src/HOL/GCD.thy
author nipkow
Sun Jul 12 14:48:01 2009 +0200 (2009-07-12)
changeset 31995 8f37cf60b885
parent 31992 f8aed98faae7
child 31996 1d93369079c4
permissions -rw-r--r--
more gcd/lcm lemmas
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(*  Title:      GCD.thy
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    Authors:    Christophe Tabacznyj, Lawrence C. Paulson, Amine Chaieb,
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                Thomas M. Rasmussen, Jeremy Avigad, Tobias Nipkow
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This file deals with the functions gcd and lcm, and properties of
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primes. Definitions and lemmas are proved uniformly for the natural
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numbers and integers.
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This file combines and revises a number of prior developments.
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The original theories "GCD" and "Primes" were by Christophe Tabacznyj
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and Lawrence C. Paulson, based on \cite{davenport92}. They introduced
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gcd, lcm, and prime for the natural numbers.
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The original theory "IntPrimes" was by Thomas M. Rasmussen, and
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extended gcd, lcm, primes to the integers. Amine Chaieb provided
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another extension of the notions to the integers, and added a number
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of results to "Primes" and "GCD". IntPrimes also defined and developed
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the congruence relations on the integers. The notion was extended to
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the natural numbers by Chiaeb.
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Tobias Nipkow cleaned up a lot.
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*)
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header {* GCD *}
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theory GCD
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imports NatTransfer
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begin
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declare One_nat_def [simp del]
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subsection {* gcd *}
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class gcd = zero + one + dvd +
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fixes
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  gcd :: "'a \<Rightarrow> 'a \<Rightarrow> 'a" and
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  lcm :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"
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begin
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abbreviation
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  coprime :: "'a \<Rightarrow> 'a \<Rightarrow> bool"
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where
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  "coprime x y == (gcd x y = 1)"
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end
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class prime = one +
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fixes
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  prime :: "'a \<Rightarrow> bool"
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(* definitions for the natural numbers *)
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instantiation nat :: gcd
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begin
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fun
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  gcd_nat  :: "nat \<Rightarrow> nat \<Rightarrow> nat"
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where
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  "gcd_nat x y =
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   (if y = 0 then x else gcd y (x mod y))"
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definition
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  lcm_nat :: "nat \<Rightarrow> nat \<Rightarrow> nat"
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where
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  "lcm_nat x y = x * y div (gcd x y)"
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instance proof qed
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end
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instantiation nat :: prime
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begin
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definition
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  prime_nat :: "nat \<Rightarrow> bool"
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where
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  [code del]: "prime_nat p = (1 < p \<and> (\<forall>m. m dvd p --> m = 1 \<or> m = p))"
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instance proof qed
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end
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(* definitions for the integers *)
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instantiation int :: gcd
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begin
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definition
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  gcd_int  :: "int \<Rightarrow> int \<Rightarrow> int"
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where
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  "gcd_int x y = int (gcd (nat (abs x)) (nat (abs y)))"
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definition
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  lcm_int :: "int \<Rightarrow> int \<Rightarrow> int"
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where
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  "lcm_int x y = int (lcm (nat (abs x)) (nat (abs y)))"
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instance proof qed
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end
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instantiation int :: prime
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begin
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definition
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  prime_int :: "int \<Rightarrow> bool"
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where
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  [code del]: "prime_int p = prime (nat p)"
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instance proof qed
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end
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subsection {* Set up Transfer *}
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lemma transfer_nat_int_gcd:
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  "(x::int) >= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> gcd (nat x) (nat y) = nat (gcd x y)"
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  "(x::int) >= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> lcm (nat x) (nat y) = nat (lcm x y)"
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  "(x::int) >= 0 \<Longrightarrow> prime (nat x) = prime x"
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  unfolding gcd_int_def lcm_int_def prime_int_def
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  by auto
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lemma transfer_nat_int_gcd_closures:
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  "x >= (0::int) \<Longrightarrow> y >= 0 \<Longrightarrow> gcd x y >= 0"
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  "x >= (0::int) \<Longrightarrow> y >= 0 \<Longrightarrow> lcm x y >= 0"
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  by (auto simp add: gcd_int_def lcm_int_def)
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declare TransferMorphism_nat_int[transfer add return:
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    transfer_nat_int_gcd transfer_nat_int_gcd_closures]
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lemma transfer_int_nat_gcd:
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  "gcd (int x) (int y) = int (gcd x y)"
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  "lcm (int x) (int y) = int (lcm x y)"
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  "prime (int x) = prime x"
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  by (unfold gcd_int_def lcm_int_def prime_int_def, auto)
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lemma transfer_int_nat_gcd_closures:
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  "is_nat x \<Longrightarrow> is_nat y \<Longrightarrow> gcd x y >= 0"
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  "is_nat x \<Longrightarrow> is_nat y \<Longrightarrow> lcm x y >= 0"
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  by (auto simp add: gcd_int_def lcm_int_def)
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declare TransferMorphism_int_nat[transfer add return:
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    transfer_int_nat_gcd transfer_int_nat_gcd_closures]
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subsection {* GCD *}
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(* was gcd_induct *)
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lemma gcd_nat_induct:
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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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  apply (rule gcd_nat.induct)
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  apply (case_tac "y = 0")
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  using assms apply simp_all
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done
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(* specific to int *)
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lemma gcd_neg1_int [simp]: "gcd (-x::int) y = gcd x y"
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  by (simp add: gcd_int_def)
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lemma gcd_neg2_int [simp]: "gcd (x::int) (-y) = gcd x y"
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  by (simp add: gcd_int_def)
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lemma abs_gcd_int[simp]: "abs(gcd (x::int) y) = gcd x y"
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by(simp add: gcd_int_def)
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lemma gcd_abs_int: "gcd (x::int) y = gcd (abs x) (abs y)"
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by (simp add: gcd_int_def)
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lemma gcd_abs1_int[simp]: "gcd (abs x) (y::int) = gcd x y"
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by (metis abs_idempotent gcd_abs_int)
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lemma gcd_abs2_int[simp]: "gcd x (abs y::int) = gcd x y"
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by (metis abs_idempotent gcd_abs_int)
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lemma gcd_cases_int:
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  fixes x :: int and y
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  assumes "x >= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> P (gcd x y)"
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      and "x >= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> P (gcd x (-y))"
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      and "x <= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> P (gcd (-x) y)"
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      and "x <= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> P (gcd (-x) (-y))"
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  shows "P (gcd x y)"
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by (insert prems, auto simp add: gcd_neg1_int gcd_neg2_int, arith)
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lemma gcd_ge_0_int [simp]: "gcd (x::int) y >= 0"
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  by (simp add: gcd_int_def)
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lemma lcm_neg1_int: "lcm (-x::int) y = lcm x y"
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  by (simp add: lcm_int_def)
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lemma lcm_neg2_int: "lcm (x::int) (-y) = lcm x y"
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  by (simp add: lcm_int_def)
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lemma lcm_abs_int: "lcm (x::int) y = lcm (abs x) (abs y)"
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  by (simp add: lcm_int_def)
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lemma abs_lcm_int [simp]: "abs (lcm i j::int) = lcm i j"
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by(simp add:lcm_int_def)
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lemma lcm_abs1_int[simp]: "lcm (abs x) (y::int) = lcm x y"
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by (metis abs_idempotent lcm_int_def)
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lemma lcm_abs2_int[simp]: "lcm x (abs y::int) = lcm x y"
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by (metis abs_idempotent lcm_int_def)
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lemma lcm_cases_int:
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  fixes x :: int and y
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  assumes "x >= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> P (lcm x y)"
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      and "x >= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> P (lcm x (-y))"
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      and "x <= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> P (lcm (-x) y)"
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      and "x <= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> P (lcm (-x) (-y))"
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  shows "P (lcm x y)"
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by (insert prems, auto simp add: lcm_neg1_int lcm_neg2_int, arith)
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lemma lcm_ge_0_int [simp]: "lcm (x::int) y >= 0"
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  by (simp add: lcm_int_def)
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(* was gcd_0, etc. *)
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lemma gcd_0_nat [simp]: "gcd (x::nat) 0 = x"
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  by simp
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(* was igcd_0, etc. *)
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lemma gcd_0_int [simp]: "gcd (x::int) 0 = abs x"
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  by (unfold gcd_int_def, auto)
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lemma gcd_0_left_nat [simp]: "gcd 0 (x::nat) = x"
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  by simp
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lemma gcd_0_left_int [simp]: "gcd 0 (x::int) = abs x"
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  by (unfold gcd_int_def, auto)
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lemma gcd_red_nat: "gcd (x::nat) y = gcd y (x mod y)"
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  by (case_tac "y = 0", auto)
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(* weaker, but useful for the simplifier *)
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lemma gcd_non_0_nat: "y ~= (0::nat) \<Longrightarrow> gcd (x::nat) y = gcd y (x mod y)"
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  by simp
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lemma gcd_1_nat [simp]: "gcd (m::nat) 1 = 1"
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  by simp
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lemma gcd_Suc_0 [simp]: "gcd (m::nat) (Suc 0) = Suc 0"
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  by (simp add: One_nat_def)
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lemma gcd_1_int [simp]: "gcd (m::int) 1 = 1"
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  by (simp add: gcd_int_def)
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lemma gcd_idem_nat: "gcd (x::nat) x = x"
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by simp
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lemma gcd_idem_int: "gcd (x::int) x = abs x"
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by (auto simp add: gcd_int_def)
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declare gcd_nat.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_nat [iff]: "(gcd (m::nat)) n dvd m"
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  and gcd_dvd2_nat [iff]: "(gcd m n) dvd n"
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  apply (induct m n rule: gcd_nat_induct)
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  apply (simp_all add: gcd_non_0_nat)
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  apply (blast dest: dvd_mod_imp_dvd)
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done
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lemma gcd_dvd1_int [iff]: "gcd (x::int) y dvd x"
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by (metis gcd_int_def int_dvd_iff gcd_dvd1_nat)
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lemma gcd_dvd2_int [iff]: "gcd (x::int) y dvd y"
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by (metis gcd_int_def int_dvd_iff gcd_dvd2_nat)
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lemma dvd_gcd_D1_nat: "k dvd gcd m n \<Longrightarrow> (k::nat) dvd m"
