# Library Cantor.epsilon0.EPSILON0

Require Import Arith.
Require Import Omega. Require Import Compare_dec.
Require Import Relations.
Require Import Wellfounded.

Require Import Tools.
Require Import More_nat.
Require Import Wf_nat.
Require Import AccP.
Require Import not_decreasing.
Require Import ArithRing.

Require Import term.
Require Import rpo.
Require Import List.

Set Implicit Arguments.

cons a n b represents omega^a *(S n) + b

Inductive T1 : Set :=
zero : T1
| cons : T1 nat T1 T1.

some abreviations
omega^x * (S k)

Definition omega_term (a:T1)(k:nat) :=
cons a k zero.

Definition phi0 a := cons a 0 zero.

Definition finite (n:nat) : T1 :=
match n with 0 ⇒ zero
| S pcons zero p zero
end.

Notation "'F' n" := (finite n)(at level 29) : cantor_scope.

Definition omega := cons (cons zero 0 zero) 0 zero.

Definition log a := match a with
| zerozero
| cons a _ _a
end.

Fixpoint omega_tower (n:nat) : T1 :=
match n with 0 ⇒ finite 1
| S pcons (omega_tower p) 0 zero
end.

Inductive lt : T1 T1 Prop :=
| zero_lt : a n b, lt zero (cons a n b)
a a' n n' b b', lt a a'
lt (cons a n b) (cons a' n' b')
| coeff_lt : a n n' b b', (n < n')%nat
lt (cons a n b) (cons a n' b')
| tail_lt : a n b b', lt b b'
lt (cons a n b) (cons a n b')
where "o < o'" := (lt o o') : cantor_scope.

Hint Resolve zero_lt head_lt coeff_lt tail_lt : T1.

Open Scope cantor_scope.
Delimit Scope cantor_scope with ca.

Definition le (alpha beta :T1) := alpha = beta alpha < beta.
Notation "alpha <= beta" := (le alpha beta) : cantor_scope.

Hint Unfold le : T1.

Inductive ap : T1 Prop:=
ap_intro : a, ap (cons a 0 zero).

Lemma ap_phi0 : a, ap (phi0 a).
Proof.
unfold phi0;constructor.
Qed.

Lemma ap_phi0R : a, ap a {b : T1 | a = phi0 b}.
Proof.
destruct a.
intro; elimtype False.
inversion H.
a1.
inversion H.
unfold phi0;auto.
Qed.

Fixpoint compare (c c':T1){struct c'}:comparison :=
match c,c' with
zero, zeroEq
| zero, cons a' n' b'Lt
| _ , zeroGt
| (cons a n b),(cons a' n' b') ⇒
(match compare a a' with
| LtLt
| GtGt
| Eq ⇒ (match lt_eq_lt_dec n n' with
inleft (left _) ⇒ Lt
| inright _Gt
| _compare b b'
end)
end)
end.

Definition max a b := match compare a b with Ltb | _a end.

Theorem not_lt_zero : a, ¬ a < zero.
Proof.
red; inversion_clear 1.
Qed.

Hint Resolve not_lt_zero : T1.

Theorem lt_inv : a n b a' n' b',
cons a n b < cons a' n' b'
a < a'
a = a' (n < n')%nat
a = a' n = n' b < b'.
Proof.
inversion_clear 1; auto.
Qed.

Theorem lt_irr : a, ¬ a < a.
Proof.
induction a.
red;inversion_clear 1.
intro H; case (lt_inv H); intuition.
Qed.
Hint Resolve lt_irr : T1.

Lemma lt_inv_nb : a n n' b b',
cons a n b < cons a n' b'
(n<n')%nat n=n' b < b'.
Proof.
inversion_clear 1; auto with T1.
elim (lt_irr (a:=a)); auto.
Qed.

Lemma lt_inv_b : a n b b',
cons a n b < cons a n b' b < b'.
Proof.
inversion_clear 1; auto with arith T1.
elim (lt_irr (a:=a));auto.
elim (lt_irrefl n);auto.
Qed.

Theorem lt_trans : a b, a < b
c, b < c a < c.
Proof.
induction 1.
inversion 1; auto with T1.
inversion_clear 1; auto with T1.
inversion_clear 1; eauto with T1 arith.
inversion_clear 1; auto with T1.
Qed.

Theorem lt_not_gt : a b, a < b ¬ b < a.
Proof.
intros o1 o2 H H0.
generalize (lt_trans H H0).
intro H2; case (lt_irr H2).
Qed.

Lemma finite_lt : n p : nat, (n < p)%nat
F n < F p.
Proof.
destruct n;simpl.
destruct p.
inversion 1.
simpl;auto with T1.
destruct p.
inversion 1.
simpl;auto with T1.
intro; assert (n<p)%nat ; auto with arith T1.
Qed.

Lemma finite_ltR : n p : nat,
F n < F p
(n < p)%nat.
Proof.
destruct n;simpl.
destruct p.
inversion 1.
auto with arith.
destruct p.
inversion 1.
simpl.
intro H; case (lt_inv_nb H).
auto with arith.
intros (_,H0); case (lt_irr H0).
Qed.

Inductive nf : T1 Prop :=
| zero_nf : nf zero
| single_nf : a n, nf a nf (cons a n zero)
| cons_nf : a n a' n' b, a' < a
nf a
nf(cons a' n' b)
nf(cons a n (cons a' n' b)).
Hint Resolve zero_nf single_nf cons_nf : T1.

Inductive nf2 : T1 T1 Prop :=
| nf2_z : a, nf2 zero a
| nf2_c : a a' n' b', a' < a
nf2 (cons a' n' b') a.

Hint Resolve nf2_z nf2_c : T1.

Lemma nf_inv1 : a n b, nf (cons a n b) nf a.
Proof.
inversion_clear 1; auto.
Qed.

Lemma nf_inv2 : a n b, nf (cons a n b) nf b.
Proof.
inversion_clear 1; auto with T1.
Qed.

Hint Resolve nf_inv1 nf_inv2 : T1.

Ltac nf_inv := (eapply nf_inv1; progress eauto)||
(eapply nf_inv2; progress eauto).

Lemma nf_tail_lt_nf : b b', b' < b nf b'
a n, nf (cons a n b)
nf (cons a n b').
Proof.
induction 1.
constructor; eauto with T1.
constructor.
apply lt_trans with a'; auto.
inversion H1; eauto with T1.
eauto with T1.
assumption.
constructor.
inversion H1;eauto with T1.
eauto with T1.
assumption.
constructor.
inversion H1;eauto with T1.
eauto with T1.
assumption.
Qed.

Lemma tail_lt_cons : b n a,
nf (cons a n b)
b < cons a n b.
Proof.
induction b.
constructor.
constructor 2.
inversion H;auto.
Qed.

Lemma nf_intro : a n b, nf a
nf b
nf2 b a
nf (cons a n b).
Proof.
destruct 3; constructor; auto.
Qed.

Lemma nf2_intro : a n b, nf (cons a n b)
nf2 b a.
Proof.
inversion 1 ; constructor; auto.
Qed.

