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chomsky.v
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chomsky.v
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(* ---------------------------------------------------------------------
This file contains definitions and proof scripts related to
(i) closure operations for context-free grammars,
(ii) context-free grammars simplification
(iii) context-free grammar Chomsky normalization and
(iv) pumping lemma for context-free languages.
More information can be found in the paper "Formalization of the
pumping lemma for context-free languages", submitted to
LATA 2016.
Marcus Vinícius Midena Ramos
--------------------------------------------------------------------- *)
(* --------------------------------------------------------------------- *)
(* CHOMSKY NORMAL FORM *)
(* --------------------------------------------------------------------- *)
Require Import List.
Require Import Ring.
Require Import Omega.
Require Import Program.
Require Import misc_arith.
Require Import misc_list.
Require Import cfg.
Require Import inaccessible.
Require Import useless.
Require Import unitrules.
Require Import emptyrules.
Require Import simplification.
Require Import allrules.
Set Implicit Arguments.
Unset Strict Implicit.
Unset Printing Implicit Defensive.
Import ListNotations.
Open Scope list_scope.
(* --------------------------------------------------------------------- *)
(* DEFINITIONS *)
(* --------------------------------------------------------------------- *)
Section Chomsky_Definitions_1.
Variables non_terminal terminal: Type.
Notation sf:= (list (non_terminal + terminal)).
Definition is_cnf_rule (left: non_terminal) (right: sf): Prop:=
(exists s1 s2: non_terminal, right = [inl s1; inl s2]) \/
(exists t: terminal, right = [inr t]).
Definition is_cnf (g: cfg non_terminal terminal): Prop:=
forall left: non_terminal,
forall right: sf,
rules g left right -> is_cnf_rule left right.
Definition is_cnf_with_empty_rule (g: cfg non_terminal terminal): Prop:=
forall left: non_terminal,
forall right: sf,
rules g left right ->
(left = (start_symbol g) /\ right = []) \/
is_cnf_rule left right.
End Chomsky_Definitions_1.
Section Chomsky_Definitions_2.
Variables non_terminal terminal: Type.
Notation sentence := (list terminal).
Notation sf := (list (non_terminal + terminal)).
Notation ntlist:= (list non_terminal).
Notation term_lift:= ((terminal_lift non_terminal) terminal).
Notation symbol:= (non_terminal + terminal)%type.
Notation slist:= (list sf).
Notation vlist:= (list symbol).
Inductive non_terminal': Type:=
| Lift_r: sf -> non_terminal'.
Lemma nt_eqdec':
(forall (x y:terminal), {x=y}+{x<>y}) ->
(forall (x y:non_terminal), {x=y}+{x<>y}) ->
forall (x y:non_terminal'), {x=y}+{x<>y}.
Proof.
intros.
assert (forall (l1 l2:vlist), {l1=l2}+{l1<>l2}).
apply list_eq_dec; decide equality.
decide equality.
Qed.
Notation sf':= (list (non_terminal' + terminal)).
Notation ntlist':= (list non_terminal').
Notation tlist:= (list terminal).
Definition non_terminal_lift (n: non_terminal): (non_terminal + terminal):= inl n.
Definition non_terminal'_lift (n: non_terminal'): (non_terminal' + terminal):= inl n.
Definition terminal_lift' (t: terminal): (non_terminal' + terminal):= inr t.
Definition symbol_lift (s: non_terminal + terminal): non_terminal' + terminal:=
match s with
| inr t => inr t
| inl n => inl (Lift_r [inl n])
end.
Inductive g_cnf_rules (g: cfg non_terminal terminal): non_terminal' -> sf' -> Prop:=
| Lift_cnf_t: forall t: terminal,
forall left: non_terminal,
forall s1 s2: sf,
rules g left (s1++[inr t]++s2) ->
g_cnf_rules g (Lift_r [inr t]) [inr t]
| Lift_cnf_1: forall left: non_terminal,
forall t: terminal,
rules g left [inr t] ->
g_cnf_rules g (Lift_r [inl left]) [inr t]
| Lift_cnf_2: forall left: non_terminal,
forall s1 s2: symbol,
forall beta: sf,
rules g left (s1 :: s2 :: beta) ->
g_cnf_rules g (Lift_r [inl left]) [inl (Lift_r [s1]); inl (Lift_r (s2 :: beta))]
| Lift_cnf_3: forall left: sf,
forall s1 s2 s3: symbol,
forall beta: sf,
g_cnf_rules g (Lift_r left) [inl (Lift_r [s1]); inl (Lift_r (s2 :: s3 :: beta))] ->
g_cnf_rules g (Lift_r (s2 :: s3 :: beta)) [inl (Lift_r [s2]); inl (Lift_r (s3 :: beta))].
