| 0 |      1 | (*  Title: 	ZF/univ.thy
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|  |      2 |     ID:         $Id$
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|  |      3 |     Author: 	Lawrence C Paulson, Cambridge University Computer Laboratory
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|  |      4 |     Copyright   1992  University of Cambridge
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|  |      5 | 
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|  |      6 | The cumulative hierarchy and a small universe for recursive types
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|  |      7 | 
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|  |      8 | Standard notation for Vset(i) is V(i), but users might want V for a variable
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|  |      9 | *)
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|  |     10 | 
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| 124 |     11 | Univ = Arith + Sum + "mono" +
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| 0 |     12 | consts
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|  |     13 |     Limit       ::      "i=>o"
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|  |     14 |     Vfrom       ::      "[i,i]=>i"
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|  |     15 |     Vset        ::      "i=>i"
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|  |     16 |     Vrec        ::      "[i, [i,i]=>i] =>i"
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|  |     17 |     univ        ::      "i=>i"
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|  |     18 | 
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|  |     19 | translations
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|  |     20 |     "Vset(x)"   == 	"Vfrom(0,x)"
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|  |     21 | 
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|  |     22 | rules
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| 28 |     23 |     Limit_def   "Limit(i) == Ord(i) & 0<i & (ALL y. y<i --> succ(y)<i)"
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| 0 |     24 | 
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|  |     25 |     Vfrom_def   "Vfrom(A,i) == transrec(i, %x f. A Un (UN y:x. Pow(f`y)))"
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|  |     26 | 
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|  |     27 |     Vrec_def
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|  |     28 |    	"Vrec(a,H) == transrec(rank(a), %x g. lam z: Vset(succ(x)).      \
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|  |     29 | \                             H(z, lam w:Vset(x). g`rank(w)`w)) ` a"
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|  |     30 | 
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|  |     31 |     univ_def    "univ(A) == Vfrom(A,nat)"
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|  |     32 | 
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|  |     33 | end
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