Lemma nf2_phi0 : a b, nf2 b a
b < phi0 a.
Proof.
induction 1; compute; auto with T1.
Qed.

Lemma nf2_phi0R : a b, b < phi0 a nf2 b a.
Proof.
induction b.
constructor.
inversion_clear 1.
constructor;auto.
inversion H0.
inversion H0.
Qed.

Lemma nf_coeff_irrelevance : a b n p, nf (cons a n b)
nf (cons a p b).
Proof.
intros; apply nf_intro; try nf_inv.
eapply nf2_intro;eauto.
Qed.

Lemma log_nf : a, nf a nf (log a).
Proof.
destruct a;unfold log;simpl.
constructor; eauto with T1.
eauto with T1.
Qed.

Lemma nf_of_finite : n b, nf (cons zero n b)
b = zero.
Proof.
intros n b H; inversion_clear H.
trivial.
case (not_lt_zero (a:=a'));auto.
Qed.

Lemma ordinal_finite : n, nf (F n).
Proof.
unfold finite; intro n;case n; auto with T1 arith.
Qed.

Lemma nf_omega : nf omega.
Proof.
unfold omega; auto with T1.
Qed.

Theorem nf_phi0 : a, nf a nf (phi0 a).
compute;auto with T1.
Qed.

Lemma nf_tower : n, nf (omega_tower n).
induction n; simpl; auto with T1.
Qed.

Definition nf_rect : P : T1 Type,
P zero
( n: nat, P (cons zero n zero))
( a n b n' b', nf (cons a n b)
P (cons a n b)
nf2 b' (cons a n b)
nf b'
P b'
P (cons (cons a n b) n' b'))
a, nf a P a.
Proof.
intros P H0 Hfinite Hcons.
induction a.
trivial.
generalize IHa1;case a1.
intros IHc0 H.
rewrite (nf_of_finite H).
apply Hfinite.
intros c n0 c0 IHc0 H2; apply Hcons.
eauto with T1.
apply IHc0; eauto with T1.
eapply nf2_intro. eauto.
nf_inv; eauto.
apply IHa2.
nf_inv.
Defined.

Section lt_not_well_founded.

Let f := (fix f (i:nat): T1 :=
match i with 0 ⇒ (phi0 (F 2))
| S icons (F 1) 0 (f i)
end).

Lemma f_not_in_normal_form :
i, ¬ (nf (f (S i))).
Proof.
induction i; red; simpl.
inversion 1.
inversion H3.
inversion H9.
inversion H9.
simpl in IHi.
inversion 1.
case (lt_irr H3).
Qed.

Lemma f_decreases : i, f (S i) < f i.
Proof.
induction i; compute; auto with T1.
Qed.

Theorem lt_not_wf : ¬ (well_founded lt).
Proof.
red; intro wf.
case (not_decreasing _ lt).
auto.

f.
exact f_decreases.
Qed.

End lt_not_well_founded.

Theorem zero_le : a, zero a.
Proof.
unfold le.
destruct a; [left|right];repeat constructor.
Qed.

Theorem le_trans : a b c, a b b c a c.
Proof.
destruct 1.
subst b;auto.
destruct 1.
subst b;right;auto.
right;eapply lt_trans;eauto.
Qed.

Theorem le_lt_trans : a b c, a b b < c a < c.
Proof.
destruct 1.
subst b;auto.
intros;eapply lt_trans;eauto.
Qed.

Theorem lt_le_trans : a b c, a < b b c a < c.
Proof.
destruct 2.
subst b;auto.
eapply lt_trans;eauto.
Qed.

Theorem le_inv : a n b a' n' b',
cons a n b cons a' n' b'
a < a'
a = a' (n < n')%nat
a = a' n = n' b b'.
Proof.
intros a n b a' n' b' H; case H.
injection 1; right.
right; subst a; subst n ; subst b; auto with T1.
intro H0; generalize (lt_inv H0).
intro H1; case H1; auto.
intros [(H2,H3) | (H2,(H3,H4))].
auto.
right;right;auto with T1.
Qed.

Lemma lt_not_le: a b, a < b ¬ b a.
Proof.
red; unfold le.
intros a b H H0; case H0;intro.
subst b; absurd (lt a a);auto with T1.
absurd (lt a a); eauto with T1.
eapply lt_trans;eauto.
Qed.

Lemma lt_inv_le : a n b a' n' b',
cons a n b < cons a' n' b'
a a'.
Proof.
intros a n b a' n' b' H.
case (lt_inv H).
auto with T1.
intros [(e,i)|(e,(e',i))].
subst a; auto with T1.
subst a; auto with T1.
Qed.

Theorem le_zero_inv : a, a zero a = zero.
Proof.
destruct 1.
auto.
absurd (a < zero);auto with T1.
Qed.

Theorem le_tail : a n b b', b b'
cons a n b cons a n b'.
Proof.
destruct 1.
subst b; left; auto.
right; auto with T1.
Qed.

Hint Resolve zero_le le_tail : T1.

Lemma head_lt_cons : a n b, a < cons a n b.
Proof.
induction a.
constructor.
constructor 2; auto.
Qed.

Definition T1_eq_dec : (a b : T1), {a = b}+{a b}.
Proof.
decide equality.
apply eq_nat_dec.
Defined.

Definition trichotomy_inf : a b, {a < b}+{a = b}+{b < a}.
Proof.
induction a; destruct b; auto with T1.
case (IHa1 b1);intros s.
case s;intros.
auto with T1.
subst b1; case (lt_eq_lt_dec n n0).
destruct 1.
auto with T1.
subst n;
case (IHa2 b2); auto with T1.
destruct 1;[idtac| subst b2];auto with T1.
right;auto with T1.
auto with T1.
Defined.

Definition max' a b :=
if trichotomy_inf a b
then b else a.

Goal a b, a < b max' a b = b.
intros a b H; unfold max';
case (trichotomy_inf a b);auto.
intro;case (lt_not_gt H);auto.
Qed.

Definition lt_le_dec : a b, {a < b}+{b a}.
Proof.
intros a b; case (trichotomy_inf a b).
destruct 1.
left;auto.
right;left; auto.
right;right; auto.
Defined.

Module Eps0_sig <: Signature.

Inductive symb0 : Set := nat_0 | nat_S | ord_zero | ord_cons.

Definition symb := symb0.

Lemma eq_symbol_dec : f1 f2 : symb, {f1 = f2} + {f1 f2}.
Proof.
intros; decide equality.
Qed.

The arity of a symbol contains also the information about built-in theories as in CiME
Inductive arity_type : Set :=
| AC : arity_type
| C : arity_type
| Free : nat arity_type.

Definition arity : symb arity_type :=
fun fmatch f with
| nat_0Free 0
| ord_zeroFree 0
| nat_SFree 1
| ord_consFree 3
end.

End Eps0_sig.

# Module Type Variables.

There are almost no assumptions, except a decidable equality.
Module Vars <: Variables.

Inductive empty_set : Set := .
Definition var := empty_set.

Lemma eq_variable_dec : v1 v2 : var, {v1 = v2} + {v1 v2}.
Proof.
intros; decide equality.
Qed.

