src/HOL/Int.thy
 author haftmann Fri Oct 20 07:46:10 2017 +0200 (21 months ago) changeset 66886 960509bfd47e parent 66836 4eb431c3f974 child 66912 a99a7cbf0fb5 permissions -rw-r--r--
```     1 (*  Title:      HOL/Int.thy
```
```     2     Author:     Lawrence C Paulson, Cambridge University Computer Laboratory
```
```     3     Author:     Tobias Nipkow, Florian Haftmann, TU Muenchen
```
```     4 *)
```
```     5
```
```     6 section \<open>The Integers as Equivalence Classes over Pairs of Natural Numbers\<close>
```
```     7
```
```     8 theory Int
```
```     9   imports Equiv_Relations Power Quotient Fun_Def
```
```    10 begin
```
```    11
```
```    12 subsection \<open>Definition of integers as a quotient type\<close>
```
```    13
```
```    14 definition intrel :: "(nat \<times> nat) \<Rightarrow> (nat \<times> nat) \<Rightarrow> bool"
```
```    15   where "intrel = (\<lambda>(x, y) (u, v). x + v = u + y)"
```
```    16
```
```    17 lemma intrel_iff [simp]: "intrel (x, y) (u, v) \<longleftrightarrow> x + v = u + y"
```
```    18   by (simp add: intrel_def)
```
```    19
```
```    20 quotient_type int = "nat \<times> nat" / "intrel"
```
```    21   morphisms Rep_Integ Abs_Integ
```
```    22 proof (rule equivpI)
```
```    23   show "reflp intrel" by (auto simp: reflp_def)
```
```    24   show "symp intrel" by (auto simp: symp_def)
```
```    25   show "transp intrel" by (auto simp: transp_def)
```
```    26 qed
```
```    27
```
```    28 lemma eq_Abs_Integ [case_names Abs_Integ, cases type: int]:
```
```    29   "(\<And>x y. z = Abs_Integ (x, y) \<Longrightarrow> P) \<Longrightarrow> P"
```
```    30   by (induct z) auto
```
```    31
```
```    32
```
```    33 subsection \<open>Integers form a commutative ring\<close>
```
```    34
```
```    35 instantiation int :: comm_ring_1
```
```    36 begin
```
```    37
```
```    38 lift_definition zero_int :: "int" is "(0, 0)" .
```
```    39
```
```    40 lift_definition one_int :: "int" is "(1, 0)" .
```
```    41
```
```    42 lift_definition plus_int :: "int \<Rightarrow> int \<Rightarrow> int"
```
```    43   is "\<lambda>(x, y) (u, v). (x + u, y + v)"
```
```    44   by clarsimp
```
```    45
```
```    46 lift_definition uminus_int :: "int \<Rightarrow> int"
```
```    47   is "\<lambda>(x, y). (y, x)"
```
```    48   by clarsimp
```
```    49
```
```    50 lift_definition minus_int :: "int \<Rightarrow> int \<Rightarrow> int"
```
```    51   is "\<lambda>(x, y) (u, v). (x + v, y + u)"
```
```    52   by clarsimp
```
```    53
```
```    54 lift_definition times_int :: "int \<Rightarrow> int \<Rightarrow> int"
```
```    55   is "\<lambda>(x, y) (u, v). (x*u + y*v, x*v + y*u)"
```
```    56 proof (clarsimp)
```
```    57   fix s t u v w x y z :: nat
```
```    58   assume "s + v = u + t" and "w + z = y + x"
```
```    59   then have "(s + v) * w + (u + t) * x + u * (w + z) + v * (y + x) =
```
```    60     (u + t) * w + (s + v) * x + u * (y + x) + v * (w + z)"
```
```    61     by simp
```
```    62   then show "(s * w + t * x) + (u * z + v * y) = (u * y + v * z) + (s * x + t * w)"
```
```    63     by (simp add: algebra_simps)
```
```    64 qed
```
```    65
```
```    66 instance
```
```    67   by standard (transfer; clarsimp simp: algebra_simps)+
```
```    68
```
```    69 end
```
```    70
```
```    71 abbreviation int :: "nat \<Rightarrow> int"
```
```    72   where "int \<equiv> of_nat"
```
```    73
```
```    74 lemma int_def: "int n = Abs_Integ (n, 0)"
```
```    75   by (induct n) (simp add: zero_int.abs_eq, simp add: one_int.abs_eq plus_int.abs_eq)
```
```    76
```
```    77 lemma int_transfer [transfer_rule]: "(rel_fun (op =) pcr_int) (\<lambda>n. (n, 0)) int"
```
```    78   by (simp add: rel_fun_def int.pcr_cr_eq cr_int_def int_def)
```
```    79
```
```    80 lemma int_diff_cases: obtains (diff) m n where "z = int m - int n"
```
```    81   by transfer clarsimp
```
```    82
```
```    83
```
```    84 subsection \<open>Integers are totally ordered\<close>
```
```    85
```
```    86 instantiation int :: linorder
```
```    87 begin
```
```    88
```
```    89 lift_definition less_eq_int :: "int \<Rightarrow> int \<Rightarrow> bool"
```
```    90   is "\<lambda>(x, y) (u, v). x + v \<le> u + y"
```
```    91   by auto
```
```    92
```
```    93 lift_definition less_int :: "int \<Rightarrow> int \<Rightarrow> bool"
```
```    94   is "\<lambda>(x, y) (u, v). x + v < u + y"
```
```    95   by auto
```
```    96
```
```    97 instance
```
```    98   by standard (transfer, force)+
```
```    99
```
```   100 end
```
```   101
```
```   102 instantiation int :: distrib_lattice
```
```   103 begin
```
```   104
```
```   105 definition "(inf :: int \<Rightarrow> int \<Rightarrow> int) = min"
```
```   106
```
```   107 definition "(sup :: int \<Rightarrow> int \<Rightarrow> int) = max"
```
```   108
```
```   109 instance
```
```   110   by standard (auto simp add: inf_int_def sup_int_def max_min_distrib2)
```
```   111
```
```   112 end
```
```   113
```
```   114
```
```   115 subsection \<open>Ordering properties of arithmetic operations\<close>
```
```   116
```
```   117 instance int :: ordered_cancel_ab_semigroup_add
```
```   118 proof
```
```   119   fix i j k :: int
```
```   120   show "i \<le> j \<Longrightarrow> k + i \<le> k + j"
```
```   121     by transfer clarsimp
```
```   122 qed
```
```   123
```
```   124 text \<open>Strict Monotonicity of Multiplication.\<close>
```
```   125
```
```   126 text \<open>Strict, in 1st argument; proof is by induction on \<open>k > 0\<close>.\<close>
```
```   127 lemma zmult_zless_mono2_lemma: "i < j \<Longrightarrow> 0 < k \<Longrightarrow> int k * i < int k * j"
```
```   128   for i j :: int
```
```   129 proof (induct k)
```
```   130   case 0
```
```   131   then show ?case by simp
```
```   132 next
```
```   133   case (Suc k)
```
```   134   then show ?case
```
```   135     by (cases "k = 0") (simp_all add: distrib_right add_strict_mono)
```
```   136 qed
```
```   137
```
```   138 lemma zero_le_imp_eq_int: "0 \<le> k \<Longrightarrow> \<exists>n. k = int n"
```
```   139   for k :: int
```
```   140   apply transfer
```
```   141   apply clarsimp
```
```   142   apply (rule_tac x="a - b" in exI)
```
```   143   apply simp
```
```   144   done
```
```   145
```
```   146 lemma zero_less_imp_eq_int: "0 < k \<Longrightarrow> \<exists>n>0. k = int n"
```
```   147   for k :: int
```
```   148   apply transfer
```
```   149   apply clarsimp
```
```   150   apply (rule_tac x="a - b" in exI)
```
```   151   apply simp
```
```   152   done
```
```   153
```
```   154 lemma zmult_zless_mono2: "i < j \<Longrightarrow> 0 < k \<Longrightarrow> k * i < k * j"
```
```   155   for i j k :: int
```
```   156   by (drule zero_less_imp_eq_int) (auto simp add: zmult_zless_mono2_lemma)
```
```   157
```
```   158
```
```   159 text \<open>The integers form an ordered integral domain.\<close>
```
```   160
```
```   161 instantiation int :: linordered_idom
```
```   162 begin
```
```   163
```
```   164 definition zabs_def: "\<bar>i::int\<bar> = (if i < 0 then - i else i)"
```
```   165
```
```   166 definition zsgn_def: "sgn (i::int) = (if i = 0 then 0 else if 0 < i then 1 else - 1)"
```
```   167
```
```   168 instance
```
```   169 proof
```
```   170   fix i j k :: int
```
```   171   show "i < j \<Longrightarrow> 0 < k \<Longrightarrow> k * i < k * j"
```
```   172     by (rule zmult_zless_mono2)
```
```   173   show "\<bar>i\<bar> = (if i < 0 then -i else i)"
```
```   174     by (simp only: zabs_def)
```
```   175   show "sgn (i::int) = (if i=0 then 0 else if 0<i then 1 else - 1)"
```
```   176     by (simp only: zsgn_def)
```
```   177 qed
```
```   178
```
```   179 end
```
```   180
```
```   181 lemma zless_imp_add1_zle: "w < z \<Longrightarrow> w + 1 \<le> z"
```
```   182   for w z :: int
```
```   183   by transfer clarsimp
```
```   184
```
```   185 lemma zless_iff_Suc_zadd: "w < z \<longleftrightarrow> (\<exists>n. z = w + int (Suc n))"
```
```   186   for w z :: int
```
```   187   apply transfer
```
```   188   apply auto
```
```   189   apply (rename_tac a b c d)
```
```   190   apply (rule_tac x="c+b - Suc(a+d)" in exI)
```
```   191   apply arith
```
```   192   done
```
```   193
```
```   194 lemma zabs_less_one_iff [simp]: "\<bar>z\<bar> < 1 \<longleftrightarrow> z = 0" (is "?lhs \<longleftrightarrow> ?rhs")
```
```   195   for z :: int
```
```   196 proof
```
```   197   assume ?rhs
```
```   198   then show ?lhs by simp
```
```   199 next
```
```   200   assume ?lhs
```
```   201   with zless_imp_add1_zle [of "\<bar>z\<bar>" 1] have "\<bar>z\<bar> + 1 \<le> 1" by simp
```
```   202   then have "\<bar>z\<bar> \<le> 0" by simp
```
```   203   then show ?rhs by simp
```
```   204 qed
```
```   205
```
```   206 lemmas int_distrib =
```
```   207   distrib_right [of z1 z2 w]
```
```   208   distrib_left [of w z1 z2]
```
```   209   left_diff_distrib [of z1 z2 w]
```
```   210   right_diff_distrib [of w z1 z2]
```
```   211   for z1 z2 w :: int
```
```   212
```
```   213
```
```   214 subsection \<open>Embedding of the Integers into any \<open>ring_1\<close>: \<open>of_int\<close>\<close>
```
```   215
```
```   216 context ring_1
```
```   217 begin
```
```   218
```
```   219 lift_definition of_int :: "int \<Rightarrow> 'a"
```
```   220   is "\<lambda>(i, j). of_nat i - of_nat j"
```
```   221   by (clarsimp simp add: diff_eq_eq eq_diff_eq diff_add_eq
```
```   222       of_nat_add [symmetric] simp del: of_nat_add)
```
```   223
```
```   224 lemma of_int_0 [simp]: "of_int 0 = 0"
```
```   225   by transfer simp
```
```   226
```
```   227 lemma of_int_1 [simp]: "of_int 1 = 1"
```
```   228   by transfer simp
```
```   229
```
```   230 lemma of_int_add [simp]: "of_int (w + z) = of_int w + of_int z"
```
```   231   by transfer (clarsimp simp add: algebra_simps)
```
```   232
```
```   233 lemma of_int_minus [simp]: "of_int (- z) = - (of_int z)"
```
```   234   by (transfer fixing: uminus) clarsimp
```
```   235
```
```   236 lemma of_int_diff [simp]: "of_int (w - z) = of_int w - of_int z"
```
```   237   using of_int_add [of w "- z"] by simp
```
```   238
```
```   239 lemma of_int_mult [simp]: "of_int (w*z) = of_int w * of_int z"
```
```   240   by (transfer fixing: times) (clarsimp simp add: algebra_simps)
```
```   241
```
```   242 lemma mult_of_int_commute: "of_int x * y = y * of_int x"
```
```   243   by (transfer fixing: times) (auto simp: algebra_simps mult_of_nat_commute)
```
```   244
```
```   245 text \<open>Collapse nested embeddings.\<close>
```
```   246 lemma of_int_of_nat_eq [simp]: "of_int (int n) = of_nat n"
```
```   247   by (induct n) auto
```
```   248
```
```   249 lemma of_int_numeral [simp, code_post]: "of_int (numeral k) = numeral k"
```
```   250   by (simp add: of_nat_numeral [symmetric] of_int_of_nat_eq [symmetric])
```
```   251
```
```   252 lemma of_int_neg_numeral [code_post]: "of_int (- numeral k) = - numeral k"
```
```   253   by simp
```
```   254
```
```   255 lemma of_int_power [simp]: "of_int (z ^ n) = of_int z ^ n"
```
```   256   by (induct n) simp_all
```
```   257
```
```   258 lemma of_int_of_bool [simp]:
```
```   259   "of_int (of_bool P) = of_bool P"
```
```   260   by auto
```
```   261
```
```   262 end
```
```   263
```
```   264 context ring_char_0
```
```   265 begin
```
```   266
```
```   267 lemma of_int_eq_iff [simp]: "of_int w = of_int z \<longleftrightarrow> w = z"
```
```   268   by transfer (clarsimp simp add: algebra_simps of_nat_add [symmetric] simp del: of_nat_add)
```
```   269
```
```   270 text \<open>Special cases where either operand is zero.\<close>
```
```   271 lemma of_int_eq_0_iff [simp]: "of_int z = 0 \<longleftrightarrow> z = 0"
```
```   272   using of_int_eq_iff [of z 0] by simp
```
```   273
```
```   274 lemma of_int_0_eq_iff [simp]: "0 = of_int z \<longleftrightarrow> z = 0"
```
```   275   using of_int_eq_iff [of 0 z] by simp
```
```   276
```
```   277 lemma of_int_eq_1_iff [iff]: "of_int z = 1 \<longleftrightarrow> z = 1"
```
```   278   using of_int_eq_iff [of z 1] by simp
```
```   279
```
```   280 end
```
```   281
```
```   282 context linordered_idom
```
```   283 begin
```
```   284
```
```   285 text \<open>Every \<open>linordered_idom\<close> has characteristic zero.\<close>
```
```   286 subclass ring_char_0 ..
