X-Git-Url: http://matita.cs.unibo.it/gitweb/?a=blobdiff_plain;f=helm%2Fmatita%2Flibrary%2Falgebra%2Fsemigroups.ma;h=5b461d1a4f43edba6acc9e4dd448f0eceb157243;hb=a7063fc0997a9d9eae6c329443e67ab92c4b6a0f;hp=93a139ca760e5113f6b87d00a8f09d5552861e48;hpb=ceb1ffa3c01551ba51c1afcd85d693726c7fd3d9;p=helm.git

diff --git a/helm/matita/library/algebra/semigroups.ma b/helm/matita/library/algebra/semigroups.ma
index 93a139ca7..5b461d1a4 100644
--- a/helm/matita/library/algebra/semigroups.ma
+++ b/helm/matita/library/algebra/semigroups.ma
@@ -16,38 +16,49 @@ set "baseuri" "cic:/matita/algebra/semigroups".
 
 include "higher_order_defs/functions.ma".
 
-definition isSemiGroup ≝
- λC:Type. λop: C → C → C.associative C op.
+(* Magmas *)
 
-record SemiGroup : Type ≝
- { carrier: Type;
-   op: carrier → carrier → carrier;
-   properties: isSemiGroup carrier op
+record Magma : Type ≝
+ { carrier:> Type;
+   op: carrier → carrier → carrier
  }.
- 
-coercion cic:/matita/algebra/semigroups/carrier.con.
 
-notation "hvbox(a break * \sub S b)" 
+notation < "M" for @{ 'carrier $M }.
+interpretation "carrier coercion" 'carrier S =
+ (cic:/matita/algebra/semigroups/carrier.con S).
+
+notation "hvbox(a break \middot b)" 
   left associative with precedence 55
-for @{ 'ptimes $S $a $b }.
+for @{ 'magma_op $a $b }.
 
-interpretation "Semigroup operation" 'times a b =
+interpretation "magma operation" 'magma_op a b =
  (cic:/matita/algebra/semigroups/op.con _ a b).
 
-interpretation "Semigroup operation" 'ptimes S a b =
- (cic:/matita/algebra/semigroups/op.con S a b).
+(* Semigroups *)
+
+record isSemiGroup (M:Magma) : Prop ≝
+ { associative: associative ? (op M) }.
 
+record SemiGroup : Type ≝
+ { magma:> Magma;
+   semigroup_properties:> isSemiGroup magma
+ }.
+ 
+notation < "S" for @{ 'magma $S }.
+interpretation "magma coercion" 'magma S =
+ (cic:/matita/algebra/semigroups/magma.con S).
+ 
 definition is_left_unit ≝
- λS:SemiGroup. λe:S. ∀x:S. e * x = x.
+ λS:SemiGroup. λe:S. ∀x:S. e·x = x.
  
 definition is_right_unit ≝
- λS:SemiGroup. λe:S. ∀x:S. x * e = x.
+ λS:SemiGroup. λe:S. ∀x:S. x·e = x.
 
 theorem is_left_unit_to_is_right_unit_to_eq:
- ∀S:SemiGroup. ∀e1,e2:S.
-  is_left_unit ? e1 → is_right_unit ? e2 → e1=e2.
+ ∀S:SemiGroup. ∀e,e':S.
+  is_left_unit ? e → is_right_unit ? e' → e=e'.
  intros;
- rewrite < (H e2);
- rewrite < (H1 e1) in \vdash (? ? % ?);
+ rewrite < (H e');
+ rewrite < (H1 e) in \vdash (? ? % ?);
  reflexivity.
-qed.
\ No newline at end of file
+qed.