diff --git a/src/HOL/Bit_Operations.thy b/src/HOL/Bit_Operations.thy
--- a/src/HOL/Bit_Operations.thy
+++ b/src/HOL/Bit_Operations.thy
@@ -1,3602 +1,3526 @@
 (*  Author:  Florian Haftmann, TUM
 *)
 
 section \<open>Bit operations in suitable algebraic structures\<close>
 
 theory Bit_Operations
   imports Presburger Groups_List
 begin
 
 subsection \<open>Abstract bit structures\<close>
 
 class semiring_bits = semiring_parity +
   assumes bits_induct [case_names stable rec]:
     \<open>(\<And>a. a div 2 = a \<Longrightarrow> P a)
      \<Longrightarrow> (\<And>a b. P a \<Longrightarrow> (of_bool b + 2 * a) div 2 = a \<Longrightarrow> P (of_bool b + 2 * a))
         \<Longrightarrow> P a\<close>
   assumes bits_div_0 [simp]: \<open>0 div a = 0\<close>
     and bits_div_by_1 [simp]: \<open>a div 1 = a\<close>
     and bits_mod_div_trivial [simp]: \<open>a mod b div b = 0\<close>
     and even_succ_div_2 [simp]: \<open>even a \<Longrightarrow> (1 + a) div 2 = a div 2\<close>
     and even_mask_div_iff: \<open>even ((2 ^ m - 1) div 2 ^ n) \<longleftrightarrow> 2 ^ n = 0 \<or> m \<le> n\<close>
     and exp_div_exp_eq: \<open>2 ^ m div 2 ^ n = of_bool (2 ^ m \<noteq> 0 \<and> m \<ge> n) * 2 ^ (m - n)\<close>
     and div_exp_eq: \<open>a div 2 ^ m div 2 ^ n = a div 2 ^ (m + n)\<close>
     and mod_exp_eq: \<open>a mod 2 ^ m mod 2 ^ n = a mod 2 ^ min m n\<close>
     and mult_exp_mod_exp_eq: \<open>m \<le> n \<Longrightarrow> (a * 2 ^ m) mod (2 ^ n) = (a mod 2 ^ (n - m)) * 2 ^ m\<close>
     and div_exp_mod_exp_eq: \<open>a div 2 ^ n mod 2 ^ m = a mod (2 ^ (n + m)) div 2 ^ n\<close>
     and even_mult_exp_div_exp_iff: \<open>even (a * 2 ^ m div 2 ^ n) \<longleftrightarrow> m > n \<or> 2 ^ n = 0 \<or> (m \<le> n \<and> even (a div 2 ^ (n - m)))\<close>
   fixes bit :: \<open>'a \<Rightarrow> nat \<Rightarrow> bool\<close>
   assumes bit_iff_odd: \<open>bit a n \<longleftrightarrow> odd (a div 2 ^ n)\<close>
 begin
 
 text \<open>
   Having \<^const>\<open>bit\<close> as definitional class operation
   takes into account that specific instances can be implemented
   differently wrt. code generation.
 \<close>
 
 lemma bits_div_by_0 [simp]:
   \<open>a div 0 = 0\<close>
   by (metis add_cancel_right_right bits_mod_div_trivial mod_mult_div_eq mult_not_zero)
 
 lemma bits_1_div_2 [simp]:
   \<open>1 div 2 = 0\<close>
   using even_succ_div_2 [of 0] by simp
 
 lemma bits_1_div_exp [simp]:
   \<open>1 div 2 ^ n = of_bool (n = 0)\<close>
   using div_exp_eq [of 1 1] by (cases n) simp_all
 
 lemma even_succ_div_exp [simp]:
   \<open>(1 + a) div 2 ^ n = a div 2 ^ n\<close> if \<open>even a\<close> and \<open>n > 0\<close>
 proof (cases n)
   case 0
   with that show ?thesis
     by simp
 next
   case (Suc n)
   with \<open>even a\<close> have \<open>(1 + a) div 2 ^ Suc n = a div 2 ^ Suc n\<close>
   proof (induction n)
     case 0
     then show ?case
       by simp
   next
     case (Suc n)
     then show ?case
       using div_exp_eq [of _ 1 \<open>Suc n\<close>, symmetric]
       by simp
   qed
   with Suc show ?thesis
     by simp
 qed
 
 lemma even_succ_mod_exp [simp]:
   \<open>(1 + a) mod 2 ^ n = 1 + (a mod 2 ^ n)\<close> if \<open>even a\<close> and \<open>n > 0\<close>
   using div_mult_mod_eq [of \<open>1 + a\<close> \<open>2 ^ n\<close>] that
   apply simp
   by (metis local.add.left_commute local.add_left_cancel local.div_mult_mod_eq)
 
 lemma bits_mod_by_1 [simp]:
   \<open>a mod 1 = 0\<close>
   using div_mult_mod_eq [of a 1] by simp
 
 lemma bits_mod_0 [simp]:
   \<open>0 mod a = 0\<close>
   using div_mult_mod_eq [of 0 a] by simp
 
 lemma bits_one_mod_two_eq_one [simp]:
   \<open>1 mod 2 = 1\<close>
   by (simp add: mod2_eq_if)
 
 lemma bit_0 [simp]:
   \<open>bit a 0 \<longleftrightarrow> odd a\<close>
   by (simp add: bit_iff_odd)
 
 lemma bit_Suc:
   \<open>bit a (Suc n) \<longleftrightarrow> bit (a div 2) n\<close>
   using div_exp_eq [of a 1 n] by (simp add: bit_iff_odd)
 
 lemma bit_rec:
   \<open>bit a n \<longleftrightarrow> (if n = 0 then odd a else bit (a div 2) (n - 1))\<close>
   by (cases n) (simp_all add: bit_Suc)
 
 lemma bit_0_eq [simp]:
   \<open>bit 0 = bot\<close>
   by (simp add: fun_eq_iff bit_iff_odd)
 
 context
   fixes a
   assumes stable: \<open>a div 2 = a\<close>
 begin
 
 lemma bits_stable_imp_add_self:
   \<open>a + a mod 2 = 0\<close>
 proof -
   have \<open>a div 2 * 2 + a mod 2 = a\<close>
     by (fact div_mult_mod_eq)
   then have \<open>a * 2 + a mod 2 = a\<close>
     by (simp add: stable)
   then show ?thesis
     by (simp add: mult_2_right ac_simps)
 qed
 
 lemma stable_imp_bit_iff_odd:
   \<open>bit a n \<longleftrightarrow> odd a\<close>
   by (induction n) (simp_all add: stable bit_Suc)
 
 end
 
 lemma bit_iff_idd_imp_stable:
   \<open>a div 2 = a\<close> if \<open>\<And>n. bit a n \<longleftrightarrow> odd a\<close>
 using that proof (induction a rule: bits_induct)
   case (stable a)
   then show ?case
     by simp
 next
   case (rec a b)
   from rec.prems [of 1] have [simp]: \<open>b = odd a\<close>
     by (simp add: rec.hyps bit_Suc)
   from rec.hyps have hyp: \<open>(of_bool (odd a) + 2 * a) div 2 = a\<close>
     by simp
   have \<open>bit a n \<longleftrightarrow> odd a\<close> for n
     using rec.prems [of \<open>Suc n\<close>] by (simp add: hyp bit_Suc)
   then have \<open>a div 2 = a\<close>
     by (rule rec.IH)
   then have \<open>of_bool (odd a) + 2 * a = 2 * (a div 2) + of_bool (odd a)\<close>
     by (simp add: ac_simps)
   also have \<open>\<dots> = a\<close>
     using mult_div_mod_eq [of 2 a]
     by (simp add: of_bool_odd_eq_mod_2)
   finally show ?case
     using \<open>a div 2 = a\<close> by (simp add: hyp)
 qed
 
 lemma exp_eq_0_imp_not_bit:
   \<open>\<not> bit a n\<close> if \<open>2 ^ n = 0\<close>
   using that by (simp add: bit_iff_odd)
 
+definition
+  possible_bit :: "'a itself \<Rightarrow> nat \<Rightarrow> bool"
+  where
+  "possible_bit tyrep n = (2 ^ n \<noteq> (0 :: 'a))"
+
+lemma possible_bit_0[simp]:
+  "possible_bit ty 0"
+  by (simp add: possible_bit_def)
+
+lemma fold_possible_bit:
+  "2 ^ n = (0 :: 'a) \<longleftrightarrow> \<not> possible_bit TYPE('a) n"
+  by (simp add: possible_bit_def)
+
+lemmas impossible_bit = exp_eq_0_imp_not_bit[simplified fold_possible_bit]
+
+lemma bit_imp_possible_bit:
+  "bit a n \<Longrightarrow> possible_bit TYPE('a) n"
+  by (rule ccontr) (simp add: impossible_bit)
+
+lemma possible_bit_less_imp:
+  "possible_bit tyrep i \<Longrightarrow> j \<le> i \<Longrightarrow> possible_bit tyrep j"
+  using power_add[of "2 :: 'a" j "i - j"]
+  by (clarsimp simp: possible_bit_def eq_commute[where a=0])
+
+lemma possible_bit_min[simp]:
+  "possible_bit tyrep (min i j) \<longleftrightarrow> possible_bit tyrep i \<or> possible_bit tyrep j"
+  by (auto simp: min_def elim: possible_bit_less_imp)
+
 lemma bit_eqI:
-  \<open>a = b\<close> if \<open>\<And>n. 2 ^ n \<noteq> 0 \<Longrightarrow> bit a n \<longleftrightarrow> bit b n\<close>
+  \<open>a = b\<close> if \<open>\<And>n. possible_bit TYPE('a) n \<Longrightarrow> bit a n \<longleftrightarrow> bit b n\<close>
 proof -
   have \<open>bit a n \<longleftrightarrow> bit b n\<close> for n
   proof (cases \<open>2 ^ n = 0\<close>)
     case True
     then show ?thesis
       by (simp add: exp_eq_0_imp_not_bit)
   next
     case False
     then show ?thesis
-      by (rule that)
+      by (rule that[unfolded possible_bit_def])
   qed
   then show ?thesis proof (induction a arbitrary: b rule: bits_induct)
     case (stable a)
     from stable(2) [of 0] have **: \<open>even b \<longleftrightarrow> even a\<close>
       by simp
     have \<open>b div 2 = b\<close>
     proof (rule bit_iff_idd_imp_stable)
       fix n
       from stable have *: \<open>bit b n \<longleftrightarrow> bit a n\<close>
         by simp
       also have \<open>bit a n \<longleftrightarrow> odd a\<close>
         using stable by (simp add: stable_imp_bit_iff_odd)
       finally show \<open>bit b n \<longleftrightarrow> odd b\<close>
         by (simp add: **)
     qed
     from ** have \<open>a mod 2 = b mod 2\<close>
       by (simp add: mod2_eq_if)
     then have \<open>a mod 2 + (a + b) = b mod 2 + (a + b)\<close>
       by simp
     then have \<open>a + a mod 2 + b = b + b mod 2 + a\<close>
       by (simp add: ac_simps)
     with \<open>a div 2 = a\<close> \<open>b div 2 = b\<close> show ?case
       by (simp add: bits_stable_imp_add_self)
   next
     case (rec a p)
     from rec.prems [of 0] have [simp]: \<open>p = odd b\<close>
       by simp
     from rec.hyps have \<open>bit a n \<longleftrightarrow> bit (b div 2) n\<close> for n
       using rec.prems [of \<open>Suc n\<close>] by (simp add: bit_Suc)
     then have \<open>a = b div 2\<close>
       by (rule rec.IH)
     then have \<open>2 * a = 2 * (b div 2)\<close>
       by simp
     then have \<open>b mod 2 + 2 * a = b mod 2 + 2 * (b div 2)\<close>
       by simp
     also have \<open>\<dots> = b\<close>
       by (fact mod_mult_div_eq)
     finally show ?case
       by (auto simp add: mod2_eq_if)
   qed
 qed
 
 lemma bit_eq_iff:
-  \<open>a = b \<longleftrightarrow> (\<forall>n. bit a n \<longleftrightarrow> bit b n)\<close>
+  \<open>a = b \<longleftrightarrow> (\<forall>n. possible_bit TYPE('a) n \<longrightarrow> bit a n \<longleftrightarrow> bit b n)\<close>
   by (auto intro: bit_eqI)
 
 named_theorems bit_simps \<open>Simplification rules for \<^const>\<open>bit\<close>\<close>
 
 lemma bit_exp_iff [bit_simps]:
-  \<open>bit (2 ^ m) n \<longleftrightarrow> 2 ^ m \<noteq> 0 \<and> m = n\<close>
-  by (auto simp add: bit_iff_odd exp_div_exp_eq)
+  \<open>bit (2 ^ m) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> m = n\<close>
+  by (auto simp add: bit_iff_odd exp_div_exp_eq possible_bit_def)
 
 lemma bit_1_iff [bit_simps]:
-  \<open>bit 1 n \<longleftrightarrow> 1 \<noteq> 0 \<and> n = 0\<close>
-  using bit_exp_iff [of 0 n] by simp
+  \<open>bit 1 n \<longleftrightarrow> n = 0\<close>
+  using bit_exp_iff [of 0 n]
+  by auto
 
 lemma bit_2_iff [bit_simps]:
-  \<open>bit 2 n \<longleftrightarrow> 2 \<noteq> 0 \<and> n = 1\<close>
+  \<open>bit 2 n \<longleftrightarrow> possible_bit TYPE('a) 1 \<and> n = 1\<close>
   using bit_exp_iff [of 1 n] by auto
 
 lemma even_bit_succ_iff:
   \<open>bit (1 + a) n \<longleftrightarrow> bit a n \<or> n = 0\<close> if \<open>even a\<close>
   using that by (cases \<open>n = 0\<close>) (simp_all add: bit_iff_odd)
 
+lemma bit_double_iff [bit_simps]:
+  \<open>bit (2 * a) n \<longleftrightarrow> bit a (n - 1) \<and> n \<noteq> 0 \<and> possible_bit TYPE('a) n\<close>
+  using even_mult_exp_div_exp_iff [of a 1 n]
+  by (cases n, auto simp add: bit_iff_odd ac_simps possible_bit_def)
+
 lemma odd_bit_iff_bit_pred:
   \<open>bit a n \<longleftrightarrow> bit (a - 1) n \<or> n = 0\<close> if \<open>odd a\<close>
 proof -
   from \<open>odd a\<close> obtain b where \<open>a = 2 * b + 1\<close> ..
   moreover have \<open>bit (2 * b) n \<or> n = 0 \<longleftrightarrow> bit (1 + 2 * b) n\<close>
     using even_bit_succ_iff by simp
   ultimately show ?thesis by (simp add: ac_simps)
 qed
 
-lemma bit_double_iff [bit_simps]:
-  \<open>bit (2 * a) n \<longleftrightarrow> bit a (n - 1) \<and> n \<noteq> 0 \<and> 2 ^ n \<noteq> 0\<close>
-  using even_mult_exp_div_exp_iff [of a 1 n]
-  by (cases n, auto simp add: bit_iff_odd ac_simps)
-
 lemma bit_eq_rec:
   \<open>a = b \<longleftrightarrow> (even a \<longleftrightarrow> even b) \<and> a div 2 = b div 2\<close> (is \<open>?P = ?Q\<close>)
 proof
   assume ?P
   then show ?Q
     by simp
 next
   assume ?Q
   then have \<open>even a \<longleftrightarrow> even b\<close> and \<open>a div 2 = b div 2\<close>
     by simp_all
   show ?P
   proof (rule bit_eqI)
     fix n
     show \<open>bit a n \<longleftrightarrow> bit b n\<close>
     proof (cases n)
       case 0
       with \<open>even a \<longleftrightarrow> even b\<close> show ?thesis
         by simp
     next
       case (Suc n)
       moreover from \<open>a div 2 = b div 2\<close> have \<open>bit (a div 2) n = bit (b div 2) n\<close>
         by simp
       ultimately show ?thesis
         by (simp add: bit_Suc)
     qed
   qed
 qed
 
 lemma bit_mod_2_iff [simp]:
   \<open>bit (a mod 2) n \<longleftrightarrow> n = 0 \<and> odd a\<close>
   by (cases a rule: parity_cases) (simp_all add: bit_iff_odd)
 
-lemma bit_mask_iff:
-  \<open>bit (2 ^ m - 1) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> n < m\<close>
-  by (simp add: bit_iff_odd even_mask_div_iff not_le)
+lemma bit_mask_sub_iff:
+  \<open>bit (2 ^ m - 1) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> n < m\<close>
+  by (simp add: bit_iff_odd even_mask_div_iff not_le possible_bit_def)
 
 lemma bit_Numeral1_iff [simp]:
   \<open>bit (numeral Num.One) n \<longleftrightarrow> n = 0\<close>
   by (simp add: bit_rec)
 
 lemma exp_add_not_zero_imp:
   \<open>2 ^ m \<noteq> 0\<close> and \<open>2 ^ n \<noteq> 0\<close> if \<open>2 ^ (m + n) \<noteq> 0\<close>
 proof -
   have \<open>\<not> (2 ^ m = 0 \<or> 2 ^ n = 0)\<close>
   proof (rule notI)
     assume \<open>2 ^ m = 0 \<or> 2 ^ n = 0\<close>
     then have \<open>2 ^ (m + n) = 0\<close>
       by (rule disjE) (simp_all add: power_add)
     with that show False ..
   qed
   then show \<open>2 ^ m \<noteq> 0\<close> and \<open>2 ^ n \<noteq> 0\<close>
     by simp_all
 qed
 
 lemma bit_disjunctive_add_iff:
   \<open>bit (a + b) n \<longleftrightarrow> bit a n \<or> bit b n\<close>
   if \<open>\<And>n. \<not> bit a n \<or> \<not> bit b n\<close>
 proof (cases \<open>2 ^ n = 0\<close>)
   case True
   then show ?thesis
     by (simp add: exp_eq_0_imp_not_bit)
 next
   case False
   with that show ?thesis proof (induction n arbitrary: a b)
     case 0
     from "0.prems"(1) [of 0] show ?case
       by auto
   next
     case (Suc n)
     from Suc.prems(1) [of 0] have even: \<open>even a \<or> even b\<close>
       by auto
     have bit: \<open>\<not> bit (a div 2) n \<or> \<not> bit (b div 2) n\<close> for n
       using Suc.prems(1) [of \<open>Suc n\<close>] by (simp add: bit_Suc)
     from Suc.prems(2) have \<open>2 * 2 ^ n \<noteq> 0\<close> \<open>2 ^ n \<noteq> 0\<close>
       by (auto simp add: mult_2)
     have \<open>a + b = (a div 2 * 2 + a mod 2) + (b div 2 * 2 + b mod 2)\<close>
       using div_mult_mod_eq [of a 2] div_mult_mod_eq [of b 2] by simp
     also have \<open>\<dots> = of_bool (odd a \<or> odd b) + 2 * (a div 2 + b div 2)\<close>
       using even by (auto simp add: algebra_simps mod2_eq_if)
     finally have \<open>bit ((a + b) div 2) n \<longleftrightarrow> bit (a div 2 + b div 2) n\<close>
-      using \<open>2 * 2 ^ n \<noteq> 0\<close> by simp (simp_all flip: bit_Suc add: bit_double_iff)
+      using \<open>2 * 2 ^ n \<noteq> 0\<close> by simp (simp_all flip: bit_Suc add: bit_double_iff possible_bit_def)
     also have \<open>\<dots> \<longleftrightarrow> bit (a div 2) n \<or> bit (b div 2) n\<close>
       using bit \<open>2 ^ n \<noteq> 0\<close> by (rule Suc.IH)
     finally show ?case
       by (simp add: bit_Suc)
   qed
 qed
 
 lemma
   exp_add_not_zero_imp_left: \<open>2 ^ m \<noteq> 0\<close>
   and exp_add_not_zero_imp_right: \<open>2 ^ n \<noteq> 0\<close>
   if \<open>2 ^ (m + n) \<noteq> 0\<close>
 proof -
   have \<open>\<not> (2 ^ m = 0 \<or> 2 ^ n = 0)\<close>
   proof (rule notI)
     assume \<open>2 ^ m = 0 \<or> 2 ^ n = 0\<close>
     then have \<open>2 ^ (m + n) = 0\<close>
       by (rule disjE) (simp_all add: power_add)
     with that show False ..
   qed
   then show \<open>2 ^ m \<noteq> 0\<close> and \<open>2 ^ n \<noteq> 0\<close>
     by simp_all
 qed
 
 lemma exp_not_zero_imp_exp_diff_not_zero:
   \<open>2 ^ (n - m) \<noteq> 0\<close> if \<open>2 ^ n \<noteq> 0\<close>
 proof (cases \<open>m \<le> n\<close>)
   case True
   moreover define q where \<open>q = n - m\<close>
   ultimately have \<open>n = m + q\<close>
     by simp
   with that show ?thesis
     by (simp add: exp_add_not_zero_imp_right)
 next
   case False
   with that show ?thesis
     by simp
 qed
 
 end
 
 lemma nat_bit_induct [case_names zero even odd]:
   "P n" if zero: "P 0"
     and even: "\<And>n. P n \<Longrightarrow> n > 0 \<Longrightarrow> P (2 * n)"
     and odd: "\<And>n. P n \<Longrightarrow> P (Suc (2 * n))"
 proof (induction n rule: less_induct)
   case (less n)
   show "P n"
   proof (cases "n = 0")
     case True with zero show ?thesis by simp
   next
     case False
     with less have hyp: "P (n div 2)" by simp
     show ?thesis
     proof (cases "even n")
       case True
       then have "n \<noteq> 1"
         by auto
       with \<open>n \<noteq> 0\<close> have "n div 2 > 0"
         by simp
       with \<open>even n\<close> hyp even [of "n div 2"] show ?thesis
         by simp
     next
       case False
       with hyp odd [of "n div 2"] show ?thesis
         by simp
     qed
   qed
 qed
 
 instantiation nat :: semiring_bits
 begin
 
 definition bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> bool\<close>
   where \<open>bit_nat m n \<longleftrightarrow> odd (m div 2 ^ n)\<close>
 
 instance
 proof
   show \<open>P n\<close> if stable: \<open>\<And>n. n div 2 = n \<Longrightarrow> P n\<close>
     and rec: \<open>\<And>n b. P n \<Longrightarrow> (of_bool b + 2 * n) div 2 = n \<Longrightarrow> P (of_bool b + 2 * n)\<close>
     for P and n :: nat
   proof (induction n rule: nat_bit_induct)
     case zero
     from stable [of 0] show ?case
       by simp
   next
     case (even n)
     with rec [of n False] show ?case
       by simp
   next
     case (odd n)
     with rec [of n True] show ?case
       by simp
   qed
   show \<open>q mod 2 ^ m mod 2 ^ n = q mod 2 ^ min m n\<close>
     for q m n :: nat
     apply (auto simp add: less_iff_Suc_add power_add mod_mod_cancel split: split_min_lin)
     apply (metis div_mult2_eq mod_div_trivial mod_eq_self_iff_div_eq_0 mod_mult_self2_is_0 power_commutes)
     done
   show \<open>(q * 2 ^ m) mod (2 ^ n) = (q mod 2 ^ (n - m)) * 2 ^ m\<close> if \<open>m \<le> n\<close>
     for q m n :: nat
     using that
     apply (auto simp add: mod_mod_cancel div_mult2_eq power_add mod_mult2_eq le_iff_add split: split_min_lin)
     done
   show \<open>even ((2 ^ m - (1::nat)) div 2 ^ n) \<longleftrightarrow> 2 ^ n = (0::nat) \<or> m \<le> n\<close>
     for m n :: nat
     using even_mask_div_iff' [where ?'a = nat, of m n] by simp
   show \<open>even (q * 2 ^ m div 2 ^ n) \<longleftrightarrow> n < m \<or> (2::nat) ^ n = 0 \<or> m \<le> n \<and> even (q div 2 ^ (n - m))\<close>
     for m n q r :: nat
     apply (auto simp add: not_less power_add ac_simps dest!: le_Suc_ex)
     apply (metis (full_types) dvd_mult dvd_mult_imp_div dvd_power_iff_le not_less not_less_eq order_refl power_Suc)
     done
 qed (auto simp add: div_mult2_eq mod_mult2_eq power_add power_diff bit_nat_def)
 
 end
 
+lemma possible_bit_nat[simp]:
+  "possible_bit TYPE(nat) n"
+  by (simp add: possible_bit_def)
+
 lemma int_bit_induct [case_names zero minus even odd]:
   "P k" if zero_int: "P 0"
     and minus_int: "P (- 1)"
     and even_int: "\<And>k. P k \<Longrightarrow> k \<noteq> 0 \<Longrightarrow> P (k * 2)"
     and odd_int: "\<And>k. P k \<Longrightarrow> k \<noteq> - 1 \<Longrightarrow> P (1 + (k * 2))" for k :: int
 proof (cases "k \<ge> 0")
   case True
   define n where "n = nat k"
   with True have "k = int n"
     by simp
   then show "P k"
   proof (induction n arbitrary: k rule: nat_bit_induct)
     case zero
     then show ?case
       by (simp add: zero_int)
   next
     case (even n)
     have "P (int n * 2)"
       by (rule even_int) (use even in simp_all)
     with even show ?case
       by (simp add: ac_simps)
   next
     case (odd n)
     have "P (1 + (int n * 2))"
       by (rule odd_int) (use odd in simp_all)
     with odd show ?case
       by (simp add: ac_simps)
   qed
 next
   case False
   define n where "n = nat (- k - 1)"
   with False have "k = - int n - 1"
     by simp
   then show "P k"
   proof (induction n arbitrary: k rule: nat_bit_induct)
     case zero
     then show ?case
       by (simp add: minus_int)
   next
     case (even n)
     have "P (1 + (- int (Suc n) * 2))"
       by (rule odd_int) (use even in \<open>simp_all add: algebra_simps\<close>)
     also have "\<dots> = - int (2 * n) - 1"
       by (simp add: algebra_simps)
     finally show ?case
       using even.prems by simp
   next
     case (odd n)
     have "P (- int (Suc n) * 2)"
       by (rule even_int) (use odd in \<open>simp_all add: algebra_simps\<close>)
     also have "\<dots> = - int (Suc (2 * n)) - 1"
       by (simp add: algebra_simps)
     finally show ?case
       using odd.prems by simp
   qed
 qed
 
 context semiring_bits
 begin
 
 lemma bit_of_bool_iff [bit_simps]:
   \<open>bit (of_bool b) n \<longleftrightarrow> b \<and> n = 0\<close>
   by (simp add: bit_1_iff)
 
 lemma even_of_nat_iff:
   \<open>even (of_nat n) \<longleftrightarrow> even n\<close>
   by (induction n rule: nat_bit_induct) simp_all
 
 lemma bit_of_nat_iff [bit_simps]:
-  \<open>bit (of_nat m) n \<longleftrightarrow> (2::'a) ^ n \<noteq> 0 \<and> bit m n\<close>
+  \<open>bit (of_nat m) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> bit m n\<close>
 proof (cases \<open>(2::'a) ^ n = 0\<close>)
   case True
   then show ?thesis
-    by (simp add: exp_eq_0_imp_not_bit)
+    by (simp add: exp_eq_0_imp_not_bit possible_bit_def)
 next
   case False
   then have \<open>bit (of_nat m) n \<longleftrightarrow> bit m n\<close>
   proof (induction m arbitrary: n rule: nat_bit_induct)
     case zero
     then show ?case
       by simp
   next
     case (even m)
     then show ?case
       by (cases n)
-        (auto simp add: bit_double_iff Bit_Operations.bit_double_iff dest: mult_not_zero)
+        (auto simp add: bit_double_iff Bit_Operations.bit_double_iff possible_bit_def dest: mult_not_zero)
   next
     case (odd m)
     then show ?case
       by (cases n)
-         (auto simp add: bit_double_iff even_bit_succ_iff Bit_Operations.bit_Suc dest: mult_not_zero)
+         (auto simp add: bit_double_iff even_bit_succ_iff possible_bit_def Bit_Operations.bit_Suc dest: mult_not_zero)
   qed
   with False show ?thesis
-    by simp
+    by (simp add: possible_bit_def)
 qed
 
 end
 
 instantiation int :: semiring_bits
 begin
 
 definition bit_int :: \<open>int \<Rightarrow> nat \<Rightarrow> bool\<close>
   where \<open>bit_int k n \<longleftrightarrow> odd (k div 2 ^ n)\<close>
 
 instance
 proof
   show \<open>P k\<close> if stable: \<open>\<And>k. k div 2 = k \<Longrightarrow> P k\<close>
     and rec: \<open>\<And>k b. P k \<Longrightarrow> (of_bool b + 2 * k) div 2 = k \<Longrightarrow> P (of_bool b + 2 * k)\<close>
     for P and k :: int
   proof (induction k rule: int_bit_induct)
     case zero
     from stable [of 0] show ?case
       by simp
   next
     case minus
     from stable [of \<open>- 1\<close>] show ?case
       by simp
   next
     case (even k)
     with rec [of k False] show ?case
       by (simp add: ac_simps)
   next
     case (odd k)
     with rec [of k True] show ?case
       by (simp add: ac_simps)
   qed
   show \<open>(2::int) ^ m div 2 ^ n = of_bool ((2::int) ^ m \<noteq> 0 \<and> n \<le> m) * 2 ^ (m - n)\<close>
     for m n :: nat
   proof (cases \<open>m < n\<close>)
     case True
     then have \<open>n = m + (n - m)\<close>
       by simp
     then have \<open>(2::int) ^ m div 2 ^ n = (2::int) ^ m div 2 ^ (m + (n - m))\<close>
       by simp
     also have \<open>\<dots> = (2::int) ^ m div (2 ^ m * 2 ^ (n - m))\<close>
       by (simp add: power_add)
     also have \<open>\<dots> = (2::int) ^ m div 2 ^ m div 2 ^ (n - m)\<close>
       by (simp add: zdiv_zmult2_eq)
     finally show ?thesis using \<open>m < n\<close> by simp
   next
     case False
     then show ?thesis
       by (simp add: power_diff)
   qed
   show \<open>k mod 2 ^ m mod 2 ^ n = k mod 2 ^ min m n\<close>
     for m n :: nat and k :: int
     using mod_exp_eq [of \<open>nat k\<close> m n]
     apply (auto simp add: mod_mod_cancel zdiv_zmult2_eq power_add zmod_zmult2_eq le_iff_add split: split_min_lin)
      apply (auto simp add: less_iff_Suc_add mod_mod_cancel power_add)
     apply (simp only: flip: mult.left_commute [of \<open>2 ^ m\<close>])
     apply (subst zmod_zmult2_eq) apply simp_all
     done
   show \<open>(k * 2 ^ m) mod (2 ^ n) = (k mod 2 ^ (n - m)) * 2 ^ m\<close>
     if \<open>m \<le> n\<close> for m n :: nat and k :: int
     using that
     apply (auto simp add: power_add zmod_zmult2_eq le_iff_add split: split_min_lin)
     done
   show \<open>even ((2 ^ m - (1::int)) div 2 ^ n) \<longleftrightarrow> 2 ^ n = (0::int) \<or> m \<le> n\<close>
     for m n :: nat
     using even_mask_div_iff' [where ?'a = int, of m n] by simp
   show \<open>even (k * 2 ^ m div 2 ^ n) \<longleftrightarrow> n < m \<or> (2::int) ^ n = 0 \<or> m \<le> n \<and> even (k div 2 ^ (n - m))\<close>
     for m n :: nat and k l :: int
     apply (auto simp add: not_less power_add ac_simps dest!: le_Suc_ex)
     apply (metis Suc_leI dvd_mult dvd_mult_imp_div dvd_power_le dvd_refl power.simps(2))
     done
 qed (auto simp add: zdiv_zmult2_eq zmod_zmult2_eq power_add power_diff not_le bit_int_def)
 
 end
 
+lemma possible_bit_int[simp]:
+  "possible_bit TYPE(int) n"
+  by (simp add: possible_bit_def)
+
 lemma bit_not_int_iff':
   \<open>bit (- k - 1) n \<longleftrightarrow> \<not> bit k n\<close>
   for k :: int
 proof (induction n arbitrary: k)
   case 0
   show ?case
     by simp
 next
   case (Suc n)
   have \<open>- k - 1 = - (k + 2) + 1\<close>
     by simp
   also have \<open>(- (k + 2) + 1) div 2 = - (k div 2) - 1\<close>
   proof (cases \<open>even k\<close>)
     case True
     then have \<open>- k div 2 = - (k div 2)\<close>
       by rule (simp flip: mult_minus_right)
     with True show ?thesis
       by simp
   next
     case False
     have \<open>4 = 2 * (2::int)\<close>
       by simp
     also have \<open>2 * 2 div 2 = (2::int)\<close>
       by (simp only: nonzero_mult_div_cancel_left)
     finally have *: \<open>4 div 2 = (2::int)\<close> .
     from False obtain l where k: \<open>k = 2 * l + 1\<close> ..
     then have \<open>- k - 2 = 2 * - (l + 2) + 1\<close>
       by simp
     then have \<open>(- k - 2) div 2 + 1 = - (k div 2) - 1\<close>
       by (simp flip: mult_minus_right add: *) (simp add: k)
     with False show ?thesis
       by simp
   qed
   finally have \<open>(- k - 1) div 2 = - (k div 2) - 1\<close> .
   with Suc show ?case
     by (simp add: bit_Suc)
 qed
 
 lemma bit_nat_iff [bit_simps]:
   \<open>bit (nat k) n \<longleftrightarrow> k \<ge> 0 \<and> bit k n\<close>
 proof (cases \<open>k \<ge> 0\<close>)
   case True
   moreover define m where \<open>m = nat k\<close>
   ultimately have \<open>k = int m\<close>
     by simp
   then show ?thesis
     by (simp add: bit_simps)
 next
   case False
   then show ?thesis
     by simp
 qed
 
 
 subsection \<open>Bit operations\<close>
 
 class semiring_bit_operations = semiring_bits +
   fixes "and" :: \<open>'a \<Rightarrow> 'a \<Rightarrow> 'a\<close>  (infixr \<open>AND\<close> 64)
     and or :: \<open>'a \<Rightarrow> 'a \<Rightarrow> 'a\<close>  (infixr \<open>OR\<close> 59)
     and xor :: \<open>'a \<Rightarrow> 'a \<Rightarrow> 'a\<close>  (infixr \<open>XOR\<close> 59)
     and mask :: \<open>nat \<Rightarrow> 'a\<close>
     and set_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
     and unset_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
     and flip_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
     and push_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
     and drop_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
     and take_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
   assumes bit_and_iff [bit_simps]: \<open>bit (a AND b) n \<longleftrightarrow> bit a n \<and> bit b n\<close>
     and bit_or_iff [bit_simps]: \<open>bit (a OR b) n \<longleftrightarrow> bit a n \<or> bit b n\<close>
     and bit_xor_iff [bit_simps]: \<open>bit (a XOR b) n \<longleftrightarrow> bit a n \<noteq> bit b n\<close>
     and mask_eq_exp_minus_1: \<open>mask n = 2 ^ n - 1\<close>
     and set_bit_eq_or: \<open>set_bit n a = a OR push_bit n 1\<close>
     and bit_unset_bit_iff [bit_simps]: \<open>bit (unset_bit m a) n \<longleftrightarrow> bit a n \<and> m \<noteq> n\<close>
     and flip_bit_eq_xor: \<open>flip_bit n a = a XOR push_bit n 1\<close>
     and push_bit_eq_mult: \<open>push_bit n a = a * 2 ^ n\<close>
     and drop_bit_eq_div: \<open>drop_bit n a = a div 2 ^ n\<close>
     and take_bit_eq_mod: \<open>take_bit n a = a mod 2 ^ n\<close>
 begin
 
 text \<open>
   We want the bitwise operations to bind slightly weaker
   than \<open>+\<close> and \<open>-\<close>.
 
   Logically, \<^const>\<open>push_bit\<close>,
   \<^const>\<open>drop_bit\<close> and \<^const>\<open>take_bit\<close> are just aliases; having them
   as separate operations makes proofs easier, otherwise proof automation
   would fiddle with concrete expressions \<^term>\<open>2 ^ n\<close> in a way obfuscating the basic
   algebraic relationships between those operations.
 
   For the sake of code generation operations 
   are specified as definitional class operations,
   taking into account that specific instances of these can be implemented
   differently wrt. code generation.
 \<close>
 
 sublocale "and": semilattice \<open>(AND)\<close>
   by standard (auto simp add: bit_eq_iff bit_and_iff)
 
 sublocale or: semilattice_neutr \<open>(OR)\<close> 0
   by standard (auto simp add: bit_eq_iff bit_or_iff)
 
 sublocale xor: comm_monoid \<open>(XOR)\<close> 0
   by standard (auto simp add: bit_eq_iff bit_xor_iff)
 
 lemma even_and_iff:
   \<open>even (a AND b) \<longleftrightarrow> even a \<or> even b\<close>
   using bit_and_iff [of a b 0] by auto
 
 lemma even_or_iff:
   \<open>even (a OR b) \<longleftrightarrow> even a \<and> even b\<close>
   using bit_or_iff [of a b 0] by auto
 
 lemma even_xor_iff:
   \<open>even (a XOR b) \<longleftrightarrow> (even a \<longleftrightarrow> even b)\<close>
   using bit_xor_iff [of a b 0] by auto
 
 lemma zero_and_eq [simp]:
   \<open>0 AND a = 0\<close>
   by (simp add: bit_eq_iff bit_and_iff)
 
 lemma and_zero_eq [simp]:
   \<open>a AND 0 = 0\<close>
   by (simp add: bit_eq_iff bit_and_iff)
 
 lemma one_and_eq:
   \<open>1 AND a = a mod 2\<close>
   by (simp add: bit_eq_iff bit_and_iff) (auto simp add: bit_1_iff)
 
 lemma and_one_eq:
   \<open>a AND 1 = a mod 2\<close>
   using one_and_eq [of a] by (simp add: ac_simps)
 
 lemma one_or_eq:
   \<open>1 OR a = a + of_bool (even a)\<close>
   by (simp add: bit_eq_iff bit_or_iff add.commute [of _ 1] even_bit_succ_iff) (auto simp add: bit_1_iff)
 
 lemma or_one_eq:
   \<open>a OR 1 = a + of_bool (even a)\<close>
   using one_or_eq [of a] by (simp add: ac_simps)
 
 lemma one_xor_eq:
   \<open>1 XOR a = a + of_bool (even a) - of_bool (odd a)\<close>
   by (simp add: bit_eq_iff bit_xor_iff add.commute [of _ 1] even_bit_succ_iff) (auto simp add: bit_1_iff odd_bit_iff_bit_pred elim: oddE)
 
 lemma xor_one_eq:
   \<open>a XOR 1 = a + of_bool (even a) - of_bool (odd a)\<close>
   using one_xor_eq [of a] by (simp add: ac_simps)
 
 lemma xor_self_eq [simp]:
   \<open>a XOR a = 0\<close>
   by (rule bit_eqI) (simp add: bit_simps)
 
 lemma bit_iff_odd_drop_bit:
   \<open>bit a n \<longleftrightarrow> odd (drop_bit n a)\<close>
   by (simp add: bit_iff_odd drop_bit_eq_div)
 
 lemma even_drop_bit_iff_not_bit:
   \<open>even (drop_bit n a) \<longleftrightarrow> \<not> bit a n\<close>
   by (simp add: bit_iff_odd_drop_bit)
 
 lemma div_push_bit_of_1_eq_drop_bit:
   \<open>a div push_bit n 1 = drop_bit n a\<close>
   by (simp add: push_bit_eq_mult drop_bit_eq_div)
 
 lemma bits_ident:
   "push_bit n (drop_bit n a) + take_bit n a = a"
   using div_mult_mod_eq by (simp add: push_bit_eq_mult take_bit_eq_mod drop_bit_eq_div)
 
 lemma push_bit_push_bit [simp]:
   "push_bit m (push_bit n a) = push_bit (m + n) a"
   by (simp add: push_bit_eq_mult power_add ac_simps)
 
 lemma push_bit_0_id [simp]:
   "push_bit 0 = id"
   by (simp add: fun_eq_iff push_bit_eq_mult)
 
 lemma push_bit_of_0 [simp]:
   "push_bit n 0 = 0"
   by (simp add: push_bit_eq_mult)
 
 lemma push_bit_of_1:
   "push_bit n 1 = 2 ^ n"
   by (simp add: push_bit_eq_mult)
 
 lemma push_bit_Suc [simp]:
   "push_bit (Suc n) a = push_bit n (a * 2)"
   by (simp add: push_bit_eq_mult ac_simps)
 
 lemma push_bit_double:
   "push_bit n (a * 2) = push_bit n a * 2"
   by (simp add: push_bit_eq_mult ac_simps)
 
 lemma push_bit_add:
   "push_bit n (a + b) = push_bit n a + push_bit n b"
   by (simp add: push_bit_eq_mult algebra_simps)
 
 lemma push_bit_numeral [simp]:
   \<open>push_bit (numeral l) (numeral k) = push_bit (pred_numeral l) (numeral (Num.Bit0 k))\<close>
   by (simp add: numeral_eq_Suc mult_2_right) (simp add: numeral_Bit0)
 
 lemma take_bit_0 [simp]:
   "take_bit 0 a = 0"
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_Suc:
   \<open>take_bit (Suc n) a = take_bit n (a div 2) * 2 + a mod 2\<close>
 proof -
   have \<open>take_bit (Suc n) (a div 2 * 2 + of_bool (odd a)) = take_bit n (a div 2) * 2 + of_bool (odd a)\<close>
     using even_succ_mod_exp [of \<open>2 * (a div 2)\<close> \<open>Suc n\<close>]
       mult_exp_mod_exp_eq [of 1 \<open>Suc n\<close> \<open>a div 2\<close>]
     by (auto simp add: take_bit_eq_mod ac_simps)
   then show ?thesis
     using div_mult_mod_eq [of a 2] by (simp add: mod_2_eq_odd)
 qed
 
 lemma take_bit_rec:
   \<open>take_bit n a = (if n = 0 then 0 else take_bit (n - 1) (a div 2) * 2 + a mod 2)\<close>
   by (cases n) (simp_all add: take_bit_Suc)
 
 lemma take_bit_Suc_0 [simp]:
   \<open>take_bit (Suc 0) a = a mod 2\<close>
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_of_0 [simp]:
   "take_bit n 0 = 0"
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_of_1 [simp]:
   "take_bit n 1 = of_bool (n > 0)"
   by (cases n) (simp_all add: take_bit_Suc)
 
 lemma drop_bit_of_0 [simp]:
   "drop_bit n 0 = 0"
   by (simp add: drop_bit_eq_div)
 
 lemma drop_bit_of_1 [simp]:
   "drop_bit n 1 = of_bool (n = 0)"
   by (simp add: drop_bit_eq_div)
 
 lemma drop_bit_0 [simp]:
   "drop_bit 0 = id"
   by (simp add: fun_eq_iff drop_bit_eq_div)
 
 lemma drop_bit_Suc:
   "drop_bit (Suc n) a = drop_bit n (a div 2)"
   using div_exp_eq [of a 1] by (simp add: drop_bit_eq_div)
 
 lemma drop_bit_rec:
   "drop_bit n a = (if n = 0 then a else drop_bit (n - 1) (a div 2))"
   by (cases n) (simp_all add: drop_bit_Suc)
 
 lemma drop_bit_half:
   "drop_bit n (a div 2) = drop_bit n a div 2"
   by (induction n arbitrary: a) (simp_all add: drop_bit_Suc)
 
 lemma drop_bit_of_bool [simp]:
   "drop_bit n (of_bool b) = of_bool (n = 0 \<and> b)"
   by (cases n) simp_all
 
 lemma even_take_bit_eq [simp]:
   \<open>even (take_bit n a) \<longleftrightarrow> n = 0 \<or> even a\<close>
   by (simp add: take_bit_rec [of n a])
 
 lemma take_bit_take_bit [simp]:
   "take_bit m (take_bit n a) = take_bit (min m n) a"
   by (simp add: take_bit_eq_mod mod_exp_eq ac_simps)
 
