# Library Coq.Reals.RList

Require Import Rbase.
Require Import Rfunctions.
Open Local Scope R_scope.

Inductive Rlist : Type :=
| nil : Rlist
| cons : R -> Rlist -> Rlist.

Fixpoint In (x:R) (l:Rlist) {struct l} : Prop :=
match l with
| nil => False
| cons a l' => x = a \/ In x l'
end.

Fixpoint Rlength (l:Rlist) : nat :=
match l with
| nil => 0%nat
| cons a l' => S (Rlength l')
end.

Fixpoint MaxRlist (l:Rlist) : R :=
match l with
| nil => 0
| cons a l1 =>
match l1 with
| nil => a
| cons a' l2 => Rmax a (MaxRlist l1)
end
end.

Fixpoint MinRlist (l:Rlist) : R :=
match l with
| nil => 1
| cons a l1 =>
match l1 with
| nil => a
| cons a' l2 => Rmin a (MinRlist l1)
end
end.

Lemma MaxRlist_P1 : forall (l:Rlist) (x:R), In x l -> x <= MaxRlist l.
Proof.
intros; induction l as [| r l Hrecl].
simpl in H; elim H.
induction l as [| r0 l Hrecl0].
simpl in H; elim H; intro.
simpl in |- *; right; assumption.
elim H0.
replace (MaxRlist (cons r (cons r0 l))) with (Rmax r (MaxRlist (cons r0 l))).
simpl in H; decompose [or] H.
rewrite H0; apply RmaxLess1.
unfold Rmax in |- *; case (Rle_dec r (MaxRlist (cons r0 l))); intro.
apply Hrecl; simpl in |- *; tauto.
apply Rle_trans with (MaxRlist (cons r0 l));
[ apply Hrecl; simpl in |- *; tauto | left; auto with real ].
unfold Rmax in |- *; case (Rle_dec r (MaxRlist (cons r0 l))); intro.
apply Hrecl; simpl in |- *; tauto.
apply Rle_trans with (MaxRlist (cons r0 l));
[ apply Hrecl; simpl in |- *; tauto | left; auto with real ].
reflexivity.
Qed.

Fixpoint AbsList (l:Rlist) (x:R) {struct l} : Rlist :=
match l with
| nil => nil
| cons a l' => cons (Rabs (a - x) / 2) (AbsList l' x)
end.

Lemma MinRlist_P1 : forall (l:Rlist) (x:R), In x l -> MinRlist l <= x.
Proof.
intros; induction l as [| r l Hrecl].
simpl in H; elim H.
induction l as [| r0 l Hrecl0].
simpl in H; elim H; intro.
simpl in |- *; right; symmetry in |- *; assumption.
elim H0.
replace (MinRlist (cons r (cons r0 l))) with (Rmin r (MinRlist (cons r0 l))).
simpl in H; decompose [or] H.
rewrite H0; apply Rmin_l.
unfold Rmin in |- *; case (Rle_dec r (MinRlist (cons r0 l))); intro.
apply Rle_trans with (MinRlist (cons r0 l)).
assumption.
apply Hrecl; simpl in |- *; tauto.
apply Hrecl; simpl in |- *; tauto.
apply Rle_trans with (MinRlist (cons r0 l)).
apply Rmin_r.
apply Hrecl; simpl in |- *; tauto.
reflexivity.
Qed.

Lemma AbsList_P1 :
forall (l:Rlist) (x y:R), In y l -> In (Rabs (y - x) / 2) (AbsList l x).
Proof.
intros; induction l as [| r l Hrecl].
elim H.
simpl in |- *; simpl in H; elim H; intro.
left; rewrite H0; reflexivity.
right; apply Hrecl; assumption.
Qed.

Lemma MinRlist_P2 :
forall l:Rlist, (forall y:R, In y l -> 0 < y) -> 0 < MinRlist l.
Proof.
intros; induction l as [| r l Hrecl].
apply Rlt_0_1.
induction l as [| r0 l Hrecl0].
simpl in |- *; apply H; simpl in |- *; tauto.
replace (MinRlist (cons r (cons r0 l))) with (Rmin r (MinRlist (cons r0 l))).
unfold Rmin in |- *; case (Rle_dec r (MinRlist (cons r0 l))); intro.
apply H; simpl in |- *; tauto.
apply Hrecl; intros; apply H; simpl in |- *; simpl in H0; tauto.
reflexivity.
Qed.

