold digit in |- *;
generalize (digitAuxLess (Zabs (Zpos p)) 1 (xO p));
case (digitAux (Zabs (Zpos p)) 1 (xO p)); simpl in |- *;
auto with zarith.
intros p H; unfold digit in |- *;
generalize (digitAuxLess (Zabs (Zneg p)) 1 (xO p));
case (digitAux (Zabs (Zneg p)) 1 (xO p)); simpl in |- *;
auto with zarith.
Qed.
Hint Resolve digitLess: zarith.
Hint Resolve Zmult_gt_0_lt_compat_r Zmult_gt_0_lt_compat_l: zarith.
Fixpoint pos_length (p : positive) : nat :=
match p with
| xH ⇒ 0
| xO p' ⇒ S (pos_length p')
| xI p' ⇒ S (pos_length p')
end.
Theorem digitAuxMore :
∀ (v r : Z) (q : positive),
(0 < r)%Z →
(v < Zpower_nat n (pos_length q) × r)%Z →
(v < Zpower_nat n (digitAux v r q) × r)%Z.
intros v r q; generalize r; elim q; clear r q; simpl in |- ×.
intros p Rec r Hr; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1 H2; rewrite <- H1.
apply Zle_lt_trans with (Zpower_nat n 0 × r)%Z; auto with zarith arith.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros H1 H2; rewrite digitAux1.
apply Rec.
apply Zlt_mult_ZERO; auto with zarith.
rewrite <- digitAux1; auto.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros p Rec r Hr; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1 H2; rewrite <- H1.
apply Zle_lt_trans with (Zpower_nat n 0 × r)%Z; auto with zarith arith.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros H1 H2; rewrite digitAux1.
apply Rec.
apply Zlt_mult_ZERO; auto with zarith.
rewrite <- digitAux1; auto.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
auto.
Qed.
Theorem pos_length_pow :
∀ p : positive, (Zpos p < Zpower_nat n (S (pos_length p)))%Z.
intros p; elim p; simpl in |- *; auto.
intros p0 H; rewrite Zpos_xI.
apply Zlt_le_trans with (2 × (n × Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
intros p0 H; rewrite Zpos_xO.
apply Zlt_le_trans with (2 × (n × Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
auto with zarith.
Qed.
Theorem digitMore : ∀ q : Z, (Zabs q < Zpower_nat n (digit q))%Z.
intros q; case q.
easy.
intros q'; rewrite <- (Zmult_1_r (Zpower_nat n (digit (Zpos q')))).
unfold digit in |- *; apply digitAuxMore; auto with zarith.
rewrite Zmult_1_r.
simpl in |- *; apply pos_length_pow.
intros q'; rewrite <- (Zmult_1_r (Zpower_nat n (digit (Zneg q')))).
unfold digit in |- *; apply digitAuxMore; auto with zarith.
rewrite Zmult_1_r.
simpl in |- *; apply pos_length_pow.
Qed.
Hint Resolve digitMore: zarith.
Theorem digitInv :
∀ (q : Z) (r : nat),
(Zpower_nat n (pred r) ≤ Zabs q)%Z →
(Zabs q < Zpower_nat n r)%Z → digit q = r.
intros q r H' H'0; case (le_or_lt (digit q) r).
intros H'1; case (le_lt_or_eq _ _ H'1); auto; intros H'2.
absurd (Zabs q < Zpower_nat n (digit q))%Z; auto with zarith.
apply Zle_not_lt; auto with zarith.
apply Zle_trans with (m := Zpower_nat n (pred r)); auto with zarith.
apply Zpower_nat_monotone_le.
generalize H'2; case r; auto with arith.
intros H'1.
absurd (Zpower_nat n (pred (digit q)) ≤ Zabs q)%Z; auto with zarith.
apply Zlt_not_le; auto with zarith.
apply Zlt_le_trans with (m := Zpower_nat n r); auto.
apply Zpower_nat_monotone_le.
generalize H'1; case (digit q); auto with arith.
apply digitLess; auto with zarith.
generalize H'1; case q; unfold digit in |- *; intros tmp; intros; red in |- *;
intros; try discriminate; Contradict tmp; auto with arith.
Qed.
Theorem digitO : digit 0 = 0.
unfold digit in |- *; simpl in |- *; auto with arith.
Qed.
Theorem digit1 : digit 1 = 1.
unfold digit in |- *; simpl in |- *; auto.
Qed.
