src/HOL/Number_Theory/Euclidean_Algorithm.thy
author haftmann
Thu, 25 Jun 2015 15:01:42 +0200
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permissions -rw-r--r--
euclidean algorithm on 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 Complex_Main "~~/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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  \item a normalization factor such that two associated numbers are equal iff 
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        they are the same when divd by their normalization factors.
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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 + 
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  fixes euclidean_size :: "'a \<Rightarrow> nat"
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  fixes normalization_factor :: "'a \<Rightarrow> 'a"
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  assumes mod_size_less: 
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    "b \<noteq> 0 \<Longrightarrow> \<not> b dvd a \<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 * b) \<ge> euclidean_size a"
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  assumes normalization_factor_is_unit [intro,simp]: 
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    "a \<noteq> 0 \<Longrightarrow> is_unit (normalization_factor a)"
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  assumes normalization_factor_mult: "normalization_factor (a * b) = 
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    normalization_factor a * normalization_factor b"
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  assumes normalization_factor_unit: "is_unit a \<Longrightarrow> normalization_factor a = a"
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  assumes normalization_factor_0 [simp]: "normalization_factor 0 = 0"
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begin
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lemma normalization_factor_dvd [simp]:
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  "a \<noteq> 0 \<Longrightarrow> normalization_factor a dvd b"
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  by (rule unit_imp_dvd, simp)
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lemma normalization_factor_1 [simp]:
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  "normalization_factor 1 = 1"
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  by (simp add: normalization_factor_unit)
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lemma normalization_factor_0_iff [simp]:
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  "normalization_factor a = 0 \<longleftrightarrow> a = 0"
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proof
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  assume "normalization_factor a = 0"
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  hence "\<not> is_unit (normalization_factor a)"
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    by simp
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  then show "a = 0" by auto
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qed simp
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lemma normalization_factor_pow:
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  "normalization_factor (a ^ n) = normalization_factor a ^ n"
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  by (induct n) (simp_all add: normalization_factor_mult power_Suc2)
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lemma normalization_correct [simp]:
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  "normalization_factor (a div normalization_factor a) = (if a = 0 then 0 else 1)"
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proof (cases "a = 0", simp)
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  assume "a \<noteq> 0"
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  let ?nf = "normalization_factor"
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  from normalization_factor_is_unit[OF \<open>a \<noteq> 0\<close>] have "?nf a \<noteq> 0"
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    by auto
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  have "?nf (a div ?nf a) * ?nf (?nf a) = ?nf (a div ?nf a * ?nf a)" 
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    by (simp add: normalization_factor_mult)
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  also have "a div ?nf a * ?nf a = a" using \<open>a \<noteq> 0\<close>
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    by simp
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  also have "?nf (?nf a) = ?nf a" using \<open>a \<noteq> 0\<close> 
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    normalization_factor_is_unit normalization_factor_unit by simp
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  finally have "normalization_factor (a div normalization_factor a) = 1"  
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    using \<open>?nf a \<noteq> 0\<close> by (metis div_mult_self2_is_id div_self)
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  with \<open>a \<noteq> 0\<close> show ?thesis by simp
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qed
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lemma normalization_0_iff [simp]:
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  "a div normalization_factor a = 0 \<longleftrightarrow> a = 0"
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  by (cases "a = 0", simp, subst unit_eq_div1, blast, simp)
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lemma mult_div_normalization [simp]:
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  "b * (1 div normalization_factor a) = b div normalization_factor a"
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  by (cases "a = 0") simp_all
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lemma associated_iff_normed_eq:
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  "associated a b \<longleftrightarrow> a div normalization_factor a = b div normalization_factor b"
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proof (cases "b = 0", simp, cases "a = 0", metis associated_0(1) normalization_0_iff, rule iffI)
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  let ?nf = normalization_factor
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  assume "a \<noteq> 0" "b \<noteq> 0" "a div ?nf a = b div ?nf b"
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  hence "a = b * (?nf a div ?nf b)"
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    apply (subst (asm) unit_eq_div1, blast, subst (asm) unit_div_commute, blast)
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    apply (subst div_mult_swap, simp, simp)
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    done
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  with \<open>a \<noteq> 0\<close> \<open>b \<noteq> 0\<close> have "\<exists>c. is_unit c \<and> a = c * b"
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    by (intro exI[of _ "?nf a div ?nf b"], force simp: mult_ac)
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  then obtain c where "is_unit c" and "a = c * b" by blast
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  then show "associated a b" by (rule is_unit_associatedI) 
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next
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  let ?nf = normalization_factor
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  assume "a \<noteq> 0" "b \<noteq> 0" "associated a b"
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  then obtain c where "is_unit c" and "a = c * b" by (blast elim: associated_is_unitE)
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  then show "a div ?nf a = b div ?nf b"
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    apply (simp only: \<open>a = c * b\<close> normalization_factor_mult normalization_factor_unit)
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    apply (rule div_mult_mult1, force)
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    done
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  qed
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lemma normed_associated_imp_eq:
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  "associated a b \<Longrightarrow> normalization_factor a \<in> {0, 1} \<Longrightarrow> normalization_factor b \<in> {0, 1} \<Longrightarrow> a = b"
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  by (simp add: associated_iff_normed_eq, elim disjE, simp_all)
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lemma normed_dvd [iff]:
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  "a div normalization_factor a dvd a"
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proof (cases "a = 0")
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  case True then show ?thesis by simp
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next
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  case False
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  then have "a = a div normalization_factor a * normalization_factor a"
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    by (auto intro: unit_div_mult_self)
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  then show ?thesis ..
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qed
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lemma dvd_normed [iff]:
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  "a dvd a div normalization_factor a"
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proof (cases "a = 0")
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  case True then show ?thesis by simp
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next
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  case False
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  then have "a div normalization_factor a = a * (1 div normalization_factor a)"
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    by (auto intro: unit_mult_div_div)
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  then show ?thesis ..
