--- a/src/HOL/Algebra/Congruence.thy Sun Mar 21 15:57:40 2010 +0100
+++ b/src/HOL/Algebra/Congruence.thy Sun Mar 21 16:51:37 2010 +0100
@@ -21,23 +21,23 @@
definition
elem :: "_ \<Rightarrow> 'a \<Rightarrow> 'a set \<Rightarrow> bool" (infixl ".\<in>\<index>" 50)
- where "x .\<in>\<^bsub>S\<^esub> A \<equiv> (\<exists>y \<in> A. x .=\<^bsub>S\<^esub> y)"
+ where "x .\<in>\<^bsub>S\<^esub> A \<longleftrightarrow> (\<exists>y \<in> A. x .=\<^bsub>S\<^esub> y)"
definition
set_eq :: "_ \<Rightarrow> 'a set \<Rightarrow> 'a set \<Rightarrow> bool" (infixl "{.=}\<index>" 50)
- where "A {.=}\<^bsub>S\<^esub> B == ((\<forall>x \<in> A. x .\<in>\<^bsub>S\<^esub> B) \<and> (\<forall>x \<in> B. x .\<in>\<^bsub>S\<^esub> A))"
+ where "A {.=}\<^bsub>S\<^esub> B \<longleftrightarrow> ((\<forall>x \<in> A. x .\<in>\<^bsub>S\<^esub> B) \<and> (\<forall>x \<in> B. x .\<in>\<^bsub>S\<^esub> A))"
definition
eq_class_of :: "_ \<Rightarrow> 'a \<Rightarrow> 'a set" ("class'_of\<index> _")
- where "class_of\<^bsub>S\<^esub> x == {y \<in> carrier S. x .=\<^bsub>S\<^esub> y}"
+ where "class_of\<^bsub>S\<^esub> x = {y \<in> carrier S. x .=\<^bsub>S\<^esub> y}"
definition
eq_closure_of :: "_ \<Rightarrow> 'a set \<Rightarrow> 'a set" ("closure'_of\<index> _")
- where "closure_of\<^bsub>S\<^esub> A == {y \<in> carrier S. y .\<in>\<^bsub>S\<^esub> A}"
+ where "closure_of\<^bsub>S\<^esub> A = {y \<in> carrier S. y .\<in>\<^bsub>S\<^esub> A}"
definition
eq_is_closed :: "_ \<Rightarrow> 'a set \<Rightarrow> bool" ("is'_closed\<index> _")
- where "is_closed\<^bsub>S\<^esub> A == (A \<subseteq> carrier S \<and> closure_of\<^bsub>S\<^esub> A = A)"
+ where "is_closed\<^bsub>S\<^esub> A \<longleftrightarrow> A \<subseteq> carrier S \<and> closure_of\<^bsub>S\<^esub> A = A"
abbreviation
not_eq :: "_ \<Rightarrow> 'a \<Rightarrow> 'a \<Rightarrow> bool" (infixl ".\<noteq>\<index>" 50)