(* File: Rev_App.v  (last edited on 27/10/2000) (c) Klaus Weich  *)
Require Export In_NGamma.
(*******************************************************************)
(* Decorated nested implications are pairs of a nested implication *)
(* and a counter-model of the premisses.                           *)
Definition decorated_nested_imp := (nimp * kripke_tree)%type.
Definition decorated_nested_imps := list decorated_nested_imp.
Definition DNI_NIL := nil (A:=decorated_nested_imp).
Definition decorated_nested_imp2nimp (x : decorated_nested_imp) :=
match x with
| (x0, _) => x0
end.
Definition decorated_nested_imp2k (x : decorated_nested_imp) :=
match x with
| (_, k) => k
end.
Definition decorated_nested_imp2form (x : decorated_nested_imp) :=
nimp2form (decorated_nested_imp2nimp x).
Fixpoint rev_app (ds : decorated_nested_imps) :
nested_imps -> nested_imps :=
match ds with
| nil => fun ni : nested_imps => ni
| (x, k) :: ds => fun ni : nested_imps => rev_app ds (Decorated x k :: ni)
end.
intros dni; elim dni; clear dni.
intros ni; simpl in |- *.
trivial.
intros a; case a; clear a.
intros x k dni ih ni.
simpl in |- *.
rewrite (ih (Decorated x k :: ni)).
rewrite (ih (Decorated x k :: NNil)).
symmetry  in |- *.
apply (app_ass (rev_app dni NNil) (Decorated x k :: NNil) ni).
Qed.

Lemma in_app_or_ni :
forall (x : nested_imp) (ni1 ni2 : nested_imps),
In x (ni1 ++ ni2) -> In x ni1 \/ In x ni2.