Lemma AbsList_P2 :
forall (l:Rlist) (x y:R),
In y (AbsList l x) -> exists z : R, In z l /\ y = Rabs (z - x) / 2.
Proof.
intros; induction l as [| r l Hrecl].
elim H.
elim H; intro.
exists r; split.
simpl in |- *; tauto.
assumption.
assert (H1 := Hrecl H0); elim H1; intros; elim H2; clear H2; intros;
exists x0; simpl in |- *; simpl in H2; tauto.
Qed.

Lemma MaxRlist_P2 :
forall l:Rlist, (exists y : R, In y l) -> In (MaxRlist l) l.
Proof.
intros; induction l as [| r l Hrecl].
simpl in H; elim H; trivial.
induction l as [| r0 l Hrecl0].
simpl in |- *; left; reflexivity.
change (In (Rmax r (MaxRlist (cons r0 l))) (cons r (cons r0 l))) in |- *;
unfold Rmax in |- *; case (Rle_dec r (MaxRlist (cons r0 l)));
intro.
right; apply Hrecl; exists r0; left; reflexivity.
left; reflexivity.
Qed.

Fixpoint pos_Rl (l:Rlist) (i:nat) {struct l} : R :=
match l with
| nil => 0
| cons a l' => match i with
| O => a
| S i' => pos_Rl l' i'
end
end.

Lemma pos_Rl_P1 :
forall (l:Rlist) (a:R),
(0 < Rlength l)%nat ->
pos_Rl (cons a l) (Rlength l) = pos_Rl l (pred (Rlength l)).
Proof.
intros; induction l as [| r l Hrecl];
[ elim (lt_n_O _ H)
| simpl in |- *; case (Rlength l); [ reflexivity | intro; reflexivity ] ].
Qed.

Lemma pos_Rl_P2 :
forall (l:Rlist) (x:R),
In x l <-> (exists i : nat, (i < Rlength l)%nat /\ x = pos_Rl l i).
Proof.
intros; induction l as [| r l Hrecl].
split; intro;
[ elim H | elim H; intros; elim H0; intros; elim (lt_n_O _ H1) ].
split; intro.
elim H; intro.
exists 0%nat; split;
[ simpl in |- *; apply lt_O_Sn | simpl in |- *; apply H0 ].
elim Hrecl; intros; assert (H3 := H1 H0); elim H3; intros; elim H4; intros;
exists (S x0); split;
[ simpl in |- *; apply lt_n_S; assumption | simpl in |- *; assumption ].
elim H; intros; elim H0; intros; elim (zerop x0); intro.
rewrite a in H2; simpl in H2; left; assumption.
right; elim Hrecl; intros; apply H4; assert (H5 : S (pred x0) = x0).
symmetry in |- *; apply S_pred with 0%nat; assumption.
exists (pred x0); split;
[ simpl in H1; apply lt_S_n; rewrite H5; assumption | rewrite <- H5 in H2; simpl in H2; assumption ].
Qed.

Lemma Rlist_P1 :
forall (l:Rlist) (P:R -> R -> Prop),
(forall x:R, In x l -> exists y : R, P x y) ->
exists l' : Rlist,
Rlength l = Rlength l' /\
(forall i:nat, (i < Rlength l)%nat -> P (pos_Rl l i) (pos_Rl l' i)).
Proof.
intros; induction l as [| r l Hrecl].
exists nil; intros; split;
[ reflexivity | intros; simpl in H0; elim (lt_n_O _ H0) ].
assert (H0 : In r (cons r l)).
simpl in |- *; left; reflexivity.
assert (H1 := H _ H0);
assert (H2 : forall x:R, In x l -> exists y : R, P x y).
intros; apply H; simpl in |- *; right; assumption.
assert (H3 := Hrecl H2); elim H1; intros; elim H3; intros; exists (cons x x0);
intros; elim H5; clear H5; intros; split.
simpl in |- *; rewrite H5; reflexivity.
intros; elim (zerop i); intro.
rewrite a; simpl in |- *; assumption.
assert (H8 : i = S (pred i)).
apply S_pred with 0%nat; assumption.
rewrite H8; simpl in |- *; apply H6; simpl in H7; apply lt_S_n; rewrite <- H8;
assumption.
Qed.

Definition ordered_Rlist (l:Rlist) : Prop :=
forall i:nat, (i < pred (Rlength l))%nat -> pos_Rl l i <= pos_Rl l (S i).

