interpretation "append (local environment)" 'Append L1 L2 = (append L1 L2).
+definition l_appendable_sn: predicate (lenv→relation term) ≝ λR.
+ ∀K,T1,T2. R K T1 T2 → ∀L. R (L @@ K) T1 T2.
+
(* Basic properties *********************************************************)
lemma append_atom_sn: ∀L. ⋆ @@ L = L.