 lemma drop_bit_drop_bit [simp]:
   "drop_bit m (drop_bit n a) = drop_bit (m + n) a"
   by (simp add: drop_bit_eq_div power_add div_exp_eq ac_simps)
 
 lemma push_bit_take_bit:
   "push_bit m (take_bit n a) = take_bit (m + n) (push_bit m a)"
   apply (simp add: push_bit_eq_mult take_bit_eq_mod power_add ac_simps)
   using mult_exp_mod_exp_eq [of m \<open>m + n\<close> a] apply (simp add: ac_simps power_add)
   done
 
 lemma take_bit_push_bit:
   "take_bit m (push_bit n a) = push_bit n (take_bit (m - n) a)"
 proof (cases "m \<le> n")
   case True
   then show ?thesis
     apply (simp add:)
     apply (simp_all add: push_bit_eq_mult take_bit_eq_mod)
     apply (auto dest!: le_Suc_ex simp add: power_add ac_simps)
     using mult_exp_mod_exp_eq [of m m \<open>a * 2 ^ n\<close> for n]
     apply (simp add: ac_simps)
     done
 next
   case False
   then show ?thesis
     using push_bit_take_bit [of n "m - n" a]
     by simp
 qed
 
 lemma take_bit_drop_bit:
   "take_bit m (drop_bit n a) = drop_bit n (take_bit (m + n) a)"
   by (simp add: drop_bit_eq_div take_bit_eq_mod ac_simps div_exp_mod_exp_eq)
 
 lemma drop_bit_take_bit:
   "drop_bit m (take_bit n a) = take_bit (n - m) (drop_bit m a)"
 proof (cases "m \<le> n")
   case True
   then show ?thesis
     using take_bit_drop_bit [of "n - m" m a] by simp
 next
   case False
   then obtain q where \<open>m = n + q\<close>
     by (auto simp add: not_le dest: less_imp_Suc_add)
   then have \<open>drop_bit m (take_bit n a) = 0\<close>
     using div_exp_eq [of \<open>a mod 2 ^ n\<close> n q]
     by (simp add: take_bit_eq_mod drop_bit_eq_div)
   with False show ?thesis
     by simp
 qed
 
 lemma even_push_bit_iff [simp]:
   \<open>even (push_bit n a) \<longleftrightarrow> n \<noteq> 0 \<or> even a\<close>
   by (simp add: push_bit_eq_mult) auto
 
 lemma bit_push_bit_iff [bit_simps]:
-  \<open>bit (push_bit m a) n \<longleftrightarrow> m \<le> n \<and> 2 ^ n \<noteq> 0 \<and> bit a (n - m)\<close>
-  by (auto simp add: bit_iff_odd push_bit_eq_mult even_mult_exp_div_exp_iff)
+  \<open>bit (push_bit m a) n \<longleftrightarrow> m \<le> n \<and> possible_bit TYPE('a) n \<and> bit a (n - m)\<close>
+  by (auto simp add: bit_iff_odd push_bit_eq_mult even_mult_exp_div_exp_iff possible_bit_def)
 
 lemma bit_drop_bit_eq [bit_simps]:
   \<open>bit (drop_bit n a) = bit a \<circ> (+) n\<close>
   by (simp add: bit_iff_odd fun_eq_iff ac_simps flip: drop_bit_eq_div)
 
 lemma bit_take_bit_iff [bit_simps]:
   \<open>bit (take_bit m a) n \<longleftrightarrow> n < m \<and> bit a n\<close>
   by (simp add: bit_iff_odd drop_bit_take_bit not_le flip: drop_bit_eq_div)
 
 lemma stable_imp_drop_bit_eq:
   \<open>drop_bit n a = a\<close>
   if \<open>a div 2 = a\<close>
   by (induction n) (simp_all add: that drop_bit_Suc)
 
 lemma stable_imp_take_bit_eq:
   \<open>take_bit n a = (if even a then 0 else 2 ^ n - 1)\<close>
     if \<open>a div 2 = a\<close>
-proof (rule bit_eqI)
+proof (rule bit_eqI[unfolded possible_bit_def])
   fix m
   assume \<open>2 ^ m \<noteq> 0\<close>
   with that show \<open>bit (take_bit n a) m \<longleftrightarrow> bit (if even a then 0 else 2 ^ n - 1) m\<close>
-    by (simp add: bit_take_bit_iff bit_mask_iff stable_imp_bit_iff_odd)
+    by (simp add: bit_take_bit_iff bit_mask_sub_iff possible_bit_def stable_imp_bit_iff_odd)
 qed
 
 lemma exp_dvdE:
   assumes \<open>2 ^ n dvd a\<close>
   obtains b where \<open>a = push_bit n b\<close>
 proof -
   from assms obtain b where \<open>a = 2 ^ n * b\<close> ..
   then have \<open>a = push_bit n b\<close>
     by (simp add: push_bit_eq_mult ac_simps)
   with that show thesis .
 qed
 
 lemma take_bit_eq_0_iff:
   \<open>take_bit n a = 0 \<longleftrightarrow> 2 ^ n dvd a\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof
   assume ?P
   then show ?Q
     by (simp add: take_bit_eq_mod mod_0_imp_dvd)
 next
   assume ?Q
   then obtain b where \<open>a = push_bit n b\<close>
     by (rule exp_dvdE)
   then show ?P
     by (simp add: take_bit_push_bit)
 qed
 
 lemma take_bit_tightened:
   \<open>take_bit m a = take_bit m b\<close> if \<open>take_bit n a = take_bit n b\<close> and \<open>m \<le> n\<close> 
 proof -
   from that have \<open>take_bit m (take_bit n a) = take_bit m (take_bit n b)\<close>
     by simp
   then have \<open>take_bit (min m n) a = take_bit (min m n) b\<close>
     by simp
   with that show ?thesis
     by (simp add: min_def)
 qed
 
 lemma take_bit_eq_self_iff_drop_bit_eq_0:
   \<open>take_bit n a = a \<longleftrightarrow> drop_bit n a = 0\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof
   assume ?P
   show ?Q
   proof (rule bit_eqI)
     fix m
     from \<open>?P\<close> have \<open>a = take_bit n a\<close> ..
     also have \<open>\<not> bit (take_bit n a) (n + m)\<close>
       unfolding bit_simps
       by (simp add: bit_simps) 
     finally show \<open>bit (drop_bit n a) m \<longleftrightarrow> bit 0 m\<close>
       by (simp add: bit_simps)
   qed
 next
   assume ?Q
   show ?P
   proof (rule bit_eqI)
     fix m
     from \<open>?Q\<close> have \<open>\<not> bit (drop_bit n a) (m - n)\<close>
       by simp
     then have \<open> \<not> bit a (n + (m - n))\<close>
       by (simp add: bit_simps)
     then show \<open>bit (take_bit n a) m \<longleftrightarrow> bit a m\<close>
       by (cases \<open>m < n\<close>) (auto simp add: bit_simps)
   qed
 qed
 
 lemma drop_bit_exp_eq:
-  \<open>drop_bit m (2 ^ n) = of_bool (m \<le> n \<and> 2 ^ n \<noteq> 0) * 2 ^ (n - m)\<close>
-  by (rule bit_eqI) (auto simp add: bit_simps)
+  \<open>drop_bit m (2 ^ n) = of_bool (m \<le> n \<and> possible_bit TYPE('a) n) * 2 ^ (n - m)\<close>
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma take_bit_and [simp]:
   \<open>take_bit n (a AND b) = take_bit n a AND take_bit n b\<close>
-  by (auto simp add: bit_eq_iff bit_take_bit_iff bit_and_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma take_bit_or [simp]:
   \<open>take_bit n (a OR b) = take_bit n a OR take_bit n b\<close>
-  by (auto simp add: bit_eq_iff bit_take_bit_iff bit_or_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma take_bit_xor [simp]:
   \<open>take_bit n (a XOR b) = take_bit n a XOR take_bit n b\<close>
-  by (auto simp add: bit_eq_iff bit_take_bit_iff bit_xor_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma push_bit_and [simp]:
   \<open>push_bit n (a AND b) = push_bit n a AND push_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_push_bit_iff bit_and_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma push_bit_or [simp]:
   \<open>push_bit n (a OR b) = push_bit n a OR push_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_push_bit_iff bit_or_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma push_bit_xor [simp]:
   \<open>push_bit n (a XOR b) = push_bit n a XOR push_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_push_bit_iff bit_xor_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma drop_bit_and [simp]:
   \<open>drop_bit n (a AND b) = drop_bit n a AND drop_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_drop_bit_eq bit_and_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma drop_bit_or [simp]:
   \<open>drop_bit n (a OR b) = drop_bit n a OR drop_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_drop_bit_eq bit_or_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma drop_bit_xor [simp]:
   \<open>drop_bit n (a XOR b) = drop_bit n a XOR drop_bit n b\<close>
-  by (rule bit_eqI) (auto simp add: bit_drop_bit_eq bit_xor_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma bit_mask_iff [bit_simps]:
-  \<open>bit (mask m) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> n < m\<close>
-  by (simp add: mask_eq_exp_minus_1 bit_mask_iff)
+  \<open>bit (mask m) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> n < m\<close>
+  by (simp add: mask_eq_exp_minus_1 bit_mask_sub_iff)
 
 lemma even_mask_iff:
   \<open>even (mask n) \<longleftrightarrow> n = 0\<close>
   using bit_mask_iff [of n 0] by auto
 
 lemma mask_0 [simp]:
   \<open>mask 0 = 0\<close>
   by (simp add: mask_eq_exp_minus_1)
 
 lemma mask_Suc_0 [simp]:
   \<open>mask (Suc 0) = 1\<close>
   by (simp add: mask_eq_exp_minus_1 add_implies_diff sym)
 
 lemma mask_Suc_exp:
   \<open>mask (Suc n) = 2 ^ n OR mask n\<close>
-  by (rule bit_eqI)
-    (auto simp add: bit_or_iff bit_mask_iff bit_exp_iff not_less le_less_Suc_eq)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma mask_Suc_double:
   \<open>mask (Suc n) = 1 OR 2 * mask n\<close>
-proof (rule bit_eqI)
-  fix q
-  assume \<open>2 ^ q \<noteq> 0\<close>
-  show \<open>bit (mask (Suc n)) q \<longleftrightarrow> bit (1 OR 2 * mask n) q\<close>
-    by (cases q)
-      (simp_all add: even_mask_iff even_or_iff bit_or_iff bit_mask_iff bit_exp_iff bit_double_iff not_less le_less_Suc_eq bit_1_iff, auto simp add: mult_2)
-qed
+  by (auto simp add: bit_eq_iff bit_simps elim: possible_bit_less_imp)
 
 lemma mask_numeral:
   \<open>mask (numeral n) = 1 + 2 * mask (pred_numeral n)\<close>
   by (simp add: numeral_eq_Suc mask_Suc_double one_or_eq ac_simps)
 
 lemma take_bit_mask [simp]:
   \<open>take_bit m (mask n) = mask (min m n)\<close>
   by (rule bit_eqI) (simp add: bit_simps)
 
 lemma take_bit_eq_mask:
   \<open>take_bit n a = a AND mask n\<close>
-  by (rule bit_eqI)
-    (auto simp add: bit_take_bit_iff bit_and_iff bit_mask_iff)
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemma or_eq_0_iff:
   \<open>a OR b = 0 \<longleftrightarrow> a = 0 \<and> b = 0\<close>
   by (auto simp add: bit_eq_iff bit_or_iff)
 
 lemma disjunctive_add:
   \<open>a + b = a OR b\<close> if \<open>\<And>n. \<not> bit a n \<or> \<not> bit b n\<close>
   by (rule bit_eqI) (use that in \<open>simp add: bit_disjunctive_add_iff bit_or_iff\<close>)
 
 lemma bit_iff_and_drop_bit_eq_1:
   \<open>bit a n \<longleftrightarrow> drop_bit n a AND 1 = 1\<close>
   by (simp add: bit_iff_odd_drop_bit and_one_eq odd_iff_mod_2_eq_one)
 
 lemma bit_iff_and_push_bit_not_eq_0:
   \<open>bit a n \<longleftrightarrow> a AND push_bit n 1 \<noteq> 0\<close>
   apply (cases \<open>2 ^ n = 0\<close>)
   apply (simp_all add: push_bit_of_1 bit_eq_iff bit_and_iff bit_push_bit_iff exp_eq_0_imp_not_bit)
   apply (simp_all add: bit_exp_iff)
   done
 
 lemmas set_bit_def = set_bit_eq_or
 
 lemma bit_set_bit_iff [bit_simps]:
-  \<open>bit (set_bit m a) n \<longleftrightarrow> bit a n \<or> (m = n \<and> 2 ^ n \<noteq> 0)\<close>
+  \<open>bit (set_bit m a) n \<longleftrightarrow> bit a n \<or> (m = n \<and> possible_bit TYPE('a) n)\<close>
   by (auto simp add: set_bit_def push_bit_of_1 bit_or_iff bit_exp_iff)
 
 lemma even_set_bit_iff:
   \<open>even (set_bit m a) \<longleftrightarrow> even a \<and> m \<noteq> 0\<close>
   using bit_set_bit_iff [of m a 0] by auto
 
 lemma even_unset_bit_iff:
   \<open>even (unset_bit m a) \<longleftrightarrow> even a \<or> m = 0\<close>
   using bit_unset_bit_iff [of m a 0] by auto
 
 lemma and_exp_eq_0_iff_not_bit:
   \<open>a AND 2 ^ n = 0 \<longleftrightarrow> \<not> bit a n\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
-proof
-  assume ?Q
-  then show ?P
-    by (auto intro: bit_eqI simp add: bit_simps)
-next
-  assume ?P
-  show ?Q
-  proof (rule notI)
-    assume \<open>bit a n\<close>
-    then have \<open>a AND 2 ^ n = 2 ^ n\<close>
-      by (auto intro: bit_eqI simp add: bit_simps)
-    with \<open>?P\<close> show False
-      using \<open>bit a n\<close> exp_eq_0_imp_not_bit by auto
-  qed
-qed
+  using bit_imp_possible_bit[of a n]
+  by (auto simp add: bit_eq_iff bit_simps)
 
 lemmas flip_bit_def = flip_bit_eq_xor
 
 lemma bit_flip_bit_iff [bit_simps]:
-  \<open>bit (flip_bit m a) n \<longleftrightarrow> (m = n \<longleftrightarrow> \<not> bit a n) \<and> 2 ^ n \<noteq> 0\<close>
-  by (auto simp add: flip_bit_def push_bit_of_1 bit_xor_iff bit_exp_iff exp_eq_0_imp_not_bit)
+  \<open>bit (flip_bit m a) n \<longleftrightarrow> (m = n \<longleftrightarrow> \<not> bit a n) \<and> possible_bit TYPE('a) n\<close>
+  by (auto simp add: bit_eq_iff bit_simps flip_bit_eq_xor bit_imp_possible_bit)
 
 lemma even_flip_bit_iff:
   \<open>even (flip_bit m a) \<longleftrightarrow> \<not> (even a \<longleftrightarrow> m = 0)\<close>
-  using bit_flip_bit_iff [of m a 0] by auto
+  using bit_flip_bit_iff [of m a 0] by (auto simp: possible_bit_def)
 
 lemma set_bit_0 [simp]:
   \<open>set_bit 0 a = 1 + 2 * (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  then show \<open>bit (set_bit 0 a) m = bit (1 + 2 * (a div 2)) m\<close>
-    by (simp add: bit_set_bit_iff bit_double_iff even_bit_succ_iff)
-      (cases m, simp_all add: bit_Suc)
+  by (auto simp add: bit_eq_iff bit_simps even_bit_succ_iff simp flip: bit_Suc)
+
+lemma bit_sum_mult_2_cases:
+  assumes a: "\<forall>j. \<not> bit a (Suc j)"
+  shows "bit (a + 2 * b) n = (if n = 0 then odd a else bit (2 * b) n)"
+proof -
+  have a_eq: "bit a i \<longleftrightarrow> i = 0 \<and> odd a" for i
+    by (cases i, simp_all add: a)
+  show ?thesis
+    by (simp add: disjunctive_add[simplified disj_imp] a_eq bit_simps)
 qed
 
 lemma set_bit_Suc:
   \<open>set_bit (Suc n) a = a mod 2 + 2 * set_bit n (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  show \<open>bit (set_bit (Suc n) a) m \<longleftrightarrow> bit (a mod 2 + 2 * set_bit n (a div 2)) m\<close>
-  proof (cases m)
-    case 0
-    then show ?thesis
-      by (simp add: even_set_bit_iff)
-  next
-    case (Suc m)
-    with * have \<open>2 ^ m \<noteq> 0\<close>
-      using mult_2 by auto
-    show ?thesis
-      by (cases a rule: parity_cases)
-        (simp_all add: bit_set_bit_iff bit_double_iff even_bit_succ_iff *,
-        simp_all add: Suc \<open>2 ^ m \<noteq> 0\<close> bit_Suc)
-  qed
-qed
+  by (auto simp add: bit_eq_iff bit_sum_mult_2_cases bit_simps bit_Suc[symmetric]
+    elim: possible_bit_less_imp)
 
 lemma unset_bit_0 [simp]:
   \<open>unset_bit 0 a = 2 * (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  then show \<open>bit (unset_bit 0 a) m = bit (2 * (a div 2)) m\<close>
-    by (simp add: bit_unset_bit_iff bit_double_iff)
-      (cases m, simp_all add: bit_Suc)
-qed
+  by (auto simp add: bit_eq_iff bit_simps even_bit_succ_iff simp flip: bit_Suc)
 
 lemma unset_bit_Suc:
   \<open>unset_bit (Suc n) a = a mod 2 + 2 * unset_bit n (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  then show \<open>bit (unset_bit (Suc n) a) m \<longleftrightarrow> bit (a mod 2 + 2 * unset_bit n (a div 2)) m\<close>
-  proof (cases m)
-    case 0
-    then show ?thesis
-      by (simp add: even_unset_bit_iff)
-  next
-    case (Suc m)
-    show ?thesis
-      by (cases a rule: parity_cases)
-        (simp_all add: bit_unset_bit_iff bit_double_iff even_bit_succ_iff *,
-         simp_all add: Suc bit_Suc)
-  qed
-qed
+  by (auto simp add: bit_eq_iff bit_sum_mult_2_cases bit_simps bit_Suc[symmetric]
+    elim: possible_bit_less_imp)
 
 lemma flip_bit_0 [simp]:
   \<open>flip_bit 0 a = of_bool (even a) + 2 * (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  then show \<open>bit (flip_bit 0 a) m = bit (of_bool (even a) + 2 * (a div 2)) m\<close>
-    by (simp add: bit_flip_bit_iff bit_double_iff even_bit_succ_iff)
-      (cases m, simp_all add: bit_Suc)
-qed
+  by (auto simp add: bit_eq_iff bit_simps even_bit_succ_iff simp flip: bit_Suc)
 
 lemma flip_bit_Suc:
   \<open>flip_bit (Suc n) a = a mod 2 + 2 * flip_bit n (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  show \<open>bit (flip_bit (Suc n) a) m \<longleftrightarrow> bit (a mod 2 + 2 * flip_bit n (a div 2)) m\<close>
-  proof (cases m)
-    case 0
-    then show ?thesis
-      by (simp add: even_flip_bit_iff)
-  next
-    case (Suc m)
-    with * have \<open>2 ^ m \<noteq> 0\<close>
-      using mult_2 by auto
-    show ?thesis
-      by (cases a rule: parity_cases)
-        (simp_all add: bit_flip_bit_iff bit_double_iff even_bit_succ_iff,
-        simp_all add: Suc \<open>2 ^ m \<noteq> 0\<close> bit_Suc)
-  qed
-qed
+  by (auto simp add: bit_eq_iff bit_sum_mult_2_cases bit_simps bit_Suc[symmetric]
+    elim: possible_bit_less_imp)
 
 lemma flip_bit_eq_if:
   \<open>flip_bit n a = (if bit a n then unset_bit else set_bit) n a\<close>
   by (rule bit_eqI) (auto simp add: bit_set_bit_iff bit_unset_bit_iff bit_flip_bit_iff)
 
 lemma take_bit_set_bit_eq:
   \<open>take_bit n (set_bit m a) = (if n \<le> m then take_bit n a else set_bit m (take_bit n a))\<close>
   by (rule bit_eqI) (auto simp add: bit_take_bit_iff bit_set_bit_iff)
 
 lemma take_bit_unset_bit_eq:
   \<open>take_bit n (unset_bit m a) = (if n \<le> m then take_bit n a else unset_bit m (take_bit n a))\<close>
   by (rule bit_eqI) (auto simp add: bit_take_bit_iff bit_unset_bit_iff)
 
 lemma take_bit_flip_bit_eq:
   \<open>take_bit n (flip_bit m a) = (if n \<le> m then take_bit n a else flip_bit m (take_bit n a))\<close>
   by (rule bit_eqI) (auto simp add: bit_take_bit_iff bit_flip_bit_iff)
 
 end
 
 class ring_bit_operations = semiring_bit_operations + ring_parity +
   fixes not :: \<open>'a \<Rightarrow> 'a\<close>  (\<open>NOT\<close>)
-  assumes bit_not_iff [bit_simps]: \<open>\<And>n. bit (NOT a) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> \<not> bit a n\<close>
+  assumes bit_not_iff_eq: \<open>\<And>n. bit (NOT a) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> \<not> bit a n\<close>
   assumes minus_eq_not_minus_1: \<open>- a = NOT (a - 1)\<close>
 begin
 
+lemmas bit_not_iff[bit_simps] = bit_not_iff_eq[unfolded fold_possible_bit]
+
 text \<open>
   For the sake of code generation \<^const>\<open>not\<close> is specified as
   definitional class operation.  Note that \<^const>\<open>not\<close> has no
   sensible definition for unlimited but only positive bit strings
   (type \<^typ>\<open>nat\<close>).
 \<close>
 
 lemma bits_minus_1_mod_2_eq [simp]:
   \<open>(- 1) mod 2 = 1\<close>
   by (simp add: mod_2_eq_odd)
 
 lemma not_eq_complement:
   \<open>NOT a = - a - 1\<close>
   using minus_eq_not_minus_1 [of \<open>a + 1\<close>] by simp
 
 lemma minus_eq_not_plus_1:
   \<open>- a = NOT a + 1\<close>
   using not_eq_complement [of a] by simp
 
 lemma bit_minus_iff [bit_simps]:
-  \<open>bit (- a) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> \<not> bit (a - 1) n\<close>
+  \<open>bit (- a) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> \<not> bit (a - 1) n\<close>
   by (simp add: minus_eq_not_minus_1 bit_not_iff)
 
 lemma even_not_iff [simp]:
-  \<open>even (NOT a) \<longleftrightarrow> odd a\<close>
+  \<open>even (NOT a) \<longleftrightarrow> odd a\<close> 
   using bit_not_iff [of a 0] by auto
 
 lemma bit_not_exp_iff [bit_simps]:
-  \<open>bit (NOT (2 ^ m)) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> n \<noteq> m\<close>
+  \<open>bit (NOT (2 ^ m)) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> n \<noteq> m\<close>
   by (auto simp add: bit_not_iff bit_exp_iff)
 
 lemma bit_minus_1_iff [simp]:
-  \<open>bit (- 1) n \<longleftrightarrow> 2 ^ n \<noteq> 0\<close>
+  \<open>bit (- 1) n \<longleftrightarrow> possible_bit TYPE('a) n\<close>
   by (simp add: bit_minus_iff)
 
 lemma bit_minus_exp_iff [bit_simps]:
-  \<open>bit (- (2 ^ m)) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> n \<ge> m\<close>
+  \<open>bit (- (2 ^ m)) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> n \<ge> m\<close>
   by (auto simp add: bit_simps simp flip: mask_eq_exp_minus_1)
 
 lemma bit_minus_2_iff [simp]:
-  \<open>bit (- 2) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> n > 0\<close>
+  \<open>bit (- 2) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> n > 0\<close>
   by (simp add: bit_minus_iff bit_1_iff)
 
 lemma not_one_eq:
   \<open>NOT 1 = - 2\<close>
   by (simp add: bit_eq_iff bit_not_iff) (simp add: bit_1_iff)
 
 sublocale "and": semilattice_neutr \<open>(AND)\<close> \<open>- 1\<close>
   by standard (rule bit_eqI, simp add: bit_and_iff)
 
 sublocale bit: abstract_boolean_algebra \<open>(AND)\<close> \<open>(OR)\<close> NOT 0 \<open>- 1\<close>
   by standard (auto simp add: bit_and_iff bit_or_iff bit_not_iff intro: bit_eqI)
 
 sublocale bit: abstract_boolean_algebra_sym_diff \<open>(AND)\<close> \<open>(OR)\<close> NOT 0 \<open>- 1\<close> \<open>(XOR)\<close>
   apply standard
   apply (rule bit_eqI)
   apply (auto simp add: bit_simps)
   done
 
 lemma and_eq_not_not_or:
   \<open>a AND b = NOT (NOT a OR NOT b)\<close>
   by simp
 
 lemma or_eq_not_not_and:
   \<open>a OR b = NOT (NOT a AND NOT b)\<close>
   by simp
 
 lemma not_add_distrib:
   \<open>NOT (a + b) = NOT a - b\<close>
   by (simp add: not_eq_complement algebra_simps)
 
 lemma not_diff_distrib:
   \<open>NOT (a - b) = NOT a + b\<close>
   using not_add_distrib [of a \<open>- b\<close>] by simp
 
 lemma and_eq_minus_1_iff:
   \<open>a AND b = - 1 \<longleftrightarrow> a = - 1 \<and> b = - 1\<close>
-proof
-  assume \<open>a = - 1 \<and> b = - 1\<close>
-  then show \<open>a AND b = - 1\<close>
-    by simp
-next
-  assume \<open>a AND b = - 1\<close>
-  have *: \<open>bit a n\<close> \<open>bit b n\<close> if \<open>2 ^ n \<noteq> 0\<close> for n
-  proof -
-    from \<open>a AND b = - 1\<close>
-    have \<open>bit (a AND b) n = bit (- 1) n\<close>
-      by (simp add: bit_eq_iff)
-    then show \<open>bit a n\<close> \<open>bit b n\<close>
-      using that by (simp_all add: bit_and_iff)
-  qed
-  have \<open>a = - 1\<close>
-    by (rule bit_eqI) (simp add: *)
-  moreover have \<open>b = - 1\<close>
-    by (rule bit_eqI) (simp add: *)
-  ultimately show \<open>a = - 1 \<and> b = - 1\<close>
-    by simp
-qed
+  by (auto simp: bit_eq_iff bit_simps)
 
 lemma disjunctive_diff:
   \<open>a - b = a AND NOT b\<close> if \<open>\<And>n. bit b n \<Longrightarrow> bit a n\<close>
 proof -
   have \<open>NOT a + b = NOT a OR b\<close>
     by (rule disjunctive_add) (auto simp add: bit_not_iff dest: that)
   then have \<open>NOT (NOT a + b) = NOT (NOT a OR b)\<close>
     by simp
   then show ?thesis
     by (simp add: not_add_distrib)
 qed
 
 lemma push_bit_minus:
   \<open>push_bit n (- a) = - push_bit n a\<close>
   by (simp add: push_bit_eq_mult)
 
 lemma take_bit_not_take_bit:
   \<open>take_bit n (NOT (take_bit n a)) = take_bit n (NOT a)\<close>
   by (auto simp add: bit_eq_iff bit_take_bit_iff bit_not_iff)
 
 lemma take_bit_not_iff:
   \<open>take_bit n (NOT a) = take_bit n (NOT b) \<longleftrightarrow> take_bit n a = take_bit n b\<close>
   apply (simp add: bit_eq_iff)
   apply (simp add: bit_not_iff bit_take_bit_iff bit_exp_iff)
   apply (use exp_eq_0_imp_not_bit in blast)
   done
 
 lemma take_bit_not_eq_mask_diff:
   \<open>take_bit n (NOT a) = mask n - take_bit n a\<close>
 proof -
   have \<open>take_bit n (NOT a) = take_bit n (NOT (take_bit n a))\<close>
     by (simp add: take_bit_not_take_bit)
   also have \<open>\<dots> = mask n AND NOT (take_bit n a)\<close>
     by (simp add: take_bit_eq_mask ac_simps)
   also have \<open>\<dots> = mask n - take_bit n a\<close>
     by (subst disjunctive_diff)
-      (auto simp add: bit_take_bit_iff bit_mask_iff exp_eq_0_imp_not_bit)
+      (auto simp add: bit_take_bit_iff bit_mask_iff bit_imp_possible_bit)
   finally show ?thesis
     by simp
 qed
 
 lemma mask_eq_take_bit_minus_one:
   \<open>mask n = take_bit n (- 1)\<close>
   by (simp add: bit_eq_iff bit_mask_iff bit_take_bit_iff conj_commute)
 
 lemma take_bit_minus_one_eq_mask:
   \<open>take_bit n (- 1) = mask n\<close>
   by (simp add: mask_eq_take_bit_minus_one)
 
 lemma minus_exp_eq_not_mask:
   \<open>- (2 ^ n) = NOT (mask n)\<close>
   by (rule bit_eqI) (simp add: bit_minus_iff bit_not_iff flip: mask_eq_exp_minus_1)
 
 lemma push_bit_minus_one_eq_not_mask:
   \<open>push_bit n (- 1) = NOT (mask n)\<close>
   by (simp add: push_bit_eq_mult minus_exp_eq_not_mask)
 
 lemma take_bit_not_mask_eq_0:
   \<open>take_bit m (NOT (mask n)) = 0\<close> if \<open>n \<ge> m\<close>
   by (rule bit_eqI) (use that in \<open>simp add: bit_take_bit_iff bit_not_iff bit_mask_iff\<close>)
 
 lemma unset_bit_eq_and_not:
   \<open>unset_bit n a = a AND NOT (push_bit n 1)\<close>
   by (rule bit_eqI) (auto simp add: bit_simps)
 
 lemmas unset_bit_def = unset_bit_eq_and_not
 
 end
 
 
 subsection \<open>Instance \<^typ>\<open>int\<close>\<close>
 
 instantiation int :: ring_bit_operations
 begin
 
 definition not_int :: \<open>int \<Rightarrow> int\<close>
   where \<open>not_int k = - k - 1\<close>
 
 lemma not_int_rec:
   \<open>NOT k = of_bool (even k) + 2 * NOT (k div 2)\<close> for k :: int
   by (auto simp add: not_int_def elim: oddE)
 
 lemma even_not_iff_int:
   \<open>even (NOT k) \<longleftrightarrow> odd k\<close> for k :: int
   by (simp add: not_int_def)
 
 lemma not_int_div_2:
   \<open>NOT k div 2 = NOT (k div 2)\<close> for k :: int
   by (cases k) (simp_all add: not_int_def divide_int_def nat_add_distrib)
 
 lemma bit_not_int_iff:
   \<open>bit (NOT k) n \<longleftrightarrow> \<not> bit k n\<close>
   for k :: int
   by (simp add: bit_not_int_iff' not_int_def)
 
 function and_int :: \<open>int \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>(k::int) AND l = (if k \<in> {0, - 1} \<and> l \<in> {0, - 1}
     then - of_bool (odd k \<and> odd l)
     else of_bool (odd k \<and> odd l) + 2 * ((k div 2) AND (l div 2)))\<close>
   by auto
 
 termination proof (relation \<open>measure (\<lambda>(k, l). nat (\<bar>k\<bar> + \<bar>l\<bar>))\<close>)
   show \<open>wf (measure (\<lambda>(k, l). nat (\<bar>k\<bar> + \<bar>l\<bar>)))\<close>
     by simp
   show \<open>((k div 2, l div 2), k, l) \<in> measure (\<lambda>(k, l). nat (\<bar>k\<bar> + \<bar>l\<bar>))\<close>
     if \<open>\<not> (k \<in> {0, - 1} \<and> l \<in> {0, - 1})\<close> for k l
   proof -
     have less_eq: \<open>\<bar>k div 2\<bar> \<le> \<bar>k\<bar>\<close> for k :: int
       by (cases k) (simp_all add: divide_int_def nat_add_distrib)
     have less: \<open>\<bar>k div 2\<bar> < \<bar>k\<bar>\<close> if \<open>k \<notin> {0, - 1}\<close> for k :: int
     proof (cases k)
       case (nonneg n)
       with that show ?thesis
         by (simp add: int_div_less_self)
     next
       case (neg n)
       with that have \<open>n \<noteq> 0\<close>
         by simp
       then have \<open>n div 2 < n\<close>
         by (simp add: div_less_iff_less_mult)
       with neg that show ?thesis
         by (simp add: divide_int_def nat_add_distrib)
     qed
     from that have *: \<open>k \<notin> {0, - 1} \<or> l \<notin> {0, - 1}\<close>
       by simp
     then have \<open>0 < \<bar>k\<bar> + \<bar>l\<bar>\<close>
       by auto
     moreover from * have \<open>\<bar>k div 2\<bar> + \<bar>l div 2\<bar> < \<bar>k\<bar> + \<bar>l\<bar>\<close>
     proof
       assume \<open>k \<notin> {0, - 1}\<close>
       then have \<open>\<bar>k div 2\<bar> < \<bar>k\<bar>\<close>
         by (rule less)
       with less_eq [of l] show ?thesis
         by auto
     next
       assume \<open>l \<notin> {0, - 1}\<close>
       then have \<open>\<bar>l div 2\<bar> < \<bar>l\<bar>\<close>
         by (rule less)
       with less_eq [of k] show ?thesis
         by auto
     qed
     ultimately show ?thesis
       by simp
   qed
 qed
 
 declare and_int.simps [simp del]
 
 lemma and_int_rec:
   \<open>k AND l = of_bool (odd k \<and> odd l) + 2 * ((k div 2) AND (l div 2))\<close>
     for k l :: int
 proof (cases \<open>k \<in> {0, - 1} \<and> l \<in> {0, - 1}\<close>)
   case True
   then show ?thesis
     by auto (simp_all add: and_int.simps)
 next
   case False
   then show ?thesis
     by (auto simp add: ac_simps and_int.simps [of k l])
 qed
 
 lemma bit_and_int_iff:
   \<open>bit (k AND l) n \<longleftrightarrow> bit k n \<and> bit l n\<close> for k l :: int
 proof (induction n arbitrary: k l)
   case 0
   then show ?case
     by (simp add: and_int_rec [of k l])
 next
   case (Suc n)
   then show ?case
     by (simp add: and_int_rec [of k l] bit_Suc)
 qed
 
 lemma even_and_iff_int:
   \<open>even (k AND l) \<longleftrightarrow> even k \<or> even l\<close> for k l :: int
   using bit_and_int_iff [of k l 0] by auto
 
 definition or_int :: \<open>int \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>k OR l = NOT (NOT k AND NOT l)\<close> for k l :: int
 
 lemma or_int_rec:
   \<open>k OR l = of_bool (odd k \<or> odd l) + 2 * ((k div 2) OR (l div 2))\<close>
   for k l :: int
   using and_int_rec [of \<open>NOT k\<close> \<open>NOT l\<close>]
   by (simp add: or_int_def even_not_iff_int not_int_div_2)
     (simp_all add: not_int_def)
 
 lemma bit_or_int_iff:
   \<open>bit (k OR l) n \<longleftrightarrow> bit k n \<or> bit l n\<close> for k l :: int
   by (simp add: or_int_def bit_not_int_iff bit_and_int_iff)
 
 definition xor_int :: \<open>int \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>k XOR l = k AND NOT l OR NOT k AND l\<close> for k l :: int
 
 lemma xor_int_rec:
   \<open>k XOR l = of_bool (odd k \<noteq> odd l) + 2 * ((k div 2) XOR (l div 2))\<close>
   for k l :: int
   by (simp add: xor_int_def or_int_rec [of \<open>k AND NOT l\<close> \<open>NOT k AND l\<close>] even_and_iff_int even_not_iff_int)
     (simp add: and_int_rec [of \<open>NOT k\<close> \<open>l\<close>] and_int_rec [of \<open>k\<close> \<open>NOT l\<close>] not_int_div_2)
 
 lemma bit_xor_int_iff:
   \<open>bit (k XOR l) n \<longleftrightarrow> bit k n \<noteq> bit l n\<close> for k l :: int
   by (auto simp add: xor_int_def bit_or_int_iff bit_and_int_iff bit_not_int_iff)
 
 definition mask_int :: \<open>nat \<Rightarrow> int\<close>
   where \<open>mask n = (2 :: int) ^ n - 1\<close>
 
 definition push_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>push_bit_int n k = k * 2 ^ n\<close>
 
 definition drop_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>drop_bit_int n k = k div 2 ^ n\<close>
 
 definition take_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>take_bit_int n k = k mod 2 ^ n\<close>
 
 definition set_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>set_bit n k = k OR push_bit n 1\<close> for k :: int
 
 definition unset_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>unset_bit n k = k AND NOT (push_bit n 1)\<close> for k :: int
 
 definition flip_bit_int :: \<open>nat \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>flip_bit n k = k XOR push_bit n 1\<close> for k :: int
 
 instance proof
   fix k l :: int and m n :: nat
   show \<open>- k = NOT (k - 1)\<close>
     by (simp add: not_int_def)
   show \<open>bit (k AND l) n \<longleftrightarrow> bit k n \<and> bit l n\<close>
     by (fact bit_and_int_iff)
   show \<open>bit (k OR l) n \<longleftrightarrow> bit k n \<or> bit l n\<close>
     by (fact bit_or_int_iff)
   show \<open>bit (k XOR l) n \<longleftrightarrow> bit k n \<noteq> bit l n\<close>
     by (fact bit_xor_int_iff)
   show \<open>bit (unset_bit m k) n \<longleftrightarrow> bit k n \<and> m \<noteq> n\<close>
   proof -
     have \<open>unset_bit m k = k AND NOT (push_bit m 1)\<close>
       by (simp add: unset_bit_int_def)
     also have \<open>NOT (push_bit m 1 :: int) = - (push_bit m 1 + 1)\<close>
       by (simp add: not_int_def)
     finally show ?thesis by (simp only: bit_simps bit_and_int_iff)
       (auto simp add: bit_simps bit_not_int_iff' push_bit_int_def)
   qed
 qed (simp_all add: bit_not_int_iff mask_int_def set_bit_int_def flip_bit_int_def
   push_bit_int_def drop_bit_int_def take_bit_int_def)
 
 end
 
 lemma bit_push_bit_iff_int:
   \<open>bit (push_bit m k) n \<longleftrightarrow> m \<le> n \<and> bit k (n - m)\<close> for k :: int
   by (auto simp add: bit_push_bit_iff)
 
 lemma take_bit_nonnegative [simp]:
   \<open>take_bit n k \<ge> 0\<close> for k :: int
   by (simp add: take_bit_eq_mod)
 
 lemma not_take_bit_negative [simp]:
   \<open>\<not> take_bit n k < 0\<close> for k :: int
   by (simp add: not_less)
 
 lemma take_bit_int_less_exp [simp]:
   \<open>take_bit n k < 2 ^ n\<close> for k :: int
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_int_eq_self_iff:
   \<open>take_bit n k = k \<longleftrightarrow> 0 \<le> k \<and> k < 2 ^ n\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for k :: int
 proof
   assume ?P
   moreover note take_bit_int_less_exp [of n k] take_bit_nonnegative [of n k]
   ultimately show ?Q
     by simp
 next
   assume ?Q
   then show ?P
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma take_bit_int_eq_self:
   \<open>take_bit n k = k\<close> if \<open>0 \<le> k\<close> \<open>k < 2 ^ n\<close> for k :: int
   using that by (simp add: take_bit_int_eq_self_iff)
 
 lemma mask_half_int:
   \<open>mask n div 2 = (mask (n - 1) :: int)\<close>
   by (cases n) (simp_all add: mask_eq_exp_minus_1 algebra_simps)
 
 lemma mask_nonnegative_int [simp]:
   \<open>mask n \<ge> (0::int)\<close>
   by (simp add: mask_eq_exp_minus_1)
 
 lemma not_mask_negative_int [simp]:
   \<open>\<not> mask n < (0::int)\<close>
   by (simp add: not_less)
 
 lemma not_nonnegative_int_iff [simp]:
   \<open>NOT k \<ge> 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (simp add: not_int_def)
 
 lemma not_negative_int_iff [simp]:
   \<open>NOT k < 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less not_le)
 
 lemma and_nonnegative_int_iff [simp]:
   \<open>k AND l \<ge> 0 \<longleftrightarrow> k \<ge> 0 \<or> l \<ge> 0\<close> for k l :: int
 proof (induction k arbitrary: l rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even k)
   then show ?case
     using and_int_rec [of \<open>k * 2\<close> l]
     by (simp add: pos_imp_zdiv_nonneg_iff zero_le_mult_iff)
 next
   case (odd k)
   from odd have \<open>0 \<le> k AND l div 2 \<longleftrightarrow> 0 \<le> k \<or> 0 \<le> l div 2\<close>
     by simp
   then have \<open>0 \<le> (1 + k * 2) div 2 AND l div 2 \<longleftrightarrow> 0 \<le> (1 + k * 2) div 2 \<or> 0 \<le> l div 2\<close>
     by simp
   with and_int_rec [of \<open>1 + k * 2\<close> l]
   show ?case
     by (auto simp add: zero_le_mult_iff not_le)
 qed
 
 lemma and_negative_int_iff [simp]:
   \<open>k AND l < 0 \<longleftrightarrow> k < 0 \<and> l < 0\<close> for k l :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less)
 
 lemma and_less_eq:
   \<open>k AND l \<le> k\<close> if \<open>l < 0\<close> for k l :: int
 using that proof (induction k arbitrary: l rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even k)
   from even.IH [of \<open>l div 2\<close>] even.hyps even.prems
   show ?case
     by (simp add: and_int_rec [of _ l])
 next
   case (odd k)
   from odd.IH [of \<open>l div 2\<close>] odd.hyps odd.prems
   show ?case
     by (simp add: and_int_rec [of _ l]) linarith
 qed
 
 lemma or_nonnegative_int_iff [simp]:
   \<open>k OR l \<ge> 0 \<longleftrightarrow> k \<ge> 0 \<and> l \<ge> 0\<close> for k l :: int
   by (simp only: or_eq_not_not_and not_nonnegative_int_iff) simp
 
 lemma or_negative_int_iff [simp]:
   \<open>k OR l < 0 \<longleftrightarrow> k < 0 \<or> l < 0\<close> for k l :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less)
 
 lemma or_greater_eq:
   \<open>k OR l \<ge> k\<close> if \<open>l \<ge> 0\<close> for k l :: int
 using that proof (induction k arbitrary: l rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even k)
   from even.IH [of \<open>l div 2\<close>] even.hyps even.prems
   show ?case
     by (simp add: or_int_rec [of _ l]) linarith
 next
   case (odd k)
   from odd.IH [of \<open>l div 2\<close>] odd.hyps odd.prems
   show ?case
     by (simp add: or_int_rec [of _ l])
 qed
 
 lemma xor_nonnegative_int_iff [simp]:
   \<open>k XOR l \<ge> 0 \<longleftrightarrow> (k \<ge> 0 \<longleftrightarrow> l \<ge> 0)\<close> for k l :: int
   by (simp only: bit.xor_def or_nonnegative_int_iff) auto
 
 lemma xor_negative_int_iff [simp]:
   \<open>k XOR l < 0 \<longleftrightarrow> (k < 0) \<noteq> (l < 0)\<close> for k l :: int
   by (subst Not_eq_iff [symmetric]) (auto simp add: not_less)
 
 lemma OR_upper: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close> \<open>x < 2 ^ n\<close> \<open>y < 2 ^ n\<close>
   shows \<open>x OR y < 2 ^ n\<close>
 using assms proof (induction x arbitrary: y n rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even x)
   from even.IH [of \<open>n - 1\<close> \<open>y div 2\<close>] even.prems even.hyps
   show ?case 
     by (cases n) (auto simp add: or_int_rec [of \<open>_ * 2\<close>] elim: oddE)
 next
   case (odd x)
   from odd.IH [of \<open>n - 1\<close> \<open>y div 2\<close>] odd.prems odd.hyps
   show ?case
     by (cases n) (auto simp add: or_int_rec [of \<open>1 + _ * 2\<close>], linarith)
 qed
 