(* --------------------------------------------------------------------- *)
(* ALL NTS (non-terminals) *)
(* --------------------------------------------------------------------- *)
Fixpoint all_nts (l: slist): ntlist':=
match l with
| [] => []
| s :: l' => Lift_r s :: all_nts l'
end.
Lemma all_nts_app:
forall l1 l2: slist,
all_nts (l1 ++ l2) = all_nts l1 ++ all_nts l2.
Proof.
induction l1.
- simpl.
reflexivity.
- intros l2.
simpl.
rewrite (IHl1 l2).
reflexivity.
Qed.
Lemma all_nts_single:
forall s: symbol,
forall l1 l2: vlist,
forall n: nat,
n >= 1 ->
In (Lift_r [s]) (all_nts (all_sf_up_to n (l1 ++ s :: l2))).
Proof.
intros s l1 l2 n.
revert l2.
revert l1.
revert s.
induction n.
- intros s l1 l2 H1.
omega.
- intros s l1 l2 H1.
assert (H2: n = 0 \/ n >= 1) by omega.
destruct H2 as [H2 | H2].
+ subst.
simpl.
rewrite all_nts_app.
apply in_or_app.
left.
rewrite concat_list_app_left.
rewrite all_nts_app.
apply in_or_app.
right.
simpl.
left.
reflexivity.
+ simpl.
rewrite all_nts_app.
apply in_or_app.
right.
apply IHn.
exact H2.
Qed.
Fixpoint all_nts_up_to (n: nat) (v: vlist): ntlist':=
match n with
| 0 => [Lift_r []]
| S n' => all_nts (all_sf_with n v) ++ all_nts_up_to n' v
end.
Lemma all_nts_up_to_correct_aux:
forall n: nat,
forall s: symbol,
forall v: vlist,
forall s0: sf,
In s v ->
In s0 (all_sf_with n v) ->
In (Lift_r (s :: s0)) (all_nts (concat_list v (all_sf_with n v))).
Proof.
induction n.
- intros s v s0 H1 H2.
simpl in H2.
destruct H2 as [H2 | H2].
+ subst.
simpl.
apply in_split in H1.
destruct H1 as [l1 [l2 H1]].
subst.
assert (H: In [s] (concat_list (l1 ++ s :: l2) [[]])).
{
apply concat_list_empty.
}
apply in_split in H.
destruct H as [l0 [l3 H]].
rewrite H.
rewrite all_nts_app.
apply in_or_app.
right.
simpl.
left.
reflexivity.
+ contradiction.
- intros s v s0 H1 H2.
simpl.
simpl in H2.
apply in_split in H2.
destruct H2 as [l1 [l2 H2]].
rewrite H2.
apply in_split in H1.
destruct H1 as [l1' [l2' H1]].
rewrite H1.
assert (H3: In (s :: s0) (concat_list (l1' ++ s :: l2') (l1 ++ s0 :: l2))).
{
apply concat_list_non_empty.
}
apply in_split in H3.
destruct H3 as [l0 [l3 H3]].
rewrite H3.
rewrite all_nts_app.
apply in_or_app.
right.
simpl.
left.
reflexivity.
Qed.
Lemma all_nts_up_to_correct:
forall n: nat,
forall s: sf,
forall v: vlist,
(forall e: symbol, In e s -> In e v) ->
length s <= n ->
In (Lift_r s) (all_nts_up_to n v).
Proof.
induction n.
- intros s v H1 H2.
assert (length s = 0) by omega.
apply length_zero in H.
subst.
simpl.
left.
reflexivity.
- intros s v H1 H2.
simpl.
apply in_or_app.
assert (H3: length s = S n \/ length s <= n) by omega.
clear H2.
destruct H3 as [H3 | H3].
+ left.
destruct s.
* simpl in H3.
omega.
* {
apply all_nts_up_to_correct_aux.
- apply H1.
simpl.
left.
reflexivity.
- simpl in H3.
apply eq_add_S in H3.
apply all_sf_with_correct.
+ intros e H4.
apply H1.
simpl.
right.
exact H4.
+ exact H3.
}
+ right.
apply IHn.
* exact H1.
* exact H3.
Qed.
