src/HOL/Number_Theory/Residues.thy
author eberlm <eberlm@in.tum.de>
Thu, 04 May 2017 16:49:29 +0200
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parent 65465 067210a08a22
child 65899 ab7d8c999531
permissions -rw-r--r--
More material on totient function
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(*  Title:      HOL/Number_Theory/Residues.thy
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    Author:     Jeremy Avigad
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An algebraic treatment of residue rings, and resulting proofs of
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Euler's theorem and Wilson's theorem.
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*)
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section \<open>Residue rings\<close>
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theory Residues
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imports
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  Cong
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  "~~/src/HOL/Algebra/More_Group"
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  "~~/src/HOL/Algebra/More_Ring"
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  "~~/src/HOL/Algebra/More_Finite_Product"
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  "~~/src/HOL/Algebra/Multiplicative_Group"
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  Totient
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begin
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definition QuadRes :: "int \<Rightarrow> int \<Rightarrow> bool" where
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  "QuadRes p a = (\<exists>y. ([y^2 = a] (mod p)))"
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definition Legendre :: "int \<Rightarrow> int \<Rightarrow> int" where
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  "Legendre a p = (if ([a = 0] (mod p)) then 0
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    else if QuadRes p a then 1
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    else -1)"
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subsection \<open>A locale for residue rings\<close>
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definition residue_ring :: "int \<Rightarrow> int ring"
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where
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  "residue_ring m =
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    \<lparr>carrier = {0..m - 1},
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     monoid.mult = \<lambda>x y. (x * y) mod m,
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     one = 1,
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     zero = 0,
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     add = \<lambda>x y. (x + y) mod m\<rparr>"
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locale residues =
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  fixes m :: int and R (structure)
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  assumes m_gt_one: "m > 1"
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  defines "R \<equiv> residue_ring m"
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begin
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lemma abelian_group: "abelian_group R"
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proof -
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  have "\<exists>y\<in>{0..m - 1}. (x + y) mod m = 0" if "0 \<le> x" "x < m" for x
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  proof (cases "x = 0")
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    case True
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    with m_gt_one show ?thesis by simp
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  next
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    case False
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    then have "(x + (m - x)) mod m = 0"
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      by simp
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    with m_gt_one that show ?thesis
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      by (metis False atLeastAtMost_iff diff_ge_0_iff_ge diff_left_mono int_one_le_iff_zero_less less_le)
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  qed
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  with m_gt_one show ?thesis
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    by (fastforce simp add: R_def residue_ring_def mod_add_right_eq ac_simps  intro!: abelian_groupI)
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qed    
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lemma comm_monoid: "comm_monoid R"
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  unfolding R_def residue_ring_def
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  apply (rule comm_monoidI)
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    using m_gt_one  apply auto
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  apply (metis mod_mult_right_eq mult.assoc mult.commute)
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  apply (metis mult.commute)
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  done
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lemma cring: "cring R"
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  apply (intro cringI abelian_group comm_monoid)
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  unfolding R_def residue_ring_def
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  apply (auto simp add: comm_semiring_class.distrib mod_add_eq mod_mult_left_eq)
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  done
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end
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sublocale residues < cring
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  by (rule cring)
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context residues
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begin
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text \<open>
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  These lemmas translate back and forth between internal and
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  external concepts.
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\<close>
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lemma res_carrier_eq: "carrier R = {0..m - 1}"
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  unfolding R_def residue_ring_def by auto
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lemma res_add_eq: "x \<oplus> y = (x + y) mod m"
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  unfolding R_def residue_ring_def by auto
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lemma res_mult_eq: "x \<otimes> y = (x * y) mod m"
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  unfolding R_def residue_ring_def by auto
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lemma res_zero_eq: "\<zero> = 0"
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  unfolding R_def residue_ring_def by auto
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lemma res_one_eq: "\<one> = 1"
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  unfolding R_def residue_ring_def units_of_def by auto
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lemma res_units_eq: "Units R = {x. 0 < x \<and> x < m \<and> coprime x m}"
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  using m_gt_one
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  unfolding Units_def R_def residue_ring_def
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  apply auto
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  apply (subgoal_tac "x \<noteq> 0")
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  apply auto
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  apply (metis invertible_coprime_int)
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  apply (subst (asm) coprime_iff_invertible'_int)
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  apply (auto simp add: cong_int_def mult.commute)
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  done
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lemma res_neg_eq: "\<ominus> x = (- x) mod m"
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  using m_gt_one unfolding R_def a_inv_def m_inv_def residue_ring_def
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  apply simp
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  apply (rule the_equality)
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  apply (simp add: mod_add_right_eq)
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  apply (simp add: add.commute mod_add_right_eq)
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  apply (metis add.right_neutral minus_add_cancel mod_add_right_eq mod_pos_pos_trivial)
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  done
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lemma finite [iff]: "finite (carrier R)"
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  by (simp add: res_carrier_eq)
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lemma finite_Units [iff]: "finite (Units R)"
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  by (simp add: finite_ring_finite_units)
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text \<open>
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  The function \<open>a \<mapsto> a mod m\<close> maps the integers to the
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  residue classes. The following lemmas show that this mapping
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  respects addition and multiplication on the integers.
