(* File: Lt_Ks.v  (last edited on 27/10/2000) (c) Klaus Weich  *)
Require Export Le.
Require Export Lt.
Require Export Le_Ks.
Fixpoint count_undecs (n : nested_imps) : nat :=
match n with
| nil => 0
| Undecorated _ :: n => S (count_undecs n)
| Decorated _ _ :: n => count_undecs n
end.
Inductive Lt_Ks (ni1 : nested_imps) (dni1 : decorated_nested_imps)
(ni2 : nested_imps) (dni2 : decorated_nested_imps) : Set :=
| lt_ks_count_undecs :
le_ni (rev_app dni1 ni1) (rev_app dni2 ni2) ->
count_undecs ni1 < count_undecs ni2 -> Lt_Ks ni1 dni1 ni2 dni2
| lt_ks_length :
le_ni (rev_app dni1 ni1) (rev_app dni2 ni2) ->
length ni1 < length ni2 -> Lt_Ks ni1 dni1 ni2 dni2.
intros ni1 ni2 le12.
elim le12; clear le12 ni1 ni2.
trivial.
intros x ni1 ni2 le ih; simpl in |- *.
apply le_n_S; assumption.
intros x k ni1 ni2 le ih; simpl in |- *.
apply le_trans with (count_undecs ni2).
assumption.
apply le_n_Sn.
intros x k ni1 ni2 le ih; simpl in |- *.
assumption.
Qed.
intros dni; elim dni; clear dni.
intros; trivial.
intros x; case x; clear x.
intros x k dni ih ni.
simpl in |- *.
apply (ih (Decorated x k :: ni)).
Qed.
intros ni1 dni1 ni2 dni2 le12.
generalize (le_ni_le_count_undecs (rev_app dni1 ni1) (rev_app dni2 ni2) le12);
clear le12.
rewrite (count_undecs_rev_app dni1 ni1).
rewrite (count_undecs_rev_app dni2 ni2).
trivial.
Qed.
intros P step.
cut
(forall (n m : nat) (ni : nested_imps) (dni : decorated_nested_imps),
count_undecs ni < n -> length ni < m -> P (rev_app dni ni)).
intros claim ni.
apply
claim
with
(n := S (count_undecs ni))
(m := S (length ni))
(ni := ni)
(dni := DNI_NIL); clear claim.
apply lt_n_Sn.
apply lt_n_Sn.
intros n; elim n; clear n.
intros m ni dni lt_nonref lt_length.
elimtype False.
inversion_clear lt_nonref.
intros n ih m.
elim m; clear m.
intros ni dni lt_nonref lt_length.
elimtype False.
inversion_clear lt_length.
intros m sih ni dni lt_nonref lt_length.
apply step; clear step.
intros ni1 dni1 lt_ks.
inversion_clear lt_ks.
apply ih with (S (length ni1)); clear ih.
apply lt_S_n.
apply le_lt_trans with (count_undecs ni); assumption.
apply lt_n_Sn.
apply sih.
apply le_lt_trans with (count_undecs ni).
apply le_ks_le_count_undecs with dni1 dni; assumption.
assumption.
apply lt_le_trans with (length ni).
assumption.
apply lt_n_Sm_le; assumption.
Qed.
intros ni ni1 dni dni1 x k le.
apply lt_ks_count_undecs.
apply le_ni_trans with (rev_app ((x, k) :: dni) ni); try assumption.
simpl in |- *.
rewrite (rev_app_app dni (Decorated x k :: ni)).
rewrite (rev_app_app dni (Undecorated x :: ni)).
apply le_ni_app_dn.
trivial.
apply le_ni_refl.
apply le_lt_trans with (count_undecs ni).
apply le_ks_le_count_undecs with dni1 ((x, k) :: dni); assumption.
simpl in |- *; apply lt_n_Sn.
Qed.

Lemma lt_ks_shift_dd :
forall (ni : nested_imps) (dni : decorated_nested_imps)
(x : nimp) (k : kripke_tree),
Lt_Ks ni ((x, k) :: dni) (Decorated x k :: ni) dni.