Lemma rules_g_cnf_to_rules_g_right:
forall g: cfg _ _,
forall right2: sf,
forall n1 n2: non_terminal',
forall s1 s2: symbol,
g_cnf_rules g n1 [inl n2; inl (Lift_r (s1 :: s2 :: right2))] ->
exists left: non_terminal,
exists right1: sf,
rules g left (right1 ++ s1 :: s2 :: right2).
Proof.
intros g right2 n1 n2 s1 s2 H.
remember [inl n2; inl (Lift_r (s1 :: s2 :: right2))] as w.
generalize n2 s1 s2 right2 Heqw.
clear n2 s1 s2 right2 Heqw.
induction H.
- intros n2 s1' s2' right2 H'.
inversion H'.
- intros n2 s1' s2' right2 H2'.
inversion H2'.
- intros n2 s0 s3 right2 H2.
inversion H2.
destruct n2.
inversion H1.
destruct beta.
+ inversion H4.
+ inversion H4.
subst.
exists left.
exists [s1].
exact H.
- intros n2 s0 s4 right2 H1.
inversion H1.
destruct n2.
destruct beta.
+ inversion H4.
+ inversion H4.
subst.
inversion H1.
subst.
clear H H1 H2 H4.
specialize (IHg_cnf_rules (Lift_r [s1]) s2 s0 (s4 :: right2)).
specialize (IHg_cnf_rules (eq_refl ([inl (Lift_r [s1]); inl (Lift_r (s2 :: s0 :: s4 :: right2))]))).
destruct IHg_cnf_rules as [left0 [right1 H]].
exists left0.
exists (right1 ++ [s2]).
rewrite <- app_assoc.
exact H.
Qed.
Lemma rules_g_cnf_to_rules_g_left:
forall g: cfg _ _,
forall s1: sf,
forall s2: sf',
g_cnf_rules g (Lift_r s1) s2 ->
(exists t: terminal, s1 = [inr t]
/\ exists left s1 s2, rules g left (s1++[inr t]++s2)
) \/
(exists n: non_terminal, s1 = [inl n]
/\ exists right, rules g n right
) \/
(exists left: non_terminal,
exists right s3 s4: sf,
rules g left right /\
right = s3 ++ s1 ++ s4).
Proof.
intros g s1 s2 H.
inversion H.
- subst.
left.
exists t.
split; [reflexivity|].
eauto.
- subst.
right.
left.
exists left.
split; [reflexivity|eauto].
- subst.
right.
left.
exists left.
split; [reflexivity|eauto].
- subst.
right.
right.
apply rules_g_cnf_to_rules_g_right in H1.
destruct H1 as [left0 [right1 H1]].
exists left0.
exists (right1 ++ s3 :: s4 :: beta).
exists right1.
exists (@nil (non_terminal + terminal)).
split.
+ exact H1.
+ rewrite app_nil_r.
reflexivity.
Qed.
Lemma g_cnf_right_formats:
forall g: cfg _ _,
forall left: non_terminal',
forall right: sf',
g_cnf_rules g left right ->
(exists t: terminal, right = [inr t]) \/
(exists s1: symbol,
exists s: sf,
right = [inl (Lift_r [s1]); inl (Lift_r s)]).
Proof.
intros g left right H.
inversion H.
- subst.
left.
exists t.
reflexivity.
- subst.
left.
exists t.
reflexivity.
- subst.
right.
destruct s1.
+ exists (inl terminal n).
exists (s2 :: beta).
simpl.
reflexivity.
+ exists (inr non_terminal t).
exists (s2 :: beta).
simpl.
reflexivity.
- subst.
right.
destruct s2.
+ exists (inl terminal n).
exists (s3 :: beta).
simpl.
reflexivity.
+ exists (inr non_terminal t).
exists (s3 :: beta).
simpl.
reflexivity.
Qed.
Lemma is_cnf_right_formats_v1:
forall g: cfg non_terminal' terminal,
forall left: non_terminal',
forall right: sf',
is_cnf g ->
rules g left right ->
(exists t: terminal, right = [inr t]) \/
(exists s1 s2: sf,
right = [inl (Lift_r s1); inl (Lift_r s2)]).
Proof.
intros g left right H1 H2.
specialize (H1 left right H2).
destruct H1 as [H1 | H1].
- destruct H1 as [s1 [s2 H1]].
right.
destruct s1, s2.
exists l.
exists l0.
exact H1.
- destruct H1 as [t H1].
left.
exists t.
exact H1.
Qed.