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\<close>
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lemma mod_in_carrier [iff]: "a mod m \<in> carrier R"
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  unfolding res_carrier_eq
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  using insert m_gt_one by auto
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lemma add_cong: "(x mod m) \<oplus> (y mod m) = (x + y) mod m"
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  unfolding R_def residue_ring_def
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  by (auto simp add: mod_simps)
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lemma mult_cong: "(x mod m) \<otimes> (y mod m) = (x * y) mod m"
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  unfolding R_def residue_ring_def
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  by (auto simp add: mod_simps)
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lemma zero_cong: "\<zero> = 0"
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  unfolding R_def residue_ring_def by auto
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lemma one_cong: "\<one> = 1 mod m"
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a98ef45122f3 misc tuning;
wenzelm
parents: 41959
diff changeset
   153
  using m_gt_one unfolding R_def residue_ring_def by auto
31719
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nipkow
parents:
diff changeset
   154
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   155
(* FIXME revise algebra library to use 1? *)
31719
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nipkow
parents:
diff changeset
   156
lemma pow_cong: "(x mod m) (^) n = x^n mod m"
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   157
  using m_gt_one
31719
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nipkow
parents:
diff changeset
   158
  apply (induct n)
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   159
  apply (auto simp add: nat_pow_def one_cong)
57512
cc97b347b301 reduced name variants for assoc and commute on plus and mult
haftmann
parents: 55352
diff changeset
   160
  apply (metis mult.commute mult_cong)
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   161
  done
31719
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nipkow
parents:
diff changeset
   162
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   163
lemma neg_cong: "\<ominus> (x mod m) = (- x) mod m"
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   164
  by (metis mod_minus_eq res_neg_eq)
31719
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nipkow
parents:
diff changeset
   165
60528
wenzelm
parents: 60527
diff changeset
   166
lemma (in residues) prod_cong: "finite A \<Longrightarrow> (\<Otimes>i\<in>A. (f i) mod m) = (\<Prod>i\<in>A. f i) mod m"
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   167
  by (induct set: finite) (auto simp: one_cong mult_cong)
31719
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nipkow
parents:
diff changeset
   168
60528
wenzelm
parents: 60527
diff changeset
   169
lemma (in residues) sum_cong: "finite A \<Longrightarrow> (\<Oplus>i\<in>A. (f i) mod m) = (\<Sum>i\<in>A. f i) mod m"
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   170
  by (induct set: finite) (auto simp: zero_cong add_cong)
31719
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nipkow
parents:
diff changeset
   171
60688
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   172
lemma mod_in_res_units [simp]:
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   173
  assumes "1 < m" and "coprime a m"
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   174
  shows "a mod m \<in> Units R"
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   175
proof (cases "a mod m = 0")
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   176
  case True with assms show ?thesis
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   177
    by (auto simp add: res_units_eq gcd_red_int [symmetric])
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   178
next
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   179
  case False
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   180
  from assms have "0 < m" by simp
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   181
  with pos_mod_sign [of m a] have "0 \<le> a mod m" .
