src/HOL/Number_Theory/Euclidean_Algorithm.thy
author eberlm
Fri, 26 Feb 2016 14:58:07 +0100
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Tuned Euclidean Ring instance for polynomials
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(* Author: Manuel Eberl *)
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section \<open>Abstract euclidean algorithm\<close>
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theory Euclidean_Algorithm
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imports Main "~~/src/HOL/GCD" "~~/src/HOL/Library/Polynomial"
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begin
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text \<open>
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  A Euclidean semiring is a semiring upon which the Euclidean algorithm can be
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  implemented. It must provide:
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  \begin{itemize}
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  \item division with remainder
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  \item a size function such that @{term "size (a mod b) < size b"} 
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        for any @{term "b \<noteq> 0"}
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  \end{itemize}
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  The existence of these functions makes it possible to derive gcd and lcm functions 
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  for any Euclidean semiring.
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\<close> 
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class euclidean_semiring = semiring_div + normalization_semidom + 
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  fixes euclidean_size :: "'a \<Rightarrow> nat"
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  assumes size_0 [simp]: "euclidean_size 0 = 0"
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  assumes mod_size_less: 
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    "b \<noteq> 0 \<Longrightarrow> euclidean_size (a mod b) < euclidean_size b"
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  assumes size_mult_mono:
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    "b \<noteq> 0 \<Longrightarrow> euclidean_size a \<le> euclidean_size (a * b)"
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begin
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lemma euclidean_division:
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  fixes a :: 'a and b :: 'a
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  assumes "b \<noteq> 0"
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  obtains s and t where "a = s * b + t" 
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    and "euclidean_size t < euclidean_size b"
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proof -
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  from div_mod_equality [of a b 0] 
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     have "a = a div b * b + a mod b" by simp
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  with that and assms show ?thesis by (auto simp add: mod_size_less)
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qed
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lemma dvd_euclidean_size_eq_imp_dvd:
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  assumes "a \<noteq> 0" and b_dvd_a: "b dvd a" and size_eq: "euclidean_size a = euclidean_size b"
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  shows "a dvd b"
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proof (rule ccontr)
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  assume "\<not> a dvd b"
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  then have "b mod a \<noteq> 0" by (simp add: mod_eq_0_iff_dvd)
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  from b_dvd_a have b_dvd_mod: "b dvd b mod a" by (simp add: dvd_mod_iff)
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  from b_dvd_mod obtain c where "b mod a = b * c" unfolding dvd_def by blast
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    with \<open>b mod a \<noteq> 0\<close> have "c \<noteq> 0" by auto
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  with \<open>b mod a = b * c\<close> have "euclidean_size (b mod a) \<ge> euclidean_size b"
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      using size_mult_mono by force
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  moreover from \<open>\<not> a dvd b\<close> and \<open>a \<noteq> 0\<close>
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  have "euclidean_size (b mod a) < euclidean_size a"
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      using mod_size_less by blast
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  ultimately show False using size_eq by simp
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qed
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function gcd_eucl :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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where
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  "gcd_eucl a b = (if b = 0 then normalize a else gcd_eucl b (a mod b))"
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  by pat_completeness simp
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termination
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  by (relation "measure (euclidean_size \<circ> snd)") (simp_all add: mod_size_less)
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declare gcd_eucl.simps [simp del]
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lemma gcd_eucl_induct [case_names zero mod]:
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  assumes H1: "\<And>b. P b 0"
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  and H2: "\<And>a b. b \<noteq> 0 \<Longrightarrow> P b (a mod b) \<Longrightarrow> P a b"
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  shows "P a b"
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proof (induct a b rule: gcd_eucl.induct)
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  case ("1" a b)
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  show ?case
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  proof (cases "b = 0")
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    case True then show "P a b" by simp (rule H1)
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  next
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    case False
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    then have "P b (a mod b)"
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      by (rule "1.hyps")
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    with \<open>b \<noteq> 0\<close> show "P a b"
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      by (blast intro: H2)
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  qed
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qed
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definition lcm_eucl :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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where
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  "lcm_eucl a b = normalize (a * b) div gcd_eucl a b"
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definition Lcm_eucl :: "'a set \<Rightarrow> 'a" -- \<open>
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  Somewhat complicated definition of Lcm that has the advantage of working
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  for infinite sets as well\<close>
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where
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  "Lcm_eucl A = (if \<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) then
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     let l = SOME l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l =
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       (LEAST n. \<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n)
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       in normalize l 
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      else 0)"
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definition Gcd_eucl :: "'a set \<Rightarrow> 'a"
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where
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  "Gcd_eucl A = Lcm_eucl {d. \<forall>a\<in>A. d dvd a}"
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lemma gcd_eucl_0:
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  "gcd_eucl a 0 = normalize a"
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  by (simp add: gcd_eucl.simps [of a 0])
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lemma gcd_eucl_0_left:
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  "gcd_eucl 0 a = normalize a"
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  by (simp_all add: gcd_eucl_0 gcd_eucl.simps [of 0 a])
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lemma gcd_eucl_non_0:
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  "b \<noteq> 0 \<Longrightarrow> gcd_eucl a b = gcd_eucl b (a mod b)"
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  by (simp add: gcd_eucl.simps [of a b] gcd_eucl.simps [of b 0])
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lemma gcd_eucl_dvd1 [iff]: "gcd_eucl a b dvd a"
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  and gcd_eucl_dvd2 [iff]: "gcd_eucl a b dvd b"
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  by (induct a b rule: gcd_eucl_induct)
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     (simp_all add: gcd_eucl_0 gcd_eucl_non_0 dvd_mod_iff)
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lemma normalize_gcd_eucl [simp]:
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  "normalize (gcd_eucl a b) = gcd_eucl a b"
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  by (induct a b rule: gcd_eucl_induct) (simp_all add: gcd_eucl_0 gcd_eucl_non_0)
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lemma gcd_eucl_greatest:
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  fixes k a b :: 'a
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  shows "k dvd a \<Longrightarrow> k dvd b \<Longrightarrow> k dvd gcd_eucl a b"
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proof (induct a b rule: gcd_eucl_induct)
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  case (zero a) from zero(1) show ?case by (rule dvd_trans) (simp add: gcd_eucl_0)
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next
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  case (mod a b)
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  then show ?case
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    by (simp add: gcd_eucl_non_0 dvd_mod_iff)
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qed
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lemma eq_gcd_euclI:
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  fixes gcd :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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  assumes "\<And>a b. gcd a b dvd a" "\<And>a b. gcd a b dvd b" "\<And>a b. normalize (gcd a b) = gcd a b"
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          "\<And>a b k. k dvd a \<Longrightarrow> k dvd b \<Longrightarrow> k dvd gcd a b"
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  shows   "gcd = gcd_eucl"
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  by (intro ext, rule associated_eqI) (simp_all add: gcd_eucl_greatest assms)
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lemma gcd_eucl_zero [simp]:
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  "gcd_eucl a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
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  by (metis dvd_0_left dvd_refl gcd_eucl_dvd1 gcd_eucl_dvd2 gcd_eucl_greatest)+
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   146
lemma dvd_Lcm_eucl [simp]: "a \<in> A \<Longrightarrow> a dvd Lcm_eucl A"
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   147
  and Lcm_eucl_least: "(\<And>a. a \<in> A \<Longrightarrow> a dvd b) \<Longrightarrow> Lcm_eucl A dvd b"
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   148
  and unit_factor_Lcm_eucl [simp]: 
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   149
          "unit_factor (Lcm_eucl A) = (if Lcm_eucl A = 0 then 0 else 1)"
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   150
proof -
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   151
  have "(\<forall>a\<in>A. a dvd Lcm_eucl A) \<and> (\<forall>l'. (\<forall>a\<in>A. a dvd l') \<longrightarrow> Lcm_eucl A dvd l') \<and>
4aa35fd6c152 Tuned Euclidean rings
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   152
    unit_factor (Lcm_eucl A) = (if Lcm_eucl A = 0 then 0 else 1)" (is ?thesis)
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   153
  proof (cases "\<exists>l. l \<noteq>  0 \<and> (\<forall>a\<in>A. a dvd l)")
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   154
    case False
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   155
    hence "Lcm_eucl A = 0" by (auto simp: Lcm_eucl_def)
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   156
    with False show ?thesis by auto
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   157
  next
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   158
    case True
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   159
    then obtain l\<^sub>0 where l\<^sub>0_props: "l\<^sub>0 \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l\<^sub>0)" by blast
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   160
    def n \<equiv> "LEAST n. \<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
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   161
    def l \<equiv> "SOME l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
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   162
    have "\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
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   163
      apply (subst n_def)
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   164
      apply (rule LeastI[of _ "euclidean_size l\<^sub>0"])
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   165
      apply (rule exI[of _ l\<^sub>0])
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   166
      apply (simp add: l\<^sub>0_props)
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   167
      done
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   168
    from someI_ex[OF this] have "l \<noteq> 0" and "\<forall>a\<in>A. a dvd l" and "euclidean_size l = n" 
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   169
      unfolding l_def by simp_all
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   170
    {
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   171
      fix l' assume "\<forall>a\<in>A. a dvd l'"
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   172
      with \<open>\<forall>a\<in>A. a dvd l\<close> have "\<forall>a\<in>A. a dvd gcd_eucl l l'" by (auto intro: gcd_eucl_greatest)
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   173
      moreover from \<open>l \<noteq> 0\<close> have "gcd_eucl l l' \<noteq> 0" by simp
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   174
      ultimately have "\<exists>b. b \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd b) \<and> 
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   175
                          euclidean_size b = euclidean_size (gcd_eucl l l')"
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   176
        by (intro exI[of _ "gcd_eucl l l'"], auto)
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   177
      hence "euclidean_size (gcd_eucl l l') \<ge> n" by (subst n_def) (rule Least_le)
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   178
      moreover have "euclidean_size (gcd_eucl l l') \<le> n"
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   179
      proof -
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   180
        have "gcd_eucl l l' dvd l" by simp
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   181
        then obtain a where "l = gcd_eucl l l' * a" unfolding dvd_def by blast
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   182
        with \<open>l \<noteq> 0\<close> have "a \<noteq> 0" by auto
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   183
        hence "euclidean_size (gcd_eucl l l') \<le> euclidean_size (gcd_eucl l l' * a)"
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   184
          by (rule size_mult_mono)
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   185
        also have "gcd_eucl l l' * a = l" using \<open>l = gcd_eucl l l' * a\<close> ..
