--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ZF/sum.thy	Thu Sep 16 12:20:38 1993 +0200
@@ -0,0 +1,25 @@
+(*  Title: 	ZF/sum.thy
+    ID:         $Id$
+    Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
+    Copyright   1993  University of Cambridge
+
+Disjoint sums in Zermelo-Fraenkel Set Theory 
+"Part" primitive for simultaneous recursive type definitions
+*)
+
+Sum = Bool +
+consts
+    "+"    	:: "[i,i]=>i"      		(infixr 65)
+    Inl,Inr     :: "i=>i"
+    case        :: "[i=>i, i=>i, i]=>i"
+    Part        :: "[i,i=>i] => i"
+
+rules
+    sum_def     "A+B == {0}*A Un {1}*B"
+    Inl_def     "Inl(a) == <0,a>"
+    Inr_def     "Inr(b) == <1,b>"
+    case_def    "case(c,d) == split(%y z. cond(y, d(z), c(z)))"
+
+  (*operator for selecting out the various summands*)
+    Part_def	"Part(A,h) == {x: A. EX z. x = h(z)}"
+end