author | berghofe |
Wed, 07 Feb 2007 17:51:38 +0100 | |
changeset 22274 | ce1459004c8d |
parent 21404 | eb85850d3eb7 |
child 26289 | 9d2c375e242b |
permissions | -rw-r--r-- |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
1 |
(* Title: HOL/Quadratic_Reciprocity/EvenOdd.thy |
14981 | 2 |
ID: $Id$ |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
3 |
Authors: Jeremy Avigad, David Gray, and Adam Kramer |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
4 |
*) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
5 |
|
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
6 |
header {*Parity: Even and Odd Integers*} |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
7 |
|
18369 | 8 |
theory EvenOdd imports Int2 begin |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
9 |
|
19670 | 10 |
definition |
21404
eb85850d3eb7
more robust syntax for definition/abbreviation/notation;
wenzelm
parents:
20369
diff
changeset
|
11 |
zOdd :: "int set" where |
19670 | 12 |
"zOdd = {x. \<exists>k. x = 2 * k + 1}" |
21404
eb85850d3eb7
more robust syntax for definition/abbreviation/notation;
wenzelm
parents:
20369
diff
changeset
|
13 |
|
eb85850d3eb7
more robust syntax for definition/abbreviation/notation;
wenzelm
parents:
20369
diff
changeset
|
14 |
definition |
eb85850d3eb7
more robust syntax for definition/abbreviation/notation;
wenzelm
parents:
20369
diff
changeset
|
15 |
zEven :: "int set" where |
19670 | 16 |
"zEven = {x. \<exists>k. x = 2 * k}" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
17 |
|
19670 | 18 |
subsection {* Some useful properties about even and odd *} |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
19 |
|
18369 | 20 |
lemma zOddI [intro?]: "x = 2 * k + 1 \<Longrightarrow> x \<in> zOdd" |
21 |
and zOddE [elim?]: "x \<in> zOdd \<Longrightarrow> (!!k. x = 2 * k + 1 \<Longrightarrow> C) \<Longrightarrow> C" |
|
22 |
by (auto simp add: zOdd_def) |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
23 |
|
18369 | 24 |
lemma zEvenI [intro?]: "x = 2 * k \<Longrightarrow> x \<in> zEven" |
25 |
and zEvenE [elim?]: "x \<in> zEven \<Longrightarrow> (!!k. x = 2 * k \<Longrightarrow> C) \<Longrightarrow> C" |
|
26 |
by (auto simp add: zEven_def) |
|
27 |
||
28 |
lemma one_not_even: "~(1 \<in> zEven)" |
|
29 |
proof |
|
30 |
assume "1 \<in> zEven" |
|
31 |
then obtain k :: int where "1 = 2 * k" .. |
|
32 |
then show False by arith |
|
33 |
qed |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
34 |
|
18369 | 35 |
lemma even_odd_conj: "~(x \<in> zOdd & x \<in> zEven)" |
36 |
proof - |
|
37 |
{ |
|
38 |
fix a b |
|
39 |
assume "2 * (a::int) = 2 * (b::int) + 1" |
|
40 |
then have "2 * (a::int) - 2 * (b :: int) = 1" |
|
41 |
by arith |
|
42 |
then have "2 * (a - b) = 1" |
|
43 |
by (auto simp add: zdiff_zmult_distrib) |
|
44 |
moreover have "(2 * (a - b)):zEven" |
|
45 |
by (auto simp only: zEven_def) |
|
46 |
ultimately have False |
|
47 |
by (auto simp add: one_not_even) |
|
48 |
} |
|
49 |
then show ?thesis |
|
50 |
by (auto simp add: zOdd_def zEven_def) |
|
51 |
qed |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
52 |
|
18369 | 53 |
lemma even_odd_disj: "(x \<in> zOdd | x \<in> zEven)" |
54 |
by (simp add: zOdd_def zEven_def) arith |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
55 |
|
18369 | 56 |
lemma not_odd_impl_even: "~(x \<in> zOdd) ==> x \<in> zEven" |
57 |
using even_odd_disj by auto |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
58 |
|
18369 | 59 |
lemma odd_mult_odd_prop: "(x*y):zOdd ==> x \<in> zOdd" |
60 |
