X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=matita%2Fmatita%2Flib%2Fbasics%2Fbool.ma;h=fb0106f12501b1d1b951f64dd912d669a1618203;hb=1efc4c2c7be1e4aff0ccccabf905d45795b3865f;hp=7b26064856545b510fabb55073aa2393bdd00d5a;hpb=844794906f5a9f97406d72b5305ce13fb75acf94;p=helm.git

diff --git a/matita/matita/lib/basics/bool.ma b/matita/matita/lib/basics/bool.ma
index 7b2606485..fb0106f12 100644
--- a/matita/matita/lib/basics/bool.ma
+++ b/matita/matita/lib/basics/bool.ma
@@ -37,6 +37,14 @@ theorem notb_notb: ∀b:bool. notb (notb b) = b.
 theorem injective_notb: injective bool bool notb.
 #b1 #b2 #H // qed.
 
+theorem noteq_to_eqnot: ∀b1,b2. b1 ≠ b2 → b1 = notb b2.
+* * // #H @False_ind /2/
+qed.
+
+theorem eqnot_to_noteq: ∀b1,b2. b1 = notb b2 → b1 ≠ b2.
+* * normalize // #_ @(not_to_not … not_eq_true_false) //
+qed.
+
 definition andb : bool → bool → bool ≝
 λb1,b2:bool. match b1 with [ true ⇒ b2 | false ⇒ false ].
 
@@ -76,11 +84,16 @@ lemma orb_true_l: ∀b1,b2:bool.
   (b1 ∨ b2) = true → (b1 = true) ∨ (b2 = true).
 * normalize /2/ qed.
 
-definition if_then_else: ∀A:Type[0]. bool → A → A → A ≝ 
-λA.λb.λ P,Q:A. match b with [ true ⇒ P | false  ⇒ Q].
+definition xorb : bool → bool → bool ≝
+λb1,b2:bool.
+ match b1 with
+  [ true ⇒  match b2 with [ true ⇒ false | false ⇒ true ]
+  | false ⇒  match b2 with [ true ⇒ true | false ⇒ false ]].
 
-notation "'if' term 19 e 'then' term 19 t 'else' term 19 f" non associative with precedence 19 for @{ 'if_then_else $e $t $f }.
-interpretation "if_then_else" 'if_then_else e t f = (if_then_else ? e t f).
+notation > "'if' term 46 e 'then' term 46 t 'else' term 46 f" non associative with precedence 46
+ for @{ match $e in bool with [ true ⇒ $t | false ⇒ $f]  }.
+notation < "hvbox('if' \nbsp term 46 e \nbsp break 'then' \nbsp term 46 t \nbsp break 'else' \nbsp term 49 f \nbsp)" non associative with precedence 46
+ for @{ match $e with [ true ⇒ $t | false ⇒ $f]  }.
 
 theorem bool_to_decidable_eq: 
   ∀b1,b2:bool. decidable (b1=b2).
@@ -91,22 +104,3 @@ theorem true_or_false:
 #b (cases b) /2/ qed.
 
 
-(****** DeqSet: a set with a decidbale equality ******)
-
-record DeqSet : Type[1] ≝ { carr :> Type[0];
-   eqb: carr → carr → bool;
-   eqb_true: ∀x,y. (eqb x y = true) ↔ (x = y)
-}.
-
-notation "a == b" non associative with precedence 45 for @{ 'eqb $a $b }.
-interpretation "eqb" 'eqb a b = (eqb ? a b).
-
-
-(****** EnumSet: a DeqSet with an enumeration function  ******
-
-record EnumSet : Type[1] ≝ { carr :> DeqSet;
-   enum: carr 
-   eqb_true: ∀x,y. (eqb x y = true) ↔ (x = y)
-}.
-
-*)
\ No newline at end of file