author | chaieb |
Mon, 14 Jul 2008 16:13:51 +0200 | |
changeset 27568 | 9949dc7a24de |
parent 27556 | 292098f2efdf |
child 27651 | 16a26996c30e |
permissions | -rw-r--r-- |
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(* Title: HOL/GCD.thy |
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ID: $Id$ |
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Author: Christophe Tabacznyj and Lawrence C Paulson |
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Copyright 1996 University of Cambridge |
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*) |
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header {* The Greatest Common Divisor *} |
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theory GCD |
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imports Plain "~~/src/HOL/Presburger" |
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begin |
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text {* |
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See \cite{davenport92}. \bigskip |
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*} |
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subsection {* Specification of GCD on nats *} |
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definition |
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is_gcd :: "nat \<Rightarrow> nat \<Rightarrow> nat \<Rightarrow> bool" where -- {* @{term gcd} as a relation *} |
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[code func del]: "is_gcd m n p \<longleftrightarrow> p dvd m \<and> p dvd n \<and> |
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(\<forall>d. d dvd m \<longrightarrow> d dvd n \<longrightarrow> d dvd p)" |
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text {* Uniqueness *} |
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lemma is_gcd_unique: "is_gcd a b m \<Longrightarrow> is_gcd a b n \<Longrightarrow> m = n" |
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by (simp add: is_gcd_def) (blast intro: dvd_anti_sym) |
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text {* Connection to divides relation *} |
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lemma is_gcd_dvd: "is_gcd a b m \<Longrightarrow> k dvd a \<Longrightarrow> k dvd b \<Longrightarrow> k dvd m" |
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by (auto simp add: is_gcd_def) |
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text {* Commutativity *} |
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lemma is_gcd_commute: "is_gcd m n k = is_gcd n m k" |
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by (auto simp add: is_gcd_def) |
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subsection {* GCD on nat by Euclid's algorithm *} |
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fun |
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gcd :: "nat => nat => nat" |
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where |
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"gcd m n = (if n = 0 then m else gcd n (m mod n))" |
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lemma gcd_induct [case_names "0" rec]: |
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fixes m n :: nat |
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assumes "\<And>m. P m 0" |
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and "\<And>m n. 0 < n \<Longrightarrow> P n (m mod n) \<Longrightarrow> P m n" |
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shows "P m n" |
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proof (induct m n rule: gcd.induct) |
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case (1 m n) with assms show ?case by (cases "n = 0") simp_all |
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qed |
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lemma gcd_0 [simp]: "gcd m 0 = m" |
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by simp |
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lemma gcd_0_left [simp]: "gcd 0 m = m" |
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by simp |
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lemma gcd_non_0: "n > 0 \<Longrightarrow> gcd m n = gcd n (m mod n)" |
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by simp |
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lemma gcd_1 [simp]: "gcd m (Suc 0) = 1" |
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by simp |
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declare gcd.simps [simp del] |
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text {* |
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\medskip @{term "gcd m n"} divides @{text m} and @{text n}. The |
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conjunctions don't seem provable separately. |
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*} |
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lemma gcd_dvd1 [iff]: "gcd m n dvd m" |
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and gcd_dvd2 [iff]: "gcd m n dvd n" |