proof (rule classical) |
|
61 |
assume "\<not> ?thesis" |
|
62 |
then have "x \<in> zEven" by (rule not_odd_impl_even) |
|
63 |
then obtain a where a: "x = 2 * a" .. |
|
64 |
assume "x * y : zOdd" |
|
65 |
then obtain b where "x * y = 2 * b + 1" .. |
|
66 |
with a have "2 * a * y = 2 * b + 1" by simp |
|
67 |
then have "2 * a * y - 2 * b = 1" |
|
68 |
by arith |
|
69 |
then have "2 * (a * y - b) = 1" |
|
70 |
by (auto simp add: zdiff_zmult_distrib) |
|
71 |
moreover have "(2 * (a * y - b)):zEven" |
|
72 |
by (auto simp only: zEven_def) |
|
73 |
ultimately have False |
|
74 |
by (auto simp add: one_not_even) |
|
75 |
then show ?thesis .. |
|
76 |
qed |
|
77 |
||
78 |
lemma odd_minus_one_even: "x \<in> zOdd ==> (x - 1):zEven" |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
79 |
by (auto simp add: zOdd_def zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
80 |
|
18369 | 81 |
lemma even_div_2_prop1: "x \<in> zEven ==> (x mod 2) = 0" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
82 |
by (auto simp add: zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
83 |
|
18369 | 84 |
lemma even_div_2_prop2: "x \<in> zEven ==> (2 * (x div 2)) = x" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
85 |
by (auto simp add: zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
86 |
|
18369 | 87 |
lemma even_plus_even: "[| x \<in> zEven; y \<in> zEven |] ==> x + y \<in> zEven" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
88 |
apply (auto simp add: zEven_def) |
18369 | 89 |
apply (auto simp only: zadd_zmult_distrib2 [symmetric]) |
90 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
91 |
|
18369 | 92 |
lemma even_times_either: "x \<in> zEven ==> x * y \<in> zEven" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
93 |
by (auto simp add: zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
94 |
|
18369 | 95 |
lemma even_minus_even: "[| x \<in> zEven; y \<in> zEven |] ==> x - y \<in> zEven" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
96 |
apply (auto simp add: zEven_def) |
18369 | 97 |
apply (auto simp only: zdiff_zmult_distrib2 [symmetric]) |
98 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
99 |
|
18369 | 100 |
lemma odd_minus_odd: "[| x \<in> zOdd; y \<in> zOdd |] ==> x - y \<in> zEven" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
101 |
apply (auto simp add: zOdd_def zEven_def) |
18369 | 102 |
apply (auto simp only: zdiff_zmult_distrib2 [symmetric]) |
103 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
104 |
|
18369 | 105 |
lemma even_minus_odd: "[| x \<in> zEven; y \<in> zOdd |] ==> x - y \<in> zOdd" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
106 |
apply (auto simp add: zOdd_def zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
107 |
apply (rule_tac x = "k - ka - 1" in exI) |
18369 | 108 |
apply auto |
109 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
110 |
|
18369 | 111 |
lemma odd_minus_even: "[| x \<in> zOdd; y \<in> zEven |] ==> x - y \<in> zOdd" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
112 |
apply (auto simp add: zOdd_def zEven_def) |
18369 | 113 |
apply (auto simp only: zdiff_zmult_distrib2 [symmetric]) |
114 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
115 |
|
18369 | 116 |
lemma odd_times_odd: "[| x \<in> zOdd; y \<in> zOdd |] ==> x * y \<in> zOdd" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
117 |
apply (auto simp add: zOdd_def zadd_zmult_distrib zadd_zmult_distrib2) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
118 |
apply (rule_tac x = "2 * ka * k + ka + k" in exI) |