```
```   287
```
```   288 lemma of_int_le_iff [simp]: "of_int w \<le> of_int z \<longleftrightarrow> w \<le> z"
```
```   289   by (transfer fixing: less_eq)
```
```   290     (clarsimp simp add: algebra_simps of_nat_add [symmetric] simp del: of_nat_add)
```
```   291
```
```   292 lemma of_int_less_iff [simp]: "of_int w < of_int z \<longleftrightarrow> w < z"
```
```   293   by (simp add: less_le order_less_le)
```
```   294
```
```   295 lemma of_int_0_le_iff [simp]: "0 \<le> of_int z \<longleftrightarrow> 0 \<le> z"
```
```   296   using of_int_le_iff [of 0 z] by simp
```
```   297
```
```   298 lemma of_int_le_0_iff [simp]: "of_int z \<le> 0 \<longleftrightarrow> z \<le> 0"
```
```   299   using of_int_le_iff [of z 0] by simp
```
```   300
```
```   301 lemma of_int_0_less_iff [simp]: "0 < of_int z \<longleftrightarrow> 0 < z"
```
```   302   using of_int_less_iff [of 0 z] by simp
```
```   303
```
```   304 lemma of_int_less_0_iff [simp]: "of_int z < 0 \<longleftrightarrow> z < 0"
```
```   305   using of_int_less_iff [of z 0] by simp
```
```   306
```
```   307 lemma of_int_1_le_iff [simp]: "1 \<le> of_int z \<longleftrightarrow> 1 \<le> z"
```
```   308   using of_int_le_iff [of 1 z] by simp
```
```   309
```
```   310 lemma of_int_le_1_iff [simp]: "of_int z \<le> 1 \<longleftrightarrow> z \<le> 1"
```
```   311   using of_int_le_iff [of z 1] by simp
```
```   312
```
```   313 lemma of_int_1_less_iff [simp]: "1 < of_int z \<longleftrightarrow> 1 < z"
```
```   314   using of_int_less_iff [of 1 z] by simp
```
```   315
```
```   316 lemma of_int_less_1_iff [simp]: "of_int z < 1 \<longleftrightarrow> z < 1"
```
```   317   using of_int_less_iff [of z 1] by simp
```
```   318
```
```   319 lemma of_int_pos: "z > 0 \<Longrightarrow> of_int z > 0"
```
```   320   by simp
```
```   321
```
```   322 lemma of_int_nonneg: "z \<ge> 0 \<Longrightarrow> of_int z \<ge> 0"
```
```   323   by simp
```
```   324
```
```   325 lemma of_int_abs [simp]: "of_int \<bar>x\<bar> = \<bar>of_int x\<bar>"
```
```   326   by (auto simp add: abs_if)
```
```   327
```
```   328 lemma of_int_lessD:
```
```   329   assumes "\<bar>of_int n\<bar> < x"
```
```   330   shows "n = 0 \<or> x > 1"
```
```   331 proof (cases "n = 0")
```
```   332   case True
```
```   333   then show ?thesis by simp
```
```   334 next
```
```   335   case False
```
```   336   then have "\<bar>n\<bar> \<noteq> 0" by simp
```
```   337   then have "\<bar>n\<bar> > 0" by simp
```
```   338   then have "\<bar>n\<bar> \<ge> 1"
```
```   339     using zless_imp_add1_zle [of 0 "\<bar>n\<bar>"] by simp
```
```   340   then have "\<bar>of_int n\<bar> \<ge> 1"
```
```   341     unfolding of_int_1_le_iff [of "\<bar>n\<bar>", symmetric] by simp
```
```   342   then have "1 < x" using assms by (rule le_less_trans)
```
```   343   then show ?thesis ..
```
```   344 qed
```
```   345
```
```   346 lemma of_int_leD:
```
```   347   assumes "\<bar>of_int n\<bar> \<le> x"
```
```   348   shows "n = 0 \<or> 1 \<le> x"
```
```   349 proof (cases "n = 0")
```
```   350   case True
```
```   351   then show ?thesis by simp
```
```   352 next
```
```   353   case False
```
```   354   then have "\<bar>n\<bar> \<noteq> 0" by simp
```
```   355   then have "\<bar>n\<bar> > 0" by simp
```
```   356   then have "\<bar>n\<bar> \<ge> 1"
```
```   357     using zless_imp_add1_zle [of 0 "\<bar>n\<bar>"] by simp
```
```   358   then have "\<bar>of_int n\<bar> \<ge> 1"
```
```   359     unfolding of_int_1_le_iff [of "\<bar>n\<bar>", symmetric] by simp
```
```   360   then have "1 \<le> x" using assms by (rule order_trans)
```
```   361   then show ?thesis ..
```
```   362 qed
```
```   363
```
```   364 end
```
```   365
```
```   366 text \<open>Comparisons involving @{term of_int}.\<close>
```
```   367
```
```   368 lemma of_int_eq_numeral_iff [iff]: "of_int z = (numeral n :: 'a::ring_char_0) \<longleftrightarrow> z = numeral n"
```
```   369   using of_int_eq_iff by fastforce
```
```   370
```
```   371 lemma of_int_le_numeral_iff [simp]:
```
```   372   "of_int z \<le> (numeral n :: 'a::linordered_idom) \<longleftrightarrow> z \<le> numeral n"
```
```   373   using of_int_le_iff [of z "numeral n"] by simp
```
```   374
```
```   375 lemma of_int_numeral_le_iff [simp]:
```
```   376   "(numeral n :: 'a::linordered_idom) \<le> of_int z \<longleftrightarrow> numeral n \<le> z"
```
```   377   using of_int_le_iff [of "numeral n"] by simp
```
```   378
```
```   379 lemma of_int_less_numeral_iff [simp]:
```
```   380   "of_int z < (numeral n :: 'a::linordered_idom) \<longleftrightarrow> z < numeral n"
```
```   381   using of_int_less_iff [of z "numeral n"] by simp
```
```   382
```
```   383 lemma of_int_numeral_less_iff [simp]:
```
```   384   "(numeral n :: 'a::linordered_idom) < of_int z \<longleftrightarrow> numeral n < z"
```
```   385   using of_int_less_iff [of "numeral n" z] by simp
```
```   386
```
```   387 lemma of_nat_less_of_int_iff: "(of_nat n::'a::linordered_idom) < of_int x \<longleftrightarrow> int n < x"
```
```   388   by (metis of_int_of_nat_eq of_int_less_iff)
```
```   389
```
```   390 lemma of_int_eq_id [simp]: "of_int = id"
```
```   391 proof
```
```   392   show "of_int z = id z" for z
```
```   393     by (cases z rule: int_diff_cases) simp
```
```   394 qed
```
```   395
```
```   396 instance int :: no_top
```
```   397   apply standard
```
```   398   apply (rule_tac x="x + 1" in exI)
```
```   399   apply simp
```
```   400   done
```
```   401
```
```   402 instance int :: no_bot
```
```   403   apply standard
```
```   404   apply (rule_tac x="x - 1" in exI)
```
```   405   apply simp
```
```   406   done
```
```   407
```
```   408
```
```   409 subsection \<open>Magnitude of an Integer, as a Natural Number: \<open>nat\<close>\<close>
```
```   410
```
```   411 lift_definition nat :: "int \<Rightarrow> nat" is "\<lambda>(x, y). x - y"
```
```   412   by auto
```
```   413
```
```   414 lemma nat_int [simp]: "nat (int n) = n"
```
```   415   by transfer simp
```
```   416
```
```   417 lemma int_nat_eq [simp]: "int (nat z) = (if 0 \<le> z then z else 0)"
```
```   418   by transfer clarsimp
```
```   419
```
```   420 lemma nat_0_le: "0 \<le> z \<Longrightarrow> int (nat z) = z"
```
```   421   by simp
```
```   422
```
```   423 lemma nat_le_0 [simp]: "z \<le> 0 \<Longrightarrow> nat z = 0"
```
```   424   by transfer clarsimp
```
```   425
```
```   426 lemma nat_le_eq_zle: "0 < w \<or> 0 \<le> z \<Longrightarrow> nat w \<le> nat z \<longleftrightarrow> w \<le> z"
```
```   427   by transfer (clarsimp, arith)
```
```   428
```
```   429 text \<open>An alternative condition is @{term "0 \<le> w"}.\<close>
```
```   430 lemma nat_mono_iff: "0 < z \<Longrightarrow> nat w < nat z \<longleftrightarrow> w < z"
```
```   431   by (simp add: nat_le_eq_zle linorder_not_le [symmetric])
```
```   432
```
```   433 lemma nat_less_eq_zless: "0 \<le> w \<Longrightarrow> nat w < nat z \<longleftrightarrow> w < z"
```
```   434   by (simp add: nat_le_eq_zle linorder_not_le [symmetric])
```
```   435
```
```   436 lemma zless_nat_conj [simp]: "nat w < nat z \<longleftrightarrow> 0 < z \<and> w < z"
```
```   437   by transfer (clarsimp, arith)
```
```   438
```
```   439 lemma nonneg_int_cases:
```
```   440   assumes "0 \<le> k"
```
```   441   obtains n where "k = int n"
```
```   442 proof -
```
```   443   from assms have "k = int (nat k)"
```
```   444     by simp
```
```   445   then show thesis
```
```   446     by (rule that)
```
```   447 qed
```
```   448
```
```   449 lemma pos_int_cases:
```
```   450   assumes "0 < k"
```
```   451   obtains n where "k = int n" and "n > 0"
```
```   452 proof -
```
```   453   from assms have "0 \<le> k"
```
```   454     by simp
```
```   455   then obtain n where "k = int n"
```
```   456     by (rule nonneg_int_cases)
```
```   457   moreover have "n > 0"
```
```   458     using \<open>k = int n\<close> assms by simp
```
```   459   ultimately show thesis
```
```   460     by (rule that)
```
```   461 qed
```
```   462
```
```   463 lemma nonpos_int_cases:
```
```   464   assumes "k \<le> 0"
```
```   465   obtains n where "k = - int n"
```
```   466 proof -
```
```   467   from assms have "- k \<ge> 0"
```
```   468     by simp
```
```   469   then obtain n where "- k = int n"
```
```   470     by (rule nonneg_int_cases)
```
```   471   then have "k = - int n"
```
```   472     by simp
```
```   473   then show thesis
```
```   474     by (rule that)
```
```   475 qed
```
```   476
```
```   477 lemma neg_int_cases:
```
```   478   assumes "k < 0"
```
```   479   obtains n where "k = - int n" and "n > 0"
```
```   480 proof -
```
```   481   from assms have "- k > 0"
```
```   482     by simp
```
```   483   then obtain n where "- k = int n" and "- k > 0"
```
```   484     by (blast elim: pos_int_cases)
```
```   485   then have "k = - int n" and "n > 0"
```
```   486     by simp_all
```
```   487   then show thesis
```
```   488     by (rule that)
```
```   489 qed
```
```   490
```
```   491 lemma nat_eq_iff: "nat w = m \<longleftrightarrow> (if 0 \<le> w then w = int m else m = 0)"
```
```   492   by transfer (clarsimp simp add: le_imp_diff_is_add)
```
```   493
```
```   494 lemma nat_eq_iff2: "m = nat w \<longleftrightarrow> (if 0 \<le> w then w = int m else m = 0)"
```
```   495   using nat_eq_iff [of w m] by auto
```
```   496
```
```   497 lemma nat_0 [simp]: "nat 0 = 0"
```
```   498   by (simp add: nat_eq_iff)
```
```   499
```
```   500 lemma nat_1 [simp]: "nat 1 = Suc 0"
```
```   501   by (simp add: nat_eq_iff)
```
```   502
```
```   503 lemma nat_numeral [simp]: "nat (numeral k) = numeral k"
```
```   504   by (simp add: nat_eq_iff)
```
```   505
```
```   506 lemma nat_neg_numeral [simp]: "nat (- numeral k) = 0"
```
```   507   by simp
```
```   508
```
```   509 lemma nat_2: "nat 2 = Suc (Suc 0)"
```
```   510   by simp
```
```   511
```
```   512 lemma nat_less_iff: "0 \<le> w \<Longrightarrow> nat w < m \<longleftrightarrow> w < of_nat m"
```
```   513   by transfer (clarsimp, arith)
```
```   514
```
```   515 lemma nat_le_iff: "nat x \<le> n \<longleftrightarrow> x \<le> int n"
```
```   516   by transfer (clarsimp simp add: le_diff_conv)
```
```   517
```
```   518 lemma nat_mono: "x \<le> y \<Longrightarrow> nat x \<le> nat y"
```
```   519   by transfer auto
```
```   520
```
```   521 lemma nat_0_iff[simp]: "nat i = 0 \<longleftrightarrow> i \<le> 0"
```
```   522   for i :: int
```
```   523   by transfer clarsimp
```
```   524
```
```   525 lemma int_eq_iff: "of_nat m = z \<longleftrightarrow> m = nat z \<and> 0 \<le> z"
```
```   526   by (auto simp add: nat_eq_iff2)