Theorem digit_monotone :
∀ p q : Z, (Zabs p ≤ Zabs q)%Z → digit p ≤ digit q.
intros p q H; case (le_or_lt (digit p) (digit q)); auto; intros H1;
Contradict H.
apply Zlt_not_le.
cut (p ≠ 0%Z); [ intros H2 | idtac ].
apply Zlt_le_trans with (2 := digitLess p H2).
cut (digit q ≤ pred (digit p)); [ intros H3 | idtac ].
apply Zlt_le_trans with (2 := Zpower_nat_monotone_le _ _ H3);
auto with zarith.
generalize H1; case (digit p); simpl in |- *; auto with arith.
generalize H1; case p; simpl in |- *; intros tmp; intros; red in |- *; intros;
try discriminate; Contradict tmp; auto with arith.
Qed.
Hint Resolve digit_monotone: arith.
Theorem digitNotZero : ∀ q : Z, q ≠ 0%Z → 0 < digit q.
intros q H'.
apply lt_le_trans with (m := digit 1); auto with zarith.
apply digit_monotone.
generalize H'; case q; simpl in |- *; auto with zarith; intros q'; case q';
simpl in |- *; auto with zarith arith; intros; red in |- *;
simpl in |- *; red in |- *; intros; discriminate.
Qed.
Hint Resolve Zlt_gt: zarith.
Theorem digitAdd :
∀ (q : Z) (r : nat),
q ≠ 0%Z → digit (q × Zpower_nat n r) = digit q + r.
intros q r H0.
apply digitInv.
replace (pred (digit q + r)) with (pred (digit q) + r).
rewrite Zpower_nat_is_exp; rewrite Zabs_Zmult;
rewrite (fun x ⇒ Zabs_eq (Zpower_nat n x)); auto with zarith arith.
generalize (digitNotZero _ H0); case (digit q); auto with arith.
intros H'; Contradict H'; auto with arith.
rewrite Zpower_nat_is_exp; rewrite Zabs_Zmult;
rewrite (fun x ⇒ Zabs_eq (Zpower_nat n x)); auto with zarith arith.
Qed.
Theorem digit_minus1 : ∀ p : nat, digit (Zpower_nat n p - 1) = p.
intros p; case p; auto.
intros n0; apply digitInv; auto.
rewrite Zabs_eq.
cut (Zpower_nat n (pred (S n0)) < Zpower_nat n (S n0))%Z; auto with zarith.
cut (0 < Zpower_nat n (S n0))%Z; auto with zarith.
rewrite Zabs_eq; auto with zarith.
Qed.
Theorem digit_bound :
∀ (x y z : Z) (n : nat),
(Zabs x ≤ Zabs y)%Z →
(Zabs y ≤ Zabs z)%Z → digit x = n → digit z = n → digit y = n.
intros x y z n0 H' H'0 H'1 H'2; apply le_antisym.
rewrite <- H'2; auto with arith.
rewrite <- H'1; auto with arith.
Qed.
Theorem digit_abs : ∀ p : Z, digit (Zabs p) = digit p.
intros p; case p; simpl in |- *; auto.
Qed.
Theorem digit_anti_monotone_lt :
(1 < n)%Z → ∀ p q : Z, digit p < digit q → (Zabs p < Zabs q)%Z.
intros H' p q H'0.
case (Zle_or_lt (Zabs q) (Zabs p)); auto; intros H'1.
Contradict H'0.
case (Zle_lt_or_eq _ _ H'1); intros H'2.
apply le_not_lt; auto with arith.
rewrite <- (digit_abs p); rewrite <- (digit_abs q); rewrite H'2;
auto with arith.
Qed.
End Pdigit.
Hint Resolve Zpower_nat_less: zarith.
Hint Resolve Zpower_nat_monotone_lt: zarith.
Hint Resolve Zpower_nat_monotone_le: zarith.
Hint Unfold digit.
Hint Resolve digitLess: zarith.
Hint Resolve digitMore: zarith.
Hint Resolve digit_monotone: arith.
Require Export Omega.
Require Export Faux.
Section Pdigit.
Variable n : Z.
Hypothesis nMoreThan1 : (1 < n)%Z.
Let nMoreThanOne := Zlt_1_O _ (Zlt_le_weak _ _ nMoreThan1).
Hint Resolve nMoreThanOne: zarith.
Theorem Zpower_nat_less : ∀ q : nat, (0 < Zpower_nat n q)%Z.
intros q; elim q; simpl in |- *;
auto with zarith.