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by(metis gcd_dvd1_nat dvd_trans)
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lemma dvd_gcd_D2_nat: "k dvd gcd m n \<Longrightarrow> (k::nat) dvd n"
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by(metis gcd_dvd2_nat dvd_trans)
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lemma dvd_gcd_D1_int: "i dvd gcd m n \<Longrightarrow> (i::int) dvd m"
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by(metis gcd_dvd1_int dvd_trans)
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lemma dvd_gcd_D2_int: "i dvd gcd m n \<Longrightarrow> (i::int) dvd n"
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by(metis gcd_dvd2_int dvd_trans)
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lemma gcd_le1_nat [simp]: "a \<noteq> 0 \<Longrightarrow> gcd (a::nat) b \<le> a"
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  by (rule dvd_imp_le, auto)
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lemma gcd_le2_nat [simp]: "b \<noteq> 0 \<Longrightarrow> gcd (a::nat) b \<le> b"
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  by (rule dvd_imp_le, auto)
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lemma gcd_le1_int [simp]: "a > 0 \<Longrightarrow> gcd (a::int) b \<le> a"
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  by (rule zdvd_imp_le, auto)
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lemma gcd_le2_int [simp]: "b > 0 \<Longrightarrow> gcd (a::int) b \<le> b"
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  by (rule zdvd_imp_le, auto)
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lemma gcd_greatest_nat: "(k::nat) dvd m \<Longrightarrow> k dvd n \<Longrightarrow> k dvd gcd m n"
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by (induct m n rule: gcd_nat_induct) (simp_all add: gcd_non_0_nat dvd_mod)
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lemma gcd_greatest_int:
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  "(k::int) dvd m \<Longrightarrow> k dvd n \<Longrightarrow> k dvd gcd m n"
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  apply (subst gcd_abs_int)
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  apply (subst abs_dvd_iff [symmetric])
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  apply (rule gcd_greatest_nat [transferred])
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  apply auto
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done
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lemma gcd_greatest_iff_nat [iff]: "(k dvd gcd (m::nat) n) =
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    (k dvd m & k dvd n)"
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  by (blast intro!: gcd_greatest_nat intro: dvd_trans)
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lemma gcd_greatest_iff_int: "((k::int) dvd gcd m n) = (k dvd m & k dvd n)"
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  by (blast intro!: gcd_greatest_int intro: dvd_trans)
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lemma gcd_zero_nat [simp]: "(gcd (m::nat) n = 0) = (m = 0 & n = 0)"
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  by (simp only: dvd_0_left_iff [symmetric] gcd_greatest_iff_nat)
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lemma gcd_zero_int [simp]: "(gcd (m::int) n = 0) = (m = 0 & n = 0)"
huffman@31706
   341
  by (auto simp add: gcd_int_def)
wenzelm@21256
   342
nipkow@31952
   343
lemma gcd_pos_nat [simp]: "(gcd (m::nat) n > 0) = (m ~= 0 | n ~= 0)"
nipkow@31952
   344
  by (insert gcd_zero_nat [of m n], arith)
wenzelm@21256
   345
nipkow@31952
   346
lemma gcd_pos_int [simp]: "(gcd (m::int) n > 0) = (m ~= 0 | n ~= 0)"
nipkow@31952
   347
  by (insert gcd_zero_int [of m n], insert gcd_ge_0_int [of m n], arith)
huffman@31706
   348
nipkow@31952
   349
lemma gcd_commute_nat: "gcd (m::nat) n = gcd n m"
huffman@31706
   350
  by (rule dvd_anti_sym, auto)
haftmann@23687
   351
nipkow@31952
   352
lemma gcd_commute_int: "gcd (m::int) n = gcd n m"
nipkow@31952
   353
  by (auto simp add: gcd_int_def gcd_commute_nat)
huffman@31706
   354
nipkow@31952
   355
lemma gcd_assoc_nat: "gcd (gcd (k::nat) m) n = gcd k (gcd m n)"
huffman@31706
   356
  apply (rule dvd_anti_sym)
huffman@31706
   357
  apply (blast intro: dvd_trans)+
huffman@31706
   358
done
wenzelm@21256
   359
nipkow@31952
   360
lemma gcd_assoc_int: "gcd (gcd (k::int) m) n = gcd k (gcd m n)"
nipkow@31952
   361
  by (auto simp add: gcd_int_def gcd_assoc_nat)
huffman@31706
   362
nipkow@31952
   363
lemmas gcd_left_commute_nat =
nipkow@31952
   364
  mk_left_commute[of gcd, OF gcd_assoc_nat gcd_commute_nat]
huffman@31706
   365
nipkow@31952
   366
lemmas gcd_left_commute_int =
nipkow@31952
   367
  mk_left_commute[of gcd, OF gcd_assoc_int gcd_commute_int]
huffman@31706
   368
nipkow@31952
   369
lemmas gcd_ac_nat = gcd_assoc_nat gcd_commute_nat gcd_left_commute_nat
huffman@31706
   370
  -- {* gcd is an AC-operator *}
wenzelm@21256
   371
nipkow@31952
   372
lemmas gcd_ac_int = gcd_assoc_int gcd_commute_int gcd_left_commute_int
huffman@31706
   373
nipkow@31952
   374
lemma gcd_unique_nat: "(d::nat) dvd a \<and> d dvd b \<and>
huffman@31706
   375
    (\<forall>e. e dvd a \<and> e dvd b \<longrightarrow> e dvd d) \<longleftrightarrow> d = gcd a b"
huffman@31706
   376
  apply auto
huffman@31706
   377
  apply (rule dvd_anti_sym)
nipkow@31952
   378
  apply (erule (1) gcd_greatest_nat)
huffman@31706
   379
  apply auto
huffman@31706
   380
done
wenzelm@21256
   381
nipkow@31952
   382
lemma gcd_unique_int: "d >= 0 & (d::int) dvd a \<and> d dvd b \<and>
huffman@31706
   383
    (\<forall>e. e dvd a \<and> e dvd b \<longrightarrow> e dvd d) \<longleftrightarrow> d = gcd a b"
huffman@31706
   384
  apply (case_tac "d = 0")
huffman@31706
   385
  apply force
huffman@31706
   386
  apply (rule iffI)
huffman@31706
   387
  apply (rule zdvd_anti_sym)
huffman@31706
   388
  apply arith
nipkow@31952
   389
  apply (subst gcd_pos_int)
huffman@31706
   390
  apply clarsimp
huffman@31706
   391
  apply (drule_tac x = "d + 1" in spec)
huffman@31706
   392
  apply (frule zdvd_imp_le)
nipkow@31952
   393
  apply (auto intro: gcd_greatest_int)
huffman@31706
   394
done
huffman@30082
   395
nipkow@31798
   396
lemma gcd_proj1_if_dvd_nat [simp]: "(x::nat) dvd y \<Longrightarrow> gcd x y = x"
nipkow@31952
   397
by (metis dvd.eq_iff gcd_unique_nat)
nipkow@31798
   398
nipkow@31798
   399
lemma gcd_proj2_if_dvd_nat [simp]: "(y::nat) dvd x \<Longrightarrow> gcd x y = y"
nipkow@31952
   400
by (metis dvd.eq_iff gcd_unique_nat)
nipkow@31798
   401
nipkow@31798
   402
lemma gcd_proj1_if_dvd_int[simp]: "x dvd y \<Longrightarrow> gcd (x::int) y = abs x"
nipkow@31952
   403
by (metis abs_dvd_iff abs_eq_0 gcd_0_left_int gcd_abs_int gcd_unique_int)
nipkow@31798
   404
nipkow@31798
   405
lemma gcd_proj2_if_dvd_int[simp]: "y dvd x \<Longrightarrow> gcd (x::int) y = abs y"
nipkow@31952
   406
by (metis gcd_proj1_if_dvd_int gcd_commute_int)
nipkow@31798
   407
nipkow@31798
   408
wenzelm@21256
   409
text {*
wenzelm@21256
   410
  \medskip Multiplication laws
wenzelm@21256
   411
*}
wenzelm@21256
   412
nipkow@31952
   413
lemma gcd_mult_distrib_nat: "(k::nat) * gcd m n = gcd (k * m) (k * n)"
wenzelm@21256
   414
    -- {* \cite[page 27]{davenport92} *}
nipkow@31952
   415
  apply (induct m n rule: gcd_nat_induct)
huffman@31706
   416
  apply simp
wenzelm@21256
   417
  apply (case_tac "k = 0")
nipkow@31952
   418
  apply (simp_all add: mod_geq gcd_non_0_nat mod_mult_distrib2)
huffman@31706
   419
done
wenzelm@21256
   420
nipkow@31952
   421
lemma gcd_mult_distrib_int: "abs (k::int) * gcd m n = gcd (k * m) (k * n)"
nipkow@31952
   422
  apply (subst (1 2) gcd_abs_int)
nipkow@31813
   423
  apply (subst (1 2) abs_mult)
nipkow@31952
   424
  apply (rule gcd_mult_distrib_nat [transferred])
huffman@31706
   425
  apply auto
huffman@31706
   426
done
wenzelm@21256
   427
nipkow@31952
   428
lemma coprime_dvd_mult_nat: "coprime (k::nat) n \<Longrightarrow> k dvd m * n \<Longrightarrow> k dvd m"
nipkow@31952
   429
  apply (insert gcd_mult_distrib_nat [of m k n])
wenzelm@21256
   430
  apply simp
wenzelm@21256
   431
  apply (erule_tac t = m in ssubst)
wenzelm@21256
   432
  apply simp
wenzelm@21256
   433
  done
wenzelm@21256
   434
nipkow@31952
   435
lemma coprime_dvd_mult_int:
nipkow@31813
   436
  "coprime (k::int) n \<Longrightarrow> k dvd m * n \<Longrightarrow> k dvd m"
nipkow@31813
   437
apply (subst abs_dvd_iff [symmetric])
nipkow@31813
   438
apply (subst dvd_abs_iff [symmetric])
nipkow@31952
   439
apply (subst (asm) gcd_abs_int)
nipkow@31952
   440
apply (rule coprime_dvd_mult_nat [transferred])
nipkow@31813
   441
    prefer 4 apply assumption
nipkow@31813
   442
   apply auto
nipkow@31813
   443
apply (subst abs_mult [symmetric], auto)
huffman@31706
   444
done
huffman@31706
   445
nipkow@31952
   446
lemma coprime_dvd_mult_iff_nat: "coprime (k::nat) n \<Longrightarrow>
huffman@31706
   447
    (k dvd m * n) = (k dvd m)"
nipkow@31952
   448
  by (auto intro: coprime_dvd_mult_nat)
huffman@31706
   449
nipkow@31952
   450
lemma coprime_dvd_mult_iff_int: "coprime (k::int) n \<Longrightarrow>
huffman@31706
   451
    (k dvd m * n) = (k dvd m)"
nipkow@31952
   452
  by (auto intro: coprime_dvd_mult_int)
huffman@31706
   453
nipkow@31952
   454
lemma gcd_mult_cancel_nat: "coprime k n \<Longrightarrow> gcd ((k::nat) * m) n = gcd m n"
wenzelm@21256
   455
  apply (rule dvd_anti_sym)
nipkow@31952
   456
  apply (rule gcd_greatest_nat)
nipkow@31952
   457
  apply (rule_tac n = k in coprime_dvd_mult_nat)
nipkow@31952
   458
  apply (simp add: gcd_assoc_nat)
nipkow@31952
   459
  apply (simp add: gcd_commute_nat)
huffman@31706
   460
  apply (simp_all add: mult_commute)
huffman@31706
   461
done
wenzelm@21256
   462
nipkow@31952
   463
lemma gcd_mult_cancel_int:
nipkow@31813
   464
  "coprime (k::int) n \<Longrightarrow> gcd (k * m) n = gcd m n"
nipkow@31952
   465
apply (subst (1 2) gcd_abs_int)
nipkow@31813
   466
apply (subst abs_mult)
nipkow@31952
   467
apply (rule gcd_mult_cancel_nat [transferred], auto)
huffman@31706
   468
done
wenzelm@21256
   469
wenzelm@21256
   470
text {* \medskip Addition laws *}
wenzelm@21256
   471
nipkow@31952
   472
lemma gcd_add1_nat [simp]: "gcd ((m::nat) + n) n = gcd m n"
huffman@31706
   473
  apply (case_tac "n = 0")
nipkow@31952
   474
  apply (simp_all add: gcd_non_0_nat)
huffman@31706
   475
done
huffman@31706
   476
nipkow@31952
   477
lemma gcd_add2_nat [simp]: "gcd (m::nat) (m + n) = gcd m n"
nipkow@31952
   478
  apply (subst (1 2) gcd_commute_nat)
huffman@31706
   479
  apply (subst add_commute)
huffman@31706
   480
  apply simp
huffman@31706
   481
done
huffman@31706
   482
huffman@31706
   483
(* to do: add the other variations? *)
huffman@31706
   484
nipkow@31952
   485
lemma gcd_diff1_nat: "(m::nat) >= n \<Longrightarrow> gcd (m - n) n = gcd m n"
nipkow@31952
   486
  by (subst gcd_add1_nat [symmetric], auto)
huffman@31706
   487
nipkow@31952
   488
lemma gcd_diff2_nat: "(n::nat) >= m \<Longrightarrow> gcd (n - m) n = gcd m n"
nipkow@31952
   489
  apply (subst gcd_commute_nat)
nipkow@31952
   490
  apply (subst gcd_diff1_nat [symmetric])
huffman@31706
   491
  apply auto
nipkow@31952
   492
  apply (subst gcd_commute_nat)
nipkow@31952
   493
  apply (subst gcd_diff1_nat)
huffman@31706
   494
  apply assumption
nipkow@31952
   495
  apply (rule gcd_commute_nat)
huffman@31706
   496
done
huffman@31706
   497
nipkow@31952
   498
lemma gcd_non_0_int: "(y::int) > 0 \<Longrightarrow> gcd x y = gcd y (x mod y)"
huffman@31706
   499
  apply (frule_tac b = y and a = x in pos_mod_sign)
huffman@31706
   500
  apply (simp del: pos_mod_sign add: gcd_int_def abs_if nat_mod_distrib)
nipkow@31952
   501
  apply (auto simp add: gcd_non_0_nat nat_mod_distrib [symmetric]
huffman@31706
   502
    zmod_zminus1_eq_if)
huffman@31706
   503
  apply (frule_tac a = x in pos_mod_bound)
nipkow@31952
   504
  apply (subst (1 2) gcd_commute_nat)
nipkow@31952
   505
  apply (simp del: pos_mod_bound add: nat_diff_distrib gcd_diff2_nat
huffman@31706
   506
    nat_le_eq_zle)
huffman@31706
   507
done
wenzelm@21256
   508
nipkow@31952
   509
lemma gcd_red_int: "gcd (x::int) y = gcd y (x mod y)"
huffman@31706
   510
  apply (case_tac "y = 0")
huffman@31706
   511
  apply force
huffman@31706
   512
  apply (case_tac "y > 0")
nipkow@31952
   513
  apply (subst gcd_non_0_int, auto)
nipkow@31952
   514
  apply (insert gcd_non_0_int [of "-y" "-x"])
nipkow@31952
   515
  apply (auto simp add: gcd_neg1_int gcd_neg2_int)
huffman@31706
   516
done
huffman@31706
   517
nipkow@31952
   518
lemma gcd_add1_int [simp]: "gcd ((m::int) + n) n = gcd m n"
nipkow@31952
   519
by (metis gcd_red_int mod_add_self1 zadd_commute)
huffman@31706
   520
nipkow@31952
   521
lemma gcd_add2_int [simp]: "gcd m ((m::int) + n) = gcd m n"
nipkow@31952
   522
by (metis gcd_add1_int gcd_commute_int zadd_commute)
wenzelm@21256
   523
nipkow@31952
   524
lemma gcd_add_mult_nat: "gcd (m::nat) (k * m + n) = gcd m n"
nipkow@31952
   525
by (metis mod_mult_self3 gcd_commute_nat gcd_red_nat)
wenzelm@21256
   526
nipkow@31952
   527
lemma gcd_add_mult_int: "gcd (m::int) (k * m + n) = gcd m n"
nipkow@31952
   528
by (metis gcd_commute_int gcd_red_int mod_mult_self1 zadd_commute)
nipkow@31798
   529
wenzelm@21256
   530
huffman@31706
   531
(* to do: differences, and all variations of addition rules
huffman@31706
   532
    as simplification rules for nat and int *)
huffman@31706
   533
nipkow@31798
   534
(* FIXME remove iff *)
nipkow@31952
   535
lemma gcd_dvd_prod_nat [iff]: "gcd (m::nat) n dvd k * n"
haftmann@23687
   536
  using mult_dvd_mono [of 1] by auto
chaieb@22027
   537
huffman@31706
   538
(* to do: add the three variations of these, and for ints? *)
huffman@31706
   539
nipkow@31992
   540
lemma finite_divisors_nat[simp]:
nipkow@31992
   541
  assumes "(m::nat) ~= 0" shows "finite{d. d dvd m}"
nipkow@31734
   542
proof-
nipkow@31734
   543
  have "finite{d. d <= m}" by(blast intro: bounded_nat_set_is_finite)
nipkow@31734
   544
  from finite_subset[OF _ this] show ?thesis using assms
nipkow@31734
   545
    by(bestsimp intro!:dvd_imp_le)
nipkow@31734
   546
qed
nipkow@31734
   547
nipkow@31995
   548
lemma finite_divisors_int[simp]:
nipkow@31734
   549
  assumes "(i::int) ~= 0" shows "finite{d. d dvd i}"
nipkow@31734
   550
proof-
nipkow@31734
   551
  have "{d. abs d <= abs i} = {- abs i .. abs i}" by(auto simp:abs_if)
nipkow@31734
   552
  hence "finite{d. abs d <= abs i}" by simp
nipkow@31734
   553
  from finite_subset[OF _ this] show ?thesis using assms
nipkow@31734
   554
    by(bestsimp intro!:dvd_imp_le_int)
nipkow@31734
   555
qed
nipkow@31734
   556
nipkow@31995
   557
lemma Max_divisors_self_nat[simp]: "n\<noteq>0 \<Longrightarrow> Max{d::nat. d dvd n} = n"
nipkow@31995
   558
apply(rule antisym)
nipkow@31995
   559
 apply (fastsimp intro: Max_le_iff[THEN iffD2] simp: dvd_imp_le)
nipkow@31995
   560
apply simp
nipkow@31995
   561
done
nipkow@31995
   562
nipkow@31995
   563
lemma Max_divisors_self_int[simp]: "n\<noteq>0 \<Longrightarrow> Max{d::int. d dvd n} = abs n"
nipkow@31995
   564
apply(rule antisym)
nipkow@31995
   565
 apply(rule Max_le_iff[THEN iffD2])
nipkow@31995
   566
   apply simp
nipkow@31995
   567
  apply fastsimp
nipkow@31995
   568
 apply (metis Collect_def abs_ge_self dvd_imp_le_int mem_def zle_trans)
nipkow@31995
   569
apply simp
nipkow@31995
   570
done
nipkow@31995
   571
nipkow@31734
   572
lemma gcd_is_Max_divisors_nat:
nipkow@31734
   573
  "m ~= 0 \<Longrightarrow> n ~= 0 \<Longrightarrow> gcd (m::nat) n = (Max {d. d dvd m & d dvd n})"
nipkow@31734
   574
apply(rule Max_eqI[THEN sym])
nipkow@31995
   575
  apply (metis finite_Collect_conjI finite_divisors_nat)
nipkow@31734
   576
 apply simp
nipkow@31952
   577
 apply(metis Suc_diff_1 Suc_neq_Zero dvd_imp_le gcd_greatest_iff_nat gcd_pos_nat)
nipkow@31734
   578
apply simp
nipkow@31734
   579
done
nipkow@31734
   580
nipkow@31734
   581
lemma gcd_is_Max_divisors_int:
nipkow@31734
   582
  "m ~= 0 ==> n ~= 0 ==> gcd (m::int) n = (Max {d. d dvd m & d dvd n})"
nipkow@31734
   583
apply(rule Max_eqI[THEN sym])
nipkow@31995
   584
  apply (metis finite_Collect_conjI finite_divisors_int)
nipkow@31734
   585
 apply simp
nipkow@31952
   586
 apply (metis gcd_greatest_iff_int gcd_pos_int zdvd_imp_le)
nipkow@31734
   587
apply simp
nipkow@31734
   588
done
nipkow@31734
   589
chaieb@22027
   590
huffman@31706
   591
subsection {* Coprimality *}
huffman@31706
   592
nipkow@31952
   593
lemma div_gcd_coprime_nat:
huffman@31706
   594
  assumes nz: "(a::nat) \<noteq> 0 \<or> b \<noteq> 0"
huffman@31706
   595
  shows "coprime (a div gcd a b) (b div gcd a b)"
wenzelm@22367
   596
proof -
haftmann@27556
   597
  let ?g = "gcd a b"
chaieb@22027
   598
  let ?a' = "a div ?g"
chaieb@22027
   599
  let ?b' = "b div ?g"
haftmann@27556
   600
  let ?g' = "gcd ?a' ?b'"
chaieb@22027
   601
  have dvdg: "?g dvd a" "?g dvd b" by simp_all
chaieb@22027
   602
  have dvdg': "?g' dvd ?a'" "?g' dvd ?b'" by simp_all
wenzelm@22367
   603
  from dvdg dvdg' obtain ka kb ka' kb' where
wenzelm@22367
   604
      kab: "a = ?g * ka" "b = ?g * kb" "?a' = ?g' * ka'" "?b' = ?g' * kb'"
chaieb@22027
   605
    unfolding dvd_def by blast
huffman@31706
   606
  then have "?g * ?a' = (?g * ?g') * ka'" "?g * ?b' = (?g * ?g') * kb'"
huffman@31706
   607
    by simp_all
wenzelm@22367
   608
  then have dvdgg':"?g * ?g' dvd a" "?g* ?g' dvd b"
wenzelm@22367
   609
    by (auto simp add: dvd_mult_div_cancel [OF dvdg(1)]
wenzelm@22367
   610
      dvd_mult_div_cancel [OF dvdg(2)] dvd_def)
nipkow@31952
   611
  have "?g \<noteq> 0" using nz by (simp add: gcd_zero_nat)
huffman@31706
   612
  then have gp: "?g > 0" by arith
nipkow@31952
   613
  from gcd_greatest_nat [OF dvdgg'] have "?g * ?g' dvd ?g" .