```
```   527
```
```   528 lemma zero_less_nat_eq [simp]: "0 < nat z \<longleftrightarrow> 0 < z"
```
```   529   using zless_nat_conj [of 0] by auto
```
```   530
```
```   531 lemma nat_add_distrib: "0 \<le> z \<Longrightarrow> 0 \<le> z' \<Longrightarrow> nat (z + z') = nat z + nat z'"
```
```   532   by transfer clarsimp
```
```   533
```
```   534 lemma nat_diff_distrib': "0 \<le> x \<Longrightarrow> 0 \<le> y \<Longrightarrow> nat (x - y) = nat x - nat y"
```
```   535   by transfer clarsimp
```
```   536
```
```   537 lemma nat_diff_distrib: "0 \<le> z' \<Longrightarrow> z' \<le> z \<Longrightarrow> nat (z - z') = nat z - nat z'"
```
```   538   by (rule nat_diff_distrib') auto
```
```   539
```
```   540 lemma nat_zminus_int [simp]: "nat (- int n) = 0"
```
```   541   by transfer simp
```
```   542
```
```   543 lemma le_nat_iff: "k \<ge> 0 \<Longrightarrow> n \<le> nat k \<longleftrightarrow> int n \<le> k"
```
```   544   by transfer auto
```
```   545
```
```   546 lemma zless_nat_eq_int_zless: "m < nat z \<longleftrightarrow> int m < z"
```
```   547   by transfer (clarsimp simp add: less_diff_conv)
```
```   548
```
```   549 lemma (in ring_1) of_nat_nat [simp]: "0 \<le> z \<Longrightarrow> of_nat (nat z) = of_int z"
```
```   550   by transfer (clarsimp simp add: of_nat_diff)
```
```   551
```
```   552 lemma diff_nat_numeral [simp]: "(numeral v :: nat) - numeral v' = nat (numeral v - numeral v')"
```
```   553   by (simp only: nat_diff_distrib' zero_le_numeral nat_numeral)
```
```   554
```
```   555 lemma nat_abs_triangle_ineq:
```
```   556   "nat \<bar>k + l\<bar> \<le> nat \<bar>k\<bar> + nat \<bar>l\<bar>"
```
```   557   by (simp add: nat_add_distrib [symmetric] nat_le_eq_zle abs_triangle_ineq)
```
```   558
```
```   559 lemma nat_of_bool [simp]:
```
```   560   "nat (of_bool P) = of_bool P"
```
```   561   by auto
```
```   562
```
```   563 lemma split_nat [arith_split]: "P (nat i) \<longleftrightarrow> ((\<forall>n. i = int n \<longrightarrow> P n) \<and> (i < 0 \<longrightarrow> P 0))"
```
```   564   (is "?P = (?L \<and> ?R)")
```
```   565   for i :: int
```
```   566 proof (cases "i < 0")
```
```   567   case True
```
```   568   then show ?thesis
```
```   569     by auto
```
```   570 next
```
```   571   case False
```
```   572   have "?P = ?L"
```
```   573   proof
```
```   574     assume ?P
```
```   575     then show ?L using False by auto
```
```   576   next
```
```   577     assume ?L
```
```   578     moreover from False have "int (nat i) = i"
```
```   579       by (simp add: not_less)
```
```   580     ultimately show ?P
```
```   581       by simp
```
```   582   qed
```
```   583   with False show ?thesis by simp
```
```   584 qed
```
```   585
```
```   586 lemma all_nat: "(\<forall>x. P x) \<longleftrightarrow> (\<forall>x\<ge>0. P (nat x))"
```
```   587   by (auto split: split_nat)
```
```   588
```
```   589 lemma ex_nat: "(\<exists>x. P x) \<longleftrightarrow> (\<exists>x. 0 \<le> x \<and> P (nat x))"
```
```   590 proof
```
```   591   assume "\<exists>x. P x"
```
```   592   then obtain x where "P x" ..
```
```   593   then have "int x \<ge> 0 \<and> P (nat (int x))" by simp
```
```   594   then show "\<exists>x\<ge>0. P (nat x)" ..
```
```   595 next
```
```   596   assume "\<exists>x\<ge>0. P (nat x)"
```
```   597   then show "\<exists>x. P x" by auto
```
```   598 qed
```
```   599
```
```   600
```
```   601 text \<open>For termination proofs:\<close>
```
```   602 lemma measure_function_int[measure_function]: "is_measure (nat \<circ> abs)" ..
```
```   603
```
```   604
```
```   605 subsection \<open>Lemmas about the Function @{term of_nat} and Orderings\<close>
```
```   606
```
```   607 lemma negative_zless_0: "- (int (Suc n)) < (0 :: int)"
```
```   608   by (simp add: order_less_le del: of_nat_Suc)
```
```   609
```
```   610 lemma negative_zless [iff]: "- (int (Suc n)) < int m"
```
```   611   by (rule negative_zless_0 [THEN order_less_le_trans], simp)
```
```   612
```
```   613 lemma negative_zle_0: "- int n \<le> 0"
```
```   614   by (simp add: minus_le_iff)
```
```   615
```
```   616 lemma negative_zle [iff]: "- int n \<le> int m"
```
```   617   by (rule order_trans [OF negative_zle_0 of_nat_0_le_iff])
```
```   618
```
```   619 lemma not_zle_0_negative [simp]: "\<not> 0 \<le> - int (Suc n)"
```
```   620   by (subst le_minus_iff) (simp del: of_nat_Suc)
```
```   621
```
```   622 lemma int_zle_neg: "int n \<le> - int m \<longleftrightarrow> n = 0 \<and> m = 0"
```
```   623   by transfer simp
```
```   624
```
```   625 lemma not_int_zless_negative [simp]: "\<not> int n < - int m"
```
```   626   by (simp add: linorder_not_less)
```
```   627
```
```   628 lemma negative_eq_positive [simp]: "- int n = of_nat m \<longleftrightarrow> n = 0 \<and> m = 0"
```
```   629   by (force simp add: order_eq_iff [of "- of_nat n"] int_zle_neg)
```
```   630
```
```   631 lemma zle_iff_zadd: "w \<le> z \<longleftrightarrow> (\<exists>n. z = w + int n)"
```
```   632   (is "?lhs \<longleftrightarrow> ?rhs")
```
```   633 proof
```
```   634   assume ?rhs
```
```   635   then show ?lhs by auto
```
```   636 next
```
```   637   assume ?lhs
```
```   638   then have "0 \<le> z - w" by simp
```
```   639   then obtain n where "z - w = int n"
```
```   640     using zero_le_imp_eq_int [of "z - w"] by blast
```
```   641   then have "z = w + int n" by simp
```
```   642   then show ?rhs ..
```
```   643 qed
```
```   644
```
```   645 lemma zadd_int_left: "int m + (int n + z) = int (m + n) + z"
```
```   646   by simp
```
```   647
```
```   648 text \<open>
```
```   649   This version is proved for all ordered rings, not just integers!
```
```   650   It is proved here because attribute \<open>arith_split\<close> is not available
```
```   651   in theory \<open>Rings\<close>.
```
```   652   But is it really better than just rewriting with \<open>abs_if\<close>?
```
```   653 \<close>
```
```   654 lemma abs_split [arith_split, no_atp]: "P \<bar>a\<bar> \<longleftrightarrow> (0 \<le> a \<longrightarrow> P a) \<and> (a < 0 \<longrightarrow> P (- a))"
```
```   655   for a :: "'a::linordered_idom"
```
```   656   by (force dest: order_less_le_trans simp add: abs_if linorder_not_less)
```
```   657
```
```   658 lemma negD: "x < 0 \<Longrightarrow> \<exists>n. x = - (int (Suc n))"
```
```   659   apply transfer
```
```   660   apply clarsimp
```
```   661   apply (rule_tac x="b - Suc a" in exI)
```
```   662   apply arith
```
```   663   done
```
```   664
```
```   665
```
```   666 subsection \<open>Cases and induction\<close>
```
```   667
```
```   668 text \<open>
```
```   669   Now we replace the case analysis rule by a more conventional one:
```
```   670   whether an integer is negative or not.
```
```   671 \<close>
```
```   672
```
```   673 text \<open>This version is symmetric in the two subgoals.\<close>
```
```   674 lemma int_cases2 [case_names nonneg nonpos, cases type: int]:
```
```   675   "(\<And>n. z = int n \<Longrightarrow> P) \<Longrightarrow> (\<And>n. z = - (int n) \<Longrightarrow> P) \<Longrightarrow> P"
```
```   676   by (cases "z < 0") (auto simp add: linorder_not_less dest!: negD nat_0_le [THEN sym])
```
```   677
```
```   678 text \<open>This is the default, with a negative case.\<close>
```
```   679 lemma int_cases [case_names nonneg neg, cases type: int]:
```
```   680   "(\<And>n. z = int n \<Longrightarrow> P) \<Longrightarrow> (\<And>n. z = - (int (Suc n)) \<Longrightarrow> P) \<Longrightarrow> P"
```
```   681   apply (cases "z < 0")
```
```   682    apply (blast dest!: negD)
```
```   683   apply (simp add: linorder_not_less del: of_nat_Suc)
```
```   684   apply auto
```
```   685   apply (blast dest: nat_0_le [THEN sym])
```
```   686   done
```
```   687
```
```   688 lemma int_cases3 [case_names zero pos neg]:
```
```   689   fixes k :: int
```
```   690   assumes "k = 0 \<Longrightarrow> P" and "\<And>n. k = int n \<Longrightarrow> n > 0 \<Longrightarrow> P"
```
```   691     and "\<And>n. k = - int n \<Longrightarrow> n > 0 \<Longrightarrow> P"
```
```   692   shows "P"
```
```   693 proof (cases k "0::int" rule: linorder_cases)
```
```   694   case equal
```
```   695   with assms(1) show P by simp
```
```   696 next
```
```   697   case greater
```
```   698   then have *: "nat k > 0" by simp
```
```   699   moreover from * have "k = int (nat k)" by auto
```
```   700   ultimately show P using assms(2) by blast
```
```   701 next
```
```   702   case less
```
```   703   then have *: "nat (- k) > 0" by simp
```
```   704   moreover from * have "k = - int (nat (- k))" by auto
```
```   705   ultimately show P using assms(3) by blast
```
```   706 qed
```
```   707
```
```   708 lemma int_of_nat_induct [case_names nonneg neg, induct type: int]:
```
```   709   "(\<And>n. P (int n)) \<Longrightarrow> (\<And>n. P (- (int (Suc n)))) \<Longrightarrow> P z"
```
```   710   by (cases z) auto
```
```   711
```
```   712 lemma Let_numeral [simp]: "Let (numeral v) f = f (numeral v)"
```
```   713   \<comment> \<open>Unfold all \<open>let\<close>s involving constants\<close>
```
```   714   by (fact Let_numeral) \<comment> \<open>FIXME drop\<close>
```
```   715
```
```   716 lemma Let_neg_numeral [simp]: "Let (- numeral v) f = f (- numeral v)"
```
```   717   \<comment> \<open>Unfold all \<open>let\<close>s involving constants\<close>
```
```   718   by (fact Let_neg_numeral) \<comment> \<open>FIXME drop\<close>
```
```   719
```
```   720 lemma sgn_mult_dvd_iff [simp]:
```
```   721   "sgn r * l dvd k \<longleftrightarrow> l dvd k \<and> (r = 0 \<longrightarrow> k = 0)" for k l r :: int
```
```   722   by (cases r rule: int_cases3) auto
```
```   723
```
```   724 lemma mult_sgn_dvd_iff [simp]:
```
```   725   "l * sgn r dvd k \<longleftrightarrow> l dvd k \<and> (r = 0 \<longrightarrow> k = 0)" for k l r :: int
```
```   726   using sgn_mult_dvd_iff [of r l k] by (simp add: ac_simps)
```
```   727
```
```   728 lemma dvd_sgn_mult_iff [simp]:
```
```   729   "l dvd sgn r * k \<longleftrightarrow> l dvd k \<or> r = 0" for k l r :: int
```
```   730   by (cases r rule: int_cases3) simp_all
```
```   731
```
```   732 lemma dvd_mult_sgn_iff [simp]:
```
```   733   "l dvd k * sgn r \<longleftrightarrow> l dvd k \<or> r = 0" for k l r :: int
```
```   734   using dvd_sgn_mult_iff [of l r k] by (simp add: ac_simps)
```
```   735
```
```   736 lemma int_sgnE:
```
```   737   fixes k :: int
```
```   738   obtains n and l where "k = sgn l * int n"
```
```   739 proof -
```
```   740   have "k = sgn k * int (nat \<bar>k\<bar>)"
```
```   741     by (simp add: sgn_mult_abs)
```
```   742   then show ?thesis ..