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   186
        also note \<open>euclidean_size l = n\<close>
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   187
        finally show "euclidean_size (gcd_eucl l l') \<le> n" .
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   188
      qed
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   189
      ultimately have *: "euclidean_size l = euclidean_size (gcd_eucl l l')" 
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   190
        by (intro le_antisym, simp_all add: \<open>euclidean_size l = n\<close>)
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   191
      from \<open>l \<noteq> 0\<close> have "l dvd gcd_eucl l l'"
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   192
        by (rule dvd_euclidean_size_eq_imp_dvd) (auto simp add: *)
4aa35fd6c152 Tuned Euclidean rings
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   193
      hence "l dvd l'" by (rule dvd_trans[OF _ gcd_eucl_dvd2])
4aa35fd6c152 Tuned Euclidean rings
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   194
    }
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diff changeset
   195
4aa35fd6c152 Tuned Euclidean rings
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   196
    with \<open>(\<forall>a\<in>A. a dvd l)\<close> and unit_factor_is_unit[OF \<open>l \<noteq> 0\<close>] and \<open>l \<noteq> 0\<close>
4aa35fd6c152 Tuned Euclidean rings
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   197
      have "(\<forall>a\<in>A. a dvd normalize l) \<and> 
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
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   198
        (\<forall>l'. (\<forall>a\<in>A. a dvd l') \<longrightarrow> normalize l dvd l') \<and>
4aa35fd6c152 Tuned Euclidean rings
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diff changeset
   199
        unit_factor (normalize l) = 
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   200
        (if normalize l = 0 then 0 else 1)"
4aa35fd6c152 Tuned Euclidean rings
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   201
      by (auto simp: unit_simps)
4aa35fd6c152 Tuned Euclidean rings
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   202
    also from True have "normalize l = Lcm_eucl A"
4aa35fd6c152 Tuned Euclidean rings
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   203
      by (simp add: Lcm_eucl_def Let_def n_def l_def)
4aa35fd6c152 Tuned Euclidean rings
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   204
    finally show ?thesis .
4aa35fd6c152 Tuned Euclidean rings
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   205
  qed
4aa35fd6c152 Tuned Euclidean rings
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   206
  note A = this
4aa35fd6c152 Tuned Euclidean rings
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   207
4aa35fd6c152 Tuned Euclidean rings
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   208
  {fix a assume "a \<in> A" then show "a dvd Lcm_eucl A" using A by blast}
4aa35fd6c152 Tuned Euclidean rings
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   209
  {fix b assume "\<And>a. a \<in> A \<Longrightarrow> a dvd b" then show "Lcm_eucl A dvd b" using A by blast}
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   210
  from A show "unit_factor (Lcm_eucl A) = (if Lcm_eucl A = 0 then 0 else 1)" by blast
4aa35fd6c152 Tuned Euclidean rings
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   211
qed
4aa35fd6c152 Tuned Euclidean rings
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   212
  
4aa35fd6c152 Tuned Euclidean rings
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   213
lemma normalize_Lcm_eucl [simp]:
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   214
  "normalize (Lcm_eucl A) = Lcm_eucl A"
4aa35fd6c152 Tuned Euclidean rings
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   215
proof (cases "Lcm_eucl A = 0")
4aa35fd6c152 Tuned Euclidean rings
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   216
  case True then show ?thesis by simp
4aa35fd6c152 Tuned Euclidean rings
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   217
next
4aa35fd6c152 Tuned Euclidean rings
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   218
  case False
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   219
  have "unit_factor (Lcm_eucl A) * normalize (Lcm_eucl A) = Lcm_eucl A"
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   220
    by (fact unit_factor_mult_normalize)
4aa35fd6c152 Tuned Euclidean rings
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   221
  with False show ?thesis by simp
4aa35fd6c152 Tuned Euclidean rings
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   222
qed
4aa35fd6c152 Tuned Euclidean rings
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diff changeset
   223
4aa35fd6c152 Tuned Euclidean rings
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   224
lemma eq_Lcm_euclI:
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   225
  fixes lcm :: "'a set \<Rightarrow> 'a"
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   226
  assumes "\<And>A a. a \<in> A \<Longrightarrow> a dvd lcm A" and "\<And>A c. (\<And>a. a \<in> A \<Longrightarrow> a dvd c) \<Longrightarrow> lcm A dvd c"
4aa35fd6c152 Tuned Euclidean rings
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parents: 62353
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   227
          "\<And>A. normalize (lcm A) = lcm A" shows "lcm = Lcm_eucl"
4aa35fd6c152 Tuned Euclidean rings
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parents: 62353
diff changeset
   228
  by (intro ext, rule associated_eqI) (auto simp: assms intro: Lcm_eucl_least)  
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   229
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
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diff changeset
   230
end
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   231
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   232
class euclidean_ring = euclidean_semiring + idom
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   233
begin
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   234
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   235
function euclid_ext :: "'a \<Rightarrow> 'a \<Rightarrow> 'a \<times> 'a \<times> 'a" where
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   236
  "euclid_ext a b = 
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   237
     (if b = 0 then 
60634
e3b6e516608b separate (semi)ring with normalization
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   238
        (1 div unit_factor a, 0, normalize a)
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   239
      else
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   240
        case euclid_ext b (a mod b) of
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   241
            (s, t, c) \<Rightarrow> (t, s - t * (a div b), c))"
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   242
  by pat_completeness simp
78ca5674c66a rings follow immediately their corresponding semirings
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   243
termination
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   244
  by (relation "measure (euclidean_size \<circ> snd)") (simp_all add: mod_size_less)
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   245
78ca5674c66a rings follow immediately their corresponding semirings
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   246
declare euclid_ext.simps [simp del]
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   247
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   248
lemma euclid_ext_0: 
60634
e3b6e516608b separate (semi)ring with normalization
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   249
  "euclid_ext a 0 = (1 div unit_factor a, 0, normalize a)"
60598
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   250
  by (simp add: euclid_ext.simps [of a 0])
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   251
78ca5674c66a rings follow immediately their corresponding semirings
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   252
lemma euclid_ext_left_0: 
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e3b6e516608b separate (semi)ring with normalization
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   253
  "euclid_ext 0 a = (0, 1 div unit_factor a, normalize a)"
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
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parents: 60599
diff changeset
   254
  by (simp add: euclid_ext_0 euclid_ext.simps [of 0 a])
60598
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diff changeset
   255
78ca5674c66a rings follow immediately their corresponding semirings
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   256
lemma euclid_ext_non_0: 
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   257
  "b \<noteq> 0 \<Longrightarrow> euclid_ext a b = (case euclid_ext b (a mod b) of
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   258
    (s, t, c) \<Rightarrow> (t, s - t * (a div b), c))"
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87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
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parents: 60599
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   259
  by (simp add: euclid_ext.simps [of a b] euclid_ext.simps [of b 0])
60598
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   260
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   261
lemma euclid_ext_code [code]:
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e3b6e516608b separate (semi)ring with normalization
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   262
  "euclid_ext a b = (if b = 0 then (1 div unit_factor a, 0, normalize a)
60598
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   263
    else let (s, t, c) = euclid_ext b (a mod b) in  (t, s - t * (a div b), c))"
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   264
  by (simp add: euclid_ext.simps [of a b] euclid_ext.simps [of b 0])
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   265
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   266
lemma euclid_ext_correct:
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   267
  "case euclid_ext a b of (s, t, c) \<Rightarrow> s * a + t * b = c"
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   268
proof (induct a b rule: gcd_eucl_induct)
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   269
  case (zero a) then show ?case
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   270
    by (simp add: euclid_ext_0 ac_simps)
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   271
next
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   272
  case (mod a b)
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   273
  obtain s t c where stc: "euclid_ext b (a mod b) = (s,t,c)"
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   274
    by (cases "euclid_ext b (a mod b)") blast
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   275
  with mod have "c = s * b + t * (a mod b)" by simp
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   276
  also have "... = t * ((a div b) * b + a mod b) + (s - t * (a div b)) * b"
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   277
    by (simp add: algebra_simps) 
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   278
  also have "(a div b) * b + a mod b = a" using mod_div_equality .