Fixpoint insert (l:Rlist) (x:R) {struct l} : Rlist :=
match l with
| nil => cons x nil
| cons a l' =>
match Rle_dec a x with
| left _ => cons a (insert l' x)
| right _ => cons x l
end
end.

Fixpoint cons_Rlist (l k:Rlist) {struct l} : Rlist :=
match l with
| nil => k
| cons a l' => cons a (cons_Rlist l' k)
end.

Fixpoint cons_ORlist (k l:Rlist) {struct k} : Rlist :=
match k with
| nil => l
| cons a k' => cons_ORlist k' (insert l a)
end.

Fixpoint app_Rlist (l:Rlist) (f:R -> R) {struct l} : Rlist :=
match l with
| nil => nil
| cons a l' => cons (f a) (app_Rlist l' f)
end.

Fixpoint mid_Rlist (l:Rlist) (x:R) {struct l} : Rlist :=
match l with
| nil => nil
| cons a l' => cons ((x + a) / 2) (mid_Rlist l' a)
end.

Definition Rtail (l:Rlist) : Rlist :=
match l with
| nil => nil
| cons a l' => l'
end.

Definition FF (l:Rlist) (f:R -> R) : Rlist :=
match l with
| nil => nil
| cons a l' => app_Rlist (mid_Rlist l' a) f
end.

Lemma RList_P0 :
forall (l:Rlist) (a:R),
pos_Rl (insert l a) 0 = a \/ pos_Rl (insert l a) 0 = pos_Rl l 0.
Proof.
intros; induction l as [| r l Hrecl];
[ left; reflexivity
| simpl in |- *; case (Rle_dec r a); intro;
[ right; reflexivity | left; reflexivity ] ].
Qed.

Lemma RList_P1 :
forall (l:Rlist) (a:R), ordered_Rlist l -> ordered_Rlist (insert l a).
Proof.
intros; induction l as [| r l Hrecl].
simpl in |- *; unfold ordered_Rlist in |- *; intros; simpl in H0;
elim (lt_n_O _ H0).
simpl in |- *; case (Rle_dec r a); intro.
assert (H1 : ordered_Rlist l).
unfold ordered_Rlist in |- *; unfold ordered_Rlist in H; intros;
assert (H1 : (S i < pred (Rlength (cons r l)))%nat);
[ simpl in |- *; replace (Rlength l) with (S (pred (Rlength l)));
[ apply lt_n_S; assumption | symmetry in |- *; apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro; rewrite <- H1 in H0; simpl in H0; elim (lt_n_O _ H0) ]
| apply (H _ H1) ].
assert (H2 := Hrecl H1); unfold ordered_Rlist in |- *; intros;
induction i as [| i Hreci].
simpl in |- *; assert (H3 := RList_P0 l a); elim H3; intro.
rewrite H4; assumption.
induction l as [| r1 l Hrecl0];
[ simpl in |- *; assumption | rewrite H4; apply (H 0%nat); simpl in |- *; apply lt_O_Sn ].
simpl in |- *; apply H2; simpl in H0; apply lt_S_n;
replace (S (pred (Rlength (insert l a)))) with (Rlength (insert l a));
[ assumption | apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro; rewrite <- H3 in H0; elim (lt_n_O _ H0) ].
unfold ordered_Rlist in |- *; intros; induction i as [| i Hreci];
[ simpl in |- *; auto with real | change (pos_Rl (cons r l) i <= pos_Rl (cons r l) (S i)) in |- *; apply H; simpl in H0; simpl in |- *; apply (lt_S_n _ _ H0) ].
Qed.

Lemma RList_P2 :
forall l1 l2:Rlist, ordered_Rlist l2 -> ordered_Rlist (cons_ORlist l1 l2).
Proof.
simple induction l1;
[ intros; simpl in |- *; apply H | intros; simpl in |- *; apply H; apply RList_P1; assumption ].
Qed.