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qed
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lemma associated_normed:
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  "associated (a div normalization_factor a) a"
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  by (rule associatedI) simp_all
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lemma normalization_factor_dvd' [simp]:
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  "normalization_factor a dvd a"
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  by (cases "a = 0", simp_all)
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lemmas normalization_factor_dvd_iff [simp] =
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  unit_dvd_iff [OF normalization_factor_is_unit]
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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" and "\<not> b dvd a"
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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
fad653acf58f isabelle update_cartouches;
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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 a div normalization_factor a
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    else if b dvd a then b div normalization_factor b
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    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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    have "P b (a mod b)"
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    proof (cases "b dvd a")
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      case False with \<open>b \<noteq> 0\<close> show "P b (a mod b)"
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        by (rule "1.hyps")
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    next
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      case True then have "a mod b = 0"
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        by (simp add: mod_eq_0_iff_dvd)
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      then show "P b (a mod b)" by simp (rule H1)
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    qed
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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 = a * b div (gcd_eucl a b * normalization_factor (a * b))"
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  (* Somewhat complicated definition of Lcm that has the advantage of working
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     for infinite sets as well *)
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definition Lcm_eucl :: "'a set \<Rightarrow> 'a"
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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 l div normalization_factor 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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end
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class euclidean_semiring_gcd = euclidean_semiring + gcd + Gcd +
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  assumes gcd_gcd_eucl: "gcd = gcd_eucl" and lcm_lcm_eucl: "lcm = lcm_eucl"
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  assumes Gcd_Gcd_eucl: "Gcd = Gcd_eucl" and Lcm_Lcm_eucl: "Lcm = Lcm_eucl"
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begin
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lemma gcd_red:
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  "gcd a b = gcd b (a mod b)"
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  by (cases "b dvd a")
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    (auto simp add: gcd_gcd_eucl gcd_eucl.simps [of a b] gcd_eucl.simps [of 0 a] gcd_eucl.simps [of b 0])
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lemma gcd_non_0:
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  "b \<noteq> 0 \<Longrightarrow> gcd a b = gcd b (a mod b)"
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  by (rule gcd_red)
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lemma gcd_0_left:
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  "gcd 0 a = a div normalization_factor a"
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   by (simp only: gcd_gcd_eucl, subst gcd_eucl.simps, subst gcd_eucl.simps, simp add: Let_def)
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lemma gcd_0:
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  "gcd a 0 = a div normalization_factor a"
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  by (simp only: gcd_gcd_eucl, subst gcd_eucl.simps, simp add: Let_def)
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lemma gcd_dvd1 [iff]: "gcd a b dvd a"
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  and gcd_dvd2 [iff]: "gcd a b dvd b"
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  by (induct a b rule: gcd_eucl_induct)
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    (simp_all add: gcd_0 gcd_non_0 dvd_mod_iff)
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lemma dvd_gcd_D1: "k dvd gcd m n \<Longrightarrow> k dvd m"
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  by (rule dvd_trans, assumption, rule gcd_dvd1)
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lemma dvd_gcd_D2: "k dvd gcd m n \<Longrightarrow> k dvd n"
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  by (rule dvd_trans, assumption, rule gcd_dvd2)
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lemma gcd_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 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_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_non_0 dvd_mod_iff)
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qed
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lemma dvd_gcd_iff:
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  "k dvd gcd a b \<longleftrightarrow> k dvd a \<and> k dvd b"
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  by (blast intro!: gcd_greatest intro: dvd_trans)
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lemmas gcd_greatest_iff = dvd_gcd_iff
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lemma gcd_zero [simp]:
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  "gcd a b = 0 \<longleftrightarrow> a = 0 \<and> b = 0"
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  by (metis dvd_0_left dvd_refl gcd_dvd1 gcd_dvd2 gcd_greatest)+
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lemma normalization_factor_gcd [simp]:
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  "normalization_factor (gcd a b) = (if a = 0 \<and> b = 0 then 0 else 1)" (is "?f a b = ?g a b")
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  by (induct a b rule: gcd_eucl_induct)
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    (auto simp add: gcd_0 gcd_non_0)
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lemma gcdI:
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  "k dvd a \<Longrightarrow> k dvd b \<Longrightarrow> (\<And>l. l dvd a \<Longrightarrow> l dvd b \<Longrightarrow> l dvd k)
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    \<Longrightarrow> normalization_factor k = (if k = 0 then 0 else 1) \<Longrightarrow> k = gcd a b"
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  by (intro normed_associated_imp_eq) (auto simp: associated_def intro: gcd_greatest)
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sublocale gcd!: abel_semigroup gcd
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   294
proof
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   295
  fix a b c 
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   296
  show "gcd (gcd a b) c = gcd a (gcd b c)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   297
  proof (rule gcdI)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   298
    have "gcd (gcd a b) c dvd gcd a b" "gcd a b dvd a" by simp_all
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   299
    then show "gcd (gcd a b) c dvd a" by (rule dvd_trans)
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   300
    have "gcd (gcd a b) c dvd gcd a b" "gcd a b dvd b" by simp_all
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   301
    hence "gcd (gcd a b) c dvd b" by (rule dvd_trans)
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   302
    moreover have "gcd (gcd a b) c dvd c" by simp
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   303
    ultimately show "gcd (gcd a b) c dvd gcd b c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   304
      by (rule gcd_greatest)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   305
    show "normalization_factor (gcd (gcd a b) c) =  (if gcd (gcd a b) c = 0 then 0 else 1)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   306
      by auto
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   307
    fix l assume "l dvd a" and "l dvd gcd b c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   308
    with dvd_trans[OF _ gcd_dvd1] and dvd_trans[OF _ gcd_dvd2]
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   309
      have "l dvd b" and "l dvd c" by blast+
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   310
    with \<open>l dvd a\<close> show "l dvd gcd (gcd a b) c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   311
      by (intro gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   312
  qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   313
next
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   314
  fix a b
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   315
  show "gcd a b = gcd b a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   316
    by (rule gcdI) (simp_all add: gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   317
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   318
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   319
lemma gcd_unique: "d dvd a \<and> d dvd b \<and> 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   320
    normalization_factor d = (if d = 0 then 0 else 1) \<and>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   321
    (\<forall>e. e dvd a \<and> e dvd b \<longrightarrow> e dvd d) \<longleftrightarrow> d = gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   322
  by (rule, auto intro: gcdI simp: gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   323
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   324
lemma gcd_dvd_prod: "gcd a b dvd k * b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   325
  using mult_dvd_mono [of 1] by auto
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   326
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   327
lemma gcd_1_left [simp]: "gcd 1 a = 1"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   328
  by (rule sym, rule gcdI, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   329
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   330
lemma gcd_1 [simp]: "gcd a 1 = 1"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   331
  by (rule sym, rule gcdI, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   332
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   333
lemma gcd_proj2_if_dvd: 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   334
  "b dvd a \<Longrightarrow> gcd a b = b div normalization_factor b"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   335
  by (cases "b = 0", simp_all add: dvd_eq_mod_eq_0 gcd_non_0 gcd_0)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   336
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   337
lemma gcd_proj1_if_dvd: 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   338
  "a dvd b \<Longrightarrow> gcd a b = a div normalization_factor a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   339
  by (subst gcd.commute, simp add: gcd_proj2_if_dvd)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   340
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   341
lemma gcd_proj1_iff: "gcd m n = m div normalization_factor m \<longleftrightarrow> m dvd n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   342
proof
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   343
  assume A: "gcd m n = m div normalization_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   344
  show "m dvd n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   345
  proof (cases "m = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   346
    assume [simp]: "m \<noteq> 0"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   347
    from A have B: "m = gcd m n * normalization_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   348
      by (simp add: unit_eq_div2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   349
    show ?thesis by (subst B, simp add: mult_unit_dvd_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   350
  qed (insert A, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   351
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   352
  assume "m dvd n"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   353
  then show "gcd m n = m div normalization_factor m" by (rule gcd_proj1_if_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   354
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   355
  
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   356
lemma gcd_proj2_iff: "gcd m n = n div normalization_factor n \<longleftrightarrow> n dvd m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   357
  by (subst gcd.commute, simp add: gcd_proj1_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   358
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   359
lemma gcd_mod1 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   360
  "gcd (a mod b) b = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   361
  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
   362
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   363
lemma gcd_mod2 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   364
  "gcd a (b mod a) = gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   365
  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
   366
         
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   367
lemma gcd_mult_distrib': 
60569
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   368
  "c div normalization_factor c * gcd a b = gcd (c * a) (c * b)"
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   369
proof (cases "c = 0")
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   370
  case True then show ?thesis by (simp_all add: gcd_0)
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   371
next
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   372
  case False then have [simp]: "is_unit (normalization_factor c)" by simp
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   373
  show ?thesis
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   374
  proof (induct a b rule: gcd_eucl_induct)
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   375
    case (zero a) show ?case
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   376
    proof (cases "a = 0")
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   377
      case True then show ?thesis by (simp add: gcd_0)
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   378
    next
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   379
      case False then have "is_unit (normalization_factor a)" by simp
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   380
      then show ?thesis
f2f1f6860959 generalized to definition from literature, which covers also polynomials
haftmann
parents: 60526
diff changeset
   381
        by (simp add: gcd_0 unit_div_commute unit_div_mult_swap normalization_factor_mult is_unit_div_mult2_eq)
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:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   389
  "k * gcd a b = gcd (k*a) (k*b) * normalization_factor k"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   390
proof-
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   391
  let ?nf = "normalization_factor"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   392
  from gcd_mult_distrib' 
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   393
    have "gcd (k*a) (k*b) = k div ?nf k * gcd a b" ..
