update in ground_2 and models

[helm.git] / matita / matita / contribs / lambdadelta / ground_2 / lib / functions.ma

diff --git a/matita/matita/contribs/lambdadelta/ground_2/lib/functions.ma b/matita/matita/contribs/lambdadelta/ground_2/lib/functions.ma
index 4276e1a6cf7a204a929ec2f4c869d215cd3b04e6..4977504b9e988a440fa7d5fb0de75a3e0b247a66 100644 (file)
--- a/matita/matita/contribs/lambdadelta/ground_2/lib/functions.ma
+++ b/matita/matita/contribs/lambdadelta/ground_2/lib/functions.ma
@@ -20,6 +20,10 @@ definition left_identity (A) (f): predicate A ≝ λi. ∀a:A. a = f i a.
 
 definition right_identity (A) (f): predicate A ≝ λi. ∀a:A. a = f a i.
 
+definition compatible_2 (A) (B): relation3 … (relation A) (relation B) ≝
+                                 λf,Sa,Sb.
+                                 ∀a1,a2. Sa a1 a2 → Sb (f a1) (f a2).
+
 definition compatible_3 (A) (B) (C): relation4 … (relation A) (relation B) (relation C) ≝
                                      λf,Sa,Sb,Sc.
                                      ∀a1,a2. Sa a1 a2 → ∀b1,b2. Sb b1 b2 → Sc (f a1 b1) (f a2 b2).