src/ZF/Sum.thy
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     1 (*  Title: 	ZF/sum.thy
       
     2     ID:         $Id$
       
     3     Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
       
     4     Copyright   1993  University of Cambridge
       
     5 
       
     6 Disjoint sums in Zermelo-Fraenkel Set Theory 
       
     7 "Part" primitive for simultaneous recursive type definitions
       
     8 *)
       
     9 
       
    10 Sum = Bool +
       
    11 consts
       
    12     "+"    	:: "[i,i]=>i"      		(infixr 65)
       
    13     Inl,Inr     :: "i=>i"
       
    14     case        :: "[i=>i, i=>i, i]=>i"
       
    15     Part        :: "[i,i=>i] => i"
       
    16 
       
    17 rules
       
    18     sum_def     "A+B == {0}*A Un {1}*B"
       
    19     Inl_def     "Inl(a) == <0,a>"
       
    20     Inr_def     "Inr(b) == <1,b>"
       
    21     case_def    "case(c,d) == split(%y z. cond(y, d(z), c(z)))"
       
    22 
       
    23   (*operator for selecting out the various summands*)
       
    24     Part_def	"Part(A,h) == {x: A. EX z. x = h(z)}"
       
    25 end