Qed.
Hint Resolve Zpower_nat_less: zarith.
Theorem Zpower_nat_monotone_S :
∀ p : nat, (Zpower_nat n p < Zpower_nat n (S p))%Z.
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 Zlt_gt; auto with zarith.
Qed.
Theorem Zpower_nat_monotone_lt :
∀ p q : nat, p < q → (Zpower_nat n p < Zpower_nat n q)%Z.
intros p q H'; elim H'; simpl in |- *; auto.
apply Zpower_nat_monotone_S.
intros m H H0; apply Zlt_trans with (1 := H0).
apply Zpower_nat_monotone_S.
Qed.
Hint Resolve Zpower_nat_monotone_lt: zarith.
Theorem Zpower_nat_anti_monotone_lt :
∀ p q : nat, (Zpower_nat n p < Zpower_nat n q)%Z → p < q.
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 :
∀ p q : nat, p ≤ q → (Zpower_nat n p ≤ Zpower_nat n q)%Z.
intros p q H'; case (le_lt_or_eq _ _ H'); auto with zarith.
intros H1; rewrite H1; auto with zarith.
Qed.
Theorem Zpower_nat_anti_monotone_le :
∀ p q : nat, (Zpower_nat n p ≤ Zpower_nat n q)%Z → p ≤ q.
intros p q H'; case (le_or_lt p q); intros H'0; auto with arith.
Contradict H'; auto with zarith.
Qed.
Theorem Zpower_nat_anti_eq :
∀ p q : nat, Zpower_nat n p = Zpower_nat n q → p = q.
intros p q H'; apply le_antisym; apply Zpower_nat_anti_monotone_le;
rewrite H'; auto with zarith.
Qed.
Fixpoint digitAux (v r : Z) (q : positive) {struct q} : nat :=
match q with
| xH ⇒ 0
| xI q' ⇒
match (n × r)%Z with
| r' ⇒
match (r ?= v)%Z with
| Datatypes.Gt ⇒ 0
| _ ⇒ S (digitAux v r' q')
end
end
| xO q' ⇒
match (n × r)%Z with
| r' ⇒
match (r ?= v)%Z with
| Datatypes.Gt ⇒ 0
| _ ⇒ S (digitAux v r' q')
end
end
end.
Definition digit (q : Z) :=
match q with
| Z0 ⇒ 0
| Zpos q' ⇒ digitAux (Zabs q) 1 (xO q')
| Zneg q' ⇒ digitAux (Zabs q) 1 (xO q')
end.
Hint Unfold digit.
Theorem digitAux1 :
∀ p r, (Zpower_nat n (S p) × r)%Z = (Zpower_nat n p × (n × r))%Z.
intros p r; replace (S p) with (1 + p);
[ rewrite Zpower_nat_is_exp | auto with arith ].
rewrite Zpower_nat_1; ring.
Qed.
Theorem Zcompare_correct :
∀ p q : Z,
match (p ?= q)%Z with
| Datatypes.Gt ⇒ (q < p)%Z
| Datatypes.Lt ⇒ (p < q)%Z
| Datatypes.Eq ⇒ p = q
end.
intros p q; unfold Zlt in |- *; generalize (Zcompare_EGAL p q);
(CaseEq (p ?= q)%Z; simpl in |- *; auto).
intros H H0; case (Zcompare_Gt_Lt_antisym p q); auto.
Qed.
Theorem digitAuxLess :
∀ (v r : Z) (q : positive),
match digitAux v r q with
| S r' ⇒ (Zpower_nat n r' × r ≤ v)%Z
| O ⇒ True
end.
intros v r q; generalize r; elim q; clear r q; simpl in |- *; auto.
intros q' Rec r; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite H1; rewrite Zpower_nat_O; auto with zarith.
intros r'; rewrite digitAux1; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite Zpower_nat_O; auto with zarith.
apply Zle_trans with (m := r); auto with zarith.
intros r'; rewrite digitAux1; auto.
intros q' Rec r; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite H1; rewrite Zpower_nat_O; auto with zarith.
intros r'; rewrite digitAux1; auto.
intros H1; generalize (Rec (n × r)%Z); case (digitAux v (n × r) q').
intros; rewrite Zpower_nat_O; auto with zarith.
apply Zle_trans with (m := r); auto with zarith.
intros r'; rewrite digitAux1; auto.
Qed.
