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 include "basics/relations.ma".
17 (* ADDITIONAL PROPERTIES OF RELATIONS ***************************************)
19 lemma replace2: ∀A,B:Type[0]. ∀R:relation2 A B. ∀x1,y1,x2,y2.
20 R x1 x2 → y1 = x1 → y2 = x2 → R y1 y2.