7998
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(*
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Degree of polynomials
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$Id$
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written by Clemens Ballarin, started 22 January 1997
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*)
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(* Relating degree and bound *)
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10230
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Goal "[| bound m f; f n ~= <0> |] ==> n <= m";
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by (force_tac (claset() addDs [inst "m" "n" boundD],
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simpset()) 1);
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7998
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qed "below_bound";
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goal UnivPoly.thy "bound (LEAST n. bound n (Rep_UP p)) (Rep_UP p)";
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by (rtac exE 1);
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by (rtac LeastI 2);
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by (assume_tac 2);
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by (res_inst_tac [("a", "Rep_UP p")] CollectD 1);
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by (rtac (rewrite_rule [UP_def] Rep_UP) 1);
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qed "Least_is_bound";
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Goalw [coeff_def, deg_def]
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"!! p. ALL m. n < m --> coeff m p = <0> ==> deg p <= n";
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by (rtac Least_le 1);
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by (Fast_tac 1);
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qed "deg_aboveI";
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Goalw [coeff_def, deg_def]
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"(n ~= 0 --> coeff n p ~= <0>) ==> n <= deg p";
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by (case_tac "n = 0" 1);
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(* Case n=0 *)
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by (Asm_simp_tac 1);
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(* Case n~=0 *)
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by (rotate_tac 1 1);
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by (Asm_full_simp_tac 1);
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by (rtac below_bound 1);
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by (assume_tac 2);
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by (rtac Least_is_bound 1);
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qed "deg_belowI";
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Goalw [coeff_def, deg_def]
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"deg p < m ==> coeff m p = <0>";
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7998
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by (rtac exE 1); (* create !! x. *)
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by (rtac boundD 2);
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by (assume_tac 3);
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by (rtac LeastI 2);
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by (assume_tac 2);
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by (res_inst_tac [("a", "Rep_UP p")] CollectD 1);
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by (rtac (rewrite_rule [UP_def] Rep_UP) 1);
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qed "deg_aboveD";
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Goalw [deg_def]
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"deg p = Suc y ==> ~ bound y (Rep_UP p)";
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7998
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by (rtac not_less_Least 1);
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by (Asm_simp_tac 1);
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val lemma1 = result();
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Goalw [deg_def, coeff_def]
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"deg p = Suc y ==> coeff (deg p) p ~= <0>";
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10230
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by (rtac ccontr 1);
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7998
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by (dtac notnotD 1);
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by (cut_inst_tac [("p", "p")] Least_is_bound 1);
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by (subgoal_tac "bound y (Rep_UP p)" 1);
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(* prove subgoal *)
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by (rtac boundI 2);
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by (case_tac "Suc y < m" 2);
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(* first case *)
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by (rtac boundD 2);
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by (assume_tac 2);
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by (Asm_simp_tac 2);
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(* second case *)
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by (dtac leI 2);
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by (dtac Suc_leI 2);
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by (dtac le_anti_sym 2);
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by (assume_tac 2);
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by (Asm_full_simp_tac 2);
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(* end prove subgoal *)
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by (fold_goals_tac [deg_def]);
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by (dtac lemma1 1);
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by (etac notE 1);
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by (assume_tac 1);
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val lemma2 = result();
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Goal "deg p ~= 0 ==> coeff (deg p) p ~= <0>";
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by (rtac lemma2 1);
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by (Full_simp_tac 1);
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by (dtac Suc_pred 1);
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by (rtac sym 1);
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by (Asm_simp_tac 1);
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qed "deg_lcoeff";
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Goal "p ~= <0> ==> coeff (deg p) p ~= <0>";
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by (etac contrapos_np 1);
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by (case_tac "deg p = 0" 1);
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by (blast_tac (claset() addSDs [deg_lcoeff]) 2);
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7998
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by (rtac up_eqI 1);
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by (case_tac "n=0" 1);
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by (rotate_tac ~2 1);
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by (Asm_full_simp_tac 1);
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by (asm_full_simp_tac (simpset() addsimps [deg_aboveD]) 1);
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qed "nonzero_lcoeff";
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Goal "(deg p <= n) = bound n (Rep_UP p)";
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by (rtac iffI 1);
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(* ==> *)
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by (rtac boundI 1);
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by (fold_goals_tac [coeff_def]);
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by (rtac deg_aboveD 1);
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by (fast_arith_tac 1);
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(* <== *)
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by (rtac deg_aboveI 1);
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by (rewtac coeff_def);
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by (Fast_tac 1);
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qed "deg_above_is_bound";
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(* Lemmas on the degree function *)
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Goalw [max_def]
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"!! p::'a::ring up. deg (p + q) <= max (deg p) (deg q)";
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by (case_tac "deg p <= deg q" 1);
