src/CCL/Lfp.thy
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(*  Title:      HOL/lfp.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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The Knaster-Tarski Theorem
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*)
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Lfp = Set +
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consts lfp :: "['a set=>'a set] => 'a set"
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rules
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 (*least fixed point*)
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 lfp_def "lfp(f) == Inter({u. f(u) <= u})"
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end