wenzelm@22367
   614
  with dvd_mult_cancel1 [OF gp] show "?g' = 1" by simp
chaieb@22027
   615
qed
chaieb@22027
   616
nipkow@31952
   617
lemma div_gcd_coprime_int:
huffman@31706
   618
  assumes nz: "(a::int) \<noteq> 0 \<or> b \<noteq> 0"
huffman@31706
   619
  shows "coprime (a div gcd a b) (b div gcd a b)"
nipkow@31952
   620
apply (subst (1 2 3) gcd_abs_int)
nipkow@31813
   621
apply (subst (1 2) abs_div)
nipkow@31813
   622
  apply simp
nipkow@31813
   623
 apply simp
nipkow@31813
   624
apply(subst (1 2) abs_gcd_int)
nipkow@31952
   625
apply (rule div_gcd_coprime_nat [transferred])
nipkow@31952
   626
using nz apply (auto simp add: gcd_abs_int [symmetric])
huffman@31706
   627
done
huffman@31706
   628
nipkow@31952
   629
lemma coprime_nat: "coprime (a::nat) b \<longleftrightarrow> (\<forall>d. d dvd a \<and> d dvd b \<longleftrightarrow> d = 1)"
nipkow@31952
   630
  using gcd_unique_nat[of 1 a b, simplified] by auto
huffman@31706
   631
nipkow@31952
   632
lemma coprime_Suc_0_nat:
huffman@31706
   633
    "coprime (a::nat) b \<longleftrightarrow> (\<forall>d. d dvd a \<and> d dvd b \<longleftrightarrow> d = Suc 0)"
nipkow@31952
   634
  using coprime_nat by (simp add: One_nat_def)
huffman@31706
   635
nipkow@31952
   636
lemma coprime_int: "coprime (a::int) b \<longleftrightarrow>
huffman@31706
   637
    (\<forall>d. d >= 0 \<and> d dvd a \<and> d dvd b \<longleftrightarrow> d = 1)"
nipkow@31952
   638
  using gcd_unique_int [of 1 a b]
huffman@31706
   639
  apply clarsimp
huffman@31706
   640
  apply (erule subst)
huffman@31706
   641
  apply (rule iffI)
huffman@31706
   642
  apply force
huffman@31706
   643
  apply (drule_tac x = "abs e" in exI)
huffman@31706
   644
  apply (case_tac "e >= 0")
huffman@31706
   645
  apply force
huffman@31706
   646
  apply force
huffman@31706
   647
done
huffman@31706
   648
nipkow@31952
   649
lemma gcd_coprime_nat:
huffman@31706
   650
  assumes z: "gcd (a::nat) b \<noteq> 0" and a: "a = a' * gcd a b" and
huffman@31706
   651
    b: "b = b' * gcd a b"
huffman@31706
   652
  shows    "coprime a' b'"
huffman@31706
   653
huffman@31706
   654
  apply (subgoal_tac "a' = a div gcd a b")
huffman@31706
   655
  apply (erule ssubst)
huffman@31706
   656
  apply (subgoal_tac "b' = b div gcd a b")
huffman@31706
   657
  apply (erule ssubst)
nipkow@31952
   658
  apply (rule div_gcd_coprime_nat)
huffman@31706
   659
  using prems
huffman@31706
   660
  apply force
huffman@31706
   661
  apply (subst (1) b)
huffman@31706
   662
  using z apply force
huffman@31706
   663
  apply (subst (1) a)
huffman@31706
   664
  using z apply force
huffman@31706
   665
done
huffman@31706
   666
nipkow@31952
   667
lemma gcd_coprime_int:
huffman@31706
   668
  assumes z: "gcd (a::int) b \<noteq> 0" and a: "a = a' * gcd a b" and
huffman@31706
   669
    b: "b = b' * gcd a b"
huffman@31706
   670
  shows    "coprime a' b'"
huffman@31706
   671
huffman@31706
   672
  apply (subgoal_tac "a' = a div gcd a b")
huffman@31706
   673
  apply (erule ssubst)
huffman@31706
   674
  apply (subgoal_tac "b' = b div gcd a b")
huffman@31706
   675
  apply (erule ssubst)
nipkow@31952
   676
  apply (rule div_gcd_coprime_int)
huffman@31706
   677
  using prems
huffman@31706
   678
  apply force
huffman@31706
   679
  apply (subst (1) b)
huffman@31706
   680
  using z apply force
huffman@31706
   681
  apply (subst (1) a)
huffman@31706
   682
  using z apply force
huffman@31706
   683
done
huffman@31706
   684
nipkow@31952
   685
lemma coprime_mult_nat: assumes da: "coprime (d::nat) a" and db: "coprime d b"
huffman@31706
   686
    shows "coprime d (a * b)"
nipkow@31952
   687
  apply (subst gcd_commute_nat)
nipkow@31952
   688
  using da apply (subst gcd_mult_cancel_nat)
nipkow@31952
   689
  apply (subst gcd_commute_nat, assumption)
nipkow@31952
   690
  apply (subst gcd_commute_nat, rule db)
huffman@31706
   691
done
huffman@31706
   692
nipkow@31952
   693
lemma coprime_mult_int: assumes da: "coprime (d::int) a" and db: "coprime d b"
huffman@31706
   694
    shows "coprime d (a * b)"
nipkow@31952
   695
  apply (subst gcd_commute_int)
nipkow@31952
   696
  using da apply (subst gcd_mult_cancel_int)
nipkow@31952
   697
  apply (subst gcd_commute_int, assumption)
nipkow@31952
   698
  apply (subst gcd_commute_int, rule db)
huffman@31706
   699
done
huffman@31706
   700
nipkow@31952
   701
lemma coprime_lmult_nat:
huffman@31706
   702
  assumes dab: "coprime (d::nat) (a * b)" shows "coprime d a"
huffman@31706
   703
proof -
huffman@31706
   704
  have "gcd d a dvd gcd d (a * b)"
nipkow@31952
   705
    by (rule gcd_greatest_nat, auto)
huffman@31706
   706
  with dab show ?thesis
huffman@31706
   707
    by auto
huffman@31706
   708
qed
huffman@31706
   709
nipkow@31952
   710
lemma coprime_lmult_int:
nipkow@31798
   711
  assumes "coprime (d::int) (a * b)" shows "coprime d a"
huffman@31706
   712
proof -
huffman@31706
   713
  have "gcd d a dvd gcd d (a * b)"
nipkow@31952
   714
    by (rule gcd_greatest_int, auto)
nipkow@31798
   715
  with assms show ?thesis
huffman@31706
   716
    by auto
huffman@31706
   717
qed
huffman@31706
   718
nipkow@31952
   719
lemma coprime_rmult_nat:
nipkow@31798
   720
  assumes "coprime (d::nat) (a * b)" shows "coprime d b"
huffman@31706
   721
proof -
huffman@31706
   722
  have "gcd d b dvd gcd d (a * b)"
nipkow@31952
   723
    by (rule gcd_greatest_nat, auto intro: dvd_mult)
nipkow@31798
   724
  with assms show ?thesis
huffman@31706
   725
    by auto
huffman@31706
   726
qed
huffman@31706
   727
nipkow@31952
   728
lemma coprime_rmult_int:
huffman@31706
   729
  assumes dab: "coprime (d::int) (a * b)" shows "coprime d b"
huffman@31706
   730
proof -
huffman@31706
   731
  have "gcd d b dvd gcd d (a * b)"
nipkow@31952
   732
    by (rule gcd_greatest_int, auto intro: dvd_mult)
huffman@31706
   733
  with dab show ?thesis
huffman@31706
   734
    by auto
huffman@31706
   735
qed
huffman@31706
   736
nipkow@31952
   737
lemma coprime_mul_eq_nat: "coprime (d::nat) (a * b) \<longleftrightarrow>
huffman@31706
   738
    coprime d a \<and>  coprime d b"
nipkow@31952
   739
  using coprime_rmult_nat[of d a b] coprime_lmult_nat[of d a b]
nipkow@31952
   740
    coprime_mult_nat[of d a b]
huffman@31706
   741
  by blast
huffman@31706
   742
nipkow@31952
   743
lemma coprime_mul_eq_int: "coprime (d::int) (a * b) \<longleftrightarrow>
huffman@31706
   744
    coprime d a \<and>  coprime d b"
nipkow@31952
   745
  using coprime_rmult_int[of d a b] coprime_lmult_int[of d a b]
nipkow@31952
   746
    coprime_mult_int[of d a b]
huffman@31706
   747
  by blast
huffman@31706
   748
nipkow@31952
   749
lemma gcd_coprime_exists_nat:
huffman@31706
   750
    assumes nz: "gcd (a::nat) b \<noteq> 0"
huffman@31706
   751
    shows "\<exists>a' b'. a = a' * gcd a b \<and> b = b' * gcd a b \<and> coprime a' b'"
huffman@31706
   752
  apply (rule_tac x = "a div gcd a b" in exI)
huffman@31706
   753
  apply (rule_tac x = "b div gcd a b" in exI)
nipkow@31952
   754
  using nz apply (auto simp add: div_gcd_coprime_nat dvd_div_mult)
huffman@31706
   755
done
huffman@31706
   756
nipkow@31952
   757
lemma gcd_coprime_exists_int:
huffman@31706
   758
    assumes nz: "gcd (a::int) b \<noteq> 0"
huffman@31706
   759
    shows "\<exists>a' b'. a = a' * gcd a b \<and> b = b' * gcd a b \<and> coprime a' b'"
huffman@31706
   760
  apply (rule_tac x = "a div gcd a b" in exI)
huffman@31706
   761
  apply (rule_tac x = "b div gcd a b" in exI)
nipkow@31952
   762
  using nz apply (auto simp add: div_gcd_coprime_int dvd_div_mult_self)
huffman@31706
   763
done
huffman@31706
   764
nipkow@31952
   765
lemma coprime_exp_nat: "coprime (d::nat) a \<Longrightarrow> coprime d (a^n)"
nipkow@31952
   766
  by (induct n, simp_all add: coprime_mult_nat)
huffman@31706
   767
nipkow@31952
   768
lemma coprime_exp_int: "coprime (d::int) a \<Longrightarrow> coprime d (a^n)"
nipkow@31952
   769
  by (induct n, simp_all add: coprime_mult_int)
huffman@31706
   770
nipkow@31952
   771
lemma coprime_exp2_nat [intro]: "coprime (a::nat) b \<Longrightarrow> coprime (a^n) (b^m)"
nipkow@31952
   772
  apply (rule coprime_exp_nat)
nipkow@31952
   773
  apply (subst gcd_commute_nat)
nipkow@31952
   774
  apply (rule coprime_exp_nat)
nipkow@31952
   775
  apply (subst gcd_commute_nat, assumption)
huffman@31706
   776
done
huffman@31706
   777
nipkow@31952
   778
lemma coprime_exp2_int [intro]: "coprime (a::int) b \<Longrightarrow> coprime (a^n) (b^m)"
nipkow@31952
   779
  apply (rule coprime_exp_int)
nipkow@31952
   780
  apply (subst gcd_commute_int)
nipkow@31952
   781
  apply (rule coprime_exp_int)
nipkow@31952
   782
  apply (subst gcd_commute_int, assumption)
huffman@31706
   783
done
huffman@31706
   784
nipkow@31952
   785
lemma gcd_exp_nat: "gcd ((a::nat)^n) (b^n) = (gcd a b)^n"
huffman@31706
   786
proof (cases)
huffman@31706
   787
  assume "a = 0 & b = 0"
huffman@31706
   788
  thus ?thesis by simp
huffman@31706
   789
  next assume "~(a = 0 & b = 0)"
huffman@31706
   790
  hence "coprime ((a div gcd a b)^n) ((b div gcd a b)^n)"
nipkow@31952
   791
    by (auto simp:div_gcd_coprime_nat)
huffman@31706
   792
  hence "gcd ((a div gcd a b)^n * (gcd a b)^n)
huffman@31706
   793
      ((b div gcd a b)^n * (gcd a b)^n) = (gcd a b)^n"
huffman@31706
   794
    apply (subst (1 2) mult_commute)
nipkow@31952
   795
    apply (subst gcd_mult_distrib_nat [symmetric])
huffman@31706
   796
    apply simp
huffman@31706
   797
    done
huffman@31706
   798
  also have "(a div gcd a b)^n * (gcd a b)^n = a^n"
huffman@31706
   799
    apply (subst div_power)
huffman@31706
   800
    apply auto
huffman@31706
   801
    apply (rule dvd_div_mult_self)
huffman@31706
   802
    apply (rule dvd_power_same)
huffman@31706
   803
    apply auto
huffman@31706
   804
    done
huffman@31706
   805
  also have "(b div gcd a b)^n * (gcd a b)^n = b^n"
huffman@31706
   806
    apply (subst div_power)
huffman@31706
   807
    apply auto
huffman@31706
   808
    apply (rule dvd_div_mult_self)
huffman@31706
   809
    apply (rule dvd_power_same)
huffman@31706
   810
    apply auto
huffman@31706
   811
    done
huffman@31706
   812
  finally show ?thesis .
