X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Flib%2Fbasics%2Frelations.ma;h=8b746ef6896d4f58bb4efa17728a27b7f8bba0e7;hb=5e24c923ea53c31c3e167c4ff7851877ded646c1;hp=ed5130955886e557a1e11b8c83b09f7ad649cb48;hpb=2a5e0b799cd6aae5d920c67a5ddc9d9888cf7e80;p=helm.git

diff --git a/matita/matita/lib/basics/relations.ma b/matita/matita/lib/basics/relations.ma
index ed5130955..8b746ef68 100644
--- a/matita/matita/lib/basics/relations.ma
+++ b/matita/matita/lib/basics/relations.ma
@@ -48,6 +48,9 @@ definition tight_apart: ∀A.∀eq,ap:relation A.Prop
 definition antisymmetric: ∀A.∀R:relation A.Prop
 ≝ λA.λR.∀x,y:A. R x y → ¬(R y x).
 
+definition singlevalued: ∀A,B. predicate (relation2 A B) ≝ λA,B,R.
+                         ∀a,b1. R a b1 → ∀b2. R a b2 → b1 = b2.
+
 (* Reflexive closure ************)
 
 definition RC: ∀A:Type[0]. relation A → relation A ≝