18369 | 119 |
apply (auto simp add: zadd_zmult_distrib) |
120 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
121 |
|
18369 | 122 |
lemma odd_iff_not_even: "(x \<in> zOdd) = (~ (x \<in> zEven))" |
123 |
using even_odd_conj even_odd_disj by auto |
|
124 |
||
125 |
lemma even_product: "x * y \<in> zEven ==> x \<in> zEven | y \<in> zEven" |
|
126 |
using odd_iff_not_even odd_times_odd by auto |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
127 |
|
18369 | 128 |
lemma even_diff: "x - y \<in> zEven = ((x \<in> zEven) = (y \<in> zEven))" |
129 |
proof |
|
130 |
assume xy: "x - y \<in> zEven" |
|
131 |
{ |
|
132 |
assume x: "x \<in> zEven" |
|
133 |
have "y \<in> zEven" |
|
134 |
proof (rule classical) |
|
135 |
assume "\<not> ?thesis" |
|
136 |
then have "y \<in> zOdd" |
|
137 |
by (simp add: odd_iff_not_even) |
|
138 |
with x have "x - y \<in> zOdd" |
|
139 |
by (simp add: even_minus_odd) |
|
140 |
with xy have False |
|
141 |
by (auto simp add: odd_iff_not_even) |
|
142 |
then show ?thesis .. |
|
143 |
qed |
|
144 |
} moreover { |
|
145 |
assume y: "y \<in> zEven" |
|
146 |
have "x \<in> zEven" |
|
147 |
proof (rule classical) |
|
148 |
assume "\<not> ?thesis" |
|
149 |
then have "x \<in> zOdd" |
|
150 |
by (auto simp add: odd_iff_not_even) |
|
151 |
with y have "x - y \<in> zOdd" |
|
152 |
by (simp add: odd_minus_even) |
|
153 |
with xy have False |
|
154 |
by (auto simp add: odd_iff_not_even) |
|
155 |
then show ?thesis .. |
|
156 |
qed |
|
157 |
} |
|
158 |
ultimately show "(x \<in> zEven) = (y \<in> zEven)" |
|
159 |
by (auto simp add: odd_iff_not_even even_minus_even odd_minus_odd |
|
160 |
even_minus_odd odd_minus_even) |
|
161 |
next |
|
162 |
assume "(x \<in> zEven) = (y \<in> zEven)" |
|
163 |
then show "x - y \<in> zEven" |
|
164 |
by (auto simp add: odd_iff_not_even even_minus_even odd_minus_odd |
|
165 |
even_minus_odd odd_minus_even) |
|
166 |
qed |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
167 |
|
18369 | 168 |
lemma neg_one_even_power: "[| x \<in> zEven; 0 \<le> x |] ==> (-1::int)^(nat x) = 1" |
169 |
proof - |
|
20369 | 170 |
assume "x \<in> zEven" and "0 \<le> x" |
171 |
from `x \<in> zEven` obtain a where "x = 2 * a" .. |
|
172 |
with `0 \<le> x` have "0 \<le> a" by simp |
|
173 |
from `0 \<le> x` and `x = 2 * a` have "nat x = nat (2 * a)" |
|
18369 | 174 |
by simp |
20369 | 175 |
also from `x = 2 * a` have "nat (2 * a) = 2 * nat a" |
18369 | 176 |
by (simp add: nat_mult_distrib) |
177 |
finally have "(-1::int)^nat x = (-1)^(2 * nat a)" |
|
178 |
by simp |
|
179 |
also have "... = ((-1::int)^2)^ (nat a)" |
|
180 |
by (simp add: zpower_zpower [symmetric]) |
|
181 |
also have "(-1::int)^2 = 1" |
|
182 |
by simp |
|
183 |
finally show ?thesis |
|
184 |
by simp |
|
185 |
qed |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
186 |
|
18369 | 187 |
lemma neg_one_odd_power: "[| x \<in> zOdd; 0 \<le> x |] ==> (-1::int)^(nat x) = -1" |
188 |
proof - |
|
20369 | 189 |
assume "x \<in> zOdd" and "0 \<le> x" |
190 |
from `x \<in> zOdd` obtain a where "x = 2 * a + 1" .. |
|
191 |
with `0 \<le> x` have a: "0 \<le> a" by simp |
|
192 |
with `0 \<le> x` and `x = 2 * a + 1` have "nat x = nat (2 * a + 1)" |
|
18369 | 193 |
by simp |
194 |
also from a have "nat (2 * a + 1) = 2 * nat a + 1" |
|
195 |
by (auto simp add: nat_mult_distrib nat_add_distrib) |
|
196 |
finally have "(-1::int)^nat x = (-1)^(2 * nat a + 1)" |
|
197 |
by simp |
|
198 |
also have "... = ((-1::int)^2)^ (nat a) * (-1)^1" |
|
199 |
by (auto simp add: zpower_zpower [symmetric] zpower_zadd_distrib) |
