author | paulson |
Tue, 02 May 2000 18:55:11 +0200 | |
changeset 8781 | d0c2bd57a9fb |
parent 8589 | a24f7e5ee7ef |
child 8950 | 3e858b72fac9 |
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 = Main + |
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consts tiling :: "'a set set => 'a set set" |
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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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consts domino :: "(nat*nat)set 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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constdefs |
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below :: "nat => nat set" |
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"below n == {i. i<n}" |
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colored :: "nat => (nat*nat)set" |
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"colored b == {(i,j). (i+j) mod #2 = b}" |
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end |