src/CCL/Lfp.thy

+(*  Title: 	HOL/lfp.thy
+    ID:         $Id$
+    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
+    Copyright   1992  University of Cambridge
+
+The Knaster-Tarski Theorem
+*)
+
+Lfp = Set +
+consts lfp :: "['a set=>'a set] => 'a set"
+rules
+ (*least fixed point*)
+ lfp_def "lfp(f) == Inter({u. f(u) <= u})"
+end