|
200 |
also have "(-1::int)^2 = 1" |
|
201 |
by simp |
|
202 |
finally show ?thesis |
|
203 |
by simp |
|
204 |
qed |
|
205 |
||
206 |
lemma neg_one_power_parity: "[| 0 \<le> x; 0 \<le> y; (x \<in> zEven) = (y \<in> zEven) |] ==> |
|
20369 | 207 |
(-1::int)^(nat x) = (-1::int)^(nat y)" |
18369 | 208 |
using even_odd_disj [of x] even_odd_disj [of y] |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
209 |
by (auto simp add: neg_one_even_power neg_one_odd_power) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
210 |
|
18369 | 211 |
|
212 |
lemma one_not_neg_one_mod_m: "2 < m ==> ~([1 = -1] (mod m))" |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
213 |
by (auto simp add: zcong_def zdvd_not_zless) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
214 |
|
18369 | 215 |
lemma even_div_2_l: "[| y \<in> zEven; x < y |] ==> x div 2 < y div 2" |
216 |
proof - |
|
20369 | 217 |
assume "y \<in> zEven" and "x < y" |
218 |
from `y \<in> zEven` obtain k where k: "y = 2 * k" .. |
|
219 |
with `x < y` have "x < 2 * k" by simp |
|
18369 | 220 |
then have "x div 2 < k" by (auto simp add: div_prop1) |
221 |
also have "k = (2 * k) div 2" by simp |
|
222 |
finally have "x div 2 < 2 * k div 2" by simp |
|
223 |
with k show ?thesis by simp |
|
224 |
qed |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
225 |
|
18369 | 226 |
lemma even_sum_div_2: "[| x \<in> zEven; y \<in> zEven |] ==> (x + y) div 2 = x div 2 + y div 2" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
227 |
by (auto simp add: zEven_def, auto simp add: zdiv_zadd1_eq) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
228 |
|
18369 | 229 |
lemma even_prod_div_2: "[| x \<in> zEven |] ==> (x * y) div 2 = (x div 2) * y" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
230 |
by (auto simp add: zEven_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
231 |
|
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
232 |
(* An odd prime is greater than 2 *) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
233 |
|
18369 | 234 |
lemma zprime_zOdd_eq_grt_2: "zprime p ==> (p \<in> zOdd) = (2 < p)" |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
235 |
apply (auto simp add: zOdd_def zprime_def) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
236 |
apply (drule_tac x = 2 in allE) |
18369 | 237 |
using odd_iff_not_even [of p] |
238 |
apply (auto simp add: zOdd_def zEven_def) |
|
239 |
done |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
240 |
|
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
241 |
(* Powers of -1 and parity *) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
242 |
|
18369 | 243 |
lemma neg_one_special: "finite A ==> |
244 |
((-1 :: int) ^ card A) * (-1 ^ card A) = 1" |
|
22274 | 245 |
by (induct set: finite) auto |
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
246 |
|
18369 | 247 |
lemma neg_one_power: "(-1::int)^n = 1 | (-1::int)^n = -1" |
248 |
by (induct n) auto |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
249 |
|
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
250 |
lemma neg_one_power_eq_mod_m: "[| 2 < m; [(-1::int)^j = (-1::int)^k] (mod m) |] |
18369 | 251 |
==> ((-1::int)^j = (-1::int)^k)" |
252 |
using neg_one_power [of j] and insert neg_one_power [of k] |
|
13871
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
253 |
by (auto simp add: one_not_neg_one_mod_m zcong_sym) |
26e5f5e624f6
Gauss's law of quadratic reciprocity by Avigad, Gray and Kramer
paulson
parents:
diff
changeset
|
254 |
|
18369 | 255 |
end |