End Vars.

Module Eps0_prec <: Precedence.

Definition A : Set := Eps0_sig.symb.
Import Eps0_sig.

Definition prec : relation A :=
fun f gmatch f, g with
| nat_0, nat_STrue
| nat_0, ord_zeroTrue
| nat_0, ord_consTrue
| ord_zero, nat_STrue
| ord_zero, ord_consTrue
| nat_S, ord_consTrue
| _, _False
end.

Inductive status_type : Set :=
| Lex : status_type
| Mul : status_type.

Definition status : A status_type := fun fLex.

Lemma prec_dec : a1 a2 : A, {prec a1 a2} + {¬ prec a1 a2}.
Proof.
intros a1 a2; destruct a1; destruct a2;
Qed.

Lemma prec_antisym : s, prec s s False.
Proof.
intros s; destruct s; simpl; trivial.
Qed.

Lemma prec_transitive : transitive A prec.
Proof.
intros s1 s2 s3; destruct s1; destruct s2; destruct s3; simpl; intros; trivial; contradiction.
Qed.

End Eps0_prec.

Module Eps0_alg <: Term := term.Make (Eps0_sig) (Vars).
Module Eps0_rpo <: RPO := rpo.Make (Eps0_alg) (Eps0_prec).

Import Eps0_alg.
Import Eps0_rpo.
Import Eps0_sig.

Fixpoint nat_2_term (n:nat) : term :=
match n with 0 ⇒ (Term nat_0 nil)
| S pTerm nat_S ((nat_2_term p)::nil)
end.

# Every (representation of a) natural number is less than

a non zero ordinal

Lemma nat_lt_cons : (n:nat) a p b , rpo (nat_2_term n)
(Term ord_cons (a::p::b::nil)).
induction n;simpl.
constructor 2.
simpl; trivial.
destruct 1.
constructor 2.
simpl; trivial.
inversion_clear 1.
subst s';apply IHn.
case H0.
Qed.

Theorem rpo_trans : t t1 t2, rpo t t1 rpo t1 t2 rpo t t2.
intros.
case (rpo_closure t2 t1 t);eauto.
Qed.

Fixpoint T1_2_term (a:T1) : term :=
match a with
zeroTerm ord_zero nil
|cons a n bTerm ord_cons (T1_2_term a :: nat_2_term n ::T1_2_term b::nil)
end.

Fixpoint T1_size (o:T1):nat :=
match o with zero ⇒ 0
| cons a n bS (T1_size a + n + T1_size b)%nat
end.

Lemma T1_size1 : a n b, (T1_size zero < T1_size (cons a n b))%nat.
Proof.
simpl.
intros.
auto with arith.
Qed.

Lemma T1_size2 : a n b , (T1_size a < T1_size (cons a n b))%nat.
Proof.
simpl; auto with arith.
Qed.

Lemma T1_size3 : a n b , (T1_size b < T1_size (cons a n b))%nat.
Proof.
simpl; auto with arith.
Qed.

Hint Resolve T1_size2 T1_size3.

let us recall subterm properties on T1
Lemma lt_subterm1 : a a' n' b', a < a'
a < cons a' n' b'.
Proof.
intros.
apply lt_trans with (cons a n' b');auto with T1.
Qed.

Lemma lt_subterm2 : a a' n n' b b', a < a'
nf (cons a n b)
nf (cons a' n' b')
b < cons a' n' b'.
Proof.
intros.
apply le_lt_trans with (cons a n b).
right.
apply tail_lt_cons;auto.
constructor.
auto.
Qed.

Hint Resolve nat_lt_cons.
Hint Resolve lt_subterm2 lt_subterm1.
Hint Resolve T1_size3 T1_size2 T1_size1.

Lemma nat_2_term_mono : n n', (n < n')%nat
rpo (nat_2_term n) (nat_2_term n').
Proof.
induction 1.
simpl.
eapply Subterm.
eleft.
esplit.
constructor.
simpl.
eapply Subterm.
eleft.
esplit.
constructor.
auto.
Qed.

Theorem lt_inc_rpo_0 : n,
o' o, (T1_size o + T1_size o' n)%nat
o < o' nf o nf o'
rpo (T1_2_term o) (T1_2_term o').
Proof.
induction n.
destruct o'.
inversion 2.
destruct o.
simpl.
inversion 1.
simpl;inversion 1.
inversion 2.
simpl.
intros; apply Top_gt.
simpl;trivial.
inversion 1.
simpl; intros; apply Top_eq_lex.
simpl;trivial.
left.
apply IHn.
subst o;subst o'.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a' n' b'))%nat.
simpl;
auto with arith.
omega.
auto.
auto.
nf_inv.
nf_inv.
simpl;auto.
inversion_clear 1.
subst s'.
change (rpo (T1_2_term a) (T1_2_term (cons a' n' b'))).
apply IHn;auto.
subst o;subst o'.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a' n' b'))%nat.
auto with arith.
auto.
nf_inv.
destruct H7 as [|[|H8]].
subst s'.
apply nat_lt_cons.
subst s'.
change (rpo (T1_2_term b) (T1_2_term (cons a' n' b'))).
apply IHn;auto.
subst o;subst o'.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a' n' b'))%nat.
auto with arith.
auto.
eauto.
nf_inv.
case H8.
intros.
simpl;apply Top_eq_lex.
auto.
constructor 2.
constructor 1.
apply nat_2_term_mono.
auto.
auto.
inversion_clear 1.
subst s'.
change (rpo (T1_2_term a) (T1_2_term (cons a n' b'))).
apply IHn;auto.
subst o;subst o'.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a n' b'))%nat.
auto with arith.
auto.
nf_inv.
destruct H7 as [|[|H8]].
subst s'.
apply nat_lt_cons.
subst s'.
change (rpo (T1_2_term b) (T1_2_term (cons a n' b'))).
apply IHn;auto.
subst o;subst o'.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a n' b'))%nat.
auto with arith.
auto.
apply lt_le_trans with (cons a 0 zero).
inversion H4.
auto with T1.
auto with T1.
case n'.
apply le_tail;auto with T1.
auto with T1 arith.
nf_inv.
case H8.
simpl.
intros;apply Top_eq_lex.
auto.
right.
right.
left.
apply IHn.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a n0 b'))%nat.
apply plus_lt_compat.
auto.
auto.
subst o;subst o';auto.
auto.
nf_inv.
nf_inv.
auto.
inversion_clear 1.
subst s'.
eapply Subterm.
2:eleft.
left;auto.
destruct H7 as [|[|H8]].
subst s'.
apply nat_lt_cons.
subst s'.
change (rpo (T1_2_term b) (T1_2_term (cons a n0 b'))).
apply IHn.
apply lt_n_Sm_le .
apply Lt.lt_le_trans with (T1_size (cons a n0 b) + T1_size (cons a n0 b'))%nat.
auto with arith.
subst o;subst o'.
auto.
apply lt_le_trans with (cons a 0 zero).
inversion H4.
auto with T1.
auto with T1.
case n0.
apply le_tail;auto with T1.
auto with T1 arith.
nf_inv.
auto.
case H8.
Qed.