 lemma XOR_upper: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close> \<open>x < 2 ^ n\<close> \<open>y < 2 ^ n\<close>
   shows \<open>x XOR y < 2 ^ n\<close>
 using assms proof (induction x arbitrary: y n rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even x)
   from even.IH [of \<open>n - 1\<close> \<open>y div 2\<close>] even.prems even.hyps
   show ?case 
     by (cases n) (auto simp add: xor_int_rec [of \<open>_ * 2\<close>] elim: oddE)
 next
   case (odd x)
   from odd.IH [of \<open>n - 1\<close> \<open>y div 2\<close>] odd.prems odd.hyps
   show ?case
     by (cases n) (auto simp add: xor_int_rec [of \<open>1 + _ * 2\<close>])
 qed
 
 lemma AND_lower [simp]: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close>
   shows \<open>0 \<le> x AND y\<close>
   using assms by simp
 
 lemma OR_lower [simp]: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close> \<open>0 \<le> y\<close>
   shows \<open>0 \<le> x OR y\<close>
   using assms by simp
 
 lemma XOR_lower [simp]: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close> \<open>0 \<le> y\<close>
   shows \<open>0 \<le> x XOR y\<close>
   using assms by simp
 
 lemma AND_upper1 [simp]: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> x\<close>
   shows \<open>x AND y \<le> x\<close>
 using assms proof (induction x arbitrary: y rule: int_bit_induct)
   case (odd k)
   then have \<open>k AND y div 2 \<le> k\<close>
     by simp
   then show ?case 
     by (simp add: and_int_rec [of \<open>1 + _ * 2\<close>])
 qed (simp_all add: and_int_rec [of \<open>_ * 2\<close>])
 
 lemmas AND_upper1' [simp] = order_trans [OF AND_upper1] \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
 lemmas AND_upper1'' [simp] = order_le_less_trans [OF AND_upper1] \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
 
 lemma AND_upper2 [simp]: \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
   fixes x y :: int
   assumes \<open>0 \<le> y\<close>
   shows \<open>x AND y \<le> y\<close>
   using assms AND_upper1 [of y x] by (simp add: ac_simps)
 
 lemmas AND_upper2' [simp] = order_trans [OF AND_upper2] \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
 lemmas AND_upper2'' [simp] = order_le_less_trans [OF AND_upper2] \<^marker>\<open>contributor \<open>Stefan Berghofer\<close>\<close>
 
 lemma plus_and_or: \<open>(x AND y) + (x OR y) = x + y\<close> for x y :: int
 proof (induction x arbitrary: y rule: int_bit_induct)
   case zero
   then show ?case
     by simp
 next
   case minus
   then show ?case
     by simp
 next
   case (even x)
   from even.IH [of \<open>y div 2\<close>]
   show ?case
     by (auto simp add: and_int_rec [of _ y] or_int_rec [of _ y] elim: oddE)
 next
   case (odd x)
   from odd.IH [of \<open>y div 2\<close>]
   show ?case
     by (auto simp add: and_int_rec [of _ y] or_int_rec [of _ y] elim: oddE)
 qed
 
 lemma push_bit_minus_one:
   "push_bit n (- 1 :: int) = - (2 ^ n)"
   by (simp add: push_bit_eq_mult)
 
 lemma minus_1_div_exp_eq_int:
   \<open>- 1 div (2 :: int) ^ n = - 1\<close>
   by (induction n) (use div_exp_eq [symmetric, of \<open>- 1 :: int\<close> 1] in \<open>simp_all add: ac_simps\<close>)
 
 lemma drop_bit_minus_one [simp]:
   \<open>drop_bit n (- 1 :: int) = - 1\<close>
   by (simp add: drop_bit_eq_div minus_1_div_exp_eq_int)
 
 lemma take_bit_Suc_from_most:
   \<open>take_bit (Suc n) k = 2 ^ n * of_bool (bit k n) + take_bit n k\<close> for k :: int
   by (simp only: take_bit_eq_mod power_Suc2) (simp_all add: bit_iff_odd odd_iff_mod_2_eq_one zmod_zmult2_eq)
 
 lemma take_bit_minus:
   \<open>take_bit n (- take_bit n k) = take_bit n (- k)\<close>
     for k :: int
   by (simp add: take_bit_eq_mod mod_minus_eq)
 
 lemma take_bit_diff:
   \<open>take_bit n (take_bit n k - take_bit n l) = take_bit n (k - l)\<close>
     for k l :: int
   by (simp add: take_bit_eq_mod mod_diff_eq)
 
 lemma bit_imp_take_bit_positive:
   \<open>0 < take_bit m k\<close> if \<open>n < m\<close> and \<open>bit k n\<close> for k :: int
 proof (rule ccontr)
   assume \<open>\<not> 0 < take_bit m k\<close>
   then have \<open>take_bit m k = 0\<close>
     by (auto simp add: not_less intro: order_antisym)
   then have \<open>bit (take_bit m k) n = bit 0 n\<close>
     by simp
   with that show False
     by (simp add: bit_take_bit_iff)
 qed
 
 lemma take_bit_mult:
   \<open>take_bit n (take_bit n k * take_bit n l) = take_bit n (k * l)\<close>
   for k l :: int
   by (simp add: take_bit_eq_mod mod_mult_eq)
 
 lemma (in ring_1) of_nat_nat_take_bit_eq [simp]:
   \<open>of_nat (nat (take_bit n k)) = of_int (take_bit n k)\<close>
   by simp
 
 lemma take_bit_minus_small_eq:
   \<open>take_bit n (- k) = 2 ^ n - k\<close> if \<open>0 < k\<close> \<open>k \<le> 2 ^ n\<close> for k :: int
 proof -
   define m where \<open>m = nat k\<close>
   with that have \<open>k = int m\<close> and \<open>0 < m\<close> and \<open>m \<le> 2 ^ n\<close>
     by simp_all
   have \<open>(2 ^ n - m) mod 2 ^ n = 2 ^ n - m\<close>
     using \<open>0 < m\<close> by simp
   then have \<open>int ((2 ^ n - m) mod 2 ^ n) = int (2 ^ n - m)\<close>
     by simp
   then have \<open>(2 ^ n - int m) mod 2 ^ n = 2 ^ n - int m\<close>
     using \<open>m \<le> 2 ^ n\<close> by (simp only: of_nat_mod of_nat_diff) simp
   with \<open>k = int m\<close> have \<open>(2 ^ n - k) mod 2 ^ n = 2 ^ n - k\<close>
     by simp
   then show ?thesis
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma drop_bit_push_bit_int:
   \<open>drop_bit m (push_bit n k) = drop_bit (m - n) (push_bit (n - m) k)\<close> for k :: int
   by (cases \<open>m \<le> n\<close>) (auto simp add: mult.left_commute [of _ \<open>2 ^ n\<close>] mult.commute [of _ \<open>2 ^ n\<close>] mult.assoc
     mult.commute [of k] drop_bit_eq_div push_bit_eq_mult not_le power_add dest!: le_Suc_ex less_imp_Suc_add)
 
 lemma push_bit_nonnegative_int_iff [simp]:
   \<open>push_bit n k \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (simp add: push_bit_eq_mult zero_le_mult_iff power_le_zero_eq)
 
 lemma push_bit_negative_int_iff [simp]:
   \<open>push_bit n k < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less)
 
 lemma drop_bit_nonnegative_int_iff [simp]:
   \<open>drop_bit n k \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (induction n) (auto simp add: drop_bit_Suc drop_bit_half)
 
 lemma drop_bit_negative_int_iff [simp]:
   \<open>drop_bit n k < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less)
 
 lemma set_bit_nonnegative_int_iff [simp]:
   \<open>set_bit n k \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (simp add: set_bit_def)
 
 lemma set_bit_negative_int_iff [simp]:
   \<open>set_bit n k < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (simp add: set_bit_def)
 
 lemma unset_bit_nonnegative_int_iff [simp]:
   \<open>unset_bit n k \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (simp add: unset_bit_def)
 
 lemma unset_bit_negative_int_iff [simp]:
   \<open>unset_bit n k < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (simp add: unset_bit_def)
 
 lemma flip_bit_nonnegative_int_iff [simp]:
   \<open>flip_bit n k \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
   by (simp add: flip_bit_def)
 
 lemma flip_bit_negative_int_iff [simp]:
   \<open>flip_bit n k < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (simp add: flip_bit_def)
 
 lemma set_bit_greater_eq:
   \<open>set_bit n k \<ge> k\<close> for k :: int
   by (simp add: set_bit_def or_greater_eq)
 
 lemma unset_bit_less_eq:
   \<open>unset_bit n k \<le> k\<close> for k :: int
   by (simp add: unset_bit_def and_less_eq)
 
 lemma set_bit_eq:
   \<open>set_bit n k = k + of_bool (\<not> bit k n) * 2 ^ n\<close> for k :: int
 proof (rule bit_eqI)
   fix m
   show \<open>bit (set_bit n k) m \<longleftrightarrow> bit (k + of_bool (\<not> bit k n) * 2 ^ n) m\<close>
   proof (cases \<open>m = n\<close>)
     case True
     then show ?thesis
       apply (simp add: bit_set_bit_iff)
       apply (simp add: bit_iff_odd div_plus_div_distrib_dvd_right)
       done
   next
     case False
     then show ?thesis
       apply (clarsimp simp add: bit_set_bit_iff)
       apply (subst disjunctive_add)
       apply (clarsimp simp add: bit_exp_iff)
       apply (clarsimp simp add: bit_or_iff bit_exp_iff)
       done
   qed
 qed
 
 lemma unset_bit_eq:
   \<open>unset_bit n k = k - of_bool (bit k n) * 2 ^ n\<close> for k :: int
 proof (rule bit_eqI)
   fix m
   show \<open>bit (unset_bit n k) m \<longleftrightarrow> bit (k - of_bool (bit k n) * 2 ^ n) m\<close>
   proof (cases \<open>m = n\<close>)
     case True
     then show ?thesis
       apply (simp add: bit_unset_bit_iff)
       apply (simp add: bit_iff_odd)
       using div_plus_div_distrib_dvd_right [of \<open>2 ^ n\<close> \<open>- (2 ^ n)\<close> k]
       apply (simp add: dvd_neg_div)
       done
   next
     case False
     then show ?thesis
       apply (clarsimp simp add: bit_unset_bit_iff)
       apply (subst disjunctive_diff)
       apply (clarsimp simp add: bit_exp_iff)
       apply (clarsimp simp add: bit_and_iff bit_not_iff bit_exp_iff)
       done
   qed
 qed
 
 lemma and_int_unfold [code]:
   \<open>k AND l = (if k = 0 \<or> l = 0 then 0 else if k = - 1 then l else if l = - 1 then k
     else (k mod 2) * (l mod 2) + 2 * ((k div 2) AND (l div 2)))\<close> for k l :: int
   by (auto simp add: and_int_rec [of k l] zmult_eq_1_iff elim: oddE)
 
 lemma or_int_unfold [code]:
   \<open>k OR l = (if k = - 1 \<or> l = - 1 then - 1 else if k = 0 then l else if l = 0 then k
     else max (k mod 2) (l mod 2) + 2 * ((k div 2) OR (l div 2)))\<close> for k l :: int
   by (auto simp add: or_int_rec [of k l] elim: oddE)
 
 lemma xor_int_unfold [code]:
   \<open>k XOR l = (if k = - 1 then NOT l else if l = - 1 then NOT k else if k = 0 then l else if l = 0 then k
     else \<bar>k mod 2 - l mod 2\<bar> + 2 * ((k div 2) XOR (l div 2)))\<close> for k l :: int
   by (auto simp add: xor_int_rec [of k l] not_int_def elim!: oddE)
 
 lemma bit_minus_int_iff:
   \<open>bit (- k) n \<longleftrightarrow> bit (NOT (k - 1)) n\<close>
   for k :: int
   by (simp add: bit_simps)
 
 
 subsection \<open>Instance \<^typ>\<open>nat\<close>\<close>
 
 instantiation nat :: semiring_bit_operations
 begin
 
 definition and_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>m AND n = nat (int m AND int n)\<close> for m n :: nat
 
 definition or_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>m OR n = nat (int m OR int n)\<close> for m n :: nat
 
 definition xor_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>m XOR n = nat (int m XOR int n)\<close> for m n :: nat
 
 definition mask_nat :: \<open>nat \<Rightarrow> nat\<close>
   where \<open>mask n = (2 :: nat) ^ n - 1\<close>
 
 definition push_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>push_bit_nat n m = m * 2 ^ n\<close>
 
 definition drop_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>drop_bit_nat n m = m div 2 ^ n\<close>
 
 definition take_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>take_bit_nat n m = m mod 2 ^ n\<close>
 
 definition set_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>set_bit m n = n OR push_bit m 1\<close> for m n :: nat
 
 definition unset_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>unset_bit m n = nat (unset_bit m (int n))\<close> for m n :: nat
 
 definition flip_bit_nat :: \<open>nat \<Rightarrow> nat \<Rightarrow> nat\<close>
   where \<open>flip_bit m n = n XOR push_bit m 1\<close> for m n :: nat
 
 instance proof
   fix m n q :: nat
   show \<open>bit (m AND n) q \<longleftrightarrow> bit m q \<and> bit n q\<close>
     by (simp add: and_nat_def bit_simps)
   show \<open>bit (m OR n) q \<longleftrightarrow> bit m q \<or> bit n q\<close>
     by (simp add: or_nat_def bit_simps)
   show \<open>bit (m XOR n) q \<longleftrightarrow> bit m q \<noteq> bit n q\<close>
     by (simp add: xor_nat_def bit_simps)
   show \<open>bit (unset_bit m n) q \<longleftrightarrow> bit n q \<and> m \<noteq> q\<close>
     by (simp add: unset_bit_nat_def bit_simps)
 qed (simp_all add: mask_nat_def set_bit_nat_def flip_bit_nat_def push_bit_nat_def drop_bit_nat_def take_bit_nat_def)
 
 end
 
 lemma take_bit_nat_less_exp [simp]:
   \<open>take_bit n m < 2 ^ n\<close> for n m ::nat 
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_nat_eq_self_iff:
   \<open>take_bit n m = m \<longleftrightarrow> m < 2 ^ n\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for n m :: nat
 proof
   assume ?P
   moreover note take_bit_nat_less_exp [of n m]
   ultimately show ?Q
     by simp
 next
   assume ?Q
   then show ?P
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma take_bit_nat_eq_self:
   \<open>take_bit n m = m\<close> if \<open>m < 2 ^ n\<close> for m n :: nat
   using that by (simp add: take_bit_nat_eq_self_iff)
 
 lemma take_bit_nat_less_eq_self [simp]:
   \<open>take_bit n m \<le> m\<close> for n m :: nat
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_nat_less_self_iff:
   \<open>take_bit n m < m \<longleftrightarrow> 2 ^ n \<le> m\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for m n :: nat
 proof
   assume ?P
   then have \<open>take_bit n m \<noteq> m\<close>
     by simp
   then show \<open>?Q\<close>
     by (simp add: take_bit_nat_eq_self_iff)
 next
   have \<open>take_bit n m < 2 ^ n\<close>
     by (fact take_bit_nat_less_exp)
   also assume ?Q
   finally show ?P .
 qed
 
 lemma bit_push_bit_iff_nat:
   \<open>bit (push_bit m q) n \<longleftrightarrow> m \<le> n \<and> bit q (n - m)\<close> for q :: nat
   by (auto simp add: bit_push_bit_iff)
 
 lemma and_nat_rec:
   \<open>m AND n = of_bool (odd m \<and> odd n) + 2 * ((m div 2) AND (n div 2))\<close> for m n :: nat
   apply (simp add: and_nat_def and_int_rec [of \<open>int m\<close> \<open>int n\<close>] zdiv_int nat_add_distrib nat_mult_distrib)
   apply (subst nat_add_distrib)
     apply auto
   done
 
 lemma or_nat_rec:
   \<open>m OR n = of_bool (odd m \<or> odd n) + 2 * ((m div 2) OR (n div 2))\<close> for m n :: nat
   apply (simp add: or_nat_def or_int_rec [of \<open>int m\<close> \<open>int n\<close>] zdiv_int nat_add_distrib nat_mult_distrib)
   apply (subst nat_add_distrib)
     apply auto
   done
 
 lemma xor_nat_rec:
   \<open>m XOR n = of_bool (odd m \<noteq> odd n) + 2 * ((m div 2) XOR (n div 2))\<close> for m n :: nat
   apply (simp add: xor_nat_def xor_int_rec [of \<open>int m\<close> \<open>int n\<close>] zdiv_int nat_add_distrib nat_mult_distrib)
   apply (subst nat_add_distrib)
     apply auto
   done
 
 lemma Suc_0_and_eq [simp]:
   \<open>Suc 0 AND n = n mod 2\<close>
   using one_and_eq [of n] by simp
 
 lemma and_Suc_0_eq [simp]:
   \<open>n AND Suc 0 = n mod 2\<close>
   using and_one_eq [of n] by simp
 
 lemma Suc_0_or_eq:
   \<open>Suc 0 OR n = n + of_bool (even n)\<close>
   using one_or_eq [of n] by simp
 
 lemma or_Suc_0_eq:
   \<open>n OR Suc 0 = n + of_bool (even n)\<close>
   using or_one_eq [of n] by simp
 
 lemma Suc_0_xor_eq:
   \<open>Suc 0 XOR n = n + of_bool (even n) - of_bool (odd n)\<close>
   using one_xor_eq [of n] by simp
 
 lemma xor_Suc_0_eq:
   \<open>n XOR Suc 0 = n + of_bool (even n) - of_bool (odd n)\<close>
   using xor_one_eq [of n] by simp
 
 lemma and_nat_unfold [code]:
   \<open>m AND n = (if m = 0 \<or> n = 0 then 0 else (m mod 2) * (n mod 2) + 2 * ((m div 2) AND (n div 2)))\<close>
     for m n :: nat
   by (auto simp add: and_nat_rec [of m n] elim: oddE)
 
 lemma or_nat_unfold [code]:
   \<open>m OR n = (if m = 0 then n else if n = 0 then m
     else max (m mod 2) (n mod 2) + 2 * ((m div 2) OR (n div 2)))\<close> for m n :: nat
   by (auto simp add: or_nat_rec [of m n] elim: oddE)
 
 lemma xor_nat_unfold [code]:
   \<open>m XOR n = (if m = 0 then n else if n = 0 then m
     else (m mod 2 + n mod 2) mod 2 + 2 * ((m div 2) XOR (n div 2)))\<close> for m n :: nat
   by (auto simp add: xor_nat_rec [of m n] elim!: oddE)
 
 lemma [code]:
   \<open>unset_bit 0 m = 2 * (m div 2)\<close>
   \<open>unset_bit (Suc n) m = m mod 2 + 2 * unset_bit n (m div 2)\<close> for m n :: nat
   by (simp_all add: unset_bit_Suc)
   
 
 subsection \<open>Common algebraic structure\<close>
 
 class unique_euclidean_semiring_with_bit_operations =
   unique_euclidean_semiring_with_nat + semiring_bit_operations
 begin
 
 lemma take_bit_of_exp [simp]:
   \<open>take_bit m (2 ^ n) = of_bool (n < m) * 2 ^ n\<close>
   by (simp add: take_bit_eq_mod exp_mod_exp)
 
 lemma take_bit_of_2 [simp]:
   \<open>take_bit n 2 = of_bool (2 \<le> n) * 2\<close>
   using take_bit_of_exp [of n 1] by simp
 
 lemma take_bit_of_mask:
   \<open>take_bit m (2 ^ n - 1) = 2 ^ min m n - 1\<close>
   by (simp add: take_bit_eq_mod mask_mod_exp)
 
 lemma push_bit_eq_0_iff [simp]:
   "push_bit n a = 0 \<longleftrightarrow> a = 0"
   by (simp add: push_bit_eq_mult)
 
 lemma take_bit_add:
   "take_bit n (take_bit n a + take_bit n b) = take_bit n (a + b)"
   by (simp add: take_bit_eq_mod mod_simps)
 
 lemma take_bit_of_1_eq_0_iff [simp]:
   "take_bit n 1 = 0 \<longleftrightarrow> n = 0"
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_Suc_1 [simp]:
   \<open>take_bit (Suc n) 1 = 1\<close>
   by (simp add: take_bit_Suc)
 
 lemma take_bit_Suc_bit0 [simp]:
   \<open>take_bit (Suc n) (numeral (Num.Bit0 k)) = take_bit n (numeral k) * 2\<close>
   by (simp add: take_bit_Suc numeral_Bit0_div_2)
 
 lemma take_bit_Suc_bit1 [simp]:
   \<open>take_bit (Suc n) (numeral (Num.Bit1 k)) = take_bit n (numeral k) * 2 + 1\<close>
   by (simp add: take_bit_Suc numeral_Bit1_div_2 mod_2_eq_odd)
 
 lemma take_bit_numeral_1 [simp]:
   \<open>take_bit (numeral l) 1 = 1\<close>
   by (simp add: take_bit_rec [of \<open>numeral l\<close> 1])
 
 lemma take_bit_numeral_bit0 [simp]:
   \<open>take_bit (numeral l) (numeral (Num.Bit0 k)) = take_bit (pred_numeral l) (numeral k) * 2\<close>
   by (simp add: take_bit_rec numeral_Bit0_div_2)
 
 lemma take_bit_numeral_bit1 [simp]:
   \<open>take_bit (numeral l) (numeral (Num.Bit1 k)) = take_bit (pred_numeral l) (numeral k) * 2 + 1\<close>
   by (simp add: take_bit_rec numeral_Bit1_div_2 mod_2_eq_odd)
 
 lemma drop_bit_Suc_bit0 [simp]:
   \<open>drop_bit (Suc n) (numeral (Num.Bit0 k)) = drop_bit n (numeral k)\<close>
   by (simp add: drop_bit_Suc numeral_Bit0_div_2)
 
 lemma drop_bit_Suc_bit1 [simp]:
   \<open>drop_bit (Suc n) (numeral (Num.Bit1 k)) = drop_bit n (numeral k)\<close>
   by (simp add: drop_bit_Suc numeral_Bit1_div_2)
 
 lemma drop_bit_numeral_bit0 [simp]:
   \<open>drop_bit (numeral l) (numeral (Num.Bit0 k)) = drop_bit (pred_numeral l) (numeral k)\<close>
   by (simp add: drop_bit_rec numeral_Bit0_div_2)
 
 lemma drop_bit_numeral_bit1 [simp]:
   \<open>drop_bit (numeral l) (numeral (Num.Bit1 k)) = drop_bit (pred_numeral l) (numeral k)\<close>
   by (simp add: drop_bit_rec numeral_Bit1_div_2)
 
 lemma drop_bit_of_nat:
   "drop_bit n (of_nat m) = of_nat (drop_bit n m)"
   by (simp add: drop_bit_eq_div Bit_Operations.drop_bit_eq_div of_nat_div [of m "2 ^ n"])
 
 lemma bit_of_nat_iff_bit [bit_simps]:
   \<open>bit (of_nat m) n \<longleftrightarrow> bit m n\<close>
 proof -
   have \<open>even (m div 2 ^ n) \<longleftrightarrow> even (of_nat (m div 2 ^ n))\<close>
     by simp
   also have \<open>of_nat (m div 2 ^ n) = of_nat m div of_nat (2 ^ n)\<close>
     by (simp add: of_nat_div)
   finally show ?thesis
     by (simp add: bit_iff_odd semiring_bits_class.bit_iff_odd)
 qed
 
 lemma of_nat_drop_bit:
   \<open>of_nat (drop_bit m n) = drop_bit m (of_nat n)\<close>
   by (simp add: drop_bit_eq_div Bit_Operations.drop_bit_eq_div of_nat_div)
 
 lemma take_bit_sum:
   "take_bit n a = (\<Sum>k = 0..<n. push_bit k (of_bool (bit a k)))"
   for n :: nat
 proof (induction n arbitrary: a)
   case 0
   then show ?case
     by simp
 next
   case (Suc n)
   have "(\<Sum>k = 0..<Suc n. push_bit k (of_bool (bit a k))) = 
     of_bool (odd a) + (\<Sum>k = Suc 0..<Suc n. push_bit k (of_bool (bit a k)))"
     by (simp add: sum.atLeast_Suc_lessThan ac_simps)
   also have "(\<Sum>k = Suc 0..<Suc n. push_bit k (of_bool (bit a k)))
     = (\<Sum>k = 0..<n. push_bit k (of_bool (bit (a div 2) k))) * 2"
     by (simp only: sum.atLeast_Suc_lessThan_Suc_shift) (simp add: sum_distrib_right push_bit_double drop_bit_Suc bit_Suc)
   finally show ?case
     using Suc [of "a div 2"] by (simp add: ac_simps take_bit_Suc mod_2_eq_odd)
 qed
 
 end
 
 instance nat :: unique_euclidean_semiring_with_bit_operations ..
 
 instance int :: unique_euclidean_semiring_with_bit_operations ..
 
 
 subsection \<open>Symbolic computations on numeral expressions\<close>
 
 context unique_euclidean_semiring_with_bit_operations
 begin
 
 lemma bit_numeral_iff:
   \<open>bit (numeral m) n \<longleftrightarrow> bit (numeral m :: nat) n\<close>
   using bit_of_nat_iff_bit [of \<open>numeral m\<close> n] by simp
 
 lemma bit_numeral_Bit0_Suc_iff [simp]:
   \<open>bit (numeral (Num.Bit0 m)) (Suc n) \<longleftrightarrow> bit (numeral m) n\<close>
   by (simp add: bit_Suc numeral_Bit0_div_2)
 
 lemma bit_numeral_Bit1_Suc_iff [simp]:
   \<open>bit (numeral (Num.Bit1 m)) (Suc n) \<longleftrightarrow> bit (numeral m) n\<close>
   by (simp add: bit_Suc numeral_Bit1_div_2)
 
 lemma bit_numeral_rec:
   \<open>bit (numeral (Num.Bit0 w)) n \<longleftrightarrow> (case n of 0 \<Rightarrow> False | Suc m \<Rightarrow> bit (numeral w) m)\<close>
   \<open>bit (numeral (Num.Bit1 w)) n \<longleftrightarrow> (case n of 0 \<Rightarrow> True | Suc m \<Rightarrow> bit (numeral w) m)\<close>
   by (cases n; simp)+
 
 lemma bit_numeral_simps [simp]:
   \<open>\<not> bit 1 (numeral n)\<close>
   \<open>bit (numeral (Num.Bit0 w)) (numeral n) \<longleftrightarrow> bit (numeral w) (pred_numeral n)\<close>
   \<open>bit (numeral (Num.Bit1 w)) (numeral n) \<longleftrightarrow> bit (numeral w) (pred_numeral n)\<close>
   by (simp_all add: bit_1_iff numeral_eq_Suc)
 
 lemma and_numerals [simp]:
   \<open>1 AND numeral (Num.Bit0 y) = 0\<close>
   \<open>1 AND numeral (Num.Bit1 y) = 1\<close>
   \<open>numeral (Num.Bit0 x) AND numeral (Num.Bit0 y) = 2 * (numeral x AND numeral y)\<close>
   \<open>numeral (Num.Bit0 x) AND numeral (Num.Bit1 y) = 2 * (numeral x AND numeral y)\<close>
   \<open>numeral (Num.Bit0 x) AND 1 = 0\<close>
   \<open>numeral (Num.Bit1 x) AND numeral (Num.Bit0 y) = 2 * (numeral x AND numeral y)\<close>
   \<open>numeral (Num.Bit1 x) AND numeral (Num.Bit1 y) = 1 + 2 * (numeral x AND numeral y)\<close>
   \<open>numeral (Num.Bit1 x) AND 1 = 1\<close>
   by (simp_all add: bit_eq_iff) (simp_all add: bit_simps bit_Suc bit_numeral_rec split: nat.splits)
 
 fun and_num :: \<open>num \<Rightarrow> num \<Rightarrow> num option\<close> \<^marker>\<open>contributor \<open>Andreas Lochbihler\<close>\<close>
 where
   \<open>and_num num.One num.One = Some num.One\<close>
 | \<open>and_num num.One (num.Bit0 n) = None\<close>
 | \<open>and_num num.One (num.Bit1 n) = Some num.One\<close>
 | \<open>and_num (num.Bit0 m) num.One = None\<close>
 | \<open>and_num (num.Bit0 m) (num.Bit0 n) = map_option num.Bit0 (and_num m n)\<close>
 | \<open>and_num (num.Bit0 m) (num.Bit1 n) = map_option num.Bit0 (and_num m n)\<close>
 | \<open>and_num (num.Bit1 m) num.One = Some num.One\<close>
 | \<open>and_num (num.Bit1 m) (num.Bit0 n) = map_option num.Bit0 (and_num m n)\<close>
 | \<open>and_num (num.Bit1 m) (num.Bit1 n) = (case and_num m n of None \<Rightarrow> Some num.One | Some n' \<Rightarrow> Some (num.Bit1 n'))\<close>
 
 lemma numeral_and_num:
   \<open>numeral m AND numeral n = (case and_num m n of None \<Rightarrow> 0 | Some n' \<Rightarrow> numeral n')\<close>
   by (induction m n rule: and_num.induct) (simp_all add: split: option.split)
 
 lemma and_num_eq_None_iff:
   \<open>and_num m n = None \<longleftrightarrow> numeral m AND numeral n = 0\<close>
   by (simp add: numeral_and_num split: option.split)
 
 lemma and_num_eq_Some_iff:
   \<open>and_num m n = Some q \<longleftrightarrow> numeral m AND numeral n = numeral q\<close>
   by (simp add: numeral_and_num split: option.split)
 
 lemma or_numerals [simp]:
   \<open>1 OR numeral (Num.Bit0 y) = numeral (Num.Bit1 y)\<close>
   \<open>1 OR numeral (Num.Bit1 y) = numeral (Num.Bit1 y)\<close>
   \<open>numeral (Num.Bit0 x) OR numeral (Num.Bit0 y) = 2 * (numeral x OR numeral y)\<close>
   \<open>numeral (Num.Bit0 x) OR numeral (Num.Bit1 y) = 1 + 2 * (numeral x OR numeral y)\<close>
   \<open>numeral (Num.Bit0 x) OR 1 = numeral (Num.Bit1 x)\<close>
   \<open>numeral (Num.Bit1 x) OR numeral (Num.Bit0 y) = 1 + 2 * (numeral x OR numeral y)\<close>
   \<open>numeral (Num.Bit1 x) OR numeral (Num.Bit1 y) = 1 + 2 * (numeral x OR numeral y)\<close>
   \<open>numeral (Num.Bit1 x) OR 1 = numeral (Num.Bit1 x)\<close>
   by (simp_all add: bit_eq_iff) (simp_all add: bit_simps bit_Suc bit_numeral_rec split: nat.splits)
 
 fun or_num :: \<open>num \<Rightarrow> num \<Rightarrow> num\<close> \<^marker>\<open>contributor \<open>Andreas Lochbihler\<close>\<close>
 where
   \<open>or_num num.One num.One = num.One\<close>
 | \<open>or_num num.One (num.Bit0 n) = num.Bit1 n\<close>
 | \<open>or_num num.One (num.Bit1 n) = num.Bit1 n\<close>
 | \<open>or_num (num.Bit0 m) num.One = num.Bit1 m\<close>
 | \<open>or_num (num.Bit0 m) (num.Bit0 n) = num.Bit0 (or_num m n)\<close>
 | \<open>or_num (num.Bit0 m) (num.Bit1 n) = num.Bit1 (or_num m n)\<close>
 | \<open>or_num (num.Bit1 m) num.One = num.Bit1 m\<close>
 | \<open>or_num (num.Bit1 m) (num.Bit0 n) = num.Bit1 (or_num m n)\<close>
 | \<open>or_num (num.Bit1 m) (num.Bit1 n) = num.Bit1 (or_num m n)\<close>
 
 lemma numeral_or_num:
   \<open>numeral m OR numeral n = numeral (or_num m n)\<close>
   by (induction m n rule: or_num.induct) simp_all
 
 lemma numeral_or_num_eq:
   \<open>numeral (or_num m n) = numeral m OR numeral n\<close>
   by (simp add: numeral_or_num)
 
 lemma xor_numerals [simp]:
   \<open>1 XOR numeral (Num.Bit0 y) = numeral (Num.Bit1 y)\<close>
   \<open>1 XOR numeral (Num.Bit1 y) = numeral (Num.Bit0 y)\<close>
   \<open>numeral (Num.Bit0 x) XOR numeral (Num.Bit0 y) = 2 * (numeral x XOR numeral y)\<close>
   \<open>numeral (Num.Bit0 x) XOR numeral (Num.Bit1 y) = 1 + 2 * (numeral x XOR numeral y)\<close>
   \<open>numeral (Num.Bit0 x) XOR 1 = numeral (Num.Bit1 x)\<close>
   \<open>numeral (Num.Bit1 x) XOR numeral (Num.Bit0 y) = 1 + 2 * (numeral x XOR numeral y)\<close>
   \<open>numeral (Num.Bit1 x) XOR numeral (Num.Bit1 y) = 2 * (numeral x XOR numeral y)\<close>
   \<open>numeral (Num.Bit1 x) XOR 1 = numeral (Num.Bit0 x)\<close>
   by (simp_all add: bit_eq_iff) (simp_all add: bit_simps bit_Suc bit_numeral_rec split: nat.splits)
 
 fun xor_num :: \<open>num \<Rightarrow> num \<Rightarrow> num option\<close> \<^marker>\<open>contributor \<open>Andreas Lochbihler\<close>\<close>
 where
   \<open>xor_num num.One num.One = None\<close>
 | \<open>xor_num num.One (num.Bit0 n) = Some (num.Bit1 n)\<close>
 | \<open>xor_num num.One (num.Bit1 n) = Some (num.Bit0 n)\<close>
 | \<open>xor_num (num.Bit0 m) num.One = Some (num.Bit1 m)\<close>
 | \<open>xor_num (num.Bit0 m) (num.Bit0 n) = map_option num.Bit0 (xor_num m n)\<close>
 | \<open>xor_num (num.Bit0 m) (num.Bit1 n) = Some (case xor_num m n of None \<Rightarrow> num.One | Some n' \<Rightarrow> num.Bit1 n')\<close>
 | \<open>xor_num (num.Bit1 m) num.One = Some (num.Bit0 m)\<close>
 | \<open>xor_num (num.Bit1 m) (num.Bit0 n) = Some (case xor_num m n of None \<Rightarrow> num.One | Some n' \<Rightarrow> num.Bit1 n')\<close>
 | \<open>xor_num (num.Bit1 m) (num.Bit1 n) = map_option num.Bit0 (xor_num m n)\<close>
 
 lemma numeral_xor_num:
   \<open>numeral m XOR numeral n = (case xor_num m n of None \<Rightarrow> 0 | Some n' \<Rightarrow> numeral n')\<close>
   by (induction m n rule: xor_num.induct) (simp_all split: option.split)
 
 lemma xor_num_eq_None_iff:
   \<open>xor_num m n = None \<longleftrightarrow> numeral m XOR numeral n = 0\<close>
   by (simp add: numeral_xor_num split: option.split)
 
 lemma xor_num_eq_Some_iff:
   \<open>xor_num m n = Some q \<longleftrightarrow> numeral m XOR numeral n = numeral q\<close>
   by (simp add: numeral_xor_num split: option.split)
 
 end
 
 context ring_bit_operations
 begin
 
 lemma minus_numeral_inc_eq:
   \<open>- numeral (Num.inc n) = NOT (numeral n)\<close>
   by (simp add: not_eq_complement sub_inc_One_eq add_One)
 
 lemma sub_one_eq_not_neg:
   \<open>Num.sub n num.One = NOT (- numeral n)\<close>
   by (simp add: not_eq_complement)
 
 lemma minus_numeral_eq_not_sub_one:
   \<open>- numeral n = NOT (Num.sub n num.One)\<close>
   by (simp add: not_eq_complement)
 
 lemma not_numeral_eq:
   \<open>NOT (numeral n) = - numeral (Num.inc n)\<close>
   by (simp add: minus_numeral_inc_eq)
 
 lemma not_minus_numeral_eq [simp]:
   \<open>NOT (- numeral n) = Num.sub n num.One\<close>
   by (simp add: sub_one_eq_not_neg)
 
 lemma minus_not_numeral_eq [simp]:
   \<open>- (NOT (numeral n)) = numeral (Num.inc n)\<close>
   by (simp add: not_numeral_eq)
 
 end
 
 lemma bit_minus_numeral_int [simp]:
   \<open>bit (- numeral (num.Bit0 w) :: int) (numeral n) \<longleftrightarrow> bit (- numeral w :: int) (pred_numeral n)\<close>
   \<open>bit (- numeral (num.Bit1 w) :: int) (numeral n) \<longleftrightarrow> \<not> bit (numeral w :: int) (pred_numeral n)\<close>
   by (simp_all add: bit_minus_iff bit_not_iff numeral_eq_Suc bit_Suc add_One sub_inc_One_eq)
 
 lemma and_not_numerals [simp]:
   \<open>1 AND NOT 1 = (0 :: int)\<close>
   \<open>1 AND NOT (numeral (Num.Bit0 n)) = (1 :: int)\<close>
   \<open>1 AND NOT (numeral (Num.Bit1 n)) = (0 :: int)\<close>
   \<open>numeral (Num.Bit0 m) AND NOT (1 :: int) = numeral (Num.Bit0 m)\<close>
   \<open>numeral (Num.Bit0 m) AND NOT (numeral (Num.Bit0 n)) = (2 :: int) * (numeral m AND NOT (numeral n))\<close>
   \<open>numeral (Num.Bit0 m) AND NOT (numeral (Num.Bit1 n)) = (2 :: int) * (numeral m AND NOT (numeral n))\<close>
   \<open>numeral (Num.Bit1 m) AND NOT (1 :: int) = numeral (Num.Bit0 m)\<close>
   \<open>numeral (Num.Bit1 m) AND NOT (numeral (Num.Bit0 n)) = 1 + (2 :: int) * (numeral m AND NOT (numeral n))\<close>
   \<open>numeral (Num.Bit1 m) AND NOT (numeral (Num.Bit1 n)) = (2 :: int) * (numeral m AND NOT (numeral n))\<close>
   by (simp_all add: bit_eq_iff) (auto simp add: bit_simps bit_Suc bit_numeral_rec BitM_inc_eq split: nat.splits)
 
 lemma and_not_not_numerals [simp]:
   \<open>NOT 1 AND NOT 1 = NOT (1 :: int)\<close>
   \<open>NOT 1 AND NOT (numeral n) = NOT (1 OR numeral n :: int)\<close>
   \<open>NOT (numeral m) AND NOT 1 = NOT (numeral m OR 1 :: int)\<close>
   \<open>NOT (numeral m) AND NOT (numeral n) = NOT (numeral m OR numeral n :: int)\<close>
   by simp_all
 
 lemma and_minus_numerals [simp]:
   \<open>- 1 AND k = k\<close>
   \<open>k AND - 1 = k\<close>
   \<open>- numeral n AND k = NOT (neg_numeral_class.sub n num.One) AND k\<close>
   \<open>k AND - numeral n = k AND NOT (neg_numeral_class.sub n num.One)\<close> for k :: int
   by (simp_all add: minus_numeral_eq_not_sub_one)
 
 fun and_not_num :: \<open>num \<Rightarrow> num \<Rightarrow> num option\<close> \<^marker>\<open>contributor \<open>Andreas Lochbihler\<close>\<close>
 where
   \<open>and_not_num num.One num.One = None\<close>
 | \<open>and_not_num num.One (num.Bit0 n) = Some num.One\<close>
 | \<open>and_not_num num.One (num.Bit1 n) = None\<close>
 | \<open>and_not_num (num.Bit0 m) num.One = Some (num.Bit0 m)\<close>
 | \<open>and_not_num (num.Bit0 m) (num.Bit0 n) = map_option num.Bit0 (and_not_num m n)\<close>
 | \<open>and_not_num (num.Bit0 m) (num.Bit1 n) = map_option num.Bit0 (and_not_num m n)\<close>
 | \<open>and_not_num (num.Bit1 m) num.One = Some (num.Bit0 m)\<close>
 | \<open>and_not_num (num.Bit1 m) (num.Bit0 n) = (case and_not_num m n of None \<Rightarrow> Some num.One | Some n' \<Rightarrow> Some (num.Bit1 n'))\<close>
 | \<open>and_not_num (num.Bit1 m) (num.Bit1 n) = map_option num.Bit0 (and_not_num m n)\<close>
 
 lemma int_numeral_and_not_num:
   \<open>numeral m AND NOT (numeral n) = (case and_not_num m n of None \<Rightarrow> 0 :: int | Some n' \<Rightarrow> numeral n')\<close>
   by (induction m n rule: and_not_num.induct) (simp_all split: option.split)
 
 lemma int_numeral_not_and_num:
   \<open>NOT (numeral m) AND numeral n = (case and_not_num n m of None \<Rightarrow> 0 :: int | Some n' \<Rightarrow> numeral n')\<close>
   using int_numeral_and_not_num [of n m] by (simp add: ac_simps)
 
 lemma and_not_num_eq_None_iff:
   \<open>and_not_num m n = None \<longleftrightarrow> numeral m AND NOT (numeral n) = (0 :: int)\<close>
   by (simp add: int_numeral_and_not_num split: option.split)
 
 lemma and_not_num_eq_Some_iff:
   \<open>and_not_num m n = Some q \<longleftrightarrow> numeral m AND NOT (numeral n) = (numeral q :: int)\<close>
   by (simp add: int_numeral_and_not_num split: option.split)
 
 lemma or_not_numerals [simp]:
   \<open>1 OR NOT 1 = NOT (0 :: int)\<close>
   \<open>1 OR NOT (numeral (Num.Bit0 n)) = NOT (numeral (Num.Bit0 n) :: int)\<close>
   \<open>1 OR NOT (numeral (Num.Bit1 n)) = NOT (numeral (Num.Bit0 n) :: int)\<close>
   \<open>numeral (Num.Bit0 m) OR NOT (1 :: int) = NOT (1 :: int)\<close>
   \<open>numeral (Num.Bit0 m) OR NOT (numeral (Num.Bit0 n)) = 1 + (2 :: int) * (numeral m OR NOT (numeral n))\<close>
   \<open>numeral (Num.Bit0 m) OR NOT (numeral (Num.Bit1 n)) = (2 :: int) * (numeral m OR NOT (numeral n))\<close>
   \<open>numeral (Num.Bit1 m) OR NOT (1 :: int) = NOT (0 :: int)\<close>
   \<open>numeral (Num.Bit1 m) OR NOT (numeral (Num.Bit0 n)) = 1 + (2 :: int) * (numeral m OR NOT (numeral n))\<close>
   \<open>numeral (Num.Bit1 m) OR NOT (numeral (Num.Bit1 n)) = 1 + (2 :: int) * (numeral m OR NOT (numeral n))\<close>
   by (simp_all add: bit_eq_iff) (simp_all add: bit_simps bit_Suc bit_numeral_rec split: nat.splits)
 
 lemma or_and_numerals [simp]:
   \<open>NOT 1 OR 1 = NOT (0 :: int)\<close>
   \<open>NOT 1 OR numeral n = numeral n OR NOT (1 :: int)\<close>
   \<open>NOT (numeral m) OR 1 = 1 OR NOT (numeral m :: int)\<close>
   \<open>NOT (numeral m) OR (numeral n) = numeral n OR NOT (numeral m :: int)\<close>
   by (simp_all add: ac_simps)
 
 lemma or_not_not_numerals [simp]:
   \<open>NOT 1 OR NOT 1 = NOT (1 :: int)\<close>
   \<open>NOT 1 OR NOT (numeral n) = NOT (1 AND numeral n :: int)\<close>
   \<open>NOT (numeral m) OR NOT 1 = NOT (numeral m AND 1 :: int)\<close>
   \<open>NOT (numeral m) OR NOT (numeral n) = NOT (numeral m AND numeral n :: int)\<close>
   by simp_all
 