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   279
  finally show ?case
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   280
    by (subst euclid_ext.simps) (simp add: stc mod ac_simps)
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   281
qed
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   282
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   283
definition euclid_ext' :: "'a \<Rightarrow> 'a \<Rightarrow> 'a \<times> 'a"
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   284
where
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   285
  "euclid_ext' a b = (case euclid_ext a b of (s, t, _) \<Rightarrow> (s, t))"
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   286
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e3b6e516608b separate (semi)ring with normalization
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   287
lemma euclid_ext'_0: "euclid_ext' a 0 = (1 div unit_factor a, 0)" 
60598
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   288
  by (simp add: euclid_ext'_def euclid_ext_0)
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   289
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e3b6e516608b separate (semi)ring with normalization
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   290
lemma euclid_ext'_left_0: "euclid_ext' 0 a = (0, 1 div unit_factor a)" 
60598
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parents: 60582
diff changeset
   291
  by (simp add: euclid_ext'_def euclid_ext_left_0)
78ca5674c66a rings follow immediately their corresponding semirings
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parents: 60582
diff changeset
   292
  
78ca5674c66a rings follow immediately their corresponding semirings
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parents: 60582
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   293
lemma euclid_ext'_non_0: "b \<noteq> 0 \<Longrightarrow> euclid_ext' a b = (snd (euclid_ext' b (a mod b)),
78ca5674c66a rings follow immediately their corresponding semirings
haftmann
parents: 60582
diff changeset
   294
  fst (euclid_ext' b (a mod b)) - snd (euclid_ext' b (a mod b)) * (a div b))"
78ca5674c66a rings follow immediately their corresponding semirings
haftmann
parents: 60582
diff changeset
   295
  by (simp add: euclid_ext'_def euclid_ext_non_0 split_def)
78ca5674c66a rings follow immediately their corresponding semirings
haftmann
parents: 60582
diff changeset
   296
78ca5674c66a rings follow immediately their corresponding semirings
haftmann
parents: 60582
diff changeset
   297
end
78ca5674c66a rings follow immediately their corresponding semirings
haftmann
parents: 60582
diff changeset
   298
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
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   299
class euclidean_semiring_gcd = euclidean_semiring + gcd + Gcd +
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   300
  assumes gcd_gcd_eucl: "gcd = gcd_eucl" and lcm_lcm_eucl: "lcm = lcm_eucl"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   301
  assumes Gcd_Gcd_eucl: "Gcd = Gcd_eucl" and Lcm_Lcm_eucl: "Lcm = Lcm_eucl"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   302
begin
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   303
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   304
subclass semiring_gcd
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   305
  by standard (simp_all add: gcd_gcd_eucl gcd_eucl_greatest lcm_lcm_eucl lcm_eucl_def)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
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parents:
diff changeset
   306
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   307
subclass semiring_Gcd
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   308
  by standard (auto simp: Gcd_Gcd_eucl Lcm_Lcm_eucl Gcd_eucl_def intro: Lcm_eucl_least)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   309
  
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
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parents:
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   310
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   311
lemma gcd_non_0:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   312
  "b \<noteq> 0 \<Longrightarrow> gcd a b = gcd b (a mod b)"
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   313
  unfolding gcd_gcd_eucl by (fact gcd_eucl_non_0)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
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parents:
diff changeset
   314
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   315
lemmas gcd_0 = gcd_0_right
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   316
lemmas dvd_gcd_iff = gcd_greatest_iff
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
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parents:
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   317
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
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   318
lemmas gcd_greatest_iff = dvd_gcd_iff
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   319
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   320
lemma gcdI:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   321
  assumes "c dvd a" and "c dvd b" and greatest: "\<And>d. d dvd a \<Longrightarrow> d dvd b \<Longrightarrow> d dvd c"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   322
    and "normalize c = c"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   323
  shows "c = gcd a b"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   324
  by (rule associated_eqI) (auto simp: assms intro: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   325
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   326
lemma gcd_unique: "d dvd a \<and> d dvd b \<and> 
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   327
    normalize d = d \<and>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   328
    (\<forall>e. e dvd a \<and> e dvd b \<longrightarrow> e dvd d) \<longleftrightarrow> d = gcd a b"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   329
  by rule (auto intro: gcdI simp: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   330
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   331
lemma gcd_dvd_prod: "gcd a b dvd k * b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   332
  using mult_dvd_mono [of 1] by auto
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   333
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   334
lemma gcd_proj2_if_dvd: 
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   335
  "b dvd a \<Longrightarrow> gcd a b = normalize b"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   336
  by (cases "b = 0", simp_all add: dvd_eq_mod_eq_0 gcd_non_0)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   337
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   338
lemma gcd_proj1_if_dvd: 
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   339
  "a dvd b \<Longrightarrow> gcd a b = normalize a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   340
  by (subst gcd.commute, simp add: gcd_proj2_if_dvd)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   341
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   342
lemma gcd_proj1_iff: "gcd m n = normalize m \<longleftrightarrow> m dvd n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   343
proof
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   344
  assume A: "gcd m n = normalize m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   345
  show "m dvd n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   346
  proof (cases "m = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   347
    assume [simp]: "m \<noteq> 0"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   348
    from A have B: "m = gcd m n * unit_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   349
      by (simp add: unit_eq_div2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   350
    show ?thesis by (subst B, simp add: mult_unit_dvd_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   351
  qed (insert A, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   352
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   353
  assume "m dvd n"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   354
  then show "gcd m n = normalize m" by (rule gcd_proj1_if_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   355
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   356
  
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   357
lemma gcd_proj2_iff: "gcd m n = normalize n \<longleftrightarrow> n dvd m"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   358
  using gcd_proj1_iff [of n m] by (simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   359
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   360
lemma gcd_mod1 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   361
  "gcd (a mod b) b = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   362
  by (rule gcdI, metis dvd_mod_iff gcd_dvd1 gcd_dvd2, simp_all add: gcd_greatest dvd_mod_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   363
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   364
lemma gcd_mod2 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   365
  "gcd a (b mod a) = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   366
  by (rule gcdI, simp, metis dvd_mod_iff gcd_dvd1 gcd_dvd2, simp_all add: gcd_greatest dvd_mod_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   367
         
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   368
lemma gcd_mult_distrib': 
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   369
  "normalize c * gcd a b = gcd (c * a) (c * b)"
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   370
proof (cases "c = 0")
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   371
  case True then show ?thesis by simp_all
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   372
next
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   373
  case False then have [simp]: "is_unit (unit_factor c)" by simp
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   374
  show ?thesis
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   375
  proof (induct a b rule: gcd_eucl_induct)
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   376
    case (zero a) show ?case
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   377
    proof (cases "a = 0")
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   378
      case True then show ?thesis by simp
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   379
    next
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   380
      case False
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   381
      then show ?thesis by (simp add: normalize_mult)
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   382
    qed
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   383
    case (mod a b)
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   384
    then show ?case by (simp add: mult_mod_right gcd.commute)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   385
  qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   386
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   387
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   388
lemma gcd_mult_distrib:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   389
  "k * gcd a b = gcd (k * a) (k * b) * unit_factor k"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   390
proof-
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   391
  have "normalize k * gcd a b = gcd (k * a) (k * b)"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   392
    by (simp add: gcd_mult_distrib')
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   393
  then have "normalize k * gcd a b * unit_factor k = gcd (k * a) (k * b) * unit_factor k"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   394
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   395
  then have "normalize k * unit_factor k * gcd a b  = gcd (k * a) (k * b) * unit_factor k"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   396
    by (simp only: ac_simps)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   397
  then show ?thesis
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   398
    by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   399
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   400
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   401
lemma euclidean_size_gcd_le1 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   402
  assumes "a \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   403
  shows "euclidean_size (gcd a b) \<le> euclidean_size a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   404
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   405
   have "gcd a b dvd a" by (rule gcd_dvd1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   406
   then obtain c where A: "a = gcd a b * c" unfolding dvd_def by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   407
   with \<open>a \<noteq> 0\<close> show ?thesis by (subst (2) A, intro size_mult_mono) auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   408
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   409
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   410
lemma euclidean_size_gcd_le2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   411
  "b \<noteq> 0 \<Longrightarrow> euclidean_size (gcd a b) \<le> euclidean_size b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   412
  by (subst gcd.commute, rule euclidean_size_gcd_le1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   413
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   414
lemma euclidean_size_gcd_less1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   415
  assumes "a \<noteq> 0" and "\<not>a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   416
  shows "euclidean_size (gcd a b) < euclidean_size a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   417
proof (rule ccontr)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   418
  assume "\<not>euclidean_size (gcd a b) < euclidean_size a"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   419
  with \<open>a \<noteq> 0\<close> have A: "euclidean_size (gcd a b) = euclidean_size a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   420
