--- /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 *)
+(* *)
+(**************************************************************************)
+
+
+
+(* INSERT RELATION FOR CONTEXTS
+*)
+
+include "Lift/defs.ma".
+include "datatypes_defs/Context.ma".
+
+inductive Insert (p,q:Proof) (S:Sequent):
+ Nat \to Context \to Context \to Prop \def
+ | insert_zero: \forall P. Insert p q S zero P (abst P p q S)
+ | insert_succ: \forall P,Q,i. Insert p q S i P Q \to
+ \forall p1,p2. Lift i (succ zero) p1 p2 \to
+ \forall q1,q2. Lift i (succ zero) q1 q2 \to \forall R.
+ Insert p q S (succ i) (abst P p1 q1 R) (abst Q p2 q2 R)
+.