 lemma or_minus_numerals [simp]:
   \<open>- 1 OR k = - 1\<close>
   \<open>k OR - 1 = - 1\<close>
   \<open>- numeral n OR k = NOT (neg_numeral_class.sub n num.One) OR k\<close>
   \<open>k OR - numeral n = k OR NOT (neg_numeral_class.sub n num.One)\<close> for k :: int
   by (simp_all add: minus_numeral_eq_not_sub_one)
 
 fun or_not_num_neg :: \<open>num \<Rightarrow> num \<Rightarrow> num\<close> \<^marker>\<open>contributor \<open>Andreas Lochbihler\<close>\<close>
 where
   \<open>or_not_num_neg num.One num.One = num.One\<close>
 | \<open>or_not_num_neg num.One (num.Bit0 m) = num.Bit1 m\<close>
 | \<open>or_not_num_neg num.One (num.Bit1 m) = num.Bit1 m\<close>
 | \<open>or_not_num_neg (num.Bit0 n) num.One = num.Bit0 num.One\<close>
 | \<open>or_not_num_neg (num.Bit0 n) (num.Bit0 m) = Num.BitM (or_not_num_neg n m)\<close>
 | \<open>or_not_num_neg (num.Bit0 n) (num.Bit1 m) = num.Bit0 (or_not_num_neg n m)\<close>
 | \<open>or_not_num_neg (num.Bit1 n) num.One = num.One\<close>
 | \<open>or_not_num_neg (num.Bit1 n) (num.Bit0 m) = Num.BitM (or_not_num_neg n m)\<close>
 | \<open>or_not_num_neg (num.Bit1 n) (num.Bit1 m) = Num.BitM (or_not_num_neg n m)\<close>
 
 lemma int_numeral_or_not_num_neg:
   \<open>numeral m OR NOT (numeral n :: int) = - numeral (or_not_num_neg m n)\<close>
   apply (induction m n rule: or_not_num_neg.induct)
   apply simp_all
     apply (simp_all add: not_one_eq not_numeral_eq)
   done
 
 lemma int_numeral_not_or_num_neg:
   \<open>NOT (numeral m) OR (numeral n :: int) = - numeral (or_not_num_neg n m)\<close>
   using int_numeral_or_not_num_neg [of n m] by (simp add: ac_simps)
 
 lemma numeral_or_not_num_eq:
   \<open>numeral (or_not_num_neg m n) = - (numeral m OR NOT (numeral n :: int))\<close>
   using int_numeral_or_not_num_neg [of m n] by simp
 
 lemma xor_minus_numerals [simp]:
   \<open>- 1 XOR k = NOT k\<close>
   \<open>k XOR - 1 = NOT k\<close>
   \<open>- numeral n XOR k = NOT (neg_numeral_class.sub n num.One XOR k)\<close>
   \<open>k XOR - numeral n = NOT (k XOR (neg_numeral_class.sub n num.One))\<close> for k :: int
   by (simp_all add: minus_numeral_eq_not_sub_one)
 
 
 subsection \<open>More properties\<close>
 
 lemma take_bit_eq_mask_iff:
   \<open>take_bit n k = mask n \<longleftrightarrow> take_bit n (k + 1) = 0\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for k :: int
 proof
   assume ?P
   then have \<open>take_bit n (take_bit n k + take_bit n 1) = 0\<close>
     by (simp add: mask_eq_exp_minus_1 take_bit_eq_0_iff)
   then show ?Q
     by (simp only: take_bit_add)
 next
   assume ?Q
   then have \<open>take_bit n (k + 1) - 1 = - 1\<close>
     by simp
   then have \<open>take_bit n (take_bit n (k + 1) - 1) = take_bit n (- 1)\<close>
     by simp
   moreover have \<open>take_bit n (take_bit n (k + 1) - 1) = take_bit n k\<close>
     by (simp add: take_bit_eq_mod mod_simps)
   ultimately show ?P
     by (simp add: take_bit_minus_one_eq_mask)
 qed
 
 lemma take_bit_eq_mask_iff_exp_dvd:
   \<open>take_bit n k = mask n \<longleftrightarrow> 2 ^ n dvd k + 1\<close>
   for k :: int
   by (simp add: take_bit_eq_mask_iff flip: take_bit_eq_0_iff)
 
 context ring_bit_operations
 begin
 
 lemma even_of_int_iff:
   \<open>even (of_int k) \<longleftrightarrow> even k\<close>
   by (induction k rule: int_bit_induct) simp_all
 
 lemma bit_of_int_iff [bit_simps]:
-  \<open>bit (of_int k) n \<longleftrightarrow> (2::'a) ^ n \<noteq> 0 \<and> bit k n\<close>
-proof (cases \<open>(2::'a) ^ n = 0\<close>)
+  \<open>bit (of_int k) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> bit k n\<close>
+proof (cases \<open>possible_bit TYPE('a) n\<close>)
+  case False
+  then show ?thesis
+    by (simp add: impossible_bit)
+next
   case True
-  then show ?thesis
-    by (simp add: exp_eq_0_imp_not_bit)
-next
-  case False
   then have \<open>bit (of_int k) n \<longleftrightarrow> bit k n\<close>
   proof (induction k arbitrary: n rule: int_bit_induct)
     case zero
     then show ?case
       by simp
   next
     case minus
     then show ?case
       by simp
   next
     case (even k)
     then show ?case
       using bit_double_iff [of \<open>of_int k\<close> n] Bit_Operations.bit_double_iff [of k n]
-      by (cases n) (auto simp add: ac_simps dest: mult_not_zero)
+      by (cases n) (auto simp add: ac_simps possible_bit_def dest: mult_not_zero)
   next
     case (odd k)
     then show ?case
       using bit_double_iff [of \<open>of_int k\<close> n]
-      by (cases n) (auto simp add: ac_simps bit_double_iff even_bit_succ_iff Bit_Operations.bit_Suc dest: mult_not_zero)
+      by (cases n) (auto simp add: ac_simps bit_double_iff even_bit_succ_iff Bit_Operations.bit_Suc possible_bit_def dest: mult_not_zero)
   qed
-  with False show ?thesis
+  with True show ?thesis
     by simp
 qed
 
 lemma push_bit_of_int:
   \<open>push_bit n (of_int k) = of_int (push_bit n k)\<close>
   by (simp add: push_bit_eq_mult Bit_Operations.push_bit_eq_mult)
 
 lemma of_int_push_bit:
   \<open>of_int (push_bit n k) = push_bit n (of_int k)\<close>
   by (simp add: push_bit_eq_mult Bit_Operations.push_bit_eq_mult)
 
 lemma take_bit_of_int:
   \<open>take_bit n (of_int k) = of_int (take_bit n k)\<close>
   by (rule bit_eqI) (simp add: bit_take_bit_iff Bit_Operations.bit_take_bit_iff bit_of_int_iff)
 
 lemma of_int_take_bit:
   \<open>of_int (take_bit n k) = take_bit n (of_int k)\<close>
   by (rule bit_eqI) (simp add: bit_take_bit_iff Bit_Operations.bit_take_bit_iff bit_of_int_iff)
 
 lemma of_int_not_eq:
   \<open>of_int (NOT k) = NOT (of_int k)\<close>
   by (rule bit_eqI) (simp add: bit_not_iff Bit_Operations.bit_not_iff bit_of_int_iff)
 
 lemma of_int_not_numeral:
   \<open>of_int (NOT (numeral k)) = NOT (numeral k)\<close>
   by (simp add: local.of_int_not_eq)
 
 lemma of_int_and_eq:
   \<open>of_int (k AND l) = of_int k AND of_int l\<close>
   by (rule bit_eqI) (simp add: bit_of_int_iff bit_and_iff Bit_Operations.bit_and_iff)
 
 lemma of_int_or_eq:
   \<open>of_int (k OR l) = of_int k OR of_int l\<close>
   by (rule bit_eqI) (simp add: bit_of_int_iff bit_or_iff Bit_Operations.bit_or_iff)
 
 lemma of_int_xor_eq:
   \<open>of_int (k XOR l) = of_int k XOR of_int l\<close>
   by (rule bit_eqI) (simp add: bit_of_int_iff bit_xor_iff Bit_Operations.bit_xor_iff)
 
 lemma of_int_mask_eq:
   \<open>of_int (mask n) = mask n\<close>
   by (induction n) (simp_all add: mask_Suc_double Bit_Operations.mask_Suc_double of_int_or_eq)
 
 end
 
 lemma take_bit_incr_eq:
   \<open>take_bit n (k + 1) = 1 + take_bit n k\<close> if \<open>take_bit n k \<noteq> 2 ^ n - 1\<close>
   for k :: int
 proof -
   from that have \<open>2 ^ n \<noteq> k mod 2 ^ n + 1\<close>
     by (simp add: take_bit_eq_mod)
   moreover have \<open>k mod 2 ^ n < 2 ^ n\<close>
     by simp
   ultimately have *: \<open>k mod 2 ^ n + 1 < 2 ^ n\<close>
     by linarith
   have \<open>(k + 1) mod 2 ^ n = (k mod 2 ^ n + 1) mod 2 ^ n\<close>
     by (simp add: mod_simps)
   also have \<open>\<dots> = k mod 2 ^ n + 1\<close>
     using * by (simp add: zmod_trivial_iff)
   finally have \<open>(k + 1) mod 2 ^ n = k mod 2 ^ n + 1\<close> .
   then show ?thesis
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma take_bit_decr_eq:
   \<open>take_bit n (k - 1) = take_bit n k - 1\<close> if \<open>take_bit n k \<noteq> 0\<close>
   for k :: int
 proof -
   from that have \<open>k mod 2 ^ n \<noteq> 0\<close>
     by (simp add: take_bit_eq_mod)
   moreover have \<open>k mod 2 ^ n \<ge> 0\<close> \<open>k mod 2 ^ n < 2 ^ n\<close>
     by simp_all
   ultimately have *: \<open>k mod 2 ^ n > 0\<close>
     by linarith
   have \<open>(k - 1) mod 2 ^ n = (k mod 2 ^ n - 1) mod 2 ^ n\<close>
     by (simp add: mod_simps)
   also have \<open>\<dots> = k mod 2 ^ n - 1\<close>
     by (simp add: zmod_trivial_iff)
       (use \<open>k mod 2 ^ n < 2 ^ n\<close> * in linarith)
   finally have \<open>(k - 1) mod 2 ^ n = k mod 2 ^ n - 1\<close> .
   then show ?thesis
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma take_bit_int_greater_eq:
   \<open>k + 2 ^ n \<le> take_bit n k\<close> if \<open>k < 0\<close> for k :: int
 proof -
   have \<open>k + 2 ^ n \<le> take_bit n (k + 2 ^ n)\<close>
   proof (cases \<open>k > - (2 ^ n)\<close>)
     case False
     then have \<open>k + 2 ^ n \<le> 0\<close>
       by simp
     also note take_bit_nonnegative
     finally show ?thesis .
   next
     case True
     with that have \<open>0 \<le> k + 2 ^ n\<close> and \<open>k + 2 ^ n < 2 ^ n\<close>
       by simp_all
     then show ?thesis
       by (simp only: take_bit_eq_mod mod_pos_pos_trivial)
   qed
   then show ?thesis
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma take_bit_int_less_eq:
   \<open>take_bit n k \<le> k - 2 ^ n\<close> if \<open>2 ^ n \<le> k\<close> and \<open>n > 0\<close> for k :: int
   using that zmod_le_nonneg_dividend [of \<open>k - 2 ^ n\<close> \<open>2 ^ n\<close>]
   by (simp add: take_bit_eq_mod)
 
 lemma take_bit_int_less_eq_self_iff:
   \<open>take_bit n k \<le> k \<longleftrightarrow> 0 \<le> k\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for k :: int
 proof
   assume ?P
   show ?Q
   proof (rule ccontr)
     assume \<open>\<not> 0 \<le> k\<close>
     then have \<open>k < 0\<close>
       by simp
     with \<open>?P\<close>
     have \<open>take_bit n k < 0\<close>
       by (rule le_less_trans)
     then show False
       by simp
   qed
 next
   assume ?Q
   then show ?P
     by (simp add: take_bit_eq_mod zmod_le_nonneg_dividend)
 qed
 
 lemma take_bit_int_less_self_iff:
   \<open>take_bit n k < k \<longleftrightarrow> 2 ^ n \<le> k\<close>
   for k :: int
   by (auto simp add: less_le take_bit_int_less_eq_self_iff take_bit_int_eq_self_iff
     intro: order_trans [of 0 \<open>2 ^ n\<close> k])
 
 lemma take_bit_int_greater_self_iff:
   \<open>k < take_bit n k \<longleftrightarrow> k < 0\<close>
   for k :: int
   using take_bit_int_less_eq_self_iff [of n k] by auto
 
 lemma take_bit_int_greater_eq_self_iff:
   \<open>k \<le> take_bit n k \<longleftrightarrow> k < 2 ^ n\<close>
   for k :: int
   by (auto simp add: le_less take_bit_int_greater_self_iff take_bit_int_eq_self_iff
     dest: sym not_sym intro: less_trans [of k 0 \<open>2 ^ n\<close>])
 
+(* FIXME: why is this here? *)
 context semiring_bit_operations
 begin
 
 lemma push_bit_of_nat:
   \<open>push_bit n (of_nat m) = of_nat (push_bit n m)\<close>
   by (simp add: push_bit_eq_mult Bit_Operations.push_bit_eq_mult)
 
 lemma of_nat_push_bit:
   \<open>of_nat (push_bit m n) = push_bit m (of_nat n)\<close>
   by (simp add: push_bit_eq_mult Bit_Operations.push_bit_eq_mult)
 
 lemma take_bit_of_nat:
   \<open>take_bit n (of_nat m) = of_nat (take_bit n m)\<close>
   by (rule bit_eqI) (simp add: bit_take_bit_iff Bit_Operations.bit_take_bit_iff bit_of_nat_iff)
 
 lemma of_nat_take_bit:
   \<open>of_nat (take_bit n m) = take_bit n (of_nat m)\<close>
   by (rule bit_eqI) (simp add: bit_take_bit_iff Bit_Operations.bit_take_bit_iff bit_of_nat_iff)
 
 end
 
 lemma push_bit_nat_eq:
   \<open>push_bit n (nat k) = nat (push_bit n k)\<close>
   by (cases \<open>k \<ge> 0\<close>) (simp_all add: push_bit_eq_mult nat_mult_distrib not_le mult_nonneg_nonpos2)
 
 lemma drop_bit_nat_eq:
   \<open>drop_bit n (nat k) = nat (drop_bit n k)\<close>
   apply (cases \<open>k \<ge> 0\<close>)
    apply (simp_all add: drop_bit_eq_div nat_div_distrib nat_power_eq not_le)
   apply (simp add: divide_int_def)
   done
 
 lemma take_bit_nat_eq:
   \<open>take_bit n (nat k) = nat (take_bit n k)\<close> if \<open>k \<ge> 0\<close>
   using that by (simp add: take_bit_eq_mod nat_mod_distrib nat_power_eq)
 
 lemma nat_take_bit_eq:
   \<open>nat (take_bit n k) = take_bit n (nat k)\<close>
   if \<open>k \<ge> 0\<close>
   using that by (simp add: take_bit_eq_mod nat_mod_distrib nat_power_eq)
 
 lemma not_exp_less_eq_0_int [simp]:
   \<open>\<not> 2 ^ n \<le> (0::int)\<close>
   by (simp add: power_le_zero_eq)
 
 lemma half_nonnegative_int_iff [simp]:
   \<open>k div 2 \<ge> 0 \<longleftrightarrow> k \<ge> 0\<close> for k :: int
 proof (cases \<open>k \<ge> 0\<close>)
   case True
   then show ?thesis
     by (auto simp add: divide_int_def sgn_1_pos)
 next
   case False
   then show ?thesis
     by (auto simp add: divide_int_def not_le elim!: evenE)
 qed
 
 lemma half_negative_int_iff [simp]:
   \<open>k div 2 < 0 \<longleftrightarrow> k < 0\<close> for k :: int
   by (subst Not_eq_iff [symmetric]) (simp add: not_less)
 
 lemma push_bit_of_Suc_0 [simp]:
   "push_bit n (Suc 0) = 2 ^ n"
   using push_bit_of_1 [where ?'a = nat] by simp
 
 lemma take_bit_of_Suc_0 [simp]:
   "take_bit n (Suc 0) = of_bool (0 < n)"
   using take_bit_of_1 [where ?'a = nat] by simp
 
 lemma drop_bit_of_Suc_0 [simp]:
   "drop_bit n (Suc 0) = of_bool (n = 0)"
   using drop_bit_of_1 [where ?'a = nat] by simp
 
 lemma int_bit_bound:
   fixes k :: int
   obtains n where \<open>\<And>m. n \<le> m \<Longrightarrow> bit k m \<longleftrightarrow> bit k n\<close>
     and \<open>n > 0 \<Longrightarrow> bit k (n - 1) \<noteq> bit k n\<close>
 proof -
   obtain q where *: \<open>\<And>m. q \<le> m \<Longrightarrow> bit k m \<longleftrightarrow> bit k q\<close>
   proof (cases \<open>k \<ge> 0\<close>)
     case True
     moreover from power_gt_expt [of 2 \<open>nat k\<close>]
     have \<open>nat k < 2 ^ nat k\<close>
       by simp
     then have \<open>int (nat k) < int (2 ^ nat k)\<close>
       by (simp only: of_nat_less_iff)
     ultimately have *: \<open>k div 2 ^ nat k = 0\<close>
       by simp
     show thesis
     proof (rule that [of \<open>nat k\<close>])
       fix m
       assume \<open>nat k \<le> m\<close>
       then show \<open>bit k m \<longleftrightarrow> bit k (nat k)\<close>
         by (auto simp add: * bit_iff_odd power_add zdiv_zmult2_eq dest!: le_Suc_ex)
     qed
   next
     case False
     moreover from power_gt_expt [of 2 \<open>nat (- k)\<close>]
     have \<open>nat (- k) < 2 ^ nat (- k)\<close>
       by simp
     then have \<open>int (nat (- k)) < int (2 ^ nat (- k))\<close>
       by (simp only: of_nat_less_iff)
     ultimately have \<open>- k div - (2 ^ nat (- k)) = - 1\<close>
       by (subst div_pos_neg_trivial) simp_all
     then have *: \<open>k div 2 ^ nat (- k) = - 1\<close>
       by simp
     show thesis
     proof (rule that [of \<open>nat (- k)\<close>])
       fix m
       assume \<open>nat (- k) \<le> m\<close>
       then show \<open>bit k m \<longleftrightarrow> bit k (nat (- k))\<close>
         by (auto simp add: * bit_iff_odd power_add zdiv_zmult2_eq minus_1_div_exp_eq_int dest!: le_Suc_ex)
     qed
   qed
   show thesis
   proof (cases \<open>\<forall>m. bit k m \<longleftrightarrow> bit k q\<close>)
     case True
     then have \<open>bit k 0 \<longleftrightarrow> bit k q\<close>
       by blast
     with True that [of 0] show thesis
       by simp
   next
     case False
     then obtain r where **: \<open>bit k r \<noteq> bit k q\<close>
       by blast
     have \<open>r < q\<close>
       by (rule ccontr) (use * [of r] ** in simp)
     define N where \<open>N = {n. n < q \<and> bit k n \<noteq> bit k q}\<close>
     moreover have \<open>finite N\<close> \<open>r \<in> N\<close>
       using ** N_def \<open>r < q\<close> by auto
     moreover define n where \<open>n = Suc (Max N)\<close>
     ultimately have \<open>\<And>m. n \<le> m \<Longrightarrow> bit k m \<longleftrightarrow> bit k n\<close>
       apply auto
          apply (metis (full_types, lifting) "*" Max_ge_iff Suc_n_not_le_n \<open>finite N\<close> all_not_in_conv mem_Collect_eq not_le)
         apply (metis "*" Max_ge Suc_n_not_le_n \<open>finite N\<close> linorder_not_less mem_Collect_eq)
         apply (metis "*" Max_ge Suc_n_not_le_n \<open>finite N\<close> linorder_not_less mem_Collect_eq)
       apply (metis (full_types, lifting) "*" Max_ge_iff Suc_n_not_le_n \<open>finite N\<close> all_not_in_conv mem_Collect_eq not_le)
       done
     have \<open>bit k (Max N) \<noteq> bit k n\<close>
       by (metis (mono_tags, lifting) "*" Max_in N_def \<open>\<And>m. n \<le> m \<Longrightarrow> bit k m = bit k n\<close> \<open>finite N\<close> \<open>r \<in> N\<close> empty_iff le_cases mem_Collect_eq)
     show thesis apply (rule that [of n])
       using \<open>\<And>m. n \<le> m \<Longrightarrow> bit k m = bit k n\<close> apply blast
       using \<open>bit k (Max N) \<noteq> bit k n\<close> n_def by auto
   qed
 qed
 
 context semiring_bit_operations
 begin
 
 lemma of_nat_and_eq:
   \<open>of_nat (m AND n) = of_nat m AND of_nat n\<close>
   by (rule bit_eqI) (simp add: bit_of_nat_iff bit_and_iff Bit_Operations.bit_and_iff)
 
 lemma of_nat_or_eq:
   \<open>of_nat (m OR n) = of_nat m OR of_nat n\<close>
   by (rule bit_eqI) (simp add: bit_of_nat_iff bit_or_iff Bit_Operations.bit_or_iff)
 
 lemma of_nat_xor_eq:
   \<open>of_nat (m XOR n) = of_nat m XOR of_nat n\<close>
   by (rule bit_eqI) (simp add: bit_of_nat_iff bit_xor_iff Bit_Operations.bit_xor_iff)
 
 end
 
 context ring_bit_operations
 begin
 
 lemma of_nat_mask_eq:
   \<open>of_nat (mask n) = mask n\<close>
   by (induction n) (simp_all add: mask_Suc_double Bit_Operations.mask_Suc_double of_nat_or_eq)
 
 end
 
 lemma Suc_mask_eq_exp:
   \<open>Suc (mask n) = 2 ^ n\<close>
   by (simp add: mask_eq_exp_minus_1)
 
 lemma less_eq_mask:
   \<open>n \<le> mask n\<close>
   by (simp add: mask_eq_exp_minus_1 le_diff_conv2)
     (metis Suc_mask_eq_exp diff_Suc_1 diff_le_diff_pow diff_zero le_refl not_less_eq_eq power_0)
 
 lemma less_mask:
   \<open>n < mask n\<close> if \<open>Suc 0 < n\<close>
 proof -
   define m where \<open>m = n - 2\<close>
   with that have *: \<open>n = m + 2\<close>
     by simp
   have \<open>Suc (Suc (Suc m)) < 4 * 2 ^ m\<close>
     by (induction m) simp_all
   then have \<open>Suc (m + 2) < Suc (mask (m + 2))\<close>
     by (simp add: Suc_mask_eq_exp)
   then have \<open>m + 2 < mask (m + 2)\<close>
     by (simp add: less_le)
   with * show ?thesis
     by simp
 qed
 
 
 subsection \<open>Bit concatenation\<close>
 
 definition concat_bit :: \<open>nat \<Rightarrow> int \<Rightarrow> int \<Rightarrow> int\<close>
   where \<open>concat_bit n k l = take_bit n k OR push_bit n l\<close>
 
 lemma bit_concat_bit_iff [bit_simps]:
   \<open>bit (concat_bit m k l) n \<longleftrightarrow> n < m \<and> bit k n \<or> m \<le> n \<and> bit l (n - m)\<close>
   by (simp add: concat_bit_def bit_or_iff bit_and_iff bit_take_bit_iff bit_push_bit_iff ac_simps)
 
 lemma concat_bit_eq:
   \<open>concat_bit n k l = take_bit n k + push_bit n l\<close>
   by (simp add: concat_bit_def take_bit_eq_mask
     bit_and_iff bit_mask_iff bit_push_bit_iff disjunctive_add)
 
 lemma concat_bit_0 [simp]:
   \<open>concat_bit 0 k l = l\<close>
   by (simp add: concat_bit_def)
 
 lemma concat_bit_Suc:
   \<open>concat_bit (Suc n) k l = k mod 2 + 2 * concat_bit n (k div 2) l\<close>
   by (simp add: concat_bit_eq take_bit_Suc push_bit_double)
 
 lemma concat_bit_of_zero_1 [simp]:
   \<open>concat_bit n 0 l = push_bit n l\<close>
   by (simp add: concat_bit_def)
 
 lemma concat_bit_of_zero_2 [simp]:
   \<open>concat_bit n k 0 = take_bit n k\<close>
   by (simp add: concat_bit_def take_bit_eq_mask)
 
 lemma concat_bit_nonnegative_iff [simp]:
   \<open>concat_bit n k l \<ge> 0 \<longleftrightarrow> l \<ge> 0\<close>
   by (simp add: concat_bit_def)
 
 lemma concat_bit_negative_iff [simp]:
   \<open>concat_bit n k l < 0 \<longleftrightarrow> l < 0\<close>
   by (simp add: concat_bit_def)
 
 lemma concat_bit_assoc:
   \<open>concat_bit n k (concat_bit m l r) = concat_bit (m + n) (concat_bit n k l) r\<close>
   by (rule bit_eqI) (auto simp add: bit_concat_bit_iff ac_simps)
 
 lemma concat_bit_assoc_sym:
   \<open>concat_bit m (concat_bit n k l) r = concat_bit (min m n) k (concat_bit (m - n) l r)\<close>
   by (rule bit_eqI) (auto simp add: bit_concat_bit_iff ac_simps min_def)
 
 lemma concat_bit_eq_iff:
   \<open>concat_bit n k l = concat_bit n r s
     \<longleftrightarrow> take_bit n k = take_bit n r \<and> l = s\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof
   assume ?Q
   then show ?P
     by (simp add: concat_bit_def)
 next
   assume ?P
   then have *: \<open>bit (concat_bit n k l) m = bit (concat_bit n r s) m\<close> for m
     by (simp add: bit_eq_iff)
   have \<open>take_bit n k = take_bit n r\<close>
   proof (rule bit_eqI)
     fix m
     from * [of m]
     show \<open>bit (take_bit n k) m \<longleftrightarrow> bit (take_bit n r) m\<close>
       by (auto simp add: bit_take_bit_iff bit_concat_bit_iff)
   qed
   moreover have \<open>push_bit n l = push_bit n s\<close>
   proof (rule bit_eqI)
     fix m
     from * [of m]
     show \<open>bit (push_bit n l) m \<longleftrightarrow> bit (push_bit n s) m\<close>
       by (auto simp add: bit_push_bit_iff bit_concat_bit_iff)
   qed
   then have \<open>l = s\<close>
     by (simp add: push_bit_eq_mult)
   ultimately show ?Q
     by (simp add: concat_bit_def)
 qed
 
 lemma take_bit_concat_bit_eq:
   \<open>take_bit m (concat_bit n k l) = concat_bit (min m n) k (take_bit (m - n) l)\<close>
   by (rule bit_eqI)
     (auto simp add: bit_take_bit_iff bit_concat_bit_iff min_def)  
 
 lemma concat_bit_take_bit_eq:
   \<open>concat_bit n (take_bit n b) = concat_bit n b\<close>
   by (simp add: concat_bit_def [abs_def])
 
 
 subsection \<open>Taking bits with sign propagation\<close>
 
 context ring_bit_operations
 begin
 
 definition signed_take_bit :: \<open>nat \<Rightarrow> 'a \<Rightarrow> 'a\<close>
   where \<open>signed_take_bit n a = take_bit n a OR (of_bool (bit a n) * NOT (mask n))\<close>
 
 lemma signed_take_bit_eq_if_positive:
   \<open>signed_take_bit n a = take_bit n a\<close> if \<open>\<not> bit a n\<close>
   using that by (simp add: signed_take_bit_def)
 
 lemma signed_take_bit_eq_if_negative:
   \<open>signed_take_bit n a = take_bit n a OR NOT (mask n)\<close> if \<open>bit a n\<close>
   using that by (simp add: signed_take_bit_def)
 
 lemma even_signed_take_bit_iff:
   \<open>even (signed_take_bit m a) \<longleftrightarrow> even a\<close>
   by (auto simp add: signed_take_bit_def even_or_iff even_mask_iff bit_double_iff)
 
 lemma bit_signed_take_bit_iff [bit_simps]:
-  \<open>bit (signed_take_bit m a) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> bit a (min m n)\<close>
+  \<open>bit (signed_take_bit m a) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> bit a (min m n)\<close>
   by (simp add: signed_take_bit_def bit_take_bit_iff bit_or_iff bit_not_iff bit_mask_iff min_def not_le)
-    (use exp_eq_0_imp_not_bit in blast)
+    (blast dest: bit_imp_possible_bit)
 
 lemma signed_take_bit_0 [simp]:
   \<open>signed_take_bit 0 a = - (a mod 2)\<close>
   by (simp add: signed_take_bit_def odd_iff_mod_2_eq_one)
 
 lemma signed_take_bit_Suc:
   \<open>signed_take_bit (Suc n) a = a mod 2 + 2 * signed_take_bit n (a div 2)\<close>
-proof (rule bit_eqI)
-  fix m
-  assume *: \<open>2 ^ m \<noteq> 0\<close>
-  show \<open>bit (signed_take_bit (Suc n) a) m \<longleftrightarrow>
-    bit (a mod 2 + 2 * signed_take_bit n (a div 2)) m\<close>
-  proof (cases m)
-    case 0
-    then show ?thesis
-      by (simp add: even_signed_take_bit_iff)
-  next
-    case (Suc m)
-    with * have \<open>2 ^ m \<noteq> 0\<close>
-      by (metis mult_not_zero power_Suc)
-    with Suc show ?thesis
-      by (simp add: bit_signed_take_bit_iff mod2_eq_if bit_double_iff even_bit_succ_iff
-        ac_simps flip: bit_Suc)
-  qed
-qed
+  apply (simp add: bit_eq_iff bit_sum_mult_2_cases bit_simps bit_Suc[symmetric])
+  apply (simp add: possible_bit_less_imp flip: min_Suc_Suc)
+  done
 
 lemma signed_take_bit_of_0 [simp]:
   \<open>signed_take_bit n 0 = 0\<close>
   by (simp add: signed_take_bit_def)
 
 lemma signed_take_bit_of_minus_1 [simp]:
   \<open>signed_take_bit n (- 1) = - 1\<close>
-  by (simp add: signed_take_bit_def take_bit_minus_one_eq_mask mask_eq_exp_minus_1)
+  by (simp add: signed_take_bit_def take_bit_minus_one_eq_mask mask_eq_exp_minus_1 possible_bit_def)
 
 lemma signed_take_bit_Suc_1 [simp]:
   \<open>signed_take_bit (Suc n) 1 = 1\<close>
   by (simp add: signed_take_bit_Suc)
 
 lemma signed_take_bit_rec:
   \<open>signed_take_bit n a = (if n = 0 then - (a mod 2) else a mod 2 + 2 * signed_take_bit (n - 1) (a div 2))\<close>
   by (cases n) (simp_all add: signed_take_bit_Suc)
 
 lemma signed_take_bit_eq_iff_take_bit_eq:
   \<open>signed_take_bit n a = signed_take_bit n b \<longleftrightarrow> take_bit (Suc n) a = take_bit (Suc n) b\<close>
 proof -
   have \<open>bit (signed_take_bit n a) = bit (signed_take_bit n b) \<longleftrightarrow> bit (take_bit (Suc n) a) = bit (take_bit (Suc n) b)\<close>
     by (simp add: fun_eq_iff bit_signed_take_bit_iff bit_take_bit_iff not_le less_Suc_eq_le min_def)
-      (use exp_eq_0_imp_not_bit in fastforce)
+      (use bit_imp_possible_bit in fastforce)
   then show ?thesis
-    by (simp add: bit_eq_iff fun_eq_iff)
+    by (auto simp add: fun_eq_iff intro: bit_eqI)
 qed
 
 lemma signed_take_bit_signed_take_bit [simp]:
   \<open>signed_take_bit m (signed_take_bit n a) = signed_take_bit (min m n) a\<close>
-proof (rule bit_eqI)
-  fix q
-  show \<open>bit (signed_take_bit m (signed_take_bit n a)) q \<longleftrightarrow>
-    bit (signed_take_bit (min m n) a) q\<close>
-    by (simp add: bit_signed_take_bit_iff min_def bit_or_iff bit_not_iff bit_mask_iff bit_take_bit_iff)
-      (use le_Suc_ex exp_add_not_zero_imp in blast)
-qed
+  by (auto simp add: bit_eq_iff bit_simps ac_simps possible_bit_min)
 
 lemma signed_take_bit_take_bit:
   \<open>signed_take_bit m (take_bit n a) = (if n \<le> m then take_bit n else signed_take_bit m) a\<close>
   by (rule bit_eqI) (auto simp add: bit_signed_take_bit_iff min_def bit_take_bit_iff)
 
 lemma take_bit_signed_take_bit:
   \<open>take_bit m (signed_take_bit n a) = take_bit m a\<close> if \<open>m \<le> Suc n\<close>
   using that by (rule le_SucE; intro bit_eqI)
    (auto simp add: bit_take_bit_iff bit_signed_take_bit_iff min_def less_Suc_eq)
 
 end
 
 text \<open>Modulus centered around 0\<close>
 
 lemma signed_take_bit_eq_concat_bit:
   \<open>signed_take_bit n k = concat_bit n k (- of_bool (bit k n))\<close>
   by (simp add: concat_bit_def signed_take_bit_def push_bit_minus_one_eq_not_mask)
 
 lemma signed_take_bit_add:
   \<open>signed_take_bit n (signed_take_bit n k + signed_take_bit n l) = signed_take_bit n (k + l)\<close>
   for k l :: int
 proof -
   have \<open>take_bit (Suc n)
      (take_bit (Suc n) (signed_take_bit n k) +
       take_bit (Suc n) (signed_take_bit n l)) =
     take_bit (Suc n) (k + l)\<close>
     by (simp add: take_bit_signed_take_bit take_bit_add)
   then show ?thesis
     by (simp only: signed_take_bit_eq_iff_take_bit_eq take_bit_add)
 qed
 
 lemma signed_take_bit_diff:
   \<open>signed_take_bit n (signed_take_bit n k - signed_take_bit n l) = signed_take_bit n (k - l)\<close>
   for k l :: int
 proof -
   have \<open>take_bit (Suc n)
      (take_bit (Suc n) (signed_take_bit n k) -
       take_bit (Suc n) (signed_take_bit n l)) =
     take_bit (Suc n) (k - l)\<close>
     by (simp add: take_bit_signed_take_bit take_bit_diff)
   then show ?thesis
     by (simp only: signed_take_bit_eq_iff_take_bit_eq take_bit_diff)
 qed
 
 lemma signed_take_bit_minus:
   \<open>signed_take_bit n (- signed_take_bit n k) = signed_take_bit n (- k)\<close>
   for k :: int
 proof -
   have \<open>take_bit (Suc n)
      (- take_bit (Suc n) (signed_take_bit n k)) =
     take_bit (Suc n) (- k)\<close>
     by (simp add: take_bit_signed_take_bit take_bit_minus)
   then show ?thesis
     by (simp only: signed_take_bit_eq_iff_take_bit_eq take_bit_minus)
 qed
 
 lemma signed_take_bit_mult:
   \<open>signed_take_bit n (signed_take_bit n k * signed_take_bit n l) = signed_take_bit n (k * l)\<close>
   for k l :: int
 proof -
   have \<open>take_bit (Suc n)
      (take_bit (Suc n) (signed_take_bit n k) *
       take_bit (Suc n) (signed_take_bit n l)) =
     take_bit (Suc n) (k * l)\<close>
     by (simp add: take_bit_signed_take_bit take_bit_mult)
   then show ?thesis
     by (simp only: signed_take_bit_eq_iff_take_bit_eq take_bit_mult)
 qed
 
 lemma signed_take_bit_eq_take_bit_minus:
   \<open>signed_take_bit n k = take_bit (Suc n) k - 2 ^ Suc n * of_bool (bit k n)\<close>
   for k :: int
 proof (cases \<open>bit k n\<close>)
   case True
   have \<open>signed_take_bit n k = take_bit (Suc n) k OR NOT (mask (Suc n))\<close>
     by (rule bit_eqI) (auto simp add: bit_signed_take_bit_iff min_def bit_take_bit_iff bit_or_iff bit_not_iff bit_mask_iff less_Suc_eq True)
   then have \<open>signed_take_bit n k = take_bit (Suc n) k + NOT (mask (Suc n))\<close>
     by (simp add: disjunctive_add bit_take_bit_iff bit_not_iff bit_mask_iff)
   with True show ?thesis
     by (simp flip: minus_exp_eq_not_mask)
 next
   case False
   show ?thesis
     by (rule bit_eqI) (simp add: False bit_signed_take_bit_iff bit_take_bit_iff min_def less_Suc_eq)
 qed
 
 lemma signed_take_bit_eq_take_bit_shift:
   \<open>signed_take_bit n k = take_bit (Suc n) (k + 2 ^ n) - 2 ^ n\<close>
   for k :: int
 proof -
   have *: \<open>take_bit n k OR 2 ^ n = take_bit n k + 2 ^ n\<close>
     by (simp add: disjunctive_add bit_exp_iff bit_take_bit_iff)
   have \<open>take_bit n k - 2 ^ n = take_bit n k + NOT (mask n)\<close>
     by (simp add: minus_exp_eq_not_mask)
   also have \<open>\<dots> = take_bit n k OR NOT (mask n)\<close>
     by (rule disjunctive_add)
       (simp add: bit_exp_iff bit_take_bit_iff bit_not_iff bit_mask_iff)
   finally have **: \<open>take_bit n k - 2 ^ n = take_bit n k OR NOT (mask n)\<close> .
   have \<open>take_bit (Suc n) (k + 2 ^ n) = take_bit (Suc n) (take_bit (Suc n) k + take_bit (Suc n) (2 ^ n))\<close>
     by (simp only: take_bit_add)
   also have \<open>take_bit (Suc n) k = 2 ^ n * of_bool (bit k n) + take_bit n k\<close>
     by (simp add: take_bit_Suc_from_most)
   finally have \<open>take_bit (Suc n) (k + 2 ^ n) = take_bit (Suc n) (2 ^ (n + of_bool (bit k n)) + take_bit n k)\<close>
     by (simp add: ac_simps)
   also have \<open>2 ^ (n + of_bool (bit k n)) + take_bit n k = 2 ^ (n + of_bool (bit k n)) OR take_bit n k\<close>
     by (rule disjunctive_add)
       (auto simp add: disjunctive_add bit_take_bit_iff bit_double_iff bit_exp_iff)
   finally show ?thesis
     using * ** by (simp add: signed_take_bit_def concat_bit_Suc min_def ac_simps)
 qed
 
 lemma signed_take_bit_nonnegative_iff [simp]:
   \<open>0 \<le> signed_take_bit n k \<longleftrightarrow> \<not> bit k n\<close>
   for k :: int
   by (simp add: signed_take_bit_def not_less concat_bit_def)
 
 lemma signed_take_bit_negative_iff [simp]:
   \<open>signed_take_bit n k < 0 \<longleftrightarrow> bit k n\<close>
   for k :: int
   by (simp add: signed_take_bit_def not_less concat_bit_def)
 
 lemma signed_take_bit_int_greater_eq_minus_exp [simp]:
   \<open>- (2 ^ n) \<le> signed_take_bit n k\<close>
   for k :: int
   by (simp add: signed_take_bit_eq_take_bit_shift)
 
 lemma signed_take_bit_int_less_exp [simp]:
   \<open>signed_take_bit n k < 2 ^ n\<close>
   for k :: int
   using take_bit_int_less_exp [of \<open>Suc n\<close>]
   by (simp add: signed_take_bit_eq_take_bit_shift)
 
 lemma signed_take_bit_int_eq_self_iff:
   \<open>signed_take_bit n k = k \<longleftrightarrow> - (2 ^ n) \<le> k \<and> k < 2 ^ n\<close>
   for k :: int
   by (auto simp add: signed_take_bit_eq_take_bit_shift take_bit_int_eq_self_iff algebra_simps)
 
 lemma signed_take_bit_int_eq_self:
   \<open>signed_take_bit n k = k\<close> if \<open>- (2 ^ n) \<le> k\<close> \<open>k < 2 ^ n\<close>
   for k :: int
   using that by (simp add: signed_take_bit_int_eq_self_iff)
 
 lemma signed_take_bit_int_less_eq_self_iff:
   \<open>signed_take_bit n k \<le> k \<longleftrightarrow> - (2 ^ n) \<le> k\<close>
   for k :: int
   by (simp add: signed_take_bit_eq_take_bit_shift take_bit_int_less_eq_self_iff algebra_simps)
     linarith
 
 lemma signed_take_bit_int_less_self_iff:
   \<open>signed_take_bit n k < k \<longleftrightarrow> 2 ^ n \<le> k\<close>
   for k :: int
   by (simp add: signed_take_bit_eq_take_bit_shift take_bit_int_less_self_iff algebra_simps)
 
 lemma signed_take_bit_int_greater_self_iff:
   \<open>k < signed_take_bit n k \<longleftrightarrow> k < - (2 ^ n)\<close>
   for k :: int
   by (simp add: signed_take_bit_eq_take_bit_shift take_bit_int_greater_self_iff algebra_simps)
     linarith
 
 lemma signed_take_bit_int_greater_eq_self_iff:
   \<open>k \<le> signed_take_bit n k \<longleftrightarrow> k < 2 ^ n\<close>
   for k :: int
   by (simp add: signed_take_bit_eq_take_bit_shift take_bit_int_greater_eq_self_iff algebra_simps)
 
 lemma signed_take_bit_int_greater_eq:
   \<open>k + 2 ^ Suc n \<le> signed_take_bit n k\<close> if \<open>k < - (2 ^ n)\<close>
   for k :: int
   using that take_bit_int_greater_eq [of \<open>k + 2 ^ n\<close> \<open>Suc n\<close>]
   by (simp add: signed_take_bit_eq_take_bit_shift)
 
 lemma signed_take_bit_int_less_eq:
   \<open>signed_take_bit n k \<le> k - 2 ^ Suc n\<close> if \<open>k \<ge> 2 ^ n\<close>
   for k :: int
   using that take_bit_int_less_eq [of \<open>Suc n\<close> \<open>k + 2 ^ n\<close>]
   by (simp add: signed_take_bit_eq_take_bit_shift)
 
 lemma signed_take_bit_Suc_bit0 [simp]:
   \<open>signed_take_bit (Suc n) (numeral (Num.Bit0 k)) = signed_take_bit n (numeral k) * (2 :: int)\<close>
   by (simp add: signed_take_bit_Suc)
 
 lemma signed_take_bit_Suc_bit1 [simp]:
   \<open>signed_take_bit (Suc n) (numeral (Num.Bit1 k)) = signed_take_bit n (numeral k) * 2 + (1 :: int)\<close>
   by (simp add: signed_take_bit_Suc)
 
 lemma signed_take_bit_Suc_minus_bit0 [simp]:
   \<open>signed_take_bit (Suc n) (- numeral (Num.Bit0 k)) = signed_take_bit n (- numeral k) * (2 :: int)\<close>
   by (simp add: signed_take_bit_Suc)
 
 lemma signed_take_bit_Suc_minus_bit1 [simp]:
   \<open>signed_take_bit (Suc n) (- numeral (Num.Bit1 k)) = signed_take_bit n (- numeral k - 1) * 2 + (1 :: int)\<close>
   by (simp add: signed_take_bit_Suc)
 
 lemma signed_take_bit_numeral_bit0 [simp]:
   \<open>signed_take_bit (numeral l) (numeral (Num.Bit0 k)) = signed_take_bit (pred_numeral l) (numeral k) * (2 :: int)\<close>
   by (simp add: signed_take_bit_rec)
 
 lemma signed_take_bit_numeral_bit1 [simp]:
   \<open>signed_take_bit (numeral l) (numeral (Num.Bit1 k)) = signed_take_bit (pred_numeral l) (numeral k) * 2 + (1 :: int)\<close>
   by (simp add: signed_take_bit_rec)
 
 lemma signed_take_bit_numeral_minus_bit0 [simp]:
   \<open>signed_take_bit (numeral l) (- numeral (Num.Bit0 k)) = signed_take_bit (pred_numeral l) (- numeral k) * (2 :: int)\<close>
   by (simp add: signed_take_bit_rec)
 
 lemma signed_take_bit_numeral_minus_bit1 [simp]:
   \<open>signed_take_bit (numeral l) (- numeral (Num.Bit1 k)) = signed_take_bit (pred_numeral l) (- numeral k - 1) * 2 + (1 :: int)\<close>
   by (simp add: signed_take_bit_rec)
 
 lemma signed_take_bit_code [code]:
   \<open>signed_take_bit n a =
   (let l = take_bit (Suc n) a
    in if bit l n then l + push_bit (Suc n) (- 1) else l)\<close>
 proof -
   have *: \<open>take_bit (Suc n) a + push_bit n (- 2) =
     take_bit (Suc n) a OR NOT (mask (Suc n))\<close>
     by (auto simp add: bit_take_bit_iff bit_push_bit_iff bit_not_iff bit_mask_iff disjunctive_add
        simp flip: push_bit_minus_one_eq_not_mask)
   show ?thesis
     by (rule bit_eqI)
       (auto simp add: Let_def * bit_signed_take_bit_iff bit_take_bit_iff min_def less_Suc_eq bit_not_iff bit_mask_iff bit_or_iff)
 qed
 
 
 subsection \<open>Horner sums\<close>
 
 context semiring_bit_operations
 begin
 
 lemma horner_sum_bit_eq_take_bit:
   \<open>horner_sum of_bool 2 (map (bit a) [0..<n]) = take_bit n a\<close>
 proof (induction a arbitrary: n rule: bits_induct)
   case (stable a)
   moreover have \<open>bit a = (\<lambda>_. odd a)\<close>
     using stable by (simp add: stable_imp_bit_iff_odd fun_eq_iff)
   moreover have \<open>{q. q < n} = {0..<n}\<close>
     by auto
   ultimately show ?case
     by (simp add: stable_imp_take_bit_eq horner_sum_eq_sum mask_eq_sum_exp)
 next
   case (rec a b)
   show ?case
   proof (cases n)
     case 0
     then show ?thesis
       by simp
   next
     case (Suc m)
     have \<open>map (bit (of_bool b + 2 * a)) [0..<Suc m] = b # map (bit (of_bool b + 2 * a)) [Suc 0..<Suc m]\<close>
       by (simp only: upt_conv_Cons) simp
     also have \<open>\<dots> = b # map (bit a) [0..<m]\<close>
       by (simp only: flip: map_Suc_upt) (simp add: bit_Suc rec.hyps)
     finally show ?thesis
       using Suc rec.IH [of m] by (simp add: take_bit_Suc rec.hyps)
         (simp_all add: ac_simps mod_2_eq_odd)
   qed
 qed
 
 end
 
 context unique_euclidean_semiring_with_bit_operations
 begin
 
 lemma bit_horner_sum_bit_iff [bit_simps]:
   \<open>bit (horner_sum of_bool 2 bs) n \<longleftrightarrow> n < length bs \<and> bs ! n\<close>
 proof (induction bs arbitrary: n)
   case Nil
   then show ?case
     by simp
 next
   case (Cons b bs)
   show ?case
   proof (cases n)
     case 0
     then show ?thesis
       by simp
   next
     case (Suc m)
     with bit_rec [of _ n] Cons.prems Cons.IH [of m]
     show ?thesis by simp
   qed
 qed
 
 lemma take_bit_horner_sum_bit_eq:
   \<open>take_bit n (horner_sum of_bool 2 bs) = horner_sum of_bool 2 (take n bs)\<close>
   by (auto simp add: bit_eq_iff bit_take_bit_iff bit_horner_sum_bit_iff)
 
 end
 
 lemma horner_sum_of_bool_2_less:
   \<open>(horner_sum of_bool 2 bs :: int) < 2 ^ length bs\<close>
 proof -
   have \<open>(\<Sum>n = 0..<length bs. of_bool (bs ! n) * (2::int) ^ n) \<le> (\<Sum>n = 0..<length bs. 2 ^ n)\<close>
     by (rule sum_mono) simp
   also have \<open>\<dots> = 2 ^ length bs - 1\<close>
     by (induction bs) simp_all
   finally show ?thesis
     by (simp add: horner_sum_eq_sum)
 qed
 
 
 subsection \<open>Key ideas of bit operations\<close>
 
 text \<open>
   When formalizing bit operations, it is tempting to represent
   bit values as explicit lists over a binary type. This however
   is a bad idea, mainly due to the inherent ambiguities in
   representation concerning repeating leading bits.
 