Theorem digitLess :
∀ q : Z, q ≠ 0%Z → (Zpower_nat n (pred (digit q)) ≤ Zabs q)%Z.
intros q; case q.
intros H; Contradict H; auto with zarith.
intros p H; unfold digit in |- *;
generalize (digitAuxLess (Zabs (Zpos p)) 1 (xO p));
case (digitAux (Zabs (Zpos p)) 1 (xO p)); simpl in |- *;
auto with zarith.
intros p H; unfold digit in |- *;
generalize (digitAuxLess (Zabs (Zneg p)) 1 (xO p));
case (digitAux (Zabs (Zneg p)) 1 (xO p)); simpl in |- *;
auto with zarith.
Qed.
Hint Resolve digitLess: zarith.
Hint Resolve Zmult_gt_0_lt_compat_r Zmult_gt_0_lt_compat_l: zarith.
Fixpoint pos_length (p : positive) : nat :=
match p with
| xH ⇒ 0
| xO p' ⇒ S (pos_length p')
| xI p' ⇒ S (pos_length p')
end.
Theorem digitAuxMore :
∀ (v r : Z) (q : positive),
(0 < r)%Z →
(v < Zpower_nat n (pos_length q) × r)%Z →
(v < Zpower_nat n (digitAux v r q) × r)%Z.
intros v r q; generalize r; elim q; clear r q; simpl in |- ×.
intros p Rec r Hr; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1 H2; rewrite <- H1.
apply Zle_lt_trans with (Zpower_nat n 0 × r)%Z; auto with zarith arith.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros H1 H2; rewrite digitAux1.
apply Rec.
apply Zlt_mult_ZERO; auto with zarith.
rewrite <- digitAux1; auto.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros p Rec r Hr; generalize (Zcompare_correct r v); case (r ?= v)%Z; auto.
intros H1 H2; rewrite <- H1.
apply Zle_lt_trans with (Zpower_nat n 0 × r)%Z; auto with zarith arith.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
intros H1 H2; rewrite digitAux1.
apply Rec.
apply Zlt_mult_ZERO; auto with zarith.
rewrite <- digitAux1; auto.
rewrite Zpower_nat_O; rewrite Zmult_1_l; auto with zarith.
auto.
Qed.
Theorem pos_length_pow :
∀ p : positive, (Zpos p < Zpower_nat n (S (pos_length p)))%Z.
intros p; elim p; simpl in |- *; auto.
intros p0 H; rewrite Zpos_xI.
apply Zlt_le_trans with (2 × (n × Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
intros p0 H; rewrite Zpos_xO.
apply Zlt_le_trans with (2 × (n × Zpower_nat n (pos_length p0)))%Z;
auto with zarith.
auto with zarith.
Qed.
Theorem digitMore : ∀ q : Z, (Zabs q < Zpower_nat n (digit q))%Z.
intros q; case q.
easy.
intros q'; rewrite <- (Zmult_1_r (Zpower_nat n (digit (Zpos q')))).
unfold digit in |- *; apply digitAuxMore; auto with zarith.
rewrite Zmult_1_r.
simpl in |- *; apply pos_length_pow.
intros q'; rewrite <- (Zmult_1_r (Zpower_nat n (digit (Zneg q')))).
unfold digit in |- *; apply digitAuxMore; auto with zarith.
rewrite Zmult_1_r.
simpl in |- *; apply pos_length_pow.
Qed.
Hint Resolve digitMore: zarith.
Theorem digitInv :
∀ (q : Z) (r : nat),
(Zpower_nat n (pred r) ≤ Zabs q)%Z →
(Zabs q < Zpower_nat n r)%Z → digit q = r.
intros q r H' H'0; case (le_or_lt (digit q) r).
intros H'1; case (le_lt_or_eq _ _ H'1); auto; intros H'2.
absurd (Zabs q < Zpower_nat n (digit q))%Z; auto with zarith.
apply Zle_not_lt; auto with zarith.
apply Zle_trans with (m := Zpower_nat n (pred r)); auto with zarith.
apply Zpower_nat_monotone_le.
generalize H'2; case r; auto with arith.
intros H'1.
absurd (Zpower_nat n (pred (digit q)) ≤ Zabs q)%Z; auto with zarith.
apply Zlt_not_le; auto with zarith.
apply Zlt_le_trans with (m := Zpower_nat n r); auto.
apply Zpower_nat_monotone_le.
generalize H'1; case (digit q); auto with arith.
apply digitLess; auto with zarith.
generalize H'1; case q; unfold digit in |- *; intros tmp; intros; red in |- *;
intros; try discriminate; Contradict tmp; auto with arith.