    by (intro le_antisym, simp_all)
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   421
  have "a dvd gcd a b"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   422
    by (rule dvd_euclidean_size_eq_imp_dvd) (simp_all add: assms A)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   423
  hence "a dvd b" using dvd_gcdD2 by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   424
  with \<open>\<not>a dvd b\<close> show False by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   425
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   426
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   427
lemma euclidean_size_gcd_less2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   428
  assumes "b \<noteq> 0" and "\<not>b dvd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   429
  shows "euclidean_size (gcd a b) < euclidean_size b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   430
  using assms by (subst gcd.commute, rule euclidean_size_gcd_less1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   431
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   432
lemma gcd_mult_unit1: "is_unit a \<Longrightarrow> gcd (b * a) c = gcd b c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   433
  apply (rule gcdI)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   434
  apply simp_all
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   435
  apply (rule dvd_trans, rule gcd_dvd1, simp add: unit_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   436
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   437
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   438
lemma gcd_mult_unit2: "is_unit a \<Longrightarrow> gcd b (c * a) = gcd b c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   439
  by (subst gcd.commute, subst gcd_mult_unit1, assumption, rule gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   440
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   441
lemma gcd_div_unit1: "is_unit a \<Longrightarrow> gcd (b div a) c = gcd b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   442
  by (erule is_unitE [of _ b]) (simp add: gcd_mult_unit1)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   443
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   444
lemma gcd_div_unit2: "is_unit a \<Longrightarrow> gcd b (c div a) = gcd b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   445
  by (erule is_unitE [of _ c]) (simp add: gcd_mult_unit2)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   446
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   447
lemma normalize_gcd_left [simp]:
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   448
  "gcd (normalize a) b = gcd a b"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   449
proof (cases "a = 0")
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   450
  case True then show ?thesis
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   451
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   452
next
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   453
  case False then have "is_unit (unit_factor a)"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   454
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   455
  moreover have "normalize a = a div unit_factor a"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   456
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   457
  ultimately show ?thesis
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   458
    by (simp only: gcd_div_unit1)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   459
qed
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   460
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   461
lemma normalize_gcd_right [simp]:
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   462
  "gcd a (normalize b) = gcd a b"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   463
  using normalize_gcd_left [of b a] by (simp add: ac_simps)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   464
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   465
lemma gcd_idem: "gcd a a = normalize a"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   466
  by (cases "a = 0") (simp, rule sym, rule gcdI, simp_all)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   467
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   468
lemma gcd_right_idem: "gcd (gcd a b) b = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   469
  apply (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   470
  apply (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   471
  apply (rule gcd_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   472
  apply (rule gcd_greatest, erule (1) gcd_greatest, assumption)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   473
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   474
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   475
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   476
lemma gcd_left_idem: "gcd a (gcd a b) = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   477
  apply (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   478
  apply simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   479
  apply (rule dvd_trans, rule gcd_dvd2, rule gcd_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   480
  apply (rule gcd_greatest, assumption, erule gcd_greatest, assumption)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   481
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   482
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   483
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   484
lemma comp_fun_idem_gcd: "comp_fun_idem gcd"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   485
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   486
  fix a b show "gcd a \<circ> gcd b = gcd b \<circ> gcd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   487
    by (simp add: fun_eq_iff ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   488
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   489
  fix a show "gcd a \<circ> gcd a = gcd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   490
    by (simp add: fun_eq_iff gcd_left_idem)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   491
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   492
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   493
lemma gcd_dvd_antisym:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   494
  "gcd a b dvd gcd c d \<Longrightarrow> gcd c d dvd gcd a b \<Longrightarrow> gcd a b = gcd c d"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   495
proof (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   496
  assume A: "gcd a b dvd gcd c d" and B: "gcd c d dvd gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   497
  have "gcd c d dvd c" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   498
  with A show "gcd a b dvd c" by (rule dvd_trans)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   499
  have "gcd c d dvd d" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   500
  with A show "gcd a b dvd d" by (rule dvd_trans)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   501
  show "normalize (gcd a b) = gcd a b"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   502
    by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   503
  fix l assume "l dvd c" and "l dvd d"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   504
  hence "l dvd gcd c d" by (rule gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   505
  from this and B show "l dvd gcd a b" by (rule dvd_trans)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   506
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   507
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   508
lemma coprime_crossproduct:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   509
  assumes [simp]: "gcd a d = 1" "gcd b c = 1"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   510
  shows "normalize (a * c) = normalize (b * d) \<longleftrightarrow> normalize a  = normalize b \<and> normalize c = normalize d"
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   511
    (is "?lhs \<longleftrightarrow> ?rhs")
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   512
proof
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   513
  assume ?rhs
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   514
  then have "a dvd b" "b dvd a" "c dvd d" "d dvd c" by (simp_all add: associated_iff_dvd)
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   515
  then have "a * c dvd b * d" "b * d dvd a * c" by (fast intro: mult_dvd_mono)+
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   516
  then show ?lhs by (simp add: associated_iff_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   517
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   518
  assume ?lhs
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   519
  then have dvd: "a * c dvd b * d" "b * d dvd a * c" by (simp_all add: associated_iff_dvd)
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   520
  then have "a dvd b * d" by (metis dvd_mult_left) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   521
  hence "a dvd b" by (simp add: coprime_dvd_mult_iff)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   522
  moreover from dvd have "b dvd a * c" by (metis dvd_mult_left) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   523
  hence "b dvd a" by (simp add: coprime_dvd_mult_iff)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   524
  moreover from dvd have "c dvd d * b" 
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   525
    by (auto dest: dvd_mult_right simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   526
  hence "c dvd d" by (simp add: coprime_dvd_mult_iff gcd.commute)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   527
  moreover from dvd have "d dvd c * a"
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   528
    by (auto dest: dvd_mult_right simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   529
  hence "d dvd c" by (simp add: coprime_dvd_mult_iff gcd.commute)
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   530
  ultimately show ?rhs by (simp add: associated_iff_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   531
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   532
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   533
lemma gcd_add1 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   534
  "gcd (m + n) n = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   535
  by (cases "n = 0", simp_all add: gcd_non_0)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   536
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   537
lemma gcd_add2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   538
  "gcd m (m + n) = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   539
  using gcd_add1 [of n m] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   540
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   541
lemma gcd_add_mult:
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   542
  "gcd m (k * m + n) = gcd m n"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   543
proof -
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   544
  have "gcd m ((k * m + n) mod m) = gcd m (k * m + n)"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   545
    by (fact gcd_mod2)
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   546
  then show ?thesis by simp 
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
   547
qed
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   548
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   549
lemma coprimeI: "(\<And>l. \<lbrakk>l dvd a; l dvd b\<rbrakk> \<Longrightarrow> l dvd 1) \<Longrightarrow> gcd a b = 1"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   550
  by (rule sym, rule gcdI, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   551
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   552
lemma coprime: "gcd a b = 1 \<longleftrightarrow> (\<forall>d. d dvd a \<and> d dvd b \<longleftrightarrow> is_unit d)"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   553
  by (auto intro: coprimeI gcd_greatest dvd_gcdD1 dvd_gcdD2)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   554
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   555
lemma div_gcd_coprime:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   556
  assumes nz: "a \<noteq> 0 \<or> b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   557
  defines [simp]: "d \<equiv> gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   558
  defines [simp]: "a' \<equiv> a div d" and [simp]: "b' \<equiv> b div d"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   559
  shows "gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   560
proof (rule coprimeI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   561
  fix l assume "l dvd a'" "l dvd b'"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   562
  then obtain s t where "a' = l * s" "b' = l * t" unfolding dvd_def by blast
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   563
  moreover have "a = a' * d" "b = b' * d" by simp_all
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   564
  ultimately have "a = (l * d) * s" "b = (l * d) * t"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   565
    by (simp_all only: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   566
  hence "l*d dvd a" and "l*d dvd b" by (simp_all only: dvd_triv_left)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   567
  hence "l*d dvd d" by (simp add: gcd_greatest)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   568
  then obtain u where "d = l * d * u" ..
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   569
  then have "d * (l * u) = d" by (simp add: ac_simps)
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   570
  moreover from nz have "d \<noteq> 0" by simp
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   571
  with div_mult_self1_is_id have "d * (l * u) div d = l * u" . 
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   572
  ultimately have "1 = l * u"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   573
    using \<open>d \<noteq> 0\<close> by simp
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   574
  then show "l dvd 1" ..
