X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fmatita%2Flibrary%2Fnat%2Fcompare.ma;h=2647315804661a23db188e36b4955c0b01c5152a;hb=4167cea65ca58897d1a3dbb81ff95de5074700cc;hp=60a9d4194c2dc5b3dbf47936260f9763d4bf577d;hpb=3eff4cc36820df9faddb3cb16390717851db499c;p=helm.git

diff --git a/helm/matita/library/nat/compare.ma b/helm/matita/library/nat/compare.ma
index 60a9d4194..264731580 100644
--- a/helm/matita/library/nat/compare.ma
+++ b/helm/matita/library/nat/compare.ma
@@ -1,5 +1,5 @@
 (**************************************************************************)
-(*       ___	                                                            *)
+(*       ___	                                                          *)
 (*      ||M||                                                             *)
 (*      ||A||       A project by Andrea Asperti                           *)
 (*      ||T||                                                             *)
@@ -14,9 +14,96 @@
 
 set "baseuri" "cic:/matita/nat/compare".
 
-include "nat/orders.ma".
 include "datatypes/bool.ma".
 include "datatypes/compare.ma".
+include "nat/orders.ma".
+
+let rec eqb n m \def 
+match n with 
+  [ O \Rightarrow 
+     match m with 
+     [ O \Rightarrow true
+	   | (S q) \Rightarrow false] 
+  | (S p) \Rightarrow
+	   match m with 
+     [ O \Rightarrow false
+	   | (S q) \Rightarrow eqb p q]].
+	   
+theorem eqb_to_Prop: \forall n,m:nat. 
+match (eqb n m) with
+[ true  \Rightarrow n = m 
+| false \Rightarrow n \neq m].
+intros.
+apply (nat_elim2
+(\lambda n,m:nat.match (eqb n m) with
+[ true  \Rightarrow n = m 
+| false \Rightarrow n \neq m])).
+intro.elim n1.
+simplify.reflexivity.
+simplify.apply not_eq_O_S.
+intro.
+simplify.unfold Not.
+intro. apply (not_eq_O_S n1).apply sym_eq.assumption.
+intros.simplify.
+generalize in match H.
+elim ((eqb n1 m1)).
+simplify.apply eq_f.apply H1.
+simplify.unfold Not.intro.apply H1.apply inj_S.assumption.
+qed.
+
+theorem eqb_elim : \forall n,m:nat.\forall P:bool \to Prop.
+(n=m \to (P true)) \to (n \neq m \to (P false)) \to (P (eqb n m)). 
+intros.
+cut 
+(match (eqb n m) with
+[ true  \Rightarrow n = m
+| false \Rightarrow n \neq m] \to (P (eqb n m))).
+apply Hcut.apply eqb_to_Prop.
+elim (eqb n m).
+apply ((H H2)).
+apply ((H1 H2)).
+qed.
+
+theorem eqb_n_n: \forall n. eqb n n = true.
+intro.elim n.simplify.reflexivity.
+simplify.assumption.
+qed.
+
+theorem eqb_true_to_eq: \forall n,m:nat.
+eqb n m = true \to n = m.
+intros.
+change with 
+match true with
+[ true  \Rightarrow n = m 
+| false \Rightarrow n \neq m].
+rewrite < H.
+apply eqb_to_Prop. 
+qed.
+
+theorem eqb_false_to_not_eq: \forall n,m:nat.
+eqb n m = false \to n \neq m.
+intros.
+change with 
+match false with
+[ true  \Rightarrow n = m 
+| false \Rightarrow n \neq m].
+rewrite < H.
+apply eqb_to_Prop. 
+qed.
+
+theorem eq_to_eqb_true: \forall n,m:nat.
+n = m \to eqb n m = true.
+intros.apply (eqb_elim n m).
+intros. reflexivity.
+intros.apply False_ind.apply (H1 H).
+qed.
+
+theorem not_eq_to_eqb_false: \forall n,m:nat.
+\lnot (n = m) \to eqb n m = false.
+intros.apply (eqb_elim n m).
+intros. apply False_ind.apply (H H1).
+intros.reflexivity.
+qed.
 
 let rec leb n m \def 
 match n with 
@@ -29,31 +116,31 @@ match n with
 theorem leb_to_Prop: \forall n,m:nat. 
 match (leb n m) with
 [ true  \Rightarrow n \leq m 
-| false \Rightarrow \lnot (n \leq m)].
+| false \Rightarrow n \nleq m].
 intros.
-apply nat_elim2
+apply (nat_elim2
 (\lambda n,m:nat.match (leb n m) with
 [ true  \Rightarrow n \leq m 
-| false \Rightarrow \lnot (n \leq m)]).
+| false \Rightarrow n \nleq m])).
 simplify.exact le_O_n.
 simplify.exact not_le_Sn_O.
-intros 2.simplify.elim (leb n1 m1).
+intros 2.simplify.elim ((leb n1 m1)).
 simplify.apply le_S_S.apply H.
-simplify.intros.apply H.apply le_S_S_to_le.assumption.
+simplify.unfold Not.intros.apply H.apply le_S_S_to_le.assumption.
 qed.
 
