--- /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 "datatypes/Nat.ma".
+
+inductive NPlus (p:Nat): Nat \to Nat \to Prop \def
+ | nplus_zero_2: NPlus p zero p
+ | nplus_succ_2: \forall q, r. NPlus p q r \to NPlus p (succ q) (succ r).
+
+(*CSC: the URI must disappear: there is a bug now *)
+interpretation "natural plus predicate" 'rel_plus x y z =
+ (cic:/matita/RELATIONAL/NPlus/defs/NPlus.ind#xpointer(1/1) x y z).
+
+notation "hvbox(a break + b break == c)"
+ non associative with precedence 95
+for @{ 'rel_plus $a $b $c}.