```
```   743 qed
```
```   744
```
```   745 text \<open>Unfold \<open>min\<close> and \<open>max\<close> on numerals.\<close>
```
```   746
```
```   747 lemmas max_number_of [simp] =
```
```   748   max_def [of "numeral u" "numeral v"]
```
```   749   max_def [of "numeral u" "- numeral v"]
```
```   750   max_def [of "- numeral u" "numeral v"]
```
```   751   max_def [of "- numeral u" "- numeral v"] for u v
```
```   752
```
```   753 lemmas min_number_of [simp] =
```
```   754   min_def [of "numeral u" "numeral v"]
```
```   755   min_def [of "numeral u" "- numeral v"]
```
```   756   min_def [of "- numeral u" "numeral v"]
```
```   757   min_def [of "- numeral u" "- numeral v"] for u v
```
```   758
```
```   759
```
```   760 subsubsection \<open>Binary comparisons\<close>
```
```   761
```
```   762 text \<open>Preliminaries\<close>
```
```   763
```
```   764 lemma le_imp_0_less:
```
```   765   fixes z :: int
```
```   766   assumes le: "0 \<le> z"
```
```   767   shows "0 < 1 + z"
```
```   768 proof -
```
```   769   have "0 \<le> z" by fact
```
```   770   also have "\<dots> < z + 1" by (rule less_add_one)
```
```   771   also have "\<dots> = 1 + z" by (simp add: ac_simps)
```
```   772   finally show "0 < 1 + z" .
```
```   773 qed
```
```   774
```
```   775 lemma odd_less_0_iff: "1 + z + z < 0 \<longleftrightarrow> z < 0"
```
```   776   for z :: int
```
```   777 proof (cases z)
```
```   778   case (nonneg n)
```
```   779   then show ?thesis
```
```   780     by (simp add: linorder_not_less add.assoc add_increasing le_imp_0_less [THEN order_less_imp_le])
```
```   781 next
```
```   782   case (neg n)
```
```   783   then show ?thesis
```
```   784     by (simp del: of_nat_Suc of_nat_add of_nat_1
```
```   785         add: algebra_simps of_nat_1 [where 'a=int, symmetric] of_nat_add [symmetric])
```
```   786 qed
```
```   787
```
```   788
```
```   789 subsubsection \<open>Comparisons, for Ordered Rings\<close>
```
```   790
```
```   791 lemmas double_eq_0_iff = double_zero
```
```   792
```
```   793 lemma odd_nonzero: "1 + z + z \<noteq> 0"
```
```   794   for z :: int
```
```   795 proof (cases z)
```
```   796   case (nonneg n)
```
```   797   have le: "0 \<le> z + z"
```
```   798     by (simp add: nonneg add_increasing)
```
```   799   then show ?thesis
```
```   800     using  le_imp_0_less [OF le] by (auto simp: add.assoc)
```
```   801 next
```
```   802   case (neg n)
```
```   803   show ?thesis
```
```   804   proof
```
```   805     assume eq: "1 + z + z = 0"
```
```   806     have "0 < 1 + (int n + int n)"
```
```   807       by (simp add: le_imp_0_less add_increasing)
```
```   808     also have "\<dots> = - (1 + z + z)"
```
```   809       by (simp add: neg add.assoc [symmetric])
```
```   810     also have "\<dots> = 0" by (simp add: eq)
```
```   811     finally have "0<0" ..
```
```   812     then show False by blast
```
```   813   qed
```
```   814 qed
```
```   815
```
```   816
```
```   817 subsection \<open>The Set of Integers\<close>
```
```   818
```
```   819 context ring_1
```
```   820 begin
```
```   821
```
```   822 definition Ints :: "'a set"  ("\<int>")
```
```   823   where "\<int> = range of_int"
```
```   824
```
```   825 lemma Ints_of_int [simp]: "of_int z \<in> \<int>"
```
```   826   by (simp add: Ints_def)
```
```   827
```
```   828 lemma Ints_of_nat [simp]: "of_nat n \<in> \<int>"
```
```   829   using Ints_of_int [of "of_nat n"] by simp
```
```   830
```
```   831 lemma Ints_0 [simp]: "0 \<in> \<int>"
```
```   832   using Ints_of_int [of "0"] by simp
```
```   833
```
```   834 lemma Ints_1 [simp]: "1 \<in> \<int>"
```
```   835   using Ints_of_int [of "1"] by simp
```
```   836
```
```   837 lemma Ints_numeral [simp]: "numeral n \<in> \<int>"
```
```   838   by (subst of_nat_numeral [symmetric], rule Ints_of_nat)
```
```   839
```
```   840 lemma Ints_add [simp]: "a \<in> \<int> \<Longrightarrow> b \<in> \<int> \<Longrightarrow> a + b \<in> \<int>"
```
```   841   apply (auto simp add: Ints_def)
```
```   842   apply (rule range_eqI)
```
```   843   apply (rule of_int_add [symmetric])
```
```   844   done
```
```   845
```
```   846 lemma Ints_minus [simp]: "a \<in> \<int> \<Longrightarrow> -a \<in> \<int>"
```
```   847   apply (auto simp add: Ints_def)
```
```   848   apply (rule range_eqI)
```
```   849   apply (rule of_int_minus [symmetric])
```
```   850   done
```
```   851
```
```   852 lemma Ints_diff [simp]: "a \<in> \<int> \<Longrightarrow> b \<in> \<int> \<Longrightarrow> a - b \<in> \<int>"
```
```   853   apply (auto simp add: Ints_def)
```
```   854   apply (rule range_eqI)
```
```   855   apply (rule of_int_diff [symmetric])
```
```   856   done
```
```   857
```
```   858 lemma Ints_mult [simp]: "a \<in> \<int> \<Longrightarrow> b \<in> \<int> \<Longrightarrow> a * b \<in> \<int>"
```
```   859   apply (auto simp add: Ints_def)
```
```   860   apply (rule range_eqI)
```
```   861   apply (rule of_int_mult [symmetric])
```
```   862   done
```
```   863
```
```   864 lemma Ints_power [simp]: "a \<in> \<int> \<Longrightarrow> a ^ n \<in> \<int>"
```
```   865   by (induct n) simp_all
```
```   866
```
```   867 lemma Ints_cases [cases set: Ints]:
```
```   868   assumes "q \<in> \<int>"
```
```   869   obtains (of_int) z where "q = of_int z"
```
```   870   unfolding Ints_def
```
```   871 proof -
```
```   872   from \<open>q \<in> \<int>\<close> have "q \<in> range of_int" unfolding Ints_def .
```
```   873   then obtain z where "q = of_int z" ..
```
```   874   then show thesis ..
```
```   875 qed
```
```   876
```
```   877 lemma Ints_induct [case_names of_int, induct set: Ints]:
```
```   878   "q \<in> \<int> \<Longrightarrow> (\<And>z. P (of_int z)) \<Longrightarrow> P q"
```
```   879   by (rule Ints_cases) auto
```
```   880
```
```   881 lemma Nats_subset_Ints: "\<nat> \<subseteq> \<int>"
```
```   882   unfolding Nats_def Ints_def
```
```   883   by (rule subsetI, elim imageE, hypsubst, subst of_int_of_nat_eq[symmetric], rule imageI) simp_all
```
```   884
```
```   885 lemma Nats_altdef1: "\<nat> = {of_int n |n. n \<ge> 0}"
```
```   886 proof (intro subsetI equalityI)
```
```   887   fix x :: 'a
```
```   888   assume "x \<in> {of_int n |n. n \<ge> 0}"
```
```   889   then obtain n where "x = of_int n" "n \<ge> 0"
```
```   890     by (auto elim!: Ints_cases)
```
```   891   then have "x = of_nat (nat n)"
```
```   892     by (subst of_nat_nat) simp_all
```
```   893   then show "x \<in> \<nat>"
```
```   894     by simp
```
```   895 next
```
```   896   fix x :: 'a
```
```   897   assume "x \<in> \<nat>"
```
```   898   then obtain n where "x = of_nat n"
```
```   899     by (auto elim!: Nats_cases)
```
```   900   then have "x = of_int (int n)" by simp
```
```   901   also have "int n \<ge> 0" by simp
```
```   902   then have "of_int (int n) \<in> {of_int n |n. n \<ge> 0}" by blast
```
```   903   finally show "x \<in> {of_int n |n. n \<ge> 0}" .
```
```   904 qed
```
```   905
```
```   906 end
```
```   907
```
```   908 lemma (in linordered_idom) Ints_abs [simp]:
```
```   909   shows "a \<in> \<int> \<Longrightarrow> abs a \<in> \<int>"
```
```   910   by (auto simp: abs_if)
```
```   911
```
```   912 lemma (in linordered_idom) Nats_altdef2: "\<nat> = {n \<in> \<int>. n \<ge> 0}"
```
```   913 proof (intro subsetI equalityI)
```
```   914   fix x :: 'a
```
```   915   assume "x \<in> {n \<in> \<int>. n \<ge> 0}"
```
```   916   then obtain n where "x = of_int n" "n \<ge> 0"
```
```   917     by (auto elim!: Ints_cases)
```
```   918   then have "x = of_nat (nat n)"
```
```   919     by (subst of_nat_nat) simp_all
```
```   920   then show "x \<in> \<nat>"
```
```   921     by simp
```
```   922 qed (auto elim!: Nats_cases)
```
```   923
```
```   924 lemma (in idom_divide) of_int_divide_in_Ints:
```
```   925   "of_int a div of_int b \<in> \<int>" if "b dvd a"
```
```   926 proof -
```
```   927   from that obtain c where "a = b * c" ..
```
```   928   then show ?thesis
```
```   929     by (cases "of_int b = 0") simp_all
```
```   930 qed
```
```   931
```
```   932 text \<open>The premise involving @{term Ints} prevents @{term "a = 1/2"}.\<close>
```
```   933
```
```   934 lemma Ints_double_eq_0_iff:
```
```   935   fixes a :: "'a::ring_char_0"
```
```   936   assumes in_Ints: "a \<in> \<int>"
```
```   937   shows "a + a = 0 \<longleftrightarrow> a = 0"
```
```   938     (is "?lhs \<longleftrightarrow> ?rhs")
```
```   939 proof -
```
```   940   from in_Ints have "a \<in> range of_int"
```
```   941     unfolding Ints_def [symmetric] .
```
```   942   then obtain z where a: "a = of_int z" ..
```
```   943   show ?thesis
```
```   944   proof
```
```   945     assume ?rhs
```
```   946     then show ?lhs by simp
```
```   947   next
```
```   948     assume ?lhs
```
```   949     with a have "of_int (z + z) = (of_int 0 :: 'a)" by simp
```
```   950     then have "z + z = 0" by (simp only: of_int_eq_iff)
```
```   951     then have "z = 0" by (simp only: double_eq_0_iff)
```
```   952     with a show ?rhs by simp
```
```   953   qed
```
```   954 qed
```
```   955
```
```   956 lemma Ints_odd_nonzero:
```
```   957   fixes a :: "'a::ring_char_0"
```
```   958   assumes in_Ints: "a \<in> \<int>"
```
```   959   shows "1 + a + a \<noteq> 0"
```
```   960 proof -
```
```   961   from in_Ints have "a \<in> range of_int"
```
```   962     unfolding Ints_def [symmetric] .
```
```   963   then obtain z where a: "a = of_int z" ..
```
```   964   show ?thesis
```
```   965   proof
```
```   966     assume "1 + a + a = 0"
```
```   967     with a have "of_int (1 + z + z) = (of_int 0 :: 'a)" by simp
```
```   968     then have "1 + z + z = 0" by (simp only: of_int_eq_iff)
```
```   969     with odd_nonzero show False by blast
```
```   970   qed
```
```   971 qed
```
```   972
```
```   973 lemma Nats_numeral [simp]: "numeral w \<in> \<nat>"
```
```   974   using of_nat_in_Nats [of "numeral w"] by simp
```
```   975
```
```   976 lemma Ints_odd_less_0:
```
```   977   fixes a :: "'a::linordered_idom"
```
```   978   assumes in_Ints: "a \<in> \<int>"
```
```   979   shows "1 + a + a < 0 \<longleftrightarrow> a < 0"
```
```   980 proof -
```
```   981   from in_Ints have "a \<in> range of_int"
```
```   982     unfolding Ints_def [symmetric] .