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   182
  with False have "0 < a mod m" by simp
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   183
  with assms show ?thesis
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   184
    by (auto simp add: res_units_eq gcd_red_int [symmetric] ac_simps)
01488b559910 avoid explicit definition of the relation of associated elements in a ring -- prefer explicit normalization instead
haftmann
parents: 60528
diff changeset
   185
qed
31719
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nipkow
parents:
diff changeset
   186
60528
wenzelm
parents: 60527
diff changeset
   187
lemma res_eq_to_cong: "(a mod m) = (b mod m) \<longleftrightarrow> [a = b] (mod m)"
31719
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nipkow
parents:
diff changeset
   188
  unfolding cong_int_def by auto
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   189
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   190
60528
wenzelm
parents: 60527
diff changeset
   191
text \<open>Simplifying with these will translate a ring equation in R to a congruence.\<close>
31719
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nipkow
parents:
diff changeset
   192
lemmas res_to_cong_simps = add_cong mult_cong pow_cong one_cong
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   193
    prod_cong sum_cong neg_cong res_eq_to_cong
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   194
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   195
text \<open>Other useful facts about the residue ring.\<close>
31719
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nipkow
parents:
diff changeset
   196
lemma one_eq_neg_one: "\<one> = \<ominus> \<one> \<Longrightarrow> m = 2"
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   197
  apply (simp add: res_one_eq res_neg_eq)
57512
cc97b347b301 reduced name variants for assoc and commute on plus and mult
haftmann
parents: 55352
diff changeset
   198
  apply (metis add.commute add_diff_cancel mod_mod_trivial one_add_one uminus_add_conv_diff
60528
wenzelm
parents: 60527
diff changeset
   199
    zero_neq_one zmod_zminus1_eq_if)
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   200
  done
31719
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nipkow
parents:
diff changeset
   201
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   202
end
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   203
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   204
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   205
subsection \<open>Prime residues\<close>
31719
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nipkow
parents:
diff changeset
   206
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   207
locale residues_prime =
63534
523b488b15c9 Overhaul of prime/multiplicity/prime_factors
eberlm <eberlm@in.tum.de>
parents: 63417
diff changeset
   208
  fixes p :: nat and R (structure)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   209
  assumes p_prime [intro]: "prime p"
63534
523b488b15c9 Overhaul of prime/multiplicity/prime_factors
eberlm <eberlm@in.tum.de>
parents: 63417
diff changeset
   210
  defines "R \<equiv> residue_ring (int p)"
31719
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nipkow
parents:
diff changeset
   211
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   212
sublocale residues_prime < residues p
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   213
  unfolding R_def residues_def
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   214
  using p_prime apply auto
62348
9a5f43dac883 dropped various legacy fact bindings
haftmann
parents: 60688
diff changeset
   215
  apply (metis (full_types) of_nat_1 of_nat_less_iff prime_gt_1_nat)
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   216
  done
31719
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nipkow
parents:
diff changeset
   217
44872
a98ef45122f3 misc tuning;
wenzelm
parents: 41959
diff changeset
   218
context residues_prime
a98ef45122f3 misc tuning;
wenzelm
parents: 41959
diff changeset
   219
begin
31719
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nipkow
parents:
diff changeset
   220
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   221
lemma is_field: "field R"
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   222
proof -
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   223
  have "\<And>x. \<lbrakk>gcd x (int p) \<noteq> 1; 0 \<le> x; x < int p\<rbrakk> \<Longrightarrow> x = 0"
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   224
    by (metis dual_order.order_iff_strict gcd.commute less_le_not_le p_prime prime_imp_coprime prime_nat_int_transfer zdvd_imp_le)
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   225
  then show ?thesis
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   226
  apply (intro cring.field_intro2 cring)
44872
a98ef45122f3 misc tuning;
wenzelm
parents: 41959
diff changeset
   227
  apply (auto simp add: res_carrier_eq res_one_eq res_zero_eq res_units_eq)
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   228
    done
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   229
qed
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   230
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   231
lemma res_prime_units_eq: "Units R = {1..p - 1}"
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   232
  apply (subst res_units_eq)
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   233
  apply auto
62348
9a5f43dac883 dropped various legacy fact bindings
haftmann
parents: 60688
diff changeset
   234
  apply (subst gcd.commute)
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   235
  apply (auto simp add: p_prime prime_imp_coprime_int zdvd_not_zless)
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   236
  done
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   237
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   238
end
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   239
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   240
sublocale residues_prime < field
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   241
  by (rule is_field)
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   242
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   243