Remark R1 : Acc P.prec nat_0.
split.
Qed.

Hint Resolve R1.

Remark R2 : Acc P.prec ord_zero.
split.
Qed.

Hint Resolve R2.

Remark R3 : Acc P.prec nat_S.
split.
Qed.

Hint Resolve R3.

Remark R4 : Acc P.prec ord_cons.
split.
Qed.

Hint Resolve R4.

Theorem well_founded_rpo : well_founded rpo.
Proof.
apply wf_rpo.
red.
destruct a;auto.
Qed.

Section well_founded.

Let R := restrict T1 nf lt.

Hint Unfold restrict R.

Lemma R_inc_rpo : o o', R o o' rpo (T1_2_term o) (T1_2_term o').
Proof.
intros o o' (H,(H1,H2)).
eapply lt_inc_rpo_0;auto.
Qed.

Lemma nf_Wf : well_founded_P _ nf lt.
Proof.
unfold well_founded_P.
intros.
unfold restrict.
generalize (Acc_inverse_image _ _ rpo T1_2_term a (well_founded_rpo (T1_2_term a))).
intro.
eapply Acc_incl with (fun x y : T1rpo (T1_2_term x) (T1_2_term y)).
red.
apply R_inc_rpo.
auto.
Qed.

End well_founded.

Definition transfinite_induction :
(P:T1 Type),
( x:T1, nf x
( y:T1, nf y y < x P y) P x)
a, nf a P a.
Proof.
intros; eapply P_well_founded_induction_type; eauto.
eexact nf_Wf;auto.
Defined.

Definition transfinite_induction_Q :
(P : T1 Type) (Q : T1 Prop),
( x:T1, Q x nf x
( y:T1, Q y nf y y < x P y) P x)
a, nf a Q a P a.
Proof.
intros.
eapply P_well_founded_induction_type with (R:=lt)(P:=fun anf a Q a).
3:split;auto.
2:destruct 1; intros; eapply X; eauto.
unfold well_founded_P.
intros.
apply Acc_incl with (restrict _ nf lt).
unfold inclusion; intros.
unfold restrict.
unfold restrict in H2.
tauto.
apply nf_Wf.
case H1;auto.
Defined.

Fixpoint succ (c:T1) : T1 :=
match c with zerofinite 1
| cons zero n _cons zero (S n) zero
| cons a n bcons a n (succ b)
end.

Fixpoint pred (c:T1) : option T1 :=
match c with zeroNone
| cons zero 0 _Some zero
| cons zero (S n) _Some (cons zero n zero)
| cons a n b
match (pred b) with NoneNone
| Some cSome (cons a n c)
end
end.

Fixpoint plus (c1 c2 : T1) {struct c1}:T1 :=
match c1,c2 with
| zero, yy
| cons zero n _, zerocons zero n zero
| x, zerox
| cons zero n _, cons zero n' _cons zero (S (n+n')) zero
| cons a n b, cons a' n' b'
(match compare a a' with
| Datatypes.Ltcons a' n' b'
| Gt ⇒ (cons a n (plus b (cons a' n' b')))
| Datatypes.Eq ⇒ (cons a (S(n+n')) b')
end)
end
where "a + b" := (plus a b) : cantor_scope.

Fixpoint minus (c1 c2 : T1) {struct c1}:T1 :=
match c1,c2 with
| zero, yzero
| cons zero n _, cons zero n' _
if (le_lt_dec n n')
then zero
else cons zero (Peano.pred (n-n')) zero
| cons zero n _, zerocons zero n zero
| cons zero n _, yzero
| cons a n b, zerocons a n b
| cons a n b, cons a' n' b'
(match compare a a' with
| Datatypes.Ltzero
| Gtcons a n b
| Datatypes.Eq ⇒ (match (lt_eq_lt_dec n n') with
| inleft (left _) ⇒ zero
| inright _ ⇒ (cons a (Peano.pred (n-n')) b')
| _b - b'
end)

end)
end
where "c1 - c2" := (minus c1 c2):cantor_scope.

Lemma omega_minus_one : omega - F 1 = omega.
Proof.
reflexivity.
Qed.

Fixpoint mult (c1 c2 : T1) {struct c2}:T1 :=
match c1,c2 with
| zero, yzero
| x, zerozero
| cons zero n _, cons zero n' _
cons zero (Peano.pred((S n) × (S n'))) zero
| cons a n b, cons zero n' b'
cons a (Peano.pred((S n) × (S n'))) b
| cons a n b, cons a' n' b'
cons (a + a') n' ((cons a n b) × b')
end
where "c1 * c2" := (mult c1 c2) : cantor_scope.

Fixpoint exp_F (a:T1)(n:nat){struct n}:T1 :=
match n with
| 0 ⇒ F 1
| S pa × (exp_F a p)
end.

Fixpoint exp (a b : T1) {struct b}:T1 :=
match a,b with
| x, zerocons zero 0 zero
| cons zero 0 _ , _cons zero 0 zero
| zero, yzero
| x , cons zero n' _exp_F x (S n')
| cons zero n _, cons (cons zero 0 zero) n' b'
((cons (cons zero n' zero) 0 zero) ×
((cons zero n zero) ^ b'))
| cons zero n _, cons a' n' b'
(omega_term
(omega_term (a' - (F 1)) n')
0) ×
((cons zero n zero) ^ b')
| cons a n b, cons a' n' b'
((omega_term (a × (cons a' n' zero))
0) ×
((cons a n b) ^ b'))
end
where "a ^ b" := (exp a b) : cantor_scope.

Definition get_decomposition : c, lt zero c
{a:T1 & {n:nat & {b:T1 | c = cons a n b}}}.
intro c; case c.
intro H; elimtype False; inversion H.
intros c0 n c1; c0; n; c1;auto.
Defined.

Ltac decomp_exhib H a n b e:=
let Ha := fresh in
let Hn := fresh in
let Hb := fresh in
match type of H
with lt zero ?c
case (get_decomposition H);
intros a Ha;
case Ha;intros n Hn; case Hn; intros b e;
clear Ha Hn
end.

Lemma lt_a_phi0_a : a, a < phi0 a.
Proof.
induction a;simpl.
compute; constructor.
unfold phi0.
constructor 2.
assert (le (cons a1 0 zero) (cons a1 n a2)).
case n.
case a2.
left.
trivial.
right;constructor 4;constructor.
right;constructor 3.
auto with arith.
case H.
injection 1.
intros; subst a2;subst n;auto.
intro; eapply lt_trans; eauto.
Qed.

Lemma phi0_lt : a b, a < b phi0 a < phi0 b.
Proof.
unfold phi0;intros c c' H.
constructor 2;trivial.
Qed.

Lemma phi0_ltR : a b, phi0 a < phi0 b a < b.
Proof.
unfold phi0;intros c c' H.
case (lt_inv H).
trivial.
intros [(_,i)|(_,(_,i))]; inversion i.
Qed.