```
```   983   then obtain z where a: "a = of_int z" ..
```
```   984   with a have "1 + a + a < 0 \<longleftrightarrow> of_int (1 + z + z) < (of_int 0 :: 'a)"
```
```   985     by simp
```
```   986   also have "\<dots> \<longleftrightarrow> z < 0"
```
```   987     by (simp only: of_int_less_iff odd_less_0_iff)
```
```   988   also have "\<dots> \<longleftrightarrow> a < 0"
```
```   989     by (simp add: a)
```
```   990   finally show ?thesis .
```
```   991 qed
```
```   992
```
```   993
```
```   994 subsection \<open>@{term sum} and @{term prod}\<close>
```
```   995
```
```   996 lemma of_nat_sum [simp]: "of_nat (sum f A) = (\<Sum>x\<in>A. of_nat(f x))"
```
```   997   by (induct A rule: infinite_finite_induct) auto
```
```   998
```
```   999 lemma of_int_sum [simp]: "of_int (sum f A) = (\<Sum>x\<in>A. of_int(f x))"
```
```  1000   by (induct A rule: infinite_finite_induct) auto
```
```  1001
```
```  1002 lemma of_nat_prod [simp]: "of_nat (prod f A) = (\<Prod>x\<in>A. of_nat(f x))"
```
```  1003   by (induct A rule: infinite_finite_induct) auto
```
```  1004
```
```  1005 lemma of_int_prod [simp]: "of_int (prod f A) = (\<Prod>x\<in>A. of_int(f x))"
```
```  1006   by (induct A rule: infinite_finite_induct) auto
```
```  1007
```
```  1008
```
```  1009 text \<open>Legacy theorems\<close>
```
```  1010
```
```  1011 lemmas int_sum = of_nat_sum [where 'a=int]
```
```  1012 lemmas int_prod = of_nat_prod [where 'a=int]
```
```  1013 lemmas zle_int = of_nat_le_iff [where 'a=int]
```
```  1014 lemmas int_int_eq = of_nat_eq_iff [where 'a=int]
```
```  1015 lemmas nonneg_eq_int = nonneg_int_cases
```
```  1016
```
```  1017
```
```  1018 subsection \<open>Setting up simplification procedures\<close>
```
```  1019
```
```  1020 lemmas of_int_simps =
```
```  1021   of_int_0 of_int_1 of_int_add of_int_mult
```
```  1022
```
```  1023 ML_file "Tools/int_arith.ML"
```
```  1024 declaration \<open>K Int_Arith.setup\<close>
```
```  1025
```
```  1026 simproc_setup fast_arith
```
```  1027   ("(m::'a::linordered_idom) < n" |
```
```  1028     "(m::'a::linordered_idom) \<le> n" |
```
```  1029     "(m::'a::linordered_idom) = n") =
```
```  1030   \<open>K Lin_Arith.simproc\<close>
```
```  1031
```
```  1032
```
```  1033 subsection\<open>More Inequality Reasoning\<close>
```
```  1034
```
```  1035 lemma zless_add1_eq: "w < z + 1 \<longleftrightarrow> w < z \<or> w = z"
```
```  1036   for w z :: int
```
```  1037   by arith
```
```  1038
```
```  1039 lemma add1_zle_eq: "w + 1 \<le> z \<longleftrightarrow> w < z"
```
```  1040   for w z :: int
```
```  1041   by arith
```
```  1042
```
```  1043 lemma zle_diff1_eq [simp]: "w \<le> z - 1 \<longleftrightarrow> w < z"
```
```  1044   for w z :: int
```
```  1045   by arith
```
```  1046
```
```  1047 lemma zle_add1_eq_le [simp]: "w < z + 1 \<longleftrightarrow> w \<le> z"
```
```  1048   for w z :: int
```
```  1049   by arith
```
```  1050
```
```  1051 lemma int_one_le_iff_zero_less: "1 \<le> z \<longleftrightarrow> 0 < z"
```
```  1052   for z :: int
```
```  1053   by arith
```
```  1054
```
```  1055 lemma Ints_nonzero_abs_ge1:
```
```  1056   fixes x:: "'a :: linordered_idom"
```
```  1057     assumes "x \<in> Ints" "x \<noteq> 0"
```
```  1058     shows "1 \<le> abs x"
```
```  1059 proof (rule Ints_cases [OF \<open>x \<in> Ints\<close>])
```
```  1060   fix z::int
```
```  1061   assume "x = of_int z"
```
```  1062     with \<open>x \<noteq> 0\<close>
```
```  1063   show "1 \<le> \<bar>x\<bar>"
```
```  1064     apply (auto simp add: abs_if)
```
```  1065     by (metis diff_0 of_int_1 of_int_le_iff of_int_minus zle_diff1_eq)
```
```  1066 qed
```
```  1067
```
```  1068 lemma Ints_nonzero_abs_less1:
```
```  1069   fixes x:: "'a :: linordered_idom"
```
```  1070   shows "\<lbrakk>x \<in> Ints; abs x < 1\<rbrakk> \<Longrightarrow> x = 0"
```
```  1071     using Ints_nonzero_abs_ge1 [of x] by auto
```
```  1072
```
```  1073
```
```  1074 subsection \<open>The functions @{term nat} and @{term int}\<close>
```
```  1075
```
```  1076 text \<open>Simplify the term @{term "w + - z"}.\<close>
```
```  1077
```
```  1078 lemma one_less_nat_eq [simp]: "Suc 0 < nat z \<longleftrightarrow> 1 < z"
```
```  1079   using zless_nat_conj [of 1 z] by auto
```
```  1080
```
```  1081 text \<open>
```
```  1082   This simplifies expressions of the form @{term "int n = z"} where
```
```  1083   \<open>z\<close> is an integer literal.
```
```  1084 \<close>
```
```  1085 lemmas int_eq_iff_numeral [simp] = int_eq_iff [of _ "numeral v"] for v
```
```  1086
```
```  1087 lemma nat_abs_int_diff: "nat \<bar>int a - int b\<bar> = (if a \<le> b then b - a else a - b)"
```
```  1088   by auto
```
```  1089
```
```  1090 lemma nat_int_add: "nat (int a + int b) = a + b"
```
```  1091   by auto
```
```  1092
```
```  1093 context ring_1
```
```  1094 begin
```
```  1095
```
```  1096 lemma of_int_of_nat [nitpick_simp]:
```
```  1097   "of_int k = (if k < 0 then - of_nat (nat (- k)) else of_nat (nat k))"
```
```  1098 proof (cases "k < 0")
```
```  1099   case True
```
```  1100   then have "0 \<le> - k" by simp
```
```  1101   then have "of_nat (nat (- k)) = of_int (- k)" by (rule of_nat_nat)
```
```  1102   with True show ?thesis by simp
```
```  1103 next
```
```  1104   case False
```
```  1105   then show ?thesis by (simp add: not_less)
```
```  1106 qed
```
```  1107
```
```  1108 end
```
```  1109
```
```  1110 lemma transfer_rule_of_int:
```
```  1111   fixes R :: "'a::ring_1 \<Rightarrow> 'b::ring_1 \<Rightarrow> bool"
```
```  1112   assumes [transfer_rule]: "R 0 0" "R 1 1"
```
```  1113     "rel_fun R (rel_fun R R) plus plus"
```
```  1114     "rel_fun R R uminus uminus"
```
```  1115   shows "rel_fun HOL.eq R of_int of_int"
```
```  1116 proof -
```
```  1117   note transfer_rule_of_nat [transfer_rule]
```
```  1118   have [transfer_rule]: "rel_fun HOL.eq R of_nat of_nat"
```
```  1119     by transfer_prover
```
```  1120   show ?thesis
```
```  1121     by (unfold of_int_of_nat [abs_def]) transfer_prover
```
```  1122 qed
```
```  1123
```
```  1124 lemma nat_mult_distrib:
```
```  1125   fixes z z' :: int
```
```  1126   assumes "0 \<le> z"
```
```  1127   shows "nat (z * z') = nat z * nat z'"
```
```  1128 proof (cases "0 \<le> z'")
```
```  1129   case False
```
```  1130   with assms have "z * z' \<le> 0"
```
```  1131     by (simp add: not_le mult_le_0_iff)
```
```  1132   then have "nat (z * z') = 0" by simp
```
```  1133   moreover from False have "nat z' = 0" by simp
```
```  1134   ultimately show ?thesis by simp
```
```  1135 next
```
```  1136   case True
```
```  1137   with assms have ge_0: "z * z' \<ge> 0" by (simp add: zero_le_mult_iff)
```
```  1138   show ?thesis
```
```  1139     by (rule injD [of "of_nat :: nat \<Rightarrow> int", OF inj_of_nat])
```
```  1140       (simp only: of_nat_mult of_nat_nat [OF True]
```
```  1141          of_nat_nat [OF assms] of_nat_nat [OF ge_0], simp)
```
```  1142 qed
```
```  1143
```
```  1144 lemma nat_mult_distrib_neg: "z \<le> 0 \<Longrightarrow> nat (z * z') = nat (- z) * nat (- z')"
```
```  1145   for z z' :: int
```
```  1146   apply (rule trans)
```
```  1147    apply (rule_tac  nat_mult_distrib)
```
```  1148    apply auto
```
```  1149   done
```
```  1150
```
```  1151 lemma nat_abs_mult_distrib: "nat \<bar>w * z\<bar> = nat \<bar>w\<bar> * nat \<bar>z\<bar>"
```
```  1152   by (cases "z = 0 \<or> w = 0")
```
```  1153     (auto simp add: abs_if nat_mult_distrib [symmetric]
```
```  1154       nat_mult_distrib_neg [symmetric] mult_less_0_iff)
```
```  1155
```
```  1156 lemma int_in_range_abs [simp]: "int n \<in> range abs"
```
```  1157 proof (rule range_eqI)
```
```  1158   show "int n = \<bar>int n\<bar>" by simp
```
```  1159 qed
```
```  1160
```
```  1161 lemma range_abs_Nats [simp]: "range abs = (\<nat> :: int set)"
```
```  1162 proof -
```
```  1163   have "\<bar>k\<bar> \<in> \<nat>" for k :: int
```
```  1164     by (cases k) simp_all
```
```  1165   moreover have "k \<in> range abs" if "k \<in> \<nat>" for k :: int
```
```  1166     using that by induct simp
```
```  1167   ultimately show ?thesis by blast
```
```  1168 qed
```
```  1169
```
```  1170 lemma Suc_nat_eq_nat_zadd1: "0 \<le> z \<Longrightarrow> Suc (nat z) = nat (1 + z)"
```
```  1171   for z :: int
```
```  1172   by (rule sym) (simp add: nat_eq_iff)
```
```  1173
```
```  1174 lemma diff_nat_eq_if:
```
```  1175   "nat z - nat z' =
```
```  1176     (if z' < 0 then nat z
```
```  1177      else
```
```  1178       let d = z - z'
```
```  1179       in if d < 0 then 0 else nat d)"
```
```  1180   by (simp add: Let_def nat_diff_distrib [symmetric])
```
```  1181
```
```  1182 lemma nat_numeral_diff_1 [simp]: "numeral v - (1::nat) = nat (numeral v - 1)"
```
```  1183   using diff_nat_numeral [of v Num.One] by simp
```
```  1184
```
```  1185
```
```  1186 subsection \<open>Induction principles for int\<close>
```
```  1187
```
```  1188 text \<open>Well-founded segments of the integers.\<close>
```
```  1189
```
```  1190 definition int_ge_less_than :: "int \<Rightarrow> (int \<times> int) set"
```
```  1191   where "int_ge_less_than d = {(z', z). d \<le> z' \<and> z' < z}"
```
```  1192
```
```  1193 lemma wf_int_ge_less_than: "wf (int_ge_less_than d)"
```
```  1194 proof -
```
```  1195   have "int_ge_less_than d \<subseteq> measure (\<lambda>z. nat (z - d))"
```
```  1196     by (auto simp add: int_ge_less_than_def)
```
```  1197   then show ?thesis
```
```  1198     by (rule wf_subset [OF wf_measure])
```
```  1199 qed
```
```  1200
```
```  1201 text \<open>
```
```  1202   This variant looks odd, but is typical of the relations suggested
```
```  1203   by RankFinder.\<close>
```
```  1204
```
```  1205 definition int_ge_less_than2 :: "int \<Rightarrow> (int \<times> int) set"
```
```  1206   where "int_ge_less_than2 d = {(z',z). d \<le> z \<and> z' < z}"