   Hence this approach avoids such explicit lists altogether
   following an algebraic path:
 
   \<^item> Bit values are represented by numeric types: idealized
     unbounded bit values can be represented by type \<^typ>\<open>int\<close>,
     bounded bit values by quotient types over \<^typ>\<open>int\<close>.
 
   \<^item> (A special case are idealized unbounded bit values ending
     in @{term [source] 0} which can be represented by type \<^typ>\<open>nat\<close> but
     only support a restricted set of operations).
 
   \<^item> From this idea follows that
 
       \<^item> multiplication by \<^term>\<open>2 :: int\<close> is a bit shift to the left and
 
       \<^item> division by \<^term>\<open>2 :: int\<close> is a bit shift to the right.
 
   \<^item> Concerning bounded bit values, iterated shifts to the left
     may result in eliminating all bits by shifting them all
     beyond the boundary.  The property \<^prop>\<open>(2 :: int) ^ n \<noteq> 0\<close>
     represents that \<^term>\<open>n\<close> is \<^emph>\<open>not\<close> beyond that boundary.
 
   \<^item> The projection on a single bit is then @{thm bit_iff_odd [where ?'a = int, no_vars]}.
 
   \<^item> This leads to the most fundamental properties of bit values:
 
       \<^item> Equality rule: @{thm bit_eqI [where ?'a = int, no_vars]}
 
       \<^item> Induction rule: @{thm bits_induct [where ?'a = int, no_vars]}
 
   \<^item> Typical operations are characterized as follows:
 
       \<^item> Singleton \<^term>\<open>n\<close>th bit: \<^term>\<open>(2 :: int) ^ n\<close>
 
       \<^item> Bit mask upto bit \<^term>\<open>n\<close>: @{thm mask_eq_exp_minus_1 [where ?'a = int, no_vars]}
 
       \<^item> Left shift: @{thm push_bit_eq_mult [where ?'a = int, no_vars]}
 
       \<^item> Right shift: @{thm drop_bit_eq_div [where ?'a = int, no_vars]}
 
       \<^item> Truncation: @{thm take_bit_eq_mod [where ?'a = int, no_vars]}
 
       \<^item> Negation: @{thm bit_not_iff [where ?'a = int, no_vars]}
 
       \<^item> And: @{thm bit_and_iff [where ?'a = int, no_vars]}
 
       \<^item> Or: @{thm bit_or_iff [where ?'a = int, no_vars]}
 
       \<^item> Xor: @{thm bit_xor_iff [where ?'a = int, no_vars]}
 
       \<^item> Set a single bit: @{thm set_bit_def [where ?'a = int, no_vars]}
 
       \<^item> Unset a single bit: @{thm unset_bit_def [where ?'a = int, no_vars]}
 
       \<^item> Flip a single bit: @{thm flip_bit_def [where ?'a = int, no_vars]}
 
       \<^item> Signed truncation, or modulus centered around \<^term>\<open>0::int\<close>: @{thm signed_take_bit_def [no_vars]}
 
       \<^item> Bit concatenation: @{thm concat_bit_def [no_vars]}
 
       \<^item> (Bounded) conversion from and to a list of bits: @{thm horner_sum_bit_eq_take_bit [where ?'a = int, no_vars]}
 \<close>
 
 no_notation
   "and"  (infixr \<open>AND\<close> 64)
     and or  (infixr \<open>OR\<close>  59)
     and xor  (infixr \<open>XOR\<close> 59)
 
 bundle bit_operations_syntax
 begin
 
 notation
   "and"  (infixr \<open>AND\<close> 64)
     and or  (infixr \<open>OR\<close>  59)
     and xor  (infixr \<open>XOR\<close> 59)
 
 end
 
 end
diff --git a/src/HOL/Code_Numeral.thy b/src/HOL/Code_Numeral.thy
--- a/src/HOL/Code_Numeral.thy
+++ b/src/HOL/Code_Numeral.thy
@@ -1,1329 +1,1329 @@
 (*  Title:      HOL/Code_Numeral.thy
     Author:     Florian Haftmann, TU Muenchen
 *)
 
 section \<open>Numeric types for code generation onto target language numerals only\<close>
 
 theory Code_Numeral
 imports Divides Lifting Bit_Operations
 begin
 
 subsection \<open>Type of target language integers\<close>
 
 typedef integer = "UNIV :: int set"
   morphisms int_of_integer integer_of_int ..
 
 setup_lifting type_definition_integer
 
 lemma integer_eq_iff:
   "k = l \<longleftrightarrow> int_of_integer k = int_of_integer l"
   by transfer rule
 
 lemma integer_eqI:
   "int_of_integer k = int_of_integer l \<Longrightarrow> k = l"
   using integer_eq_iff [of k l] by simp
 
 lemma int_of_integer_integer_of_int [simp]:
   "int_of_integer (integer_of_int k) = k"
   by transfer rule
 
 lemma integer_of_int_int_of_integer [simp]:
   "integer_of_int (int_of_integer k) = k"
   by transfer rule
 
 instantiation integer :: ring_1
 begin
 
 lift_definition zero_integer :: integer
   is "0 :: int"
   .
 
 declare zero_integer.rep_eq [simp]
 
 lift_definition one_integer :: integer
   is "1 :: int"
   .
 
 declare one_integer.rep_eq [simp]
 
 lift_definition plus_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer"
   is "plus :: int \<Rightarrow> int \<Rightarrow> int"
   .
 
 declare plus_integer.rep_eq [simp]
 
 lift_definition uminus_integer :: "integer \<Rightarrow> integer"
   is "uminus :: int \<Rightarrow> int"
   .
 
 declare uminus_integer.rep_eq [simp]
 
 lift_definition minus_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer"
   is "minus :: int \<Rightarrow> int \<Rightarrow> int"
   .
 
 declare minus_integer.rep_eq [simp]
 
 lift_definition times_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer"
   is "times :: int \<Rightarrow> int \<Rightarrow> int"
   .
 
 declare times_integer.rep_eq [simp]
 
 instance proof
 qed (transfer, simp add: algebra_simps)+
 
 end
 
 instance integer :: Rings.dvd ..
 
 context
   includes lifting_syntax
   notes transfer_rule_numeral [transfer_rule]
 begin
 
 lemma [transfer_rule]:
   "(pcr_integer ===> pcr_integer ===> (\<longleftrightarrow>)) (dvd) (dvd)"
   by (unfold dvd_def) transfer_prover
 
 lemma [transfer_rule]:
   "((\<longleftrightarrow>) ===> pcr_integer) of_bool of_bool"
   by (unfold of_bool_def) transfer_prover
 
 lemma [transfer_rule]:
   "((=) ===> pcr_integer) int of_nat"
   by (rule transfer_rule_of_nat) transfer_prover+
 
 lemma [transfer_rule]:
   "((=) ===> pcr_integer) (\<lambda>k. k) of_int"
 proof -
   have "((=) ===> pcr_integer) of_int of_int"
     by (rule transfer_rule_of_int) transfer_prover+
   then show ?thesis by (simp add: id_def)
 qed
 
 lemma [transfer_rule]:
   "((=) ===> pcr_integer) numeral numeral"
   by transfer_prover
 
 lemma [transfer_rule]:
   "((=) ===> (=) ===> pcr_integer) Num.sub Num.sub"
   by (unfold Num.sub_def) transfer_prover
 
 lemma [transfer_rule]:
   "(pcr_integer ===> (=) ===> pcr_integer) (^) (^)"
   by (unfold power_def) transfer_prover
 
 end
 
 lemma int_of_integer_of_nat [simp]:
   "int_of_integer (of_nat n) = of_nat n"
   by transfer rule
 
 lift_definition integer_of_nat :: "nat \<Rightarrow> integer"
   is "of_nat :: nat \<Rightarrow> int"
   .
 
 lemma integer_of_nat_eq_of_nat [code]:
   "integer_of_nat = of_nat"
   by transfer rule
 
 lemma int_of_integer_integer_of_nat [simp]:
   "int_of_integer (integer_of_nat n) = of_nat n"
   by transfer rule
 
 lift_definition nat_of_integer :: "integer \<Rightarrow> nat"
   is Int.nat
   .
 
 lemma nat_of_integer_of_nat [simp]:
   "nat_of_integer (of_nat n) = n"
   by transfer simp
 
 lemma int_of_integer_of_int [simp]:
   "int_of_integer (of_int k) = k"
   by transfer simp
 
 lemma nat_of_integer_integer_of_nat [simp]:
   "nat_of_integer (integer_of_nat n) = n"
   by transfer simp
 
 lemma integer_of_int_eq_of_int [simp, code_abbrev]:
   "integer_of_int = of_int"
   by transfer (simp add: fun_eq_iff)
 
 lemma of_int_integer_of [simp]:
   "of_int (int_of_integer k) = (k :: integer)"
   by transfer rule
 
 lemma int_of_integer_numeral [simp]:
   "int_of_integer (numeral k) = numeral k"
   by transfer rule
 
 lemma int_of_integer_sub [simp]:
   "int_of_integer (Num.sub k l) = Num.sub k l"
   by transfer rule
 
 definition integer_of_num :: "num \<Rightarrow> integer"
   where [simp]: "integer_of_num = numeral"
 
 lemma integer_of_num [code]:
   "integer_of_num Num.One = 1"
   "integer_of_num (Num.Bit0 n) = (let k = integer_of_num n in k + k)"
   "integer_of_num (Num.Bit1 n) = (let k = integer_of_num n in k + k + 1)"
   by (simp_all only: integer_of_num_def numeral.simps Let_def)
 
 lemma integer_of_num_triv:
   "integer_of_num Num.One = 1"
   "integer_of_num (Num.Bit0 Num.One) = 2"
   by simp_all
 
 instantiation integer :: "{linordered_idom, equal}"
 begin
 
 lift_definition abs_integer :: "integer \<Rightarrow> integer"
   is "abs :: int \<Rightarrow> int"
   .
 
 declare abs_integer.rep_eq [simp]
 
 lift_definition sgn_integer :: "integer \<Rightarrow> integer"
   is "sgn :: int \<Rightarrow> int"
   .
 
 declare sgn_integer.rep_eq [simp]
 
 lift_definition less_eq_integer :: "integer \<Rightarrow> integer \<Rightarrow> bool"
   is "less_eq :: int \<Rightarrow> int \<Rightarrow> bool"
   .
 
 lemma integer_less_eq_iff:
   "k \<le> l \<longleftrightarrow> int_of_integer k \<le> int_of_integer l"
   by (fact less_eq_integer.rep_eq)
 
 lift_definition less_integer :: "integer \<Rightarrow> integer \<Rightarrow> bool"
   is "less :: int \<Rightarrow> int \<Rightarrow> bool"
   .
 
 lemma integer_less_iff:
   "k < l \<longleftrightarrow> int_of_integer k < int_of_integer l"
   by (fact less_integer.rep_eq)
 
 lift_definition equal_integer :: "integer \<Rightarrow> integer \<Rightarrow> bool"
   is "HOL.equal :: int \<Rightarrow> int \<Rightarrow> bool"
   .
 
 instance
   by standard (transfer, simp add: algebra_simps equal less_le_not_le [symmetric] mult_strict_right_mono linear)+
 
 end
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>(pcr_integer ===> pcr_integer ===> pcr_integer) min min\<close>
   by (unfold min_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>(pcr_integer ===> pcr_integer ===> pcr_integer) max max\<close>
   by (unfold max_def) transfer_prover
 
 end
 
 lemma int_of_integer_min [simp]:
   "int_of_integer (min k l) = min (int_of_integer k) (int_of_integer l)"
   by transfer rule
 
 lemma int_of_integer_max [simp]:
   "int_of_integer (max k l) = max (int_of_integer k) (int_of_integer l)"
   by transfer rule
 
 lemma nat_of_integer_non_positive [simp]:
   "k \<le> 0 \<Longrightarrow> nat_of_integer k = 0"
   by transfer simp
 
 lemma of_nat_of_integer [simp]:
   "of_nat (nat_of_integer k) = max 0 k"
   by transfer auto
 
 instantiation integer :: unique_euclidean_ring
 begin
 
 lift_definition divide_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer"
   is "divide :: int \<Rightarrow> int \<Rightarrow> int"
   .
 
 declare divide_integer.rep_eq [simp]
 
 lift_definition modulo_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer"
   is "modulo :: int \<Rightarrow> int \<Rightarrow> int"
   .
 
 declare modulo_integer.rep_eq [simp]
 
 lift_definition euclidean_size_integer :: "integer \<Rightarrow> nat"
   is "euclidean_size :: int \<Rightarrow> nat"
   .
 
 declare euclidean_size_integer.rep_eq [simp]
 
 lift_definition division_segment_integer :: "integer \<Rightarrow> integer"
   is "division_segment :: int \<Rightarrow> int"
   .
 
 declare division_segment_integer.rep_eq [simp]
 
 instance
   by (standard; transfer)
     (use mult_le_mono2 [of 1] in \<open>auto simp add: sgn_mult_abs abs_mult sgn_mult abs_mod_less sgn_mod nat_mult_distrib
      division_segment_mult division_segment_mod intro: div_eqI\<close>)
 
 end
 
 lemma [code]:
   "euclidean_size = nat_of_integer \<circ> abs"
   by (simp add: fun_eq_iff nat_of_integer.rep_eq)
 
 lemma [code]:
   "division_segment (k :: integer) = (if k \<ge> 0 then 1 else - 1)"
   by transfer (simp add: division_segment_int_def)
 
 instance integer :: unique_euclidean_ring_with_nat
   by (standard; transfer) (simp_all add: of_nat_div division_segment_int_def)
 
 instantiation integer :: ring_bit_operations
 begin
 
 lift_definition bit_integer :: \<open>integer \<Rightarrow> nat \<Rightarrow> bool\<close>
   is bit .
 
 lift_definition not_integer :: \<open>integer \<Rightarrow> integer\<close>
   is not .
 
 lift_definition and_integer :: \<open>integer \<Rightarrow> integer \<Rightarrow> integer\<close>
   is \<open>and\<close> .
 
 lift_definition or_integer :: \<open>integer \<Rightarrow> integer \<Rightarrow> integer\<close>
   is or .
 
 lift_definition xor_integer ::  \<open>integer \<Rightarrow> integer \<Rightarrow> integer\<close>
   is xor .
 
 lift_definition mask_integer :: \<open>nat \<Rightarrow> integer\<close>
   is mask .
 
 lift_definition set_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is set_bit .
 
 lift_definition unset_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is unset_bit .
 
 lift_definition flip_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is flip_bit .
 
 lift_definition push_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is push_bit .
 
 lift_definition drop_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is drop_bit .
 
 lift_definition take_bit_integer :: \<open>nat \<Rightarrow> integer \<Rightarrow> integer\<close>
   is take_bit .
 
 instance by (standard; transfer)
   (fact bit_eq_rec bits_induct bit_iff_odd push_bit_eq_mult drop_bit_eq_div take_bit_eq_mod
     bits_div_0 bits_div_by_1 bits_mod_div_trivial even_succ_div_2
     exp_div_exp_eq div_exp_eq mod_exp_eq mult_exp_mod_exp_eq div_exp_mod_exp_eq
     even_mask_div_iff even_mult_exp_div_exp_iff
     bit_and_iff bit_or_iff bit_xor_iff mask_eq_exp_minus_1
-    set_bit_def bit_unset_bit_iff flip_bit_def bit_not_iff minus_eq_not_minus_1)+
+    set_bit_def bit_unset_bit_iff flip_bit_def bit_not_iff_eq minus_eq_not_minus_1)+
 
 end
 
 instance integer :: unique_euclidean_semiring_with_bit_operations ..
 
 context
   includes bit_operations_syntax
 begin
 
 lemma [code]:
   \<open>bit k n \<longleftrightarrow> odd (drop_bit n k)\<close>
   \<open>NOT k = - k - 1\<close>
   \<open>mask n = 2 ^ n - (1 :: integer)\<close>
   \<open>set_bit n k = k OR push_bit n 1\<close>
   \<open>unset_bit n k = k AND NOT (push_bit n 1)\<close>
   \<open>flip_bit n k = k XOR push_bit n 1\<close>
   \<open>push_bit n k = k * 2 ^ n\<close>
   \<open>drop_bit n k = k div 2 ^ n\<close>
   \<open>take_bit n k = k mod 2 ^ n\<close> for k :: integer
   by (fact bit_iff_odd_drop_bit not_eq_complement mask_eq_exp_minus_1
     set_bit_eq_or unset_bit_eq_and_not flip_bit_eq_xor push_bit_eq_mult drop_bit_eq_div take_bit_eq_mod)+
 
 lemma [code]:
   \<open>k AND l = (if k = 0 \<or> l = 0 then 0 else if k = - 1 then l else if l = - 1 then k
     else (k mod 2) * (l mod 2) + 2 * ((k div 2) AND (l div 2)))\<close> for k l :: integer
   by transfer (fact and_int_unfold) 
 
 lemma [code]:
   \<open>k OR l = (if k = - 1 \<or> l = - 1 then - 1 else if k = 0 then l else if l = 0 then k
     else max (k mod 2) (l mod 2) + 2 * ((k div 2) OR (l div 2)))\<close> for k l :: integer
   by transfer (fact or_int_unfold)
 
 lemma [code]:
   \<open>k XOR l = (if k = - 1 then NOT l else if l = - 1 then NOT k else if k = 0 then l else if l = 0 then k
     else \<bar>k mod 2 - l mod 2\<bar> + 2 * ((k div 2) XOR (l div 2)))\<close> for k l :: integer
   by transfer (fact xor_int_unfold)
 
 end
 
 instantiation integer :: unique_euclidean_semiring_numeral
 begin
 
 definition divmod_integer :: "num \<Rightarrow> num \<Rightarrow> integer \<times> integer"
 where
   divmod_integer'_def: "divmod_integer m n = (numeral m div numeral n, numeral m mod numeral n)"
 
 definition divmod_step_integer :: "num \<Rightarrow> integer \<times> integer \<Rightarrow> integer \<times> integer"
 where
   "divmod_step_integer l qr = (let (q, r) = qr
     in if r \<ge> numeral l then (2 * q + 1, r - numeral l)
     else (2 * q, r))"
 
 instance proof
   show "divmod m n = (numeral m div numeral n :: integer, numeral m mod numeral n)"
     for m n by (fact divmod_integer'_def)
   show "divmod_step l qr = (let (q, r) = qr
     in if r \<ge> numeral l then (2 * q + 1, r - numeral l)
     else (2 * q, r))" for l and qr :: "integer \<times> integer"
     by (fact divmod_step_integer_def)
 qed (transfer,
   fact le_add_diff_inverse2
   unique_euclidean_semiring_numeral_class.div_less
   unique_euclidean_semiring_numeral_class.mod_less
   unique_euclidean_semiring_numeral_class.div_positive
   unique_euclidean_semiring_numeral_class.mod_less_eq_dividend
   unique_euclidean_semiring_numeral_class.pos_mod_bound
   unique_euclidean_semiring_numeral_class.pos_mod_sign
   unique_euclidean_semiring_numeral_class.mod_mult2_eq
   unique_euclidean_semiring_numeral_class.div_mult2_eq
   unique_euclidean_semiring_numeral_class.discrete)+
 
 end
 
 declare divmod_algorithm_code [where ?'a = integer,
   folded integer_of_num_def, unfolded integer_of_num_triv,
   code]
 
 lemma integer_of_nat_0: "integer_of_nat 0 = 0"
 by transfer simp
 
 lemma integer_of_nat_1: "integer_of_nat 1 = 1"
 by transfer simp
 
 lemma integer_of_nat_numeral:
   "integer_of_nat (numeral n) = numeral n"
 by transfer simp
 
 
 subsection \<open>Code theorems for target language integers\<close>
 
 text \<open>Constructors\<close>
 
 definition Pos :: "num \<Rightarrow> integer"
 where
   [simp, code_post]: "Pos = numeral"
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_integer) numeral Pos\<close>
   by simp transfer_prover
 
 end
 
 lemma Pos_fold [code_unfold]:
   "numeral Num.One = Pos Num.One"
   "numeral (Num.Bit0 k) = Pos (Num.Bit0 k)"
   "numeral (Num.Bit1 k) = Pos (Num.Bit1 k)"
   by simp_all
 
 definition Neg :: "num \<Rightarrow> integer"
 where
   [simp, code_abbrev]: "Neg n = - Pos n"
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_integer) (\<lambda>n. - numeral n) Neg\<close>
   by (unfold Neg_def) transfer_prover
 
 end
 
 code_datatype "0::integer" Pos Neg
 
   
 text \<open>A further pair of constructors for generated computations\<close>
 
 context
 begin  
 
 qualified definition positive :: "num \<Rightarrow> integer"
   where [simp]: "positive = numeral"
 
 qualified definition negative :: "num \<Rightarrow> integer"
   where [simp]: "negative = uminus \<circ> numeral"
 
 lemma [code_computation_unfold]:
   "numeral = positive"
   "Pos = positive"
   "Neg = negative"
   by (simp_all add: fun_eq_iff)
 
 end
 
 
 text \<open>Auxiliary operations\<close>
 
 lift_definition dup :: "integer \<Rightarrow> integer"
   is "\<lambda>k::int. k + k"
   .
 
 lemma dup_code [code]:
   "dup 0 = 0"
   "dup (Pos n) = Pos (Num.Bit0 n)"
   "dup (Neg n) = Neg (Num.Bit0 n)"
   by (transfer, simp only: numeral_Bit0 minus_add_distrib)+
 
 lift_definition sub :: "num \<Rightarrow> num \<Rightarrow> integer"
   is "\<lambda>m n. numeral m - numeral n :: int"
   .
 
 lemma sub_code [code]:
   "sub Num.One Num.One = 0"
   "sub (Num.Bit0 m) Num.One = Pos (Num.BitM m)"
   "sub (Num.Bit1 m) Num.One = Pos (Num.Bit0 m)"
   "sub Num.One (Num.Bit0 n) = Neg (Num.BitM n)"
   "sub Num.One (Num.Bit1 n) = Neg (Num.Bit0 n)"
   "sub (Num.Bit0 m) (Num.Bit0 n) = dup (sub m n)"
   "sub (Num.Bit1 m) (Num.Bit1 n) = dup (sub m n)"
   "sub (Num.Bit1 m) (Num.Bit0 n) = dup (sub m n) + 1"
   "sub (Num.Bit0 m) (Num.Bit1 n) = dup (sub m n) - 1"
   by (transfer, simp add: dbl_def dbl_inc_def dbl_dec_def)+
 
 
 text \<open>Implementations\<close>
 
 lemma one_integer_code [code, code_unfold]:
   "1 = Pos Num.One"
   by simp
 
 lemma plus_integer_code [code]:
   "k + 0 = (k::integer)"
   "0 + l = (l::integer)"
   "Pos m + Pos n = Pos (m + n)"
   "Pos m + Neg n = sub m n"
   "Neg m + Pos n = sub n m"
   "Neg m + Neg n = Neg (m + n)"
   by (transfer, simp)+
 
 lemma uminus_integer_code [code]:
   "uminus 0 = (0::integer)"
   "uminus (Pos m) = Neg m"
   "uminus (Neg m) = Pos m"
   by simp_all
 
 lemma minus_integer_code [code]:
   "k - 0 = (k::integer)"
   "0 - l = uminus (l::integer)"
   "Pos m - Pos n = sub m n"
   "Pos m - Neg n = Pos (m + n)"
   "Neg m - Pos n = Neg (m + n)"
   "Neg m - Neg n = sub n m"
   by (transfer, simp)+
 
 lemma abs_integer_code [code]:
   "\<bar>k\<bar> = (if (k::integer) < 0 then - k else k)"
   by simp
 
 lemma sgn_integer_code [code]:
   "sgn k = (if k = 0 then 0 else if (k::integer) < 0 then - 1 else 1)"
   by simp
 
 lemma times_integer_code [code]:
   "k * 0 = (0::integer)"
   "0 * l = (0::integer)"
   "Pos m * Pos n = Pos (m * n)"
   "Pos m * Neg n = Neg (m * n)"
   "Neg m * Pos n = Neg (m * n)"
   "Neg m * Neg n = Pos (m * n)"
   by simp_all
 
 definition divmod_integer :: "integer \<Rightarrow> integer \<Rightarrow> integer \<times> integer"
 where
   "divmod_integer k l = (k div l, k mod l)"
 
 lemma fst_divmod_integer [simp]:
   "fst (divmod_integer k l) = k div l"
   by (simp add: divmod_integer_def)
 
 lemma snd_divmod_integer [simp]:
   "snd (divmod_integer k l) = k mod l"
   by (simp add: divmod_integer_def)
 
 definition divmod_abs :: "integer \<Rightarrow> integer \<Rightarrow> integer \<times> integer"
 where
   "divmod_abs k l = (\<bar>k\<bar> div \<bar>l\<bar>, \<bar>k\<bar> mod \<bar>l\<bar>)"
 
 lemma fst_divmod_abs [simp]:
   "fst (divmod_abs k l) = \<bar>k\<bar> div \<bar>l\<bar>"
   by (simp add: divmod_abs_def)
 
 lemma snd_divmod_abs [simp]:
   "snd (divmod_abs k l) = \<bar>k\<bar> mod \<bar>l\<bar>"
   by (simp add: divmod_abs_def)
 
 lemma divmod_abs_code [code]:
   "divmod_abs (Pos k) (Pos l) = divmod k l"
   "divmod_abs (Neg k) (Neg l) = divmod k l"
   "divmod_abs (Neg k) (Pos l) = divmod k l"
   "divmod_abs (Pos k) (Neg l) = divmod k l"
   "divmod_abs j 0 = (0, \<bar>j\<bar>)"
   "divmod_abs 0 j = (0, 0)"
   by (simp_all add: prod_eq_iff)
 
 lemma divmod_integer_eq_cases:
   "divmod_integer k l =
     (if k = 0 then (0, 0) else if l = 0 then (0, k) else
     (apsnd \<circ> times \<circ> sgn) l (if sgn k = sgn l
       then divmod_abs k l
       else (let (r, s) = divmod_abs k l in
         if s = 0 then (- r, 0) else (- r - 1, \<bar>l\<bar> - s))))"
 proof -
   have *: "sgn k = sgn l \<longleftrightarrow> k = 0 \<and> l = 0 \<or> 0 < l \<and> 0 < k \<or> l < 0 \<and> k < 0" for k l :: int
     by (auto simp add: sgn_if)
   have **: "- k = l * q \<longleftrightarrow> k = - (l * q)" for k l q :: int
     by auto
   show ?thesis
     by (simp add: divmod_integer_def divmod_abs_def)
       (transfer, auto simp add: * ** not_less zdiv_zminus1_eq_if zmod_zminus1_eq_if div_minus_right mod_minus_right)
 qed
 
 lemma divmod_integer_code [code]: \<^marker>\<open>contributor \<open>René Thiemann\<close>\<close> \<^marker>\<open>contributor \<open>Akihisa Yamada\<close>\<close>
   "divmod_integer k l =
    (if k = 0 then (0, 0)
     else if l > 0 then
             (if k > 0 then Code_Numeral.divmod_abs k l
              else case Code_Numeral.divmod_abs k l of (r, s) \<Rightarrow>
                   if s = 0 then (- r, 0) else (- r - 1, l - s))
     else if l = 0 then (0, k)
     else apsnd uminus
             (if k < 0 then Code_Numeral.divmod_abs k l
              else case Code_Numeral.divmod_abs k l of (r, s) \<Rightarrow>
                   if s = 0 then (- r, 0) else (- r - 1, - l - s)))"
   by (cases l "0 :: integer" rule: linorder_cases)
     (auto split: prod.splits simp add: divmod_integer_eq_cases)
 
 lemma div_integer_code [code]:
   "k div l = fst (divmod_integer k l)"
   by simp
 
 lemma mod_integer_code [code]:
   "k mod l = snd (divmod_integer k l)"
   by simp
 
 definition bit_cut_integer :: "integer \<Rightarrow> integer \<times> bool"
   where "bit_cut_integer k = (k div 2, odd k)"
 
 lemma bit_cut_integer_code [code]:
   "bit_cut_integer k = (if k = 0 then (0, False)
      else let (r, s) = Code_Numeral.divmod_abs k 2
        in (if k > 0 then r else - r - s, s = 1))"
 proof -
   have "bit_cut_integer k = (let (r, s) = divmod_integer k 2 in (r, s = 1))"
     by (simp add: divmod_integer_def bit_cut_integer_def odd_iff_mod_2_eq_one)
   then show ?thesis
     by (simp add: divmod_integer_code) (auto simp add: split_def)
 qed
 
 lemma equal_integer_code [code]:
   "HOL.equal 0 (0::integer) \<longleftrightarrow> True"
   "HOL.equal 0 (Pos l) \<longleftrightarrow> False"
   "HOL.equal 0 (Neg l) \<longleftrightarrow> False"
   "HOL.equal (Pos k) 0 \<longleftrightarrow> False"
   "HOL.equal (Pos k) (Pos l) \<longleftrightarrow> HOL.equal k l"
   "HOL.equal (Pos k) (Neg l) \<longleftrightarrow> False"
   "HOL.equal (Neg k) 0 \<longleftrightarrow> False"
   "HOL.equal (Neg k) (Pos l) \<longleftrightarrow> False"
   "HOL.equal (Neg k) (Neg l) \<longleftrightarrow> HOL.equal k l"
   by (simp_all add: equal)
 
 lemma equal_integer_refl [code nbe]:
   "HOL.equal (k::integer) k \<longleftrightarrow> True"
   by (fact equal_refl)
 
 lemma less_eq_integer_code [code]:
   "0 \<le> (0::integer) \<longleftrightarrow> True"
   "0 \<le> Pos l \<longleftrightarrow> True"
   "0 \<le> Neg l \<longleftrightarrow> False"
   "Pos k \<le> 0 \<longleftrightarrow> False"
   "Pos k \<le> Pos l \<longleftrightarrow> k \<le> l"
   "Pos k \<le> Neg l \<longleftrightarrow> False"
   "Neg k \<le> 0 \<longleftrightarrow> True"
   "Neg k \<le> Pos l \<longleftrightarrow> True"
   "Neg k \<le> Neg l \<longleftrightarrow> l \<le> k"
   by simp_all
 
 lemma less_integer_code [code]:
   "0 < (0::integer) \<longleftrightarrow> False"
   "0 < Pos l \<longleftrightarrow> True"
   "0 < Neg l \<longleftrightarrow> False"
   "Pos k < 0 \<longleftrightarrow> False"
   "Pos k < Pos l \<longleftrightarrow> k < l"
   "Pos k < Neg l \<longleftrightarrow> False"
   "Neg k < 0 \<longleftrightarrow> True"
   "Neg k < Pos l \<longleftrightarrow> True"
   "Neg k < Neg l \<longleftrightarrow> l < k"
   by simp_all
 
 lift_definition num_of_integer :: "integer \<Rightarrow> num"
   is "num_of_nat \<circ> nat"
   .
 
 lemma num_of_integer_code [code]:
   "num_of_integer k = (if k \<le> 1 then Num.One
      else let
        (l, j) = divmod_integer k 2;
        l' = num_of_integer l;
        l'' = l' + l'
      in if j = 0 then l'' else l'' + Num.One)"
 proof -
   {
     assume "int_of_integer k mod 2 = 1"
     then have "nat (int_of_integer k mod 2) = nat 1" by simp
     moreover assume *: "1 < int_of_integer k"
     ultimately have **: "nat (int_of_integer k) mod 2 = 1" by (simp add: nat_mod_distrib)
     have "num_of_nat (nat (int_of_integer k)) =
       num_of_nat (2 * (nat (int_of_integer k) div 2) + nat (int_of_integer k) mod 2)"
       by simp
     then have "num_of_nat (nat (int_of_integer k)) =
       num_of_nat (nat (int_of_integer k) div 2 + nat (int_of_integer k) div 2 + nat (int_of_integer k) mod 2)"
       by (simp add: mult_2)
     with ** have "num_of_nat (nat (int_of_integer k)) =
       num_of_nat (nat (int_of_integer k) div 2 + nat (int_of_integer k) div 2 + 1)"
       by simp
   }
   note aux = this
   show ?thesis
     by (auto simp add: num_of_integer_def nat_of_integer_def Let_def case_prod_beta
       not_le integer_eq_iff less_eq_integer_def
       nat_mult_distrib nat_div_distrib num_of_nat_One num_of_nat_plus_distrib
        mult_2 [where 'a=nat] aux add_One)
 qed
 
 lemma nat_of_integer_code [code]:
   "nat_of_integer k = (if k \<le> 0 then 0
      else let
        (l, j) = divmod_integer k 2;
        l' = nat_of_integer l;
        l'' = l' + l'
      in if j = 0 then l'' else l'' + 1)"
 proof -
   obtain j where k: "k = integer_of_int j"
   proof
     show "k = integer_of_int (int_of_integer k)" by simp
   qed
   have *: "nat j mod 2 = nat_of_integer (of_int j mod 2)" if "j \<ge> 0"
     using that by transfer (simp add: nat_mod_distrib)
   from k show ?thesis
     by (auto simp add: split_def Let_def nat_of_integer_def nat_div_distrib mult_2 [symmetric]
       minus_mod_eq_mult_div [symmetric] *)
 qed
 
 lemma int_of_integer_code [code]:
   "int_of_integer k = (if k < 0 then - (int_of_integer (- k))
      else if k = 0 then 0
      else let
        (l, j) = divmod_integer k 2;
        l' = 2 * int_of_integer l
      in if j = 0 then l' else l' + 1)"
   by (auto simp add: split_def Let_def integer_eq_iff minus_mod_eq_mult_div [symmetric])
 
 lemma integer_of_int_code [code]:
   "integer_of_int k = (if k < 0 then - (integer_of_int (- k))
      else if k = 0 then 0
      else let
        l = 2 * integer_of_int (k div 2);
        j = k mod 2
      in if j = 0 then l else l + 1)"
   by (auto simp add: split_def Let_def integer_eq_iff minus_mod_eq_mult_div [symmetric])
 
 hide_const (open) Pos Neg sub dup divmod_abs
 
 
 subsection \<open>Serializer setup for target language integers\<close>
 
 code_reserved Eval int Integer abs
 
 code_printing
   type_constructor integer \<rightharpoonup>
     (SML) "IntInf.int"
     and (OCaml) "Z.t"
     and (Haskell) "Integer"
     and (Scala) "BigInt"
     and (Eval) "int"
 | class_instance integer :: equal \<rightharpoonup>
     (Haskell) -
 
 code_printing
   constant "0::integer" \<rightharpoonup>
     (SML) "!(0/ :/ IntInf.int)"
     and (OCaml) "Z.zero"
     and (Haskell) "!(0/ ::/ Integer)"
     and (Scala) "BigInt(0)"
 
 setup \<open>
   fold (fn target =>
     Numeral.add_code \<^const_name>\<open>Code_Numeral.Pos\<close> I Code_Printer.literal_numeral target
     #> Numeral.add_code \<^const_name>\<open>Code_Numeral.Neg\<close> (~) Code_Printer.literal_numeral target)
     ["SML", "OCaml", "Haskell", "Scala"]
 \<close>
 
 code_printing
   constant "plus :: integer \<Rightarrow> _ \<Rightarrow> _" \<rightharpoonup>
     (SML) "IntInf.+ ((_), (_))"
     and (OCaml) "Z.add"
     and (Haskell) infixl 6 "+"
     and (Scala) infixl 7 "+"
     and (Eval) infixl 8 "+"
 | constant "uminus :: integer \<Rightarrow> _" \<rightharpoonup>
     (SML) "IntInf.~"
     and (OCaml) "Z.neg"
     and (Haskell) "negate"
     and (Scala) "!(- _)"
     and (Eval) "~/ _"
 | constant "minus :: integer \<Rightarrow> _" \<rightharpoonup>
     (SML) "IntInf.- ((_), (_))"
     and (OCaml) "Z.sub"
     and (Haskell) infixl 6 "-"
     and (Scala) infixl 7 "-"
     and (Eval) infixl 8 "-"
 | constant Code_Numeral.dup \<rightharpoonup>
     (SML) "IntInf.*/ (2,/ (_))"
     and (OCaml) "Z.shift'_left/ _/ 1"
     and (Haskell) "!(2 * _)"
     and (Scala) "!(2 * _)"
     and (Eval) "!(2 * _)"
 | constant Code_Numeral.sub \<rightharpoonup>
     (SML) "!(raise/ Fail/ \"sub\")"
     and (OCaml) "failwith/ \"sub\""
     and (Haskell) "error/ \"sub\""
     and (Scala) "!sys.error(\"sub\")"
 | constant "times :: integer \<Rightarrow> _ \<Rightarrow> _" \<rightharpoonup>
     (SML) "IntInf.* ((_), (_))"
     and (OCaml) "Z.mul"
     and (Haskell) infixl 7 "*"
     and (Scala) infixl 8 "*"
     and (Eval) infixl 9 "*"
 | constant Code_Numeral.divmod_abs \<rightharpoonup>
     (SML) "IntInf.divMod/ (IntInf.abs _,/ IntInf.abs _)"
     and (OCaml) "!(fun k l ->/ if Z.equal Z.zero l then/ (Z.zero, l) else/ Z.div'_rem/ (Z.abs k)/ (Z.abs l))"
     and (Haskell) "divMod/ (abs _)/ (abs _)"
     and (Scala) "!((k: BigInt) => (l: BigInt) =>/ if (l == 0)/ (BigInt(0), k) else/ (k.abs '/% l.abs))"
     and (Eval) "Integer.div'_mod/ (abs _)/ (abs _)"
 | constant "HOL.equal :: integer \<Rightarrow> _ \<Rightarrow> bool" \<rightharpoonup>
     (SML) "!((_ : IntInf.int) = _)"
     and (OCaml) "Z.equal"
     and (Haskell) infix 4 "=="
     and (Scala) infixl 5 "=="
     and (Eval) infixl 6 "="
 | constant "less_eq :: integer \<Rightarrow> _ \<Rightarrow> bool" \<rightharpoonup>
     (SML) "IntInf.<= ((_), (_))"
     and (OCaml) "Z.leq"
     and (Haskell) infix 4 "<="
     and (Scala) infixl 4 "<="
     and (Eval) infixl 6 "<="
 | constant "less :: integer \<Rightarrow> _ \<Rightarrow> bool" \<rightharpoonup>
     (SML) "IntInf.< ((_), (_))"
     and (OCaml) "Z.lt"
     and (Haskell) infix 4 "<"
     and (Scala) infixl 4 "<"
     and (Eval) infixl 6 "<"
 | constant "abs :: integer \<Rightarrow> _" \<rightharpoonup>
     (SML) "IntInf.abs"
     and (OCaml) "Z.abs"
     and (Haskell) "Prelude.abs"
     and (Scala) "_.abs"
     and (Eval) "abs"
 
 code_identifier
   code_module Code_Numeral \<rightharpoonup> (SML) Arith and (OCaml) Arith and (Haskell) Arith
 
 
 subsection \<open>Type of target language naturals\<close>
 
 typedef natural = "UNIV :: nat set"
   morphisms nat_of_natural natural_of_nat ..
 