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   394
  also have "... = k * gcd a b div ?nf k"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   395
    by (metis dvd_div_mult dvd_eq_mod_eq_0 mod_0 normalization_factor_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   396
  finally show ?thesis
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   397
    by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   398
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   399
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   400
lemma euclidean_size_gcd_le1 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   401
  assumes "a \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   402
  shows "euclidean_size (gcd a b) \<le> euclidean_size a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   403
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   404
   have "gcd a b dvd a" by (rule gcd_dvd1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   405
   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
   406
   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
   407
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   408
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   409
lemma euclidean_size_gcd_le2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   410
  "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
   411
  by (subst gcd.commute, rule euclidean_size_gcd_le1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   412
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   413
lemma euclidean_size_gcd_less1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   414
  assumes "a \<noteq> 0" and "\<not>a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   415
  shows "euclidean_size (gcd a b) < euclidean_size a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   416
proof (rule ccontr)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   417
  assume "\<not>euclidean_size (gcd a b) < euclidean_size a"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   418
  with \<open>a \<noteq> 0\<close> have "euclidean_size (gcd a b) = euclidean_size a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   419
    by (intro le_antisym, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   420
  with assms have "a dvd gcd a b" by (auto intro: dvd_euclidean_size_eq_imp_dvd)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   421
  hence "a dvd b" using dvd_gcd_D2 by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   422
  with \<open>\<not>a dvd b\<close> show False by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   423
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   424
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   425
lemma euclidean_size_gcd_less2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   426
  assumes "b \<noteq> 0" and "\<not>b dvd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   427
  shows "euclidean_size (gcd a b) < euclidean_size b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   428
  using assms by (subst gcd.commute, rule euclidean_size_gcd_less1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   429
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   430
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
   431
  apply (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   432
  apply (rule dvd_trans, rule gcd_dvd1, simp add: unit_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   433
  apply (rule gcd_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   434
  apply (rule gcd_greatest, simp add: unit_simps, assumption)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   435
  apply (subst normalization_factor_gcd, simp add: gcd_0)
58023
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
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   447
lemma gcd_idem: "gcd a a = a div normalization_factor a"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   448
  by (cases "a = 0") (simp add: gcd_0_left, rule sym, rule gcdI, simp_all)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   449
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   450
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
   451
  apply (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   452
  apply (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   453
  apply (rule gcd_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   454
  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
   455
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   456
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   457
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   458
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
   459
  apply (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   460
  apply simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   461
  apply (rule dvd_trans, rule gcd_dvd2, rule gcd_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   462
  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
   463
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   464
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   465
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   466
lemma comp_fun_idem_gcd: "comp_fun_idem gcd"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   467
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   468
  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
   469
    by (simp add: fun_eq_iff ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   470
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   471
  fix a show "gcd a \<circ> gcd a = gcd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   472
    by (simp add: fun_eq_iff gcd_left_idem)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   473
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   474
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   475
lemma coprime_dvd_mult:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   476
  assumes "gcd c b = 1" and "c dvd a * b"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   477
  shows "c dvd a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   478
proof -
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   479
  let ?nf = "normalization_factor"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   480
  from assms gcd_mult_distrib [of a c b] 
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   481
    have A: "a = gcd (a * c) (a * b) * ?nf a" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   482
  from \<open>c dvd a * b\<close> show ?thesis by (subst A, simp_all add: gcd_greatest)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   483
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   484
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   485
lemma coprime_dvd_mult_iff:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   486
  "gcd c b = 1 \<Longrightarrow> (c dvd a * b) = (c dvd a)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   487
  by (rule, rule coprime_dvd_mult, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   488
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   489
lemma gcd_dvd_antisym:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   490
  "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
   491
proof (rule gcdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   492
  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
   493
  have "gcd c d dvd c" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   494
  with A show "gcd a b dvd c" by (rule dvd_trans)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   495
  have "gcd c d dvd d" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   496
  with A show "gcd a b dvd d" by (rule dvd_trans)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   497
  show "normalization_factor (gcd a b) = (if gcd a b = 0 then 0 else 1)"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   498
    by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   499
  fix l assume "l dvd c" and "l dvd d"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   500
  hence "l dvd gcd c d" by (rule gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   501
  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
   502
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   503
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   504
lemma gcd_mult_cancel:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   505
  assumes "gcd k n = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   506
  shows "gcd (k * m) n = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   507
proof (rule gcd_dvd_antisym)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   508
  have "gcd (gcd (k * m) n) k = gcd (gcd k n) (k * m)" by (simp add: ac_simps)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   509
  also note \<open>gcd k n = 1\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   510
  finally have "gcd (gcd (k * m) n) k = 1" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   511
  hence "gcd (k * m) n dvd m" by (rule coprime_dvd_mult, simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   512
  moreover have "gcd (k * m) n dvd n" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   513
  ultimately show "gcd (k * m) n dvd gcd m n" by (rule gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   514
  have "gcd m n dvd (k * m)" and "gcd m n dvd n" by simp_all
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   515
  then show "gcd m n dvd gcd (k * m) n" by (rule gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   516
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   517
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   518
lemma coprime_crossproduct:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   519
  assumes [simp]: "gcd a d = 1" "gcd b c = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   520
  shows "associated (a * c) (b * d) \<longleftrightarrow> associated a b \<and> associated c d" (is "?lhs \<longleftrightarrow> ?rhs")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   521
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   522
  assume ?rhs then show ?lhs unfolding associated_def by (fast intro: mult_dvd_mono)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   523
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   524
  assume ?lhs
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   525
  from \<open>?lhs\<close> have "a dvd b * d" unfolding associated_def by (metis dvd_mult_left) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   526
  hence "a dvd b" by (simp add: coprime_dvd_mult_iff)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   527
  moreover from \<open>?lhs\<close> have "b dvd a * c" unfolding associated_def by (metis dvd_mult_left) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   528
  hence "b dvd a" by (simp add: coprime_dvd_mult_iff)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   529
  moreover from \<open>?lhs\<close> have "c dvd d * b" 
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   530
    unfolding associated_def by (auto dest: dvd_mult_right simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   531
  hence "c dvd d" by (simp add: coprime_dvd_mult_iff gcd.commute)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   532
  moreover from \<open>?lhs\<close> have "d dvd c * a"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   533
    unfolding associated_def by (auto dest: dvd_mult_right simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   534
  hence "d dvd c" by (simp add: coprime_dvd_mult_iff gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   535
  ultimately show ?rhs unfolding associated_def by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   536
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   537
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   538
lemma gcd_add1 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   539
  "gcd (m + n) n = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   540
  by (cases "n = 0", simp_all add: gcd_non_0)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   541
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   542
lemma gcd_add2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   543
  "gcd m (m + n) = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   544
  using gcd_add1 [of n m] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   545
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   546
lemma gcd_add_mult: "gcd m (k * m + n) = gcd m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   547
  by (subst gcd.commute, subst gcd_red, simp)
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)"
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   553
  by (auto intro: coprimeI gcd_greatest dvd_gcd_D1 dvd_gcd_D2)
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_mult: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   578
  assumes da: "gcd d a = 1" and db: "gcd d b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   579
  shows "gcd d (a * b) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   580
  apply (subst gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   581