Lemma compare_ok_1:
a a', (compare a a' = Datatypes.Lt a < a')
(compare a a' = Datatypes.Eq a = a') .
Proof.
induction a;simpl.
destruct a';simpl.
split;split.
discriminate 1.
inversion 1.
auto.
auto.
split;split.
auto with T1.
auto.
discriminate 1.
discriminate 1.
destruct a'; simpl.
split; split.
discriminate 1.
inversion 1.
inversion 1.
discriminate 1.
caseEq (compare a1 a'1).
intros.
case (lt_eq_lt_dec n n0).
destruct s.
repeat split.
replace a1 with a'1.
constructor 3;auto.
case (IHa1 a'1).
intros.
case H1;auto.
intros;symmetry.
auto.
discriminate 1.
injection 1.
intros; subst n0.
absurd (n<n)%nat;auto with arith.
split.
repeat split.
intro.
subst n0.
replace a1 with a'1.
constructor 4.
case (IHa2 a'2);intros.
auto.
case H1;auto.
elim (IHa1 a'1);intros.
case H2;auto.
symmetry;auto.
subst n0.
replace a1 with a'1.
intro.
assert (lt a2 a'2).
eapply lt_inv_b;eauto.
case (IHa2 a'2);intros.
case H2;auto.
case (IHa1 a'1);intros.
case H1;auto.
intros;symmetry;auto.
replace a1 with a'1.
subst n0.
repeat split.
intros.
case (IHa2 a'2); intros.
replace a2 with a'2.
auto.
case H2;intros.
symmetry;auto.
injection 1.
intro;subst a'2.
case (IHa2 a2).
intros.
case H2;auto.
case (IHa1 a'1);intros.
case H1;intros;symmetry;auto.
intro;repeat split.
discriminate 1.
intro H0.
absurd (cons a1 n a2 < cons a'1 n0 a'2);auto.
apply lt_not_gt.
replace a1 with a'1.
constructor 3;auto.
elim (IHa1 a'1);intros.
case H2;auto.
symmetry;auto.
discriminate 1.
injection 1.
intros; subst n0; absurd (n<n)%nat;auto with arith.
intros; repeat split.
constructor 2.
case (IHa1 a'1);intros.
case H1;auto.
discriminate 1.
injection 1;intros.
subst a'1;absurd (lt a1 a1).
apply lt_irr.
case (IHa1 a1);intros.
case H3;auto.
intro;repeat split.
discriminate 1.
inversion 1.
case (IHa1 a'1);intros.
case H8;intros.
rewrite <- (H11 H2).
symmetry;auto.
absurd (cons a'1 n0 a'2 < cons a1 n a2).
apply lt_not_gt;auto.
case (IHa1 a'1);intros.
case H9;intros.
rewrite H in H11.
generalize (H11 H5).
discriminate 1.
case (IHa1 a'1);intros.
case H9;intros.
rewrite H in H11.
generalize (H11 H5).
discriminate 1.
discriminate 1.
injection 1;intros.
subst a'1; case (IHa1 a1);intros.
case H4;intros.
rewrite H in H6.
auto.
Qed.

Lemma compare_reflect : a a', match compare a a' with
| Datatypes.Lta < a'
| Datatypes.Eqa = a'
| Datatypes.Gta' < a
end.
Proof.
intros c c'; case (compare_ok_1 c c');intros H0 H1; case H0; case H1;
intros;
caseEq (compare c c'); auto.
intro comp; case (trichotomy_inf c c').
intro x; case x; intro H'.
rewrite (H4 H') in comp;discriminate comp.
rewrite (H2 H') in comp;discriminate comp.
trivial.
Qed.

Lemma compare_rw1 : a b, a < b compare a b = Datatypes.Lt.
Proof.
intros c1 c2; generalize (compare_reflect c1 c2).
case (compare c1 c2);auto.
intros e H;subst c2;case (lt_irr H).
intros H1 H2;case (lt_not_gt H2);auto.
Qed.

Lemma compare_rw2 : a, compare a a = Datatypes.Eq.
Proof.
intro c; generalize (compare_reflect c c).
case (compare c c);auto;
intro H;case (lt_irr H);auto.
Qed.

Lemma compare_rw3 : a b, b < a compare a b = Gt.
Proof.
intros c1 c2; generalize (compare_reflect c1 c2).
case (compare c1 c2);auto.
intros e H;subst c2;case (lt_irr H).
intros H1 H2;case (lt_not_gt H2);auto.
Qed.

Theorem compare_reflectR : a b : T1,
(match trichotomy_inf a b with
inleft (left _) ⇒ Datatypes.Lt
| inleft (right _) ⇒ Datatypes.Eq
| inright _Gt
end)
= compare a b.
Proof.
intros c1 c2;case (trichotomy_inf c1 c2).
destruct s; auto; try discriminate.
rewrite compare_rw1;auto.
subst c1;rewrite compare_rw2;auto.
intro; rewrite compare_rw3;auto.
Qed.

Lemma max_le_1 : a b, a max a b.
Proof.
unfold max.
intros.
rewrite <- compare_reflectR.
case (trichotomy_inf a b);auto with T1.
destruct s;auto with T1.
Qed.

Lemma max_comm : a b, max a b = max b a.
Proof.
unfold max.
intros a b; repeat rewrite <- compare_reflectR.
case ( trichotomy_inf a b); case (trichotomy_inf b a);auto with T1.
destruct s; destruct s; auto with T1.
case (lt_not_gt l);auto.
destruct s;auto with T1.
destruct s;auto with T1.
intros H H0; case (lt_not_gt H);auto.
Qed.

Lemma lt_intro : a b, compare a b = Datatypes.Lt a < b.
Proof.
intros a b; rewrite <- compare_reflectR.
case (trichotomy_inf a b);auto with T1.
destruct s; auto.
discriminate 1.
discriminate 2.
Qed.

Lemma max_dec : a b, {max a b = a}+{max a b = b}.
Proof.
unfold max; intros a b; case (trichotomy_inf a b);auto.
destruct 1.
repeat rewrite compare_rw1;auto.
subst b;repeat rewrite compare_rw2;auto.
intro; repeat rewrite compare_rw3;auto.
Qed.

Lemma max_nf : a b, nf a nf b nf (max a b).
Proof.
intros c c'; case (max_dec c c');
intro H;rewrite H;auto.
Qed.

