--- /dev/null
+(**************************************************************************)
+(* ___ *)
+(* ||M|| *)
+(* ||A|| A project by Andrea Asperti *)
+(* ||T|| *)
+(* ||I|| Developers: *)
+(* ||T|| The HELM team. *)
+(* ||A|| http://helm.cs.unibo.it *)
+(* \ / *)
+(* \ / This file is distributed under the terms of the *)
+(* v GNU General Public License Version 2 *)
+(* *)
+(**************************************************************************)
+
+include "apps_2/models/model_vlift.ma".
+include "apps_2/models/vdrop.ma".
+
+(* EVALUATION DROP **********************************************************)
+
+(* Advanced properties with evaluation evaluation lift **********************)
+
+lemma vlift_vdrop_eq (M): ∀lv,i. lv ≐{?,dd M} ⫯[i←lv i]⫰[i]lv.
+#M #lv #i #j elim (lt_or_eq_or_gt j i) #Hji destruct
+[ >vlift_lt // >vdrop_lt //
+| >vlift_eq //
+| >vlift_gt // >vdrop_ge /2 width=1 by monotonic_pred/
+ <(lt_succ_pred … Hji) //
+]
+qed.