 setup_lifting type_definition_natural
 
 lemma natural_eq_iff [termination_simp]:
   "m = n \<longleftrightarrow> nat_of_natural m = nat_of_natural n"
   by transfer rule
 
 lemma natural_eqI:
   "nat_of_natural m = nat_of_natural n \<Longrightarrow> m = n"
   using natural_eq_iff [of m n] by simp
 
 lemma nat_of_natural_of_nat_inverse [simp]:
   "nat_of_natural (natural_of_nat n) = n"
   by transfer rule
 
 lemma natural_of_nat_of_natural_inverse [simp]:
   "natural_of_nat (nat_of_natural n) = n"
   by transfer rule
 
 instantiation natural :: "{comm_monoid_diff, semiring_1}"
 begin
 
 lift_definition zero_natural :: natural
   is "0 :: nat"
   .
 
 declare zero_natural.rep_eq [simp]
 
 lift_definition one_natural :: natural
   is "1 :: nat"
   .
 
 declare one_natural.rep_eq [simp]
 
 lift_definition plus_natural :: "natural \<Rightarrow> natural \<Rightarrow> natural"
   is "plus :: nat \<Rightarrow> nat \<Rightarrow> nat"
   .
 
 declare plus_natural.rep_eq [simp]
 
 lift_definition minus_natural :: "natural \<Rightarrow> natural \<Rightarrow> natural"
   is "minus :: nat \<Rightarrow> nat \<Rightarrow> nat"
   .
 
 declare minus_natural.rep_eq [simp]
 
 lift_definition times_natural :: "natural \<Rightarrow> natural \<Rightarrow> natural"
   is "times :: nat \<Rightarrow> nat \<Rightarrow> nat"
   .
 
 declare times_natural.rep_eq [simp]
 
 instance proof
 qed (transfer, simp add: algebra_simps)+
 
 end
 
 instance natural :: Rings.dvd ..
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>(pcr_natural ===> pcr_natural ===> (\<longleftrightarrow>)) (dvd) (dvd)\<close>
   by (unfold dvd_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>((\<longleftrightarrow>) ===> pcr_natural) of_bool of_bool\<close>
   by (unfold of_bool_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_natural) (\<lambda>n. n) of_nat\<close>
 proof -
   have "rel_fun HOL.eq pcr_natural (of_nat :: nat \<Rightarrow> nat) (of_nat :: nat \<Rightarrow> natural)"
     by (unfold of_nat_def) transfer_prover
   then show ?thesis by (simp add: id_def)
 qed
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_natural) numeral numeral\<close>
 proof -
   have \<open>((=) ===> pcr_natural) numeral (\<lambda>n. of_nat (numeral n))\<close>
     by transfer_prover
   then show ?thesis by simp
 qed
 
 lemma [transfer_rule]:
   \<open>(pcr_natural ===> (=) ===> pcr_natural) (^) (^)\<close>
   by (unfold power_def) transfer_prover
 
 end
 
 lemma nat_of_natural_of_nat [simp]:
   "nat_of_natural (of_nat n) = n"
   by transfer rule
 
 lemma natural_of_nat_of_nat [simp, code_abbrev]:
   "natural_of_nat = of_nat"
   by transfer rule
 
 lemma of_nat_of_natural [simp]:
   "of_nat (nat_of_natural n) = n"
   by transfer rule
 
 lemma nat_of_natural_numeral [simp]:
   "nat_of_natural (numeral k) = numeral k"
   by transfer rule
 
 instantiation natural :: "{linordered_semiring, equal}"
 begin
 
 lift_definition less_eq_natural :: "natural \<Rightarrow> natural \<Rightarrow> bool"
   is "less_eq :: nat \<Rightarrow> nat \<Rightarrow> bool"
   .
 
 declare less_eq_natural.rep_eq [termination_simp]
 
 lift_definition less_natural :: "natural \<Rightarrow> natural \<Rightarrow> bool"
   is "less :: nat \<Rightarrow> nat \<Rightarrow> bool"
   .
 
 declare less_natural.rep_eq [termination_simp]
 
 lift_definition equal_natural :: "natural \<Rightarrow> natural \<Rightarrow> bool"
   is "HOL.equal :: nat \<Rightarrow> nat \<Rightarrow> bool"
   .
 
 instance proof
 qed (transfer, simp add: algebra_simps equal less_le_not_le [symmetric] linear)+
 
 end
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>(pcr_natural ===> pcr_natural ===> pcr_natural) min min\<close>
   by (unfold min_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>(pcr_natural ===> pcr_natural ===> pcr_natural) max max\<close>
   by (unfold max_def) transfer_prover
 
 end
 
 lemma nat_of_natural_min [simp]:
   "nat_of_natural (min k l) = min (nat_of_natural k) (nat_of_natural l)"
   by transfer rule
 
 lemma nat_of_natural_max [simp]:
   "nat_of_natural (max k l) = max (nat_of_natural k) (nat_of_natural l)"
   by transfer rule
 
 instantiation natural :: unique_euclidean_semiring
 begin
 
 lift_definition divide_natural :: "natural \<Rightarrow> natural \<Rightarrow> natural"
   is "divide :: nat \<Rightarrow> nat \<Rightarrow> nat"
   .
 
 declare divide_natural.rep_eq [simp]
 
 lift_definition modulo_natural :: "natural \<Rightarrow> natural \<Rightarrow> natural"
   is "modulo :: nat \<Rightarrow> nat \<Rightarrow> nat"
   .
 
 declare modulo_natural.rep_eq [simp]
 
 lift_definition euclidean_size_natural :: "natural \<Rightarrow> nat"
   is "euclidean_size :: nat \<Rightarrow> nat"
   .
 
 declare euclidean_size_natural.rep_eq [simp]
 
 lift_definition division_segment_natural :: "natural \<Rightarrow> natural"
   is "division_segment :: nat \<Rightarrow> nat"
   .
 
 declare division_segment_natural.rep_eq [simp]
 
 instance
   by (standard; transfer)
     (auto simp add: algebra_simps unit_factor_nat_def gr0_conv_Suc)
 
 end
 
 lemma [code]:
   "euclidean_size = nat_of_natural"
   by (simp add: fun_eq_iff)
 
 lemma [code]:
   "division_segment (n::natural) = 1"
   by (simp add: natural_eq_iff)
 
 instance natural :: linordered_semidom
   by (standard; transfer) simp_all
 
 instance natural :: unique_euclidean_semiring_with_nat
   by (standard; transfer) simp_all
 
 instantiation natural :: semiring_bit_operations
 begin
 
 lift_definition bit_natural :: \<open>natural \<Rightarrow> nat \<Rightarrow> bool\<close>
   is bit .
 
 lift_definition and_natural :: \<open>natural \<Rightarrow> natural \<Rightarrow> natural\<close>
   is \<open>and\<close> .
 
 lift_definition or_natural :: \<open>natural \<Rightarrow> natural \<Rightarrow> natural\<close>
   is or .
 
 lift_definition xor_natural ::  \<open>natural \<Rightarrow> natural \<Rightarrow> natural\<close>
   is xor .
 
 lift_definition mask_natural :: \<open>nat \<Rightarrow> natural\<close>
   is mask .
 
 lift_definition set_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is set_bit .
 
 lift_definition unset_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is unset_bit .
 
 lift_definition flip_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is flip_bit .
 
 lift_definition push_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is push_bit .
 
 lift_definition drop_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is drop_bit .
 
 lift_definition take_bit_natural :: \<open>nat \<Rightarrow> natural \<Rightarrow> natural\<close>
   is take_bit .
 
 instance by (standard; transfer)
   (fact bit_eq_rec bits_induct bit_iff_odd push_bit_eq_mult drop_bit_eq_div take_bit_eq_mod
     bits_div_0 bits_div_by_1 bits_mod_div_trivial even_succ_div_2
     exp_div_exp_eq div_exp_eq mod_exp_eq mult_exp_mod_exp_eq div_exp_mod_exp_eq
     even_mask_div_iff even_mult_exp_div_exp_iff bit_and_iff bit_or_iff bit_xor_iff
     mask_eq_exp_minus_1 set_bit_def bit_unset_bit_iff flip_bit_def)+
 
 end
 
 instance natural :: unique_euclidean_semiring_with_bit_operations ..
 
 context
   includes bit_operations_syntax
 begin
 
 lemma [code]:
   \<open>bit m n \<longleftrightarrow> odd (drop_bit n m)\<close>
   \<open>mask n = 2 ^ n - (1 :: integer)\<close>
   \<open>set_bit n m = m OR push_bit n 1\<close>
   \<open>flip_bit n m = m XOR push_bit n 1\<close>
   \<open>push_bit n m = m * 2 ^ n\<close>
   \<open>drop_bit n m = m div 2 ^ n\<close>
   \<open>take_bit n m = m mod 2 ^ n\<close> for m :: natural
   by (fact bit_iff_odd_drop_bit mask_eq_exp_minus_1
     set_bit_eq_or flip_bit_eq_xor push_bit_eq_mult drop_bit_eq_div take_bit_eq_mod)+
 
 lemma [code]:
   \<open>m AND n = (if m = 0 \<or> n = 0 then 0
     else (m mod 2) * (n mod 2) + 2 * ((m div 2) AND (n div 2)))\<close> for m n :: natural
   by transfer (fact and_nat_unfold)
 
 lemma [code]:
   \<open>m OR n = (if m = 0 then n else if n = 0 then m
     else max (m mod 2) (n mod 2) + 2 * ((m div 2) OR (n div 2)))\<close> for m n :: natural
   by transfer (fact or_nat_unfold)
 
 lemma [code]:
   \<open>m XOR n = (if m = 0 then n else if n = 0 then m
     else (m mod 2 + n mod 2) mod 2 + 2 * ((m div 2) XOR (n div 2)))\<close> for m n :: natural
   by transfer (fact xor_nat_unfold)
 
 lemma [code]:
   \<open>unset_bit 0 m = 2 * (m div 2)\<close>
   \<open>unset_bit (Suc n) m = m mod 2 + 2 * unset_bit n (m div 2)\<close> for m :: natural
   by (transfer; simp add: unset_bit_Suc)+
 
 end
 
 lift_definition natural_of_integer :: "integer \<Rightarrow> natural"
   is "nat :: int \<Rightarrow> nat"
   .
 
 lift_definition integer_of_natural :: "natural \<Rightarrow> integer"
   is "of_nat :: nat \<Rightarrow> int"
   .
 
 lemma natural_of_integer_of_natural [simp]:
   "natural_of_integer (integer_of_natural n) = n"
   by transfer simp
 
 lemma integer_of_natural_of_integer [simp]:
   "integer_of_natural (natural_of_integer k) = max 0 k"
   by transfer auto
 
 lemma int_of_integer_of_natural [simp]:
   "int_of_integer (integer_of_natural n) = of_nat (nat_of_natural n)"
   by transfer rule
 
 lemma integer_of_natural_of_nat [simp]:
   "integer_of_natural (of_nat n) = of_nat n"
   by transfer rule
 
 lemma [measure_function]:
   "is_measure nat_of_natural"
   by (rule is_measure_trivial)
 
 
 subsection \<open>Inductive representation of target language naturals\<close>
 
 lift_definition Suc :: "natural \<Rightarrow> natural"
   is Nat.Suc
   .
 
 declare Suc.rep_eq [simp]
 
 old_rep_datatype "0::natural" Suc
   by (transfer, fact nat.induct nat.inject nat.distinct)+
 
 lemma natural_cases [case_names nat, cases type: natural]:
   fixes m :: natural
   assumes "\<And>n. m = of_nat n \<Longrightarrow> P"
   shows P
   using assms by transfer blast
 
 instantiation natural :: size
 begin
 
 definition size_nat where [simp, code]: "size_nat = nat_of_natural"
 
 instance ..
 
 end
 
 lemma natural_decr [termination_simp]:
   "n \<noteq> 0 \<Longrightarrow> nat_of_natural n - Nat.Suc 0 < nat_of_natural n"
   by transfer simp
 
 lemma natural_zero_minus_one: "(0::natural) - 1 = 0"
   by (rule zero_diff)
 
 lemma Suc_natural_minus_one: "Suc n - 1 = n"
   by transfer simp
 
 hide_const (open) Suc
 
 
 subsection \<open>Code refinement for target language naturals\<close>
 
 lift_definition Nat :: "integer \<Rightarrow> natural"
   is nat
   .
 
 lemma [code_post]:
   "Nat 0 = 0"
   "Nat 1 = 1"
   "Nat (numeral k) = numeral k"
   by (transfer, simp)+
 
 lemma [code abstype]:
   "Nat (integer_of_natural n) = n"
   by transfer simp
 
 lemma [code]:
   "natural_of_nat n = natural_of_integer (integer_of_nat n)"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural (natural_of_integer k) = max 0 k"
   by simp
 
 lemma [code]:
   \<open>integer_of_natural (mask n) = mask n\<close>
   by transfer (simp add: mask_eq_exp_minus_1 of_nat_diff)
 
 lemma [code_abbrev]:
   "natural_of_integer (Code_Numeral.Pos k) = numeral k"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural 0 = 0"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural 1 = 1"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural (Code_Numeral.Suc n) = integer_of_natural n + 1"
   by transfer simp
 
 lemma [code]:
   "nat_of_natural = nat_of_integer \<circ> integer_of_natural"
   by transfer (simp add: fun_eq_iff)
 
 lemma [code, code_unfold]:
   "case_natural f g n = (if n = 0 then f else g (n - 1))"
   by (cases n rule: natural.exhaust) (simp_all, simp add: Suc_def)
 
 declare natural.rec [code del]
 
 lemma [code abstract]:
   "integer_of_natural (m + n) = integer_of_natural m + integer_of_natural n"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural (m - n) = max 0 (integer_of_natural m - integer_of_natural n)"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural (m * n) = integer_of_natural m * integer_of_natural n"
   by transfer simp
 
 lemma [code abstract]:
   "integer_of_natural (m div n) = integer_of_natural m div integer_of_natural n"
   by transfer (simp add: zdiv_int)
 
 lemma [code abstract]:
   "integer_of_natural (m mod n) = integer_of_natural m mod integer_of_natural n"
   by transfer (simp add: zmod_int)
 
 lemma [code]:
   "HOL.equal m n \<longleftrightarrow> HOL.equal (integer_of_natural m) (integer_of_natural n)"
   by transfer (simp add: equal)
 
 lemma [code nbe]: "HOL.equal n (n::natural) \<longleftrightarrow> True"
   by (rule equal_class.equal_refl)
 
 lemma [code]: "m \<le> n \<longleftrightarrow> integer_of_natural m \<le> integer_of_natural n"
   by transfer simp
 
 lemma [code]: "m < n \<longleftrightarrow> integer_of_natural m < integer_of_natural n"
   by transfer simp
 
 hide_const (open) Nat
 
 code_reflect Code_Numeral
   datatypes natural
   functions "Code_Numeral.Suc" "0 :: natural" "1 :: natural"
     "plus :: natural \<Rightarrow> _" "minus :: natural \<Rightarrow> _"
     "times :: natural \<Rightarrow> _" "divide :: natural \<Rightarrow> _"
     "modulo :: natural \<Rightarrow> _"
     integer_of_natural natural_of_integer
 
 lifting_update integer.lifting
 lifting_forget integer.lifting
 
 lifting_update natural.lifting
 lifting_forget natural.lifting
 
 end
diff --git a/src/HOL/Library/Word.thy b/src/HOL/Library/Word.thy
--- a/src/HOL/Library/Word.thy
+++ b/src/HOL/Library/Word.thy
@@ -1,4294 +1,4233 @@
 (*  Title:      HOL/Library/Word.thy
     Author:     Jeremy Dawson and Gerwin Klein, NICTA, et. al.
 *)
 
 section \<open>A type of finite bit strings\<close>
 
 theory Word
 imports
   "HOL-Library.Type_Length"
 begin
 
 subsection \<open>Preliminaries\<close>
 
 lemma signed_take_bit_decr_length_iff:
   \<open>signed_take_bit (LENGTH('a::len) - Suc 0) k = signed_take_bit (LENGTH('a) - Suc 0) l
     \<longleftrightarrow> take_bit LENGTH('a) k = take_bit LENGTH('a) l\<close>
   by (cases \<open>LENGTH('a)\<close>)
     (simp_all add: signed_take_bit_eq_iff_take_bit_eq)
 
 
 subsection \<open>Fundamentals\<close>
 
 subsubsection \<open>Type definition\<close>
 
 quotient_type (overloaded) 'a word = int / \<open>\<lambda>k l. take_bit LENGTH('a) k = take_bit LENGTH('a::len) l\<close>
   morphisms rep Word by (auto intro!: equivpI reflpI sympI transpI)
 
 hide_const (open) rep \<comment> \<open>only for foundational purpose\<close>
 hide_const (open) Word \<comment> \<open>only for code generation\<close>
 
 
 subsubsection \<open>Basic arithmetic\<close>
 
 instantiation word :: (len) comm_ring_1
 begin
 
 lift_definition zero_word :: \<open>'a word\<close>
   is 0 .
 
 lift_definition one_word :: \<open>'a word\<close>
   is 1 .
 
 lift_definition plus_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>(+)\<close>
   by (auto simp add: take_bit_eq_mod intro: mod_add_cong)
 
 lift_definition minus_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>(-)\<close>
   by (auto simp add: take_bit_eq_mod intro: mod_diff_cong)
 
 lift_definition uminus_word :: \<open>'a word \<Rightarrow> 'a word\<close>
   is uminus
   by (auto simp add: take_bit_eq_mod intro: mod_minus_cong)
 
 lift_definition times_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>(*)\<close>
   by (auto simp add: take_bit_eq_mod intro: mod_mult_cong)
 
 instance
   by (standard; transfer) (simp_all add: algebra_simps)
 
 end
 
 context
   includes lifting_syntax
   notes
     power_transfer [transfer_rule]
     transfer_rule_of_bool [transfer_rule]
     transfer_rule_numeral [transfer_rule]
     transfer_rule_of_nat [transfer_rule]
     transfer_rule_of_int [transfer_rule]
 begin
 
 lemma power_transfer_word [transfer_rule]:
   \<open>(pcr_word ===> (=) ===> pcr_word) (^) (^)\<close>
   by transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_word) of_bool of_bool\<close>
   by transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_word) numeral numeral\<close>
   by transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_word) int of_nat\<close>
   by transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_word) (\<lambda>k. k) of_int\<close>
 proof -
   have \<open>((=) ===> pcr_word) of_int of_int\<close>
     by transfer_prover
   then show ?thesis by (simp add: id_def)
 qed
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> (\<longleftrightarrow>)) even ((dvd) 2 :: 'a::len word \<Rightarrow> bool)\<close>
 proof -
   have even_word_unfold: "even k \<longleftrightarrow> (\<exists>l. take_bit LENGTH('a) k = take_bit LENGTH('a) (2 * l))" (is "?P \<longleftrightarrow> ?Q")
     for k :: int
   proof
     assume ?P
     then show ?Q
       by auto
   next
     assume ?Q
     then obtain l where "take_bit LENGTH('a) k = take_bit LENGTH('a) (2 * l)" ..
     then have "even (take_bit LENGTH('a) k)"
       by simp
     then show ?P
       by simp
   qed
   show ?thesis by (simp only: even_word_unfold [abs_def] dvd_def [where ?'a = "'a word", abs_def])
     transfer_prover
 qed
 
 end
 
 lemma exp_eq_zero_iff [simp]:
   \<open>2 ^ n = (0 :: 'a::len word) \<longleftrightarrow> n \<ge> LENGTH('a)\<close>
   by transfer auto
 
 lemma word_exp_length_eq_0 [simp]:
   \<open>(2 :: 'a::len word) ^ LENGTH('a) = 0\<close>
   by simp
 
 
 subsubsection \<open>Basic tool setup\<close>
 
 ML_file \<open>Tools/word_lib.ML\<close>
 
 
 subsubsection \<open>Basic code generation setup\<close>
 
 context
 begin
 
 qualified lift_definition the_int :: \<open>'a::len word \<Rightarrow> int\<close>
   is \<open>take_bit LENGTH('a)\<close> .
 
 end
 
 lemma [code abstype]:
   \<open>Word.Word (Word.the_int w) = w\<close>
   by transfer simp
 
 lemma Word_eq_word_of_int [code_post, simp]:
   \<open>Word.Word = of_int\<close>
   by (rule; transfer) simp
 
 quickcheck_generator word
   constructors:
     \<open>0 :: 'a::len word\<close>,
     \<open>numeral :: num \<Rightarrow> 'a::len word\<close>
 
 instantiation word :: (len) equal
 begin
 
 lift_definition equal_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> bool\<close>
   is \<open>\<lambda>k l. take_bit LENGTH('a) k = take_bit LENGTH('a) l\<close>
   by simp
 
 instance
   by (standard; transfer) rule
 
 end
 
 lemma [code]:
   \<open>HOL.equal v w \<longleftrightarrow> HOL.equal (Word.the_int v) (Word.the_int w)\<close>
   by transfer (simp add: equal)
 
 lemma [code]:
   \<open>Word.the_int 0 = 0\<close>
   by transfer simp
 
 lemma [code]:
   \<open>Word.the_int 1 = 1\<close>
   by transfer simp
 
 lemma [code]:
   \<open>Word.the_int (v + w) = take_bit LENGTH('a) (Word.the_int v + Word.the_int w)\<close>
   for v w :: \<open>'a::len word\<close>
   by transfer (simp add: take_bit_add)
 
 lemma [code]:
   \<open>Word.the_int (- w) = (let k = Word.the_int w in if w = 0 then 0 else 2 ^ LENGTH('a) - k)\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (auto simp add: take_bit_eq_mod zmod_zminus1_eq_if)
 
 lemma [code]:
   \<open>Word.the_int (v - w) = take_bit LENGTH('a) (Word.the_int v - Word.the_int w)\<close>
   for v w :: \<open>'a::len word\<close>
   by transfer (simp add: take_bit_diff)
 
 lemma [code]:
   \<open>Word.the_int (v * w) = take_bit LENGTH('a) (Word.the_int v * Word.the_int w)\<close>
   for v w :: \<open>'a::len word\<close>
   by transfer (simp add: take_bit_mult)
 
 
 subsubsection \<open>Basic conversions\<close>
 
 abbreviation word_of_nat :: \<open>nat \<Rightarrow> 'a::len word\<close>
   where \<open>word_of_nat \<equiv> of_nat\<close>
 
 abbreviation word_of_int :: \<open>int \<Rightarrow> 'a::len word\<close>
   where \<open>word_of_int \<equiv> of_int\<close>
 
 lemma word_of_nat_eq_iff:
   \<open>word_of_nat m = (word_of_nat n :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) m = take_bit LENGTH('a) n\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma word_of_int_eq_iff:
   \<open>word_of_int k = (word_of_int l :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) k = take_bit LENGTH('a) l\<close>
   by transfer rule
 
 lemma word_of_nat_eq_0_iff [simp]:
   \<open>word_of_nat n = (0 :: 'a::len word) \<longleftrightarrow> 2 ^ LENGTH('a) dvd n\<close>
   using word_of_nat_eq_iff [where ?'a = 'a, of n 0] by (simp add: take_bit_eq_0_iff)
 
 lemma word_of_int_eq_0_iff [simp]:
   \<open>word_of_int k = (0 :: 'a::len word) \<longleftrightarrow> 2 ^ LENGTH('a) dvd k\<close>
   using word_of_int_eq_iff [where ?'a = 'a, of k 0] by (simp add: take_bit_eq_0_iff)
 
 context semiring_1
 begin
 
 lift_definition unsigned :: \<open>'b::len word \<Rightarrow> 'a\<close>
   is \<open>of_nat \<circ> nat \<circ> take_bit LENGTH('b)\<close>
   by simp
 
 lemma unsigned_0 [simp]:
   \<open>unsigned 0 = 0\<close>
   by transfer simp
 
 lemma unsigned_1 [simp]:
   \<open>unsigned 1 = 1\<close>
   by transfer simp
 
 lemma unsigned_numeral [simp]:
   \<open>unsigned (numeral n :: 'b::len word) = of_nat (take_bit LENGTH('b) (numeral n))\<close>
   by transfer (simp add: nat_take_bit_eq)
 
 lemma unsigned_neg_numeral [simp]:
   \<open>unsigned (- numeral n :: 'b::len word) = of_nat (nat (take_bit LENGTH('b) (- numeral n)))\<close>
   by transfer simp
 
 end
 
 context semiring_1
 begin
 
 lemma unsigned_of_nat [simp]:
   \<open>unsigned (word_of_nat n :: 'b::len word) = of_nat (take_bit LENGTH('b) n)\<close>
   by transfer (simp add: nat_eq_iff take_bit_of_nat)
 
 lemma unsigned_of_int [simp]:
   \<open>unsigned (word_of_int k :: 'b::len word) = of_nat (nat (take_bit LENGTH('b) k))\<close>
   by transfer simp
 
 end
 
 context semiring_char_0
 begin
 
 lemma unsigned_word_eqI:
   \<open>v = w\<close> if \<open>unsigned v = unsigned w\<close>
   using that by transfer (simp add: eq_nat_nat_iff)
 
 lemma word_eq_iff_unsigned:
   \<open>v = w \<longleftrightarrow> unsigned v = unsigned w\<close>
   by (auto intro: unsigned_word_eqI)
 
 lemma inj_unsigned [simp]:
   \<open>inj unsigned\<close>
   by (rule injI) (simp add: unsigned_word_eqI)
 
 lemma unsigned_eq_0_iff:
   \<open>unsigned w = 0 \<longleftrightarrow> w = 0\<close>
   using word_eq_iff_unsigned [of w 0] by simp
 
 end
 
 context ring_1
 begin
 
 lift_definition signed :: \<open>'b::len word \<Rightarrow> 'a\<close>
   is \<open>of_int \<circ> signed_take_bit (LENGTH('b) - Suc 0)\<close>
   by (simp flip: signed_take_bit_decr_length_iff)
 
 lemma signed_0 [simp]:
   \<open>signed 0 = 0\<close>
   by transfer simp
 
 lemma signed_1 [simp]:
   \<open>signed (1 :: 'b::len word) = (if LENGTH('b) = 1 then - 1 else 1)\<close>
   by (transfer fixing: uminus; cases \<open>LENGTH('b)\<close>) (auto dest: gr0_implies_Suc)
 
 lemma signed_minus_1 [simp]:
   \<open>signed (- 1 :: 'b::len word) = - 1\<close>
   by (transfer fixing: uminus) simp
 
 lemma signed_numeral [simp]:
   \<open>signed (numeral n :: 'b::len word) = of_int (signed_take_bit (LENGTH('b) - 1) (numeral n))\<close>
   by transfer simp
 
 lemma signed_neg_numeral [simp]:
   \<open>signed (- numeral n :: 'b::len word) = of_int (signed_take_bit (LENGTH('b) - 1) (- numeral n))\<close>
   by transfer simp
 
 lemma signed_of_nat [simp]:
   \<open>signed (word_of_nat n :: 'b::len word) = of_int (signed_take_bit (LENGTH('b) - Suc 0) (int n))\<close>
   by transfer simp
 
 lemma signed_of_int [simp]:
   \<open>signed (word_of_int n :: 'b::len word) = of_int (signed_take_bit (LENGTH('b) - Suc 0) n)\<close>
   by transfer simp
 
 end
 
 context ring_char_0
 begin
 
 lemma signed_word_eqI:
   \<open>v = w\<close> if \<open>signed v = signed w\<close>
   using that by transfer (simp flip: signed_take_bit_decr_length_iff)
 
 lemma word_eq_iff_signed:
   \<open>v = w \<longleftrightarrow> signed v = signed w\<close>
   by (auto intro: signed_word_eqI)
 
 lemma inj_signed [simp]:
   \<open>inj signed\<close>
   by (rule injI) (simp add: signed_word_eqI)
 
 lemma signed_eq_0_iff:
   \<open>signed w = 0 \<longleftrightarrow> w = 0\<close>
   using word_eq_iff_signed [of w 0] by simp
 
 end
 
 abbreviation unat :: \<open>'a::len word \<Rightarrow> nat\<close>
   where \<open>unat \<equiv> unsigned\<close>
 
 abbreviation uint :: \<open>'a::len word \<Rightarrow> int\<close>
   where \<open>uint \<equiv> unsigned\<close>
 
 abbreviation sint :: \<open>'a::len word \<Rightarrow> int\<close>
   where \<open>sint \<equiv> signed\<close>
 
 abbreviation ucast :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>ucast \<equiv> unsigned\<close>
 
 abbreviation scast :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>scast \<equiv> signed\<close>
 
 context
   includes lifting_syntax
 begin
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> (=)) (nat \<circ> take_bit LENGTH('a)) (unat :: 'a::len word \<Rightarrow> nat)\<close>
   using unsigned.transfer [where ?'a = nat] by simp
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> (=)) (take_bit LENGTH('a)) (uint :: 'a::len word \<Rightarrow> int)\<close>
   using unsigned.transfer [where ?'a = int] by (simp add: comp_def)
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> (=)) (signed_take_bit (LENGTH('a) - Suc 0)) (sint :: 'a::len word \<Rightarrow> int)\<close>
   using signed.transfer [where ?'a = int] by simp
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> pcr_word) (take_bit LENGTH('a)) (ucast :: 'a::len word \<Rightarrow> 'b::len word)\<close>
 proof (rule rel_funI)
   fix k :: int and w :: \<open>'a word\<close>
   assume \<open>pcr_word k w\<close>
   then have \<open>w = word_of_int k\<close>
     by (simp add: pcr_word_def cr_word_def relcompp_apply)
   moreover have \<open>pcr_word (take_bit LENGTH('a) k) (ucast (word_of_int k :: 'a word))\<close>
     by transfer (simp add: pcr_word_def cr_word_def relcompp_apply)
   ultimately show \<open>pcr_word (take_bit LENGTH('a) k) (ucast w)\<close>
     by simp
 qed
 
 lemma [transfer_rule]:
   \<open>(pcr_word ===> pcr_word) (signed_take_bit (LENGTH('a) - Suc 0)) (scast :: 'a::len word \<Rightarrow> 'b::len word)\<close>
 proof (rule rel_funI)
   fix k :: int and w :: \<open>'a word\<close>
   assume \<open>pcr_word k w\<close>
   then have \<open>w = word_of_int k\<close>
     by (simp add: pcr_word_def cr_word_def relcompp_apply)
   moreover have \<open>pcr_word (signed_take_bit (LENGTH('a) - Suc 0) k) (scast (word_of_int k :: 'a word))\<close>
     by transfer (simp add: pcr_word_def cr_word_def relcompp_apply)
   ultimately show \<open>pcr_word (signed_take_bit (LENGTH('a) - Suc 0) k) (scast w)\<close>
     by simp
 qed
 
 end
 
 lemma of_nat_unat [simp]:
   \<open>of_nat (unat w) = unsigned w\<close>
   by transfer simp
 
 lemma of_int_uint [simp]:
   \<open>of_int (uint w) = unsigned w\<close>
   by transfer simp
 
 lemma of_int_sint [simp]:
   \<open>of_int (sint a) = signed a\<close>
   by transfer (simp_all add: take_bit_signed_take_bit)
 
 lemma nat_uint_eq [simp]:
   \<open>nat (uint w) = unat w\<close>
   by transfer simp
 
 lemma sgn_uint_eq [simp]:
   \<open>sgn (uint w) = of_bool (w \<noteq> 0)\<close>
   by transfer (simp add: less_le)
 
 text \<open>Aliasses only for code generation\<close>
 
 context
 begin
 
 qualified lift_definition of_int :: \<open>int \<Rightarrow> 'a::len word\<close>
   is \<open>take_bit LENGTH('a)\<close> .
 
 qualified lift_definition of_nat :: \<open>nat \<Rightarrow> 'a::len word\<close>
   is \<open>int \<circ> take_bit LENGTH('a)\<close> .
 
 qualified lift_definition the_nat :: \<open>'a::len word \<Rightarrow> nat\<close>
   is \<open>nat \<circ> take_bit LENGTH('a)\<close> by simp
 
 qualified lift_definition the_signed_int :: \<open>'a::len word \<Rightarrow> int\<close>
   is \<open>signed_take_bit (LENGTH('a) - Suc 0)\<close> by (simp add: signed_take_bit_decr_length_iff)
 
 qualified lift_definition cast :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   is \<open>take_bit LENGTH('a)\<close> by simp
 
 qualified lift_definition signed_cast :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   is \<open>signed_take_bit (LENGTH('a) - Suc 0)\<close> by (metis signed_take_bit_decr_length_iff)
 
 end
 
 lemma [code_abbrev, simp]:
   \<open>Word.the_int = uint\<close>
   by transfer rule
 
 lemma [code]:
   \<open>Word.the_int (Word.of_int k :: 'a::len word) = take_bit LENGTH('a) k\<close>
   by transfer simp
 
 lemma [code_abbrev, simp]:
   \<open>Word.of_int = word_of_int\<close>
   by (rule; transfer) simp
 
 lemma [code]:
   \<open>Word.the_int (Word.of_nat n :: 'a::len word) = take_bit LENGTH('a) (int n)\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma [code_abbrev, simp]:
   \<open>Word.of_nat = word_of_nat\<close>
   by (rule; transfer) (simp add: take_bit_of_nat)
 
 lemma [code]:
   \<open>Word.the_nat w = nat (Word.the_int w)\<close>
   by transfer simp
 
 lemma [code_abbrev, simp]:
   \<open>Word.the_nat = unat\<close>
   by (rule; transfer) simp
 
 lemma [code]:
   \<open>Word.the_signed_int w = signed_take_bit (LENGTH('a) - Suc 0) (Word.the_int w)\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (simp add: signed_take_bit_take_bit)
 
 lemma [code_abbrev, simp]:
   \<open>Word.the_signed_int = sint\<close>
   by (rule; transfer) simp
 
 lemma [code]:
   \<open>Word.the_int (Word.cast w :: 'b::len word) = take_bit LENGTH('b) (Word.the_int w)\<close>
   for w :: \<open>'a::len word\<close>
   by transfer simp
 
 lemma [code_abbrev, simp]:
   \<open>Word.cast = ucast\<close>
   by (rule; transfer) simp
 
 lemma [code]:
   \<open>Word.the_int (Word.signed_cast w :: 'b::len word) = take_bit LENGTH('b) (Word.the_signed_int w)\<close>
   for w :: \<open>'a::len word\<close>
   by transfer simp
 
 lemma [code_abbrev, simp]:
   \<open>Word.signed_cast = scast\<close>
   by (rule; transfer) simp
 
 lemma [code]:
   \<open>unsigned w = of_nat (nat (Word.the_int w))\<close>
   by transfer simp
 
 lemma [code]:
   \<open>signed w = of_int (Word.the_signed_int w)\<close>
   by transfer simp
 
 
 subsubsection \<open>Basic ordering\<close>
 
 instantiation word :: (len) linorder
 begin
 
 lift_definition less_eq_word :: "'a word \<Rightarrow> 'a word \<Rightarrow> bool"
   is "\<lambda>a b. take_bit LENGTH('a) a \<le> take_bit LENGTH('a) b"
   by simp
 
 lift_definition less_word :: "'a word \<Rightarrow> 'a word \<Rightarrow> bool"
   is "\<lambda>a b. take_bit LENGTH('a) a < take_bit LENGTH('a) b"
   by simp
 
 instance
   by (standard; transfer) auto
 
 end
 
 interpretation word_order: ordering_top \<open>(\<le>)\<close> \<open>(<)\<close> \<open>- 1 :: 'a::len word\<close>
   by (standard; transfer) (simp add: take_bit_eq_mod zmod_minus1)
 
 interpretation word_coorder: ordering_top \<open>(\<ge>)\<close> \<open>(>)\<close> \<open>0 :: 'a::len word\<close>
   by (standard; transfer) simp
 
 lemma word_of_nat_less_eq_iff:
   \<open>word_of_nat m \<le> (word_of_nat n :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) m \<le> take_bit LENGTH('a) n\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma word_of_int_less_eq_iff:
   \<open>word_of_int k \<le> (word_of_int l :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) k \<le> take_bit LENGTH('a) l\<close>
   by transfer rule
 
 lemma word_of_nat_less_iff:
   \<open>word_of_nat m < (word_of_nat n :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) m < take_bit LENGTH('a) n\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma word_of_int_less_iff:
   \<open>word_of_int k < (word_of_int l :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) k < take_bit LENGTH('a) l\<close>
   by transfer rule
 
 lemma word_le_def [code]:
   "a \<le> b \<longleftrightarrow> uint a \<le> uint b"
   by transfer rule
 
 lemma word_less_def [code]:
   "a < b \<longleftrightarrow> uint a < uint b"
   by transfer rule
 
 lemma word_greater_zero_iff:
   \<open>a > 0 \<longleftrightarrow> a \<noteq> 0\<close> for a :: \<open>'a::len word\<close>
   by transfer (simp add: less_le)
 
 lemma of_nat_word_less_eq_iff:
   \<open>of_nat m \<le> (of_nat n :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) m \<le> take_bit LENGTH('a) n\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma of_nat_word_less_iff:
   \<open>of_nat m < (of_nat n :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) m < take_bit LENGTH('a) n\<close>
   by transfer (simp add: take_bit_of_nat)
 
 lemma of_int_word_less_eq_iff:
   \<open>of_int k \<le> (of_int l :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) k \<le> take_bit LENGTH('a) l\<close>
   by transfer rule
 
 lemma of_int_word_less_iff:
   \<open>of_int k < (of_int l :: 'a::len word) \<longleftrightarrow> take_bit LENGTH('a) k < take_bit LENGTH('a) l\<close>
   by transfer rule
 
 
 
 subsection \<open>Enumeration\<close>
 
 lemma inj_on_word_of_nat:
   \<open>inj_on (word_of_nat :: nat \<Rightarrow> 'a::len word) {0..<2 ^ LENGTH('a)}\<close>
   by (rule inj_onI; transfer) (simp_all add: take_bit_int_eq_self)
 
 lemma UNIV_word_eq_word_of_nat:
   \<open>(UNIV :: 'a::len word set) = word_of_nat ` {0..<2 ^ LENGTH('a)}\<close> (is \<open>_ = ?A\<close>)
 proof
   show \<open>word_of_nat ` {0..<2 ^ LENGTH('a)} \<subseteq> UNIV\<close>
     by simp
   show \<open>UNIV \<subseteq> ?A\<close>
   proof
     fix w :: \<open>'a word\<close>
     show \<open>w \<in> (word_of_nat ` {0..<2 ^ LENGTH('a)} :: 'a word set)\<close>
       by (rule image_eqI [of _ _ \<open>unat w\<close>]; transfer) simp_all
   qed
 qed
 
 instantiation word :: (len) enum
 begin
 
 definition enum_word :: \<open>'a word list\<close>
   where \<open>enum_word = map word_of_nat [0..<2 ^ LENGTH('a)]\<close>
 
 definition enum_all_word :: \<open>('a word \<Rightarrow> bool) \<Rightarrow> bool\<close>
   where \<open>enum_all_word = Ball UNIV\<close>
 
 definition enum_ex_word :: \<open>('a word \<Rightarrow> bool) \<Rightarrow> bool\<close>
   where \<open>enum_ex_word = Bex UNIV\<close>
 
 lemma [code]:
   \<open>Enum.enum_all P \<longleftrightarrow> Ball UNIV P\<close>
   \<open>Enum.enum_ex P \<longleftrightarrow> Bex UNIV P\<close> for P :: \<open>'a word \<Rightarrow> bool\<close>
   by (simp_all add: enum_all_word_def enum_ex_word_def)
 
 instance
   by standard (simp_all add: UNIV_word_eq_word_of_nat inj_on_word_of_nat enum_word_def enum_all_word_def enum_ex_word_def distinct_map)
 
 end
 
 
 subsection \<open>Bit-wise operations\<close>
 
 instantiation word :: (len) semiring_modulo
 begin
 
 lift_definition divide_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>\<lambda>a b. take_bit LENGTH('a) a div take_bit LENGTH('a) b\<close>
   by simp
 
 lift_definition modulo_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>\<lambda>a b. take_bit LENGTH('a) a mod take_bit LENGTH('a) b\<close>
   by simp
 
 instance proof
   show "a div b * b + a mod b = a" for a b :: "'a word"
   proof transfer
     fix k l :: int
     define r :: int where "r = 2 ^ LENGTH('a)"
     then have r: "take_bit LENGTH('a) k = k mod r" for k
       by (simp add: take_bit_eq_mod)
     have "k mod r = ((k mod r) div (l mod r) * (l mod r)
       + (k mod r) mod (l mod r)) mod r"
       by (simp add: div_mult_mod_eq)
     also have "... = (((k mod r) div (l mod r) * (l mod r)) mod r
       + (k mod r) mod (l mod r)) mod r"
       by (simp add: mod_add_left_eq)
     also have "... = (((k mod r) div (l mod r) * l) mod r
       + (k mod r) mod (l mod r)) mod r"
       by (simp add: mod_mult_right_eq)
     finally have "k mod r = ((k mod r) div (l mod r) * l
       + (k mod r) mod (l mod r)) mod r"
       by (simp add: mod_simps)
     with r show "take_bit LENGTH('a) (take_bit LENGTH('a) k div take_bit LENGTH('a) l * l
       + take_bit LENGTH('a) k mod take_bit LENGTH('a) l) = take_bit LENGTH('a) k"
       by simp
   qed
 qed
 
 end
 
 instance word :: (len) semiring_parity
 proof
   show "\<not> 2 dvd (1::'a word)"
     by transfer simp
   show even_iff_mod_2_eq_0: "2 dvd a \<longleftrightarrow> a mod 2 = 0"
     for a :: "'a word"
     by transfer (simp_all add: mod_2_eq_odd take_bit_Suc)
   show "\<not> 2 dvd a \<longleftrightarrow> a mod 2 = 1"
     for a :: "'a word"
     by transfer (simp_all add: mod_2_eq_odd take_bit_Suc)
 qed
 
 lemma word_bit_induct [case_names zero even odd]:
   \<open>P a\<close> if word_zero: \<open>P 0\<close>
     and word_even: \<open>\<And>a. P a \<Longrightarrow> 0 < a \<Longrightarrow> a < 2 ^ (LENGTH('a) - Suc 0) \<Longrightarrow> P (2 * a)\<close>
     and word_odd: \<open>\<And>a. P a \<Longrightarrow> a < 2 ^ (LENGTH('a) - Suc 0) \<Longrightarrow> P (1 + 2 * a)\<close>
   for P and a :: \<open>'a::len word\<close>
 proof -
   define m :: nat where \<open>m = LENGTH('a) - Suc 0\<close>
   then have l: \<open>LENGTH('a) = Suc m\<close>
     by simp
   define n :: nat where \<open>n = unat a\<close>
   then have \<open>n < 2 ^ LENGTH('a)\<close>
     by transfer (simp add: take_bit_eq_mod)
   then have \<open>n < 2 * 2 ^ m\<close>
     by (simp add: l)
   then have \<open>P (of_nat n)\<close>
   proof (induction n rule: nat_bit_induct)
     case zero
     show ?case
       by simp (rule word_zero)
   next
     case (even n)
     then have \<open>n < 2 ^ m\<close>
       by simp
     with even.IH have \<open>P (of_nat n)\<close>
       by simp
     moreover from \<open>n < 2 ^ m\<close> even.hyps have \<open>0 < (of_nat n :: 'a word)\<close>
       by (auto simp add: word_greater_zero_iff l)
     moreover from \<open>n < 2 ^ m\<close> have \<open>(of_nat n :: 'a word) < 2 ^ (LENGTH('a) - Suc 0)\<close>
       using of_nat_word_less_iff [where ?'a = 'a, of n \<open>2 ^ m\<close>]
       by (simp add: l take_bit_eq_mod)
     ultimately have \<open>P (2 * of_nat n)\<close>
       by (rule word_even)
     then show ?case
       by simp
   next
     case (odd n)
     then have \<open>Suc n \<le> 2 ^ m\<close>
       by simp
     with odd.IH have \<open>P (of_nat n)\<close>
       by simp
     moreover from \<open>Suc n \<le> 2 ^ m\<close> have \<open>(of_nat n :: 'a word) < 2 ^ (LENGTH('a) - Suc 0)\<close>
       using of_nat_word_less_iff [where ?'a = 'a, of n \<open>2 ^ m\<close>]
       by (simp add: l take_bit_eq_mod)
     ultimately have \<open>P (1 + 2 * of_nat n)\<close>
       by (rule word_odd)
     then show ?case
       by simp
   qed
   moreover have \<open>of_nat (nat (uint a)) = a\<close>
     by transfer simp
   ultimately show ?thesis
     by (simp add: n_def)
 qed
 