  using da apply (subst gcd_mult_cancel)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   582
  apply (subst gcd.commute, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   583
  apply (subst gcd.commute, rule db)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   584
  done
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_lmult:
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 a = 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 a"
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_rmult:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   596
  assumes dab: "gcd d (a * b) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   597
  shows "gcd d b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   598
proof (rule coprimeI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   599
  fix l assume "l dvd d" and "l dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   600
  hence "l dvd a * b" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   601
  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
   602
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   603
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   604
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
   605
  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
   606
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   607
lemma gcd_coprime:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   608
  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
   609
  shows "gcd a' b' = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   610
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   611
  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
   612
  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
   613
  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
   614
  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
   615
  finally show ?thesis .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   616
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   617
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   618
lemma coprime_power:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   619
  assumes "0 < n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   620
  shows "gcd a (b ^ n) = 1 \<longleftrightarrow> gcd a b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   621
using assms proof (induct n)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   622
  case (Suc n) then show ?case
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   623
    by (cases n) (simp_all add: coprime_mul_eq)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   624
qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   625
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   626
lemma gcd_coprime_exists:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   627
  assumes nz: "gcd a b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   628
  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
   629
  apply (rule_tac x = "a div gcd a b" in exI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   630
  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
   631
  apply (insert nz, auto intro: div_gcd_coprime)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   632
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   633
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   634
lemma coprime_exp:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   635
  "gcd d a = 1 \<Longrightarrow> gcd d (a^n) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   636
  by (induct n, simp_all add: coprime_mult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   637
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   638
lemma coprime_exp2 [intro]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   639
  "gcd a b = 1 \<Longrightarrow> gcd (a^n) (b^m) = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   640
  apply (rule coprime_exp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   641
  apply (subst gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   642
  apply (rule coprime_exp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   643
  apply (subst gcd.commute)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   644
  apply assumption
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   645
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   646
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   647
lemma gcd_exp:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   648
  "gcd (a^n) (b^n) = (gcd a b) ^ n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   649
proof (cases "a = 0 \<and> b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   650
  assume "a = 0 \<and> b = 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   651
  then show ?thesis by (cases n, simp_all add: gcd_0_left)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   652
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   653
  assume A: "\<not>(a = 0 \<and> b = 0)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   654
  hence "1 = gcd ((a div gcd a b)^n) ((b div gcd a b)^n)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   655
    using div_gcd_coprime by (subst sym, auto simp: div_gcd_coprime)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   656
  hence "(gcd a b) ^ n = (gcd a b) ^ n * ..." by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   657
  also note gcd_mult_distrib
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   658
  also have "normalization_factor ((gcd a b)^n) = 1"
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   659
    by (simp add: normalization_factor_pow A)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   660
  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
   661
    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
   662
  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
   663
    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
   664
  finally show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   665
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   666
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   667
lemma coprime_common_divisor: 
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   668
  "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
   669
  apply (subgoal_tac "a dvd gcd a b")
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   670
  apply simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   671
  apply (erule (1) gcd_greatest)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   672
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   673
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   674
lemma division_decomp: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   675
  assumes dc: "a dvd b * c"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   676
  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
   677
proof (cases "gcd a b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   678
  assume "gcd a b = 0"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   679
  hence "a = 0 \<and> b = 0" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   680
  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
   681
  then show ?thesis by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   682
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   683
  let ?d = "gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   684
  assume "?d \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   685
  from gcd_coprime_exists[OF this]
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   686
    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
   687
    by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   688
  from ab'(1) have "a' dvd a" unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   689
  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
   690
  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
   691
  hence "?d * a' dvd ?d * (b' * c)" by (simp add: mult_ac)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   692
  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
   693
  with coprime_dvd_mult[OF ab'(3)] 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   694
    have "a' dvd c" by (subst (asm) ac_simps, blast)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   695
  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
   696
  then show ?thesis by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   697
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   698
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   699
lemma pow_divs_pow:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   700
  assumes ab: "a ^ n dvd b ^ n" and n: "n \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   701
  shows "a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   702
proof (cases "gcd a b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   703
  assume "gcd a b = 0"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   704
  then show ?thesis by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   705
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   706
  let ?d = "gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   707
  assume "?d \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   708
  from n obtain m where m: "n = Suc m" by (cases n, simp_all)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   709
  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
   710
  from gcd_coprime_exists[OF \<open>?d \<noteq> 0\<close>]
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   711
    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
   712
    by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   713
  from ab have "(a' * ?d) ^ n dvd (b' * ?d) ^ n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   714
    by (simp add: ab'(1,2)[symmetric])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   715
  hence "?d^n * a'^n dvd ?d^n * b'^n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   716
    by (simp only: power_mult_distrib ac_simps)
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   717
  with zn have "a'^n dvd b'^n" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   718
  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
   719
  hence "a' dvd b'^m * b'" by (simp add: m ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   720
  with coprime_dvd_mult[OF coprime_exp[OF ab'(3), of m]]
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   721
    have "a' dvd b'" by (subst (asm) ac_simps, blast)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   722
  hence "a'*?d dvd b'*?d" by (rule mult_dvd_mono, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   723
  with ab'(1,2) show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   724
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   725
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   726
lemma pow_divs_eq [simp]:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   727
  "n \<noteq> 0 \<Longrightarrow> a ^ n dvd b ^ n \<longleftrightarrow> a dvd b"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   728
  by (auto intro: pow_divs_pow dvd_power_same)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   729
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   730
lemma divs_mult:
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   731
  assumes mr: "m dvd r" and nr: "n dvd r" and mn: "gcd m n = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   732
  shows "m * n dvd r"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   733
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   734
  from mr nr obtain m' n' where m': "r = m*m'" and n': "r = n*n'"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   735
    unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   736
  from mr n' have "m dvd n'*n" by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   737
  hence "m dvd n'" using coprime_dvd_mult_iff[OF mn] by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   738
  then obtain k where k: "n' = m*k" unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   739
  with n' have "r = m * n * k" by (simp add: mult_ac)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   740
  then show ?thesis unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   741
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   742
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   743
lemma coprime_plus_one [simp]: "gcd (n + 1) n = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   744
  by (subst add_commute, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   745
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   746
lemma setprod_coprime [rule_format]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   747
  "(\<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
   748
  apply (cases "finite A")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   749
  apply (induct set: finite)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   750
  apply (auto simp add: gcd_mult_cancel)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   751
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   752
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   753
lemma coprime_divisors: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   754