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apply (induct m n rule: gcd_induct) |
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apply (simp_all add: gcd_non_0) |
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apply (blast dest: dvd_mod_imp_dvd) |
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done |
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text {* |
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\medskip Maximality: for all @{term m}, @{term n}, @{term k} |
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naturals, if @{term k} divides @{term m} and @{term k} divides |
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@{term n} then @{term k} divides @{term "gcd m n"}. |
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*} |
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lemma gcd_greatest: "k dvd m \<Longrightarrow> k dvd n \<Longrightarrow> k dvd gcd m n" |
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by (induct m n rule: gcd_induct) (simp_all add: gcd_non_0 dvd_mod) |
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text {* |
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\medskip Function gcd yields the Greatest Common Divisor. |
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*} |
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lemma is_gcd: "is_gcd m n (gcd m n) " |
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by (simp add: is_gcd_def gcd_greatest) |
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subsection {* Derived laws for GCD *} |
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lemma gcd_greatest_iff [iff]: "k dvd gcd m n \<longleftrightarrow> k dvd m \<and> k dvd n" |
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by (blast intro!: gcd_greatest intro: dvd_trans) |
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lemma gcd_zero: "gcd m n = 0 \<longleftrightarrow> m = 0 \<and> n = 0" |
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by (simp only: dvd_0_left_iff [symmetric] gcd_greatest_iff) |
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lemma gcd_commute: "gcd m n = gcd n m" |
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apply (rule is_gcd_unique) |
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apply (rule is_gcd) |
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apply (subst is_gcd_commute) |
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apply (simp add: is_gcd) |
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done |
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lemma gcd_assoc: "gcd (gcd k m) n = gcd k (gcd m n)" |
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apply (rule is_gcd_unique) |
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apply (rule is_gcd) |
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apply (simp add: is_gcd_def) |
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apply (blast intro: dvd_trans) |
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done |
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lemma gcd_1_left [simp]: "gcd (Suc 0) m = 1" |
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by (simp add: gcd_commute) |
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text {* |
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\medskip Multiplication laws |
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*} |
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lemma gcd_mult_distrib2: "k * gcd m n = gcd (k * m) (k * n)" |
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-- {* \cite[page 27]{davenport92} *} |
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apply (induct m n rule: gcd_induct) |
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apply simp |
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apply (case_tac "k = 0") |
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apply (simp_all add: mod_geq gcd_non_0 mod_mult_distrib2) |
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done |
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lemma gcd_mult [simp]: "gcd k (k * n) = k" |
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apply (rule gcd_mult_distrib2 [of k 1 n, simplified, symmetric]) |
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done |
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lemma gcd_self [simp]: "gcd k k = k" |
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apply (rule gcd_mult [of k 1, simplified]) |
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done |
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lemma relprime_dvd_mult: "gcd k n = 1 ==> k dvd m * n ==> k dvd m" |
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apply (insert gcd_mult_distrib2 [of m k n]) |
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apply simp |
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apply (erule_tac t = m in ssubst) |
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apply simp |
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done |
