+++ /dev/null
-(**************************************************************************)
-(* ___ *)
-(* ||M|| *)
-(* ||A|| A project by Andrea Asperti *)
-(* ||T|| *)
-(* ||I|| Developers: *)
-(* ||T|| The HELM team. *)
-(* ||A|| http://helm.cs.unibo.it *)
-(* \ / *)
-(* \ / This file is distributed under the terms of the *)
-(* v GNU General Public License Version 2 *)
-(* *)
-(**************************************************************************)
-
-include "ground_2/notation/relations/ringeq_3.ma".
-include "ground_2/lib/list.ma".
-
-(* EXTENSIONAL EQUIVALENCE OF LISTS *****************************************)
-
-rec definition eq_list A (l1,l2:list A) on l1 ≝
-match l1 with
-[ nil ⇒
- match l2 with
- [ nil ⇒ ⊤
- | cons _ _ ⇒ ⊥
- ]
-| cons a1 l1 ⇒
- match l2 with
- [ nil ⇒ ⊥
- | cons a2 l2 ⇒ a1 = a2 ∧ eq_list A l1 l2
- ]
-].
-
-interpretation "extensional equivalence (list)"
- 'RingEq A l1 l2 = (eq_list A l1 l2).
-
-(* Basic properties *********************************************************)
-
-lemma eq_list_refl (A): reflexive … (eq_list A).
-#A #l elim l -l /2 width=1 by conj/
-qed.
-
-(* Main properties **********************************************************)
-
-theorem eq_eq_list (A,l1,l2): l1 = l2 → l1 ≗{A} l2.
-// qed.
-
-(* Main inversion propertiess ***********************************************)
-
-theorem eq_list_inv_eq (A,l1,l2): l1 ≗{A} l2 → l1 = l2.
-#A #l1 elim l1 -l1 [| #a1 #l1 #IH ] *
-[ //
-| #a2 #l2 #H elim H
-| #H elim H
-| #a2 #l2 * #Ha #Hl /3 width=1 by eq_f2/
-]
-qed-.