Lemma max_assoc : a b c, max (max a b) c =
max a (max b c).
Proof.
intros c1 c2 c3.
unfold max.
case (trichotomy_inf c1 c2).
destruct 1.
repeat (rewrite (compare_rw1 l)).

case (trichotomy_inf c2 c3).
destruct 1.
repeat (rewrite (compare_rw1 l0)).
assert (lt c1 c3).
eapply lt_trans;eauto.
rewrite (compare_rw1 H);auto.
subst c3.
repeat rewrite compare_rw2.
rewrite compare_rw1;auto.
intro c'.
repeat (rewrite (compare_rw3 c')).
rewrite compare_rw1;auto.
subst c2;
repeat (rewrite (compare_rw2));auto.
case (trichotomy_inf c1 c3).
destruct 1.
repeat (rewrite (compare_rw1 l));auto.
subst c3;repeat rewrite compare_rw2;auto.
intro c;repeat (rewrite (compare_rw3 c));auto.
repeat rewrite compare_rw2;auto.
intro c; repeat rewrite (compare_rw3 c);auto.
case (trichotomy_inf c1 c3).
destruct 1.
rewrite (compare_rw1 l);auto.
assert (lt c2 c3).
eapply lt_trans;eauto.
repeat rewrite (compare_rw1 H);auto.
rewrite (compare_rw1 l);auto.
subst c3;rewrite (compare_rw2);auto.
repeat rewrite (compare_rw1 c);auto.
rewrite compare_rw2;auto.
intro.
rewrite (compare_rw3 l).
case (trichotomy_inf c2 c3).
destruct 1.
repeat rewrite (compare_rw1 l0);auto.
repeat rewrite (compare_rw3 l);auto.
subst c3;repeat rewrite (compare_rw2);auto.
repeat rewrite (compare_rw3 l);auto.
intro c';repeat rewrite (compare_rw3 c');auto.
repeat rewrite (compare_rw3 c);auto.
Qed.

Lemma succ_nf2 : c a n b, nf2 c (cons a n b)
nf2 (succ c) (cons a n b).
Proof.
induction c.
simpl.
repeat constructor.
simpl.
case c1.
repeat constructor.
intros t n0 t0 a n1 b H.
inversion_clear H.
constructor; auto.
Qed.

Lemma succ_nf : a, nf a nf (succ a).
Proof.
induction a.
simpl.
repeat constructor; auto with arith.
simpl.
generalize IHa1 ; case a1.
simpl;repeat constructor; auto.
intros c n0 c0 H H0.
apply nf_intro.
nf_inv.
apply IHa2; nf_inv.
apply succ_nf2.
eapply nf2_intro; eauto.
Qed.

Lemma lt_succ : a, a < succ a.
Proof.
intro c; elim c; simpl; auto with T1.
intro c0; case c0; simpl; auto with T1.
Qed.

Lemma phi0_log : a, a < phi0 (succ (log a)).
Proof.
destruct a.
simpl.
compute.
constructor.
simpl.
unfold phi0.
constructor 2.
apply lt_succ.
Qed.

Lemma plus_zero : a, zero + a = a.
Proof.
simpl; intro a; case a; auto.
Qed.

Lemma plus_a_zero : a, nf a a + zero = a.
Proof.
intro c; case c;simpl.
trivial.
intro c0;case c0;simpl;auto.
intros n c1 H1; rewrite (nf_of_finite H1); auto with T1.
Qed.

Lemma plus_fin_omega : n ,F n + omega = omega.
Proof.
destruct n;simpl;auto.
Qed.

Lemma plus_not_comm : {a:T1 & {b :T1 |
nf a nf a a + b b + a}}.
Proof.
(finite 1); omega.
split.
simpl;repeat constructor.
split.
compute;repeat constructor.
compute.
discriminate 1.
Defined.

Lemma succ_is_plus_one: a, nf a succ a = a + F 1.
Proof.
unfold finite.
intro c; elim c.
compute; trivial.
intro c0;case c0.
simpl.
intros H n c1 H0 H1.
rewrite <- plus_n_O; trivial.
intros c1 n c2 H n0 c3 H0 H1.
simpl.
rewrite H0; [trivial | nf_inv].
Qed.

Lemma plus_cons_cons_rw1 : a n b a' n' b',
a < a'
cons a n b + cons a' n' b' = cons a' n' b'.
Proof.
simpl.
destruct a.
destruct a'.
inversion 1.
intros; rewrite compare_rw1; auto with T1.
destruct a'.
inversion 1.
intros n' b' H; rewrite (compare_rw1);auto.
Qed.

Lemma plus_cons_cons_rw2 : a n b n' b',
nf (cons a n b)
nf (cons a n' b')
plus (cons a n b) (cons a n' b')=
cons a (S (n + n') ) b'.
Proof.
simpl.
destruct a.
intros.
rewrite (nf_of_finite H0).
auto.
rewrite (compare_rw2).
auto.
Qed.

Lemma plus_cons_cons_rw3 : a n b a' n' b',
a' < a
nf (cons a n b)
nf (cons a' n' b')
cons a n b + cons a' n' b'=
cons a n (b + (cons a' n' b')).
Proof.
simpl.
destruct a.
inversion 1.

destruct a'.
rewrite compare_rw3.
auto.
constructor.
intros;
rewrite compare_rw3.
auto.
auto.
Qed.

Lemma ap_plus : a, ap a
b c, nf b nf c b < a c < a b + c < a.
Proof.
destruct 1.
intro b; elim b.
intro c; elim c;intros.
simpl; auto with T1.
simpl.
auto.
intros c H0.
intros.
generalize c0 H2 H4.
destruct c1.
rewrite (plus_a_zero).
auto.
auto.
intros.
case (trichotomy_inf c c1_1).
destruct 1.
rewrite (plus_cons_cons_rw1 n t n0 c1_2 l).
auto.
subst c1_1.
rewrite (plus_cons_cons_rw2 H1 H5).
constructor 2.

inversion H3;auto.
inversion H8.  inversion H8.
intro H7.
rewrite (plus_cons_cons_rw3).
constructor 2.
inversion_clear H3;auto.
inversion H8.
inversion H8.  auto.
auto.
auto.
Qed.

Lemma ap_plusR : c, nf c c zero
( a b, nf a nf b a < c
b < c a + b < c)
ap c.
destruct c.
intros; absurd (zero = zero); auto.
case c2.
case n.
constructor.
intros.
generalize (H1 (cons c1 0 zero) (cons c1 n0 zero)).
clear H1;intros.
assert (nf (cons c1 0 zero)).
eapply nf_coeff_irrelevance;eauto.
assert (nf (cons c1 n0 zero)).
eapply nf_coeff_irrelevance;eauto.
assert (lt (cons c1 0 zero) (cons c1 (S n0) zero)).
constructor 3;auto with arith.
assert (lt (cons c1 n0 zero) (cons c1 (S n0) zero) ).
constructor 3;auto with arith.
generalize (H1 H2 H3 H4 H5).
intro.
rewrite plus_cons_cons_rw2 in H6.
simpl in H6.
case (lt_irr H6).
auto.
auto.
intros.
assert (nf (cons c1 n zero)).
constructor.
nf_inv.
assert (nf (cons t n0 t0)).
nf_inv.
assert (cons c1 n zero < cons c1 n (cons t n0 t0)).
constructor 4;auto with T1.
assert (lt (cons t n0 t0) (cons c1 n (cons t n0 t0))).
constructor 2.
inversion H;auto.
generalize (H1 _ _ H2 H3 H4 H5).
clear H1 H4 H5;intro.
rewrite plus_cons_cons_rw3 in H1.
simpl in H1.
case (lt_irr H1).
inversion H;auto.
auto.
auto.
Qed.