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lemma relprime_dvd_mult_iff: "gcd k n = 1 ==> (k dvd m * n) = (k dvd m)" |
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apply (blast intro: relprime_dvd_mult dvd_trans) |
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done |
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lemma gcd_mult_cancel: "gcd k n = 1 ==> gcd (k * m) n = gcd m n" |
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apply (rule dvd_anti_sym) |
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apply (rule gcd_greatest) |
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apply (rule_tac n = k in relprime_dvd_mult) |
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apply (simp add: gcd_assoc) |
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apply (simp add: gcd_commute) |
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apply (simp_all add: mult_commute) |
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apply (blast intro: dvd_trans) |
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done |
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text {* \medskip Addition laws *} |
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lemma gcd_add1 [simp]: "gcd (m + n) n = gcd m n" |
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apply (case_tac "n = 0") |
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apply (simp_all add: gcd_non_0) |
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done |
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lemma gcd_add2 [simp]: "gcd m (m + n) = gcd m n" |
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proof - |
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have "gcd m (m + n) = gcd (m + n) m" by (rule gcd_commute) |
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also have "... = gcd (n + m) m" by (simp add: add_commute) |
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also have "... = gcd n m" by simp |
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also have "... = gcd m n" by (rule gcd_commute) |
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finally show ?thesis . |
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qed |
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lemma gcd_add2' [simp]: "gcd m (n + m) = gcd m n" |
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apply (subst add_commute) |
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apply (rule gcd_add2) |
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done |
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lemma gcd_add_mult: "gcd m (k * m + n) = gcd m n" |
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by (induct k) (simp_all add: add_assoc) |
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lemma gcd_dvd_prod: "gcd m n dvd m * n" |
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using mult_dvd_mono [of 1] by auto |
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text {* |
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\medskip Division by gcd yields rrelatively primes. |
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*} |
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lemma div_gcd_relprime: |
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assumes nz: "a \<noteq> 0 \<or> b \<noteq> 0" |
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shows "gcd (a div gcd a b) (b div gcd a b) = 1" |
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proof - |
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let ?g = "gcd a b" |
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let ?a' = "a div ?g" |
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let ?b' = "b div ?g" |
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let ?g' = "gcd ?a' ?b'" |
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have dvdg: "?g dvd a" "?g dvd b" by simp_all |
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have dvdg': "?g' dvd ?a'" "?g' dvd ?b'" by simp_all |
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from dvdg dvdg' obtain ka kb ka' kb' where |
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kab: "a = ?g * ka" "b = ?g * kb" "?a' = ?g' * ka'" "?b' = ?g' * kb'" |
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unfolding dvd_def by blast |
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then have "?g * ?a' = (?g * ?g') * ka'" "?g * ?b' = (?g * ?g') * kb'" by simp_all |
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then have dvdgg':"?g * ?g' dvd a" "?g* ?g' dvd b" |
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by (auto simp add: dvd_mult_div_cancel [OF dvdg(1)] |
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dvd_mult_div_cancel [OF dvdg(2)] dvd_def) |
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have "?g \<noteq> 0" using nz by (simp add: gcd_zero) |
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then have gp: "?g > 0" by simp |
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from gcd_greatest [OF dvdgg'] have "?g * ?g' dvd ?g" . |