Lemma RList_P3 :
forall (l:Rlist) (x:R),
In x l <-> (exists i : nat, x = pos_Rl l i /\ (i < Rlength l)%nat).
Proof.
intros; split; intro;
[ induction l as [| r l Hrecl] | induction l as [| r l Hrecl] ].
elim H.
elim H; intro;
[ exists 0%nat; split; [ apply H0 | simpl in |- *; apply lt_O_Sn ]
| elim (Hrecl H0); intros; elim H1; clear H1; intros; exists (S x0); split;
[ apply H1 | simpl in |- *; apply lt_n_S; assumption ] ].
elim H; intros; elim H0; intros; elim (lt_n_O _ H2).
simpl in |- *; elim H; intros; elim H0; clear H0; intros;
induction x0 as [| x0 Hrecx0];
[ left; apply H0
| right; apply Hrecl; exists x0; split;
[ apply H0 | simpl in H1; apply lt_S_n; assumption ] ].
Qed.

Lemma RList_P4 :
forall (l1:Rlist) (a:R), ordered_Rlist (cons a l1) -> ordered_Rlist l1.
Proof.
intros; unfold ordered_Rlist in |- *; intros; apply (H (S i)); simpl in |- *;
replace (Rlength l1) with (S (pred (Rlength l1)));
[ apply lt_n_S; assumption | symmetry in |- *; apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro; rewrite <- H1 in H0; elim (lt_n_O _ H0) ].
Qed.

Lemma RList_P5 :
forall (l:Rlist) (x:R), ordered_Rlist l -> In x l -> pos_Rl l 0 <= x.
Proof.
intros; induction l as [| r l Hrecl];
[ elim H0
| simpl in |- *; elim H0; intro;
[ rewrite H1; right; reflexivity
| apply Rle_trans with (pos_Rl l 0);
[ apply (H 0%nat); simpl in |- *; induction l as [| r0 l Hrecl0];
[ elim H1 | simpl in |- *; apply lt_O_Sn ]
| apply Hrecl; [ eapply RList_P4; apply H | assumption ] ] ] ].
Qed.

Lemma RList_P6 :
forall l:Rlist,
ordered_Rlist l <->
(forall i j:nat,
(i <= j)%nat -> (j < Rlength l)%nat -> pos_Rl l i <= pos_Rl l j).
Proof.
simple induction l; split; intro.
intros; right; reflexivity.
unfold ordered_Rlist in |- *; intros; simpl in H0; elim (lt_n_O _ H0).
intros; induction i as [| i Hreci];
[ induction j as [| j Hrecj];
[ right; reflexivity
| simpl in |- *; apply Rle_trans with (pos_Rl r0 0);
[ apply (H0 0%nat); simpl in |- *; simpl in H2; apply neq_O_lt;
red in |- *; intro; rewrite <- H3 in H2;
assert (H4 := lt_S_n _ _ H2); elim (lt_n_O _ H4)
| elim H; intros; apply H3;
[ apply RList_P4 with r; assumption | apply le_O_n | simpl in H2; apply lt_S_n; assumption ] ] ]
| induction j as [| j Hrecj];
[ elim (le_Sn_O _ H1)
| simpl in |- *; elim H; intros; apply H3;
[ apply RList_P4 with r; assumption | apply le_S_n; assumption | simpl in H2; apply lt_S_n; assumption ] ] ].
unfold ordered_Rlist in |- *; intros; apply H0;
[ apply le_n_Sn | simpl in |- *; simpl in H1; apply lt_n_S; assumption ].
Qed.

Lemma RList_P7 :
forall (l:Rlist) (x:R),
ordered_Rlist l -> In x l -> x <= pos_Rl l (pred (Rlength l)).
Proof.
intros; assert (H1 := RList_P6 l); elim H1; intros H2 _; assert (H3 := H2 H);
clear H1 H2; assert (H1 := RList_P3 l x); elim H1;
clear H1; intros; assert (H4 := H1 H0); elim H4; clear H4;
intros; elim H4; clear H4; intros; rewrite H4;
assert (H6 : Rlength l = S (pred (Rlength l))).
apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro;
rewrite <- H6 in H5; elim (lt_n_O _ H5).
apply H3;
[ rewrite H6 in H5; apply lt_n_Sm_le; assumption | apply lt_pred_n_n; apply neq_O_lt; red in |- *; intro; rewrite <- H7 in H5; elim (lt_n_O _ H5) ].
Qed.