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   244
section \<open>Test cases: Euler's theorem and Wilson's theorem\<close>
31719
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nipkow
parents:
diff changeset
   245
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   246
subsection \<open>Euler's theorem\<close>
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   247
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   248
lemma (in residues) totient_eq:
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   249
  "totient (nat m) = card (Units R)"
65726
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   250
  thm R_def
55261
ad3604df6bc6 new lemmas involving phi from Lehmer AFP entry
paulson <lp15@cam.ac.uk>
parents: 55242
diff changeset
   251
proof -
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   252
  have *: "inj_on nat (Units R)"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   253
    by (rule inj_onI) (auto simp add: res_units_eq)
65726
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   254
  define m' where "m' = nat m"
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   255
  from m_gt_one have m: "m = int m'" "m' > 1" by (simp_all add: m'_def)
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   256
  from m have "x \<in> Units R \<longleftrightarrow> x \<in> int ` totatives m'" for x
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   257
    unfolding res_units_eq
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   258
    by (cases x; cases "x = m") (auto simp: totatives_def transfer_int_nat_gcd)
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   259
  hence "Units R = int ` totatives m'" by blast
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   260
  hence "totatives m' = nat ` Units R" by (simp add: image_image)
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   261
  then have "card (totatives (nat m)) = card (nat ` Units R)"
65726
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   262
    by (simp add: m'_def)
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   263
  also have "\<dots> = card (Units R)"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   264
    using * card_image [of nat "Units R"] by auto
65726
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   265
  finally show ?thesis by (simp add: totient_def)
55261
ad3604df6bc6 new lemmas involving phi from Lehmer AFP entry
paulson <lp15@cam.ac.uk>
parents: 55242
diff changeset
   266
qed
ad3604df6bc6 new lemmas involving phi from Lehmer AFP entry
paulson <lp15@cam.ac.uk>
parents: 55242
diff changeset
   267
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   268
lemma (in residues_prime) totient_eq: "totient p = p - 1"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   269
  using totient_eq by (simp add: res_prime_units_eq)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   270
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   271
lemma (in residues) euler_theorem:
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   272
  assumes "coprime a m"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   273
  shows "[a ^ totient (nat m) = 1] (mod m)"
65416
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   274
proof -
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   275
  have "a ^ totient (nat m) mod m = 1 mod m"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   276
    by (metis assms finite_Units m_gt_one mod_in_res_units one_cong totient_eq pow_cong units_power_order_eq_one)
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   277
  then show ?thesis
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   278
    using res_eq_to_cong by blast
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   279
qed
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   280
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   281
lemma euler_theorem:
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   282
  fixes a m :: nat
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   283
  assumes "coprime a m"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   284
  shows "[a ^ totient m = 1] (mod m)"
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   285
proof (cases "m = 0 | m = 1")
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   286
  case True
44872
a98ef45122f3 misc tuning;
wenzelm
parents: 41959
diff changeset
   287
  then show ?thesis by auto
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   288
next
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   289
  case False
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   290
  with assms show ?thesis
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   291
    using residues.euler_theorem [of "int m" "int a"] transfer_int_nat_cong
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   292
    by (auto simp add: residues_def transfer_int_nat_gcd(1)) force
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   293
qed
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   294
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   295
lemma fermat_theorem:
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   296
  fixes p a :: nat
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   297
  assumes "prime p" and "\<not> p dvd a"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   298
  shows "[a ^ (p - 1) = 1] (mod p)"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   299
proof -
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   300
  from assms prime_imp_coprime [of p a] have "coprime a p"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   301
    by (auto simp add: ac_simps)
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   302
  then have "[a ^ totient p = 1] (mod p)"
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   303
     by (rule euler_theorem)
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   304
  also have "totient p = p - 1"
65726
f5d64d094efe More material on totient function
eberlm <eberlm@in.tum.de>
parents: 65465
diff changeset
   305
    by (rule totient_prime) (rule assms)
65465
067210a08a22 more fundamental euler's totient function on nat rather than int;
haftmann
parents: 65416
diff changeset
   306
  finally show ?thesis .