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with dvd_mult_cancel1 [OF gp] show "?g' = 1" by simp |
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qed |
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subsection {* LCM defined by GCD *} |
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definition |
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lcm :: "nat \<Rightarrow> nat \<Rightarrow> nat" |
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where |
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lcm_def: "lcm m n = m * n div gcd m n" |
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lemma prod_gcd_lcm: |
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"m * n = gcd m n * lcm m n" |
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unfolding lcm_def by (simp add: dvd_mult_div_cancel [OF gcd_dvd_prod]) |
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lemma lcm_0 [simp]: "lcm m 0 = 0" |
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unfolding lcm_def by simp |
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lemma lcm_1 [simp]: "lcm m 1 = m" |
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unfolding lcm_def by simp |
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lemma lcm_0_left [simp]: "lcm 0 n = 0" |
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unfolding lcm_def by simp |
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lemma lcm_1_left [simp]: "lcm 1 m = m" |
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unfolding lcm_def by simp |
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241 |
|
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lemma dvd_pos: |
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fixes n m :: nat |
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assumes "n > 0" and "m dvd n" |
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shows "m > 0" |
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using assms by (cases m) auto |
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lemma lcm_least: |
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23431
diff
changeset
|
249 |
assumes "m dvd k" and "n dvd k" |
27556 | 250 |
shows "lcm m n dvd k" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
251 |
proof (cases k) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
252 |
case 0 then show ?thesis by auto |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
253 |
next |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
254 |
case (Suc _) then have pos_k: "k > 0" by auto |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
255 |
from assms dvd_pos [OF this] have pos_mn: "m > 0" "n > 0" by auto |
27556 | 256 |
with gcd_zero [of m n] have pos_gcd: "gcd m n > 0" by simp |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
257 |
from assms obtain p where k_m: "k = m * p" using dvd_def by blast |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
258 |
from assms obtain q where k_n: "k = n * q" using dvd_def by blast |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
259 |
from pos_k k_m have pos_p: "p > 0" by auto |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
260 |
from pos_k k_n have pos_q: "q > 0" by auto |
27556 | 261 |
have "k * k * gcd q p = k * gcd (k * q) (k * p)" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
262 |
by (simp add: mult_ac gcd_mult_distrib2) |
27556 | 263 |
also have "\<dots> = k * gcd (m * p * q) (n * q * p)" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
264 |
by (simp add: k_m [symmetric] k_n [symmetric]) |
27556 | 265 |
also have "\<dots> = k * p * q * gcd m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
266 |
by (simp add: mult_ac gcd_mult_distrib2) |
27556 | 267 |
finally have "(m * p) * (n * q) * gcd q p = k * p * q * gcd m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
268 |
by (simp only: k_m [symmetric] k_n [symmetric]) |
27556 | 269 |
then have "p * q * m * n * gcd q p = p * q * k * gcd m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
270 |
by (simp add: mult_ac) |
27556 | 271 |
with pos_p pos_q have "m * n * gcd q p = k * gcd m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
272 |
by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
273 |
with prod_gcd_lcm [of m n] |
27556 | 274 |
have "lcm m n * gcd q p * gcd m n = k * gcd m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
275 |
by (simp add: mult_ac) |
27556 | 276 |
with pos_gcd have "lcm m n * gcd q p = k" by simp |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
277 |
then show ?thesis using dvd_def by auto |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
278 |
qed |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
279 |
|
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
280 |
lemma lcm_dvd1 [iff]: |
27556 | 281 |
"m dvd lcm m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
282 |
proof (cases m) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
283 |
case 0 then show ?thesis by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
284 |
next |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
