- transcript: bugfix

[helm.git] / helm / software / matita / library / nat / div_and_mod.ma

diff --git a/helm/software/matita/library/nat/div_and_mod.ma b/helm/software/matita/library/nat/div_and_mod.ma
index 658b07b686eb5e6c23f02f3247c64f02f8f25381..fbf51276189b1524bb8418eb0f611606cd5f5f54 100644 (file)
--- a/helm/software/matita/library/nat/div_and_mod.ma
+++ b/helm/software/matita/library/nat/div_and_mod.ma
@@ -12,12 +12,9 @@
 (*                                                                        *)
 (**************************************************************************)
 
-set "baseuri" "cic:/matita/nat/div_and_mod".
-
 include "datatypes/constructors.ma".
 include "nat/minus.ma".
 
-
 let rec mod_aux p m n: nat \def
 match (leb m n) with
 [ true \Rightarrow m
@@ -32,8 +29,7 @@ match m with
 [O \Rightarrow n
 | (S p) \Rightarrow mod_aux n n p]. 
 
-interpretation "natural remainder" 'module x y =
-  (cic:/matita/nat/div_and_mod/mod.con x y).
+interpretation "natural remainder" 'module x y = (mod x y).
 
 let rec div_aux p m n : nat \def
 match (leb m n) with
@@ -49,8 +45,7 @@ match m with
 [O \Rightarrow S n
 | (S p) \Rightarrow div_aux n n p]. 
 
-interpretation "natural divide" 'divide x y =
-  (cic:/matita/nat/div_and_mod/div.con x y).
+interpretation "natural divide" 'divide x y = (div x y).
 
 theorem le_mod_aux_m_m: 
 \forall p,n,m. n \leq p \to (mod_aux p n m) \leq m.
@@ -223,6 +218,7 @@ apply (div_mod_spec_to_eq2 (q*m+r) m ((q*m+r)/ m) ((q*m+r) \mod m) q r)
   |apply div_mod_spec_intro[assumption|reflexivity]
   ]
 qed.
+
 (* some properties of div and mod *)
 theorem div_times: \forall n,m:nat. ((S n)*m) / (S n) = m.
 intros.
@@ -293,6 +289,50 @@ constructor 1.
 assumption.reflexivity.
 qed.
 
+theorem mod_SO: \forall n:nat. mod n (S O) = O.
+intro.
+apply sym_eq.
+apply le_n_O_to_eq.
+apply le_S_S_to_le.
+apply lt_mod_m_m.
+apply le_n.
+qed.
+
+theorem div_SO: \forall n:nat. div n (S O) = n.
+intro.
+rewrite > (div_mod ? (S O)) in \vdash (? ? ? %)
+  [rewrite > mod_SO.
+   rewrite < plus_n_O.
+   apply times_n_SO
+  |apply le_n
+  ]
+qed.
+
+theorem or_div_mod: \forall n,q. O < q \to
+((S (n \mod q)=q) \land S n = (S (div n q)) * q \lor
+((S (n \mod q)<q) \land S n= (div n q) * q + S (n\mod q))).
+intros.
+elim (le_to_or_lt_eq ? ? (lt_mod_m_m n q H))
+  [right.split
+    [assumption
+    |rewrite < plus_n_Sm.
+     apply eq_f.
+     apply div_mod.
+     assumption
+    ]
+  |left.split
+    [assumption
+    |simplify.
+     rewrite > sym_plus.
+     rewrite < H1 in ⊢ (? ? ? (? ? %)).
+     rewrite < plus_n_Sm.
+     apply eq_f.
+     apply div_mod.
+     assumption
+    ]
+  ]
+qed.
+
 (* injectivity *)
 theorem injective_times_r: \forall n:nat.injective nat nat (\lambda m:nat.(S n)*m).
 change with (\forall n,p,q:nat.(S n)*p = (S n)*q \to p=q).
@@ -338,6 +378,7 @@ qed.
 variant inj_times_l1:\forall n. O < n \to \forall p,q:nat.p*n = q*n \to p=q
 \def lt_O_to_injective_times_l.
 
+      
 (* n_divides computes the pair (div,mod) *)
 
 (* p is just an upper bound, acc is an accumulator *)