```
```  1207
```
```  1208 lemma wf_int_ge_less_than2: "wf (int_ge_less_than2 d)"
```
```  1209 proof -
```
```  1210   have "int_ge_less_than2 d \<subseteq> measure (\<lambda>z. nat (1 + z - d))"
```
```  1211     by (auto simp add: int_ge_less_than2_def)
```
```  1212   then show ?thesis
```
```  1213     by (rule wf_subset [OF wf_measure])
```
```  1214 qed
```
```  1215
```
```  1216 (* `set:int': dummy construction *)
```
```  1217 theorem int_ge_induct [case_names base step, induct set: int]:
```
```  1218   fixes i :: int
```
```  1219   assumes ge: "k \<le> i"
```
```  1220     and base: "P k"
```
```  1221     and step: "\<And>i. k \<le> i \<Longrightarrow> P i \<Longrightarrow> P (i + 1)"
```
```  1222   shows "P i"
```
```  1223 proof -
```
```  1224   have "\<And>i::int. n = nat (i - k) \<Longrightarrow> k \<le> i \<Longrightarrow> P i" for n
```
```  1225   proof (induct n)
```
```  1226     case 0
```
```  1227     then have "i = k" by arith
```
```  1228     with base show "P i" by simp
```
```  1229   next
```
```  1230     case (Suc n)
```
```  1231     then have "n = nat ((i - 1) - k)" by arith
```
```  1232     moreover have k: "k \<le> i - 1" using Suc.prems by arith
```
```  1233     ultimately have "P (i - 1)" by (rule Suc.hyps)
```
```  1234     from step [OF k this] show ?case by simp
```
```  1235   qed
```
```  1236   with ge show ?thesis by fast
```
```  1237 qed
```
```  1238
```
```  1239 (* `set:int': dummy construction *)
```
```  1240 theorem int_gr_induct [case_names base step, induct set: int]:
```
```  1241   fixes i k :: int
```
```  1242   assumes gr: "k < i"
```
```  1243     and base: "P (k + 1)"
```
```  1244     and step: "\<And>i. k < i \<Longrightarrow> P i \<Longrightarrow> P (i + 1)"
```
```  1245   shows "P i"
```
```  1246   apply (rule int_ge_induct[of "k + 1"])
```
```  1247   using gr apply arith
```
```  1248    apply (rule base)
```
```  1249   apply (rule step)
```
```  1250    apply simp_all
```
```  1251   done
```
```  1252
```
```  1253 theorem int_le_induct [consumes 1, case_names base step]:
```
```  1254   fixes i k :: int
```
```  1255   assumes le: "i \<le> k"
```
```  1256     and base: "P k"
```
```  1257     and step: "\<And>i. i \<le> k \<Longrightarrow> P i \<Longrightarrow> P (i - 1)"
```
```  1258   shows "P i"
```
```  1259 proof -
```
```  1260   have "\<And>i::int. n = nat(k-i) \<Longrightarrow> i \<le> k \<Longrightarrow> P i" for n
```
```  1261   proof (induct n)
```
```  1262     case 0
```
```  1263     then have "i = k" by arith
```
```  1264     with base show "P i" by simp
```
```  1265   next
```
```  1266     case (Suc n)
```
```  1267     then have "n = nat (k - (i + 1))" by arith
```
```  1268     moreover have k: "i + 1 \<le> k" using Suc.prems by arith
```
```  1269     ultimately have "P (i + 1)" by (rule Suc.hyps)
```
```  1270     from step[OF k this] show ?case by simp
```
```  1271   qed
```
```  1272   with le show ?thesis by fast
```
```  1273 qed
```
```  1274
```
```  1275 theorem int_less_induct [consumes 1, case_names base step]:
```
```  1276   fixes i k :: int
```
```  1277   assumes less: "i < k"
```
```  1278     and base: "P (k - 1)"
```
```  1279     and step: "\<And>i. i < k \<Longrightarrow> P i \<Longrightarrow> P (i - 1)"
```
```  1280   shows "P i"
```
```  1281   apply (rule int_le_induct[of _ "k - 1"])
```
```  1282   using less apply arith
```
```  1283    apply (rule base)
```
```  1284   apply (rule step)
```
```  1285    apply simp_all
```
```  1286   done
```
```  1287
```
```  1288 theorem int_induct [case_names base step1 step2]:
```
```  1289   fixes k :: int
```
```  1290   assumes base: "P k"
```
```  1291     and step1: "\<And>i. k \<le> i \<Longrightarrow> P i \<Longrightarrow> P (i + 1)"
```
```  1292     and step2: "\<And>i. k \<ge> i \<Longrightarrow> P i \<Longrightarrow> P (i - 1)"
```
```  1293   shows "P i"
```
```  1294 proof -
```
```  1295   have "i \<le> k \<or> i \<ge> k" by arith
```
```  1296   then show ?thesis
```
```  1297   proof
```
```  1298     assume "i \<ge> k"
```
```  1299     then show ?thesis
```
```  1300       using base by (rule int_ge_induct) (fact step1)
```
```  1301   next
```
```  1302     assume "i \<le> k"
```
```  1303     then show ?thesis
```
```  1304       using base by (rule int_le_induct) (fact step2)
```
```  1305   qed
```
```  1306 qed
```
```  1307
```
```  1308
```
```  1309 subsection \<open>Intermediate value theorems\<close>
```
```  1310
```
```  1311 lemma int_val_lemma: "(\<forall>i<n. \<bar>f (i + 1) - f i\<bar> \<le> 1) \<longrightarrow> f 0 \<le> k \<longrightarrow> k \<le> f n \<longrightarrow> (\<exists>i \<le> n. f i = k)"
```
```  1312   for n :: nat and k :: int
```
```  1313   unfolding One_nat_def
```
```  1314   apply (induct n)
```
```  1315    apply simp
```
```  1316   apply (intro strip)
```
```  1317   apply (erule impE)
```
```  1318    apply simp
```
```  1319   apply (erule_tac x = n in allE)
```
```  1320   apply simp
```
```  1321   apply (case_tac "k = f (Suc n)")
```
```  1322    apply force
```
```  1323   apply (erule impE)
```
```  1324    apply (simp add: abs_if split: if_split_asm)
```
```  1325   apply (blast intro: le_SucI)
```
```  1326   done
```
```  1327
```
```  1328 lemmas nat0_intermed_int_val = int_val_lemma [rule_format (no_asm)]
```
```  1329
```
```  1330 lemma nat_intermed_int_val:
```
```  1331   "\<forall>i. m \<le> i \<and> i < n \<longrightarrow> \<bar>f (i + 1) - f i\<bar> \<le> 1 \<Longrightarrow> m < n \<Longrightarrow>
```
```  1332     f m \<le> k \<Longrightarrow> k \<le> f n \<Longrightarrow> \<exists>i. m \<le> i \<and> i \<le> n \<and> f i = k"
```
```  1333     for f :: "nat \<Rightarrow> int" and k :: int
```
```  1334   apply (cut_tac n = "n-m" and f = "\<lambda>i. f (i + m)" and k = k in int_val_lemma)
```
```  1335   unfolding One_nat_def
```
```  1336   apply simp
```
```  1337   apply (erule exE)
```
```  1338   apply (rule_tac x = "i+m" in exI)
```
```  1339   apply arith
```
```  1340   done
```
```  1341
```
```  1342
```
```  1343 subsection \<open>Products and 1, by T. M. Rasmussen\<close>
```
```  1344
```
```  1345 lemma abs_zmult_eq_1:
```
```  1346   fixes m n :: int
```
```  1347   assumes mn: "\<bar>m * n\<bar> = 1"
```
```  1348   shows "\<bar>m\<bar> = 1"
```
```  1349 proof -
```
```  1350   from mn have 0: "m \<noteq> 0" "n \<noteq> 0" by auto
```
```  1351   have "\<not> 2 \<le> \<bar>m\<bar>"
```
```  1352   proof
```
```  1353     assume "2 \<le> \<bar>m\<bar>"
```
```  1354     then have "2 * \<bar>n\<bar> \<le> \<bar>m\<bar> * \<bar>n\<bar>" by (simp add: mult_mono 0)
```
```  1355     also have "\<dots> = \<bar>m * n\<bar>" by (simp add: abs_mult)
```
```  1356     also from mn have "\<dots> = 1" by simp
```
```  1357     finally have "2 * \<bar>n\<bar> \<le> 1" .
```
```  1358     with 0 show "False" by arith
```
```  1359   qed
```
```  1360   with 0 show ?thesis by auto
```
```  1361 qed
```
```  1362
```
```  1363 lemma pos_zmult_eq_1_iff_lemma: "m * n = 1 \<Longrightarrow> m = 1 \<or> m = - 1"
```
```  1364   for m n :: int
```
```  1365   using abs_zmult_eq_1 [of m n] by arith
```
```  1366
```
```  1367 lemma pos_zmult_eq_1_iff:
```
```  1368   fixes m n :: int
```
```  1369   assumes "0 < m"
```
```  1370   shows "m * n = 1 \<longleftrightarrow> m = 1 \<and> n = 1"
```
```  1371 proof -
```
```  1372   from assms have "m * n = 1 \<Longrightarrow> m = 1"
```
```  1373     by (auto dest: pos_zmult_eq_1_iff_lemma)
```
```  1374   then show ?thesis
```
```  1375     by (auto dest: pos_zmult_eq_1_iff_lemma)
```
```  1376 qed
```
```  1377
```
```  1378 lemma zmult_eq_1_iff: "m * n = 1 \<longleftrightarrow> (m = 1 \<and> n = 1) \<or> (m = - 1 \<and> n = - 1)"
```
```  1379   for m n :: int
```
```  1380   apply (rule iffI)
```
```  1381    apply (frule pos_zmult_eq_1_iff_lemma)
```
```  1382    apply (simp add: mult.commute [of m])
```
```  1383    apply (frule pos_zmult_eq_1_iff_lemma)
```
```  1384    apply auto
```
```  1385   done
```
```  1386
```
```  1387 lemma infinite_UNIV_int: "\<not> finite (UNIV::int set)"
```
```  1388 proof
```
```  1389   assume "finite (UNIV::int set)"
```
```  1390   moreover have "inj (\<lambda>i::int. 2 * i)"
```
```  1391     by (rule injI) simp
```
```  1392   ultimately have "surj (\<lambda>i::int. 2 * i)"
```
```  1393     by (rule finite_UNIV_inj_surj)
```
```  1394   then obtain i :: int where "1 = 2 * i" by (rule surjE)
```
```  1395   then show False by (simp add: pos_zmult_eq_1_iff)
```
```  1396 qed
```
```  1397
```
```  1398
```
```  1399 subsection \<open>Further theorems on numerals\<close>
```
```  1400
```
```  1401 subsubsection \<open>Special Simplification for Constants\<close>
```
```  1402
```
```  1403 text \<open>These distributive laws move literals inside sums and differences.\<close>
```
```  1404
```
```  1405 lemmas distrib_right_numeral [simp] = distrib_right [of _ _ "numeral v"] for v
```
```  1406 lemmas distrib_left_numeral [simp] = distrib_left [of "numeral v"] for v
```
```  1407 lemmas left_diff_distrib_numeral [simp] = left_diff_distrib [of _ _ "numeral v"] for v
```
```  1408 lemmas right_diff_distrib_numeral [simp] = right_diff_distrib [of "numeral v"] for v
```
```  1409
```
```  1410 text \<open>These are actually for fields, like real: but where else to put them?\<close>
```
```  1411
```
```  1412 lemmas zero_less_divide_iff_numeral [simp, no_atp] = zero_less_divide_iff [of "numeral w"] for w
```
```  1413 lemmas divide_less_0_iff_numeral [simp, no_atp] = divide_less_0_iff [of "numeral w"] for w
```
```  1414 lemmas zero_le_divide_iff_numeral [simp, no_atp] = zero_le_divide_iff [of "numeral w"] for w
```
```  1415 lemmas divide_le_0_iff_numeral [simp, no_atp] = divide_le_0_iff [of "numeral w"] for w
```
```  1416
```
```  1417
```