Qed.
Theorem digitO : digit 0 = 0.
unfold digit in |- *; simpl in |- *; auto with arith.
Qed.
Theorem digit1 : digit 1 = 1.
unfold digit in |- *; simpl in |- *; auto.
Qed.
Theorem digit_monotone :
∀ p q : Z, (Zabs p ≤ Zabs q)%Z → digit p ≤ digit q.
intros p q H; case (le_or_lt (digit p) (digit q)); auto; intros H1;
Contradict H.
apply Zlt_not_le.
cut (p ≠ 0%Z); [ intros H2 | idtac ].
apply Zlt_le_trans with (2 := digitLess p H2).
cut (digit q ≤ pred (digit p)); [ intros H3 | idtac ].
apply Zlt_le_trans with (2 := Zpower_nat_monotone_le _ _ H3);
auto with zarith.
generalize H1; case (digit p); simpl in |- *; auto with arith.
generalize H1; case p; simpl in |- *; intros tmp; intros; red in |- *; intros;
try discriminate; Contradict tmp; auto with arith.
Qed.
Hint Resolve digit_monotone: arith.
Theorem digitNotZero : ∀ q : Z, q ≠ 0%Z → 0 < digit q.
intros q H'.
apply lt_le_trans with (m := digit 1); auto with zarith.
apply digit_monotone.
generalize H'; case q; simpl in |- *; auto with zarith; intros q'; case q';
simpl in |- *; auto with zarith arith; intros; red in |- *;
simpl in |- *; red in |- *; intros; discriminate.
Qed.
Hint Resolve Zlt_gt: zarith.
Theorem digitAdd :
∀ (q : Z) (r : nat),
q ≠ 0%Z → digit (q × Zpower_nat n r) = digit q + r.
intros q r H0.
apply digitInv.
replace (pred (digit q + r)) with (pred (digit q) + r).
rewrite Zpower_nat_is_exp; rewrite Zabs_Zmult;
rewrite (fun x ⇒ Zabs_eq (Zpower_nat n x)); auto with zarith arith.
generalize (digitNotZero _ H0); case (digit q); auto with arith.
intros H'; Contradict H'; auto with arith.
rewrite Zpower_nat_is_exp; rewrite Zabs_Zmult;
rewrite (fun x ⇒ Zabs_eq (Zpower_nat n x)); auto with zarith arith.
Qed.
Theorem digit_minus1 : ∀ p : nat, digit (Zpower_nat n p - 1) = p.
intros p; case p; auto.
intros n0; apply digitInv; auto.
rewrite Zabs_eq.
cut (Zpower_nat n (pred (S n0)) < Zpower_nat n (S n0))%Z; auto with zarith.
cut (0 < Zpower_nat n (S n0))%Z; auto with zarith.
rewrite Zabs_eq; auto with zarith.
Qed.
Theorem digit_bound :
∀ (x y z : Z) (n : nat),
(Zabs x ≤ Zabs y)%Z →
(Zabs y ≤ Zabs z)%Z → digit x = n → digit z = n → digit y = n.
intros x y z n0 H' H'0 H'1 H'2; apply le_antisym.
rewrite <- H'2; auto with arith.
rewrite <- H'1; auto with arith.
Qed.
Theorem digit_abs : ∀ p : Z, digit (Zabs p) = digit p.
intros p; case p; simpl in |- *; auto.
Qed.
Theorem digit_anti_monotone_lt :
(1 < n)%Z → ∀ p q : Z, digit p < digit q → (Zabs p < Zabs q)%Z.
intros H' p q H'0.
case (Zle_or_lt (Zabs q) (Zabs p)); auto; intros H'1.
Contradict H'0.
case (Zle_lt_or_eq _ _ H'1); intros H'2.
apply le_not_lt; auto with arith.
rewrite <- (digit_abs p); rewrite <- (digit_abs q); rewrite H'2;
auto with arith.
Qed.
End Pdigit.
Hint Resolve Zpower_nat_less: zarith.
Hint Resolve Zpower_nat_monotone_lt: zarith.
Hint Resolve Zpower_nat_monotone_le: zarith.
Hint Unfold digit.
Hint Resolve digitLess: zarith.
Hint Resolve digitMore: zarith.
Hint Resolve digit_monotone: arith.