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   307
qed
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   308
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   309
60526
fad653acf58f isabelle update_cartouches;
wenzelm
parents: 59730
diff changeset
   310
subsection \<open>Wilson's theorem\<close>
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   311
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   312
lemma (in field) inv_pair_lemma: "x \<in> Units R \<Longrightarrow> y \<in> Units R \<Longrightarrow>
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   313
    {x, inv x} \<noteq> {y, inv y} \<Longrightarrow> {x, inv x} \<inter> {y, inv y} = {}"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   314
  apply auto
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   315
  apply (metis Units_inv_inv)+
41541
1fa4725c4656 eliminated global prems;
wenzelm
parents: 36350
diff changeset
   316
  done
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   317
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   318
lemma (in residues_prime) wilson_theorem1:
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   319
  assumes a: "p > 2"
59730
b7c394c7a619 The factorial function, "fact", now has type "nat => 'a"
paulson <lp15@cam.ac.uk>
parents: 59667
diff changeset
   320
  shows "[fact (p - 1) = (-1::int)] (mod p)"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   321
proof -
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   322
  let ?Inverse_Pairs = "{{x, inv x}| x. x \<in> Units R - {\<one>, \<ominus> \<one>}}"
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   323
  have UR: "Units R = {\<one>, \<ominus> \<one>} \<union> \<Union>?Inverse_Pairs"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   324
    by auto
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   325
  have "(\<Otimes>i\<in>Units R. i) = (\<Otimes>i\<in>{\<one>, \<ominus> \<one>}. i) \<otimes> (\<Otimes>i\<in>\<Union>?Inverse_Pairs. i)"
31732
052399f580cf fixed proof
nipkow
parents: 31727
diff changeset
   326
    apply (subst UR)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   327
    apply (subst finprod_Un_disjoint)
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   328
    apply (auto intro: funcsetI)
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   329
    using inv_one apply auto[1]
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   330
    using inv_eq_neg_one_eq apply auto
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   331
    done
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   332
  also have "(\<Otimes>i\<in>{\<one>, \<ominus> \<one>}. i) = \<ominus> \<one>"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   333
    apply (subst finprod_insert)
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   334
    apply auto
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   335
    apply (frule one_eq_neg_one)
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   336
    using a apply force
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   337
    done
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   338
  also have "(\<Otimes>i\<in>(\<Union>?Inverse_Pairs). i) = (\<Otimes>A\<in>?Inverse_Pairs. (\<Otimes>y\<in>A. y))"
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   339
    apply (subst finprod_Union_disjoint)
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   340
    apply auto
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   341
    apply (metis Units_inv_inv)+
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   342
    done
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   343
  also have "\<dots> = \<one>"
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   344
    apply (rule finprod_one)
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   345
    apply auto
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   346
    apply (subst finprod_insert)
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   347
    apply auto
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   348
    apply (metis inv_eq_self)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   349
    done
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   350
  finally have "(\<Otimes>i\<in>Units R. i) = \<ominus> \<one>"
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   351
    by simp
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   352
  also have "(\<Otimes>i\<in>Units R. i) = (\<Otimes>i\<in>Units R. i mod p)"
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   353
    by (rule finprod_cong') (auto simp: res_units_eq)
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   354
  also have "\<dots> = (\<Prod>i\<in>Units R. i) mod p"
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   355
    by (rule prod_cong) auto
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   356
  also have "\<dots> = fact (p - 1) mod p"
64272
f76b6dda2e56 setprod -> prod
nipkow
parents: 63633
diff changeset
   357
    apply (simp add: fact_prod)
65066
c64d778a593a tidied some messy proofs
paulson <lp15@cam.ac.uk>
parents: 64593
diff changeset
   358
    using assms
55242
413ec965f95d Number_Theory: prime is no longer overloaded, but only for nat. Automatic coercion to int enabled.
paulson <lp15@cam.ac.uk>
parents: 55227
diff changeset
   359
    apply (subst res_prime_units_eq)
64272
f76b6dda2e56 setprod -> prod
nipkow
parents: 63633
diff changeset
   360
    apply (simp add: int_prod zmod_int prod_int_eq)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   361
    done
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   362
  finally have "fact (p - 1) mod p = \<ominus> \<one>" .