Lemma cnf_rules_not_empty:
forall g: cfg _ _,
forall n: non_terminal,
forall s: sf,
is_cnf g \/ is_cnf_with_empty_rule g ->
n <> start_symbol g ->
rules g n s ->
s <> [].
Proof.
intros g n s H1 H2 H3.
destruct H1 as [H1 | H1].
- specialize (H1 n s H3).
destruct H1 as [H1 | H1].
+ destruct H1 as [s1 [s2 H1]].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
+ destruct H1 as [t H1].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
- specialize (H1 n s H3).
destruct H1 as [H1 | H1].
+ destruct H1 as [H1 _].
contradiction.
+ destruct H1 as [H1 | H1].
* destruct H1 as [s1 [s2 H1]].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
* destruct H1 as [t H1].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
Qed.
Lemma cnf_derives_not_empty:
forall g: cfg _ _,
forall s1 s2: sf,
is_cnf g \/ is_cnf_with_empty_rule g ->
start_symbol_not_in_rhs g ->
~ In (inl (start_symbol g)) s1 ->
s1 <> [] ->
derives g s1 s2 ->
s2 <> [].
Proof.
intros g s1 s2 H1 H2 H3 H4 H5.
apply derives_equiv_derives6 in H5.
destruct H5 as [n0 H5].
revert s1 s2 H3 H4 H5.
induction n0.
- intros n s H3 H4 H5.
inversion H5.
subst.
exact H4.
- intros s1 s2 H3 H4 H5.
inversion H5.
subst.
clear H4 H5.
specialize (IHn0 (s0 ++ right ++ s3) s2).
assert (H7: ~ In (inl (start_symbol g)) (s0 ++ right ++ s3)).
{
intros H4.
apply H3.
apply in_app_or in H4.
destruct H4 as [H4 | H4].
- apply in_or_app.
left.
exact H4.
- apply in_app_or in H4.
destruct H4 as [H4 | H4].
+ specialize (H2 left right H0).
contradiction.
+ apply in_or_app.
right.
apply in_or_app.
right.
exact H4.
}
assert (H8: right <> []).
{
destruct H1 as [H1 | H1].
- specialize (H1 left right H0).
destruct H1 as [H1 | H1].
+ destruct H1 as [s1' [s2' H1]].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
+ destruct H1 as [t H1].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
- specialize (H1 left right H0).
destruct H1 as [H1 | H1].
+ destruct H1 as [H1a H1b].
subst.
intros _.
apply H3.
apply in_or_app.
right.
simpl.
left.
reflexivity.
+ destruct H1 as [H1 | H1].
* destruct H1 as [s1' [s2' H1]].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
* destruct H1 as [t H1].
rewrite H1.
apply not_eq_sym.
apply nil_cons.
}
assert (H9: s0 ++ right ++ s3 <> []).
{
apply app_not_nil_inv.
right.
apply app_not_nil_inv.
left.
exact H8.
}
specialize (IHn0 H7 H9 H6).
exact IHn0.
Qed.
(*
Lemma cnf_derives_not_empty_v2:
forall g: cfg _ _,
forall s1 s2: sf,
is_cnf g \/ is_cnf_with_empty_rule g ->
start_symbol_not_in_rhs g ->
~ In (inl (start_symbol g)) s1 ->
s1 <> [] ->
derives g s1 s2 ->
s2 <> [].
Proof.
intros g s1 s2 H1 H2 H3 H4 H5.
destruct s1.
- destruct H3.
destruct H4.
reflexivity.
- change (s :: s1) with ([s] ++ s1) in H5.
apply derives_split in H5.
destruct H5 as [s1' [s2' [H5 [H6 H7]]]].
destruct s.
+ apply cnf_derives_not_empty_v1 in H6.
* {
destruct s1'.
- destruct H6.
reflexivity.
- rewrite H5.
apply app_not_nil_inv.
left.
apply not_eq_sym.
apply nil_cons.
}
* exact H1.
* exact H2.
* intros H8.
apply H3.
rewrite H8.
simpl.
left.
reflexivity.
+ change [inr t] with (map (@inr non_terminal terminal) [t]) in H6.
apply derives_sentence_left in H6.
rewrite H6 in H5.
rewrite H5.
simpl.
apply not_eq_sym.
apply nil_cons.
Qed.
*)
Lemma is_cnf_right_formats_v2:
forall g: cfg non_terminal' terminal,
forall left: non_terminal',
forall right: sf',
is_cnf g \/ is_cnf_with_empty_rule g ->
rules g left right ->
right <> [] ->
(exists t: terminal, right = [inr t]) \/
(exists s1 s2: sf,
right = [inl (Lift_r s1); inl (Lift_r s2)]).
