]> matita.cs.unibo.it Git - helm.git/blobdiff - matita/matita/contribs/lambdadelta/ground/arith/nat_pred_succ.ma
partial update in static_2
[helm.git] / matita / matita / contribs / lambdadelta / ground / arith / nat_pred_succ.ma
index b7f9918b08d0191cf52391c310700d278be31116..4a6e23b01846b0fd7b807b095b87add5b44d060f 100644 (file)
@@ -17,14 +17,33 @@ include "ground/arith/nat_pred.ma".
 
 (* PREDECESSOR FOR NON-NEGATIVE INTEGERS ************************************)
 
+(* Constructions with npsucc ************************************************)
+
+lemma pnpred_succ (n): n = pnpred (npsucc n).
+* //
+qed.
+
+lemma npsucc_pred (p): p = npsucc (pnpred p).
+* //
+qed.
+
+(* Constructions with nsucc and psucc ***************************************)
+
+lemma pnpred_psucc (p): pnpred (psucc p) = nsucc (pnpred p).
+* // qed.
+
 (* Constructions with nsucc *************************************************)
 
+lemma nsucc_pnpred (p):
+      ninj p = ↑(pnpred p).
+// qed.
+
 (*** pred_Sn pred_S *)
 lemma npred_succ (n): n = ↓↑n.
 * //
 qed.
 
-(* Inversion with nsucc *****************************************************)
+(* Inversions with nsucc ****************************************************)
 
 (*** nat_split *)
 lemma nat_split_zero_pos (n): ∨∨ 𝟎 = n | n = ↑↓n.