author | paulson |
Mon, 27 Mar 2000 16:25:53 +0200 | |
changeset 8589 | a24f7e5ee7ef |
parent 8558 | 6c4860b1828d |
child 8703 | 816d8f6513be |
permissions | -rw-r--r-- |
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(* 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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*) |
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Addsimps (tiling.intrs @ domino.intrs); |
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AddIs tiling.intrs; |
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(** The union of two disjoint tilings is a tiling **) |
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Goal "t: tiling A ==> u: tiling A --> t <= -u --> t Un u : tiling A"; |
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by (etac tiling.induct 1); |
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by (simp_tac (simpset() addsimps [Un_assoc]) 2); |
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by Auto_tac; |
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qed_spec_mp "tiling_UnI"; |
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AddIs [tiling_UnI]; |
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(*** Chess boards ***) |
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Goalw [below_def] "(i: below k) = (i<k)"; |
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by Auto_tac; |
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qed "below_less_iff"; |
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AddIffs [below_less_iff]; |
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Goalw [below_def] "below 0 = {}"; |
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by Auto_tac; |
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qed "below_0"; |
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Addsimps [below_0]; |
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Goalw [below_def] |
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"below(Suc n) Times B = ({n} Times B) Un ((below n) Times B)"; |
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by Auto_tac; |
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qed "Sigma_Suc1"; |
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Goalw [below_def] |
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"A Times below(Suc n) = (A Times {n}) Un (A Times (below n))"; |
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by Auto_tac; |
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qed "Sigma_Suc2"; |
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Addsimps [Sigma_Suc1, Sigma_Suc2]; |
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Goal "({i} Times {n}) Un ({i} Times {m}) = {(i,m), (i,n)}"; |
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by Auto_tac; |
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qed "sing_Times_lemma"; |
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Goal "{i} Times below(n+n) : tiling domino"; |
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by (induct_tac "n" 1); |
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by (ALLGOALS (asm_simp_tac (simpset() addsimps [Un_assoc RS sym]))); |
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by (rtac tiling.Un 1); |
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by (ALLGOALS (asm_simp_tac (simpset() addsimps [sing_Times_lemma]))); |
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qed "dominoes_tile_row"; |
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AddSIs [dominoes_tile_row]; |
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Goal "(below m) Times below(n+n) : tiling domino"; |
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by (induct_tac "m" 1); |
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by Auto_tac; |
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qed "dominoes_tile_matrix"; |
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(*** "colored" and Dominoes ***) |
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Goalw [colored_def] |
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"colored b Int (insert (i,j) C) = \ |
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\ (if (i+j) mod 2 = b then insert (i,j) (colored b Int C) \ |
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\ else colored b Int C)"; |
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by Auto_tac; |
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qed "colored_insert"; |
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Addsimps [colored_insert]; |
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Goal "d:domino ==> finite d"; |
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by (etac domino.elim 1); |
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by Auto_tac; |
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qed "domino_finite"; |
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Addsimps [domino_finite]; |
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Goal "d:domino ==> (EX i j. colored 0 Int d = {(i,j)}) & \ |
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\ (EX k l. colored 1 Int d = {(k,l)})"; |
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by (etac domino.elim 1); |
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by (auto_tac (claset(), simpset() addsimps [mod_Suc])); |
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qed "domino_singletons"; |
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(*** Tilings of dominoes ***) |
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Goal "t:tiling domino ==> finite t"; |
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by (etac tiling.induct 1); |
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by Auto_tac; |
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qed "tiling_domino_finite"; |
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Addsimps [tiling_domino_finite, Int_Un_distrib, Diff_Int_distrib]; |
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Goal "t: tiling domino ==> card(colored 0 Int t) = card(colored 1 Int t)"; |
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by (etac tiling.induct 1); |
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by (dtac domino_singletons 2); |
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by Auto_tac; |
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(*this lemma tells us that both "inserts" are non-trivial*) |
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by (subgoal_tac "ALL p C. C Int a = {p} --> p ~: t" 1); |
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by (Asm_simp_tac 1); |
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by (blast_tac (claset() addEs [equalityE]) 1); |
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qed "tiling_domino_0_1"; |
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(*Final argument is surprisingly complex*) |
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Goal "[| t : tiling domino; \ |
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\ (i+j) mod 2 = 0; (k+l) mod 2 = 0; \ |
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\ {(i,j),(k,l)} <= t; l ~= j |] \ |
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\ ==> (t - {(i,j)} - {(k,l)}) ~: tiling domino"; |
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by (rtac notI 1); |
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by (subgoal_tac "card (colored 0 Int (t - {(i,j)} - {(k,l)})) < \ |
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\ card (colored 1 Int (t - {(i,j)} - {(k,l)}))" 1); |
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by (force_tac (claset(), HOL_ss addsimps [tiling_domino_0_1]) 1); |
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by (asm_simp_tac (simpset() addsimps [tiling_domino_0_1 RS sym]) 1); |
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by (rtac less_trans 1); |
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by (ALLGOALS (force_tac (claset() addSIs [card_Diff1_less], |
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simpset() addsimps [colored_def]))); |
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qed "gen_mutil_not_tiling"; |
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(*Apply the general theorem to the well-known case*) |
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Goal "[| t = below(Suc m + Suc m) Times below(Suc n + Suc n) |] \ |
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\ ==> t - {(0,0)} - {(Suc(m+m), Suc(n+n))} ~: tiling domino"; |
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by (rtac gen_mutil_not_tiling 1); |
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by (blast_tac (claset() addSIs [dominoes_tile_matrix]) 1); |
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by Auto_tac; |
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qed "mutil_not_tiling"; |
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