Lemma plus_nf0 : a, nf a b c, b < phi0 a
c < phi0 a
nf b nf c
nf (b + c).
Proof.
intros a Ha ; pattern a.
apply transfinite_induction.
2:assumption.
intros x Cx Hx.
destruct b; destruct c.
simpl;constructor.
simpl;auto.
intros;rewrite plus_a_zero; auto.
intros.
case (trichotomy_inf b1 c1).
destruct 1.
rewrite plus_cons_cons_rw1.
auto.
auto.
subst c1.

rewrite plus_cons_cons_rw2.
eapply nf_coeff_irrelevance;eauto.
auto.
auto.
intro; rewrite plus_cons_cons_rw3;auto.

apply nf_intro.
nf_inv.
eapply Hx with b1.
nf_inv.
inversion_clear H; auto.
inversion H3.
inversion H3.
inversion H1.
compute;auto with T1.
unfold phi0.
constructor 2;auto.

unfold phi0.
constructor 2;auto.
nf_inv.
auto.
apply nf2_phi0R.
apply ap_plus.
unfold phi0;constructor.
nf_inv.
auto.
apply nf2_phi0.
eapply nf2_intro.
eauto.
unfold phi0; constructor 2; auto.
Qed.

Lemma plus_nf : a, nf a b, nf b nf (a + b).
Proof.
intros.
case (trichotomy_inf a b).
destruct 1.
apply plus_nf0 with b; auto.
apply lt_trans with b; auto.
apply lt_a_phi0_a.
apply lt_a_phi0_a.
subst b.
apply plus_nf0 with a; auto.
apply lt_a_phi0_a.
apply lt_a_phi0_a.
intro; apply plus_nf0 with a; auto.
apply lt_a_phi0_a.
apply lt_trans with a.
auto.
apply lt_a_phi0_a.
Qed.

Lemma plus_to_cons: a n b,
nf (cons a n b) omega_term a n + b =
cons a n b.
Proof.
simpl.
destruct a.
intros n b H.
rewrite (nf_of_finite H); auto.
destruct b.
auto.
inversion_clear 1.
case (trichotomy_inf (cons a1 n a2) b1).
destruct 1.
absurd (lt b1 b1);eauto with T1.
eapply lt_trans;eauto.
subst b1.
case (lt_irr H0).
intro; rewrite compare_rw3; auto.
Qed.

Lemma plus_is_zero : a b, nf a nf b
a + b = zero a = zero
b = zero.
Proof.
destruct a;destruct b.
compute.
auto.
simpl.
discriminate 3.
intro;rewrite plus_a_zero.
discriminate 2.
auto.
simpl.
case a1;case b1.
discriminate 3.
intros c n1 c0 H H0; rewrite compare_rw1.
discriminate 1.
constructor.
intros c n1 c0 H H0; rewrite compare_rw3.
discriminate 1.
constructor.
intros c n1 c0 c3 n2 c4 H H0;
case (compare (cons c3 n2 c4) (cons c n1 c0));discriminate 1.
Qed.

Lemma lt_succ_succ : a b,
a < b nf a nf b
succ a < succ b.
Proof.
induction 1.
simpl.
case a.
constructor 3;auto with arith.
constructor 2.
constructor.
generalize H; simpl.
case a.
case a'.
inversion 1.
constructor 2.
constructor 1.
case a'.
inversion 1.
constructor 2;auto.
simpl.
case a.
constructor 3;auto with arith.
constructor 3;auto.
simpl.
case a.
intros.
assert (b'=zero).
inversion H1.
auto.
inversion H5.
subst b';inversion H.
constructor 4.
apply IHlt; nf_inv.
Qed.

Lemma lt_phi0_phi0 : a b, a < b phi0 a < phi0 b.
Proof.
unfold phi0.
constructor 2.
auto.
Qed.

Lemma le_phi0_phi0 : a b, a b phi0 a phi0 b.
Proof.
destruct 1.
subst b;left;auto.
right;unfold phi0;constructor 2.
auto.
Qed.

Lemma le_succ_succ : a b, nf a nf b
a b succ a succ b.
Proof.
destruct 3.
subst a;left;auto.
right.
apply lt_succ_succ;auto.
Qed.

Lemma lt_succ_le_R : a, nf a b, nf b
succ a b a < b .
intros c Hc; elim Hc using nf_rect.
compute.
intros.
case H0;intros.
subst b;auto with T1.
eapply lt_trans.
2:eexact H1.
auto with T1.
intros.
inversion_clear H0.

subst b; simpl; auto with T1.
simpl in H1.
eapply lt_trans.
2:eauto.
auto with T1.
intros.
simpl in H5.
case H5.
intro; subst b0.
constructor 4.
apply lt_succ;auto.
intro.
eapply lt_trans.
2:eauto.
constructor 4.
apply lt_succ;auto.
Qed.

Lemma lt_succ_le_2 : a, nf a b, nf b
a < succ b a b.
intros c Hc; elim Hc using nf_rect.
intros;apply zero_le.
intros.
generalize H0; case b;simpl.
intros.
generalize (lt_inv_nb H1).
destruct 1.
inversion H2.
case H2;intros.
inversion H4.
destruct t.

inversion 1.
inversion H3.
assert (n = n0 (n < n0)%nat).
omega.
destruct H8.
rewrite H8.
case t.
left.
auto.
right;constructor 4.
auto with T1.
right;constructor 3;auto.
inversion H3.
right;constructor 2;auto with T1.
destruct b0.
simpl.
inversion 2.
inversion H7.
simpl.
case b0_1;simpl.
inversion 2.
inversion H7.
intros.
inversion_clear H5.
right;constructor 2;auto.
right;constructor 3;auto.
case (H3 b0_2 (nf_inv2 H4) H6).
intro; subst b';left;auto.
right;constructor 4;auto.
Qed.

Lemma lt_succ_le : a, nf a b, nf b
a < b succ a b.
induction a.
intros H0 c'; case c'.
inversion 2.
destruct t.
destruct n.

intros.
inversion_clear H.
simpl.
left;auto.
inversion H2.
simpl;case n.
right;constructor 3;auto with arith.
right; constructor 3;auto with arith.
simpl;right;constructor 2; auto with T1.
inversion 3.
simpl;constructor 2;auto with T1.
generalize H6;case a1.
constructor 2;auto with T1.
constructor 2.
auto.
simpl.
case a1.
assert (S n = n' (S n < n')%nat).
omega.
case H7.
intro; subst n'.
case b'.
left;auto.
right;constructor 4;auto with T1.
right;constructor 3;auto.
intros.
right;constructor 3;auto.
subst b;generalize H0;case a1.
intro.
assert (b'=zero).
inversion_clear H3.
auto.
inversion H7.
subst b'; inversion H6.
simpl.
intros.
case (IHa2 (nf_inv2 H) b').
eapply nf_inv2;eauto.
auto.
destruct 1;left;auto.
intro;apply le_tail.
right;auto.
Qed.

Lemma minus_lt : a b, a < b a - b = zero.
induction 1;simpl.
auto.
generalize H;case a.
case a';simpl;auto.
intro H0;case (lt_irr H0).
intros.
rewrite (compare_rw1 H0).
auto.
case a.
case (le_lt_dec n n').
auto.
intro H0; absurd (n < n)%nat;auto with arith.
eauto with arith.
intros;rewrite (compare_rw2).
case (lt_eq_lt_dec n n').
destruct s.
auto.
subst n';absurd (n < n)%nat;auto with arith.
intro; absurd (n<n)%nat;eauto with arith.
case a.
case (le_lt_dec n n).
auto.
intro; absurd (n>n);auto with arith.
intros; rewrite (compare_rw2).
case (lt_eq_lt_dec n n).
destruct s.
auto.
auto.
intro; absurd (n < n)%nat;auto with arith.
Qed.

