src/Sequents/LK.thy
author paulson
Mon, 06 Aug 2001 12:42:43 +0200
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removed an unsuitable default simprule
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(*  Title:      LK/LK
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    ID:         $Id$
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    Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
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    Copyright   1993  University of Cambridge
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Axiom to express monotonicity (a variant of the deduction theorem).  Makes the
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link between |- and ==>, needed for instance to prove imp_cong.
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Axiom left_cong allows the simplifier to use left-side formulas.  Ideally it
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should be derived from lower-level axioms.
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CANNOT be added to LK0.thy because modal logic is built upon it, and
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various modal rules would become inconsistent.
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*)
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LK = LK0 +
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rules
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  monotonic  "($H |- P ==> $H |- Q) ==> $H, P |- Q"
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  left_cong  "[| P == P';  |- P' ==> ($H |- $F) == ($H' |- $F') |] 
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              ==> (P, $H |- $F) == (P', $H' |- $F')"
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end