+(**************************************************************************)
+(* ___ *)
+(* ||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 *)
+(* *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/LOGIC/datatypes_defs/Sequent".
+
+(* SEQUENTS
+ - Naming policy:
+ - left hand sides (lhs): A C
+ - right hand sides (rhs): B D
+ - sequents : R S
+*)
+
+include "datatypes_defs/Formula.ma".
+
+inductive LHS: Type \def
+ | lleaf: LHS
+ | labst: LHS \to Formula \to LHS
+.
+
+inductive RHS: Type \def
+ | rleaf: RHS
+ | rabst: Formula \to RHS \to RHS
+.
+
+inductive Sequent: Type \def
+ | pair: LHS \to RHS \to Sequent
+.
+
+definition linj: Formula \to LHS \def labst lleaf.
+
+definition rinj: Formula \to RHS \def \lambda b. rabst b rleaf.
+
+coercion cic:/matita/LOGIC/datatypes_defs/Sequent/linj.con.
+
+coercion cic:/matita/LOGIC/datatypes_defs/Sequent/rinj.con.