Lemma RList_P8 :
forall (l:Rlist) (a x:R), In x (insert l a) <-> x = a \/ In x l.
Proof.
simple induction l.
intros; split; intro; simpl in H; apply H.
intros; split; intro;
[ simpl in H0; generalize H0; case (Rle_dec r a); intros;
[ simpl in H1; elim H1; intro;
[ right; left; assumption
| elim (H a x); intros; elim (H3 H2); intro;
[ left; assumption | right; right; assumption ] ]
| simpl in H1; decompose [or] H1;
[ left; assumption | right; left; assumption | right; right; assumption ] ]
| simpl in |- *; case (Rle_dec r a); intro;
[ simpl in H0; decompose [or] H0;
[ right; elim (H a x); intros; apply H3; left | left | right; elim (H a x); intros; apply H3; right ]
| simpl in H0; decompose [or] H0; [ left | right; left | right; right ] ];
assumption ].
Qed.

Lemma RList_P9 :
forall (l1 l2:Rlist) (x:R), In x (cons_ORlist l1 l2) <-> In x l1 \/ In x l2.
Proof.
simple induction l1.
intros; split; intro;
[ simpl in H; right; assumption
| simpl in |- *; elim H; intro; [ elim H0 | assumption ] ].
intros; split.
simpl in |- *; intros; elim (H (insert l2 r) x); intros; assert (H3 := H1 H0);
elim H3; intro;
[ left; right; assumption
| elim (RList_P8 l2 r x); intros H5 _; assert (H6 := H5 H4); elim H6; intro;
[ left; left; assumption | right; assumption ] ].
intro; simpl in |- *; elim (H (insert l2 r) x); intros _ H1; apply H1;
elim H0; intro;
[ elim H2; intro;
[ right; elim (RList_P8 l2 r x); intros _ H4; apply H4; left; assumption | left; assumption ]
| right; elim (RList_P8 l2 r x); intros _ H3; apply H3; right; assumption ].
Qed.

Lemma RList_P10 :
forall (l:Rlist) (a:R), Rlength (insert l a) = S (Rlength l).
Proof.
intros; induction l as [| r l Hrecl];
[ reflexivity
| simpl in |- *; case (Rle_dec r a); intro;
[ simpl in |- *; rewrite Hrecl; reflexivity | reflexivity ] ].
Qed.

Lemma RList_P11 :
forall l1 l2:Rlist,
Rlength (cons_ORlist l1 l2) = (Rlength l1 + Rlength l2)%nat.
Proof.
simple induction l1;
[ intro; reflexivity | intros; simpl in |- *; rewrite (H (insert l2 r)); rewrite RList_P10; apply INR_eq; rewrite S_INR; do 2 rewrite plus_INR; rewrite S_INR; ring ].
Qed.

Lemma RList_P12 :
forall (l:Rlist) (i:nat) (f:R -> R),
(i < Rlength l)%nat -> pos_Rl (app_Rlist l f) i = f (pos_Rl l i).
Proof.
simple induction l;
[ intros; elim (lt_n_O _ H)
| intros; induction i as [| i Hreci];
[ reflexivity | simpl in |- *; apply H; apply lt_S_n; apply H0 ] ].
Qed.

Lemma RList_P13 :
forall (l:Rlist) (i:nat) (a:R),
(i < pred (Rlength l))%nat ->
pos_Rl (mid_Rlist l a) (S i) = (pos_Rl l i + pos_Rl l (S i)) / 2.
Proof.
simple induction l.
intros; simpl in H; elim (lt_n_O _ H).
simple induction r0.
intros; simpl in H0; elim (lt_n_O _ H0).
intros; simpl in H1; induction i as [| i Hreci].
reflexivity.
change
(pos_Rl (mid_Rlist (cons r1 r2) r) (S i) =
(pos_Rl (cons r1 r2) i + pos_Rl (cons r1 r2) (S i)) / 2)
in |- *; apply H0; simpl in |- *; apply lt_S_n; assumption.
Qed.

Lemma RList_P14 : forall (l:Rlist) (a:R), Rlength (mid_Rlist l a) = Rlength l.
Proof.
simple induction l; intros;
[ reflexivity | simpl in |- *; rewrite (H r); reflexivity ].
Qed.