  assumes "d dvd a" "e dvd b" "gcd a b = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   755
  shows "gcd d e = 1" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   756
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   757
  from assms obtain k l where "a = d * k" "b = e * l"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   758
    unfolding dvd_def by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   759
  with assms have "gcd (d * k) (e * l) = 1" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   760
  hence "gcd (d * k) e = 1" by (rule coprime_lmult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   761
  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
   762
  finally have "gcd e d = 1" by (rule coprime_lmult)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   763
  then show ?thesis by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   764
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   765
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   766
lemma invertible_coprime:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   767
  assumes "a * b mod m = 1"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   768
  shows "coprime a m"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   769
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   770
  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
   771
    by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   772
  then have "coprime m (a * b)"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   773
    by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   774
  then have "coprime m a"
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   775
    by (rule coprime_lmult)
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   776
  then show ?thesis
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   777
    by (simp add: ac_simps)
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   778
qed
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   779
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   780
lemma lcm_gcd:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   781
  "lcm a b = a * b div (gcd a b * normalization_factor (a*b))"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   782
  by (simp only: lcm_lcm_eucl gcd_gcd_eucl lcm_eucl_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   783
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   784
lemma lcm_gcd_prod:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   785
  "lcm a b * gcd a b = a * b div normalization_factor (a*b)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   786
proof (cases "a * b = 0")
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   787
  let ?nf = normalization_factor
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   788
  assume "a * b \<noteq> 0"
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   789
  hence "gcd a b \<noteq> 0" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   790
  from lcm_gcd have "lcm a b * gcd a b = gcd a b * (a * b div (?nf (a*b) * gcd a b))" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   791
    by (simp add: mult_ac)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   792
  also from \<open>a * b \<noteq> 0\<close> have "... = a * b div ?nf (a*b)"
60432
68d75cff8809 given up trivial definition
haftmann
parents: 60431
diff changeset
   793
    by (simp add: div_mult_swap mult.commute)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   794
  finally show ?thesis .
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   795
qed (auto simp add: lcm_gcd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   796
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   797
lemma lcm_dvd1 [iff]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   798
  "a dvd lcm a b"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   799
proof (cases "a*b = 0")
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   800
  assume "a * b \<noteq> 0"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   801
  hence "gcd a b \<noteq> 0" by simp
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   802
  let ?c = "1 div normalization_factor (a * b)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   803
  from \<open>a * b \<noteq> 0\<close> have [simp]: "is_unit (normalization_factor (a * b))" by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   804
  from lcm_gcd_prod[of a b] have "lcm a b * gcd a b = a * ?c * b"
60432
68d75cff8809 given up trivial definition
haftmann
parents: 60431
diff changeset
   805
    by (simp add: div_mult_swap unit_div_commute)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   806
  hence "lcm a b * gcd a b div gcd a b = a * ?c * b div gcd a b" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   807
  with \<open>gcd a b \<noteq> 0\<close> have "lcm a b = a * ?c * b div gcd a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   808
    by (subst (asm) div_mult_self2_is_id, simp_all)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   809
  also have "... = a * (?c * b div gcd a b)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   810
    by (metis div_mult_swap gcd_dvd2 mult_assoc)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   811
  finally show ?thesis by (rule dvdI)
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   812
qed (auto simp add: lcm_gcd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   813
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   814
lemma lcm_least:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   815
  "\<lbrakk>a dvd k; b dvd k\<rbrakk> \<Longrightarrow> lcm a b dvd k"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   816
proof (cases "k = 0")
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   817
  let ?nf = normalization_factor
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   818
  assume "k \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   819
  hence "is_unit (?nf k)" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   820
  hence "?nf k \<noteq> 0" by (metis not_is_unit_0)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   821
  assume A: "a dvd k" "b dvd k"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   822
  hence "gcd a b \<noteq> 0" using \<open>k \<noteq> 0\<close> by auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   823
  from A obtain r s where ar: "k = a * r" and bs: "k = b * s" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   824
    unfolding dvd_def by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   825
  with \<open>k \<noteq> 0\<close> have "r * s \<noteq> 0"
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   826
    by auto (drule sym [of 0], simp)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   827
  hence "is_unit (?nf (r * s))" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   828
  let ?c = "?nf k div ?nf (r*s)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   829
  from \<open>is_unit (?nf k)\<close> and \<open>is_unit (?nf (r * s))\<close> have "is_unit ?c" by (rule unit_div)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   830
  hence "?c \<noteq> 0" using not_is_unit_0 by fast 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   831
  from ar bs have "k * k * gcd s r = ?nf k * k * gcd (k * s) (k * r)"
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   832
    by (subst mult_assoc, subst gcd_mult_distrib[of k s r], simp only: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   833
  also have "... = ?nf k * k * gcd ((r*s) * a) ((r*s) * b)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   834
    by (subst (3) \<open>k = a * r\<close>, subst (3) \<open>k = b * s\<close>, simp add: algebra_simps)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   835
  also have "... = ?c * r*s * k * gcd a b" using \<open>r * s \<noteq> 0\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   836
    by (subst gcd_mult_distrib'[symmetric], simp add: algebra_simps unit_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   837
  finally have "(a*r) * (b*s) * gcd s r = ?c * k * r * s * gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   838
    by (subst ar[symmetric], subst bs[symmetric], simp add: mult_ac)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   839
  hence "a * b * gcd s r * (r * s) = ?c * k * gcd a b * (r * s)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   840
    by (simp add: algebra_simps)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   841
  hence "?c * k * gcd a b = a * b * gcd s r" using \<open>r * s \<noteq> 0\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   842
    by (metis div_mult_self2_is_id)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   843
  also have "... = lcm a b * gcd a b * gcd s r * ?nf (a*b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   844
    by (subst lcm_gcd_prod[of a b], metis gcd_mult_distrib gcd_mult_distrib') 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   845
  also have "... = lcm a b * gcd s r * ?nf (a*b) * gcd a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   846
    by (simp add: algebra_simps)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   847
  finally have "k * ?c = lcm a b * gcd s r * ?nf (a*b)" using \<open>gcd a b \<noteq> 0\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   848
    by (metis mult.commute div_mult_self2_is_id)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   849
  hence "k = lcm a b * (gcd s r * ?nf (a*b)) div ?c" using \<open>?c \<noteq> 0\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   850
    by (metis div_mult_self2_is_id mult_assoc) 
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   851
  also have "... = lcm a b * (gcd s r * ?nf (a*b) div ?c)" using \<open>is_unit ?c\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   852
    by (simp add: unit_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   853
  finally show ?thesis by (rule dvdI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   854
qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   855
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   856
lemma lcm_zero:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   857
  "lcm a b = 0 \<longleftrightarrow> a = 0 \<or> b = 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   858
proof -
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   859
  let ?nf = normalization_factor
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   860
  {
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   861
    assume "a \<noteq> 0" "b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   862
    hence "a * b div ?nf (a * b) \<noteq> 0" by (simp add: no_zero_divisors)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   863
    moreover from \<open>a \<noteq> 0\<close> and \<open>b \<noteq> 0\<close> have "gcd a b \<noteq> 0" by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   864
    ultimately have "lcm a b \<noteq> 0" using lcm_gcd_prod[of a b] by (intro notI, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   865
  } moreover {
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   866
    assume "a = 0 \<or> b = 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   867
    hence "lcm a b = 0" by (elim disjE, simp_all add: lcm_gcd)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   868
  }
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   869
  ultimately show ?thesis by blast
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   870
qed
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
lemmas lcm_0_iff = lcm_zero
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   873
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   874
lemma gcd_lcm: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   875
  assumes "lcm a b \<noteq> 0"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   876
  shows "gcd a b = a * b div (lcm a b * normalization_factor (a * b))"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   877
proof-
59009
348561aa3869 generalized lemmas (particularly concerning dvd) as far as appropriate
haftmann
parents: 58953
diff changeset
   878
  from assms have "gcd a b \<noteq> 0" by (simp add: lcm_zero)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   879
  let ?c = "normalization_factor (a * b)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   880
  from \<open>lcm a b \<noteq> 0\<close> have "?c \<noteq> 0" by (intro notI, simp add: lcm_zero no_zero_divisors)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   881
  hence "is_unit ?c" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   882
  from lcm_gcd_prod [of a b] have "gcd a b = a * b div ?c div lcm a b"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   883
    by (subst (2) div_mult_self2_is_id[OF \<open>lcm a b \<noteq> 0\<close>, symmetric], simp add: mult_ac)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   884
  also from \<open>is_unit ?c\<close> have "... = a * b div (lcm a b * ?c)"
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   885
    by (metis \<open>?c \<noteq> 0\<close> div_mult_mult1 dvd_mult_div_cancel mult_commute normalization_factor_dvd')
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
   886
  finally show ?thesis .