huffman@31706
   813
qed
huffman@31706
   814
nipkow@31952
   815
lemma gcd_exp_int: "gcd ((a::int)^n) (b^n) = (gcd a b)^n"
nipkow@31952
   816
  apply (subst (1 2) gcd_abs_int)
huffman@31706
   817
  apply (subst (1 2) power_abs)
nipkow@31952
   818
  apply (rule gcd_exp_nat [where n = n, transferred])
huffman@31706
   819
  apply auto
huffman@31706
   820
done
huffman@31706
   821
nipkow@31952
   822
lemma coprime_divprod_nat: "(d::nat) dvd a * b  \<Longrightarrow> coprime d a \<Longrightarrow> d dvd b"
nipkow@31952
   823
  using coprime_dvd_mult_iff_nat[of d a b]
huffman@31706
   824
  by (auto simp add: mult_commute)
huffman@31706
   825
nipkow@31952
   826
lemma coprime_divprod_int: "(d::int) dvd a * b  \<Longrightarrow> coprime d a \<Longrightarrow> d dvd b"
nipkow@31952
   827
  using coprime_dvd_mult_iff_int[of d a b]
huffman@31706
   828
  by (auto simp add: mult_commute)
huffman@31706
   829
nipkow@31952
   830
lemma division_decomp_nat: assumes dc: "(a::nat) dvd b * c"
huffman@31706
   831
  shows "\<exists>b' c'. a = b' * c' \<and> b' dvd b \<and> c' dvd c"
huffman@31706
   832
proof-
huffman@31706
   833
  let ?g = "gcd a b"
huffman@31706
   834
  {assume "?g = 0" with dc have ?thesis by auto}
huffman@31706
   835
  moreover
huffman@31706
   836
  {assume z: "?g \<noteq> 0"
nipkow@31952
   837
    from gcd_coprime_exists_nat[OF z]
huffman@31706
   838
    obtain a' b' where ab': "a = a' * ?g" "b = b' * ?g" "coprime a' b'"
huffman@31706
   839
      by blast
huffman@31706
   840
    have thb: "?g dvd b" by auto
huffman@31706
   841
    from ab'(1) have "a' dvd a"  unfolding dvd_def by blast
huffman@31706
   842
    with dc have th0: "a' dvd b*c" using dvd_trans[of a' a "b*c"] by simp
huffman@31706
   843
    from dc ab'(1,2) have "a'*?g dvd (b'*?g) *c" by auto
huffman@31706
   844
    hence "?g*a' dvd ?g * (b' * c)" by (simp add: mult_assoc)
huffman@31706
   845
    with z have th_1: "a' dvd b' * c" by auto
nipkow@31952
   846
    from coprime_dvd_mult_nat[OF ab'(3)] th_1
huffman@31706
   847
    have thc: "a' dvd c" by (subst (asm) mult_commute, blast)
huffman@31706
   848
    from ab' have "a = ?g*a'" by algebra
huffman@31706
   849
    with thb thc have ?thesis by blast }
huffman@31706
   850
  ultimately show ?thesis by blast
huffman@31706
   851
qed
huffman@31706
   852
nipkow@31952
   853
lemma division_decomp_int: assumes dc: "(a::int) dvd b * c"
huffman@31706
   854
  shows "\<exists>b' c'. a = b' * c' \<and> b' dvd b \<and> c' dvd c"
huffman@31706
   855
proof-
huffman@31706
   856
  let ?g = "gcd a b"
huffman@31706
   857
  {assume "?g = 0" with dc have ?thesis by auto}
huffman@31706
   858
  moreover
huffman@31706
   859
  {assume z: "?g \<noteq> 0"
nipkow@31952
   860
    from gcd_coprime_exists_int[OF z]
huffman@31706
   861
    obtain a' b' where ab': "a = a' * ?g" "b = b' * ?g" "coprime a' b'"
huffman@31706
   862
      by blast
huffman@31706
   863
    have thb: "?g dvd b" by auto
huffman@31706
   864
    from ab'(1) have "a' dvd a"  unfolding dvd_def by blast
huffman@31706
   865
    with dc have th0: "a' dvd b*c"
huffman@31706
   866
      using dvd_trans[of a' a "b*c"] by simp
huffman@31706
   867
    from dc ab'(1,2) have "a'*?g dvd (b'*?g) *c" by auto
huffman@31706
   868
    hence "?g*a' dvd ?g * (b' * c)" by (simp add: mult_assoc)
huffman@31706
   869
    with z have th_1: "a' dvd b' * c" by auto
nipkow@31952
   870
    from coprime_dvd_mult_int[OF ab'(3)] th_1
huffman@31706
   871
    have thc: "a' dvd c" by (subst (asm) mult_commute, blast)
huffman@31706
   872
    from ab' have "a = ?g*a'" by algebra
huffman@31706
   873
    with thb thc have ?thesis by blast }
huffman@31706
   874
  ultimately show ?thesis by blast
chaieb@27669
   875
qed
chaieb@27669
   876
nipkow@31952
   877
lemma pow_divides_pow_nat:
huffman@31706
   878
  assumes ab: "(a::nat) ^ n dvd b ^n" and n:"n \<noteq> 0"
huffman@31706
   879
  shows "a dvd b"
huffman@31706
   880
proof-
huffman@31706
   881
  let ?g = "gcd a b"
huffman@31706
   882
  from n obtain m where m: "n = Suc m" by (cases n, simp_all)
huffman@31706
   883
  {assume "?g = 0" with ab n have ?thesis by auto }
huffman@31706
   884
  moreover
huffman@31706
   885
  {assume z: "?g \<noteq> 0"
huffman@31706
   886
    hence zn: "?g ^ n \<noteq> 0" using n by (simp add: neq0_conv)
nipkow@31952
   887
    from gcd_coprime_exists_nat[OF z]
huffman@31706
   888
    obtain a' b' where ab': "a = a' * ?g" "b = b' * ?g" "coprime a' b'"
huffman@31706
   889
      by blast
huffman@31706
   890
    from ab have "(a' * ?g) ^ n dvd (b' * ?g)^n"
huffman@31706
   891
      by (simp add: ab'(1,2)[symmetric])
huffman@31706
   892
    hence "?g^n*a'^n dvd ?g^n *b'^n"
huffman@31706
   893
      by (simp only: power_mult_distrib mult_commute)
huffman@31706
   894
    with zn z n have th0:"a'^n dvd b'^n" by auto
huffman@31706
   895
    have "a' dvd a'^n" by (simp add: m)
huffman@31706
   896
    with th0 have "a' dvd b'^n" using dvd_trans[of a' "a'^n" "b'^n"] by simp
huffman@31706
   897
    hence th1: "a' dvd b'^m * b'" by (simp add: m mult_commute)
nipkow@31952
   898
    from coprime_dvd_mult_nat[OF coprime_exp_nat [OF ab'(3), of m]] th1
huffman@31706
   899
    have "a' dvd b'" by (subst (asm) mult_commute, blast)
huffman@31706
   900
    hence "a'*?g dvd b'*?g" by simp
huffman@31706
   901
    with ab'(1,2)  have ?thesis by simp }
huffman@31706
   902
  ultimately show ?thesis by blast
huffman@31706
   903
qed
huffman@31706
   904
nipkow@31952
   905
lemma pow_divides_pow_int:
huffman@31706
   906
  assumes ab: "(a::int) ^ n dvd b ^n" and n:"n \<noteq> 0"
huffman@31706
   907
  shows "a dvd b"
chaieb@27669
   908
proof-
huffman@31706
   909
  let ?g = "gcd a b"
huffman@31706
   910
  from n obtain m where m: "n = Suc m" by (cases n, simp_all)
huffman@31706
   911
  {assume "?g = 0" with ab n have ?thesis by auto }
huffman@31706
   912
  moreover
huffman@31706
   913
  {assume z: "?g \<noteq> 0"
huffman@31706
   914
    hence zn: "?g ^ n \<noteq> 0" using n by (simp add: neq0_conv)
nipkow@31952
   915
    from gcd_coprime_exists_int[OF z]
huffman@31706
   916
    obtain a' b' where ab': "a = a' * ?g" "b = b' * ?g" "coprime a' b'"
huffman@31706
   917
      by blast
huffman@31706
   918
    from ab have "(a' * ?g) ^ n dvd (b' * ?g)^n"
huffman@31706
   919
      by (simp add: ab'(1,2)[symmetric])
huffman@31706
   920
    hence "?g^n*a'^n dvd ?g^n *b'^n"
huffman@31706
   921
      by (simp only: power_mult_distrib mult_commute)
huffman@31706
   922
    with zn z n have th0:"a'^n dvd b'^n" by auto
huffman@31706
   923
    have "a' dvd a'^n" by (simp add: m)
huffman@31706
   924
    with th0 have "a' dvd b'^n"
huffman@31706
   925
      using dvd_trans[of a' "a'^n" "b'^n"] by simp
huffman@31706
   926
    hence th1: "a' dvd b'^m * b'" by (simp add: m mult_commute)
nipkow@31952
   927
    from coprime_dvd_mult_int[OF coprime_exp_int [OF ab'(3), of m]] th1
huffman@31706
   928
    have "a' dvd b'" by (subst (asm) mult_commute, blast)
huffman@31706
   929
    hence "a'*?g dvd b'*?g" by simp
huffman@31706
   930
    with ab'(1,2)  have ?thesis by simp }
huffman@31706
   931
  ultimately show ?thesis by blast
huffman@31706
   932
qed
huffman@31706
   933
nipkow@31798
   934
(* FIXME move to Divides(?) *)
nipkow@31952
   935
lemma pow_divides_eq_nat [simp]: "n ~= 0 \<Longrightarrow> ((a::nat)^n dvd b^n) = (a dvd b)"
nipkow@31952
   936
  by (auto intro: pow_divides_pow_nat dvd_power_same)
huffman@31706
   937
nipkow@31952
   938
lemma pow_divides_eq_int [simp]: "n ~= 0 \<Longrightarrow> ((a::int)^n dvd b^n) = (a dvd b)"
nipkow@31952
   939
  by (auto intro: pow_divides_pow_int dvd_power_same)
huffman@31706
   940
nipkow@31952
   941
lemma divides_mult_nat:
huffman@31706
   942
  assumes mr: "(m::nat) dvd r" and nr: "n dvd r" and mn:"coprime m n"
huffman@31706
   943
  shows "m * n dvd r"
huffman@31706
   944
proof-
huffman@31706
   945
  from mr nr obtain m' n' where m': "r = m*m'" and n': "r = n*n'"
huffman@31706
   946
    unfolding dvd_def by blast
huffman@31706
   947
  from mr n' have "m dvd n'*n" by (simp add: mult_commute)
nipkow@31952
   948
  hence "m dvd n'" using coprime_dvd_mult_iff_nat[OF mn] by simp
huffman@31706
   949
  then obtain k where k: "n' = m*k" unfolding dvd_def by blast
huffman@31706
   950
  from n' k show ?thesis unfolding dvd_def by auto
huffman@31706
   951
qed
huffman@31706
   952
nipkow@31952
   953
lemma divides_mult_int:
huffman@31706
   954
  assumes mr: "(m::int) dvd r" and nr: "n dvd r" and mn:"coprime m n"
huffman@31706
   955
  shows "m * n dvd r"
huffman@31706
   956
proof-
huffman@31706
   957
  from mr nr obtain m' n' where m': "r = m*m'" and n': "r = n*n'"
huffman@31706
   958
    unfolding dvd_def by blast
huffman@31706
   959
  from mr n' have "m dvd n'*n" by (simp add: mult_commute)
nipkow@31952
   960
  hence "m dvd n'" using coprime_dvd_mult_iff_int[OF mn] by simp
huffman@31706
   961
  then obtain k where k: "n' = m*k" unfolding dvd_def by blast
huffman@31706
   962
  from n' k show ?thesis unfolding dvd_def by auto
chaieb@27669
   963
qed
chaieb@27669
   964
nipkow@31952
   965
lemma coprime_plus_one_nat [simp]: "coprime ((n::nat) + 1) n"
huffman@31706
   966
  apply (subgoal_tac "gcd (n + 1) n dvd (n + 1 - n)")
huffman@31706
   967
  apply force
nipkow@31952
   968
  apply (rule dvd_diff_nat)
huffman@31706
   969
  apply auto
huffman@31706
   970
done
huffman@31706
   971
nipkow@31952
   972
lemma coprime_Suc_nat [simp]: "coprime (Suc n) n"
nipkow@31952
   973
  using coprime_plus_one_nat by (simp add: One_nat_def)
huffman@31706
   974
nipkow@31952
   975
lemma coprime_plus_one_int [simp]: "coprime ((n::int) + 1) n"
huffman@31706
   976
  apply (subgoal_tac "gcd (n + 1) n dvd (n + 1 - n)")
huffman@31706
   977
  apply force
huffman@31706
   978
  apply (rule dvd_diff)
huffman@31706
   979
  apply auto
huffman@31706
   980
done
huffman@31706
   981
nipkow@31952
   982
lemma coprime_minus_one_nat: "(n::nat) \<noteq> 0 \<Longrightarrow> coprime (n - 1) n"
nipkow@31952
   983
  using coprime_plus_one_nat [of "n - 1"]
nipkow@31952
   984
    gcd_commute_nat [of "n - 1" n] by auto
huffman@31706
   985
nipkow@31952
   986
lemma coprime_minus_one_int: "coprime ((n::int) - 1) n"
nipkow@31952
   987
  using coprime_plus_one_int [of "n - 1"]
nipkow@31952
   988
    gcd_commute_int [of "n - 1" n] by auto
huffman@31706
   989
nipkow@31952
   990
lemma setprod_coprime_nat [rule_format]:
huffman@31706
   991
    "(ALL i: A. coprime (f i) (x::nat)) --> coprime (PROD i:A. f i) x"
huffman@31706
   992
  apply (case_tac "finite A")
huffman@31706
   993
  apply (induct set: finite)
nipkow@31952
   994
  apply (auto simp add: gcd_mult_cancel_nat)