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   575
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   576
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   577
lemma coprime_lmult:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   578
  assumes dab: "gcd d (a * b) = 1" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   579
  shows "gcd d a = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   580
proof (rule coprimeI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   581
  fix l assume "l dvd d" and "l dvd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   582
  hence "l dvd a * b" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   583
  with \<open>l dvd d\<close> and dab show "l dvd 1" by (auto intro: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   584
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   585
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   586
lemma coprime_rmult:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   587
  assumes dab: "gcd d (a * b) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   588
  shows "gcd d b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   589
proof (rule coprimeI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   590
  fix l assume "l dvd d" and "l dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   591
  hence "l dvd a * b" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   592
  with \<open>l dvd d\<close> and dab show "l dvd 1" by (auto intro: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   593
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   594
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   595
lemma coprime_mul_eq: "gcd d (a * b) = 1 \<longleftrightarrow> gcd d a = 1 \<and> gcd d b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   596
  using coprime_rmult[of d a b] coprime_lmult[of d a b] coprime_mult[of d a b] by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   597
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   598
lemma gcd_coprime:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   599
  assumes c: "gcd a b \<noteq> 0" and a: "a = a' * gcd a b" and b: "b = b' * gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   600
  shows "gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   601
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   602
  from c have "a \<noteq> 0 \<or> b \<noteq> 0" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   603
  with div_gcd_coprime have "gcd (a div gcd a b) (b div gcd a b) = 1" .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   604
  also from assms have "a div gcd a b = a'" by (metis div_mult_self2_is_id)+
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   605
  also from assms have "b div gcd a b = b'" by (metis div_mult_self2_is_id)+
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   606
  finally show ?thesis .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   607
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   608
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   609
lemma coprime_power:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   610
  assumes "0 < n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   611
  shows "gcd a (b ^ n) = 1 \<longleftrightarrow> gcd a b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   612
using assms proof (induct n)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   613
  case (Suc n) then show ?case
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   614
    by (cases n) (simp_all add: coprime_mul_eq)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   615
qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   616
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   617
lemma gcd_coprime_exists:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   618
  assumes nz: "gcd a b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   619
  shows "\<exists>a' b'. a = a' * gcd a b \<and> b = b' * gcd a b \<and> gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   620
  apply (rule_tac x = "a div gcd a b" in exI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   621
  apply (rule_tac x = "b div gcd a b" in exI)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   622
  apply (insert nz, auto intro: div_gcd_coprime)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   623
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   624
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   625
lemma coprime_exp:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   626
  "gcd d a = 1 \<Longrightarrow> gcd d (a^n) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   627
  by (induct n, simp_all add: coprime_mult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   628
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   629
lemma gcd_exp:
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   630
  "gcd (a ^ n) (b ^ n) = gcd a b ^ n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   631
proof (cases "a = 0 \<and> b = 0")
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   632
  case True
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   633
  then show ?thesis by (cases n) simp_all
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   634
next
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   635
  case False
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   636
  then have "1 = gcd ((a div gcd a b) ^ n) ((b div gcd a b) ^ n)"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   637
    using coprime_exp2[OF div_gcd_coprime[of a b], of n n, symmetric] by simp
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   638
  then have "gcd a b ^ n = gcd a b ^ n * ..." by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   639
  also note gcd_mult_distrib
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   640
  also have "unit_factor (gcd a b ^ n) = 1"
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   641
    using False by (auto simp add: unit_factor_power unit_factor_gcd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   642
  also have "(gcd a b)^n * (a div gcd a b)^n = a^n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   643
    by (subst ac_simps, subst div_power, simp, rule dvd_div_mult_self, rule dvd_power_same, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   644
  also have "(gcd a b)^n * (b div gcd a b)^n = b^n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   645
    by (subst ac_simps, subst div_power, simp, rule dvd_div_mult_self, rule dvd_power_same, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   646
  finally show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   647
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   648
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   649
lemma coprime_common_divisor: 
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   650
  "gcd a b = 1 \<Longrightarrow> a dvd a \<Longrightarrow> a dvd b \<Longrightarrow> is_unit a"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   651
  apply (subgoal_tac "a dvd gcd a b")
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   652
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   653
  apply (erule (1) gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   654
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   655
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   656
lemma division_decomp: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   657
  assumes dc: "a dvd b * c"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   658
  shows "\<exists>b' c'. a = b' * c' \<and> b' dvd b \<and> c' dvd c"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   659
proof (cases "gcd a b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   660
  assume "gcd a b = 0"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   661
  hence "a = 0 \<and> b = 0" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   662
  hence "a = 0 * c \<and> 0 dvd b \<and> c dvd c" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   663
  then show ?thesis by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   664
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   665
  let ?d = "gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   666
  assume "?d \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   667
  from gcd_coprime_exists[OF this]
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   668
    obtain a' b' where ab': "a = a' * ?d" "b = b' * ?d" "gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   669
    by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   670
  from ab'(1) have "a' dvd a" unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   671
  with dc have "a' dvd b*c" using dvd_trans[of a' a "b*c"] by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   672
  from dc ab'(1,2) have "a'*?d dvd (b'*?d) * c" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   673
  hence "?d * a' dvd ?d * (b' * c)" by (simp add: mult_ac)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   674
  with \<open>?d \<noteq> 0\<close> have "a' dvd b' * c" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   675
  with coprime_dvd_mult[OF ab'(3)] 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   676
    have "a' dvd c" by (subst (asm) ac_simps, blast)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   677
  with ab'(1) have "a = ?d * a' \<and> ?d dvd b \<and> a' dvd c" by (simp add: mult_ac)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   678
  then show ?thesis by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   679
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   680
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   681
lemma pow_divs_pow:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   682
  assumes ab: "a ^ n dvd b ^ n" and n: "n \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   683
  shows "a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   684
proof (cases "gcd a b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   685
  assume "gcd a b = 0"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   686
  then show ?thesis by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   687
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   688
  let ?d = "gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   689
  assume "?d \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   690
  from n obtain m where m: "n = Suc m" by (cases n, simp_all)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   691
  from \<open>?d \<noteq> 0\<close> have zn: "?d ^ n \<noteq> 0" by (rule power_not_zero)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   692
  from gcd_coprime_exists[OF \<open>?d \<noteq> 0\<close>]
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   693
    obtain a' b' where ab': "a = a' * ?d" "b = b' * ?d" "gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   694
    by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   695
  from ab have "(a' * ?d) ^ n dvd (b' * ?d) ^ n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   696
    by (simp add: ab'(1,2)[symmetric])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   697
  hence "?d^n * a'^n dvd ?d^n * b'^n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   698
    by (simp only: power_mult_distrib ac_simps)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   699
  with zn have "a'^n dvd b'^n" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   700
  hence "a' dvd b'^n" using dvd_trans[of a' "a'^n" "b'^n"] by (simp add: m)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   701
  hence "a' dvd b'^m * b'" by (simp add: m ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   702
  with coprime_dvd_mult[OF coprime_exp[OF ab'(3), of m]]
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   703
    have "a' dvd b'" by (subst (asm) ac_simps, blast)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   704
  hence "a'*?d dvd b'*?d" by (rule mult_dvd_mono, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   705
  with ab'(1,2) show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   706
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   707
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   708
lemma pow_divs_eq [simp]:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   709
  "n \<noteq> 0 \<Longrightarrow> a ^ n dvd b ^ n \<longleftrightarrow> a dvd b"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   710
  by (auto intro: pow_divs_pow dvd_power_same)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   711
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   712
lemmas divs_mult = divides_mult
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   713
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   714
lemma coprime_plus_one [simp]: "gcd (n + 1) n = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   715
  by (subst add_commute, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   716
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   717
lemma setprod_coprime [rule_format]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   718
  "(\<forall>i\<in>A. gcd (f i) a = 1) \<longrightarrow> gcd (\<Prod>i\<in>A. f i) a = 1"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   719
  apply (cases "finite A")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   720
  apply (induct set: finite)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   721
  apply (auto simp add: gcd_mult_cancel)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   722
  done
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   723
  
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   724
lemma listprod_coprime:
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   725
  "(\<And>x. x \<in> set xs \<Longrightarrow> coprime x y) \<Longrightarrow> coprime (listprod xs) y" 
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   726
  by (induction xs) (simp_all add: gcd_mult_cancel)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   727
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   728
lemma coprime_divisors: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   729
  assumes "d dvd a" "e dvd b" "gcd a b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   730
  shows "gcd d e = 1" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   731
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   732
  from assms obtain k l where "a = d * k" "b = e * l"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   733
    unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   734
  with assms have "gcd (d * k) (e * l) = 1" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   735