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   887
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   888
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   889
lemma normalization_factor_lcm [simp]:
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   890
  "normalization_factor (lcm a b) = (if a = 0 \<or> b = 0 then 0 else 1)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   891
proof (cases "a = 0 \<or> b = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   892
  case True then show ?thesis
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   893
    by (auto simp add: lcm_gcd) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   894
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   895
  case False
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   896
  let ?nf = normalization_factor
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   897
  from lcm_gcd_prod[of a b] 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   898
    have "?nf (lcm a b) * ?nf (gcd a b) = ?nf (a*b) div ?nf (a*b)"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   899
    by (metis div_by_0 div_self normalization_correct normalization_factor_0 normalization_factor_mult)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   900
  also have "... = (if a*b = 0 then 0 else 1)"
58953
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   901
    by simp
2e19b392d9e3 self-contained simp rules for dvd on numerals
haftmann
parents: 58889
diff changeset
   902
  finally show ?thesis using False by simp
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   903
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   904
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   905
lemma lcm_dvd2 [iff]: "b dvd lcm a b"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   906
  using lcm_dvd1 [of b a] by (simp add: lcm_gcd ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   907
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   908
lemma lcmI:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   909
  "\<lbrakk>a dvd k; b dvd k; \<And>l. a dvd l \<Longrightarrow> b dvd l \<Longrightarrow> k dvd l;
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   910
    normalization_factor k = (if k = 0 then 0 else 1)\<rbrakk> \<Longrightarrow> k = lcm a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   911
  by (intro normed_associated_imp_eq) (auto simp: associated_def intro: lcm_least)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   912
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   913
sublocale lcm!: abel_semigroup lcm
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   914
proof
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   915
  fix a b c
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   916
  show "lcm (lcm a b) c = lcm a (lcm b c)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   917
  proof (rule lcmI)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   918
    have "a dvd lcm a b" and "lcm a b dvd lcm (lcm a b) c" by simp_all
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   919
    then show "a dvd lcm (lcm a b) c" by (rule dvd_trans)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   920
    
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   921
    have "b dvd lcm a b" and "lcm a b dvd lcm (lcm a b) c" by simp_all
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   922
    hence "b dvd lcm (lcm a b) c" by (rule dvd_trans)
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   923
    moreover have "c dvd lcm (lcm a b) c" by simp
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   924
    ultimately show "lcm b c dvd lcm (lcm a b) c" by (rule lcm_least)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   925
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   926
    fix l assume "a dvd l" and "lcm b c dvd l"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   927
    have "b dvd lcm b c" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   928
    from this and \<open>lcm b c dvd l\<close> have "b dvd l" by (rule dvd_trans)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   929
    have "c dvd lcm b c" by simp
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   930
    from this and \<open>lcm b c dvd l\<close> have "c dvd l" by (rule dvd_trans)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   931
    from \<open>a dvd l\<close> and \<open>b dvd l\<close> have "lcm a b dvd l" by (rule lcm_least)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   932
    from this and \<open>c dvd l\<close> show "lcm (lcm a b) c dvd l" by (rule lcm_least)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   933
  qed (simp add: lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   934
next
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   935
  fix a b
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   936
  show "lcm a b = lcm b a"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   937
    by (simp add: lcm_gcd ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   938
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   939
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   940
lemma dvd_lcm_D1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   941
  "lcm m n dvd k \<Longrightarrow> m dvd k"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   942
  by (rule dvd_trans, rule lcm_dvd1, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   943
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   944
lemma dvd_lcm_D2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   945
  "lcm m n dvd k \<Longrightarrow> n dvd k"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   946
  by (rule dvd_trans, rule lcm_dvd2, assumption)
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 gcd_dvd_lcm [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   949
  "gcd a b dvd lcm a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   950
  by (metis dvd_trans gcd_dvd2 lcm_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   951
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   952
lemma lcm_1_iff:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   953
  "lcm a b = 1 \<longleftrightarrow> is_unit a \<and> is_unit b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   954
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   955
  assume "lcm a b = 1"
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   956
  then show "is_unit a \<and> is_unit b" by auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   957
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   958
  assume "is_unit a \<and> is_unit b"
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   959
  hence "a dvd 1" and "b dvd 1" by simp_all
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   960
  hence "is_unit (lcm a b)" by (rule lcm_least)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   961
  hence "lcm a b = normalization_factor (lcm a b)"
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   962
    by (subst normalization_factor_unit, simp_all)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
   963
  also have "\<dots> = 1" using \<open>is_unit a \<and> is_unit b\<close>
59061
67771d267ff2 prefer abbrev for is_unit
haftmann
parents: 59010
diff changeset
   964
    by auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   965
  finally show "lcm a b = 1" .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   966
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   967
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   968
lemma lcm_0_left [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   969
  "lcm 0 a = 0"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   970
  by (rule sym, rule lcmI, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   971
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   972
lemma lcm_0 [simp]:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   973
  "lcm a 0 = 0"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   974
  by (rule sym, rule lcmI, simp_all)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   975
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   976
lemma lcm_unique:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   977
  "a dvd d \<and> b dvd d \<and> 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   978
  normalization_factor d = (if d = 0 then 0 else 1) \<and>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   979
  (\<forall>e. a dvd e \<and> b dvd e \<longrightarrow> d dvd e) \<longleftrightarrow> d = lcm a b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   980
  by (rule, auto intro: lcmI simp: lcm_least lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   981
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   982
lemma dvd_lcm_I1 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   983
  "k dvd m \<Longrightarrow> k dvd lcm m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   984
  by (metis lcm_dvd1 dvd_trans)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   985
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   986
lemma dvd_lcm_I2 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   987
  "k dvd n \<Longrightarrow> k dvd lcm m n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   988
  by (metis lcm_dvd2 dvd_trans)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   989
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   990
lemma lcm_1_left [simp]:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   991
  "lcm 1 a = a div normalization_factor a"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   992
  by (cases "a = 0") (simp, rule sym, rule lcmI, simp_all)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   993
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   994
lemma lcm_1_right [simp]:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   995
  "lcm a 1 = a div normalization_factor a"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
   996
  using lcm_1_left [of a] by (simp add: ac_simps)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   997
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
   998
lemma lcm_coprime:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
   999
  "gcd a b = 1 \<Longrightarrow> lcm a b = a * b div normalization_factor (a*b)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1000
  by (subst lcm_gcd) simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1001
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1002
lemma lcm_proj1_if_dvd: 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1003
  "b dvd a \<Longrightarrow> lcm a b = a div normalization_factor a"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1004
  by (cases "a = 0") (simp, rule sym, rule lcmI, simp_all)
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 lcm_proj2_if_dvd: 
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1007
  "a dvd b \<Longrightarrow> lcm a b = b div normalization_factor b"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1008
  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
  1009
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1010
lemma lcm_proj1_iff:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1011
  "lcm m n = m div normalization_factor m \<longleftrightarrow> n dvd m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1012
proof
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1013
  assume A: "lcm m n = m div normalization_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1014
  show "n dvd m"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1015
  proof (cases "m = 0")
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1016
    assume [simp]: "m \<noteq> 0"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1017
    from A have B: "m = lcm m n * normalization_factor m"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1018