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(* case deg p <= deg q *)
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by (rtac deg_aboveI 1);
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by (Asm_simp_tac 1);
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by (strip_tac 1);
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by (dtac le_less_trans 1);
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by (assume_tac 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD]) 1);
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(* case deg p > deg q *)
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by (rtac deg_aboveI 1);
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by (Asm_simp_tac 1);
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by (dtac not_leE 1);
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by (strip_tac 1);
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by (dtac less_trans 1);
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by (assume_tac 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD]) 1);
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qed "deg_add";
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Goal "!!p::('a::ring up). deg p < deg q ==> deg (p + q) = deg q";
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by (rtac order_antisym 1);
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by (rtac le_trans 1);
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by (rtac deg_add 1);
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by (Asm_simp_tac 1);
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by (rtac deg_belowI 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD, deg_lcoeff]) 1);
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qed "deg_add_equal";
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Goal "deg (monom m::'a::ring up) = m";
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by (rtac le_anti_sym 1);
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(* <= *)
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by (asm_simp_tac
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(simpset() addsimps [deg_aboveI, less_not_refl2 RS not_sym]) 1);
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(* >= *)
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by (asm_simp_tac
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(simpset() addsimps [deg_belowI, less_not_refl2 RS not_sym]) 1);
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qed "deg_monom";
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Goal "!! a::'a::ring. deg (const a) = 0";
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by (rtac le_anti_sym 1);
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by (rtac deg_aboveI 1);
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by (simp_tac (simpset() addsimps [less_not_refl2]) 1);
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by (rtac deg_belowI 1);
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by (simp_tac (simpset() addsimps [less_not_refl2]) 1);
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qed "deg_const";
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Goal "deg (<0>::'a::ringS up) = 0";
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by (rtac le_anti_sym 1);
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by (rtac deg_aboveI 1);
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by (Simp_tac 1);
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by (rtac deg_belowI 1);
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by (Simp_tac 1);
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qed "deg_zero";
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Goal "deg (<1>::'a::ring up) = 0";
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by (rtac le_anti_sym 1);
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by (rtac deg_aboveI 1);
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by (simp_tac (simpset() addsimps [less_not_refl2]) 1);
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by (rtac deg_belowI 1);
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by (Simp_tac 1);
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qed "deg_one";
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Goal "!!p::('a::ring) up. deg (-p) = deg p";
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by (rtac le_anti_sym 1);
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(* <= *)
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by (simp_tac (simpset() addsimps [deg_aboveI, deg_aboveD]) 1);
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by (simp_tac (simpset() addsimps [deg_belowI, deg_lcoeff, uminus_monom_neq]) 1);
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qed "deg_uminus";
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Addsimps [deg_monom, deg_const, deg_zero, deg_one, deg_uminus];
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Goal
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"!! a::'a::ring. deg (a *s p) <= (if a = <0> then 0 else deg p)";
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by (case_tac "a = <0>" 1);
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by (REPEAT (asm_simp_tac (simpset() addsimps [deg_aboveI, deg_aboveD]) 1));
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qed "deg_smult_ring";
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Goal
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"!! a::'a::domain. deg (a *s p) = (if a = <0> then 0 else deg p)";
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by (rtac le_anti_sym 1);
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by (rtac deg_smult_ring 1);
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by (case_tac "a = <0>" 1);
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by (REPEAT (asm_simp_tac (simpset() addsimps [deg_belowI, deg_lcoeff]) 1));
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qed "deg_smult";
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Goal
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"!! p::'a::ring up. [| deg p + deg q < k |] ==> \
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\ coeff i p * coeff (k - i) q = <0>";
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by (simp_tac (simpset() addsimps [coeff_def]) 1);
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by (rtac bound_mult_zero 1);
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by (assume_tac 3);
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by (simp_tac (simpset() addsimps [deg_above_is_bound RS sym]) 1);
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by (simp_tac (simpset() addsimps [deg_above_is_bound RS sym]) 1);
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qed "deg_above_mult_zero";
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Goal
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"!! p::'a::ring up. deg (p * q) <= deg p + deg q";
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by (rtac deg_aboveI 1);
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by (asm_simp_tac (simpset() addsimps [deg_above_mult_zero]) 1);
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qed "deg_mult_ring";
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goal Main.thy
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"!!k::nat. k < n ==> m < n + m - k";
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by (arith_tac 1);
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qed "less_add_diff";
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Goal "!!p. coeff n p ~= <0> ==> n <= deg p";
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(* More general than deg_belowI, and simplifies the next proof! *)
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by (rtac deg_belowI 1);
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by (Fast_tac 1);
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qed "deg_below2I";
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Goal
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"!! p::'a::domain up. \
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\ [| p ~= <0>; q ~= <0> |] ==> deg (p * q) = deg p + deg q";
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by (rtac le_anti_sym 1);
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by (rtac deg_mult_ring 1);
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(* deg p + deg q <= deg (p * q) *)
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by (rtac deg_below2I 1);
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by (Simp_tac 1);
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(*
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by (rtac conjI 1);
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by (rtac impI 1);
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*)
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by (res_inst_tac [("m", "deg p"), ("n", "deg p + deg q")] SUM_extend 1);
