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[helm.git] / helm / matita / library / Z / orders.ma

diff --git a/helm/matita/library/Z/orders.ma b/helm/matita/library/Z/orders.ma
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+(**************************************************************************)
+(*       ___                                                               *)
+(*      ||M||                                                             *)
+(*      ||A||       A project by Andrea Asperti                           *)
+(*      ||T||                                                             *)
+(*      ||I||       Developers:                                           *)
+(*      ||T||       A.Asperti, C.Sacerdoti Coen,                          *)
+(*      ||A||       E.Tassi, S.Zacchiroli                                 *)
+(*      \   /                                                             *)
+(*       \ /        This file is distributed under the terms of the       *)
+(*        v         GNU Lesser General Public License Version 2.1         *)
+(*                                                                        *)
+(**************************************************************************)
+
+set "baseuri" "cic:/matita/Z/orders".
+
+include "Z/z.ma".
+include "nat/orders.ma".
+
+definition Zle : Z \to Z \to Prop \def
+\lambda x,y:Z.
+  match x with
+  [ OZ \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow True
+    | (pos m) \Rightarrow True
+    | (neg m) \Rightarrow False ]
+  | (pos n) \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow False
+    | (pos m) \Rightarrow n \leq m
+    | (neg m) \Rightarrow False ]
+  | (neg n) \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow True
+    | (pos m) \Rightarrow True
+    | (neg m) \Rightarrow m \leq n ]].
+
+(*CSC: the URI must disappear: there is a bug now *)
+interpretation "integer 'less or equal to'" 'leq x y = (cic:/matita/Z/orders/Zle.con x y).
+(*CSC: the URI must disappear: there is a bug now *)
+interpretation "integer 'neither less nor equal to'" 'nleq x y =
+  (cic:/matita/logic/connectives/Not.con (cic:/matita/Z/orders/Zle.con x y)).
+
+definition Zlt : Z \to Z \to Prop \def
+\lambda x,y:Z.
+  match x with
+  [ OZ \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow False
+    | (pos m) \Rightarrow True
+    | (neg m) \Rightarrow False ]
+  | (pos n) \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow False
+    | (pos m) \Rightarrow n<m
+    | (neg m) \Rightarrow False ]
+  | (neg n) \Rightarrow 
+    match y with 
+    [ OZ \Rightarrow True
+    | (pos m) \Rightarrow True
+    | (neg m) \Rightarrow m<n ]].
+    
+(*CSC: the URI must disappear: there is a bug now *)
+interpretation "integer 'less than'" 'lt x y = (cic:/matita/Z/orders/Zlt.con x y).
+(*CSC: the URI must disappear: there is a bug now *)
+interpretation "integer 'not less than'" 'nless x y =
+  (cic:/matita/logic/connectives/Not.con (cic:/matita/Z/orders/Zlt.con x y)).
+
+theorem irreflexive_Zlt: irreflexive Z Zlt.
+change with (\forall x:Z. x < x \to False).
+intro.elim x.exact H.
+cut (neg n < neg n \to False).
+apply Hcut.apply H.simplify.unfold lt.apply not_le_Sn_n.
+cut (pos n < pos n \to False).
+apply Hcut.apply H.simplify.unfold lt.apply not_le_Sn_n.
+qed.
+
+theorem irrefl_Zlt: irreflexive Z Zlt
+\def irreflexive_Zlt.
+
+theorem Zlt_neg_neg_to_lt: 
+\forall n,m:nat. neg n < neg m \to m < n.
+intros.apply H.
+qed.
+
+theorem lt_to_Zlt_neg_neg: \forall n,m:nat.m < n \to neg n < neg m. 
+intros.
+simplify.apply H.
+qed.
+
+theorem Zlt_pos_pos_to_lt: 
+\forall n,m:nat. pos n < pos m \to n < m.
+intros.apply H.
+qed.
+
+theorem lt_to_Zlt_pos_pos: \forall n,m:nat.n < m \to pos n < pos m. 
+intros.
+simplify.apply H.
+qed.
+
+theorem Zlt_to_Zle: \forall x,y:Z. x < y \to Zsucc x \leq y.
+intros 2.
+elim x.
+(* goal: x=OZ *)
+  cut (OZ < y \to Zsucc OZ \leq y).
+    apply Hcut. assumption.
+    simplify.elim y. 
+      simplify.exact H1.
+      simplify.apply le_O_n.
+      simplify.exact H1.
+(* goal: x=pos *)      
+  exact H.
+(* goal: x=neg *)      
+  cut (neg n < y \to Zsucc (neg n) \leq y).
+    apply Hcut. assumption.
+    elim n.
+      cut (neg O < y \to Zsucc (neg O) \leq y).
+        apply Hcut. assumption.
+        simplify.elim y.
+          simplify.exact I.
+          simplify.exact I.
+          simplify.apply (not_le_Sn_O n1 H2).
+      cut (neg (S n1) < y \to (Zsucc (neg (S n1))) \leq y).
+        apply Hcut. assumption.simplify.
+        elim y.
+          simplify.exact I.
+          simplify.exact I.
+          simplify.apply (le_S_S_to_le n2 n1 H3).
+qed.