coercion cic:/matita/algebra/semigroups/carrier.con.
+notation "hvbox(a break * \sub S b)"
+ left associative with precedence 55
+for @{ 'ptimes $S $a $b }.
+
+interpretation "Semigroup operation" 'times 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).
+
definition is_left_unit ≝
- λS:SemiGroup. λe:S. ∀x:S. op S e x = x.
+ λS:SemiGroup. λe:S. ∀x:S. e * x = x.
definition is_right_unit ≝
- λS:SemiGroup. λe:S. ∀x:S. op 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.