285 |
case (Suc _) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
286 |
then have mpos: "m > 0" by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
287 |
show ?thesis |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
288 |
proof (cases n) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
289 |
case 0 then show ?thesis by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
290 |
next |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
291 |
case (Suc _) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
292 |
then have npos: "n > 0" by simp |
27556 | 293 |
have "gcd m n dvd n" by simp |
294 |
then obtain k where "n = gcd m n * k" using dvd_def by auto |
|
295 |
then have "m * n div gcd m n = m * (gcd m n * k) div gcd m n" by (simp add: mult_ac) |
|
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
296 |
also have "\<dots> = m * k" using mpos npos gcd_zero by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
297 |
finally show ?thesis by (simp add: lcm_def) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
298 |
qed |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
299 |
qed |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
300 |
|
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
301 |
lemma lcm_dvd2 [iff]: |
27556 | 302 |
"n dvd lcm m n" |
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
303 |
proof (cases n) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
304 |
case 0 then show ?thesis by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
305 |
next |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
306 |
case (Suc _) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
307 |
then have npos: "n > 0" by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
308 |
show ?thesis |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
309 |
proof (cases m) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
310 |
case 0 then show ?thesis by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
311 |
next |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
312 |
case (Suc _) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
313 |
then have mpos: "m > 0" by simp |
27556 | 314 |
have "gcd m n dvd m" by simp |
315 |
then obtain k where "m = gcd m n * k" using dvd_def by auto |
|
316 |
then have "m * n div gcd m n = (gcd m n * k) * n div gcd m n" by (simp add: mult_ac) |
|
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
317 |
also have "\<dots> = n * k" using mpos npos gcd_zero by simp |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
318 |
finally show ?thesis by (simp add: lcm_def) |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
319 |
qed |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
320 |
qed |
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
321 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
322 |
lemma gcd_add1_eq: "gcd (m + k) k = gcd (m + k) m" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
323 |
by (simp add: gcd_commute) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
324 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
325 |
lemma gcd_diff2: "m \<le> n ==> gcd n (n - m) = gcd n m" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
326 |
apply (subgoal_tac "n = m + (n - m)") |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
327 |
apply (erule ssubst, rule gcd_add1_eq, simp) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
328 |
done |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
329 |
|
23687
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
330 |
|
06884f7ffb18
extended - convers now basic lcm properties also
haftmann
parents:
23431
diff
changeset
|
331 |
subsection {* GCD and LCM on integers *} |
22367 | 332 |
|
333 |
definition |
|
27556 | 334 |
zgcd :: "int \<Rightarrow> int \<Rightarrow> int" where |
335 |
"zgcd i j = int (gcd (nat (abs i)) (nat (abs j)))" |
|
22367 | 336 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
337 |
lemma zgcd_zdvd1 [iff,simp]: "zgcd i j dvd i" |
27556 | 338 |
by (simp add: zgcd_def int_dvd_iff) |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
339 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
340 |
lemma zgcd_zdvd2 [iff,simp]: "zgcd i j dvd j" |
27556 | 341 |
by (simp add: zgcd_def int_dvd_iff) |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
342 |
|
27556 | 343 |
lemma zgcd_pos: "zgcd i j \<ge> 0" |
344 |
by (simp add: zgcd_def) |
|
22367 | 345 |
|
27556 | 346 |
lemma zgcd0 [simp]: "(zgcd i j = 0) = (i = 0 \<and> j = 0)" |
347 |
by (simp add: zgcd_def gcd_zero) arith |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
348 |
|
27556 | 349 |
lemma zgcd_commute: "zgcd i j = zgcd j i" |
350 |
unfolding zgcd_def by (simp add: gcd_commute) |
|
22367 | 351 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
352 |
lemma zgcd_zminus [simp]: "zgcd (- i) j = zgcd i j" |
27556 | 353 |
unfolding zgcd_def by simp |
22367 | 354 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
355 |
lemma zgcd_zminus2 [simp]: "zgcd i (- j) = zgcd i j" |
27556 | 356 |
unfolding zgcd_def by simp |