huffman@31706
   995
done
huffman@31706
   996
nipkow@31952
   997
lemma setprod_coprime_int [rule_format]:
huffman@31706
   998
    "(ALL i: A. coprime (f i) (x::int)) --> coprime (PROD i:A. f i) x"
huffman@31706
   999
  apply (case_tac "finite A")
huffman@31706
  1000
  apply (induct set: finite)
nipkow@31952
  1001
  apply (auto simp add: gcd_mult_cancel_int)
huffman@31706
  1002
done
huffman@31706
  1003
nipkow@31952
  1004
lemma prime_odd_nat: "prime (p::nat) \<Longrightarrow> p > 2 \<Longrightarrow> odd p"
huffman@31706
  1005
  unfolding prime_nat_def
huffman@31706
  1006
  apply (subst even_mult_two_ex)
huffman@31706
  1007
  apply clarify
huffman@31706
  1008
  apply (drule_tac x = 2 in spec)
huffman@31706
  1009
  apply auto
huffman@31706
  1010
done
huffman@31706
  1011
nipkow@31952
  1012
lemma prime_odd_int: "prime (p::int) \<Longrightarrow> p > 2 \<Longrightarrow> odd p"
huffman@31706
  1013
  unfolding prime_int_def
nipkow@31952
  1014
  apply (frule prime_odd_nat)
huffman@31706
  1015
  apply (auto simp add: even_nat_def)
huffman@31706
  1016
done
huffman@31706
  1017
nipkow@31952
  1018
lemma coprime_common_divisor_nat: "coprime (a::nat) b \<Longrightarrow> x dvd a \<Longrightarrow>
huffman@31706
  1019
    x dvd b \<Longrightarrow> x = 1"
huffman@31706
  1020
  apply (subgoal_tac "x dvd gcd a b")
huffman@31706
  1021
  apply simp
nipkow@31952
  1022
  apply (erule (1) gcd_greatest_nat)
huffman@31706
  1023
done
huffman@31706
  1024
nipkow@31952
  1025
lemma coprime_common_divisor_int: "coprime (a::int) b \<Longrightarrow> x dvd a \<Longrightarrow>
huffman@31706
  1026
    x dvd b \<Longrightarrow> abs x = 1"
huffman@31706
  1027
  apply (subgoal_tac "x dvd gcd a b")
huffman@31706
  1028
  apply simp
nipkow@31952
  1029
  apply (erule (1) gcd_greatest_int)
huffman@31706
  1030
done
huffman@31706
  1031
nipkow@31952
  1032
lemma coprime_divisors_nat: "(d::int) dvd a \<Longrightarrow> e dvd b \<Longrightarrow> coprime a b \<Longrightarrow>
huffman@31706
  1033
    coprime d e"
huffman@31706
  1034
  apply (auto simp add: dvd_def)
nipkow@31952
  1035
  apply (frule coprime_lmult_int)
nipkow@31952
  1036
  apply (subst gcd_commute_int)
nipkow@31952
  1037
  apply (subst (asm) (2) gcd_commute_int)
nipkow@31952
  1038
  apply (erule coprime_lmult_int)
huffman@31706
  1039
done
huffman@31706
  1040
nipkow@31952
  1041
lemma invertible_coprime_nat: "(x::nat) * y mod m = 1 \<Longrightarrow> coprime x m"
nipkow@31952
  1042
apply (metis coprime_lmult_nat gcd_1_nat gcd_commute_nat gcd_red_nat)
huffman@31706
  1043
done
huffman@31706
  1044
nipkow@31952
  1045
lemma invertible_coprime_int: "(x::int) * y mod m = 1 \<Longrightarrow> coprime x m"
nipkow@31952
  1046
apply (metis coprime_lmult_int gcd_1_int gcd_commute_int gcd_red_int)
huffman@31706
  1047
done
huffman@31706
  1048
huffman@31706
  1049
huffman@31706
  1050
subsection {* Bezout's theorem *}
huffman@31706
  1051
huffman@31706
  1052
(* Function bezw returns a pair of witnesses to Bezout's theorem --
huffman@31706
  1053
   see the theorems that follow the definition. *)
huffman@31706
  1054
fun
huffman@31706
  1055
  bezw  :: "nat \<Rightarrow> nat \<Rightarrow> int * int"
huffman@31706
  1056
where
huffman@31706
  1057
  "bezw x y =
huffman@31706
  1058
  (if y = 0 then (1, 0) else
huffman@31706
  1059
      (snd (bezw y (x mod y)),
huffman@31706
  1060
       fst (bezw y (x mod y)) - snd (bezw y (x mod y)) * int(x div y)))"
huffman@31706
  1061
huffman@31706
  1062
lemma bezw_0 [simp]: "bezw x 0 = (1, 0)" by simp
huffman@31706
  1063
huffman@31706
  1064
lemma bezw_non_0: "y > 0 \<Longrightarrow> bezw x y = (snd (bezw y (x mod y)),
huffman@31706
  1065
       fst (bezw y (x mod y)) - snd (bezw y (x mod y)) * int(x div y))"
huffman@31706
  1066
  by simp
huffman@31706
  1067
huffman@31706
  1068
declare bezw.simps [simp del]
huffman@31706
  1069
huffman@31706
  1070
lemma bezw_aux [rule_format]:
huffman@31706
  1071
    "fst (bezw x y) * int x + snd (bezw x y) * int y = int (gcd x y)"
nipkow@31952
  1072
proof (induct x y rule: gcd_nat_induct)
huffman@31706
  1073
  fix m :: nat
huffman@31706
  1074
  show "fst (bezw m 0) * int m + snd (bezw m 0) * int 0 = int (gcd m 0)"
huffman@31706
  1075
    by auto
huffman@31706
  1076
  next fix m :: nat and n
huffman@31706
  1077
    assume ngt0: "n > 0" and
huffman@31706
  1078
      ih: "fst (bezw n (m mod n)) * int n +
huffman@31706
  1079
        snd (bezw n (m mod n)) * int (m mod n) =
huffman@31706
  1080
        int (gcd n (m mod n))"
huffman@31706
  1081
    thus "fst (bezw m n) * int m + snd (bezw m n) * int n = int (gcd m n)"
nipkow@31952
  1082
      apply (simp add: bezw_non_0 gcd_non_0_nat)
huffman@31706
  1083
      apply (erule subst)
huffman@31706
  1084
      apply (simp add: ring_simps)
huffman@31706
  1085
      apply (subst mod_div_equality [of m n, symmetric])
huffman@31706
  1086
      (* applying simp here undoes the last substitution!
huffman@31706
  1087
         what is procedure cancel_div_mod? *)
huffman@31706
  1088
      apply (simp only: ring_simps zadd_int [symmetric]
huffman@31706
  1089
        zmult_int [symmetric])
huffman@31706
  1090
      done
huffman@31706
  1091
qed
huffman@31706
  1092
nipkow@31952
  1093
lemma bezout_int:
huffman@31706
  1094
  fixes x y
huffman@31706
  1095
  shows "EX u v. u * (x::int) + v * y = gcd x y"
huffman@31706
  1096
proof -
huffman@31706
  1097
  have bezout_aux: "!!x y. x \<ge> (0::int) \<Longrightarrow> y \<ge> 0 \<Longrightarrow>
huffman@31706
  1098
      EX u v. u * x + v * y = gcd x y"
huffman@31706
  1099
    apply (rule_tac x = "fst (bezw (nat x) (nat y))" in exI)
huffman@31706
  1100
    apply (rule_tac x = "snd (bezw (nat x) (nat y))" in exI)
huffman@31706
  1101
    apply (unfold gcd_int_def)
huffman@31706
  1102
    apply simp
huffman@31706
  1103
    apply (subst bezw_aux [symmetric])
huffman@31706
  1104
    apply auto
huffman@31706
  1105
    done
huffman@31706
  1106
  have "(x \<ge> 0 \<and> y \<ge> 0) | (x \<ge> 0 \<and> y \<le> 0) | (x \<le> 0 \<and> y \<ge> 0) |
huffman@31706
  1107
      (x \<le> 0 \<and> y \<le> 0)"
huffman@31706
  1108
    by auto
huffman@31706
  1109
  moreover have "x \<ge> 0 \<Longrightarrow> y \<ge> 0 \<Longrightarrow> ?thesis"
huffman@31706
  1110
    by (erule (1) bezout_aux)
huffman@31706
  1111
  moreover have "x >= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> ?thesis"
huffman@31706
  1112
    apply (insert bezout_aux [of x "-y"])
huffman@31706
  1113
    apply auto
huffman@31706
  1114
    apply (rule_tac x = u in exI)
huffman@31706
  1115
    apply (rule_tac x = "-v" in exI)
nipkow@31952
  1116
    apply (subst gcd_neg2_int [symmetric])
huffman@31706
  1117
    apply auto
huffman@31706
  1118
    done
huffman@31706
  1119
  moreover have "x <= 0 \<Longrightarrow> y >= 0 \<Longrightarrow> ?thesis"
huffman@31706
  1120
    apply (insert bezout_aux [of "-x" y])
huffman@31706
  1121
    apply auto
huffman@31706
  1122
    apply (rule_tac x = "-u" in exI)
huffman@31706
  1123
    apply (rule_tac x = v in exI)
nipkow@31952
  1124
    apply (subst gcd_neg1_int [symmetric])
huffman@31706
  1125
    apply auto
huffman@31706
  1126
    done
huffman@31706
  1127
  moreover have "x <= 0 \<Longrightarrow> y <= 0 \<Longrightarrow> ?thesis"
huffman@31706
  1128
    apply (insert bezout_aux [of "-x" "-y"])
huffman@31706
  1129
    apply auto
huffman@31706
  1130
    apply (rule_tac x = "-u" in exI)
huffman@31706
  1131
    apply (rule_tac x = "-v" in exI)
nipkow@31952
  1132
    apply (subst gcd_neg1_int [symmetric])
nipkow@31952
  1133
    apply (subst gcd_neg2_int [symmetric])
huffman@31706
  1134
    apply auto
huffman@31706
  1135
    done
huffman@31706
  1136
  ultimately show ?thesis by blast
huffman@31706
  1137
qed
huffman@31706
  1138
huffman@31706
  1139
text {* versions of Bezout for nat, by Amine Chaieb *}
huffman@31706
  1140
huffman@31706
  1141
lemma ind_euclid:
huffman@31706
  1142
  assumes c: " \<forall>a b. P (a::nat) b \<longleftrightarrow> P b a" and z: "\<forall>a. P a 0"
huffman@31706
  1143
  and add: "\<forall>a b. P a b \<longrightarrow> P a (a + b)"
chaieb@27669
  1144
  shows "P a b"
chaieb@27669
  1145
proof(induct n\<equiv>"a+b" arbitrary: a b rule: nat_less_induct)
chaieb@27669
  1146
  fix n a b
chaieb@27669
  1147
  assume H: "\<forall>m < n. \<forall>a b. m = a + b \<longrightarrow> P a b" "n = a + b"
chaieb@27669
  1148
  have "a = b \<or> a < b \<or> b < a" by arith
chaieb@27669
  1149
  moreover {assume eq: "a= b"
huffman@31706
  1150
    from add[rule_format, OF z[rule_format, of a]] have "P a b" using eq
huffman@31706
  1151
    by simp}
chaieb@27669
  1152
  moreover
chaieb@27669
  1153
  {assume lt: "a < b"
chaieb@27669
  1154
    hence "a + b - a < n \<or> a = 0"  using H(2) by arith
chaieb@27669
  1155
    moreover
chaieb@27669
  1156
    {assume "a =0" with z c have "P a b" by blast }
chaieb@27669
  1157
    moreover
chaieb@27669
  1158
    {assume ab: "a + b - a < n"
chaieb@27669
  1159
      have th0: "a + b - a = a + (b - a)" using lt by arith
chaieb@27669
  1160
      from add[rule_format, OF H(1)[rule_format, OF ab th0]]
chaieb@27669
  1161
      have "P a b" by (simp add: th0[symmetric])}
chaieb@27669
  1162
    ultimately have "P a b" by blast}
chaieb@27669
  1163
  moreover
chaieb@27669
  1164
  {assume lt: "a > b"
chaieb@27669
  1165
    hence "b + a - b < n \<or> b = 0"  using H(2) by arith
chaieb@27669
  1166
    moreover
chaieb@27669
  1167
    {assume "b =0" with z c have "P a b" by blast }
chaieb@27669
  1168
    moreover
chaieb@27669
  1169
    {assume ab: "b + a - b < n"
chaieb@27669
  1170
      have th0: "b + a - b = b + (a - b)" using lt by arith
chaieb@27669
  1171
      from add[rule_format, OF H(1)[rule_format, OF ab th0]]
chaieb@27669
  1172
      have "P b a" by (simp add: th0[symmetric])
chaieb@27669
  1173
      hence "P a b" using c by blast }
chaieb@27669
  1174
    ultimately have "P a b" by blast}
chaieb@27669
  1175
ultimately  show "P a b" by blast
chaieb@27669
  1176
qed
chaieb@27669
  1177
nipkow@31952
  1178
lemma bezout_lemma_nat:
huffman@31706
  1179
  assumes ex: "\<exists>(d::nat) x y. d dvd a \<and> d dvd b \<and>
huffman@31706
  1180
    (a * x = b * y + d \<or> b * x = a * y + d)"
huffman@31706
  1181
  shows "\<exists>d x y. d dvd a \<and> d dvd a + b \<and>
huffman@31706
  1182
    (a * x = (a + b) * y + d \<or> (a + b) * x = a * y + d)"
huffman@31706
  1183
  using ex
huffman@31706
  1184
  apply clarsimp
huffman@31706
  1185
  apply (rule_tac x="d" in exI, simp add: dvd_add)
huffman@31706
  1186
  apply (case_tac "a * x = b * y + d" , simp_all)
huffman@31706
  1187
  apply (rule_tac x="x + y" in exI)
