--- /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 *)
+(* *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/test/letrecand".
+
+include "nat/nat.ma".
+
+let rec pari n : Prop :=
+ match n with
+ [ O ⇒ True
+ | S n ⇒ dispari n
+ ]
+and dispari n : Prop :=
+ match n with
+ [ O => False
+ | S n => pari n
+ ].
+
+definition pari2 ≝
+let rec pari n : Prop :=
+ match n with
+ [ O ⇒ True
+ | S n ⇒ dispari n
+ ]
+and dispari n : Prop :=
+ match n with
+ [ O => False
+ | S n => pari n
+ ]
+in pari.
+
+definition dispari2 ≝
+let rec pari n : Prop :=
+ match n with
+ [ O ⇒ True
+ | S n ⇒ dispari n
+ ]
+and dispari n : Prop :=
+ match n with
+ [ O => False
+ | S n => pari n
+ ]
+in dispari.
+
+lemma test_pari: pari (S (S O)).
+simplify.
+constructor 1.
+qed.
+
+lemma test_pari2: pari2 (S (S O)).
+simplify.
+constructor 1.
+qed.
+
+lemma test_dispari: dispari (S O).
+simplify.
+constructor 1.
+qed.
+
+lemma test_dispari2: dispari2 (S O).
+simplify.
+constructor 1.
+qed.
\ No newline at end of file