22367 | 357 |
|
27556 | 358 |
lemma zrelprime_dvd_mult: "zgcd i j = 1 \<Longrightarrow> i dvd k * j \<Longrightarrow> i dvd k" |
359 |
unfolding zgcd_def |
|
22367 | 360 |
proof - |
27556 | 361 |
assume "int (gcd (nat \<bar>i\<bar>) (nat \<bar>j\<bar>)) = 1" "i dvd k * j" |
362 |
then have g: "gcd (nat \<bar>i\<bar>) (nat \<bar>j\<bar>) = 1" by simp |
|
22367 | 363 |
from `i dvd k * j` obtain h where h: "k*j = i*h" unfolding dvd_def by blast |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
364 |
have th: "nat \<bar>i\<bar> dvd nat \<bar>k\<bar> * nat \<bar>j\<bar>" |
22367 | 365 |
unfolding dvd_def |
366 |
by (rule_tac x= "nat \<bar>h\<bar>" in exI, simp add: h nat_abs_mult_distrib [symmetric]) |
|
367 |
from relprime_dvd_mult [OF g th] obtain h' where h': "nat \<bar>k\<bar> = nat \<bar>i\<bar> * h'" |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
368 |
unfolding dvd_def by blast |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
369 |
from h' have "int (nat \<bar>k\<bar>) = int (nat \<bar>i\<bar> * h')" by simp |
23431
25ca91279a9b
change simp rules for of_nat to work like int did previously (reorient of_nat_Suc, remove of_nat_mult [simp]); preserve original variable names in legacy int theorems
huffman
parents:
23365
diff
changeset
|
370 |
then have "\<bar>k\<bar> = \<bar>i\<bar> * int h'" by (simp add: int_mult) |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
371 |
then show ?thesis |
22367 | 372 |
apply (subst zdvd_abs1 [symmetric]) |
373 |
apply (subst zdvd_abs2 [symmetric]) |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
374 |
apply (unfold dvd_def) |
22367 | 375 |
apply (rule_tac x = "int h'" in exI, simp) |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
376 |
done |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
377 |
qed |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
378 |
|
27556 | 379 |
lemma int_nat_abs: "int (nat (abs x)) = abs x" by arith |
22367 | 380 |
|
27556 | 381 |
lemma zgcd_greatest: |
22367 | 382 |
assumes "k dvd m" and "k dvd n" |
27556 | 383 |
shows "k dvd zgcd m n" |
22367 | 384 |
proof - |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
385 |
let ?k' = "nat \<bar>k\<bar>" |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
386 |
let ?m' = "nat \<bar>m\<bar>" |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
387 |
let ?n' = "nat \<bar>n\<bar>" |
22367 | 388 |
from `k dvd m` and `k dvd n` have dvd': "?k' dvd ?m'" "?k' dvd ?n'" |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
389 |
unfolding zdvd_int by (simp_all only: int_nat_abs zdvd_abs1 zdvd_abs2) |
27556 | 390 |
from gcd_greatest [OF dvd'] have "int (nat \<bar>k\<bar>) dvd zgcd m n" |
391 |
unfolding zgcd_def by (simp only: zdvd_int) |
|
392 |
then have "\<bar>k\<bar> dvd zgcd m n" by (simp only: int_nat_abs) |
|
393 |
then show "k dvd zgcd m n" by (simp add: zdvd_abs1) |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
394 |
qed |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
395 |
|
27556 | 396 |
lemma div_zgcd_relprime: |
22367 | 397 |
assumes nz: "a \<noteq> 0 \<or> b \<noteq> 0" |
27556 | 398 |
shows "zgcd (a div (zgcd a b)) (b div (zgcd a b)) = 1" |
22367 | 399 |
proof - |
25112 | 400 |
from nz have nz': "nat \<bar>a\<bar> \<noteq> 0 \<or> nat \<bar>b\<bar> \<noteq> 0" by arith |
27556 | 401 |
let ?g = "zgcd a b" |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
402 |
let ?a' = "a div ?g" |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
403 |
let ?b' = "b div ?g" |
27556 | 404 |
let ?g' = "zgcd ?a' ?b'" |
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
405 |
have dvdg: "?g dvd a" "?g dvd b" by (simp_all add: zgcd_zdvd1 zgcd_zdvd2) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
406 |
have dvdg': "?g' dvd ?a'" "?g' dvd ?b'" by (simp_all add: zgcd_zdvd1 zgcd_zdvd2) |
22367 | 407 |
from dvdg dvdg' obtain ka kb ka' kb' where |
408 |
kab: "a = ?g*ka" "b = ?g*kb" "?a' = ?g'*ka'" "?b' = ?g' * kb'" |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
409 |
unfolding dvd_def by blast |
22367 | 410 |
then have "?g* ?a' = (?g * ?g') * ka'" "?g* ?b' = (?g * ?g') * kb'" by simp_all |
411 |
then have dvdgg':"?g * ?g' dvd a" "?g* ?g' dvd b" |
|
412 |
by (auto simp add: zdvd_mult_div_cancel [OF dvdg(1)] |
|
413 |
zdvd_mult_div_cancel [OF dvdg(2)] dvd_def) |
|
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
414 |
have "?g \<noteq> 0" using nz by simp |
27556 | 415 |
then have gp: "?g \<noteq> 0" using zgcd_pos[where i="a" and j="b"] by arith |
416 |
from zgcd_greatest [OF dvdgg'] have "?g * ?g' dvd ?g" . |
|
22367 | 417 |
with zdvd_mult_cancel1 [OF gp] have "\<bar>?g'\<bar> = 1" by simp |
27556 | 418 |
with zgcd_pos show "?g' = 1" by simp |
22027
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
419 |
qed |
e4a08629c4bd
A few lemmas about relative primes when dividing trough gcd
chaieb
parents:
21404
diff
changeset
|
420 |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
421 |
(* IntPrimes stuff *) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
422 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