Proof.
intros g left right H1 H2 H3.
destruct H1 as [H1 | H1].
- specialize (H1 left right H2).
destruct H1 as [H1 | H1].
+ destruct H1 as [s1 [s2 H1]].
right.
destruct s1, s2.
exists l.
exists l0.
exact H1.
+ destruct H1 as [t H1].
left.
exists t.
exact H1.
- specialize (H1 left right H2).
destruct H1 as [H1 | H1].
+ destruct H1 as [H1 H4].
contradiction.
+ destruct H1 as [H1 | H1].
* destruct H1 as [s1 [s2 H1]].
right.
destruct s1, s2.
exists l l0.
exact H1.
* destruct H1 as [t H1].
left.
exists t.
exact H1.
Qed.
Lemma g_cnf_finite:
forall g: cfg non_terminal terminal,
exists n: nat,
exists ntl: ntlist',
exists tl: tlist,
In (Lift_r [inl (start_symbol g)]) ntl /\
forall left: non_terminal',
forall right: sf',
g_cnf_rules g left right ->
(length right <= n) /\
(In left ntl) /\
(forall s: non_terminal', In (inl s) right -> In s ntl) /\
(forall s: terminal, In (inr s) right -> In s tl).
Proof.
intros g.
destruct (rules_finite g) as [n [ntl [tl H1]]].
exists 2.
exists (all_nts_up_to (S n) (map non_terminal_lift ntl ++ map term_lift tl)).
exists tl.
split.
- (* start_symbol is in the list *)
destruct H1 as [H1 _].
apply all_nts_up_to_correct.
+ intros e H2.
simpl in H2.
destruct H2 as [H2 | H2].
* subst.
apply in_or_app.
left.
apply in_map.
exact H1.
* contradiction.
+ simpl.
omega.
- split.
+ (* length rhs <= 2 *)
inversion H.
* simpl.
omega.
* simpl.
omega.
* simpl.
omega.
* simpl.
omega.
+ split.
* (* non-terminals in the lhs are in the list *)
destruct left.
{
apply all_nts_up_to_correct.
- intros e H2.
apply rules_g_cnf_to_rules_g_left in H.
destruct H as [H | [H | H]].
+ destruct H as [t [H [left [s1 [s2 Hg]]]]].
subst.
simpl in H2.
destruct H2 as [H2 | H2].
* subst.
apply in_or_app; right.
apply in_map.
destruct H1 as [_ H1].
specialize (H1 left (s1 ++ [inr t] ++ s2) Hg).
apply H1.
apply in_or_app.
right.
simpl.
left.
reflexivity.
* contradiction.
+ destruct H as [n0 [H [r Hright]]].
subst.
simpl in H2.
destruct H2 as [H2 | H2].
* subst.
unfold rules_finite_def in H1.
apply in_or_app; left.
apply in_map.
destruct H1 as [_ H1].
specialize (H1 n0 r Hright).
destruct H1 as [_ [H1 _]].
exact H1.
* contradiction.
+ destruct H as [left [right0 [s3 [s4 [H3 H4]]]]].
apply in_split in H2.
destruct H2 as [l1 [l2 H2]].
subst.
rewrite <- app_assoc in H3.
unfold rules_finite_def in H1.
destruct H1 as [_ H1].
specialize (H1 left (s3 ++ l1 ++ (e :: l2) ++ s4) H3).
destruct H1 as [_ [_ [H1 H2]]].
destruct e.
* apply in_or_app.
left.
apply in_map.
apply H1.
apply in_or_app.
right.
apply in_or_app.
right.
simpl.
left.
reflexivity.
* apply in_or_app.
right.
apply in_map.
apply H2.
apply in_or_app.
right.
apply in_or_app.
right.
simpl.
left.
reflexivity.
- apply rules_g_cnf_to_rules_g_left in H.
destruct H as [H | [H | H]].
+ destruct H as [t [H _]].
subst.
simpl.
omega.
+ destruct H as [n0 [H _]].
subst.
simpl.
omega.
+ destruct H as [left [right0 [s3 [s4 [H H2]]]]].
subst.
unfold rules_finite_def in H1.
destruct H1 as [_ H1].
specialize (H1 left (s3 ++ l ++ s4) H).
destruct H1 as [H1 _].
repeat rewrite app_length in H1.
omega.
