X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fsoftware%2Fmatita%2Flibrary%2Fnat%2Frelevant_equations.ma;h=6e641708021d79d36c81b67283f889949e1fe43c;hb=fe40d64367a3105b09696557c256f5a78d4b7384;hp=af8f68d5b994ae829a868341cf3a1bffc37075e3;hpb=589ea43c8916e765e43f27b80a2596010527042c;p=helm.git

diff --git a/helm/software/matita/library/nat/relevant_equations.ma b/helm/software/matita/library/nat/relevant_equations.ma
index af8f68d5b..6e6417080 100644
--- a/helm/software/matita/library/nat/relevant_equations.ma
+++ b/helm/software/matita/library/nat/relevant_equations.ma
@@ -12,7 +12,7 @@
 (*                                                                        *)
 (**************************************************************************)
 
-set "baseuri" "cic:/matita/nat/relevant_equations.ma".
+set "baseuri" "cic:/matita/nat/relevant_equations".
 
 include "nat/times.ma".
 include "nat/minus.ma".
@@ -50,3 +50,13 @@ rewrite > distr_times_plus.
 rewrite > distr_times_plus.
 rewrite < assoc_plus.reflexivity.
 qed.
+
+theorem eq_pred_to_eq:
+ ∀n,m. O < n → O < m → pred n = pred m → n = m.
+intros;
+generalize in match (eq_f ? ? S ? ? H2);
+intro;
+rewrite < S_pred in H3;
+rewrite < S_pred in H3;
+assumption.
+qed.