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   363
  then show ?thesis
60528
wenzelm
parents: 60527
diff changeset
   364
    by (metis of_nat_fact Divides.transfer_int_nat_functions(2)
wenzelm
parents: 60527
diff changeset
   365
      cong_int_def res_neg_eq res_one_eq)
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   366
qed
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   367
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   368
lemma wilson_theorem:
60527
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   369
  assumes "prime p"
eb431a5651fe tuned proofs;
wenzelm
parents: 60526
diff changeset
   370
  shows "[fact (p - 1) = - 1] (mod p)"
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   371
proof (cases "p = 2")
59667
651ea265d568 Removal of the file HOL/Number_Theory/Binomial!! And class field_char_0 now declared in Int.thy
paulson <lp15@cam.ac.uk>
parents: 58889
diff changeset
   372
  case True
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   373
  then show ?thesis
64272
f76b6dda2e56 setprod -> prod
nipkow
parents: 63633
diff changeset
   374
    by (simp add: cong_int_def fact_prod)
55352
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   375
next
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   376
  case False
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   377
  then show ?thesis
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   378
    using assms prime_ge_2_nat
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   379
    by (metis residues_prime.wilson_theorem1 residues_prime.intro le_eq_less_or_eq)
paulson <lp15@cam.ac.uk>
parents: 55262
diff changeset
   380
qed
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   381
65416
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   382
text {*
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   383
  This result can be transferred to the multiplicative group of
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   384
  $\mathbb{Z}/p\mathbb{Z}$ for $p$ prime. *}
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   385
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   386
lemma mod_nat_int_pow_eq:
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   387
  fixes n :: nat and p a :: int
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   388
  assumes "a \<ge> 0" "p \<ge> 0"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   389
  shows "(nat a ^ n) mod (nat p) = nat ((a ^ n) mod p)"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   390
  using assms
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   391
  by (simp add: int_one_le_iff_zero_less nat_mod_distrib order_less_imp_le nat_power_eq[symmetric])
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   392
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   393
theorem residue_prime_mult_group_has_gen :
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   394
 fixes p :: nat
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   395
 assumes prime_p : "prime p"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   396
 shows "\<exists>a \<in> {1 .. p - 1}. {1 .. p - 1} = {a^i mod p|i . i \<in> UNIV}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   397
proof -
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   398
  have "p\<ge>2" using prime_gt_1_nat[OF prime_p] by simp
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   399
  interpret R:residues_prime "p" "residue_ring p" unfolding residues_prime_def
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   400
    by (simp add: prime_p)
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   401
  have car: "carrier (residue_ring (int p)) - {\<zero>\<^bsub>residue_ring (int p)\<^esub>} =  {1 .. int p - 1}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   402
    by (auto simp add: R.zero_cong R.res_carrier_eq)
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   403
  obtain a where a:"a \<in> {1 .. int p - 1}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   404
         and a_gen:"{1 .. int p - 1} = {a(^)\<^bsub>residue_ring (int p)\<^esub>i|i::nat . i \<in> UNIV}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   405
    apply atomize_elim using field.finite_field_mult_group_has_gen[OF R.is_field]
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   406
    by (auto simp add: car[symmetric] carrier_mult_of)
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   407
  { fix x fix i :: nat assume x: "x \<in> {1 .. int p - 1}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   408
    hence "x (^)\<^bsub>residue_ring (int p)\<^esub> i = x ^ i mod (int p)" using R.pow_cong[of x i] by auto}
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   409
  note * = this
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   410
  have **:"nat ` {1 .. int p - 1} = {1 .. p - 1}" (is "?L = ?R")
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   411
  proof
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   412
    { fix n assume n: "n \<in> ?L"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   413
      then have "n \<in> ?R" using `p\<ge>2` by force
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   414
    } thus "?L \<subseteq> ?R" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   415
    { fix n assume n: "n \<in> ?R"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   416
      then have "n \<in> ?L" using `p\<ge>2` Set_Interval.transfer_nat_int_set_functions(2) by fastforce
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   417
    } thus "?R \<subseteq> ?L" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   418
  qed
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   419
  have "nat ` {a^i mod (int p) | i::nat. i \<in> UNIV} = {nat a^i mod p | i . i \<in> UNIV}" (is "?L = ?R")
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   420
  proof
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   421
    { fix x assume x: "x \<in> ?L"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   422
      then obtain i where i:"x = nat (a^i mod (int p))" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   423
      hence "x = nat a ^ i mod p" using mod_nat_int_pow_eq[of a "int p" i] a `p\<ge>2` by auto
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   424
      hence "x \<in> ?R" using i by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   425
    } thus "?L \<subseteq> ?R" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   426
    { fix x assume x: "x \<in> ?R"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   427
      then obtain i where i:"x = nat a^i mod p" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   428
      hence "x \<in> ?L" using mod_nat_int_pow_eq[of a "int p" i] a `p\<ge>2` by auto
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   429
    } thus "?R \<subseteq> ?L" by blast
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   430
  qed
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   431
  hence "{1 .. p - 1} = {nat a^i mod p | i. i \<in> UNIV}"
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   432
    using * a a_gen ** by presburger
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   433
  moreover
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   434
  have "nat a \<in> {1 .. p - 1}" using a by force
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   435
  ultimately show ?thesis ..
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   436
qed
f707dbcf11e3 more approproiate placement of theories MiscAlgebra and Multiplicate_Group
haftmann
parents: 65066
diff changeset
   437
31719
29f5b20e8ee8 Added NewNumberTheory by Jeremy Avigad
nipkow
parents:
diff changeset
   438
end