src/ZF/Fixedpt.thy
author paulson
Fri, 03 Jan 1997 15:01:55 +0100
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Implicit simpsets and clasets for FOL and ZF
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(*  Title:      ZF/fixedpt.thy
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1992  University of Cambridge
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Least and greatest fixed points
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*)
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Fixedpt = domrange +
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consts
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  bnd_mono    :: [i,i=>i]=>o
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  lfp, gfp    :: [i,i=>i]=>i
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defs
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  (*monotone operator from Pow(D) to itself*)
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  bnd_mono_def 
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      "bnd_mono(D,h) == h(D)<=D & (ALL W X. W<=X --> X<=D --> h(W) <= h(X))"
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  lfp_def     "lfp(D,h) == Inter({X: Pow(D). h(X) <= X})"
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  gfp_def     "gfp(D,h) == Union({X: Pow(D). X <= h(X)})"
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end