huffman@31706
  1188
  apply (rule_tac x="y" in exI)
huffman@31706
  1189
  apply algebra
huffman@31706
  1190
  apply (rule_tac x="x" in exI)
huffman@31706
  1191
  apply (rule_tac x="x + y" in exI)
huffman@31706
  1192
  apply algebra
chaieb@27669
  1193
done
chaieb@27669
  1194
nipkow@31952
  1195
lemma bezout_add_nat: "\<exists>(d::nat) x y. d dvd a \<and> d dvd b \<and>
huffman@31706
  1196
    (a * x = b * y + d \<or> b * x = a * y + d)"
huffman@31706
  1197
  apply(induct a b rule: ind_euclid)
huffman@31706
  1198
  apply blast
huffman@31706
  1199
  apply clarify
huffman@31706
  1200
  apply (rule_tac x="a" in exI, simp add: dvd_add)
huffman@31706
  1201
  apply clarsimp
huffman@31706
  1202
  apply (rule_tac x="d" in exI)
huffman@31706
  1203
  apply (case_tac "a * x = b * y + d", simp_all add: dvd_add)
huffman@31706
  1204
  apply (rule_tac x="x+y" in exI)
huffman@31706
  1205
  apply (rule_tac x="y" in exI)
huffman@31706
  1206
  apply algebra
huffman@31706
  1207
  apply (rule_tac x="x" in exI)
huffman@31706
  1208
  apply (rule_tac x="x+y" in exI)
huffman@31706
  1209
  apply algebra
chaieb@27669
  1210
done
chaieb@27669
  1211
nipkow@31952
  1212
lemma bezout1_nat: "\<exists>(d::nat) x y. d dvd a \<and> d dvd b \<and>
huffman@31706
  1213
    (a * x - b * y = d \<or> b * x - a * y = d)"
nipkow@31952
  1214
  using bezout_add_nat[of a b]
huffman@31706
  1215
  apply clarsimp
huffman@31706
  1216
  apply (rule_tac x="d" in exI, simp)
huffman@31706
  1217
  apply (rule_tac x="x" in exI)
huffman@31706
  1218
  apply (rule_tac x="y" in exI)
huffman@31706
  1219
  apply auto
chaieb@27669
  1220
done
chaieb@27669
  1221
nipkow@31952
  1222
lemma bezout_add_strong_nat: assumes nz: "a \<noteq> (0::nat)"
chaieb@27669
  1223
  shows "\<exists>d x y. d dvd a \<and> d dvd b \<and> a * x = b * y + d"
chaieb@27669
  1224
proof-
huffman@31706
  1225
 from nz have ap: "a > 0" by simp
nipkow@31952
  1226
 from bezout_add_nat[of a b]
huffman@31706
  1227
 have "(\<exists>d x y. d dvd a \<and> d dvd b \<and> a * x = b * y + d) \<or>
huffman@31706
  1228
   (\<exists>d x y. d dvd a \<and> d dvd b \<and> b * x = a * y + d)" by blast
chaieb@27669
  1229
 moreover
huffman@31706
  1230
    {fix d x y assume H: "d dvd a" "d dvd b" "a * x = b * y + d"
huffman@31706
  1231
     from H have ?thesis by blast }
chaieb@27669
  1232
 moreover
chaieb@27669
  1233
 {fix d x y assume H: "d dvd a" "d dvd b" "b * x = a * y + d"
chaieb@27669
  1234
   {assume b0: "b = 0" with H  have ?thesis by simp}
huffman@31706
  1235
   moreover
chaieb@27669
  1236
   {assume b: "b \<noteq> 0" hence bp: "b > 0" by simp
huffman@31706
  1237
     from b dvd_imp_le [OF H(2)] have "d < b \<or> d = b"
huffman@31706
  1238
       by auto
chaieb@27669
  1239
     moreover
chaieb@27669
  1240
     {assume db: "d=b"
chaieb@27669
  1241
       from prems have ?thesis apply simp
chaieb@27669
  1242
	 apply (rule exI[where x = b], simp)
chaieb@27669
  1243
	 apply (rule exI[where x = b])
chaieb@27669
  1244
	by (rule exI[where x = "a - 1"], simp add: diff_mult_distrib2)}
chaieb@27669
  1245
    moreover
huffman@31706
  1246
    {assume db: "d < b"
chaieb@27669
  1247
	{assume "x=0" hence ?thesis  using prems by simp }
chaieb@27669
  1248
	moreover
chaieb@27669
  1249
	{assume x0: "x \<noteq> 0" hence xp: "x > 0" by simp
chaieb@27669
  1250
	  from db have "d \<le> b - 1" by simp
chaieb@27669
  1251
	  hence "d*b \<le> b*(b - 1)" by simp
chaieb@27669
  1252
	  with xp mult_mono[of "1" "x" "d*b" "b*(b - 1)"]
chaieb@27669
  1253
	  have dble: "d*b \<le> x*b*(b - 1)" using bp by simp
huffman@31706
  1254
	  from H (3) have "d + (b - 1) * (b*x) = d + (b - 1) * (a*y + d)"
huffman@31706
  1255
            by simp
huffman@31706
  1256
	  hence "d + (b - 1) * a * y + (b - 1) * d = d + (b - 1) * b * x"
huffman@31706
  1257
	    by (simp only: mult_assoc right_distrib)
huffman@31706
  1258
	  hence "a * ((b - 1) * y) + d * (b - 1 + 1) = d + x*b*(b - 1)"
huffman@31706
  1259
            by algebra
chaieb@27669
  1260
	  hence "a * ((b - 1) * y) = d + x*b*(b - 1) - d*b" using bp by simp
huffman@31706
  1261
	  hence "a * ((b - 1) * y) = d + (x*b*(b - 1) - d*b)"
chaieb@27669
  1262
	    by (simp only: diff_add_assoc[OF dble, of d, symmetric])
chaieb@27669
  1263
	  hence "a * ((b - 1) * y) = b*(x*(b - 1) - d) + d"
chaieb@27669
  1264
	    by (simp only: diff_mult_distrib2 add_commute mult_ac)
chaieb@27669
  1265
	  hence ?thesis using H(1,2)
chaieb@27669
  1266
	    apply -
chaieb@27669
  1267
	    apply (rule exI[where x=d], simp)
chaieb@27669
  1268
	    apply (rule exI[where x="(b - 1) * y"])
chaieb@27669
  1269
	    by (rule exI[where x="x*(b - 1) - d"], simp)}
chaieb@27669
  1270
	ultimately have ?thesis by blast}
chaieb@27669
  1271
    ultimately have ?thesis by blast}
chaieb@27669
  1272
  ultimately have ?thesis by blast}
chaieb@27669
  1273
 ultimately show ?thesis by blast
chaieb@27669
  1274
qed
chaieb@27669
  1275
nipkow@31952
  1276
lemma bezout_nat: assumes a: "(a::nat) \<noteq> 0"
chaieb@27669
  1277
  shows "\<exists>x y. a * x = b * y + gcd a b"
chaieb@27669
  1278
proof-
chaieb@27669
  1279
  let ?g = "gcd a b"
nipkow@31952
  1280
  from bezout_add_strong_nat[OF a, of b]
chaieb@27669
  1281
  obtain d x y where d: "d dvd a" "d dvd b" "a * x = b * y + d" by blast
chaieb@27669
  1282
  from d(1,2) have "d dvd ?g" by simp
chaieb@27669
  1283
  then obtain k where k: "?g = d*k" unfolding dvd_def by blast
huffman@31706
  1284
  from d(3) have "a * x * k = (b * y + d) *k " by auto
chaieb@27669
  1285
  hence "a * (x * k) = b * (y*k) + ?g" by (algebra add: k)
chaieb@27669
  1286
  thus ?thesis by blast
chaieb@27669
  1287
qed
chaieb@27669
  1288
huffman@31706
  1289
huffman@31706
  1290
subsection {* LCM *}
huffman@31706
  1291
nipkow@31952
  1292
lemma lcm_altdef_int: "lcm (a::int) b = (abs a) * (abs b) div gcd a b"
huffman@31706
  1293
  by (simp add: lcm_int_def lcm_nat_def zdiv_int
huffman@31706
  1294
    zmult_int [symmetric] gcd_int_def)
huffman@31706
  1295
nipkow@31952
  1296
lemma prod_gcd_lcm_nat: "(m::nat) * n = gcd m n * lcm m n"
huffman@31706
  1297
  unfolding lcm_nat_def
nipkow@31952
  1298
  by (simp add: dvd_mult_div_cancel [OF gcd_dvd_prod_nat])
huffman@31706
  1299
nipkow@31952
  1300
lemma prod_gcd_lcm_int: "abs(m::int) * abs n = gcd m n * lcm m n"
huffman@31706
  1301
  unfolding lcm_int_def gcd_int_def
huffman@31706
  1302
  apply (subst int_mult [symmetric])
nipkow@31952
  1303
  apply (subst prod_gcd_lcm_nat [symmetric])
huffman@31706
  1304
  apply (subst nat_abs_mult_distrib [symmetric])
huffman@31706
  1305
  apply (simp, simp add: abs_mult)
huffman@31706
  1306
done
huffman@31706
  1307
nipkow@31952
  1308
lemma lcm_0_nat [simp]: "lcm (m::nat) 0 = 0"
huffman@31706
  1309
  unfolding lcm_nat_def by simp
huffman@31706
  1310
nipkow@31952
  1311
lemma lcm_0_int [simp]: "lcm (m::int) 0 = 0"
huffman@31706
  1312
  unfolding lcm_int_def by simp
huffman@31706
  1313
nipkow@31952
  1314
lemma lcm_0_left_nat [simp]: "lcm (0::nat) n = 0"
huffman@31706
  1315
  unfolding lcm_nat_def by simp
chaieb@27669
  1316
nipkow@31952
  1317
lemma lcm_0_left_int [simp]: "lcm (0::int) n = 0"
huffman@31706
  1318
  unfolding lcm_int_def by simp
huffman@31706
  1319
nipkow@31952
  1320
lemma lcm_commute_nat: "lcm (m::nat) n = lcm n m"
nipkow@31952
  1321
  unfolding lcm_nat_def by (simp add: gcd_commute_nat ring_simps)
huffman@31706
  1322
nipkow@31952
  1323
lemma lcm_commute_int: "lcm (m::int) n = lcm n m"
nipkow@31952
  1324
  unfolding lcm_int_def by (subst lcm_commute_nat, rule refl)
huffman@31706
  1325
huffman@31706
  1326
nipkow@31952
  1327
lemma lcm_pos_nat:
nipkow@31798
  1328
  "(m::nat) > 0 \<Longrightarrow> n>0 \<Longrightarrow> lcm m n > 0"
nipkow@31952
  1329
by (metis gr0I mult_is_0 prod_gcd_lcm_nat)
chaieb@27669
  1330
nipkow@31952
  1331
lemma lcm_pos_int:
nipkow@31798
  1332
  "(m::int) ~= 0 \<Longrightarrow> n ~= 0 \<Longrightarrow> lcm m n > 0"
nipkow@31952
  1333
  apply (subst lcm_abs_int)
nipkow@31952
  1334
  apply (rule lcm_pos_nat [transferred])
nipkow@31798
  1335
  apply auto
huffman@31706
  1336
done
haftmann@23687
  1337
nipkow@31952
  1338
lemma dvd_pos_nat:
haftmann@23687
  1339
  fixes n m :: nat
haftmann@23687
  1340
  assumes "n > 0" and "m dvd n"
haftmann@23687
  1341
  shows "m > 0"
haftmann@23687
  1342
using assms by (cases m) auto
haftmann@23687
  1343
nipkow@31952
  1344
lemma lcm_least_nat:
huffman@31706
  1345
  assumes "(m::nat) dvd k" and "n dvd k"
haftmann@27556
  1346
  shows "lcm m n dvd k"
haftmann@23687
  1347
proof (cases k)
haftmann@23687
  1348
  case 0 then show ?thesis by auto
haftmann@23687
  1349
next
haftmann@23687
  1350
  case (Suc _) then have pos_k: "k > 0" by auto
nipkow@31952
  1351
  from assms dvd_pos_nat [OF this] have pos_mn: "m > 0" "n > 0" by auto
nipkow@31952
  1352
  with gcd_zero_nat [of m n] have pos_gcd: "gcd m n > 0" by simp
haftmann@23687
  1353
  from assms obtain p where k_m: "k = m * p" using dvd_def by blast
haftmann@23687
  1354
  from assms obtain q where k_n: "k = n * q" using dvd_def by blast
haftmann@23687
  1355
  from pos_k k_m have pos_p: "p > 0" by auto
haftmann@23687
  1356
  from pos_k k_n have pos_q: "q > 0" by auto
haftmann@27556
  1357
  have "k * k * gcd q p = k * gcd (k * q) (k * p)"
nipkow@31952
  1358
    by (simp add: mult_ac gcd_mult_distrib_nat)
haftmann@27556
  1359
  also have "\<dots> = k * gcd (m * p * q) (n * q * p)"
haftmann@23687
  1360
    by (simp add: k_m [symmetric] k_n [symmetric])
haftmann@27556
  1361
  also have "\<dots> = k * p * q * gcd m n"
nipkow@31952
  1362
    by (simp add: mult_ac gcd_mult_distrib_nat)
haftmann@27556
  1363
  finally have "(m * p) * (n * q) * gcd q p = k * p * q * gcd m n"
haftmann@23687
  1364
    by (simp only: k_m [symmetric] k_n [symmetric])
haftmann@27556
  1365
  then have "p * q * m * n * gcd q p = p * q * k * gcd m n"
haftmann@23687
  1366
    by (simp add: mult_ac)
haftmann@27556
  1367
  with pos_p pos_q have "m * n * gcd q p = k * gcd m n"
haftmann@23687
  1368
    by simp
nipkow@31952
  1369
  with prod_gcd_lcm_nat [of m n]
haftmann@27556
  1370
  have "lcm m n * gcd q p * gcd m n = k * gcd m n"
haftmann@23687
  1371
    by (simp add: mult_ac)
huffman@31706
  1372
  with pos_gcd have "lcm m n * gcd q p = k" by auto
haftmann@23687
  1373
  then show ?thesis using dvd_def by auto
haftmann@23687
  1374
qed
haftmann@23687
  1375
nipkow@31952
  1376
lemma lcm_least_int:
nipkow@31798
  1377
  "(m::int) dvd k \<Longrightarrow> n dvd k \<Longrightarrow> lcm m n dvd k"
nipkow@31952
  1378
apply (subst lcm_abs_int)
nipkow@31798
  1379
apply (rule dvd_trans)
nipkow@31952
  1380
