+ 'leq p q = (rple p q).
+
+lemma rpprec_rple: ∀p,q. p ≺ q → p ≤ q.
+/2 width=1/
+qed.
+
+lemma rple_false: false::◊ ≤ ◊.
+/2 width=1/
+qed.
+
+lemma rple_nil: ∀p. ◊ ≤ p.
+* // /2 width=1/
+qed.
+
+lemma rple_comp: ∀p1,p2. p1 ≤ p2 → ∀b. (b::p1) ≤ (b::p2).
+#p1 #p2 #H elim H -p2 // /3 width=3/
+qed.