Lemma RList_P15 :
forall l1 l2:Rlist,
ordered_Rlist l1 ->
ordered_Rlist l2 ->
pos_Rl l1 0 = pos_Rl l2 0 -> pos_Rl (cons_ORlist l1 l2) 0 = pos_Rl l1 0.
Proof.
intros; apply Rle_antisym.
induction l1 as [| r l1 Hrecl1];
[ simpl in |- *; simpl in H1; right; symmetry in |- *; assumption
| elim (RList_P9 (cons r l1) l2 (pos_Rl (cons r l1) 0)); intros;
assert
(H4 :
In (pos_Rl (cons r l1) 0) (cons r l1) \/ In (pos_Rl (cons r l1) 0) l2);
[ left; left; reflexivity
| assert (H5 := H3 H4); apply RList_P5;
[ apply RList_P2; assumption | assumption ] ] ].
induction l1 as [| r l1 Hrecl1];
[ simpl in |- *; simpl in H1; right; assumption
| assert
(H2 :
In (pos_Rl (cons_ORlist (cons r l1) l2) 0) (cons_ORlist (cons r l1) l2));
[ elim
(RList_P3 (cons_ORlist (cons r l1) l2)
(pos_Rl (cons_ORlist (cons r l1) l2) 0));
intros; apply H3; exists 0%nat; split;
[ reflexivity | rewrite RList_P11; simpl in |- *; apply lt_O_Sn ]
| elim (RList_P9 (cons r l1) l2 (pos_Rl (cons_ORlist (cons r l1) l2) 0));
intros; assert (H5 := H3 H2); elim H5; intro;
[ apply RList_P5; assumption | rewrite H1; apply RList_P5; assumption ] ] ].
Qed.

Lemma RList_P16 :
forall l1 l2:Rlist,
ordered_Rlist l1 ->
ordered_Rlist l2 ->
pos_Rl l1 (pred (Rlength l1)) = pos_Rl l2 (pred (Rlength l2)) ->
pos_Rl (cons_ORlist l1 l2) (pred (Rlength (cons_ORlist l1 l2))) =
pos_Rl l1 (pred (Rlength l1)).
Proof.
intros; apply Rle_antisym.
induction l1 as [| r l1 Hrecl1].
simpl in |- *; simpl in H1; right; symmetry in |- *; assumption.
assert
(H2 :
In
(pos_Rl (cons_ORlist (cons r l1) l2)
(pred (Rlength (cons_ORlist (cons r l1) l2))))
(cons_ORlist (cons r l1) l2));
[ elim
(RList_P3 (cons_ORlist (cons r l1) l2)
(pos_Rl (cons_ORlist (cons r l1) l2)
(pred (Rlength (cons_ORlist (cons r l1) l2)))));
intros; apply H3; exists (pred (Rlength (cons_ORlist (cons r l1) l2)));
split; [ reflexivity | rewrite RList_P11; simpl in |- *; apply lt_n_Sn ]
| elim
(RList_P9 (cons r l1) l2
(pos_Rl (cons_ORlist (cons r l1) l2)
(pred (Rlength (cons_ORlist (cons r l1) l2)))));
intros; assert (H5 := H3 H2); elim H5; intro;
[ apply RList_P7; assumption | rewrite H1; apply RList_P7; assumption ] ].
induction l1 as [| r l1 Hrecl1].
simpl in |- *; simpl in H1; right; assumption.
elim
(RList_P9 (cons r l1) l2 (pos_Rl (cons r l1) (pred (Rlength (cons r l1)))));
intros;
assert
(H4 :
In (pos_Rl (cons r l1) (pred (Rlength (cons r l1)))) (cons r l1) \/
In (pos_Rl (cons r l1) (pred (Rlength (cons r l1)))) l2);
[ left; change (In (pos_Rl (cons r l1) (Rlength l1)) (cons r l1)) in |- *;
elim (RList_P3 (cons r l1) (pos_Rl (cons r l1) (Rlength l1)));
intros; apply H5; exists (Rlength l1); split;
[ reflexivity | simpl in |- *; apply lt_n_Sn ]
| assert (H5 := H3 H4); apply RList_P7;
[ apply RList_P2; assumption
| elim
(RList_P9 (cons r l1) l2
(pos_Rl (cons r l1) (pred (Rlength (cons r l1)))));
intros; apply H7; left;
elim
(RList_P3 (cons r l1)
(pos_Rl (cons r l1) (pred (Rlength (cons r l1)))));
intros; apply H9; exists (pred (Rlength (cons r l1)));
split; [ reflexivity | simpl in |- *; apply lt_n_Sn ] ] ].
Qed.

