author | berghofe |
Fri, 16 Jul 1999 14:03:03 +0200 | |
changeset 7018 | ae18bb3075c3 |
parent 5931 | 325300576da7 |
child 8340 | c169cd21fe42 |
permissions | -rw-r--r-- |
3424 | 1 |
(* Title: HOL/Induct/Mutil |
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ID: $Id$ |
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
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Copyright 1996 University of Cambridge |
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The Mutilated Chess Board Problem, formalized inductively |
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Originator is Max Black, according to J A Robinson. |
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Popularized as the Mutilated Checkerboard Problem by J McCarthy |
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*) |
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Mutil = Finite + |
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consts |
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domino :: "(nat*nat)set set" |
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tiling :: "'a set set => 'a set set" |
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below :: "nat => nat set" |
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evnodd :: "[(nat*nat)set, nat] => (nat*nat)set" |
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inductive domino |
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intrs |
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horiz "{(i, j), (i, Suc j)} : domino" |
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vertl "{(i, j), (Suc i, j)} : domino" |
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inductive "tiling A" |
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intrs |
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empty "{} : tiling A" |
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Un "[| a: A; t: tiling A; a <= -t |] ==> a Un t : tiling A" |
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defs |
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below_def "below n == {i. i<n}" |
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evnodd_def "evnodd A b == A Int {(i,j). (i+j) mod 2 = b}" |
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end |