ex/Acc.thy

+(*  Title: 	HOL/ex/Acc.thy
+    ID:         $Id$
+    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
+    Copyright   1994  University of Cambridge
+
+Inductive definition of acc(r)
+
+See Ch. Paulin-Mohring, Inductive Definitions in the System Coq.
+Research Report 92-49, LIP, ENS Lyon.  Dec 1992.
+*)
+
+Acc = WF + 
+
+consts
+  pred :: "['b, ('a * 'b)set] => 'a set"	(*Set of predecessors*)
+  acc  :: "('a * 'a)set => 'a set"		(*Accessible part*)
+
+defs
+  pred_def     "pred(x,r) == {y. <y,x>:r}"
+
+inductive "acc(r)"
+  intrs
+    pred    "pred(a,r): Pow(acc(r)) ==> a: acc(r)"
+  monos     "[Pow_mono]"
+
+end