}
* {
split.
- (* non-terminals in the rhs are in the list *)
destruct H1 as [_ H1].
inversion H.
+ subst.
intros s H2.
simpl in H2.
destruct H2 as [H2 | H2].
* inversion H2.
* contradiction.
+ subst.
intros s H2.
simpl in H2.
destruct H2 as [H2 | H2].
* inversion H2.
* contradiction.
+ subst.
intros s H2.
simpl in H2.
destruct H2 as [H2 | [H2 | H2]].
* inversion H2.
{
apply all_nts_up_to_correct.
- intros e H5.
destruct e, s1.
+ simpl in H5.
destruct H5 as [H5 | H5].
* inversion H5.
subst.
apply in_or_app.
left.
apply in_map.
specialize (H1 left0 (inl n0 :: s2 :: beta) H0).
destruct H1 as [_ [_ [H1 _]]].
apply H1.
simpl.
left.
reflexivity.
* contradiction.
+ simpl in H5.
destruct H5 as [H5 | H5].
* inversion H5.
* contradiction.
+ simpl in H5.
destruct H5 as [H5 | H5].
* inversion H5.
* contradiction.
+ simpl in H5.
destruct H5 as [H5 | H5].
* inversion H5.
subst.
apply in_or_app.
right.
apply in_map.
specialize (H1 left0 (inr t :: s2 :: beta) H0).
destruct H1 as [_ [_ [_ H1]]].
apply H1.
simpl.
left.
reflexivity.
* contradiction.
- simpl.
omega.
}
* inversion H2.
{
apply all_nts_up_to_correct.
- intros e H3.
simpl in H3.
destruct H3 as [H3 | H3].
+ subst.
destruct e.
* apply in_or_app.
left.
apply in_map.
specialize (H1 left0 (s1 :: inl n0 :: beta) H0).
destruct H1 as [_ [_ [H1 _]]].
apply H1.
simpl.
right.
left.
reflexivity.
* apply in_or_app.
right.
apply in_map.
specialize (H1 left0 (s1 :: inr t :: beta) H0).
destruct H1 as [_ [_ [_ H1]]].
apply H1.
simpl.
right.
left.
reflexivity.
+ apply in_split in H3.
destruct H3 as [l1 [l2 H3]].
subst.
apply in_or_app.
destruct e.
* left.
apply in_map.
specialize (H1 left0 (s1 :: s2 :: l1 ++ inl n0 :: l2) H0).
destruct H1 as [_ [_ [H1 _]]].
apply H1.
simpl.
right.
right.
apply in_or_app.
right.
simpl.
left.
reflexivity.
* right.
apply in_map.
specialize (H1 left0 (s1 :: s2 :: l1 ++ inr t :: l2) H0).
destruct H1 as [_ [_ [_ H1]]].
apply H1.
simpl.
right.
right.
apply in_or_app.
right.
simpl.
left.
reflexivity.
- specialize (H1 left0 (s1 :: s2 :: beta) H0).
destruct H1 as [H1 _].
simpl in H1.
simpl.
omega.
}
* contradiction.
+ apply rules_g_cnf_to_rules_g_right in H0.
destruct H0 as [left1 [right1 H0]].
intros s H4.
simpl in H4.
destruct H4 as [H4 | [H4 | H4]].
* inversion H4.
{
apply all_nts_up_to_correct.
- intros e H7.
destruct e, s2.
+ apply in_or_app.
left.
apply in_map.
simpl in H7.
destruct H7 as [H7 | H7].
* inversion H7.
subst.
specialize (H1 left1 (right1 ++ inl n0 :: s3 :: beta) H0).
destruct H1 as [_ [_ [H1 _]]].
apply H1.
apply in_or_app.
right.
simpl.
left.
reflexivity.
* contradiction.
+ simpl in H7.
destruct H7 as [H7 | H7].
* inversion H7.
* contradiction.
+ simpl in H7.
destruct H7 as [H7 | H7].
* inversion H7.
* contradiction.
+ simpl in H7.
destruct H7 as [H7 | H7].
* inversion H7.
subst.
apply in_or_app.
right.
specialize (H1 left1 (right1 ++ inr t :: s3 :: beta) H0).
destruct H1 as [_ [_ [_ H1]]].
apply in_map.
apply H1.
apply in_or_app.
right.
simpl.
left.
reflexivity.
* contradiction.
- simpl.
omega.
}
* inversion H4.
{
apply all_nts_up_to_correct.