```  1418 text \<open>Replaces \<open>inverse #nn\<close> by \<open>1/#nn\<close>.  It looks
```
```  1419   strange, but then other simprocs simplify the quotient.\<close>
```
```  1420
```
```  1421 lemmas inverse_eq_divide_numeral [simp] =
```
```  1422   inverse_eq_divide [of "numeral w"] for w
```
```  1423
```
```  1424 lemmas inverse_eq_divide_neg_numeral [simp] =
```
```  1425   inverse_eq_divide [of "- numeral w"] for w
```
```  1426
```
```  1427 text \<open>These laws simplify inequalities, moving unary minus from a term
```
```  1428   into the literal.\<close>
```
```  1429
```
```  1430 lemmas equation_minus_iff_numeral [no_atp] =
```
```  1431   equation_minus_iff [of "numeral v"] for v
```
```  1432
```
```  1433 lemmas minus_equation_iff_numeral [no_atp] =
```
```  1434   minus_equation_iff [of _ "numeral v"] for v
```
```  1435
```
```  1436 lemmas le_minus_iff_numeral [no_atp] =
```
```  1437   le_minus_iff [of "numeral v"] for v
```
```  1438
```
```  1439 lemmas minus_le_iff_numeral [no_atp] =
```
```  1440   minus_le_iff [of _ "numeral v"] for v
```
```  1441
```
```  1442 lemmas less_minus_iff_numeral [no_atp] =
```
```  1443   less_minus_iff [of "numeral v"] for v
```
```  1444
```
```  1445 lemmas minus_less_iff_numeral [no_atp] =
```
```  1446   minus_less_iff [of _ "numeral v"] for v
```
```  1447
```
```  1448 (* FIXME maybe simproc *)
```
```  1449
```
```  1450
```
```  1451 text \<open>Cancellation of constant factors in comparisons (\<open><\<close> and \<open>\<le>\<close>)\<close>
```
```  1452
```
```  1453 lemmas mult_less_cancel_left_numeral [simp, no_atp] = mult_less_cancel_left [of "numeral v"] for v
```
```  1454 lemmas mult_less_cancel_right_numeral [simp, no_atp] = mult_less_cancel_right [of _ "numeral v"] for v
```
```  1455 lemmas mult_le_cancel_left_numeral [simp, no_atp] = mult_le_cancel_left [of "numeral v"] for v
```
```  1456 lemmas mult_le_cancel_right_numeral [simp, no_atp] = mult_le_cancel_right [of _ "numeral v"] for v
```
```  1457
```
```  1458
```
```  1459 text \<open>Multiplying out constant divisors in comparisons (\<open><\<close>, \<open>\<le>\<close> and \<open>=\<close>)\<close>
```
```  1460
```
```  1461 named_theorems divide_const_simps "simplification rules to simplify comparisons involving constant divisors"
```
```  1462
```
```  1463 lemmas le_divide_eq_numeral1 [simp,divide_const_simps] =
```
```  1464   pos_le_divide_eq [of "numeral w", OF zero_less_numeral]
```
```  1465   neg_le_divide_eq [of "- numeral w", OF neg_numeral_less_zero] for w
```
```  1466
```
```  1467 lemmas divide_le_eq_numeral1 [simp,divide_const_simps] =
```
```  1468   pos_divide_le_eq [of "numeral w", OF zero_less_numeral]
```
```  1469   neg_divide_le_eq [of "- numeral w", OF neg_numeral_less_zero] for w
```
```  1470
```
```  1471 lemmas less_divide_eq_numeral1 [simp,divide_const_simps] =
```
```  1472   pos_less_divide_eq [of "numeral w", OF zero_less_numeral]
```
```  1473   neg_less_divide_eq [of "- numeral w", OF neg_numeral_less_zero] for w
```
```  1474
```
```  1475 lemmas divide_less_eq_numeral1 [simp,divide_const_simps] =
```
```  1476   pos_divide_less_eq [of "numeral w", OF zero_less_numeral]
```
```  1477   neg_divide_less_eq [of "- numeral w", OF neg_numeral_less_zero] for w
```
```  1478
```
```  1479 lemmas eq_divide_eq_numeral1 [simp,divide_const_simps] =
```
```  1480   eq_divide_eq [of _ _ "numeral w"]
```
```  1481   eq_divide_eq [of _ _ "- numeral w"] for w
```
```  1482
```
```  1483 lemmas divide_eq_eq_numeral1 [simp,divide_const_simps] =
```
```  1484   divide_eq_eq [of _ "numeral w"]
```
```  1485   divide_eq_eq [of _ "- numeral w"] for w
```
```  1486
```
```  1487
```
```  1488 subsubsection \<open>Optional Simplification Rules Involving Constants\<close>
```
```  1489
```
```  1490 text \<open>Simplify quotients that are compared with a literal constant.\<close>
```
```  1491
```
```  1492 lemmas le_divide_eq_numeral [divide_const_simps] =
```
```  1493   le_divide_eq [of "numeral w"]
```
```  1494   le_divide_eq [of "- numeral w"] for w
```
```  1495
```
```  1496 lemmas divide_le_eq_numeral [divide_const_simps] =
```
```  1497   divide_le_eq [of _ _ "numeral w"]
```
```  1498   divide_le_eq [of _ _ "- numeral w"] for w
```
```  1499
```
```  1500 lemmas less_divide_eq_numeral [divide_const_simps] =
```
```  1501   less_divide_eq [of "numeral w"]
```
```  1502   less_divide_eq [of "- numeral w"] for w
```
```  1503
```
```  1504 lemmas divide_less_eq_numeral [divide_const_simps] =
```
```  1505   divide_less_eq [of _ _ "numeral w"]
```
```  1506   divide_less_eq [of _ _ "- numeral w"] for w
```
```  1507
```
```  1508 lemmas eq_divide_eq_numeral [divide_const_simps] =
```
```  1509   eq_divide_eq [of "numeral w"]
```
```  1510   eq_divide_eq [of "- numeral w"] for w
```
```  1511
```
```  1512 lemmas divide_eq_eq_numeral [divide_const_simps] =
```
```  1513   divide_eq_eq [of _ _ "numeral w"]
```
```  1514   divide_eq_eq [of _ _ "- numeral w"] for w
```
```  1515
```
```  1516
```
```  1517 text \<open>Not good as automatic simprules because they cause case splits.\<close>
```
```  1518 lemmas [divide_const_simps] =
```
```  1519   le_divide_eq_1 divide_le_eq_1 less_divide_eq_1 divide_less_eq_1
```
```  1520
```
```  1521
```
```  1522 subsection \<open>The divides relation\<close>
```
```  1523
```
```  1524 lemma zdvd_antisym_nonneg: "0 \<le> m \<Longrightarrow> 0 \<le> n \<Longrightarrow> m dvd n \<Longrightarrow> n dvd m \<Longrightarrow> m = n"
```
```  1525   for m n :: int
```
```  1526   by (auto simp add: dvd_def mult.assoc zero_le_mult_iff zmult_eq_1_iff)
```
```  1527
```
```  1528 lemma zdvd_antisym_abs:
```
```  1529   fixes a b :: int
```
```  1530   assumes "a dvd b" and "b dvd a"
```
```  1531   shows "\<bar>a\<bar> = \<bar>b\<bar>"
```
```  1532 proof (cases "a = 0")
```
```  1533   case True
```
```  1534   with assms show ?thesis by simp
```
```  1535 next
```
```  1536   case False
```
```  1537   from \<open>a dvd b\<close> obtain k where k: "b = a * k"
```
```  1538     unfolding dvd_def by blast
```
```  1539   from \<open>b dvd a\<close> obtain k' where k': "a = b * k'"
```
```  1540     unfolding dvd_def by blast
```
```  1541   from k k' have "a = a * k * k'" by simp
```
```  1542   with mult_cancel_left1[where c="a" and b="k*k'"] have kk': "k * k' = 1"
```
```  1543     using \<open>a \<noteq> 0\<close> by (simp add: mult.assoc)
```
```  1544   then have "k = 1 \<and> k' = 1 \<or> k = -1 \<and> k' = -1"
```
```  1545     by (simp add: zmult_eq_1_iff)
```
```  1546   with k k' show ?thesis by auto
```
```  1547 qed
```
```  1548
```
```  1549 lemma zdvd_zdiffD: "k dvd m - n \<Longrightarrow> k dvd n \<Longrightarrow> k dvd m"
```
```  1550   for k m n :: int
```
```  1551   using dvd_add_right_iff [of k "- n" m] by simp
```
```  1552
```
```  1553 lemma zdvd_reduce: "k dvd n + k * m \<longleftrightarrow> k dvd n"
```
```  1554   for k m n :: int
```
```  1555   using dvd_add_times_triv_right_iff [of k n m] by (simp add: ac_simps)
```
```  1556
```
```  1557 lemma dvd_imp_le_int:
```
```  1558   fixes d i :: int
```
```  1559   assumes "i \<noteq> 0" and "d dvd i"
```
```  1560   shows "\<bar>d\<bar> \<le> \<bar>i\<bar>"
```
```  1561 proof -
```
```  1562   from \<open>d dvd i\<close> obtain k where "i = d * k" ..
```
```  1563   with \<open>i \<noteq> 0\<close> have "k \<noteq> 0" by auto
```
```  1564   then have "1 \<le> \<bar>k\<bar>" and "0 \<le> \<bar>d\<bar>" by auto
```
```  1565   then have "\<bar>d\<bar> * 1 \<le> \<bar>d\<bar> * \<bar>k\<bar>" by (rule mult_left_mono)
```
```  1566   with \<open>i = d * k\<close> show ?thesis by (simp add: abs_mult)
```
```  1567 qed
```
```  1568
```
```  1569 lemma zdvd_not_zless:
```
```  1570   fixes m n :: int
```
```  1571   assumes "0 < m" and "m < n"
```
```  1572   shows "\<not> n dvd m"
```
```  1573 proof
```
```  1574   from assms have "0 < n" by auto
```
```  1575   assume "n dvd m" then obtain k where k: "m = n * k" ..
```
```  1576   with \<open>0 < m\<close> have "0 < n * k" by auto
```
```  1577   with \<open>0 < n\<close> have "0 < k" by (simp add: zero_less_mult_iff)
```
```  1578   with k \<open>0 < n\<close> \<open>m < n\<close> have "n * k < n * 1" by simp
```
```  1579   with \<open>0 < n\<close> \<open>0 < k\<close> show False unfolding mult_less_cancel_left by auto
```
```  1580 qed
```
```  1581
```
```  1582 lemma zdvd_mult_cancel:
```
```  1583   fixes k m n :: int
```
```  1584   assumes d: "k * m dvd k * n"
```
```  1585     and "k \<noteq> 0"
```
```  1586   shows "m dvd n"
```
```  1587 proof -
```
```  1588   from d obtain h where h: "k * n = k * m * h"
```
```  1589     unfolding dvd_def by blast
```
```  1590   have "n = m * h"
```
```  1591   proof (rule ccontr)
```
```  1592     assume "\<not> ?thesis"
```
```  1593     with \<open>k \<noteq> 0\<close> have "k * n \<noteq> k * (m * h)" by simp
```
```  1594     with h show False
```
```  1595       by (simp add: mult.assoc)
```
```  1596   qed
```
```  1597   then show ?thesis by simp
```
```  1598 qed
```
```  1599
```
```  1600 theorem zdvd_int: "x dvd y \<longleftrightarrow> int x dvd int y"
```
```  1601 proof -
```
```  1602   have "x dvd y" if "int y = int x * k" for k
```
```  1603   proof (cases k)
```
```  1604     case (nonneg n)
```
```  1605     with that have "y = x * n"
```
```  1606       by (simp del: of_nat_mult add: of_nat_mult [symmetric])
```
```  1607     then show ?thesis ..
```
```  1608   next
```
```  1609     case (neg n)
```
```  1610     with that have "int y = int x * (- int (Suc n))"
```
```  1611       by simp
```
```  1612     also have "\<dots> = - (int x * int (Suc n))"
```
```  1613       by (simp only: mult_minus_right)
```
```  1614     also have "\<dots> = - int (x * Suc n)"
```
```  1615       by (simp only: of_nat_mult [symmetric])
```
```  1616     finally have "- int (x * Suc n) = int y" ..
