New version of the library. nth_prime, gcd, log.

[helm.git] / helm / matita / library / nat / minimization.ma

diff --git a/helm/matita/library/nat/minimization.ma b/helm/matita/library/nat/minimization.ma
index da76606b4233393971bd70580184a34740676700..5eaa02cc36922378f9dbca5755aa22651bbbcb7b 100644 (file)
--- a/helm/matita/library/nat/minimization.ma
+++ b/helm/matita/library/nat/minimization.ma
@@ -40,6 +40,39 @@ simplify.left.split.reflexivity.reflexivity.
 simplify.right.split.reflexivity.reflexivity.
 qed.
 
+theorem le_max_n : \forall f: nat \to bool. \forall n:nat.
+max n f \le n.
+intros.elim n.rewrite > max_O_f.apply le_n.
+simplify.elim (f (S n1)).simplify.apply le_n.
+simplify.apply le_S.assumption.
+qed.
+
+theorem le_to_le_max : \forall f: nat \to bool. \forall n,m:nat.
+n\le m  \to max n f \le max m f.
+intros.elim H.
+apply le_n.
+apply trans_le ? (max n1 f).apply H2.
+cut (f (S n1) = true \land max (S n1) f = (S n1)) \lor 
+(f (S n1) = false \land max (S n1) f = max n1 f).
+elim Hcut.elim H3.
+rewrite > H5.
+apply le_S.apply le_max_n.
+elim H3.rewrite > H5.apply le_n.
+apply max_S_max.
+qed.
+
+theorem f_m_to_le_max: \forall f: nat \to bool. \forall n,m:nat.
+m\le n \to f m = true \to m \le max n f.
+intros 3.elim n.apply le_n_O_elim m H.
+apply le_O_n.
+apply le_n_Sm_elim m n1 H1.
+intro.apply trans_le ? (max n1 f).
+apply H.apply le_S_S_to_le.assumption.assumption.
+apply le_to_le_max.apply le_n_Sn.
+intro.simplify.rewrite < H3. 
+rewrite > H2.simplify.apply le_n.
+qed.
+
 definition max_spec \def \lambda f:nat \to bool.\lambda n: nat.
 ex nat (\lambda i:nat. (le i n) \land (f i = true)) \to
 (f n) = true \land (\forall i. i < n \to (f i = false)).