apply (rule lcm_least_nat [transferred, of _ "abs k" _])
nipkow@31798
  1381
apply auto
huffman@31706
  1382
done
huffman@31706
  1383
nipkow@31952
  1384
lemma lcm_dvd1_nat: "(m::nat) dvd lcm m n"
haftmann@23687
  1385
proof (cases m)
haftmann@23687
  1386
  case 0 then show ?thesis by simp
haftmann@23687
  1387
next
haftmann@23687
  1388
  case (Suc _)
haftmann@23687
  1389
  then have mpos: "m > 0" by simp
haftmann@23687
  1390
  show ?thesis
haftmann@23687
  1391
  proof (cases n)
haftmann@23687
  1392
    case 0 then show ?thesis by simp
haftmann@23687
  1393
  next
haftmann@23687
  1394
    case (Suc _)
haftmann@23687
  1395
    then have npos: "n > 0" by simp
haftmann@27556
  1396
    have "gcd m n dvd n" by simp
haftmann@27556
  1397
    then obtain k where "n = gcd m n * k" using dvd_def by auto
huffman@31706
  1398
    then have "m * n div gcd m n = m * (gcd m n * k) div gcd m n"
huffman@31706
  1399
      by (simp add: mult_ac)
nipkow@31952
  1400
    also have "\<dots> = m * k" using mpos npos gcd_zero_nat by simp
huffman@31706
  1401
    finally show ?thesis by (simp add: lcm_nat_def)
haftmann@23687
  1402
  qed
haftmann@23687
  1403
qed
haftmann@23687
  1404
nipkow@31952
  1405
lemma lcm_dvd1_int: "(m::int) dvd lcm m n"
nipkow@31952
  1406
  apply (subst lcm_abs_int)
huffman@31706
  1407
  apply (rule dvd_trans)
huffman@31706
  1408
  prefer 2
nipkow@31952
  1409
  apply (rule lcm_dvd1_nat [transferred])
huffman@31706
  1410
  apply auto
huffman@31706
  1411
done
huffman@31706
  1412
nipkow@31952
  1413
lemma lcm_dvd2_nat: "(n::nat) dvd lcm m n"
nipkow@31952
  1414
  by (subst lcm_commute_nat, rule lcm_dvd1_nat)
huffman@31706
  1415
nipkow@31952
  1416
lemma lcm_dvd2_int: "(n::int) dvd lcm m n"
nipkow@31952
  1417
  by (subst lcm_commute_int, rule lcm_dvd1_int)
huffman@31706
  1418
nipkow@31730
  1419
lemma dvd_lcm_I1_nat[simp]: "(k::nat) dvd m \<Longrightarrow> k dvd lcm m n"
nipkow@31952
  1420
by(metis lcm_dvd1_nat dvd_trans)
nipkow@31729
  1421
nipkow@31730
  1422
lemma dvd_lcm_I2_nat[simp]: "(k::nat) dvd n \<Longrightarrow> k dvd lcm m n"
nipkow@31952
  1423
by(metis lcm_dvd2_nat dvd_trans)
nipkow@31729
  1424
nipkow@31730
  1425
lemma dvd_lcm_I1_int[simp]: "(i::int) dvd m \<Longrightarrow> i dvd lcm m n"
nipkow@31952
  1426
by(metis lcm_dvd1_int dvd_trans)
nipkow@31729
  1427
nipkow@31730
  1428
lemma dvd_lcm_I2_int[simp]: "(i::int) dvd n \<Longrightarrow> i dvd lcm m n"
nipkow@31952
  1429
by(metis lcm_dvd2_int dvd_trans)
nipkow@31729
  1430
nipkow@31952
  1431
lemma lcm_unique_nat: "(a::nat) dvd d \<and> b dvd d \<and>
huffman@31706
  1432
    (\<forall>e. a dvd e \<and> b dvd e \<longrightarrow> d dvd e) \<longleftrightarrow> d = lcm a b"
nipkow@31952
  1433
  by (auto intro: dvd_anti_sym lcm_least_nat lcm_dvd1_nat lcm_dvd2_nat)
chaieb@27568
  1434
nipkow@31952
  1435
lemma lcm_unique_int: "d >= 0 \<and> (a::int) dvd d \<and> b dvd d \<and>
huffman@31706
  1436
    (\<forall>e. a dvd e \<and> b dvd e \<longrightarrow> d dvd e) \<longleftrightarrow> d = lcm a b"
nipkow@31952
  1437
  by (auto intro: dvd_anti_sym [transferred] lcm_least_int)
huffman@31706
  1438
nipkow@31798
  1439
lemma lcm_proj2_if_dvd_nat [simp]: "(x::nat) dvd y \<Longrightarrow> lcm x y = y"
huffman@31706
  1440
  apply (rule sym)
nipkow@31952
  1441
  apply (subst lcm_unique_nat [symmetric])
huffman@31706
  1442
  apply auto
huffman@31706
  1443
done
huffman@31706
  1444
nipkow@31798
  1445
lemma lcm_proj2_if_dvd_int [simp]: "(x::int) dvd y \<Longrightarrow> lcm x y = abs y"
huffman@31706
  1446
  apply (rule sym)
nipkow@31952
  1447
  apply (subst lcm_unique_int [symmetric])
huffman@31706
  1448
  apply auto
huffman@31706
  1449
done
huffman@31706
  1450
nipkow@31798
  1451
lemma lcm_proj1_if_dvd_nat [simp]: "(x::nat) dvd y \<Longrightarrow> lcm y x = y"
nipkow@31952
  1452
by (subst lcm_commute_nat, erule lcm_proj2_if_dvd_nat)
huffman@31706
  1453
nipkow@31798
  1454
lemma lcm_proj1_if_dvd_int [simp]: "(x::int) dvd y \<Longrightarrow> lcm y x = abs y"
nipkow@31952
  1455
by (subst lcm_commute_int, erule lcm_proj2_if_dvd_int)
huffman@31706
  1456
nipkow@31992
  1457
lemma lcm_proj1_iff_nat[simp]: "lcm m n = (m::nat) \<longleftrightarrow> n dvd m"
nipkow@31992
  1458
by (metis lcm_proj1_if_dvd_nat lcm_unique_nat)
nipkow@31992
  1459
nipkow@31992
  1460
lemma lcm_proj2_iff_nat[simp]: "lcm m n = (n::nat) \<longleftrightarrow> m dvd n"
nipkow@31992
  1461
by (metis lcm_proj2_if_dvd_nat lcm_unique_nat)
nipkow@31992
  1462
nipkow@31992
  1463
lemma lcm_proj1_iff_int[simp]: "lcm m n = abs(m::int) \<longleftrightarrow> n dvd m"
nipkow@31992
  1464
by (metis dvd_abs_iff lcm_proj1_if_dvd_int lcm_unique_int)
nipkow@31992
  1465
nipkow@31992
  1466
lemma lcm_proj2_iff_int[simp]: "lcm m n = abs(n::int) \<longleftrightarrow> m dvd n"
nipkow@31992
  1467
by (metis dvd_abs_iff lcm_proj2_if_dvd_int lcm_unique_int)
chaieb@27568
  1468
nipkow@31766
  1469
lemma lcm_assoc_nat: "lcm (lcm n m) (p::nat) = lcm n (lcm m p)"
nipkow@31992
  1470
by(rule lcm_unique_nat[THEN iffD1])(metis dvd.order_trans lcm_unique_nat)
nipkow@31766
  1471
nipkow@31766
  1472
lemma lcm_assoc_int: "lcm (lcm n m) (p::int) = lcm n (lcm m p)"
nipkow@31992
  1473
by(rule lcm_unique_int[THEN iffD1])(metis dvd_trans lcm_unique_int)
nipkow@31766
  1474
nipkow@31992
  1475
lemmas lcm_left_commute_nat = mk_left_commute[of lcm, OF lcm_assoc_nat lcm_commute_nat]
nipkow@31992
  1476
lemmas lcm_left_commute_int = mk_left_commute[of lcm, OF lcm_assoc_int lcm_commute_int]
nipkow@31766
  1477
nipkow@31952
  1478
lemmas lcm_ac_nat = lcm_assoc_nat lcm_commute_nat lcm_left_commute_nat
nipkow@31952
  1479
lemmas lcm_ac_int = lcm_assoc_int lcm_commute_int lcm_left_commute_int
nipkow@31766
  1480
nipkow@31992
  1481
lemma fun_left_comm_idem_gcd_nat: "fun_left_comm_idem (gcd :: nat\<Rightarrow>nat\<Rightarrow>nat)"
nipkow@31992
  1482
proof qed (auto simp add: gcd_ac_nat)
nipkow@31992
  1483
nipkow@31992
  1484
lemma fun_left_comm_idem_gcd_int: "fun_left_comm_idem (gcd :: int\<Rightarrow>int\<Rightarrow>int)"
nipkow@31992
  1485
proof qed (auto simp add: gcd_ac_int)
nipkow@31992
  1486
nipkow@31992
  1487
lemma fun_left_comm_idem_lcm_nat: "fun_left_comm_idem (lcm :: nat\<Rightarrow>nat\<Rightarrow>nat)"
nipkow@31992
  1488
proof qed (auto simp add: lcm_ac_nat)
nipkow@31992
  1489
nipkow@31992
  1490
lemma fun_left_comm_idem_lcm_int: "fun_left_comm_idem (lcm :: int\<Rightarrow>int\<Rightarrow>int)"
nipkow@31992
  1491
proof qed (auto simp add: lcm_ac_int)
nipkow@31992
  1492
haftmann@23687
  1493
nipkow@31995
  1494
(* FIXME introduce selimattice_bot/top and derive the following lemmas in there: *)
nipkow@31995
  1495
nipkow@31995
  1496
lemma lcm_0_iff_nat[simp]: "lcm (m::nat) n = 0 \<longleftrightarrow> m=0 \<or> n=0"
nipkow@31995
  1497
by (metis lcm_0_left_nat lcm_0_nat mult_is_0 prod_gcd_lcm_nat)
nipkow@31995
  1498
nipkow@31995
  1499
lemma lcm_0_iff_int[simp]: "lcm (m::int) n = 0 \<longleftrightarrow> m=0 \<or> n=0"
nipkow@31995
  1500
by (metis lcm_0_int lcm_0_left_int lcm_pos_int zless_le)
nipkow@31995
  1501
nipkow@31995
  1502
lemma lcm_1_iff_nat[simp]: "lcm (m::nat) n = 1 \<longleftrightarrow> m=1 \<and> n=1"
nipkow@31995
  1503
by (metis gcd_1_nat lcm_unique_nat nat_mult_1 prod_gcd_lcm_nat)
nipkow@31995
  1504
nipkow@31995
  1505
lemma lcm_1_iff_int[simp]: "lcm (m::int) n = 1 \<longleftrightarrow> (m=1 \<or> m = -1) \<and> (n=1 \<or> n = -1)"
nipkow@31995
  1506
by (metis abs_minus_one abs_mult_self lcm_proj1_if_dvd_int lcm_unique_int one_dvd zmult_eq_1_iff)
nipkow@31995
  1507
nipkow@31995
  1508
huffman@31706
  1509
subsection {* Primes *}
wenzelm@22367
  1510
nipkow@31992
  1511
(* FIXME Is there a better way to handle these, rather than making them elim rules? *)
chaieb@22027
  1512
nipkow@31952
  1513
lemma prime_ge_0_nat [elim]: "prime (p::nat) \<Longrightarrow> p >= 0"
huffman@31706
  1514
  by (unfold prime_nat_def, auto)
chaieb@22027
  1515
nipkow@31952
  1516
lemma prime_gt_0_nat [elim]: "prime (p::nat) \<Longrightarrow> p > 0"
huffman@31706
  1517
  by (unfold prime_nat_def, auto)
wenzelm@22367
  1518
nipkow@31952
  1519
lemma prime_ge_1_nat [elim]: "prime (p::nat) \<Longrightarrow> p >= 1"
huffman@31706
  1520
  by (unfold prime_nat_def, auto)
chaieb@22027
  1521
nipkow@31952
  1522
lemma prime_gt_1_nat [elim]: "prime (p::nat) \<Longrightarrow> p > 1"
huffman@31706
  1523
  by (unfold prime_nat_def, auto)
wenzelm@22367
  1524
nipkow@31952
  1525
lemma prime_ge_Suc_0_nat [elim]: "prime (p::nat) \<Longrightarrow> p >= Suc 0"
huffman@31706
  1526
  by (unfold prime_nat_def, auto)
wenzelm@22367
  1527
nipkow@31952
  1528
lemma prime_gt_Suc_0_nat [elim]: "prime (p::nat) \<Longrightarrow> p > Suc 0"
huffman@31706
  1529
  by (unfold prime_nat_def, auto)
huffman@31706
  1530
nipkow@31952
  1531
lemma prime_ge_2_nat [elim]: "prime (p::nat) \<Longrightarrow> p >= 2"
huffman@31706
  1532
  by (unfold prime_nat_def, auto)
huffman@31706
  1533
nipkow@31952
  1534
lemma prime_ge_0_int [elim]: "prime (p::int) \<Longrightarrow> p >= 0"
nipkow@31992
  1535
  by (unfold prime_int_def prime_nat_def) auto
wenzelm@22367
  1536
nipkow@31952
  1537
lemma prime_gt_0_int [elim]: "prime (p::int) \<Longrightarrow> p > 0"
huffman@31706
  1538
  by (unfold prime_int_def prime_nat_def, auto)
huffman@31706
  1539
nipkow@31952
  1540
lemma prime_ge_1_int [elim]: "prime (p::int) \<Longrightarrow> p >= 1"
huffman@31706
  1541
  by (unfold prime_int_def prime_nat_def, auto)
chaieb@22027
  1542
nipkow@31952
  1543
lemma prime_gt_1_int [elim]: "prime (p::int) \<Longrightarrow> p > 1"
huffman@31706
  1544
  by (unfold prime_int_def prime_nat_def, auto)
huffman@31706
  1545
nipkow@31952
  1546
lemma prime_ge_2_int [elim]: "prime (p::int) \<Longrightarrow> p >= 2"
huffman@31706
  1547
  by (unfold prime_int_def prime_nat_def, auto)
wenzelm@22367
  1548
huffman@31706
  1549
huffman@31706
  1550
lemma prime_int_altdef: "prime (p::int) = (1 < p \<and> (\<forall>m \<ge> 0. m dvd p \<longrightarrow>
huffman@31706
  1551
    m = 1 \<or> m = p))"
huffman@31706
  1552
  using prime_nat_def [transferred]
huffman@31706
  1553
    apply (case_tac "p >= 0")
nipkow@31952
  1554
    by (blast, auto simp add: prime_ge_0_int)
huffman@31706
  1555
huffman@31706
  1556
(* To do: determine primality of any numeral *)
huffman@31706
  1557
nipkow@31952
  1558
lemma zero_not_prime_nat [simp]: "~prime (0::nat)"
huffman@31706
  1559
  by (simp add: prime_nat_def)
huffman@31706
  1560
nipkow@31952
  1561
lemma zero_not_prime_int [simp]: "~prime (0::int)"
huffman@31706
  1562
  by (simp add: prime_int_def)
huffman@31706
  1563
nipkow@31952
  1564
lemma one_not_prime_nat [simp]: "~prime (1::nat)"
huffman@31706
  1565
  by (simp add: prime_nat_def)