Lemma minus_a_a : a, a - a = zero.
Proof.
induction a;simpl;auto.
case a1.
case (le_lt_dec n n).
auto.
intros; absurd (n < n)%nat; auto with arith.
case (lt_eq_lt_dec n n ).
destruct s.
absurd (n < n)%nat;auto with arith.
intros;rewrite compare_rw2.
rewrite IHa2;auto.
intro; absurd (n<n)%nat;auto with arith.
Qed.

Lemma minus_le : a b, a b a - b = zero.
Proof.
destruct 1.
subst b; apply minus_a_a.
apply minus_lt;auto.
Qed.

Lemma mult_fin_omega : n,
(F (S n)) × omega = omega.
Proof.
simpl.
unfold omega;auto.
Qed.

Lemma phi0_plus_mult : a b, nf a nf b
phi0 (a + b) = phi0 a × phi0 b.
Proof.
simpl.
intro a; case a.
intro b; case b;simpl.
compute;trivial.
compute; trivial.
intros until b;case b;simpl.
case t;simpl;auto.
intro H; rewrite (nf_of_finite H).
compute;trivial.
case t;simpl.
compute;auto.
unfold phi0;auto.
Qed.

operations on T1 extend operations on nat

Lemma succ_compat : n:nat, succ (F n) = F (S n).
Proof.
destruct n; compute ; trivial.
Qed.

Lemma plus_compat: n p, F n + F p = F (n + p)%nat.
Proof.
induction n; destruct p; simpl ; auto.
rewrite <- (plus_n_O n);auto.
rewrite plus_n_Sm;auto.
Qed.

Lemma mult_compat : n p, (F n) × (F p) =
F (n × p)%nat.
Proof.
induction n; destruct p; simpl; auto.
rewrite (mult_0_r n).
compute; trivial.
Qed.

Lemma exp_F_compat :
p n, exp_F (F n) p =
F (n ^ p)%nat.
Proof.
induction p;simpl.
trivial.
intro n.
rewrite (IHp n).
rewrite mult_compat; trivial.
Qed.

Lemma exp_compat : p n, (F n) ^ (F p) =
F (n ^ p)%nat.
Proof.
induction p.
destruct n;simpl.
auto.
destruct n;auto.
destruct n;simpl.
auto.
case n.
simpl.
rewrite power_of_1.
rewrite <- plus_n_O;auto.

simpl.
intros.
replace (cons zero (S n0) zero) with (finite (S (S n0))).
2:simpl;auto.
rewrite exp_F_compat.
rewrite mult_compat.
assert ( (S (S n0) × S (S n0) ^ p) =
(S (S n0) ^ p + (S (S n0) ^ p + n0 × S (S n0) ^ p)))%nat.
ring.
rewrite H;trivial.
Qed.

Lemma mult_0_a : a, zero × a = zero.
Proof.
induction a;simpl;auto.
Qed.

Lemma mult_a_0 : a, a × zero = zero.
Proof.
simple induction a; simpl.
auto.
destruct t;auto.
Qed.

Lemma mult_1_a : a, nf a (F 1) × a = a.
induction a.
simpl.
trivial.
simpl.

simpl in IHa2.
intro.
caseEq a1.
intro.
subst a1.
rewrite (nf_of_finite H).
rewrite <- (plus_n_O n).
auto.
intros.
subst a1.
unfold finite in IHa2.
rewrite IHa2.
auto.
nf_inv.
Qed.

Lemma mult_a_1 : a, nf a a × (F 1) = a.
induction a.
simpl.
trivial.
simpl.

simpl in IHa2.
intro.
caseEq a1.
intro.
subst a1.
rewrite mult_1_r.
rewrite (nf_of_finite H).
auto.
intros.
subst a1.
rewrite mult_1_r;auto.
Qed.

Lemma exp_fin_omega : n, (F (S (S n)))^ omega = omega.
Proof.
reflexivity.
Qed.

Lemma omega_exp_rw : a, nf a omega ^ a = phi0 a.
Proof.
unfold omega, phi0;simpl.
intro a; elim a; simpl.
trivial.
destruct t.
simpl.
intros.
generalize (nf_of_finite H1).
intro; subst t.
case n;simpl.
auto.
simpl.
induction n0;simpl.
auto.
rewrite IHn0.
simpl.
auto.
intros.
unfold omega_term.
rewrite H0.
fold (phi0 t).
fold (phi0 (cons (cons t1 n t2) n0 t)).
fold (phi0 (cons (cons t1 n t2) n0 zero)).
rewrite <- (plus_to_cons H1).
rewrite phi0_plus_mult.
unfold omega_term;auto.
unfold omega_term;constructor.
nf_inv.
nf_inv.
nf_inv.
Qed.

Lemma omega_term_ambiguity : a n, nf a omega_term a n =
(omega ^ a) × (F (S n)).
Proof.
intros a n H; rewrite omega_exp_rw.
simpl.
case a; simpl; unfold omega_term; auto.
rewrite <- (plus_n_O n).
auto.
rewrite <- (plus_n_O n).
auto.
auto.
Qed.

Lemma cons_ambiguity : a n b, nf(cons a n b)
cons a n b = (omega^a)*(F (S n))+b.
Proof.
intros.
rewrite <- plus_to_cons.
rewrite omega_term_ambiguity; auto.
nf_inv.
auto.
Qed.

Lemma cons_unicity : a n b a' n' b',
nf (cons a n b) nf (cons a' n' b')
(omega^a)*(F (S n))+b = (omega^a')*(F (S n'))+b'
a=a' n = n' b = b'.
Proof.
intros a n b a' n' b' N N'.
rewrite <- (cons_ambiguity N).
rewrite <- (cons_ambiguity N').
injection 1;auto.
Qed.

Theorem Cantor_normal_form :
o, zero < o nf o
{a:T1 & {n: nat &{b : T1 | o = omega ^ a × (F (S n)) + b
nf (cons a n b)
( a' n' b', nf (cons a' n' b')
o = omega ^ a' × (F (S n')) + b'
a = a' n=n' b = b' )}}}.
Proof.
intro ; case o.
intro i; case (lt_irr i).
intros a n b H H0.
a; n; b; split.
apply cons_ambiguity;auto.
split;[auto|intros a' n' b' H' e'].
apply cons_unicity;auto.
rewrite <- e'.
symmetry;apply cons_ambiguity;auto.
Defined.

Lemma trichotomy : a b, a < b a = b b < a.
Proof.
intros a b; case (trichotomy_inf a b); auto.
destruct 1;auto.
Qed.

Ltac tricho t t' Hname := case (trichotomy t t');
[auto with T1 |
auto with T1 |
intro Hname |
intros [Hname|Hname]].