 theorem leb_elim: \forall n,m:nat. \forall P:bool \to Prop. 
-(n \leq m \to (P true)) \to (\not (n \leq m) \to (P false)) \to
+(n \leq m \to (P true)) \to (n \nleq m \to (P false)) \to
 P (leb n m).
 intros.
 cut 
-match (leb n m) with
+(match (leb n m) with
 [ true  \Rightarrow n \leq m
-| false \Rightarrow \lnot (n \leq m)] \to (P (leb n m)).
+| false \Rightarrow n \nleq m] \to (P (leb n m))).
 apply Hcut.apply leb_to_Prop.
-elim leb n m.
-apply (H H2).
-apply (H1 H2).
+elim (leb n m).
+apply ((H H2)).
+apply ((H1 H2)).
 qed.
 
 let rec nat_compare n m: compare \def
@@ -78,29 +165,44 @@ nat_compare n m = nat_compare (S n) (S m).
 intros.simplify.reflexivity.
 qed.
 
+theorem S_pred: \forall n:nat.lt O n \to eq nat n (S (pred n)).
+intro.elim n.apply False_ind.exact (not_le_Sn_O O H).
+apply eq_f.apply pred_Sn.
+qed.
+
+theorem nat_compare_pred_pred: 
+\forall n,m:nat.lt O n \to lt O m \to 
+eq compare (nat_compare n m) (nat_compare (pred n) (pred m)).
+intros.
+apply (lt_O_n_elim n H).
+apply (lt_O_n_elim m H1).
+intros.
+simplify.reflexivity.
+qed.
+
 theorem nat_compare_to_Prop: \forall n,m:nat. 
 match (nat_compare n m) with
   [ LT \Rightarrow n < m
   | EQ \Rightarrow n=m
   | GT \Rightarrow m < n ].
 intros.
-apply nat_elim2 (\lambda n,m.match (nat_compare n m) with
+apply (nat_elim2 (\lambda n,m.match (nat_compare n m) with
   [ LT \Rightarrow n < m
   | EQ \Rightarrow n=m
-  | GT \Rightarrow m < n ]).
+  | GT \Rightarrow m < n ])).
 intro.elim n1.simplify.reflexivity.
-simplify.apply le_S_S.apply le_O_n.
-intro.simplify.apply le_S_S. apply le_O_n.
-intros 2.simplify.elim (nat_compare n1 m1).
-simplify. apply le_S_S.apply H.
-simplify. apply le_S_S.apply H.
+simplify.unfold lt.apply le_S_S.apply le_O_n.
+intro.simplify.unfold lt.apply le_S_S. apply le_O_n.
+intros 2.simplify.elim ((nat_compare n1 m1)).
+simplify. unfold lt. apply le_S_S.apply H.
 simplify. apply eq_f. apply H.
+simplify. unfold lt.apply le_S_S.apply H.
 qed.
 
 theorem nat_compare_n_m_m_n: \forall n,m:nat. 
 nat_compare n m = compare_invert (nat_compare m n).
 intros. 
-apply nat_elim2 (\lambda n,m. nat_compare n m = compare_invert (nat_compare m n)).
+apply (nat_elim2 (\lambda n,m. nat_compare n m = compare_invert (nat_compare m n))).
 intros.elim n1.simplify.reflexivity.
 simplify.reflexivity.
 intro.elim n1.simplify.reflexivity.
@@ -112,14 +214,14 @@ theorem nat_compare_elim : \forall n,m:nat. \forall P:compare \to Prop.
 (n < m \to P LT) \to (n=m \to P EQ) \to (m < n \to P GT) \to 
 (P (nat_compare n m)).
 intros.
-cut match (nat_compare n m) with
+cut (match (nat_compare n m) with
 [ LT \Rightarrow n < m
 | EQ \Rightarrow n=m
 | GT \Rightarrow m < n] \to
-(P (nat_compare n m)).
+(P (nat_compare n m))).
 apply Hcut.apply nat_compare_to_Prop.
-elim (nat_compare n m).
-apply (H H3).
-apply (H2 H3).
-apply (H1 H3).
+elim ((nat_compare n m)).
+apply ((H H3)).
+apply ((H1 H3)).
+apply ((H2 H3)).
 qed.