      by (simp add: unit_eq_div2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1019
    show ?thesis by (subst B, simp)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1020
  qed simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1021
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1022
  assume "n dvd m"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1023
  then show "lcm m n = m div normalization_factor m" by (rule lcm_proj1_if_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1024
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1025
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1026
lemma lcm_proj2_iff:
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1027
  "lcm m n = n div normalization_factor n \<longleftrightarrow> m dvd n"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1028
  using lcm_proj1_iff [of n m] by (simp add: ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1029
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1030
lemma euclidean_size_lcm_le1: 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1031
  assumes "a \<noteq> 0" and "b \<noteq> 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1032
  shows "euclidean_size a \<le> euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1033
proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1034
  have "a dvd lcm a b" by (rule lcm_dvd1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1035
  then obtain c where A: "lcm a b = a * c" unfolding dvd_def by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1036
  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
  1037
  then show ?thesis by (subst A, intro size_mult_mono)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1038
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1039
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1040
lemma euclidean_size_lcm_le2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1041
  "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
  1042
  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
  1043
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1044
lemma euclidean_size_lcm_less1:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1045
  assumes "b \<noteq> 0" and "\<not>b dvd a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1046
  shows "euclidean_size a < euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1047
proof (rule ccontr)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1048
  from assms have "a \<noteq> 0" by auto
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1049
  assume "\<not>euclidean_size a < euclidean_size (lcm a b)"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1050
  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
  1051
    by (intro le_antisym, simp, intro euclidean_size_lcm_le1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1052
  with assms have "lcm a b dvd a" 
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1053
    by (rule_tac dvd_euclidean_size_eq_imp_dvd) (auto simp: lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1054
  hence "b dvd a" by (rule dvd_lcm_D2)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1055
  with \<open>\<not>b dvd a\<close> show False by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1056
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1057
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1058
lemma euclidean_size_lcm_less2:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1059
  assumes "a \<noteq> 0" and "\<not>a dvd b"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1060
  shows "euclidean_size b < euclidean_size (lcm a b)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1061
  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
  1062
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1063
lemma lcm_mult_unit1:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1064
  "is_unit a \<Longrightarrow> lcm (b * a) c = lcm b c"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1065
  apply (rule lcmI)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1066
  apply (rule dvd_trans[of _ "b * a"], simp, rule lcm_dvd1)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1067
  apply (rule lcm_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1068
  apply (rule lcm_least, simp add: unit_simps, assumption)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1069
  apply (subst normalization_factor_lcm, simp add: lcm_zero)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1070
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1071
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1072
lemma lcm_mult_unit2:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1073
  "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
  1074
  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
  1075
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1076
lemma lcm_div_unit1:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1077
  "is_unit a \<Longrightarrow> lcm (b div a) c = lcm b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
  1078
  by (erule is_unitE [of _ b]) (simp add: lcm_mult_unit1) 
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1079
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1080
lemma lcm_div_unit2:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1081
  "is_unit a \<Longrightarrow> lcm b (c div a) = lcm b c"
60433
720f210c5b1d tuned lemmas and proofs
haftmann
parents: 60432
diff changeset
  1082
  by (erule is_unitE [of _ c]) (simp add: lcm_mult_unit2)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1083
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1084
lemma lcm_left_idem:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1085
  "lcm a (lcm a b) = lcm a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1086
  apply (rule lcmI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1087
  apply simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1088
  apply (subst lcm.assoc [symmetric], rule lcm_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1089
  apply (rule lcm_least, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1090
  apply (erule (1) lcm_least)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1091
  apply (auto simp: lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1092
  done
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 lcm_right_idem:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1095
  "lcm (lcm a b) b = lcm a b"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1096
  apply (rule lcmI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1097
  apply (subst lcm.assoc, rule lcm_dvd1)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1098
  apply (rule lcm_dvd2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1099
  apply (rule lcm_least, erule (1) lcm_least, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1100
  apply (auto simp: lcm_zero)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1101
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1102
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1103
lemma comp_fun_idem_lcm: "comp_fun_idem lcm"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1104
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1105
  fix a b show "lcm a \<circ> lcm b = lcm b \<circ> lcm a"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1106
    by (simp add: fun_eq_iff ac_simps)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1107
next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1108
  fix a show "lcm a \<circ> lcm a = lcm a" unfolding o_def
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1109
    by (intro ext, simp add: lcm_left_idem)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1110
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1111
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1112
lemma dvd_Lcm [simp]: "a \<in> A \<Longrightarrow> a dvd Lcm A"
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1113
  and Lcm_dvd [simp]: "(\<forall>a\<in>A. a dvd l') \<Longrightarrow> Lcm A dvd l'"
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1114
  and normalization_factor_Lcm [simp]: 
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1115
          "normalization_factor (Lcm A) = (if Lcm A = 0 then 0 else 1)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1116
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1117
  have "(\<forall>a\<in>A. a dvd Lcm A) \<and> (\<forall>l'. (\<forall>a\<in>A. a dvd l') \<longrightarrow> Lcm A dvd l') \<and>
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1118
    normalization_factor (Lcm A) = (if Lcm A = 0 then 0 else 1)" (is ?thesis)
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1119
  proof (cases "\<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
  1120
    case False
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1121
    hence "Lcm A = 0" by (auto simp: Lcm_Lcm_eucl Lcm_eucl_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1122
    with False show ?thesis by auto
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1123
  next
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1124
    case True
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1125
    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
  1126
    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
  1127
    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
  1128
    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
  1129
      apply (subst n_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1130
      apply (rule LeastI[of _ "euclidean_size l\<^sub>0"])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1131
      apply (rule exI[of _ l\<^sub>0])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1132
      apply (simp add: l\<^sub>0_props)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1133
      done
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1134
    from someI_ex[OF this] have "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
  1135
      unfolding l_def by simp_all
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1136
    {
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1137
      fix l' assume "\<forall>a\<in>A. a dvd l'"
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1138
      with \<open>\<forall>a\<in>A. a dvd l\<close> have "\<forall>a\<in>A. a dvd gcd l l'" by (auto intro: gcd_greatest)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1139
      moreover from \<open>l \<noteq> 0\<close> have "gcd l l' \<noteq> 0" by simp
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1140
      ultimately have "\<exists>b. b \<noteq> 0 \<and> (\<forall>a\<in>A. a dvd b) \<and> euclidean_size b = euclidean_size (gcd l l')"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1141
        by (intro exI[of _ "gcd l l'"], auto)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1142
      hence "euclidean_size (gcd l l') \<ge> n" by (subst n_def) (rule Least_le)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1143
      moreover have "euclidean_size (gcd l l') \<le> n"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1144
      proof -
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1145
        have "gcd l l' dvd l" by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1146
        then obtain a where "l = gcd l l' * a" unfolding dvd_def by blast
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1147
        with \<open>l \<noteq> 0\<close> have "a \<noteq> 0" by auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1148
        hence "euclidean_size (gcd l l') \<le> euclidean_size (gcd l l' * a)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1149
          by (rule size_mult_mono)
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1150
        also have "gcd l l' * a = l" using \<open>l = gcd l l' * a\<close> ..