  hence "gcd (d * k) e = 1" by (rule coprime_lmult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   736
  also have "gcd (d * k) e = gcd e (d * k)" by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   737
  finally have "gcd e d = 1" by (rule coprime_lmult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   738
  then show ?thesis by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   739
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   740
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   741
lemma invertible_coprime:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   742
  assumes "a * b mod m = 1"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   743
  shows "coprime a m"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   744
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   745
  from assms have "coprime m (a * b mod m)"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   746
    by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   747
  then have "coprime m (a * b)"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   748
    by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   749
  then have "coprime m a"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   750
    by (rule coprime_lmult)
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   751
  then show ?thesis
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   752
    by (simp add: ac_simps)
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   753
qed
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   754
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   755
lemma lcm_gcd_prod:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   756
  "lcm a b * gcd a b = normalize (a * b)"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   757
  by (simp add: lcm_gcd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   758
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   759
lemma lcm_zero:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   760
  "lcm a b = 0 \<longleftrightarrow> a = 0 \<or> b = 0"
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
   761
  by (fact lcm_eq_0_iff)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   762
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   763
lemmas lcm_0_iff = lcm_zero
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   764
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   765
lemma gcd_lcm: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   766
  assumes "lcm a b \<noteq> 0"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   767
  shows "gcd a b = normalize (a * b) div lcm a b"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   768
proof -
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   769
  have "lcm a b * gcd a b = normalize (a * b)"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   770
    by (fact lcm_gcd_prod)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   771
  with assms show ?thesis
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   772
    by (metis nonzero_mult_divide_cancel_left)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   773
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   774
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
   775
declare unit_factor_lcm [simp]
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   776
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   777
lemma lcmI:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   778
  assumes "a dvd c" and "b dvd c" and "\<And>d. a dvd d \<Longrightarrow> b dvd d \<Longrightarrow> c dvd d"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   779
    and "normalize c = c"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   780
  shows "c = lcm a b"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   781
  by (rule associated_eqI) (auto simp: assms intro: lcm_least)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   782
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   783
lemma gcd_dvd_lcm [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   784
  "gcd a b dvd lcm a b"
60690
a9e45c9588c3 tuned facts
haftmann
parents: 60688
diff changeset
   785
  using gcd_dvd2 by (rule dvd_lcmI2)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   786
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   787
lemmas lcm_0 = lcm_0_right
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   788
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   789
lemma lcm_unique:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   790
  "a dvd d \<and> b dvd d \<and> 
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   791
  normalize d = d \<and>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   792
  (\<forall>e. a dvd e \<and> b dvd e \<longrightarrow> d dvd e) \<longleftrightarrow> d = lcm a b"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   793
  by rule (auto intro: lcmI simp: lcm_least lcm_zero)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   794
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   795
lemma lcm_coprime:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   796
  "gcd a b = 1 \<Longrightarrow> lcm a b = normalize (a * b)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   797
  by (subst lcm_gcd) simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   798
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   799
lemma lcm_proj1_if_dvd: 
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   800
  "b dvd a \<Longrightarrow> lcm a b = normalize a"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   801
  by (cases "a = 0") (simp, rule sym, rule lcmI, simp_all)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   802
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   803
lemma lcm_proj2_if_dvd: 
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   804
  "a dvd b \<Longrightarrow> lcm a b = normalize b"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   805
  using lcm_proj1_if_dvd [of a b] by (simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   806
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   807
lemma lcm_proj1_iff:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   808
  "lcm m n = normalize m \<longleftrightarrow> n dvd m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   809
proof
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   810
  assume A: "lcm m n = normalize m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   811
  show "n dvd m"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   812
  proof (cases "m = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   813
    assume [simp]: "m \<noteq> 0"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   814
    from A have B: "m = lcm m n * unit_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   815
      by (simp add: unit_eq_div2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   816
    show ?thesis by (subst B, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   817
  qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   818
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   819
  assume "n dvd m"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   820
  then show "lcm m n = normalize m" by (rule lcm_proj1_if_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   821
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   822
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   823
lemma lcm_proj2_iff:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   824
  "lcm m n = normalize n \<longleftrightarrow> m dvd n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   825
  using lcm_proj1_iff [of n m] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   826
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   827
lemma euclidean_size_lcm_le1: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   828
  assumes "a \<noteq> 0" and "b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   829
  shows "euclidean_size a \<le> euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   830
proof -
60690
a9e45c9588c3 tuned facts
haftmann
parents: 60688
diff changeset
   831
  have "a dvd lcm a b" by (rule dvd_lcm1)
a9e45c9588c3 tuned facts
haftmann
parents: 60688
diff changeset
   832
  then obtain c where A: "lcm a b = a * c" ..
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   833
  with \<open>a \<noteq> 0\<close> and \<open>b \<noteq> 0\<close> have "c \<noteq> 0" by (auto simp: lcm_zero)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   834
  then show ?thesis by (subst A, intro size_mult_mono)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   835
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   836
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   837
lemma euclidean_size_lcm_le2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   838
  "a \<noteq> 0 \<Longrightarrow> b \<noteq> 0 \<Longrightarrow> euclidean_size b \<le> euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   839
  using euclidean_size_lcm_le1 [of b a] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   840
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   841
lemma euclidean_size_lcm_less1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   842
  assumes "b \<noteq> 0" and "\<not>b dvd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   843
  shows "euclidean_size a < euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   844
proof (rule ccontr)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   845
  from assms have "a \<noteq> 0" by auto
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   846
  assume "\<not>euclidean_size a < euclidean_size (lcm a b)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   847
  with \<open>a \<noteq> 0\<close> and \<open>b \<noteq> 0\<close> have "euclidean_size (lcm a b) = euclidean_size a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   848
    by (intro le_antisym, simp, intro euclidean_size_lcm_le1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   849
  with assms have "lcm a b dvd a" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   850
    by (rule_tac dvd_euclidean_size_eq_imp_dvd) (auto simp: lcm_zero)
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   851
  hence "b dvd a" by (rule lcm_dvdD2)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   852
  with \<open>\<not>b dvd a\<close> show False by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   853
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   854
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   855
lemma euclidean_size_lcm_less2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   856
  assumes "a \<noteq> 0" and "\<not>a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   857
  shows "euclidean_size b < euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   858
  using assms euclidean_size_lcm_less1 [of a b] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   859
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   860
lemma lcm_mult_unit1:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   861
  "is_unit a \<Longrightarrow> lcm (b * a) c = lcm b c"
60690
a9e45c9588c3 tuned facts
haftmann
parents: 60688
diff changeset
   862
  by (rule associated_eqI) (simp_all add: mult_unit_dvd_iff dvd_lcmI1)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   863
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   864
lemma lcm_mult_unit2:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   865
  "is_unit a \<Longrightarrow> lcm b (c * a) = lcm b c"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   866
  using lcm_mult_unit1 [of a c b] by (simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   867
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   868
lemma lcm_div_unit1:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   869
  "is_unit a \<Longrightarrow> lcm (b div a) c = lcm b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   870
  by (erule is_unitE [of _ b]) (simp add: lcm_mult_unit1) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   871
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   872
lemma lcm_div_unit2:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   873
  "is_unit a \<Longrightarrow> lcm b (c div a) = lcm b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   874
  by (erule is_unitE [of _ c]) (simp add: lcm_mult_unit2)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   875
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   876
lemma normalize_lcm_left [simp]:
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   877
  "lcm (normalize a) b = lcm a b"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   878
proof (cases "a = 0")
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   879
  case True then show ?thesis
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   880
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   881
next
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   882
  case False then have "is_unit (unit_factor a)"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   883
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   884
  moreover have "normalize a = a div unit_factor a"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   885
    by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   886
  ultimately show ?thesis
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   887
    by (simp only: lcm_div_unit1)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   888
qed
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   889
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   890
lemma normalize_lcm_right [simp]:
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   891
  "lcm a (normalize b) = lcm a b"
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   892
  using normalize_lcm_left [of b a] by (simp add: ac_simps)
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   893
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   894
lemma LcmI:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   895
  assumes "\<And>a. a \<in> A \<Longrightarrow> a dvd b" and "\<And>c. (\<And>a. a \<in> A \<Longrightarrow> a dvd c) \<Longrightarrow> b dvd c"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
   896
    and "normalize b = b" shows "b = Lcm A"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   897
  by (rule associated_eqI) (auto simp: assms dvd_Lcm intro: Lcm_least)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   898
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   899
lemma Lcm_subset:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   900
  "A \<subseteq> B \<Longrightarrow> Lcm A dvd Lcm B"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   901