423 |
lemma zgcd_0 [simp]: "zgcd m 0 = abs m" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
424 |
by (simp add: zgcd_def abs_if) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
425 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
426 |
lemma zgcd_0_left [simp]: "zgcd 0 m = abs m" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
427 |
by (simp add: zgcd_def abs_if) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
428 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
429 |
lemma zgcd_non_0: "0 < n ==> zgcd m n = zgcd n (m mod n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
430 |
apply (frule_tac b = n and a = m in pos_mod_sign) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
431 |
apply (simp del: pos_mod_sign add: zgcd_def abs_if nat_mod_distrib) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
432 |
apply (auto simp add: gcd_non_0 nat_mod_distrib [symmetric] zmod_zminus1_eq_if) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
433 |
apply (frule_tac a = m in pos_mod_bound) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
434 |
apply (simp del: pos_mod_bound add: nat_diff_distrib gcd_diff2 nat_le_eq_zle) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
435 |
done |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
436 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
437 |
lemma zgcd_eq: "zgcd m n = zgcd n (m mod n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
438 |
apply (case_tac "n = 0", simp add: DIVISION_BY_ZERO) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
439 |
apply (auto simp add: linorder_neq_iff zgcd_non_0) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
440 |
apply (cut_tac m = "-m" and n = "-n" in zgcd_non_0, auto) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
441 |
done |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
442 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
443 |
lemma zgcd_1 [simp]: "zgcd m 1 = 1" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
444 |
by (simp add: zgcd_def abs_if) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
445 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
446 |
lemma zgcd_0_1_iff [simp]: "zgcd 0 m = 1 \<longleftrightarrow> \<bar>m\<bar> = 1" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
447 |
by (simp add: zgcd_def abs_if) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
448 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
449 |
lemma zgcd_greatest_iff: "k dvd zgcd m n = (k dvd m \<and> k dvd n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
450 |
by (simp add: zgcd_def abs_if int_dvd_iff dvd_int_iff nat_dvd_iff) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
451 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
452 |
lemma zgcd_1_left [simp]: "zgcd 1 m = 1" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
453 |
by (simp add: zgcd_def gcd_1_left) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
454 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
455 |
lemma zgcd_assoc: "zgcd (zgcd k m) n = zgcd k (zgcd m n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
456 |
by (simp add: zgcd_def gcd_assoc) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
457 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
458 |
lemma zgcd_left_commute: "zgcd k (zgcd m n) = zgcd m (zgcd k n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
459 |
apply (rule zgcd_commute [THEN trans]) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
460 |
apply (rule zgcd_assoc [THEN trans]) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
461 |
apply (rule zgcd_commute [THEN arg_cong]) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
462 |
done |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
463 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
464 |
lemmas zgcd_ac = zgcd_assoc zgcd_commute zgcd_left_commute |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
465 |
-- {* addition is an AC-operator *} |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
466 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
467 |
lemma zgcd_zmult_distrib2: "0 \<le> k ==> k * zgcd m n = zgcd (k * m) (k * n)" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
468 |
by (simp del: minus_mult_right [symmetric] |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
469 |
add: minus_mult_right nat_mult_distrib zgcd_def abs_if |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
470 |
mult_less_0_iff gcd_mult_distrib2 [symmetric] zmult_int [symmetric]) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
471 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
472 |
lemma zgcd_zmult_distrib2_abs: "zgcd (k * m) (k * n) = abs k * zgcd m n" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
473 |
by (simp add: abs_if zgcd_zmult_distrib2) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
474 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
475 |
lemma zgcd_self [simp]: "0 \<le> m ==> zgcd m m = m" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
476 |
