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(*       ___                                                              *)
(*      ||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                  *)
(*                                                                        *)
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include "ground_2/notation/functions/oplus_4.ma".
include "ground_2/lib/list2.ma".

(* LISTS OF PAIRS ***********************************************************)

rec definition append2 A1 A2 (l1,l2:list2 A1 A2) on l1 ≝ match l1 with
[ nil2           ⇒ l2
| cons2 a1 a2 tl ⇒ {a1, a2} ⨮ append2 A1 A2 tl l2
].

interpretation "append (list of pairs)"
   'OPlus A1 A2 l1 l2 = (append2 A1 A2 l1 l2).