# HG changeset patch
# User haftmann
# Date 1313599887 -7200
# Node ID 567fb5f5c639e7d245b31d40557482870288d95a
# Parent  85e9dad3c187c3a0a26850cd0c35662904409abd# Parent  d58864221eef68c13622f9d77aabb8494353724c
merged

diff -r 85e9dad3c187 -r 567fb5f5c639 src/HOL/Quotient.thy
--- a/src/HOL/Quotient.thy	Wed Aug 17 10:03:58 2011 +0200
+++ b/src/HOL/Quotient.thy	Wed Aug 17 18:51:27 2011 +0200
@@ -643,10 +643,18 @@
     have "Collect (R (SOME x. x \<in> Rep a)) = (Rep a)" by (metis some_collect rep_prop)
     then show "Abs (Collect (R (SOME x. x \<in> Rep a))) = a" using rep_inverse by auto
     have "R r r \<Longrightarrow> R s s \<Longrightarrow> Abs (Collect (R r)) = Abs (Collect (R s)) \<longleftrightarrow> R r = R s"
-      by (metis Collect_def abs_inverse)
+    proof -
+      assume "R r r" and "R s s"
+      then have "Abs (Collect (R r)) = Abs (Collect (R s)) \<longleftrightarrow> Collect (R r) = Collect (R s)"
+        by (metis abs_inverse)
+      also have "Collect (R r) = Collect (R s) \<longleftrightarrow> (\<lambda>A x. x \<in> A) (Collect (R r)) = (\<lambda>A x. x \<in> A) (Collect (R s))"
+        by rule simp_all
+      finally show "Abs (Collect (R r)) = Abs (Collect (R s)) \<longleftrightarrow> R r = R s" by simp
+    qed
     then show "R r s \<longleftrightarrow> R r r \<and> R s s \<and> (Abs (Collect (R r)) = Abs (Collect (R s)))"
       using equivp[simplified part_equivp_def] by metis
     qed
+
 end
 
 subsection {* ML setup *}