Lemma RList_P17 :
forall (l1:Rlist) (x:R) (i:nat),
ordered_Rlist l1 ->
In x l1 ->
pos_Rl l1 i < x -> (i < pred (Rlength l1))%nat -> pos_Rl l1 (S i) <= x.
Proof.
simple induction l1.
intros; elim H0.
intros; induction i as [| i Hreci].
simpl in |- *; elim H1; intro;
[ simpl in H2; rewrite H4 in H2; elim (Rlt_irrefl _ H2)
| apply RList_P5; [ apply RList_P4 with r; assumption | assumption ] ].
simpl in |- *; simpl in H2; elim H1; intro.
rewrite H4 in H2; assert (H5 : r <= pos_Rl r0 i);
[ apply Rle_trans with (pos_Rl r0 0);
[ apply (H0 0%nat); simpl in |- *; simpl in H3; apply neq_O_lt;
red in |- *; intro; rewrite <- H5 in H3; elim (lt_n_O _ H3)
| elim (RList_P6 r0); intros; apply H5;
[ apply RList_P4 with r; assumption
| apply le_O_n
| simpl in H3; apply lt_S_n; apply lt_trans with (Rlength r0);
[ apply H3 | apply lt_n_Sn ] ] ]
| elim (Rlt_irrefl _ (Rle_lt_trans _ _ _ H5 H2)) ].
apply H; try assumption;
[ apply RList_P4 with r; assumption
| simpl in H3; apply lt_S_n;
replace (S (pred (Rlength r0))) with (Rlength r0);
[ apply H3 | apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro; rewrite <- H5 in H3; elim (lt_n_O _ H3) ] ].
Qed.

Lemma RList_P18 :
forall (l:Rlist) (f:R -> R), Rlength (app_Rlist l f) = Rlength l.
Proof.
simple induction l; intros;
[ reflexivity | simpl in |- *; rewrite H; reflexivity ].
Qed.

Lemma RList_P19 :
forall l:Rlist,
l <> nil -> exists r : R, (exists r0 : Rlist, l = cons r r0).
Proof.
intros; induction l as [| r l Hrecl];
[ elim H; reflexivity | exists r; exists l; reflexivity ].
Qed.

Lemma RList_P20 :
forall l:Rlist,
(2 <= Rlength l)%nat ->
exists r : R,
(exists r1 : R, (exists l' : Rlist, l = cons r (cons r1 l'))).
Proof.
intros; induction l as [| r l Hrecl];
[ simpl in H; elim (le_Sn_O _ H)
| induction l as [| r0 l Hrecl0];
[ simpl in H; elim (le_Sn_O _ (le_S_n _ _ H)) | exists r; exists r0; exists l; reflexivity ] ].
Qed.

Lemma RList_P21 : forall l l':Rlist, l = l' -> Rtail l = Rtail l'.
Proof.
intros; rewrite H; reflexivity.
Qed.

Lemma RList_P22 :
forall l1 l2:Rlist, l1 <> nil -> pos_Rl (cons_Rlist l1 l2) 0 = pos_Rl l1 0.
Proof.
simple induction l1; [ intros; elim H; reflexivity | intros; reflexivity ].
Qed.

Lemma RList_P23 :
forall l1 l2:Rlist,
Rlength (cons_Rlist l1 l2) = (Rlength l1 + Rlength l2)%nat.
Proof.
simple induction l1;
[ intro; reflexivity | intros; simpl in |- *; rewrite H; reflexivity ].
Qed.

Lemma RList_P24 :
forall l1 l2:Rlist,
l2 <> nil ->
pos_Rl (cons_Rlist l1 l2) (pred (Rlength (cons_Rlist l1 l2))) =
pos_Rl l2 (pred (Rlength l2)).
Proof.
simple induction l1.
intros; reflexivity.
intros; rewrite <- (H l2 H0); induction l2 as [| r1 l2 Hrecl2].
elim H0; reflexivity.
do 2 rewrite RList_P23;
replace (Rlength (cons r r0) + Rlength (cons r1 l2))%nat with
(S (S (Rlength r0 + Rlength l2)));
[ replace (Rlength r0 + Rlength (cons r1 l2))%nat with
(S (Rlength r0 + Rlength l2));
[ reflexivity | simpl in |- *; apply INR_eq; rewrite S_INR; do 2 rewrite plus_INR; rewrite S_INR; ring ]
| simpl in |- *; apply INR_eq; do 3 rewrite S_INR; do 2 rewrite plus_INR;
rewrite S_INR; ring ].
Qed.