 lemma bit_word_half_eq:
   \<open>(of_bool b + a * 2) div 2 = a\<close>
     if \<open>a < 2 ^ (LENGTH('a) - Suc 0)\<close>
     for a :: \<open>'a::len word\<close>
 proof (cases \<open>2 \<le> LENGTH('a::len)\<close>)
   case False
   have \<open>of_bool (odd k) < (1 :: int) \<longleftrightarrow> even k\<close> for k :: int
     by auto
   with False that show ?thesis
     by transfer (simp add: eq_iff)
 next
   case True
   obtain n where length: \<open>LENGTH('a) = Suc n\<close>
     by (cases \<open>LENGTH('a)\<close>) simp_all
   show ?thesis proof (cases b)
     case False
     moreover have \<open>a * 2 div 2 = a\<close>
     using that proof transfer
       fix k :: int
       from length have \<open>k * 2 mod 2 ^ LENGTH('a) = (k mod 2 ^ n) * 2\<close>
         by simp
       moreover assume \<open>take_bit LENGTH('a) k < take_bit LENGTH('a) (2 ^ (LENGTH('a) - Suc 0))\<close>
       with \<open>LENGTH('a) = Suc n\<close>
       have \<open>k mod 2 ^ LENGTH('a) = k mod 2 ^ n\<close>
         by (simp add: take_bit_eq_mod divmod_digit_0)
       ultimately have \<open>take_bit LENGTH('a) (k * 2) = take_bit LENGTH('a) k * 2\<close>
         by (simp add: take_bit_eq_mod)
       with True show \<open>take_bit LENGTH('a) (take_bit LENGTH('a) (k * 2) div take_bit LENGTH('a) 2)
         = take_bit LENGTH('a) k\<close>
         by simp
     qed
     ultimately show ?thesis
       by simp
   next
     case True
     moreover have \<open>(1 + a * 2) div 2 = a\<close>
     using that proof transfer
       fix k :: int
       from length have \<open>(1 + k * 2) mod 2 ^ LENGTH('a) = 1 + (k mod 2 ^ n) * 2\<close>
         using pos_zmod_mult_2 [of \<open>2 ^ n\<close> k] by (simp add: ac_simps)
       moreover assume \<open>take_bit LENGTH('a) k < take_bit LENGTH('a) (2 ^ (LENGTH('a) - Suc 0))\<close>
       with \<open>LENGTH('a) = Suc n\<close>
       have \<open>k mod 2 ^ LENGTH('a) = k mod 2 ^ n\<close>
         by (simp add: take_bit_eq_mod divmod_digit_0)
       ultimately have \<open>take_bit LENGTH('a) (1 + k * 2) = 1 + take_bit LENGTH('a) k * 2\<close>
         by (simp add: take_bit_eq_mod)
       with True show \<open>take_bit LENGTH('a) (take_bit LENGTH('a) (1 + k * 2) div take_bit LENGTH('a) 2)
         = take_bit LENGTH('a) k\<close>
         by (auto simp add: take_bit_Suc)
     qed
     ultimately show ?thesis
       by simp
   qed
 qed
 
 lemma even_mult_exp_div_word_iff:
   \<open>even (a * 2 ^ m div 2 ^ n) \<longleftrightarrow> \<not> (
     m \<le> n \<and>
     n < LENGTH('a) \<and> odd (a div 2 ^ (n - m)))\<close> for a :: \<open>'a::len word\<close>
   by transfer
     (auto simp flip: drop_bit_eq_div simp add: even_drop_bit_iff_not_bit bit_take_bit_iff,
       simp_all flip: push_bit_eq_mult add: bit_push_bit_iff_int)
 
 instantiation word :: (len) semiring_bits
 begin
 
 lift_definition bit_word :: \<open>'a word \<Rightarrow> nat \<Rightarrow> bool\<close>
   is \<open>\<lambda>k n. n < LENGTH('a) \<and> bit k n\<close>
 proof
   fix k l :: int and n :: nat
   assume *: \<open>take_bit LENGTH('a) k = take_bit LENGTH('a) l\<close>
   show \<open>n < LENGTH('a) \<and> bit k n \<longleftrightarrow> n < LENGTH('a) \<and> bit l n\<close>
   proof (cases \<open>n < LENGTH('a)\<close>)
     case True
     from * have \<open>bit (take_bit LENGTH('a) k) n \<longleftrightarrow> bit (take_bit LENGTH('a) l) n\<close>
       by simp
     then show ?thesis
       by (simp add: bit_take_bit_iff)
   next
     case False
     then show ?thesis
       by simp
   qed
 qed
 
 instance proof
   show \<open>P a\<close> if stable: \<open>\<And>a. a div 2 = a \<Longrightarrow> P a\<close>
     and rec: \<open>\<And>a b. P a \<Longrightarrow> (of_bool b + 2 * a) div 2 = a \<Longrightarrow> P (of_bool b + 2 * a)\<close>
   for P and a :: \<open>'a word\<close>
   proof (induction a rule: word_bit_induct)
     case zero
     have \<open>0 div 2 = (0::'a word)\<close>
       by transfer simp
     with stable [of 0] show ?case
       by simp
   next
     case (even a)
     with rec [of a False] show ?case
       using bit_word_half_eq [of a False] by (simp add: ac_simps)
   next
     case (odd a)
     with rec [of a True] show ?case
       using bit_word_half_eq [of a True] by (simp add: ac_simps)
   qed
   show \<open>bit a n \<longleftrightarrow> odd (a div 2 ^ n)\<close> for a :: \<open>'a word\<close> and n
     by transfer (simp flip: drop_bit_eq_div add: drop_bit_take_bit bit_iff_odd_drop_bit)
   show \<open>0 div a = 0\<close>
     for a :: \<open>'a word\<close>
     by transfer simp
   show \<open>a div 1 = a\<close>
     for a :: \<open>'a word\<close>
     by transfer simp
   have \<section>: "\<And>i n. (i::int) mod 2 ^ n = 0 \<or> 0 < i mod 2 ^ n"
     by (metis le_less take_bit_eq_mod take_bit_nonnegative)
   have less_power: "\<And>n i p. (i::int) mod numeral p ^ n < numeral p ^ n"
     by simp
   show \<open>a mod b div b = 0\<close>
     for a b :: \<open>'a word\<close>
     apply transfer
     apply (simp add: take_bit_eq_mod mod_eq_0_iff_dvd dvd_def)
     by (metis (no_types, opaque_lifting) "\<section>" Euclidean_Division.pos_mod_bound Euclidean_Division.pos_mod_sign le_less_trans mult_eq_0_iff take_bit_eq_mod take_bit_nonnegative zdiv_eq_0_iff zmod_le_nonneg_dividend)
   show \<open>(1 + a) div 2 = a div 2\<close>
     if \<open>even a\<close>
     for a :: \<open>'a word\<close>
     using that by transfer
       (auto dest: le_Suc_ex simp add: take_bit_Suc elim!: evenE)
   show \<open>(2 :: 'a word) ^ m div 2 ^ n = of_bool ((2 :: 'a word) ^ m \<noteq> 0 \<and> n \<le> m) * 2 ^ (m - n)\<close>
     for m n :: nat
     by transfer (simp, simp add: exp_div_exp_eq)
   show "a div 2 ^ m div 2 ^ n = a div 2 ^ (m + n)"
     for a :: "'a word" and m n :: nat
     apply transfer
     apply (auto simp add: not_less take_bit_drop_bit ac_simps simp flip: drop_bit_eq_div)
     apply (simp add: drop_bit_take_bit)
     done
   show "a mod 2 ^ m mod 2 ^ n = a mod 2 ^ min m n"
     for a :: "'a word" and m n :: nat
     by transfer (auto simp flip: take_bit_eq_mod simp add: ac_simps)
   show \<open>a * 2 ^ m mod 2 ^ n = a mod 2 ^ (n - m) * 2 ^ m\<close>
     if \<open>m \<le> n\<close> for a :: "'a word" and m n :: nat
     using that apply transfer
     apply (auto simp flip: take_bit_eq_mod)
            apply (auto simp flip: push_bit_eq_mult simp add: push_bit_take_bit split: split_min_lin)
     done
   show \<open>a div 2 ^ n mod 2 ^ m = a mod (2 ^ (n + m)) div 2 ^ n\<close>
     for a :: "'a word" and m n :: nat
     by transfer (auto simp add: not_less take_bit_drop_bit ac_simps simp flip: take_bit_eq_mod drop_bit_eq_div split: split_min_lin)
   show \<open>even ((2 ^ m - 1) div (2::'a word) ^ n) \<longleftrightarrow> 2 ^ n = (0::'a word) \<or> m \<le> n\<close>
     for m n :: nat
     by transfer (auto simp add: take_bit_of_mask even_mask_div_iff)
   show \<open>even (a * 2 ^ m div 2 ^ n) \<longleftrightarrow> n < m \<or> (2::'a word) ^ n = 0 \<or> m \<le> n \<and> even (a div 2 ^ (n - m))\<close>
     for a :: \<open>'a word\<close> and m n :: nat
   proof transfer
     show \<open>even (take_bit LENGTH('a) (k * 2 ^ m) div take_bit LENGTH('a) (2 ^ n)) \<longleftrightarrow>
       n < m
       \<or> take_bit LENGTH('a) ((2::int) ^ n) = take_bit LENGTH('a) 0
       \<or> (m \<le> n \<and> even (take_bit LENGTH('a) k div take_bit LENGTH('a) (2 ^ (n - m))))\<close>
     for m n :: nat and k l :: int
       by (auto simp flip: take_bit_eq_mod drop_bit_eq_div push_bit_eq_mult
         simp add: div_push_bit_of_1_eq_drop_bit drop_bit_take_bit drop_bit_push_bit_int [of n m])
   qed
 qed
 
 end
 
 lemma bit_word_eqI:
   \<open>a = b\<close> if \<open>\<And>n. n < LENGTH('a) \<Longrightarrow> bit a n \<longleftrightarrow> bit b n\<close>
   for a b :: \<open>'a::len word\<close>
   using that by transfer (auto simp add: nat_less_le bit_eq_iff bit_take_bit_iff)
 
 lemma bit_imp_le_length:
   \<open>n < LENGTH('a)\<close> if \<open>bit w n\<close>
     for w :: \<open>'a::len word\<close>
   using that by transfer simp
 
 lemma not_bit_length [simp]:
   \<open>\<not> bit w LENGTH('a)\<close> for w :: \<open>'a::len word\<close>
   by transfer simp
 
 lemma finite_bit_word [simp]:
   \<open>finite {n. bit w n}\<close>
   for w :: \<open>'a::len word\<close>
 proof -
   have \<open>{n. bit w n} \<subseteq> {0..LENGTH('a)}\<close>
     by (auto dest: bit_imp_le_length)
   moreover have \<open>finite {0..LENGTH('a)}\<close>
     by simp
   ultimately show ?thesis
     by (rule finite_subset)
 qed
 
 lemma bit_numeral_word_iff [simp]:
   \<open>bit (numeral w :: 'a::len word) n
     \<longleftrightarrow> n < LENGTH('a) \<and> bit (numeral w :: int) n\<close>
   by transfer simp
 
 lemma bit_neg_numeral_word_iff [simp]:
   \<open>bit (- numeral w :: 'a::len word) n
     \<longleftrightarrow> n < LENGTH('a) \<and> bit (- numeral w :: int) n\<close>
   by transfer simp
 
 instantiation word :: (len) ring_bit_operations
 begin
 
 lift_definition not_word :: \<open>'a word \<Rightarrow> 'a word\<close>
   is not
   by (simp add: take_bit_not_iff)
 
 lift_definition and_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>and\<close>
   by simp
 
 lift_definition or_word :: \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is or
   by simp
 
 lift_definition xor_word ::  \<open>'a word \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is xor
   by simp
 
 lift_definition mask_word :: \<open>nat \<Rightarrow> 'a word\<close>
   is mask
   .
 
 lift_definition set_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is set_bit
   by (simp add: set_bit_def)
 
 lift_definition unset_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is unset_bit
   by (simp add: unset_bit_def)
 
 lift_definition flip_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is flip_bit
   by (simp add: flip_bit_def)
 
 lift_definition push_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is push_bit
 proof -
   show \<open>take_bit LENGTH('a) (push_bit n k) = take_bit LENGTH('a) (push_bit n l)\<close>
     if \<open>take_bit LENGTH('a) k = take_bit LENGTH('a) l\<close> for k l :: int and n :: nat
   proof -
     from that
     have \<open>take_bit (LENGTH('a) - n) (take_bit LENGTH('a) k)
       = take_bit (LENGTH('a) - n) (take_bit LENGTH('a) l)\<close>
       by simp
     moreover have \<open>min (LENGTH('a) - n) LENGTH('a) = LENGTH('a) - n\<close>
       by simp
     ultimately show ?thesis
       by (simp add: take_bit_push_bit)
   qed
 qed
 
 lift_definition drop_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>\<lambda>n. drop_bit n \<circ> take_bit LENGTH('a)\<close>
   by (simp add: take_bit_eq_mod)
 
 lift_definition take_bit_word :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a word\<close>
   is \<open>\<lambda>n. take_bit (min LENGTH('a) n)\<close>
   by (simp add: ac_simps) (simp only: flip: take_bit_take_bit)
 
 instance apply (standard; transfer)
   apply (auto simp add: minus_eq_not_minus_1 mask_eq_exp_minus_1
     bit_simps set_bit_def flip_bit_def take_bit_drop_bit
     simp flip: drop_bit_eq_div take_bit_eq_mod)
    apply (simp_all add: drop_bit_take_bit flip: push_bit_eq_mult)
   done
 
 end
 
 lemma [code]:
   \<open>push_bit n w = w * 2 ^ n\<close> for w :: \<open>'a::len word\<close>
   by (fact push_bit_eq_mult)
 
 lemma [code]:
   \<open>Word.the_int (drop_bit n w) = drop_bit n (Word.the_int w)\<close>
   by transfer (simp add: drop_bit_take_bit min_def le_less less_diff_conv)
 
 lemma [code]:
   \<open>Word.the_int (take_bit n w) = (if n < LENGTH('a::len) then take_bit n (Word.the_int w) else Word.the_int w)\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (simp add: not_le not_less ac_simps min_absorb2)
 
 lemma [code_abbrev]:
   \<open>push_bit n 1 = (2 :: 'a::len word) ^ n\<close>
   by (fact push_bit_of_1)
 
 lemma [code]:
   \<open>NOT w = Word.of_int (NOT (Word.the_int w))\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (simp add: take_bit_not_take_bit) 
 
 context
   includes bit_operations_syntax
 begin
 
 lemma [code]:
   \<open>Word.the_int (v AND w) = Word.the_int v AND Word.the_int w\<close>
   by transfer simp
 
 lemma [code]:
   \<open>Word.the_int (v OR w) = Word.the_int v OR Word.the_int w\<close>
   by transfer simp
 
 lemma [code]:
   \<open>Word.the_int (v XOR w) = Word.the_int v XOR Word.the_int w\<close>
   by transfer simp
 
 lemma [code]:
   \<open>Word.the_int (mask n :: 'a::len word) = mask (min LENGTH('a) n)\<close>
   by transfer simp
 
 lemma [code]:
   \<open>set_bit n w = w OR push_bit n 1\<close> for w :: \<open>'a::len word\<close>
   by (fact set_bit_eq_or)
 
 lemma [code]:
   \<open>unset_bit n w = w AND NOT (push_bit n 1)\<close> for w :: \<open>'a::len word\<close>
   by (fact unset_bit_eq_and_not)
 
 lemma [code]:
   \<open>flip_bit n w = w XOR push_bit n 1\<close> for w :: \<open>'a::len word\<close>
   by (fact flip_bit_eq_xor)
 
 context
   includes lifting_syntax
 begin
 
 lemma set_bit_word_transfer [transfer_rule]:
   \<open>((=) ===> pcr_word ===> pcr_word) set_bit set_bit\<close>
   by (unfold set_bit_def) transfer_prover
 
 lemma unset_bit_word_transfer [transfer_rule]:
   \<open>((=) ===> pcr_word ===> pcr_word) unset_bit unset_bit\<close>
   by (unfold unset_bit_def) transfer_prover
 
 lemma flip_bit_word_transfer [transfer_rule]:
   \<open>((=) ===> pcr_word ===> pcr_word) flip_bit flip_bit\<close>
   by (unfold flip_bit_def) transfer_prover
 
 lemma signed_take_bit_word_transfer [transfer_rule]:
   \<open>((=) ===> pcr_word ===> pcr_word)
     (\<lambda>n k. signed_take_bit n (take_bit LENGTH('a::len) k))
     (signed_take_bit :: nat \<Rightarrow> 'a word \<Rightarrow> 'a word)\<close>
 proof -
   let ?K = \<open>\<lambda>n (k :: int). take_bit (min LENGTH('a) n) k OR of_bool (n < LENGTH('a) \<and> bit k n) * NOT (mask n)\<close>
   let ?W = \<open>\<lambda>n (w :: 'a word). take_bit n w OR of_bool (bit w n) * NOT (mask n)\<close>
   have \<open>((=) ===> pcr_word ===> pcr_word) ?K ?W\<close>
     by transfer_prover
   also have \<open>?K = (\<lambda>n k. signed_take_bit n (take_bit LENGTH('a::len) k))\<close>
     by (simp add: fun_eq_iff signed_take_bit_def bit_take_bit_iff ac_simps)
   also have \<open>?W = signed_take_bit\<close>
     by (simp add: fun_eq_iff signed_take_bit_def)
   finally show ?thesis .
 qed
 
 end
 
 end
 
 
 subsection \<open>Conversions including casts\<close>
 
 subsubsection \<open>Generic unsigned conversion\<close>
 
 context semiring_bits
 begin
 
 lemma bit_unsigned_iff [bit_simps]:
-  \<open>bit (unsigned w) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> bit w n\<close>
+  \<open>bit (unsigned w) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> bit w n\<close>
   for w :: \<open>'b::len word\<close>
   by (transfer fixing: bit) (simp add: bit_of_nat_iff bit_nat_iff bit_take_bit_iff)
 
 end
 
+lemma possible_bit_word[simp]:
+  \<open>possible_bit TYPE(('a :: len) word) m \<longleftrightarrow> m < LENGTH('a)\<close>
+  by (simp add: possible_bit_def linorder_not_le)
+
 context semiring_bit_operations
 begin
 
 lemma unsigned_push_bit_eq:
   \<open>unsigned (push_bit n w) = take_bit LENGTH('b) (push_bit n (unsigned w))\<close>
   for w :: \<open>'b::len word\<close>
 proof (rule bit_eqI)
   fix m
-  assume \<open>2 ^ m \<noteq> 0\<close>
+  assume \<open>possible_bit TYPE('a) m\<close>
   show \<open>bit (unsigned (push_bit n w)) m = bit (take_bit LENGTH('b) (push_bit n (unsigned w))) m\<close>
   proof (cases \<open>n \<le> m\<close>)
     case True
-    with \<open>2 ^ m \<noteq> 0\<close> have \<open>2 ^ (m - n) \<noteq> 0\<close>
-      by (metis (full_types) diff_add exp_add_not_zero_imp)
+    with \<open>possible_bit TYPE('a) m\<close> have \<open>possible_bit TYPE('a) (m - n)\<close>
+      by (simp add: possible_bit_less_imp)
     with True show ?thesis
       by (simp add: bit_unsigned_iff bit_push_bit_iff Bit_Operations.bit_push_bit_iff bit_take_bit_iff not_le ac_simps)
   next
     case False
     then show ?thesis
       by (simp add: not_le bit_unsigned_iff bit_push_bit_iff Bit_Operations.bit_push_bit_iff bit_take_bit_iff)
   qed
 qed
 
 lemma unsigned_take_bit_eq:
   \<open>unsigned (take_bit n w) = take_bit n (unsigned w)\<close>
   for w :: \<open>'b::len word\<close>
   by (rule bit_eqI) (simp add: bit_unsigned_iff bit_take_bit_iff Bit_Operations.bit_take_bit_iff)
 
 end
 
 context unique_euclidean_semiring_with_bit_operations
 begin
 
 lemma unsigned_drop_bit_eq:
   \<open>unsigned (drop_bit n w) = drop_bit n (take_bit LENGTH('b) (unsigned w))\<close>
   for w :: \<open>'b::len word\<close>
-  by (rule bit_eqI) (auto simp add: bit_unsigned_iff bit_take_bit_iff bit_drop_bit_eq Bit_Operations.bit_drop_bit_eq dest: bit_imp_le_length)
+  by (rule bit_eqI) (auto simp add: bit_unsigned_iff bit_take_bit_iff bit_drop_bit_eq Bit_Operations.bit_drop_bit_eq possible_bit_def dest: bit_imp_le_length)
 
 end
 
 lemma ucast_drop_bit_eq:
   \<open>ucast (drop_bit n w) = drop_bit n (ucast w :: 'b::len word)\<close>
   if \<open>LENGTH('a) \<le> LENGTH('b)\<close> for w :: \<open>'a::len word\<close>
   by (rule bit_word_eqI) (use that in \<open>auto simp add: bit_unsigned_iff bit_drop_bit_eq dest: bit_imp_le_length\<close>)
 
 context semiring_bit_operations
 begin
 
 context
   includes bit_operations_syntax
 begin
 
 lemma unsigned_and_eq:
   \<open>unsigned (v AND w) = unsigned v AND unsigned w\<close>
   for v w :: \<open>'b::len word\<close>
-  by (rule bit_eqI) (simp add: bit_unsigned_iff bit_and_iff Bit_Operations.bit_and_iff)
+  by (simp add: bit_eq_iff bit_simps)
 
 lemma unsigned_or_eq:
   \<open>unsigned (v OR w) = unsigned v OR unsigned w\<close>
   for v w :: \<open>'b::len word\<close>
-  by (rule bit_eqI) (simp add: bit_unsigned_iff bit_or_iff Bit_Operations.bit_or_iff)
+  by (simp add: bit_eq_iff bit_simps)
 
 lemma unsigned_xor_eq:
   \<open>unsigned (v XOR w) = unsigned v XOR unsigned w\<close>
   for v w :: \<open>'b::len word\<close>
-  by (rule bit_eqI) (simp add: bit_unsigned_iff bit_xor_iff Bit_Operations.bit_xor_iff)
+  by (simp add: bit_eq_iff bit_simps)
 
 end
 
 end
 
 context ring_bit_operations
 begin
 
 context
   includes bit_operations_syntax
 begin
 
 lemma unsigned_not_eq:
   \<open>unsigned (NOT w) = take_bit LENGTH('b) (NOT (unsigned w))\<close>
   for w :: \<open>'b::len word\<close>
-  by (rule bit_eqI)
-    (simp add: bit_unsigned_iff bit_take_bit_iff bit_not_iff Bit_Operations.bit_not_iff not_le)
+  by (simp add: bit_eq_iff bit_simps)
 
 end
 
 end
 
 context unique_euclidean_semiring_numeral
 begin
 
 lemma unsigned_greater_eq [simp]:
   \<open>0 \<le> unsigned w\<close> for w :: \<open>'b::len word\<close>
   by (transfer fixing: less_eq) simp
 
 lemma unsigned_less [simp]:
   \<open>unsigned w < 2 ^ LENGTH('b)\<close> for w :: \<open>'b::len word\<close>
   by (transfer fixing: less) simp
 
 end
 
 context linordered_semidom
 begin
 
 lemma word_less_eq_iff_unsigned:
   "a \<le> b \<longleftrightarrow> unsigned a \<le> unsigned b"
   by (transfer fixing: less_eq) (simp add: nat_le_eq_zle)
 
 lemma word_less_iff_unsigned:
   "a < b \<longleftrightarrow> unsigned a < unsigned b"
   by (transfer fixing: less) (auto dest: preorder_class.le_less_trans [OF take_bit_nonnegative])
 
 end
 
 
 subsubsection \<open>Generic signed conversion\<close>
 
 context ring_bit_operations
 begin
 
 lemma bit_signed_iff [bit_simps]:
-  \<open>bit (signed w) n \<longleftrightarrow> 2 ^ n \<noteq> 0 \<and> bit w (min (LENGTH('b) - Suc 0) n)\<close>
+  \<open>bit (signed w) n \<longleftrightarrow> possible_bit TYPE('a) n \<and> bit w (min (LENGTH('b) - Suc 0) n)\<close>
   for w :: \<open>'b::len word\<close>
   by (transfer fixing: bit)
     (auto simp add: bit_of_int_iff Bit_Operations.bit_signed_take_bit_iff min_def)
 
 lemma signed_push_bit_eq:
   \<open>signed (push_bit n w) = signed_take_bit (LENGTH('b) - Suc 0) (push_bit n (signed w :: 'a))\<close>
   for w :: \<open>'b::len word\<close>
-proof (rule bit_eqI)
-  fix m
-  assume \<open>2 ^ m \<noteq> 0\<close>
-  define q where \<open>q = LENGTH('b) - Suc 0\<close>
-  then have *: \<open>LENGTH('b) = Suc q\<close>
-    by simp
-  show \<open>bit (signed (push_bit n w)) m \<longleftrightarrow>
-    bit (signed_take_bit (LENGTH('b) - Suc 0) (push_bit n (signed w :: 'a))) m\<close>
-  proof (cases \<open>q \<le> m\<close>)
-    case True
-    moreover define r where \<open>r = m - q\<close>
-    ultimately have \<open>m = q + r\<close>
-      by simp
-    moreover from \<open>m = q + r\<close> \<open>2 ^ m \<noteq> 0\<close> have \<open>2 ^ q \<noteq> 0\<close> \<open>2 ^ r \<noteq> 0\<close>
-      using exp_add_not_zero_imp_left [of q r] exp_add_not_zero_imp_right [of q r]
-      by simp_all
-    moreover from \<open>2 ^ q \<noteq> 0\<close> have \<open>2 ^ (q - n) \<noteq> 0\<close>
-      by (rule exp_not_zero_imp_exp_diff_not_zero)
-    ultimately show ?thesis
-      by (auto simp add: bit_signed_iff bit_signed_take_bit_iff bit_push_bit_iff Bit_Operations.bit_push_bit_iff
-        min_def * le_diff_conv2)
-  next
-    case False
-    then show ?thesis
-      using exp_not_zero_imp_exp_diff_not_zero [of m n]
-      by (auto simp add: bit_signed_iff bit_signed_take_bit_iff bit_push_bit_iff Bit_Operations.bit_push_bit_iff
-        min_def not_le not_less * le_diff_conv2 less_diff_conv2 Bit_Operations.exp_eq_0_imp_not_bit exp_eq_0_imp_not_bit)
-  qed
-qed
+  apply (simp add: bit_eq_iff bit_simps possible_bit_min possible_bit_less_imp min_less_iff_disj)
+  apply (cases n, simp_all add: min_def)
+  done
 
 lemma signed_take_bit_eq:
   \<open>signed (take_bit n w) = (if n < LENGTH('b) then take_bit n (signed w) else signed w)\<close>
   for w :: \<open>'b::len word\<close>
   by (transfer fixing: take_bit; cases \<open>LENGTH('b)\<close>)
     (auto simp add: Bit_Operations.signed_take_bit_take_bit Bit_Operations.take_bit_signed_take_bit take_bit_of_int min_def less_Suc_eq)
 
 lemma signed_not_eq:
   \<open>signed (NOT w) = signed_take_bit LENGTH('b) (NOT (signed w))\<close>
   for w :: \<open>'b::len word\<close>
-proof (rule bit_eqI)
-  fix n
-  assume \<open>2 ^ n \<noteq> 0\<close>
-  define q where \<open>q = LENGTH('b) - Suc 0\<close>
-  then have *: \<open>LENGTH('b) = Suc q\<close>
-    by simp
-  show \<open>bit (signed (NOT w)) n \<longleftrightarrow>
-    bit (signed_take_bit LENGTH('b) (NOT (signed w))) n\<close>
-  proof (cases \<open>q < n\<close>)
-    case True
-    moreover define r where \<open>r = n - Suc q\<close>
-    ultimately have \<open>n = r + Suc q\<close>
-      by simp
-    moreover from \<open>2 ^ n \<noteq> 0\<close> \<open>n = r + Suc q\<close>
-      have \<open>2 ^ Suc q \<noteq> 0\<close>
-      using exp_add_not_zero_imp_right by blast 
-    ultimately show ?thesis
-      by (simp add: * bit_signed_iff bit_not_iff bit_signed_take_bit_iff Bit_Operations.bit_not_iff min_def)
-  next
-    case False
-    then show ?thesis
-      by (auto simp add: * bit_signed_iff bit_not_iff bit_signed_take_bit_iff Bit_Operations.bit_not_iff min_def)
-  qed
-qed
+  by (simp add: bit_eq_iff bit_simps possible_bit_min possible_bit_less_imp min_less_iff_disj)
+    (auto simp: min_def)
 
 context
   includes bit_operations_syntax
 begin
 
 lemma signed_and_eq:
   \<open>signed (v AND w) = signed v AND signed w\<close>
   for v w :: \<open>'b::len word\<close>
   by (rule bit_eqI) (simp add: bit_signed_iff bit_and_iff Bit_Operations.bit_and_iff)
 
 lemma signed_or_eq:
   \<open>signed (v OR w) = signed v OR signed w\<close>
   for v w :: \<open>'b::len word\<close>
   by (rule bit_eqI) (simp add: bit_signed_iff bit_or_iff Bit_Operations.bit_or_iff)
 
 lemma signed_xor_eq:
   \<open>signed (v XOR w) = signed v XOR signed w\<close>
   for v w :: \<open>'b::len word\<close>
   by (rule bit_eqI) (simp add: bit_signed_iff bit_xor_iff Bit_Operations.bit_xor_iff)
 
 end
 
 end
 
 
 subsubsection \<open>More\<close>
 
 lemma sint_greater_eq:
   \<open>- (2 ^ (LENGTH('a) - Suc 0)) \<le> sint w\<close> for w :: \<open>'a::len word\<close>
 proof (cases \<open>bit w (LENGTH('a) - Suc 0)\<close>)
   case True
   then show ?thesis
     by transfer (simp add: signed_take_bit_eq_if_negative minus_exp_eq_not_mask or_greater_eq ac_simps)
 next
   have *: \<open>- (2 ^ (LENGTH('a) - Suc 0)) \<le> (0::int)\<close>
     by simp
   case False
   then show ?thesis
     by transfer (auto simp add: signed_take_bit_eq intro: order_trans *)
 qed
 
 lemma sint_less:
   \<open>sint w < 2 ^ (LENGTH('a) - Suc 0)\<close> for w :: \<open>'a::len word\<close>
   by (cases \<open>bit w (LENGTH('a) - Suc 0)\<close>; transfer)
     (simp_all add: signed_take_bit_eq signed_take_bit_def not_eq_complement mask_eq_exp_minus_1 OR_upper)
 
 lemma unat_div_distrib:
   \<open>unat (v div w) = unat v div unat w\<close>
 proof transfer
   fix k l
   have \<open>nat (take_bit LENGTH('a) k) div nat (take_bit LENGTH('a) l) \<le> nat (take_bit LENGTH('a) k)\<close>
     by (rule div_le_dividend)
   also have \<open>nat (take_bit LENGTH('a) k) < 2 ^ LENGTH('a)\<close>
     by (simp add: nat_less_iff)
   finally show \<open>(nat \<circ> take_bit LENGTH('a)) (take_bit LENGTH('a) k div take_bit LENGTH('a) l) =
     (nat \<circ> take_bit LENGTH('a)) k div (nat \<circ> take_bit LENGTH('a)) l\<close>
     by (simp add: nat_take_bit_eq div_int_pos_iff nat_div_distrib take_bit_nat_eq_self_iff)
 qed
 
 lemma unat_mod_distrib:
   \<open>unat (v mod w) = unat v mod unat w\<close>
 proof transfer
   fix k l
   have \<open>nat (take_bit LENGTH('a) k) mod nat (take_bit LENGTH('a) l) \<le> nat (take_bit LENGTH('a) k)\<close>
     by (rule mod_less_eq_dividend)
   also have \<open>nat (take_bit LENGTH('a) k) < 2 ^ LENGTH('a)\<close>
     by (simp add: nat_less_iff)
   finally show \<open>(nat \<circ> take_bit LENGTH('a)) (take_bit LENGTH('a) k mod take_bit LENGTH('a) l) =
     (nat \<circ> take_bit LENGTH('a)) k mod (nat \<circ> take_bit LENGTH('a)) l\<close>
     by (simp add: nat_take_bit_eq mod_int_pos_iff less_le nat_mod_distrib take_bit_nat_eq_self_iff)
 qed
 
 lemma uint_div_distrib:
   \<open>uint (v div w) = uint v div uint w\<close>
 proof -
   have \<open>int (unat (v div w)) = int (unat v div unat w)\<close>
     by (simp add: unat_div_distrib)
   then show ?thesis
     by (simp add: of_nat_div)
 qed
 
 lemma unat_drop_bit_eq:
   \<open>unat (drop_bit n w) = drop_bit n (unat w)\<close>
   by (rule bit_eqI) (simp add: bit_unsigned_iff bit_drop_bit_eq)
 
 lemma uint_mod_distrib:
   \<open>uint (v mod w) = uint v mod uint w\<close>
 proof -
   have \<open>int (unat (v mod w)) = int (unat v mod unat w)\<close>
     by (simp add: unat_mod_distrib)
   then show ?thesis
     by (simp add: of_nat_mod)
 qed
 
 context semiring_bit_operations
 begin
 
 lemma unsigned_ucast_eq:
   \<open>unsigned (ucast w :: 'c::len word) = take_bit LENGTH('c) (unsigned w)\<close>
   for w :: \<open>'b::len word\<close>
   by (rule bit_eqI) (simp add: bit_unsigned_iff Word.bit_unsigned_iff bit_take_bit_iff not_le)
 
 end
 
 context ring_bit_operations
 begin
 
 lemma signed_ucast_eq:
   \<open>signed (ucast w :: 'c::len word) = signed_take_bit (LENGTH('c) - Suc 0) (unsigned w)\<close>
   for w :: \<open>'b::len word\<close>
-proof (rule bit_eqI)
-  fix n
-  assume \<open>2 ^ n \<noteq> 0\<close>
-  then have \<open>2 ^ (min (LENGTH('c) - Suc 0) n) \<noteq> 0\<close>
-    by (simp add: min_def)
-      (metis (mono_tags) diff_diff_cancel exp_not_zero_imp_exp_diff_not_zero)
-  then show \<open>bit (signed (ucast w :: 'c::len word)) n \<longleftrightarrow> bit (signed_take_bit (LENGTH('c) - Suc 0) (unsigned w)) n\<close>
-    by (simp add: bit_signed_iff bit_unsigned_iff Word.bit_unsigned_iff bit_signed_take_bit_iff not_le)
-qed
+  by (simp add: bit_eq_iff bit_simps possible_bit_min min_less_iff_disj)
 
 lemma signed_scast_eq:
   \<open>signed (scast w :: 'c::len word) = signed_take_bit (LENGTH('c) - Suc 0) (signed w)\<close>
   for w :: \<open>'b::len word\<close>
-proof (rule bit_eqI)
-  fix n
-  assume \<open>2 ^ n \<noteq> 0\<close>
-  then have \<open>2 ^ (min (LENGTH('c) - Suc 0) n) \<noteq> 0\<close>
-    by (simp add: min_def)
-      (metis (mono_tags) diff_diff_cancel exp_not_zero_imp_exp_diff_not_zero)
-  then show \<open>bit (signed (scast w :: 'c::len word)) n \<longleftrightarrow> bit (signed_take_bit (LENGTH('c) - Suc 0) (signed w)) n\<close>
-    by (simp add: bit_signed_iff bit_unsigned_iff Word.bit_signed_iff bit_signed_take_bit_iff not_le)
-qed
+  by (simp add: bit_eq_iff bit_simps possible_bit_min min_less_iff_disj)
 
 end
 
 lemma uint_nonnegative: "0 \<le> uint w"
   by (fact unsigned_greater_eq)
 
 lemma uint_bounded: "uint w < 2 ^ LENGTH('a)"
   for w :: "'a::len word"
   by (fact unsigned_less)
 
 lemma uint_idem: "uint w mod 2 ^ LENGTH('a) = uint w"
   for w :: "'a::len word"
   by transfer (simp add: take_bit_eq_mod)
 
 lemma word_uint_eqI: "uint a = uint b \<Longrightarrow> a = b"
   by (fact unsigned_word_eqI)
 
 lemma word_uint_eq_iff: "a = b \<longleftrightarrow> uint a = uint b"
   by (fact word_eq_iff_unsigned)
 
 lemma uint_word_of_int_eq:
   \<open>uint (word_of_int k :: 'a::len word) = take_bit LENGTH('a) k\<close>
   by transfer rule
 
 lemma uint_word_of_int: "uint (word_of_int k :: 'a::len word) = k mod 2 ^ LENGTH('a)"
   by (simp add: uint_word_of_int_eq take_bit_eq_mod)
   
 lemma word_of_int_uint: "word_of_int (uint w) = w"
   by transfer simp
 
 lemma word_div_def [code]:
   "a div b = word_of_int (uint a div uint b)"
   by transfer rule
 
 lemma word_mod_def [code]:
   "a mod b = word_of_int (uint a mod uint b)"
   by transfer rule
 
 lemma split_word_all: "(\<And>x::'a::len word. PROP P x) \<equiv> (\<And>x. PROP P (word_of_int x))"
 proof
   fix x :: "'a word"
   assume "\<And>x. PROP P (word_of_int x)"
   then have "PROP P (word_of_int (uint x))" .
   then show "PROP P x"
     by (simp only: word_of_int_uint)
 qed
 
 lemma sint_uint:
   \<open>sint w = signed_take_bit (LENGTH('a) - Suc 0) (uint w)\<close>
   for w :: \<open>'a::len word\<close>
   by (cases \<open>LENGTH('a)\<close>; transfer) (simp_all add: signed_take_bit_take_bit)
 
 lemma unat_eq_nat_uint:
   \<open>unat w = nat (uint w)\<close>
   by simp
 
 lemma ucast_eq:
   \<open>ucast w = word_of_int (uint w)\<close>
   by transfer simp
 
 lemma scast_eq:
   \<open>scast w = word_of_int (sint w)\<close>
   by transfer simp
 
 lemma uint_0_eq:
   \<open>uint 0 = 0\<close>
   by (fact unsigned_0)
 
 lemma uint_1_eq:
   \<open>uint 1 = 1\<close>
   by (fact unsigned_1)
 
 lemma word_m1_wi: "- 1 = word_of_int (- 1)"
   by simp
 
 lemma uint_0_iff: "uint x = 0 \<longleftrightarrow> x = 0"
   by (auto simp add: unsigned_word_eqI)
 
 lemma unat_0_iff: "unat x = 0 \<longleftrightarrow> x = 0"
   by (auto simp add: unsigned_word_eqI)
 
 lemma unat_0: "unat 0 = 0"
   by (fact unsigned_0)
 
 lemma unat_gt_0: "0 < unat x \<longleftrightarrow> x \<noteq> 0"
   by (auto simp: unat_0_iff [symmetric])
 
 lemma ucast_0: "ucast 0 = 0"
   by (fact unsigned_0)
 
 lemma sint_0: "sint 0 = 0"
   by (fact signed_0)
 
 lemma scast_0: "scast 0 = 0"
   by (fact signed_0)
 
 lemma sint_n1: "sint (- 1) = - 1"
   by (fact signed_minus_1)
 
 lemma scast_n1: "scast (- 1) = - 1"
   by (fact signed_minus_1)
 
 lemma uint_1: "uint (1::'a::len word) = 1"
   by (fact uint_1_eq)
 
 lemma unat_1: "unat (1::'a::len word) = 1"
   by (fact unsigned_1)
 
 lemma ucast_1: "ucast (1::'a::len word) = 1"
   by (fact unsigned_1)
 
 instantiation word :: (len) size
 begin
 
 lift_definition size_word :: \<open>'a word \<Rightarrow> nat\<close>
   is \<open>\<lambda>_. LENGTH('a)\<close> ..
 
 instance ..
 
 end
 
 lemma word_size [code]:
   \<open>size w = LENGTH('a)\<close> for w :: \<open>'a::len word\<close>
   by (fact size_word.rep_eq)
 
 lemma word_size_gt_0 [iff]: "0 < size w"
   for w :: "'a::len word"
   by (simp add: word_size)
 
 lemmas lens_gt_0 = word_size_gt_0 len_gt_0
 
 lemma lens_not_0 [iff]:
   \<open>size w \<noteq> 0\<close> for  w :: \<open>'a::len word\<close>
   by auto
 
 lift_definition source_size :: \<open>('a::len word \<Rightarrow> 'b) \<Rightarrow> nat\<close>
   is \<open>\<lambda>_. LENGTH('a)\<close> .
 
 lift_definition target_size :: \<open>('a \<Rightarrow> 'b::len word) \<Rightarrow> nat\<close>
   is \<open>\<lambda>_. LENGTH('b)\<close> ..
 
 lift_definition is_up :: \<open>('a::len word \<Rightarrow> 'b::len word) \<Rightarrow> bool\<close>
   is \<open>\<lambda>_. LENGTH('a) \<le> LENGTH('b)\<close> ..
 
 lift_definition is_down :: \<open>('a::len word \<Rightarrow> 'b::len word) \<Rightarrow> bool\<close>
   is \<open>\<lambda>_. LENGTH('a) \<ge> LENGTH('b)\<close> ..
 
