| 7998 |      1 | (*
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|  |      2 |     Factorisation within a factorial domain
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|  |      3 |     $Id$
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|  |      4 |     Author: Clemens Ballarin, started 25 November 1997
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|  |      5 | *)
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|  |      6 | 
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|  |      7 | open Factor;
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|  |      8 | 
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|  |      9 | goalw Ring.thy [assoc_def] "!! c::'a::factorial. \
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|  |     10 | \  [| irred c; irred a; irred b; c dvd (a*b) |] ==> c assoc a | c assoc b";
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|  |     11 | by (ftac factorial_prime 1);
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|  |     12 | by (rewrite_goals_tac [irred_def, prime_def]);
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|  |     13 | by (Blast_tac 1);
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|  |     14 | qed "irred_dvd_lemma";
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|  |     15 | 
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|  |     16 | goalw Ring.thy [assoc_def] "!! c::'a::factorial. \
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|  |     17 | \  [| irred c; a dvd <1> |] ==> \
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|  |     18 | \  (ALL b : set factors. irred b) & c dvd foldr op* factors a --> \
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|  |     19 | \  (EX d. c assoc d & d : set factors)";
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|  |     20 | by (induct_tac "factors" 1);
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|  |     21 | (* Base case: c dvd a contradicts irred c *)
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|  |     22 | by (full_simp_tac (simpset() addsimps [irred_def]) 1);
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|  |     23 | by (blast_tac (claset() addIs [dvd_trans_ring]) 1);
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|  |     24 | (* Induction step *)
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|  |     25 | by (ftac factorial_prime 1);
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|  |     26 | by (full_simp_tac (simpset() addsimps [irred_def, prime_def]) 1);
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|  |     27 | by (Blast_tac 1);
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|  |     28 | qed "irred_dvd_list_lemma";
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|  |     29 | 
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|  |     30 | goal Ring.thy "!! c::'a::factorial. \
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|  |     31 | \  [| irred c; ALL b : set factors. irred b; a dvd <1>; \
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|  |     32 | \    c dvd foldr op* factors a |] ==> \
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|  |     33 | \  EX d. c assoc d & d : set factors";
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|  |     34 | by (rtac (irred_dvd_list_lemma RS mp) 1);
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|  |     35 | by (Auto_tac);
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|  |     36 | qed "irred_dvd_list";
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|  |     37 | 
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|  |     38 | Goalw [Factorisation_def] "!! c::'a::factorial. \
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|  |     39 | \  [| irred c; Factorisation x factors u; c dvd x |] ==> \
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|  |     40 | \  EX d. c assoc d & d : set factors";
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|  |     41 | by (rtac (irred_dvd_list_lemma RS mp) 1);
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|  |     42 | by (Auto_tac);
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|  |     43 | qed "Factorisation_dvd";
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|  |     44 | 
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|  |     45 | Goalw [Factorisation_def] "!! c::'a::factorial. \
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|  |     46 | \  [| Factorisation x factors u; a : set factors |] ==> irred a";
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|  |     47 | by (Blast_tac 1);
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|  |     48 | qed "Factorisation_irred";
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|  |     49 | 
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