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by (rtac le_add1 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD]) 1);
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by (res_inst_tac [("m", "deg p"), ("n", "deg p")] SUM_extend_below 1);
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by (rtac le_refl 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD, less_add_diff]) 1);
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by (asm_simp_tac (simpset() addsimps [nonzero_lcoeff]) 1);
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(*
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by (rtac impI 1);
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by (res_inst_tac [("m", "deg p"), ("n", "deg p + deg q")] SUM_extend 1);
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by (rtac le_add1 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD, less_add_diff]) 1);
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by (res_inst_tac [("m", "deg p"), ("n", "deg p")] SUM_extend_below 1);
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by (rtac le_refl 1);
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by (asm_simp_tac (simpset() addsimps [deg_aboveD, less_add_diff]) 1);
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by (asm_simp_tac (simpset() addsimps [nonzero_lcoeff]) 1);
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*)
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qed "deg_mult";
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Addsimps [deg_smult, deg_mult];
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(* Representation theorems about polynomials *)
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goal PolyRing.thy
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"!! p::nat=>'a::ring up. coeff k (SUM n p) = SUM n (%i. coeff k (p i))";
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8707
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by (induct_tac "n" 1);
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by Auto_tac;
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7998
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qed "coeff_SUM";
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goal UnivPoly.thy
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"!! f::(nat=>'a::ring). \
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\ bound n f ==> SUM n (%i. if i = x then f i else <0>) = f x";
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by (simp_tac (simpset() addsimps [SUM_if_singleton]) 1);
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by (auto_tac
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8707
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(claset() addDs [not_leE],
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simpset()));
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7998
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qed "bound_SUM_if";
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Goal
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"!! p::'a::ring up. deg p <= n ==> SUM n (%i. coeff i p *s monom i) = p";
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by (rtac up_eqI 1);
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by (simp_tac (simpset() addsimps [coeff_SUM]) 1);
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by (rtac trans 1);
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by (res_inst_tac [("x", "na")] bound_SUM_if 2);
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by (full_simp_tac (simpset() addsimps [deg_above_is_bound, coeff_def]) 2);
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by (rtac SUM_cong 1);
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by (rtac refl 1);
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8006
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by (Asm_simp_tac 1);
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7998
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qed "up_repr";
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Goal
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"!! p::'a::ring up. [| deg p <= n; P p |] ==> \
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\ P (SUM n (%i. coeff i p *s monom i))";
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by (asm_simp_tac (simpset() addsimps [up_repr]) 1);
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qed "up_reprD";
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Goal
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"!! p::'a::ring up. [| deg p <= n; P (SUM n (%i. coeff i p *s monom i)) |] \
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\ ==> P p";
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by (asm_full_simp_tac (simpset() addsimps [up_repr]) 1);
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qed "up_repr2D";
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(*
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Goal
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"!! p::'a::ring up. [| deg p <= n; deg q <= m |] ==> \
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\ (SUM n (%i. coeff i p *s monom i) = SUM m (%i. coeff i q *s monom i)) \
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\ = (coeff k f = coeff k g)
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...
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qed "up_unique";
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*)
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(* Polynomials over integral domains are again integral domains *)
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Goal "!!p::'a::domain up. p * q = <0> ==> p = <0> | q = <0>";
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by (rtac classical 1);
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by (subgoal_tac "deg p = 0 & deg q = 0" 1);
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by (res_inst_tac [("p", "p"), ("n", "0")] up_repr2D 1);
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by (Asm_simp_tac 1);
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by (res_inst_tac [("p", "q"), ("n", "0")] up_repr2D 1);
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by (Asm_simp_tac 1);
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by (subgoal_tac "coeff 0 p = <0> | coeff 0 q = <0>" 1);
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8707
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by (force_tac (claset() addIs [up_eqI], simpset()) 1);
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7998
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by (rtac integral 1);
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by (subgoal_tac "coeff 0 (p * q) = <0>" 1);
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8707
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by (Asm_simp_tac 2);
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7998
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by (Full_simp_tac 1);
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by (dres_inst_tac [("f", "deg")] arg_cong 1);
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by (Asm_full_simp_tac 1);
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qed "up_integral";
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Goal "!! a::'a::domain. a *s p = <0> ==> a = <0> | p = <0>";
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by (full_simp_tac (simpset() addsimps [const_mult_is_smult RS sym]) 1);
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by (dtac up_integral 1);
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by Auto_tac;
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by (rtac (const_inj RS injD) 1);
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by (Simp_tac 1);
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qed "smult_integral";
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341 |
(* Divisibility and degree *)
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342 |
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343 |
Goalw [dvd_def]
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344 |
"!! p::'a::domain up. [| p dvd q; q ~= <0> |] ==> deg p <= deg q";
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345 |
by (etac exE 1);
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346 |
by (hyp_subst_tac 1);
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347 |
by (case_tac "p = <0>" 1);
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348 |
by (Asm_simp_tac 1);
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349 |
by (dtac r_nullD 1);
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350 |
by (asm_simp_tac (simpset() addsimps [le_add1]) 1);
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351 |
qed "dvd_imp_deg";
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