by (cut_tac k = m and m = 1 and n = 1 in zgcd_zmult_distrib2, simp_all) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
477 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
478 |
lemma zgcd_zmult_eq_self [simp]: "0 \<le> k ==> zgcd k (k * n) = k" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
479 |
by (cut_tac k = k and m = 1 and n = n in zgcd_zmult_distrib2, simp_all) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
480 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
481 |
lemma zgcd_zmult_eq_self2 [simp]: "0 \<le> k ==> zgcd (k * n) k = k" |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
482 |
by (cut_tac k = k and m = n and n = 1 in zgcd_zmult_distrib2, simp_all) |
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
483 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
484 |
|
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
485 |
definition "zlcm i j = int (lcm(nat(abs i)) (nat(abs j)))" |
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
486 |
|
27556 | 487 |
lemma dvd_zlcm_self1[simp]: "i dvd zlcm i j" |
488 |
by(simp add:zlcm_def dvd_int_iff) |
|
23983 | 489 |
|
27556 | 490 |
lemma dvd_zlcm_self2[simp]: "j dvd zlcm i j" |
491 |
by(simp add:zlcm_def dvd_int_iff) |
|
23983 | 492 |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
493 |
|
27556 | 494 |
lemma dvd_imp_dvd_zlcm1: |
495 |
assumes "k dvd i" shows "k dvd (zlcm i j)" |
|
23983 | 496 |
proof - |
497 |
have "nat(abs k) dvd nat(abs i)" using `k dvd i` |
|
23994 | 498 |
by(simp add:int_dvd_iff[symmetric] dvd_int_iff[symmetric] zdvd_abs1) |
27556 | 499 |
thus ?thesis by(simp add:zlcm_def dvd_int_iff)(blast intro: dvd_trans) |
23983 | 500 |
qed |
501 |
||
27556 | 502 |
lemma dvd_imp_dvd_zlcm2: |
503 |
assumes "k dvd j" shows "k dvd (zlcm i j)" |
|
23983 | 504 |
proof - |
505 |
have "nat(abs k) dvd nat(abs j)" using `k dvd j` |
|
23994 | 506 |
by(simp add:int_dvd_iff[symmetric] dvd_int_iff[symmetric] zdvd_abs1) |
27556 | 507 |
thus ?thesis by(simp add:zlcm_def dvd_int_iff)(blast intro: dvd_trans) |
23983 | 508 |
qed |
509 |
||
23994 | 510 |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
511 |
lemma zdvd_self_abs1: "(d::int) dvd (abs d)" |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
512 |
by (case_tac "d <0", simp_all) |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
513 |
|
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
514 |
lemma zdvd_self_abs2: "(abs (d::int)) dvd d" |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
515 |
by (case_tac "d<0", simp_all) |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
516 |
|
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
517 |
(* lcm a b is positive for positive a and b *) |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
518 |
|
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
519 |
lemma lcm_pos: |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
520 |
assumes mpos: "m > 0" |
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
521 |
and npos: "n>0" |
27556 | 522 |
shows "lcm m n > 0" |
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
523 |
proof(rule ccontr, simp add: lcm_def gcd_zero) |
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
524 |
assume h:"m*n div gcd m n = 0" |
27556 | 525 |
from mpos npos have "gcd m n \<noteq> 0" using gcd_zero by simp |
526 |
hence gcdp: "gcd m n > 0" by simp |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
527 |
with h |
27556 | 528 |
have "m*n < gcd m n" |
529 |
by (cases "m * n < gcd m n") (auto simp add: div_if[OF gcdp, where m="m*n"]) |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
530 |
moreover |
27556 | 531 |
have "gcd m n dvd m" by simp |
532 |
with mpos dvd_imp_le have t1:"gcd m n \<le> m" by simp |
|
27568
9949dc7a24de
Theorem names as in IntPrimes.thy, also several theorems moved from there
chaieb
parents:
27556
diff
changeset
|
533 |
with npos have t1:"gcd m n *n \<le> m*n" by simp |
27556 | 534 |
have "gcd m n \<le> gcd m n*n" using npos by simp |
535 |
with t1 have "gcd m n \<le> m*n" by arith |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
536 |
ultimately show "False" by simp |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
537 |
qed |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
538 |
|
27556 | 539 |
lemma zlcm_pos: |
23983 | 540 |
assumes anz: "a \<noteq> 0" |
541 |
and bnz: "b \<noteq> 0" |
|
27556 | 542 |
shows "0 < zlcm a b" |
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
543 |
proof- |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
544 |
let ?na = "nat (abs a)" |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
545 |
let ?nb = "nat (abs b)" |
23983 | 546 |
have nap: "?na >0" using anz by simp |
547 |
have nbp: "?nb >0" using bnz by simp |
|
27556 | 548 |
have "0 < lcm ?na ?nb" by (rule lcm_pos[OF nap nbp]) |
549 |
thus ?thesis by (simp add: zlcm_def) |
|
23244
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
550 |
qed |
1630951f0512
added lcm, ilcm (lcm for integers) and some lemmas about them;
chaieb
parents:
22367
diff
changeset
|
551 |
|
21256 | 552 |
end |