chaieb@22027
  1566
nipkow@31952
  1567
lemma Suc_0_not_prime_nat [simp]: "~prime (Suc 0)"
huffman@31706
  1568
  by (simp add: prime_nat_def One_nat_def)
huffman@31706
  1569
nipkow@31952
  1570
lemma one_not_prime_int [simp]: "~prime (1::int)"
huffman@31706
  1571
  by (simp add: prime_int_def)
huffman@31706
  1572
nipkow@31952
  1573
lemma two_is_prime_nat [simp]: "prime (2::nat)"
huffman@31706
  1574
  apply (auto simp add: prime_nat_def)
huffman@31706
  1575
  apply (case_tac m)
huffman@31706
  1576
  apply (auto dest!: dvd_imp_le)
huffman@31706
  1577
  done
chaieb@22027
  1578
nipkow@31952
  1579
lemma two_is_prime_int [simp]: "prime (2::int)"
nipkow@31952
  1580
  by (rule two_is_prime_nat [transferred direction: nat "op <= (0::int)"])
chaieb@27568
  1581
nipkow@31952
  1582
lemma prime_imp_coprime_nat: "prime (p::nat) \<Longrightarrow> \<not> p dvd n \<Longrightarrow> coprime p n"
huffman@31706
  1583
  apply (unfold prime_nat_def)
nipkow@31952
  1584
  apply (metis gcd_dvd1_nat gcd_dvd2_nat)
huffman@31706
  1585
  done
huffman@31706
  1586
nipkow@31952
  1587
lemma prime_imp_coprime_int: "prime (p::int) \<Longrightarrow> \<not> p dvd n \<Longrightarrow> coprime p n"
huffman@31706
  1588
  apply (unfold prime_int_altdef)
nipkow@31952
  1589
  apply (metis gcd_dvd1_int gcd_dvd2_int gcd_ge_0_int)
chaieb@27568
  1590
  done
chaieb@27568
  1591
nipkow@31952
  1592
lemma prime_dvd_mult_nat: "prime (p::nat) \<Longrightarrow> p dvd m * n \<Longrightarrow> p dvd m \<or> p dvd n"
nipkow@31952
  1593
  by (blast intro: coprime_dvd_mult_nat prime_imp_coprime_nat)
huffman@31706
  1594
nipkow@31952
  1595
lemma prime_dvd_mult_int: "prime (p::int) \<Longrightarrow> p dvd m * n \<Longrightarrow> p dvd m \<or> p dvd n"
nipkow@31952
  1596
  by (blast intro: coprime_dvd_mult_int prime_imp_coprime_int)
huffman@31706
  1597
nipkow@31952
  1598
lemma prime_dvd_mult_eq_nat [simp]: "prime (p::nat) \<Longrightarrow>
huffman@31706
  1599
    p dvd m * n = (p dvd m \<or> p dvd n)"
nipkow@31952
  1600
  by (rule iffI, rule prime_dvd_mult_nat, auto)
chaieb@27568
  1601
nipkow@31952
  1602
lemma prime_dvd_mult_eq_int [simp]: "prime (p::int) \<Longrightarrow>
huffman@31706
  1603
    p dvd m * n = (p dvd m \<or> p dvd n)"
nipkow@31952
  1604
  by (rule iffI, rule prime_dvd_mult_int, auto)
chaieb@27568
  1605
nipkow@31952
  1606
lemma not_prime_eq_prod_nat: "(n::nat) > 1 \<Longrightarrow> ~ prime n \<Longrightarrow>
huffman@31706
  1607
    EX m k. n = m * k & 1 < m & m < n & 1 < k & k < n"
huffman@31706
  1608
  unfolding prime_nat_def dvd_def apply auto
nipkow@31992
  1609
  by(metis mult_commute linorder_neq_iff linorder_not_le mult_1 n_less_n_mult_m one_le_mult_iff less_imp_le_nat)
chaieb@27568
  1610
nipkow@31952
  1611
lemma not_prime_eq_prod_int: "(n::int) > 1 \<Longrightarrow> ~ prime n \<Longrightarrow>
huffman@31706
  1612
    EX m k. n = m * k & 1 < m & m < n & 1 < k & k < n"
huffman@31706
  1613
  unfolding prime_int_altdef dvd_def
huffman@31706
  1614
  apply auto
nipkow@31992
  1615
  by(metis div_mult_self1_is_id div_mult_self2_is_id int_div_less_self int_one_le_iff_zero_less zero_less_mult_pos zless_le)
chaieb@27568
  1616
nipkow@31952
  1617
lemma prime_dvd_power_nat [rule_format]: "prime (p::nat) -->
huffman@31706
  1618
    n > 0 --> (p dvd x^n --> p dvd x)"
huffman@31706
  1619
  by (induct n rule: nat_induct, auto)
chaieb@27568
  1620
nipkow@31952
  1621
lemma prime_dvd_power_int [rule_format]: "prime (p::int) -->
huffman@31706
  1622
    n > 0 --> (p dvd x^n --> p dvd x)"
huffman@31706
  1623
  apply (induct n rule: nat_induct, auto)
nipkow@31952
  1624
  apply (frule prime_ge_0_int)
huffman@31706
  1625
  apply auto
huffman@31706
  1626
done
huffman@31706
  1627
nipkow@31952
  1628
lemma prime_imp_power_coprime_nat: "prime (p::nat) \<Longrightarrow> ~ p dvd a \<Longrightarrow>
huffman@31706
  1629
    coprime a (p^m)"
nipkow@31952
  1630
  apply (rule coprime_exp_nat)
nipkow@31952
  1631
  apply (subst gcd_commute_nat)
nipkow@31952
  1632
  apply (erule (1) prime_imp_coprime_nat)
huffman@31706
  1633
done
chaieb@27568
  1634
nipkow@31952
  1635
lemma prime_imp_power_coprime_int: "prime (p::int) \<Longrightarrow> ~ p dvd a \<Longrightarrow>
huffman@31706
  1636
    coprime a (p^m)"
nipkow@31952
  1637
  apply (rule coprime_exp_int)
nipkow@31952
  1638
  apply (subst gcd_commute_int)
nipkow@31952
  1639
  apply (erule (1) prime_imp_coprime_int)
huffman@31706
  1640
done
chaieb@27568
  1641
nipkow@31952
  1642
lemma primes_coprime_nat: "prime (p::nat) \<Longrightarrow> prime q \<Longrightarrow> p \<noteq> q \<Longrightarrow> coprime p q"
nipkow@31952
  1643
  apply (rule prime_imp_coprime_nat, assumption)
huffman@31706
  1644
  apply (unfold prime_nat_def, auto)
huffman@31706
  1645
done
chaieb@27568
  1646
nipkow@31952
  1647
lemma primes_coprime_int: "prime (p::int) \<Longrightarrow> prime q \<Longrightarrow> p \<noteq> q \<Longrightarrow> coprime p q"
nipkow@31952
  1648
  apply (rule prime_imp_coprime_int, assumption)
huffman@31706
  1649
  apply (unfold prime_int_altdef, clarify)
huffman@31706
  1650
  apply (drule_tac x = q in spec)
huffman@31706
  1651
  apply (drule_tac x = p in spec)
huffman@31706
  1652
  apply auto
huffman@31706
  1653
done
chaieb@27568
  1654
nipkow@31952
  1655
lemma primes_imp_powers_coprime_nat: "prime (p::nat) \<Longrightarrow> prime q \<Longrightarrow> p ~= q \<Longrightarrow>
huffman@31706
  1656
    coprime (p^m) (q^n)"
nipkow@31952
  1657
  by (rule coprime_exp2_nat, rule primes_coprime_nat)
chaieb@27568
  1658
nipkow@31952
  1659
lemma primes_imp_powers_coprime_int: "prime (p::int) \<Longrightarrow> prime q \<Longrightarrow> p ~= q \<Longrightarrow>
huffman@31706
  1660
    coprime (p^m) (q^n)"
nipkow@31952
  1661
  by (rule coprime_exp2_int, rule primes_coprime_int)
chaieb@27568
  1662
nipkow@31952
  1663
lemma prime_factor_nat: "n \<noteq> (1::nat) \<Longrightarrow> \<exists> p. prime p \<and> p dvd n"
huffman@31706
  1664
  apply (induct n rule: nat_less_induct)
huffman@31706
  1665
  apply (case_tac "n = 0")
nipkow@31952
  1666
  using two_is_prime_nat apply blast
huffman@31706
  1667
  apply (case_tac "prime n")
huffman@31706
  1668
  apply blast
huffman@31706
  1669
  apply (subgoal_tac "n > 1")
nipkow@31952
  1670
  apply (frule (1) not_prime_eq_prod_nat)
huffman@31706
  1671
  apply (auto intro: dvd_mult dvd_mult2)
huffman@31706
  1672
done
chaieb@23244
  1673
huffman@31706
  1674
(* An Isar version:
huffman@31706
  1675
nipkow@31952
  1676
lemma prime_factor_b_nat:
huffman@31706
  1677
  fixes n :: nat
huffman@31706
  1678
  assumes "n \<noteq> 1"
huffman@31706
  1679
  shows "\<exists>p. prime p \<and> p dvd n"
nipkow@23983
  1680
huffman@31706
  1681
using `n ~= 1`
nipkow@31952
  1682
proof (induct n rule: less_induct_nat)
huffman@31706
  1683
  fix n :: nat
huffman@31706
  1684
  assume "n ~= 1" and
huffman@31706
  1685
    ih: "\<forall>m<n. m \<noteq> 1 \<longrightarrow> (\<exists>p. prime p \<and> p dvd m)"
huffman@31706
  1686
  thus "\<exists>p. prime p \<and> p dvd n"
huffman@31706
  1687
  proof -
huffman@31706
  1688
  {
huffman@31706
  1689
    assume "n = 0"
nipkow@31952
  1690
    moreover note two_is_prime_nat
huffman@31706
  1691
    ultimately have ?thesis
nipkow@31952
  1692
      by (auto simp del: two_is_prime_nat)
huffman@31706
  1693
  }
huffman@31706
  1694
  moreover
huffman@31706
  1695
  {
huffman@31706
  1696
    assume "prime n"
huffman@31706
  1697
    hence ?thesis by auto
huffman@31706
  1698
  }
huffman@31706
  1699
  moreover
huffman@31706
  1700
  {
huffman@31706
  1701
    assume "n ~= 0" and "~ prime n"
huffman@31706
  1702
    with `n ~= 1` have "n > 1" by auto
nipkow@31952
  1703
    with `~ prime n` and not_prime_eq_prod_nat obtain m k where
huffman@31706
  1704
      "n = m * k" and "1 < m" and "m < n" by blast
huffman@31706
  1705
    with ih obtain p where "prime p" and "p dvd m" by blast
huffman@31706
  1706
    with `n = m * k` have ?thesis by auto
huffman@31706
  1707
  }
huffman@31706
  1708
  ultimately show ?thesis by blast
huffman@31706
  1709
  qed
nipkow@23983
  1710
qed
nipkow@23983
  1711
huffman@31706
  1712
*)
huffman@31706
  1713
huffman@31706
  1714
text {* One property of coprimality is easier to prove via prime factors. *}
huffman@31706
  1715
nipkow@31952
  1716
lemma prime_divprod_pow_nat:
huffman@31706
  1717
  assumes p: "prime (p::nat)" and ab: "coprime a b" and pab: "p^n dvd a * b"
huffman@31706
  1718
  shows "p^n dvd a \<or> p^n dvd b"
huffman@31706
  1719
proof-
huffman@31706
  1720
  {assume "n = 0 \<or> a = 1 \<or> b = 1" with pab have ?thesis
huffman@31706
  1721
      apply (cases "n=0", simp_all)
huffman@31706
  1722
      apply (cases "a=1", simp_all) done}
huffman@31706
  1723
  moreover
huffman@31706
  1724
  {assume n: "n \<noteq> 0" and a: "a\<noteq>1" and b: "b\<noteq>1"
huffman@31706
  1725
    then obtain m where m: "n = Suc m" by (cases n, auto)
huffman@31706
  1726
    from n have "p dvd p^n" by (intro dvd_power, auto)
huffman@31706
  1727
    also note pab
huffman@31706
  1728
    finally have pab': "p dvd a * b".
nipkow@31952
  1729
    from prime_dvd_mult_nat[OF p pab']
huffman@31706
  1730
    have "p dvd a \<or> p dvd b" .
huffman@31706
  1731
    moreover
huffman@31706
  1732
    {assume pa: "p dvd a"
huffman@31706
  1733
      have pnba: "p^n dvd b*a" using pab by (simp add: mult_commute)
nipkow@31952
  1734
      from coprime_common_divisor_nat [OF ab, OF pa] p have "\<not> p dvd b" by auto
huffman@31706
  1735
      with p have "coprime b p"
nipkow@31952
  1736
        by (subst gcd_commute_nat, intro prime_imp_coprime_nat)
huffman@31706
  1737
      hence pnb: "coprime (p^n) b"
nipkow@31952
  1738
        by (subst gcd_commute_nat, rule coprime_exp_nat)
nipkow@31952
  1739
      from coprime_divprod_nat[OF pnba pnb] have ?thesis by blast }
huffman@31706
  1740
    moreover
huffman@31706
  1741
    {assume pb: "p dvd b"
huffman@31706
  1742
      have pnba: "p^n dvd b*a" using pab by (simp add: mult_commute)
nipkow@31952
  1743
      from coprime_common_divisor_nat [OF ab, of p] pb p have "\<not> p dvd a"
huffman@31706
  1744
        by auto
huffman@31706
  1745
      with p have "coprime a p"
nipkow@31952
  1746
        by (subst gcd_commute_nat, intro prime_imp_coprime_nat)
huffman@31706
  1747
      hence pna: "coprime (p^n) a"
nipkow@31952
  1748
        by (subst gcd_commute_nat, rule coprime_exp_nat)
nipkow@31952
  1749
      from coprime_divprod_nat[OF pab pna] have ?thesis by blast }
huffman@31706
  1750
    ultimately have ?thesis by blast}
huffman@31706
  1751
  ultimately show ?thesis by blast
nipkow@23983
  1752
qed
nipkow@23983
  1753
wenzelm@21256
  1754
end