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1151
        also note \<open>euclidean_size l = n\<close>
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1152
        finally show "euclidean_size (gcd l l') \<le> n" .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1153
      qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1154
      ultimately have "euclidean_size l = euclidean_size (gcd l l')" 
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1155
        by (intro le_antisym, simp_all add: \<open>euclidean_size l = n\<close>)
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1156
      with \<open>l \<noteq> 0\<close> have "l dvd gcd l l'" by (blast intro: dvd_euclidean_size_eq_imp_dvd)
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1157
      hence "l dvd l'" by (blast dest: dvd_gcd_D2)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1158
    }
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1159
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 60517
diff changeset
  1160
    with \<open>(\<forall>a\<in>A. a dvd l)\<close> and normalization_factor_is_unit[OF \<open>l \<noteq> 0\<close>] and \<open>l \<noteq> 0\<close>
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1161
      have "(\<forall>a\<in>A. a dvd l div normalization_factor l) \<and> 
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1162
        (\<forall>l'. (\<forall>a\<in>A. a dvd l') \<longrightarrow> l div normalization_factor l dvd l') \<and>
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1163
        normalization_factor (l div normalization_factor l) = 
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1164
        (if l div normalization_factor l = 0 then 0 else 1)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1165
      by (auto simp: unit_simps)
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1166
    also from True have "l div normalization_factor l = Lcm A"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1167
      by (simp add: Lcm_Lcm_eucl Lcm_eucl_def Let_def n_def l_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1168
    finally show ?thesis .
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1169
  qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1170
  note A = this
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1171
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1172
  {fix a assume "a \<in> A" then show "a dvd Lcm A" using A by blast}
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1173
  {fix l' assume "\<forall>a\<in>A. a dvd l'" then show "Lcm A dvd l'" using A by blast}
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1174
  from A show "normalization_factor (Lcm A) = (if Lcm A = 0 then 0 else 1)" by blast
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1175
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1176
    
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1177
lemma LcmI:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1178
  "(\<And>a. a\<in>A \<Longrightarrow> a dvd l) \<Longrightarrow> (\<And>l'. (\<forall>a\<in>A. a dvd l') \<Longrightarrow> l dvd l') \<Longrightarrow>
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1179
      normalization_factor l = (if l = 0 then 0 else 1) \<Longrightarrow> l = Lcm A"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1180
  by (intro normed_associated_imp_eq)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1181
    (auto intro: Lcm_dvd dvd_Lcm simp: associated_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1182
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1183
lemma Lcm_subset:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1184
  "A \<subseteq> B \<Longrightarrow> Lcm A dvd Lcm B"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1185
  by (blast intro: Lcm_dvd dvd_Lcm)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1186
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1187
lemma Lcm_Un:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1188
  "Lcm (A \<union> B) = lcm (Lcm A) (Lcm B)"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1189
  apply (rule lcmI)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1190
  apply (blast intro: Lcm_subset)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1191
  apply (blast intro: Lcm_subset)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1192
  apply (intro Lcm_dvd ballI, elim UnE)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1193
  apply (rule dvd_trans, erule dvd_Lcm, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1194
  apply (rule dvd_trans, erule dvd_Lcm, assumption)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1195
  apply simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1196
  done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1197
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1198
lemma Lcm_1_iff:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1199
  "Lcm A = 1 \<longleftrightarrow> (\<forall>a\<in>A. is_unit a)"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1200
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1201
  assume "Lcm A = 1"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1202
  then show "\<forall>a\<in>A. is_unit a" by auto
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1203
qed (rule LcmI [symmetric], auto)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1204
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1205
lemma Lcm_no_units:
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1206
  "Lcm A = Lcm (A - {a. is_unit a})"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1207
proof -
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1208
  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
  1209
  hence "Lcm A = lcm (Lcm (A - {a. is_unit a})) (Lcm {a\<in>A. is_unit a})"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1210
    by (simp add: Lcm_Un[symmetric])
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1211
  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
  1212
  finally show ?thesis by simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1213
qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1214
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1215
lemma Lcm_empty [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1216
  "Lcm {} = 1"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1217
  by (simp add: Lcm_1_iff)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1218
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1219
lemma Lcm_eq_0 [simp]:
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1220
  "0 \<in> A \<Longrightarrow> Lcm A = 0"
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1221
  by (drule dvd_Lcm) simp
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1222
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1223
lemma Lcm0_iff':
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1224
  "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
  1225
proof
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1226
  assume "Lcm A = 0"
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1227
  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
  1228
  proof
60430
ce559c850a27 standardized algebraic conventions: prefer a, b, c over x, y, z
haftmann
parents: 59061
diff changeset
  1229
    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
  1230
    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
  1231
    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
  1232
    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
  1233
    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
  1234
      apply (subst n_def)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1235
      apply (rule LeastI[of _ "euclidean_size l\<^sub>0"])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1236
      apply (rule exI[of _ l\<^sub>0])
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1237
      apply (simp add: l\<^sub>0_props)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1238
      done
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1239
    from someI_ex[OF this] have "l \<noteq> 0" unfolding l_def by simp_all
60438
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1240
    hence "l div normalization_factor l \<noteq> 0" by simp
e1c345094813 slight preference for American English
haftmann
parents: 60437
diff changeset
  1241
    also from ex have "l div normalization_factor l = Lcm A"
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1242
       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
  1243
    finally show False using \<open>Lcm A = 0\<close> by contradiction
58023
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1244
  qed
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1245
qed (simp only: Lcm_Lcm_eucl Lcm_eucl_def if_False)
62826b36ac5e generic euclidean algorithm (due to Manuel Eberl)
haftmann
parents:
diff changeset
  1246