Lemma RList_P25 :
forall l1 l2:Rlist,
ordered_Rlist l1 ->
ordered_Rlist l2 ->
pos_Rl l1 (pred (Rlength l1)) <= pos_Rl l2 0 ->
ordered_Rlist (cons_Rlist l1 l2).
Proof.
simple induction l1.
intros; simpl in |- *; assumption.
simple induction r0.
intros; simpl in |- *; simpl in H2; unfold ordered_Rlist in |- *; intros;
simpl in H3.
induction i as [| i Hreci].
simpl in |- *; assumption.
change (pos_Rl l2 i <= pos_Rl l2 (S i)) in |- *; apply (H1 i); apply lt_S_n;
replace (S (pred (Rlength l2))) with (Rlength l2);
[ assumption | apply S_pred with 0%nat; apply neq_O_lt; red in |- *; intro; rewrite <- H4 in H3; elim (lt_n_O _ H3) ].
intros; clear H; assert (H : ordered_Rlist (cons_Rlist (cons r1 r2) l2)).
apply H0; try assumption.
apply RList_P4 with r; assumption.
unfold ordered_Rlist in |- *; intros; simpl in H4;
induction i as [| i Hreci].
simpl in |- *; apply (H1 0%nat); simpl in |- *; apply lt_O_Sn.
change
(pos_Rl (cons_Rlist (cons r1 r2) l2) i <=
pos_Rl (cons_Rlist (cons r1 r2) l2) (S i)) in |- *;
apply (H i); simpl in |- *; apply lt_S_n; assumption.
Qed.

Lemma RList_P26 :
forall (l1 l2:Rlist) (i:nat),
(i < Rlength l1)%nat -> pos_Rl (cons_Rlist l1 l2) i = pos_Rl l1 i.
Proof.
simple induction l1.
intros; elim (lt_n_O _ H).
intros; induction i as [| i Hreci].
apply RList_P22; discriminate.
apply (H l2 i); simpl in H0; apply lt_S_n; assumption.
Qed.

Lemma RList_P27 :
forall l1 l2 l3:Rlist,
cons_Rlist l1 (cons_Rlist l2 l3) = cons_Rlist (cons_Rlist l1 l2) l3.
Proof.
simple induction l1; intros;
[ reflexivity | simpl in |- *; rewrite (H l2 l3); reflexivity ].
Qed.

Lemma RList_P28 : forall l:Rlist, cons_Rlist l nil = l.
Proof.
simple induction l;
[ reflexivity | intros; simpl in |- *; rewrite H; reflexivity ].
Qed.

Lemma RList_P29 :
forall (l2 l1:Rlist) (i:nat),
(Rlength l1 <= i)%nat ->
(i < Rlength (cons_Rlist l1 l2))%nat ->
pos_Rl (cons_Rlist l1 l2) i = pos_Rl l2 (i - Rlength l1).
Proof.
simple induction l2.
intros; rewrite RList_P28 in H0; elim (lt_irrefl _ (le_lt_trans _ _ _ H H0)).
intros;
replace (cons_Rlist l1 (cons r r0)) with
(cons_Rlist (cons_Rlist l1 (cons r nil)) r0).
inversion H0.
rewrite <- minus_n_n; simpl in |- *; rewrite RList_P26.
clear l2 r0 H i H0 H1 H2; induction l1 as [| r0 l1 Hrecl1].
reflexivity.
simpl in |- *; assumption.
rewrite RList_P23; rewrite plus_comm; simpl in |- *; apply lt_n_Sn.
replace (S m - Rlength l1)%nat with (S (S m - S (Rlength l1))).
rewrite H3; simpl in |- *;
replace (S (Rlength l1)) with (Rlength (cons_Rlist l1 (cons r nil))).
apply (H (cons_Rlist l1 (cons r nil)) i).
rewrite RList_P23; rewrite plus_comm; simpl in |- *; rewrite <- H3;
apply le_n_S; assumption.
repeat rewrite RList_P23; simpl in |- *; rewrite RList_P23 in H1;
rewrite plus_comm in H1; simpl in H1; rewrite (plus_comm (Rlength l1));
simpl in |- *; rewrite plus_comm; apply H1.
rewrite RList_P23; rewrite plus_comm; reflexivity.
change (S (m - Rlength l1) = (S m - Rlength l1)%nat) in |- *;
apply minus_Sn_m; assumption.
replace (cons r r0) with (cons_Rlist (cons r nil) r0);
[ symmetry in |- *; apply RList_P27 | reflexivity ].
Qed.