  by (blast intro: Lcm_least dvd_Lcm)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   902
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   903
lemma Lcm_Un:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   904
  "Lcm (A \<union> B) = lcm (Lcm A) (Lcm B)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   905
  apply (rule lcmI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   906
  apply (blast intro: Lcm_subset)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   907
  apply (blast intro: Lcm_subset)
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   908
  apply (intro Lcm_least ballI, elim UnE)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   909
  apply (rule dvd_trans, erule dvd_Lcm, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   910
  apply (rule dvd_trans, erule dvd_Lcm, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   911
  apply simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   912
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   913
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   914
lemma Lcm_no_units:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   915
  "Lcm A = Lcm (A - {a. is_unit a})"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   916
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   917
  have "(A - {a. is_unit a}) \<union> {a\<in>A. is_unit a} = A" by blast
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   918
  hence "Lcm A = lcm (Lcm (A - {a. is_unit a})) (Lcm {a\<in>A. is_unit a})"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   919
    by (simp add: Lcm_Un [symmetric])
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   920
  also have "Lcm {a\<in>A. is_unit a} = 1" by (simp add: Lcm_1_iff)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   921
  finally show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   922
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   923
62353
7f927120b5a2 dropped various legacy fact bindings and tuned proofs
haftmann
parents: 62348
diff changeset
   924
lemma Lcm_0_iff':
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   925
  "Lcm A = 0 \<longleftrightarrow> \<not>(\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l))"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   926
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   927
  assume "Lcm A = 0"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   928
  show "\<not>(\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l))"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   929
  proof
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   930
    assume ex: "\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l)"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   931
    then obtain l\<^sub>0 where l\<^sub>0_props: "l\<^sub>0 \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l\<^sub>0)" by blast
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   932
    def n \<equiv> "LEAST n. \<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   933
    def l \<equiv> "SOME l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   934
    have "\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l) \<and> euclidean_size l = n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   935
      apply (subst n_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   936
      apply (rule LeastI[of _ "euclidean_size l\<^sub>0"])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   937
      apply (rule exI[of _ l\<^sub>0])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   938
      apply (simp add: l\<^sub>0_props)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   939
      done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   940
    from someI_ex[OF this] have "l \<noteq> 0" unfolding l_def by simp_all
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   941
    hence "normalize l \<noteq> 0" by simp
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   942
    also from ex have "normalize l = Lcm A"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   943
       by (simp only: Lcm_Lcm_eucl Lcm_eucl_def n_def l_def if_True Let_def)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   944
    finally show False using \<open>Lcm A = 0\<close> by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   945
  qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   946
qed (simp only: Lcm_Lcm_eucl Lcm_eucl_def if_False)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   947
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   948
lemma Lcm_no_multiple:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   949
  "(\<forall>m. m \<noteq> 0 \<longrightarrow> (\<exists>a\<in>A. \<not>a dvd m)) \<Longrightarrow> Lcm A = 0"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   950
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   951
  assume "\<forall>m. m \<noteq> 0 \<longrightarrow> (\<exists>a\<in>A. \<not>a dvd m)"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   952
  hence "\<not>(\<exists>l. l \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd l))" by blast
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   953
  then show "Lcm A = 0" by (simp only: Lcm_Lcm_eucl Lcm_eucl_def if_False)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   954
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   955
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   956
lemma Lcm_finite:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   957
  assumes "finite A"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   958
  shows "Lcm A = Finite_Set.fold lcm 1 A"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   959
  by (induct rule: finite.induct[OF \<open>finite A\<close>])
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   960
    (simp_all add: comp_fun_idem.fold_insert_idem[OF comp_fun_idem_lcm])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   961
60431
db9c67b760f1 dropped warnings by dropping ineffective code declarations
haftmann
parents: 60430
diff changeset
   962
lemma Lcm_set [code_unfold]:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   963
  "Lcm (set xs) = fold lcm xs 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   964
  using comp_fun_idem.fold_set_fold[OF comp_fun_idem_lcm] Lcm_finite by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   965
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   966
lemma Lcm_singleton [simp]:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   967
  "Lcm {a} = normalize a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   968
  by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   969
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   970
lemma Lcm_2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   971
  "Lcm {a,b} = lcm a b"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   972
  by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   973
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   974
lemma Lcm_coprime:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   975
  assumes "finite A" and "A \<noteq> {}" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   976
  assumes "\<And>a b. a \<in> A \<Longrightarrow> b \<in> A \<Longrightarrow> a \<noteq> b \<Longrightarrow> gcd a b = 1"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   977
  shows "Lcm A = normalize (\<Prod>A)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   978
using assms proof (induct rule: finite_ne_induct)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   979
  case (insert a A)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   980
  have "Lcm (insert a A) = lcm a (Lcm A)" by simp
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   981
  also from insert have "Lcm A = normalize (\<Prod>A)" by blast
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   982
  also have "lcm a \<dots> = lcm a (\<Prod>A)" by (cases "\<Prod>A = 0") (simp_all add: lcm_div_unit2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   983
  also from insert have "gcd a (\<Prod>A) = 1" by (subst gcd.commute, intro setprod_coprime) auto
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   984
  with insert have "lcm a (\<Prod>A) = normalize (\<Prod>(insert a A))"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   985
    by (simp add: lcm_coprime)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   986
  finally show ?case .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   987
qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   988
      
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   989
lemma Lcm_coprime':
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   990
  "card A \<noteq> 0 \<Longrightarrow> (\<And>a b. a \<in> A \<Longrightarrow> b \<in> A \<Longrightarrow> a \<noteq> b \<Longrightarrow> gcd a b = 1)
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   991
    \<Longrightarrow> Lcm A = normalize (\<Prod>A)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   992
  by (rule Lcm_coprime) (simp_all add: card_eq_0_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   993
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   994
lemma unit_factor_Gcd [simp]: "unit_factor (Gcd A) = (if Gcd A = 0 then 0 else 1)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   995
proof -
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
   996
  show "unit_factor (Gcd A) = (if Gcd A = 0 then 0 else 1)"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
   997
    by (simp add: Gcd_Lcm unit_factor_Lcm)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   998
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   999
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1000
lemma GcdI:
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
  1001
  assumes "\<And>a. a \<in> A \<Longrightarrow> b dvd a" and "\<And>c. (\<And>a. a \<in> A \<Longrightarrow> c dvd a) \<Longrightarrow> c dvd b"
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60687
diff changeset
  1002
    and "normalize b = b"
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
  1003
  shows "b = Gcd A"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1004
  by (rule associated_eqI) (auto simp: assms Gcd_dvd intro: Gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1005
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1006
lemma Gcd_1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1007
  "1 \<in> A \<Longrightarrow> Gcd A = 1"
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
  1008
  by (auto intro!: Gcd_eq_1_I)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1009
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1010
lemma Gcd_finite:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1011
  assumes "finite A"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1012
  shows "Gcd A = Finite_Set.fold gcd 0 A"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1013
  by (induct rule: finite.induct[OF \<open>finite A\<close>])
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1014
    (simp_all add: comp_fun_idem.fold_insert_idem[OF comp_fun_idem_gcd])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1015
60431
db9c67b760f1 dropped warnings by dropping ineffective code declarations
haftmann
parents: 60430
diff changeset
  1016
lemma Gcd_set [code_unfold]:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1017
  "Gcd (set xs) = fold gcd xs 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1018
  using comp_fun_idem.fold_set_fold[OF comp_fun_idem_gcd] Gcd_finite by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1019
60634
e3b6e516608b separate (semi)ring with normalization
haftmann
parents: 60600
diff changeset
  1020
lemma Gcd_singleton [simp]: "Gcd {a} = normalize a"
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
  1021
  by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1022
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1023
lemma Gcd_2 [simp]: "Gcd {a,b} = gcd a b"
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
  1024
  by simp
60686
ea5bc46c11e6 more algebraic properties for gcd/lcm
haftmann
parents: 60685
diff changeset
  1025
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1026
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1027
definition pairwise_coprime where
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1028
  "pairwise_coprime A = (\<forall>x y. x \<in> A \<and> y \<in> A \<and> x \<noteq> y \<longrightarrow> coprime x y)"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1029
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1030
lemma pairwise_coprimeI [intro?]:
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1031
  "(\<And>x y. x \<in> A \<Longrightarrow> y \<in> A \<Longrightarrow> x \<noteq> y \<Longrightarrow> coprime x y) \<Longrightarrow> pairwise_coprime A"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1032
  by (simp add: pairwise_coprime_def)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1033
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1034
lemma pairwise_coprimeD:
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1035
  "pairwise_coprime A \<Longrightarrow> x \<in> A \<Longrightarrow> y \<in> A \<Longrightarrow> x \<noteq> y \<Longrightarrow> coprime x y"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1036
  by (simp add: pairwise_coprime_def)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1037
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1038
lemma pairwise_coprime_subset: "pairwise_coprime A \<Longrightarrow> B \<subseteq> A \<Longrightarrow> pairwise_coprime B"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1039
  by (force simp: pairwise_coprime_def)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1040
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1041
end
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1042
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1043
text \<open>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1044
  A Euclidean ring is a Euclidean semiring with additive inverses. It provides a 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1045
  few more lemmas; in particular, Bezout's lemma holds for any Euclidean ring.
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1046
\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1047
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1048
class euclidean_ring_gcd = euclidean_semiring_gcd + idom
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1049
begin
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1050
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1051
subclass euclidean_ring ..
60439
b765e08f8bc0 proper subclass instances for existing gcd (semi)rings
haftmann
parents: 60438
diff changeset
  1052
subclass ring_gcd ..
