src/HOL/Library/Primes.thy
author nipkow
Fri Jul 08 11:39:08 2005 +0200 (2005-07-08)
changeset 16762 aafd23b47a5d
parent 16663 13e9c402308b
child 19086 1b3780be6cc2
permissions -rw-r--r--
moved gcd to new GCD.thy
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(*  Title:      HOL/Library/Primes.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 {* Primality on nat *}
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theory Primes
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imports Main
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begin
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constdefs
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  coprime :: "nat => nat => bool"
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  "coprime m n == gcd (m, n) = 1"
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  prime :: "nat \<Rightarrow> bool"
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  "prime p == 1 < p \<and> (\<forall>m. m dvd p --> m = 1 \<or> m = p)"
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lemma two_is_prime: "prime 2"
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  apply (auto simp add: prime_def)
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  apply (case_tac m)
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   apply (auto dest!: dvd_imp_le)
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  done
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lemma prime_imp_relprime: "prime p ==> \<not> p dvd n ==> gcd (p, n) = 1"
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  apply (auto simp add: prime_def)
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  apply (drule_tac x = "gcd (p, n)" in spec)
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  apply auto
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  apply (insert gcd_dvd2 [of p n])
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  apply simp
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  done
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text {*
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  This theorem leads immediately to a proof of the uniqueness of
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  factorization.  If @{term p} divides a product of primes then it is
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  one of those primes.
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*}
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lemma prime_dvd_mult: "prime p ==> p dvd m * n ==> p dvd m \<or> p dvd n"
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  by (blast intro: relprime_dvd_mult prime_imp_relprime)
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lemma prime_dvd_square: "prime p ==> p dvd m^Suc (Suc 0) ==> p dvd m"
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  by (auto dest: prime_dvd_mult)
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lemma prime_dvd_power_two: "prime p ==> p dvd m\<twosuperior> ==> p dvd m"
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  by (rule prime_dvd_square) (simp_all add: power2_eq_square)
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end