```
```  1617     then show ?thesis
```
```  1618       by (simp only: negative_eq_positive) auto
```
```  1619   qed
```
```  1620   then show ?thesis
```
```  1621     by (auto elim!: dvdE simp only: dvd_triv_left of_nat_mult)
```
```  1622 qed
```
```  1623
```
```  1624 lemma zdvd1_eq[simp]: "x dvd 1 \<longleftrightarrow> \<bar>x\<bar> = 1"
```
```  1625   (is "?lhs \<longleftrightarrow> ?rhs")
```
```  1626   for x :: int
```
```  1627 proof
```
```  1628   assume ?lhs
```
```  1629   then have "int (nat \<bar>x\<bar>) dvd int (nat 1)" by simp
```
```  1630   then have "nat \<bar>x\<bar> dvd 1" by (simp add: zdvd_int)
```
```  1631   then have "nat \<bar>x\<bar> = 1" by simp
```
```  1632   then show ?rhs by (cases "x < 0") auto
```
```  1633 next
```
```  1634   assume ?rhs
```
```  1635   then have "x = 1 \<or> x = - 1" by auto
```
```  1636   then show ?lhs by (auto intro: dvdI)
```
```  1637 qed
```
```  1638
```
```  1639 lemma zdvd_mult_cancel1:
```
```  1640   fixes m :: int
```
```  1641   assumes mp: "m \<noteq> 0"
```
```  1642   shows "m * n dvd m \<longleftrightarrow> \<bar>n\<bar> = 1"
```
```  1643     (is "?lhs \<longleftrightarrow> ?rhs")
```
```  1644 proof
```
```  1645   assume ?rhs
```
```  1646   then show ?lhs
```
```  1647     by (cases "n > 0") (auto simp add: minus_equation_iff)
```
```  1648 next
```
```  1649   assume ?lhs
```
```  1650   then have "m * n dvd m * 1" by simp
```
```  1651   from zdvd_mult_cancel[OF this mp] show ?rhs
```
```  1652     by (simp only: zdvd1_eq)
```
```  1653 qed
```
```  1654
```
```  1655 lemma int_dvd_iff: "int m dvd z \<longleftrightarrow> m dvd nat \<bar>z\<bar>"
```
```  1656   by (cases "z \<ge> 0") (simp_all add: zdvd_int)
```
```  1657
```
```  1658 lemma dvd_int_iff: "z dvd int m \<longleftrightarrow> nat \<bar>z\<bar> dvd m"
```
```  1659   by (cases "z \<ge> 0") (simp_all add: zdvd_int)
```
```  1660
```
```  1661 lemma dvd_int_unfold_dvd_nat: "k dvd l \<longleftrightarrow> nat \<bar>k\<bar> dvd nat \<bar>l\<bar>"
```
```  1662   by (simp add: dvd_int_iff [symmetric])
```
```  1663
```
```  1664 lemma nat_dvd_iff: "nat z dvd m \<longleftrightarrow> (if 0 \<le> z then z dvd int m else m = 0)"
```
```  1665   by (auto simp add: dvd_int_iff)
```
```  1666
```
```  1667 lemma eq_nat_nat_iff: "0 \<le> z \<Longrightarrow> 0 \<le> z' \<Longrightarrow> nat z = nat z' \<longleftrightarrow> z = z'"
```
```  1668   by (auto elim!: nonneg_eq_int)
```
```  1669
```
```  1670 lemma nat_power_eq: "0 \<le> z \<Longrightarrow> nat (z ^ n) = nat z ^ n"
```
```  1671   by (induct n) (simp_all add: nat_mult_distrib)
```
```  1672
```
```  1673 lemma zdvd_imp_le: "z dvd n \<Longrightarrow> 0 < n \<Longrightarrow> z \<le> n"
```
```  1674   for n z :: int
```
```  1675   apply (cases n)
```
```  1676    apply (auto simp add: dvd_int_iff)
```
```  1677   apply (cases z)
```
```  1678    apply (auto simp add: dvd_imp_le)
```
```  1679   done
```
```  1680
```
```  1681 lemma zdvd_period:
```
```  1682   fixes a d :: int
```
```  1683   assumes "a dvd d"
```
```  1684   shows "a dvd (x + t) \<longleftrightarrow> a dvd ((x + c * d) + t)"
```
```  1685     (is "?lhs \<longleftrightarrow> ?rhs")
```
```  1686 proof -
```
```  1687   from assms have "a dvd (x + t) \<longleftrightarrow> a dvd ((x + t) + c * d)"
```
```  1688     by (simp add: dvd_add_left_iff)
```
```  1689   then show ?thesis
```
```  1690     by (simp add: ac_simps)
```
```  1691 qed
```
```  1692
```
```  1693
```
```  1694 subsection \<open>Finiteness of intervals\<close>
```
```  1695
```
```  1696 lemma finite_interval_int1 [iff]: "finite {i :: int. a \<le> i \<and> i \<le> b}"
```
```  1697 proof (cases "a \<le> b")
```
```  1698   case True
```
```  1699   then show ?thesis
```
```  1700   proof (induct b rule: int_ge_induct)
```
```  1701     case base
```
```  1702     have "{i. a \<le> i \<and> i \<le> a} = {a}" by auto
```
```  1703     then show ?case by simp
```
```  1704   next
```
```  1705     case (step b)
```
```  1706     then have "{i. a \<le> i \<and> i \<le> b + 1} = {i. a \<le> i \<and> i \<le> b} \<union> {b + 1}" by auto
```
```  1707     with step show ?case by simp
```
```  1708   qed
```
```  1709 next
```
```  1710   case False
```
```  1711   then show ?thesis
```
```  1712     by (metis (lifting, no_types) Collect_empty_eq finite.emptyI order_trans)
```
```  1713 qed
```
```  1714
```
```  1715 lemma finite_interval_int2 [iff]: "finite {i :: int. a \<le> i \<and> i < b}"
```
```  1716   by (rule rev_finite_subset[OF finite_interval_int1[of "a" "b"]]) auto
```
```  1717
```
```  1718 lemma finite_interval_int3 [iff]: "finite {i :: int. a < i \<and> i \<le> b}"
```
```  1719   by (rule rev_finite_subset[OF finite_interval_int1[of "a" "b"]]) auto
```
```  1720
```
```  1721 lemma finite_interval_int4 [iff]: "finite {i :: int. a < i \<and> i < b}"
```
```  1722   by (rule rev_finite_subset[OF finite_interval_int1[of "a" "b"]]) auto
```
```  1723
```
```  1724
```
```  1725 subsection \<open>Configuration of the code generator\<close>
```
```  1726
```
```  1727 text \<open>Constructors\<close>
```
```  1728
```
```  1729 definition Pos :: "num \<Rightarrow> int"
```
```  1730   where [simp, code_abbrev]: "Pos = numeral"
```
```  1731
```
```  1732 definition Neg :: "num \<Rightarrow> int"
```
```  1733   where [simp, code_abbrev]: "Neg n = - (Pos n)"
```
```  1734
```
```  1735 code_datatype "0::int" Pos Neg
```
```  1736
```
```  1737
```
```  1738 text \<open>Auxiliary operations.\<close>
```
```  1739
```
```  1740 definition dup :: "int \<Rightarrow> int"
```
```  1741   where [simp]: "dup k = k + k"
```
```  1742
```
```  1743 lemma dup_code [code]:
```
```  1744   "dup 0 = 0"
```
```  1745   "dup (Pos n) = Pos (Num.Bit0 n)"
```
```  1746   "dup (Neg n) = Neg (Num.Bit0 n)"
```
```  1747   by (simp_all add: numeral_Bit0)
```
```  1748
```
```  1749 definition sub :: "num \<Rightarrow> num \<Rightarrow> int"
```
```  1750   where [simp]: "sub m n = numeral m - numeral n"
```
```  1751
```
```  1752 lemma sub_code [code]:
```
```  1753   "sub Num.One Num.One = 0"
```
```  1754   "sub (Num.Bit0 m) Num.One = Pos (Num.BitM m)"
```
```  1755   "sub (Num.Bit1 m) Num.One = Pos (Num.Bit0 m)"
```
```  1756   "sub Num.One (Num.Bit0 n) = Neg (Num.BitM n)"
```
```  1757   "sub Num.One (Num.Bit1 n) = Neg (Num.Bit0 n)"
```
```  1758   "sub (Num.Bit0 m) (Num.Bit0 n) = dup (sub m n)"
```
```  1759   "sub (Num.Bit1 m) (Num.Bit1 n) = dup (sub m n)"
```
```  1760   "sub (Num.Bit1 m) (Num.Bit0 n) = dup (sub m n) + 1"
```
```  1761   "sub (Num.Bit0 m) (Num.Bit1 n) = dup (sub m n) - 1"
```
```  1762   by (simp_all only: sub_def dup_def numeral.simps Pos_def Neg_def numeral_BitM)
```
```  1763
```
```  1764 text \<open>Implementations.\<close>
```
```  1765
```
```  1766 lemma one_int_code [code]: "1 = Pos Num.One"
```
```  1767   by simp
```
```  1768
```
```  1769 lemma plus_int_code [code]:
```
```  1770   "k + 0 = k"
```
```  1771   "0 + l = l"
```
```  1772   "Pos m + Pos n = Pos (m + n)"
```
```  1773   "Pos m + Neg n = sub m n"
```
```  1774   "Neg m + Pos n = sub n m"
```
```  1775   "Neg m + Neg n = Neg (m + n)"
```
```  1776   for k l :: int
```
```  1777   by simp_all
```
```  1778
```
```  1779 lemma uminus_int_code [code]:
```
```  1780   "uminus 0 = (0::int)"
```
```  1781   "uminus (Pos m) = Neg m"
```
```  1782   "uminus (Neg m) = Pos m"
```
```  1783   by simp_all
```
```  1784
```
```  1785 lemma minus_int_code [code]:
```
```  1786   "k - 0 = k"
```
```  1787   "0 - l = uminus l"
```
```  1788   "Pos m - Pos n = sub m n"
```
```  1789   "Pos m - Neg n = Pos (m + n)"
```
```  1790   "Neg m - Pos n = Neg (m + n)"
```
```  1791   "Neg m - Neg n = sub n m"
```
```  1792   for k l :: int
```
```  1793   by simp_all
```
```  1794
```
```  1795 lemma times_int_code [code]:
```
```  1796   "k * 0 = 0"
```
```  1797   "0 * l = 0"
```
```  1798   "Pos m * Pos n = Pos (m * n)"
```
```  1799   "Pos m * Neg n = Neg (m * n)"
```
```  1800   "Neg m * Pos n = Neg (m * n)"
```
```  1801   "Neg m * Neg n = Pos (m * n)"
```
```  1802   for k l :: int
```
```  1803   by simp_all
```
```  1804
```
```  1805 instantiation int :: equal
```
```  1806 begin
```
```  1807
```
```  1808 definition "HOL.equal k l \<longleftrightarrow> k = (l::int)"
```
```  1809
```
```  1810 instance
```
```  1811   by standard (rule equal_int_def)
```
```  1812
```
```  1813 end
```
```  1814
```
```  1815 lemma equal_int_code [code]:
```
```  1816   "HOL.equal 0 (0::int) \<longleftrightarrow> True"
```
```  1817   "HOL.equal 0 (Pos l) \<longleftrightarrow> False"
```
```  1818   "HOL.equal 0 (Neg l) \<longleftrightarrow> False"
```
```  1819   "HOL.equal (Pos k) 0 \<longleftrightarrow> False"
```
```  1820   "HOL.equal (Pos k) (Pos l) \<longleftrightarrow> HOL.equal k l"
```
```  1821   "HOL.equal (Pos k) (Neg l) \<longleftrightarrow> False"
```
```  1822   "HOL.equal (Neg k) 0 \<longleftrightarrow> False"
```
```  1823   "HOL.equal (Neg k) (Pos l) \<longleftrightarrow> False"
```
```  1824   "HOL.equal (Neg k) (Neg l) \<longleftrightarrow> HOL.equal k l"
```
```  1825   by (auto simp add: equal)
```
```  1826
```
```  1827 lemma equal_int_refl [code nbe]: "HOL.equal k k \<longleftrightarrow> True"
```
```  1828   for k :: int
```
```  1829   by (fact equal_refl)
```
```  1830
```
```  1831 lemma less_eq_int_code [code]:
```
```  1832   "0 \<le> (0::int) \<longleftrightarrow> True"
```
```  1833   "0 \<le> Pos l \<longleftrightarrow> True"
```
```  1834   "0 \<le> Neg l \<longleftrightarrow> False"
```
```  1835   "Pos k \<le> 0 \<longleftrightarrow> False"
```
```  1836   "Pos k \<le> Pos l \<longleftrightarrow> k \<le> l"
```
```  1837   "Pos k \<le> Neg l \<longleftrightarrow> False"
```
```  1838   "Neg k \<le> 0 \<longleftrightarrow> True"
```
```  1839   "Neg k \<le> Pos l \<longleftrightarrow> True"
```
```  1840   "Neg k \<le> Neg l \<longleftrightarrow> l \<le> k"
```
```  1841   by simp_all
```
```  1842
```
```  1843 lemma less_int_code [code]:
```
```  1844   "0 < (0::int) \<longleftrightarrow> False"
```
```  1845   "0 < Pos l \<longleftrightarrow> True"
```
```  1846   "0 < Neg l \<longleftrightarrow> False"
```
```  1847   "Pos k < 0 \<longleftrightarrow> False"
```
```  1848   "Pos k < Pos l \<longleftrightarrow> k < l"
```
```  1849   "Pos k < Neg l \<longleftrightarrow> False"
```
```  1850   "Neg k < 0 \<longleftrightarrow> True"
```
```  1851   "Neg k < Pos l \<longleftrightarrow> True"
```
```  1852   "Neg k < Neg l \<longleftrightarrow> l < k"
```
```  1853   by simp_all
```
```  1854
```
```  1855 lemma nat_code [code]:
```
```  1856   "nat (Int.Neg k) = 0"
```
```  1857   "nat 0 = 0"
```
```  1858   "nat (Int.Pos k) = nat_of_num k"
```
```  1859   by (simp_all add: nat_of_num_numeral)
```
```  1860
```
```  1861 lemma (in ring_1) of_int_code [code]:
```
```  1862   "of_int (Int.Neg k) = - numeral k"
```
```  1863   "of_int 0 = 0"
```
```  1864   "of_int (Int.Pos k) = numeral k"
```
```  1865   by simp_all
```
```  1866
```
```  1867
```
```  1868 text \<open>Serializer setup.\<close>
```
```  1869
```
```  1870 code_identifier
```
```  1871   code_module Int \<rightharpoonup> (SML) Arith and (OCaml) Arith and (Haskell) Arith
```
```  1872
```
```  1873 quickcheck_params [default_type = int]
```
```  1874
```
```  1875 hide_const (open) Pos Neg sub dup
```
```  1876
```
```  1877
```
```  1878 text \<open>De-register \<open>int\<close> as a quotient type:\<close>
```
```  1879
```
```  1880 lifting_update int.lifting
```
```  1881 lifting_forget int.lifting
```
```  1882
```
```  1883 end
```