b765e08f8bc0 proper subclass instances for existing gcd (semi)rings
haftmann
parents: 60438
diff changeset
  1053
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1054
lemma euclid_ext_gcd [simp]:
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1055
  "(case euclid_ext a b of (_, _ , t) \<Rightarrow> t) = gcd a b"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1056
  by (induct a b rule: gcd_eucl_induct)
60686
ea5bc46c11e6 more algebraic properties for gcd/lcm
haftmann
parents: 60685
diff changeset
  1057
    (simp_all add: euclid_ext_0 euclid_ext_non_0 ac_simps split: prod.split prod.split_asm)
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1058
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1059
lemma euclid_ext_gcd' [simp]:
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1060
  "euclid_ext a b = (r, s, t) \<Longrightarrow> t = gcd a b"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1061
  by (insert euclid_ext_gcd[of a b], drule (1) subst, simp)
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1062
  
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1063
lemma euclid_ext'_correct:
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1064
  "fst (euclid_ext' a b) * a + snd (euclid_ext' a b) * b = gcd a b"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1065
proof-
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1066
  obtain s t c where "euclid_ext a b = (s,t,c)"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1067
    by (cases "euclid_ext a b", blast)
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1068
  with euclid_ext_correct[of a b] euclid_ext_gcd[of a b]
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1069
    show ?thesis unfolding euclid_ext'_def by simp
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1070
qed
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1071
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1072
lemma bezout: "\<exists>s t. s * a + t * b = gcd a b"
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1073
  using euclid_ext'_correct by blast
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1074
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1075
lemma gcd_neg1 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1076
  "gcd (-a) b = gcd a b"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
  1077
  by (rule sym, rule gcdI, simp_all add: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1078
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1079
lemma gcd_neg2 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1080
  "gcd a (-b) = gcd a b"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
  1081
  by (rule sym, rule gcdI, simp_all add: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1082
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1083
lemma gcd_neg_numeral_1 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1084
  "gcd (- numeral n) a = gcd (numeral n) a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1085
  by (fact gcd_neg1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1086
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1087
lemma gcd_neg_numeral_2 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1088
  "gcd a (- numeral n) = gcd a (numeral n)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1089
  by (fact gcd_neg2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1090
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1091
lemma gcd_diff1: "gcd (m - n) n = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1092
  by (subst diff_conv_add_uminus, subst gcd_neg2[symmetric],  subst gcd_add1, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1093
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1094
lemma gcd_diff2: "gcd (n - m) n = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1095
  by (subst gcd_neg1[symmetric], simp only: minus_diff_eq gcd_diff1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1096
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1097
lemma coprime_minus_one [simp]: "gcd (n - 1) n = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1098
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1099
  have "gcd (n - 1) n = gcd n (n - 1)" by (fact gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1100
  also have "\<dots> = gcd ((n - 1) + 1) (n - 1)" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1101
  also have "\<dots> = 1" by (rule coprime_plus_one)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1102
  finally show ?thesis .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1103
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1104
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1105
lemma lcm_neg1 [simp]: "lcm (-a) b = lcm a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1106
  by (rule sym, rule lcmI, simp_all add: lcm_least lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1107
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1108
lemma lcm_neg2 [simp]: "lcm a (-b) = lcm a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1109
  by (rule sym, rule lcmI, simp_all add: lcm_least lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1110
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1111
lemma lcm_neg_numeral_1 [simp]: "lcm (- numeral n) a = lcm (numeral n) a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1112
  by (fact lcm_neg1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1113
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1114
lemma lcm_neg_numeral_2 [simp]: "lcm a (- numeral n) = lcm a (numeral n)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1115
  by (fact lcm_neg2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1116
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1117
end
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1118
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1119
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1120
subsection \<open>Typical instances\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1121
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1122
instantiation nat :: euclidean_semiring
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1123
begin
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1124
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1125
definition [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1126
  "euclidean_size_nat = (id :: nat \<Rightarrow> nat)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1127
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1128
instance proof
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
  1129
qed simp_all
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1130
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1131
end
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1132
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1133
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1134
instantiation int :: euclidean_ring
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1135
begin
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1136
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1137
definition [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1138
  "euclidean_size_int = (nat \<circ> abs :: int \<Rightarrow> nat)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1139
60580
7e741e22d7fc tuned proofs;
wenzelm
parents: 60526
diff changeset
  1140
instance
60686
ea5bc46c11e6 more algebraic properties for gcd/lcm
haftmann
parents: 60685
diff changeset
  1141
by standard (auto simp add: abs_mult nat_mult_distrib split: abs_split)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1142
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1143
end
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1144
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1145
60572
718b1ba06429 streamlined definitions and primitive lemma of euclidean algorithm, including code generation
haftmann
parents: 60571
diff changeset
  1146
instantiation poly :: (field) euclidean_ring
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1147
begin
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1148
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1149
definition euclidean_size_poly :: "'a poly \<Rightarrow> nat"
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1150
  where "euclidean_size p = (if p = 0 then 0 else 2 ^ degree p)"
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1151
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1152
lemma euclidean_size_poly_0 [simp]:
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1153
  "euclidean_size (0::'a poly) = 0"
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1154
  by (simp add: euclidean_size_poly_def)
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1155
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1156
lemma euclidean_size_poly_not_0 [simp]:
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1157
  "p \<noteq> 0 \<Longrightarrow> euclidean_size p = 2 ^ degree p"
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1158
  by (simp add: euclidean_size_poly_def)
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1159
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1160
instance
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1161
proof
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1162
  fix p q :: "'a poly"
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1163
  assume "q \<noteq> 0"
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1164
  then have "p mod q = 0 \<or> degree (p mod q) < degree q"
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1165
    by (rule degree_mod_less [of q p])  
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1166
  with \<open>q \<noteq> 0\<close> show "euclidean_size (p mod q) < euclidean_size q"
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1167
    by (cases "p mod q = 0") simp_all
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1168
next
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1169
  fix p q :: "'a poly"
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1170
  assume "q \<noteq> 0"
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1171
  from \<open>q \<noteq> 0\<close> have "degree p \<le> degree (p * q)"
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1172
    by (rule degree_mult_right_le)
60600
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1173
  with \<open>q \<noteq> 0\<close> show "euclidean_size p \<le> euclidean_size (p * q)"
87fbfea0bd0a simplified termination criterion for euclidean algorithm (again)
haftmann
parents: 60599
diff changeset
  1174
    by (cases "p = 0") simp_all
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1175
qed simp
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1176
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1177
end
60571
c9fdf2080447 euclidean algorithm on polynomials
haftmann
parents: 60569
diff changeset
  1178
62422
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1179
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1180
instance nat :: euclidean_semiring_gcd
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1181
proof
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1182
  show [simp]: "gcd = (gcd_eucl :: nat \<Rightarrow> _)" "Lcm = (Lcm_eucl :: nat set \<Rightarrow> _)"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1183
    by (simp_all add: eq_gcd_euclI eq_Lcm_euclI)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1184
  show "lcm = (lcm_eucl :: nat \<Rightarrow> _)" "Gcd = (Gcd_eucl :: nat set \<Rightarrow> _)"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1185
    by (intro ext, simp add: lcm_eucl_def lcm_nat_def Gcd_nat_def Gcd_eucl_def)+
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1186
qed
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1187
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1188
instance int :: euclidean_ring_gcd
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1189
proof
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1190
  show [simp]: "gcd = (gcd_eucl :: int \<Rightarrow> _)" "Lcm = (Lcm_eucl :: int set \<Rightarrow> _)"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1191
    by (simp_all add: eq_gcd_euclI eq_Lcm_euclI)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1192
  show "lcm = (lcm_eucl :: int \<Rightarrow> _)" "Gcd = (Gcd_eucl :: int set \<Rightarrow> _)"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1193
    by (intro ext, simp add: lcm_eucl_def lcm_altdef_int 
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1194
          semiring_Gcd_class.Gcd_Lcm Gcd_eucl_def abs_mult)+
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1195
qed
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1196
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1197
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1198
instantiation poly :: (field) euclidean_ring_gcd
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1199
begin
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1200
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1201
definition gcd_poly :: "'a poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" where
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1202
  "gcd_poly = gcd_eucl"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1203
  
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1204
definition lcm_poly :: "'a poly \<Rightarrow> 'a poly \<Rightarrow> 'a poly" where
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1205
  "lcm_poly = lcm_eucl"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1206
  
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1207
definition Gcd_poly :: "'a poly set \<Rightarrow> 'a poly" where
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1208
  "Gcd_poly = Gcd_eucl"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1209
  
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1210
definition Lcm_poly :: "'a poly set \<Rightarrow> 'a poly" where
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1211
  "Lcm_poly = Lcm_eucl"
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1212
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1213
instance by standard (simp_all only: gcd_poly_def lcm_poly_def Gcd_poly_def Lcm_poly_def)
4aa35fd6c152 Tuned Euclidean rings
eberlm
parents: 62353
diff changeset
  1214
end
60687
33dbbcb6a8a3 eliminated some duplication
haftmann
parents: 60686
diff changeset
  1215
62425
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1216
lemma poly_gcd_monic:
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1217
  "lead_coeff (gcd x y) = (if x = 0 \<and> y = 0 then 0 else 1)"
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1218
  using unit_factor_gcd[of x y]
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1219
  by (simp add: unit_factor_poly_def monom_0 one_poly_def lead_coeff_def split: if_split_asm)
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1220
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1221
lemma poly_dvd_antisym:
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1222
  fixes p q :: "'a::idom poly"
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1223
  assumes coeff: "coeff p (degree p) = coeff q (degree q)"
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1224
  assumes dvd1: "p dvd q" and dvd2: "q dvd p" shows "p = q"
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1225
proof (cases "p = 0")
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1226
  case True with coeff show "p = q" by simp
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1227
next
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1228
  case False with coeff have "q \<noteq> 0" by auto
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1229
  have degree: "degree p = degree q"
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1230
    using \<open>p dvd q\<close> \<open>q dvd p\<close> \<open>p \<noteq> 0\<close> \<open>q \<noteq> 0\<close>
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1231
    by (intro order_antisym dvd_imp_degree_le)
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1232
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff changeset
  1233
  from \<open>p dvd q\<close> obtain a where a: "q = p * a" ..
d0936b500bf5 Tuned Euclidean Ring instance for polynomials
eberlm
parents: 62422
diff