1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 (* LOGIC ********************************************************************)
17 include "ground/xoa/ex_4_1.ma".
19 (* Constructions with ex4 ***************************************************)
21 lemma ex4_commute (A0) (P0,P1,P2,P3:A0→Prop):
22 (∃∃x0. P0 x0 & P1 x0 & P2 x0 & P3 x0) → ∃∃x0. P2 x0 & P3 x0 & P0 x0 & P1 x0.
23 #A0 #P0 #P1 #P2 #P3 * /2 width=5 by ex4_intro/