 lemma is_up_eq:
   \<open>is_up f \<longleftrightarrow> source_size f \<le> target_size f\<close>
   for f :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   by (simp add: source_size.rep_eq target_size.rep_eq is_up.rep_eq)
 
 lemma is_down_eq:
   \<open>is_down f \<longleftrightarrow> target_size f \<le> source_size f\<close>
   for f :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   by (simp add: source_size.rep_eq target_size.rep_eq is_down.rep_eq)
 
 lift_definition word_int_case :: \<open>(int \<Rightarrow> 'b) \<Rightarrow> 'a::len word \<Rightarrow> 'b\<close>
   is \<open>\<lambda>f. f \<circ> take_bit LENGTH('a)\<close> by simp
 
 lemma word_int_case_eq_uint [code]:
   \<open>word_int_case f w = f (uint w)\<close>
   by transfer simp
 
 translations
   "case x of XCONST of_int y \<Rightarrow> b" \<rightleftharpoons> "CONST word_int_case (\<lambda>y. b) x"
   "case x of (XCONST of_int :: 'a) y \<Rightarrow> b" \<rightharpoonup> "CONST word_int_case (\<lambda>y. b) x"
 
 
 subsection \<open>Arithmetic operations\<close>
 
 text \<open>Legacy theorems:\<close>
 
 lemma word_add_def [code]:
   "a + b = word_of_int (uint a + uint b)"
   by transfer (simp add: take_bit_add)
 
 lemma word_sub_wi [code]:
   "a - b = word_of_int (uint a - uint b)"
   by transfer (simp add: take_bit_diff)
 
 lemma word_mult_def [code]:
   "a * b = word_of_int (uint a * uint b)"
   by transfer (simp add: take_bit_eq_mod mod_simps)
 
 lemma word_minus_def [code]:
   "- a = word_of_int (- uint a)"
   by transfer (simp add: take_bit_minus)
 
 lemma word_0_wi:
   "0 = word_of_int 0"
   by transfer simp
 
 lemma word_1_wi:
   "1 = word_of_int 1"
   by transfer simp
 
 lift_definition word_succ :: "'a::len word \<Rightarrow> 'a word" is "\<lambda>x. x + 1"
   by (auto simp add: take_bit_eq_mod intro: mod_add_cong)
 
 lift_definition word_pred :: "'a::len word \<Rightarrow> 'a word" is "\<lambda>x. x - 1"
   by (auto simp add: take_bit_eq_mod intro: mod_diff_cong)
 
 lemma word_succ_alt [code]:
   "word_succ a = word_of_int (uint a + 1)"
   by transfer (simp add: take_bit_eq_mod mod_simps)
 
 lemma word_pred_alt [code]:
   "word_pred a = word_of_int (uint a - 1)"
   by transfer (simp add: take_bit_eq_mod mod_simps)
 
 lemmas word_arith_wis = 
   word_add_def word_sub_wi word_mult_def
   word_minus_def word_succ_alt word_pred_alt
   word_0_wi word_1_wi
 
 lemma wi_homs:
   shows wi_hom_add: "word_of_int a + word_of_int b = word_of_int (a + b)"
     and wi_hom_sub: "word_of_int a - word_of_int b = word_of_int (a - b)"
     and wi_hom_mult: "word_of_int a * word_of_int b = word_of_int (a * b)"
     and wi_hom_neg: "- word_of_int a = word_of_int (- a)"
     and wi_hom_succ: "word_succ (word_of_int a) = word_of_int (a + 1)"
     and wi_hom_pred: "word_pred (word_of_int a) = word_of_int (a - 1)"
   by (transfer, simp)+
 
 lemmas wi_hom_syms = wi_homs [symmetric]
 
 lemmas word_of_int_homs = wi_homs word_0_wi word_1_wi
 
 lemmas word_of_int_hom_syms = word_of_int_homs [symmetric]
 
 lemma double_eq_zero_iff:
   \<open>2 * a = 0 \<longleftrightarrow> a = 0 \<or> a = 2 ^ (LENGTH('a) - Suc 0)\<close>
   for a :: \<open>'a::len word\<close>
 proof -
   define n where \<open>n = LENGTH('a) - Suc 0\<close>
   then have *: \<open>LENGTH('a) = Suc n\<close>
     by simp
   have \<open>a = 0\<close> if \<open>2 * a = 0\<close> and \<open>a \<noteq> 2 ^ (LENGTH('a) - Suc 0)\<close>
     using that by transfer
       (auto simp add: take_bit_eq_0_iff take_bit_eq_mod *)
   moreover have \<open>2 ^ LENGTH('a) = (0 :: 'a word)\<close>
     by transfer simp
   then have \<open>2 * 2 ^ (LENGTH('a) - Suc 0) = (0 :: 'a word)\<close>
     by (simp add: *)
   ultimately show ?thesis
     by auto
 qed
 
 
 subsection \<open>Ordering\<close>
 
 lift_definition word_sle :: \<open>'a::len word \<Rightarrow> 'a word \<Rightarrow> bool\<close>
   is \<open>\<lambda>k l. signed_take_bit (LENGTH('a) - Suc 0) k \<le> signed_take_bit (LENGTH('a) - Suc 0) l\<close>
   by (simp flip: signed_take_bit_decr_length_iff)
 
 lift_definition word_sless :: \<open>'a::len word \<Rightarrow> 'a word \<Rightarrow> bool\<close>
   is \<open>\<lambda>k l. signed_take_bit (LENGTH('a) - Suc 0) k < signed_take_bit (LENGTH('a) - Suc 0) l\<close>
   by (simp flip: signed_take_bit_decr_length_iff)
 
 notation
   word_sle    ("'(\<le>s')") and
   word_sle    ("(_/ \<le>s _)"  [51, 51] 50) and
   word_sless  ("'(<s')") and
   word_sless  ("(_/ <s _)"  [51, 51] 50)
 
 notation (input)
   word_sle    ("(_/ <=s _)"  [51, 51] 50)
 
 lemma word_sle_eq [code]:
   \<open>a <=s b \<longleftrightarrow> sint a \<le> sint b\<close>
   by transfer simp
 
 lemma [code]:
   \<open>a <s b \<longleftrightarrow> sint a < sint b\<close>
   by transfer simp
 
 lemma signed_ordering: \<open>ordering word_sle word_sless\<close>
   apply (standard; transfer)
   using signed_take_bit_decr_length_iff by force+
 
 lemma signed_linorder: \<open>class.linorder word_sle word_sless\<close>
   by (standard; transfer) (auto simp add: signed_take_bit_decr_length_iff)
 
 interpretation signed: linorder word_sle word_sless
   by (fact signed_linorder)
 
 lemma word_sless_eq:
   \<open>x <s y \<longleftrightarrow> x <=s y \<and> x \<noteq> y\<close>
   by (fact signed.less_le)
 
 lemma word_less_alt: "a < b \<longleftrightarrow> uint a < uint b"
   by (fact word_less_def)
 
 lemma word_zero_le [simp]: "0 \<le> y"
   for y :: "'a::len word"
   by (fact word_coorder.extremum)
 
 lemma word_m1_ge [simp] : "word_pred 0 \<ge> y" (* FIXME: delete *)
   by transfer (simp add: take_bit_minus_one_eq_mask mask_eq_exp_minus_1 )
 
 lemma word_n1_ge [simp]: "y \<le> -1"
   for y :: "'a::len word"
   by (fact word_order.extremum)
 
 lemmas word_not_simps [simp] =
   word_zero_le [THEN leD] word_m1_ge [THEN leD] word_n1_ge [THEN leD]
 
 lemma word_gt_0: "0 < y \<longleftrightarrow> 0 \<noteq> y"
   for y :: "'a::len word"
   by (simp add: less_le)
 
 lemmas word_gt_0_no [simp] = word_gt_0 [of "numeral y"] for y
 
 lemma word_sless_alt: "a <s b \<longleftrightarrow> sint a < sint b"
   by transfer simp
 
 lemma word_le_nat_alt: "a \<le> b \<longleftrightarrow> unat a \<le> unat b"
   by transfer (simp add: nat_le_eq_zle)
 
 lemma word_less_nat_alt: "a < b \<longleftrightarrow> unat a < unat b"
   by transfer (auto simp add: less_le [of 0])
 
 lemmas unat_mono = word_less_nat_alt [THEN iffD1]
 
 instance word :: (len) wellorder
 proof
   fix P :: "'a word \<Rightarrow> bool" and a
   assume *: "(\<And>b. (\<And>a. a < b \<Longrightarrow> P a) \<Longrightarrow> P b)"
   have "wf (measure unat)" ..
   moreover have "{(a, b :: ('a::len) word). a < b} \<subseteq> measure unat"
     by (auto simp add: word_less_nat_alt)
   ultimately have "wf {(a, b :: ('a::len) word). a < b}"
     by (rule wf_subset)
   then show "P a" using *
     by induction blast
 qed
 
 lemma wi_less:
   "(word_of_int n < (word_of_int m :: 'a::len word)) =
     (n mod 2 ^ LENGTH('a) < m mod 2 ^ LENGTH('a))"
   by transfer (simp add: take_bit_eq_mod)
 
 lemma wi_le:
   "(word_of_int n \<le> (word_of_int m :: 'a::len word)) =
     (n mod 2 ^ LENGTH('a) \<le> m mod 2 ^ LENGTH('a))"
   by transfer (simp add: take_bit_eq_mod)
 
 
 subsection \<open>Bit-wise operations\<close>
 
 context
   includes bit_operations_syntax
 begin
 
 lemma uint_take_bit_eq:
   \<open>uint (take_bit n w) = take_bit n (uint w)\<close>
   by transfer (simp add: ac_simps)
 
 lemma take_bit_word_eq_self:
   \<open>take_bit n w = w\<close> if \<open>LENGTH('a) \<le> n\<close> for w :: \<open>'a::len word\<close>
   using that by transfer simp
 
 lemma take_bit_length_eq [simp]:
   \<open>take_bit LENGTH('a) w = w\<close> for w :: \<open>'a::len word\<close>
   by (rule take_bit_word_eq_self) simp
 
 lemma bit_word_of_int_iff:
   \<open>bit (word_of_int k :: 'a::len word) n \<longleftrightarrow> n < LENGTH('a) \<and> bit k n\<close>
   by transfer rule
 
 lemma bit_uint_iff:
   \<open>bit (uint w) n \<longleftrightarrow> n < LENGTH('a) \<and> bit w n\<close>
     for w :: \<open>'a::len word\<close>
   by transfer (simp add: bit_take_bit_iff)
 
 lemma bit_sint_iff:
   \<open>bit (sint w) n \<longleftrightarrow> n \<ge> LENGTH('a) \<and> bit w (LENGTH('a) - 1) \<or> bit w n\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (auto simp add: bit_signed_take_bit_iff min_def le_less not_less)
 
 lemma bit_word_ucast_iff:
   \<open>bit (ucast w :: 'b::len word) n \<longleftrightarrow> n < LENGTH('a) \<and> n < LENGTH('b) \<and> bit w n\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (simp add: bit_take_bit_iff ac_simps)
 
 lemma bit_word_scast_iff:
   \<open>bit (scast w :: 'b::len word) n \<longleftrightarrow>
     n < LENGTH('b) \<and> (bit w n \<or> LENGTH('a) \<le> n \<and> bit w (LENGTH('a) - Suc 0))\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (auto simp add: bit_signed_take_bit_iff le_less min_def)
 
 lemma bit_word_iff_drop_bit_and [code]:
   \<open>bit a n \<longleftrightarrow> drop_bit n a AND 1 = 1\<close> for a :: \<open>'a::len word\<close>
   by (simp add: bit_iff_odd_drop_bit odd_iff_mod_2_eq_one and_one_eq)
 
 lemma
   word_not_def: "NOT (a::'a::len word) = word_of_int (NOT (uint a))"
     and word_and_def: "(a::'a word) AND b = word_of_int (uint a AND uint b)"
     and word_or_def: "(a::'a word) OR b = word_of_int (uint a OR uint b)"
     and word_xor_def: "(a::'a word) XOR b = word_of_int (uint a XOR uint b)"
   by (transfer, simp add: take_bit_not_take_bit)+
 
 definition even_word :: \<open>'a::len word \<Rightarrow> bool\<close>
   where [code_abbrev]: \<open>even_word = even\<close>
 
 lemma even_word_iff [code]:
   \<open>even_word a \<longleftrightarrow> a AND 1 = 0\<close>
   by (simp add: and_one_eq even_iff_mod_2_eq_zero even_word_def)
 
 lemma map_bit_range_eq_if_take_bit_eq:
   \<open>map (bit k) [0..<n] = map (bit l) [0..<n]\<close>
   if \<open>take_bit n k = take_bit n l\<close> for k l :: int
 using that proof (induction n arbitrary: k l)
   case 0
   then show ?case
     by simp
 next
   case (Suc n)
   from Suc.prems have \<open>take_bit n (k div 2) = take_bit n (l div 2)\<close>
     by (simp add: take_bit_Suc)
   then have \<open>map (bit (k div 2)) [0..<n] = map (bit (l div 2)) [0..<n]\<close>
     by (rule Suc.IH)
   moreover have \<open>bit (r div 2) = bit r \<circ> Suc\<close> for r :: int
     by (simp add: fun_eq_iff bit_Suc)
   moreover from Suc.prems have \<open>even k \<longleftrightarrow> even l\<close>
     by (auto simp add: take_bit_Suc elim!: evenE oddE) arith+
   ultimately show ?case
     by (simp only: map_Suc_upt upt_conv_Cons flip: list.map_comp) simp
 qed
 
 lemma
   take_bit_word_Bit0_eq [simp]: \<open>take_bit (numeral n) (numeral (num.Bit0 m) :: 'a::len word)
     = 2 * take_bit (pred_numeral n) (numeral m)\<close> (is ?P)
   and take_bit_word_Bit1_eq [simp]: \<open>take_bit (numeral n) (numeral (num.Bit1 m) :: 'a::len word)
     = 1 + 2 * take_bit (pred_numeral n) (numeral m)\<close> (is ?Q)
   and take_bit_word_minus_Bit0_eq [simp]: \<open>take_bit (numeral n) (- numeral (num.Bit0 m) :: 'a::len word)
     = 2 * take_bit (pred_numeral n) (- numeral m)\<close> (is ?R)
   and take_bit_word_minus_Bit1_eq [simp]: \<open>take_bit (numeral n) (- numeral (num.Bit1 m) :: 'a::len word)
     = 1 + 2 * take_bit (pred_numeral n) (- numeral (Num.inc m))\<close> (is ?S)
 proof -
   define w :: \<open>'a::len word\<close>
     where \<open>w = numeral m\<close>
   moreover define q :: nat
     where \<open>q = pred_numeral n\<close>
   ultimately have num:
     \<open>numeral m = w\<close>
     \<open>numeral (num.Bit0 m) = 2 * w\<close>
     \<open>numeral (num.Bit1 m) = 1 + 2 * w\<close>
     \<open>numeral (Num.inc m) = 1 + w\<close>
     \<open>pred_numeral n = q\<close>
     \<open>numeral n = Suc q\<close>
     by (simp_all only: w_def q_def numeral_Bit0 [of m] numeral_Bit1 [of m] ac_simps
       numeral_inc numeral_eq_Suc flip: mult_2)
   have even: \<open>take_bit (Suc q) (2 * w) = 2 * take_bit q w\<close> for w :: \<open>'a::len word\<close>
     by (rule bit_word_eqI)
       (auto simp add: bit_take_bit_iff bit_double_iff)
   have odd: \<open>take_bit (Suc q) (1 + 2 * w) = 1 + 2 * take_bit q w\<close> for w :: \<open>'a::len word\<close>
     by (rule bit_eqI)
       (auto simp add: bit_take_bit_iff bit_double_iff even_bit_succ_iff)
   show ?P
     using even [of w] by (simp add: num)
   show ?Q
     using odd [of w] by (simp add: num)
   show ?R
     using even [of \<open>- w\<close>] by (simp add: num)
   show ?S
     using odd [of \<open>- (1 + w)\<close>] by (simp add: num)
 qed
 
 
 subsection \<open>More shift operations\<close>
 
 lift_definition signed_drop_bit :: \<open>nat \<Rightarrow> 'a word \<Rightarrow> 'a::len word\<close>
   is \<open>\<lambda>n. drop_bit n \<circ> signed_take_bit (LENGTH('a) - Suc 0)\<close>
   using signed_take_bit_decr_length_iff
   by (simp add: take_bit_drop_bit) force
 
 lemma bit_signed_drop_bit_iff [bit_simps]:
   \<open>bit (signed_drop_bit m w) n \<longleftrightarrow> bit w (if LENGTH('a) - m \<le> n \<and> n < LENGTH('a) then LENGTH('a) - 1 else m + n)\<close>
   for w :: \<open>'a::len word\<close>
   apply transfer
   apply (auto simp add: bit_drop_bit_eq bit_signed_take_bit_iff not_le min_def)
    apply (metis add.commute le_antisym less_diff_conv less_eq_decr_length_iff)
   apply (metis le_antisym less_eq_decr_length_iff)
   done
 
 lemma [code]:
   \<open>Word.the_int (signed_drop_bit n w) = take_bit LENGTH('a) (drop_bit n (Word.the_signed_int w))\<close>
   for w :: \<open>'a::len word\<close>
   by transfer simp
 
 lemma signed_drop_bit_of_0 [simp]:
   \<open>signed_drop_bit n 0 = 0\<close>
   by transfer simp
 
 lemma signed_drop_bit_of_minus_1 [simp]:
   \<open>signed_drop_bit n (- 1) = - 1\<close>
   by transfer simp
 
 lemma signed_drop_bit_signed_drop_bit [simp]:
   \<open>signed_drop_bit m (signed_drop_bit n w) = signed_drop_bit (m + n) w\<close>
   for w :: \<open>'a::len word\<close>
 proof (cases \<open>LENGTH('a)\<close>)
   case 0
   then show ?thesis
     using len_not_eq_0 by blast
 next
   case (Suc n)
   then show ?thesis
     by (force simp add: bit_signed_drop_bit_iff not_le less_diff_conv ac_simps intro!: bit_word_eqI)
 qed
 
 lemma signed_drop_bit_0 [simp]:
   \<open>signed_drop_bit 0 w = w\<close>
   by transfer (simp add: take_bit_signed_take_bit)
 
 lemma sint_signed_drop_bit_eq:
   \<open>sint (signed_drop_bit n w) = drop_bit n (sint w)\<close>
 proof (cases \<open>LENGTH('a) = 0 \<or> n=0\<close>)
   case False
   then show ?thesis
     apply simp
     apply (rule bit_eqI)
     by (auto simp add: bit_sint_iff bit_drop_bit_eq bit_signed_drop_bit_iff dest: bit_imp_le_length)
 qed auto
 
 
 subsection \<open>Rotation\<close>
 
 lift_definition word_rotr :: \<open>nat \<Rightarrow> 'a::len word \<Rightarrow> 'a::len word\<close>
   is \<open>\<lambda>n k. concat_bit (LENGTH('a) - n mod LENGTH('a))
     (drop_bit (n mod LENGTH('a)) (take_bit LENGTH('a) k))
     (take_bit (n mod LENGTH('a)) k)\<close>
   subgoal for n k l
     by (simp add: concat_bit_def nat_le_iff less_imp_le
       take_bit_tightened [of \<open>LENGTH('a)\<close> k l \<open>n mod LENGTH('a::len)\<close>])
   done
 
 lift_definition word_rotl :: \<open>nat \<Rightarrow> 'a::len word \<Rightarrow> 'a::len word\<close>
   is \<open>\<lambda>n k. concat_bit (n mod LENGTH('a))
     (drop_bit (LENGTH('a) - n mod LENGTH('a)) (take_bit LENGTH('a) k))
     (take_bit (LENGTH('a) - n mod LENGTH('a)) k)\<close>
   subgoal for n k l
     by (simp add: concat_bit_def nat_le_iff less_imp_le
       take_bit_tightened [of \<open>LENGTH('a)\<close> k l \<open>LENGTH('a) - n mod LENGTH('a::len)\<close>])
   done
 
 lift_definition word_roti :: \<open>int \<Rightarrow> 'a::len word \<Rightarrow> 'a::len word\<close>
   is \<open>\<lambda>r k. concat_bit (LENGTH('a) - nat (r mod int LENGTH('a)))
     (drop_bit (nat (r mod int LENGTH('a))) (take_bit LENGTH('a) k))
     (take_bit (nat (r mod int LENGTH('a))) k)\<close>
   subgoal for r k l
     by (simp add: concat_bit_def nat_le_iff less_imp_le
       take_bit_tightened [of \<open>LENGTH('a)\<close> k l \<open>nat (r mod int LENGTH('a::len))\<close>])
   done
 
 lemma word_rotl_eq_word_rotr [code]:
   \<open>word_rotl n = (word_rotr (LENGTH('a) - n mod LENGTH('a)) :: 'a::len word \<Rightarrow> 'a word)\<close>
   by (rule ext, cases \<open>n mod LENGTH('a) = 0\<close>; transfer) simp_all
 
 lemma word_roti_eq_word_rotr_word_rotl [code]:
   \<open>word_roti i w =
     (if i \<ge> 0 then word_rotr (nat i) w else word_rotl (nat (- i)) w)\<close>
 proof (cases \<open>i \<ge> 0\<close>)
   case True
   moreover define n where \<open>n = nat i\<close>
   ultimately have \<open>i = int n\<close>
     by simp
   moreover have \<open>word_roti (int n) = (word_rotr n :: _ \<Rightarrow> 'a word)\<close>
     by (rule ext, transfer) (simp add: nat_mod_distrib)
   ultimately show ?thesis
     by simp
 next
   case False
   moreover define n where \<open>n = nat (- i)\<close>
   ultimately have \<open>i = - int n\<close> \<open>n > 0\<close>
     by simp_all
   moreover have \<open>word_roti (- int n) = (word_rotl n :: _ \<Rightarrow> 'a word)\<close>
     by (rule ext, transfer)
       (simp add: zmod_zminus1_eq_if flip: of_nat_mod of_nat_diff)
   ultimately show ?thesis
     by simp
 qed
 
 lemma bit_word_rotr_iff [bit_simps]:
   \<open>bit (word_rotr m w) n \<longleftrightarrow>
     n < LENGTH('a) \<and> bit w ((n + m) mod LENGTH('a))\<close>
   for w :: \<open>'a::len word\<close>
 proof transfer
   fix k :: int and m n :: nat
   define q where \<open>q = m mod LENGTH('a)\<close>
   have \<open>q < LENGTH('a)\<close> 
     by (simp add: q_def)
   then have \<open>q \<le> LENGTH('a)\<close>
     by simp
   have \<open>m mod LENGTH('a) = q\<close>
     by (simp add: q_def)
   moreover have \<open>(n + m) mod LENGTH('a) = (n + q) mod LENGTH('a)\<close>
     by (subst mod_add_right_eq [symmetric]) (simp add: \<open>m mod LENGTH('a) = q\<close>)
   moreover have \<open>n < LENGTH('a) \<and>
     bit (concat_bit (LENGTH('a) - q) (drop_bit q (take_bit LENGTH('a) k)) (take_bit q k)) n \<longleftrightarrow>
     n < LENGTH('a) \<and> bit k ((n + q) mod LENGTH('a))\<close>
     using \<open>q < LENGTH('a)\<close>
     by (cases \<open>q + n \<ge> LENGTH('a)\<close>)
      (auto simp add: bit_concat_bit_iff bit_drop_bit_eq
         bit_take_bit_iff le_mod_geq ac_simps)
   ultimately show \<open>n < LENGTH('a) \<and>
     bit (concat_bit (LENGTH('a) - m mod LENGTH('a))
       (drop_bit (m mod LENGTH('a)) (take_bit LENGTH('a) k))
       (take_bit (m mod LENGTH('a)) k)) n
     \<longleftrightarrow> n < LENGTH('a) \<and>
       (n + m) mod LENGTH('a) < LENGTH('a) \<and>
       bit k ((n + m) mod LENGTH('a))\<close>
     by simp
 qed
 
 lemma bit_word_rotl_iff [bit_simps]:
   \<open>bit (word_rotl m w) n \<longleftrightarrow>
     n < LENGTH('a) \<and> bit w ((n + (LENGTH('a) - m mod LENGTH('a))) mod LENGTH('a))\<close>
   for w :: \<open>'a::len word\<close>
   by (simp add: word_rotl_eq_word_rotr bit_word_rotr_iff)
 
 lemma bit_word_roti_iff [bit_simps]:
   \<open>bit (word_roti k w) n \<longleftrightarrow>
     n < LENGTH('a) \<and> bit w (nat ((int n + k) mod int LENGTH('a)))\<close>
   for w :: \<open>'a::len word\<close>
 proof transfer
   fix k l :: int and n :: nat
   define m where \<open>m = nat (k mod int LENGTH('a))\<close>
   have \<open>m < LENGTH('a)\<close> 
     by (simp add: nat_less_iff m_def)
   then have \<open>m \<le> LENGTH('a)\<close>
     by simp
   have \<open>k mod int LENGTH('a) = int m\<close>
     by (simp add: nat_less_iff m_def)
   moreover have \<open>(int n + k) mod int LENGTH('a) = int ((n + m) mod LENGTH('a))\<close>
     by (subst mod_add_right_eq [symmetric]) (simp add: of_nat_mod \<open>k mod int LENGTH('a) = int m\<close>)
   moreover have \<open>n < LENGTH('a) \<and>
     bit (concat_bit (LENGTH('a) - m) (drop_bit m (take_bit LENGTH('a) l)) (take_bit m l)) n \<longleftrightarrow>
     n < LENGTH('a) \<and> bit l ((n + m) mod LENGTH('a))\<close>
     using \<open>m < LENGTH('a)\<close>
     by (cases \<open>m + n \<ge> LENGTH('a)\<close>)
      (auto simp add: bit_concat_bit_iff bit_drop_bit_eq
         bit_take_bit_iff nat_less_iff not_le not_less ac_simps
         le_diff_conv le_mod_geq)
   ultimately show \<open>n < LENGTH('a)
     \<and> bit (concat_bit (LENGTH('a) - nat (k mod int LENGTH('a)))
              (drop_bit (nat (k mod int LENGTH('a))) (take_bit LENGTH('a) l))
              (take_bit (nat (k mod int LENGTH('a))) l)) n \<longleftrightarrow>
        n < LENGTH('a) 
     \<and> nat ((int n + k) mod int LENGTH('a)) < LENGTH('a)
     \<and> bit l (nat ((int n + k) mod int LENGTH('a)))\<close>
     by simp
 qed
 
 lemma uint_word_rotr_eq:
   \<open>uint (word_rotr n w) = concat_bit (LENGTH('a) - n mod LENGTH('a))
     (drop_bit (n mod LENGTH('a)) (uint w))
     (uint (take_bit (n mod LENGTH('a)) w))\<close>
   for w :: \<open>'a::len word\<close>
   by transfer (simp add: take_bit_concat_bit_eq)
 
 lemma [code]:
   \<open>Word.the_int (word_rotr n w) = concat_bit (LENGTH('a) - n mod LENGTH('a))
     (drop_bit (n mod LENGTH('a)) (Word.the_int w))
     (Word.the_int (take_bit (n mod LENGTH('a)) w))\<close>
   for w :: \<open>'a::len word\<close>
   using uint_word_rotr_eq [of n w] by simp
 
     
 subsection \<open>Split and cat operations\<close>
 
 lift_definition word_cat :: \<open>'a::len word \<Rightarrow> 'b::len word \<Rightarrow> 'c::len word\<close>
   is \<open>\<lambda>k l. concat_bit LENGTH('b) l (take_bit LENGTH('a) k)\<close>
   by (simp add: bit_eq_iff bit_concat_bit_iff bit_take_bit_iff)
 
 lemma word_cat_eq:
   \<open>(word_cat v w :: 'c::len word) = push_bit LENGTH('b) (ucast v) + ucast w\<close>
   for v :: \<open>'a::len word\<close> and w :: \<open>'b::len word\<close>
   by transfer (simp add: concat_bit_eq ac_simps)
 
 lemma word_cat_eq' [code]:
   \<open>word_cat a b = word_of_int (concat_bit LENGTH('b) (uint b) (uint a))\<close>
   for a :: \<open>'a::len word\<close> and b :: \<open>'b::len word\<close>
   by transfer (simp add: concat_bit_take_bit_eq)
 
 lemma bit_word_cat_iff [bit_simps]:
   \<open>bit (word_cat v w :: 'c::len word) n \<longleftrightarrow> n < LENGTH('c) \<and> (if n < LENGTH('b) then bit w n else bit v (n - LENGTH('b)))\<close> 
   for v :: \<open>'a::len word\<close> and w :: \<open>'b::len word\<close>
   by transfer (simp add: bit_concat_bit_iff bit_take_bit_iff)
 
 definition word_split :: \<open>'a::len word \<Rightarrow> 'b::len word \<times> 'c::len word\<close>
   where \<open>word_split w =
     (ucast (drop_bit LENGTH('c) w) :: 'b::len word, ucast w :: 'c::len word)\<close>
 
 definition word_rcat :: \<open>'a::len word list \<Rightarrow> 'b::len word\<close>
   where \<open>word_rcat = word_of_int \<circ> horner_sum uint (2 ^ LENGTH('a)) \<circ> rev\<close>
 
 
 subsection \<open>More on conversions\<close>
 
 lemma int_word_sint:
   \<open>sint (word_of_int x :: 'a::len word) = (x + 2 ^ (LENGTH('a) - 1)) mod 2 ^ LENGTH('a) - 2 ^ (LENGTH('a) - 1)\<close>
   by transfer (simp flip: take_bit_eq_mod add: signed_take_bit_eq_take_bit_shift)
 
 lemma sint_sbintrunc': "sint (word_of_int bin :: 'a word) = signed_take_bit (LENGTH('a::len) - 1) bin"
   by simp
 
 lemma uint_sint: "uint w = take_bit LENGTH('a) (sint w)"
   for w :: "'a::len word"
   by transfer (simp add: take_bit_signed_take_bit)
 
 lemma bintr_uint: "LENGTH('a) \<le> n \<Longrightarrow> take_bit n (uint w) = uint w"
   for w :: "'a::len word"
   by transfer (simp add: min_def)
 
 lemma wi_bintr:
   "LENGTH('a::len) \<le> n \<Longrightarrow>
     word_of_int (take_bit n w) = (word_of_int w :: 'a word)"
   by transfer simp
 
 lemma word_numeral_alt: "numeral b = word_of_int (numeral b)"
   by (induct b, simp_all only: numeral.simps word_of_int_homs)
 
 declare word_numeral_alt [symmetric, code_abbrev]
 
 lemma word_neg_numeral_alt: "- numeral b = word_of_int (- numeral b)"
   by (simp only: word_numeral_alt wi_hom_neg)
 
 declare word_neg_numeral_alt [symmetric, code_abbrev]
 
 lemma uint_bintrunc [simp]:
   "uint (numeral bin :: 'a word) =
     take_bit (LENGTH('a::len)) (numeral bin)"
   by transfer rule
 
 lemma uint_bintrunc_neg [simp]:
   "uint (- numeral bin :: 'a word) = take_bit (LENGTH('a::len)) (- numeral bin)"
   by transfer rule
 
 lemma sint_sbintrunc [simp]:
   "sint (numeral bin :: 'a word) = signed_take_bit (LENGTH('a::len) - 1) (numeral bin)"
   by transfer simp
 
 lemma sint_sbintrunc_neg [simp]:
   "sint (- numeral bin :: 'a word) = signed_take_bit (LENGTH('a::len) - 1) (- numeral bin)"
   by transfer simp
 
 lemma unat_bintrunc [simp]:
   "unat (numeral bin :: 'a::len word) = nat (take_bit (LENGTH('a)) (numeral bin))"
   by transfer simp
 
 lemma unat_bintrunc_neg [simp]:
   "unat (- numeral bin :: 'a::len word) = nat (take_bit (LENGTH('a)) (- numeral bin))"
   by transfer simp
 
 lemma size_0_eq: "size w = 0 \<Longrightarrow> v = w"
   for v w :: "'a::len word"
   by transfer simp
 
 lemma uint_ge_0 [iff]: "0 \<le> uint x"
   by (fact unsigned_greater_eq)
 
 lemma uint_lt2p [iff]: "uint x < 2 ^ LENGTH('a)"
   for x :: "'a::len word"
   by (fact unsigned_less)
 
 lemma sint_ge: "- (2 ^ (LENGTH('a) - 1)) \<le> sint x"
   for x :: "'a::len word"
   using sint_greater_eq [of x] by simp
 
 lemma sint_lt: "sint x < 2 ^ (LENGTH('a) - 1)"
   for x :: "'a::len word"
   using sint_less [of x] by simp
 
 lemma uint_m2p_neg: "uint x - 2 ^ LENGTH('a) < 0"
   for x :: "'a::len word"
   by (simp only: diff_less_0_iff_less uint_lt2p)
 
 lemma uint_m2p_not_non_neg: "\<not> 0 \<le> uint x - 2 ^ LENGTH('a)"
   for x :: "'a::len word"
   by (simp only: not_le uint_m2p_neg)
 
 lemma lt2p_lem: "LENGTH('a) \<le> n \<Longrightarrow> uint w < 2 ^ n"
   for w :: "'a::len word"
   using uint_bounded [of w] by (rule less_le_trans) simp
 
 lemma uint_le_0_iff [simp]: "uint x \<le> 0 \<longleftrightarrow> uint x = 0"
   by (fact uint_ge_0 [THEN leD, THEN antisym_conv1])
 
 lemma uint_nat: "uint w = int (unat w)"
   by transfer simp
 
 lemma uint_numeral: "uint (numeral b :: 'a::len word) = numeral b mod 2 ^ LENGTH('a)"
   by (simp flip: take_bit_eq_mod add: of_nat_take_bit)
 
 lemma uint_neg_numeral: "uint (- numeral b :: 'a::len word) = - numeral b mod 2 ^ LENGTH('a)"
   by (simp flip: take_bit_eq_mod add: of_nat_take_bit)
 
 lemma unat_numeral: "unat (numeral b :: 'a::len word) = numeral b mod 2 ^ LENGTH('a)"
   by transfer (simp add: take_bit_eq_mod nat_mod_distrib nat_power_eq)
 
 lemma sint_numeral:
   "sint (numeral b :: 'a::len word) =
     (numeral b + 2 ^ (LENGTH('a) - 1)) mod 2 ^ LENGTH('a) - 2 ^ (LENGTH('a) - 1)"
   by (metis int_word_sint word_numeral_alt)
 
 lemma word_of_int_0 [simp, code_post]: "word_of_int 0 = 0"
   by (fact of_int_0)
 
 lemma word_of_int_1 [simp, code_post]: "word_of_int 1 = 1"
   by (fact of_int_1)
 
 lemma word_of_int_neg_1 [simp]: "word_of_int (- 1) = - 1"
   by (simp add: wi_hom_syms)
 
 lemma word_of_int_numeral [simp] : "(word_of_int (numeral bin) :: 'a::len word) = numeral bin"
   by (fact of_int_numeral)
 
 lemma word_of_int_neg_numeral [simp]:
   "(word_of_int (- numeral bin) :: 'a::len word) = - numeral bin"
   by (fact of_int_neg_numeral)
 
 lemma word_int_case_wi:
   "word_int_case f (word_of_int i :: 'b word) = f (i mod 2 ^ LENGTH('b::len))"
   by transfer (simp add: take_bit_eq_mod)
 
 lemma word_int_split:
   "P (word_int_case f x) =
     (\<forall>i. x = (word_of_int i :: 'b::len word) \<and> 0 \<le> i \<and> i < 2 ^ LENGTH('b) \<longrightarrow> P (f i))"
   by transfer (auto simp add: take_bit_eq_mod)
 
 lemma word_int_split_asm:
   "P (word_int_case f x) =
     (\<nexists>n. x = (word_of_int n :: 'b::len word) \<and> 0 \<le> n \<and> n < 2 ^ LENGTH('b::len) \<and> \<not> P (f n))"
   by transfer (auto simp add: take_bit_eq_mod)
 
 lemma uint_range_size: "0 \<le> uint w \<and> uint w < 2 ^ size w"
   by transfer simp
 
 lemma sint_range_size: "- (2 ^ (size w - Suc 0)) \<le> sint w \<and> sint w < 2 ^ (size w - Suc 0)"
   by (simp add: word_size sint_greater_eq sint_less)
 
 lemma sint_above_size: "2 ^ (size w - 1) \<le> x \<Longrightarrow> sint w < x"
   for w :: "'a::len word"
   unfolding word_size by (rule less_le_trans [OF sint_lt])
 
 lemma sint_below_size: "x \<le> - (2 ^ (size w - 1)) \<Longrightarrow> x \<le> sint w"
   for w :: "'a::len word"
   unfolding word_size by (rule order_trans [OF _ sint_ge])
 
 
 subsection \<open>Testing bits\<close>
 
 lemma bin_nth_uint_imp: "bit (uint w) n \<Longrightarrow> n < LENGTH('a)"
   for w :: "'a::len word"
   by transfer (simp add: bit_take_bit_iff)
 
 lemma bin_nth_sint:
   "LENGTH('a) \<le> n \<Longrightarrow>
     bit (sint w) n = bit (sint w) (LENGTH('a) - 1)"
   for w :: "'a::len word"
   by (transfer fixing: n) (simp add: bit_signed_take_bit_iff le_diff_conv min_def)
 
 lemma num_of_bintr':
   "take_bit (LENGTH('a::len)) (numeral a :: int) = (numeral b) \<Longrightarrow>
     numeral a = (numeral b :: 'a word)"
 proof (transfer fixing: a b)
   assume \<open>take_bit LENGTH('a) (numeral a :: int) = numeral b\<close>
   then have \<open>take_bit LENGTH('a) (take_bit LENGTH('a) (numeral a :: int)) = take_bit LENGTH('a) (numeral b)\<close>
     by simp
   then show \<open>take_bit LENGTH('a) (numeral a :: int) = take_bit LENGTH('a) (numeral b)\<close>
     by simp
 qed
 
 lemma num_of_sbintr':
   "signed_take_bit (LENGTH('a::len) - 1) (numeral a :: int) = (numeral b) \<Longrightarrow>
     numeral a = (numeral b :: 'a word)"
 proof (transfer fixing: a b)
   assume \<open>signed_take_bit (LENGTH('a) - 1) (numeral a :: int) = numeral b\<close>
   then have \<open>take_bit LENGTH('a) (signed_take_bit (LENGTH('a) - 1) (numeral a :: int)) = take_bit LENGTH('a) (numeral b)\<close>
     by simp
   then show \<open>take_bit LENGTH('a) (numeral a :: int) = take_bit LENGTH('a) (numeral b)\<close>
     by (simp add: take_bit_signed_take_bit)
 qed
  
 lemma num_abs_bintr:
   "(numeral x :: 'a word) =
     word_of_int (take_bit (LENGTH('a::len)) (numeral x))"
   by transfer simp
 
 lemma num_abs_sbintr:
   "(numeral x :: 'a word) =
     word_of_int (signed_take_bit (LENGTH('a::len) - 1) (numeral x))"
   by transfer (simp add: take_bit_signed_take_bit)
 
 text \<open>
   \<open>cast\<close> -- note, no arg for new length, as it's determined by type of result,
   thus in \<open>cast w = w\<close>, the type means cast to length of \<open>w\<close>!
 \<close>
 
 lemma bit_ucast_iff:
   \<open>bit (ucast a :: 'a::len word) n \<longleftrightarrow> n < LENGTH('a::len) \<and> bit a n\<close>
   by transfer (simp add: bit_take_bit_iff)
 
 lemma ucast_id [simp]: "ucast w = w"
   by transfer simp
 
 lemma scast_id [simp]: "scast w = w"
   by transfer (simp add: take_bit_signed_take_bit)
 
 lemma ucast_mask_eq:
   \<open>ucast (mask n :: 'b word) = mask (min LENGTH('b::len) n)\<close>
   by (simp add: bit_eq_iff) (auto simp add: bit_mask_iff bit_ucast_iff)
 
 \<comment> \<open>literal u(s)cast\<close>
 lemma ucast_bintr [simp]:
   "ucast (numeral w :: 'a::len word) =
     word_of_int (take_bit (LENGTH('a)) (numeral w))"
   by transfer simp
 
 (* TODO: neg_numeral *)
 
 lemma scast_sbintr [simp]:
   "scast (numeral w ::'a::len word) =
     word_of_int (signed_take_bit (LENGTH('a) - Suc 0) (numeral w))"
   by transfer simp
 
 lemma source_size: "source_size (c::'a::len word \<Rightarrow> _) = LENGTH('a)"
   by transfer simp
 
 lemma target_size: "target_size (c::_ \<Rightarrow> 'b::len word) = LENGTH('b)"
   by transfer simp
 
 lemma is_down: "is_down c \<longleftrightarrow> LENGTH('b) \<le> LENGTH('a)"
   for c :: "'a::len word \<Rightarrow> 'b::len word"
   by transfer simp
 
 lemma is_up: "is_up c \<longleftrightarrow> LENGTH('a) \<le> LENGTH('b)"
   for c :: "'a::len word \<Rightarrow> 'b::len word"
   by transfer simp
 
 lemma is_up_down:
   \<open>is_up c \<longleftrightarrow> is_down d\<close>
   for c :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   and d :: \<open>'b::len word \<Rightarrow> 'a::len word\<close>
   by transfer simp
 
 context
   fixes dummy_types :: \<open>'a::len \<times> 'b::len\<close>
 begin
 
 private abbreviation (input) UCAST :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>UCAST == ucast\<close>
 
 private abbreviation (input) SCAST :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>SCAST == scast\<close>
 
 lemma down_cast_same:
   \<open>UCAST = scast\<close> if \<open>is_down UCAST\<close>
   by (rule ext, use that in transfer) (simp add: take_bit_signed_take_bit)
 
 lemma sint_up_scast:
   \<open>sint (SCAST w) = sint w\<close> if \<open>is_up SCAST\<close>
   using that by transfer (simp add: min_def Suc_leI le_diff_iff)
 
 lemma uint_up_ucast:
   \<open>uint (UCAST w) = uint w\<close> if \<open>is_up UCAST\<close>
   using that by transfer (simp add: min_def)
 
 lemma ucast_up_ucast:
   \<open>ucast (UCAST w) = ucast w\<close> if \<open>is_up UCAST\<close>
   using that by transfer (simp add: ac_simps)
 
 lemma ucast_up_ucast_id:
   \<open>ucast (UCAST w) = w\<close> if \<open>is_up UCAST\<close>
   using that by (simp add: ucast_up_ucast)
 
 lemma scast_up_scast:
   \<open>scast (SCAST w) = scast w\<close> if \<open>is_up SCAST\<close>
   using that by transfer (simp add: ac_simps)
 
 lemma scast_up_scast_id:
   \<open>scast (SCAST w) = w\<close> if \<open>is_up SCAST\<close>
   using that by (simp add: scast_up_scast)
 
 lemma isduu:
   \<open>is_up UCAST\<close> if \<open>is_down d\<close>
     for d :: \<open>'b word \<Rightarrow> 'a word\<close>
   using that is_up_down [of UCAST d] by simp
 
 lemma isdus:
   \<open>is_up SCAST\<close> if \<open>is_down d\<close>
     for d :: \<open>'b word \<Rightarrow> 'a word\<close>
   using that is_up_down [of SCAST d] by simp
 
 lemmas ucast_down_ucast_id = isduu [THEN ucast_up_ucast_id]
 lemmas scast_down_scast_id = isdus [THEN scast_up_scast_id]
 
 lemma up_ucast_surj:
   \<open>surj (ucast :: 'b word \<Rightarrow> 'a word)\<close> if \<open>is_up UCAST\<close>
   by (rule surjI) (use that in \<open>rule ucast_up_ucast_id\<close>)
 
 lemma up_scast_surj:
   \<open>surj (scast :: 'b word \<Rightarrow> 'a word)\<close> if \<open>is_up SCAST\<close>
   by (rule surjI) (use that in \<open>rule scast_up_scast_id\<close>)
 
 lemma down_ucast_inj:
   \<open>inj_on UCAST A\<close> if \<open>is_down (ucast :: 'b word \<Rightarrow> 'a word)\<close>
   by (rule inj_on_inverseI) (use that in \<open>rule ucast_down_ucast_id\<close>)
 
 lemma down_scast_inj:
   \<open>inj_on SCAST A\<close> if \<open>is_down (scast :: 'b word \<Rightarrow> 'a word)\<close>
   by (rule inj_on_inverseI) (use that in \<open>rule scast_down_scast_id\<close>)
   
 lemma ucast_down_wi:
   \<open>UCAST (word_of_int x) = word_of_int x\<close> if \<open>is_down UCAST\<close>
   using that by transfer simp
 
 lemma ucast_down_no:
   \<open>UCAST (numeral bin) = numeral bin\<close> if \<open>is_down UCAST\<close>
   using that by transfer simp
 
 end
 
 lemmas word_log_defs = word_and_def word_or_def word_xor_def word_not_def
 
 lemma bit_last_iff:
   \<open>bit w (LENGTH('a) - Suc 0) \<longleftrightarrow> sint w < 0\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
   for w :: \<open>'a::len word\<close>
 proof -
   have \<open>?P \<longleftrightarrow> bit (uint w) (LENGTH('a) - Suc 0)\<close>
     by (simp add: bit_uint_iff)
   also have \<open>\<dots> \<longleftrightarrow> ?Q\<close>
     by (simp add: sint_uint)
   finally show ?thesis .
 qed
 
 lemma drop_bit_eq_zero_iff_not_bit_last:
   \<open>drop_bit (LENGTH('a) - Suc 0) w = 0 \<longleftrightarrow> \<not> bit w (LENGTH('a) - Suc 0)\<close>
   for w :: "'a::len word"
 proof (cases \<open>LENGTH('a)\<close>)
   case (Suc n)
   then show ?thesis
     apply transfer
     apply (simp add: take_bit_drop_bit)
     by (simp add: bit_iff_odd_drop_bit drop_bit_take_bit odd_iff_mod_2_eq_one)
 qed auto
 
 
 subsection \<open>Word Arithmetic\<close>
 
 lemmas word_div_no [simp] = word_div_def [of "numeral a" "numeral b"] for a b
 lemmas word_mod_no [simp] = word_mod_def [of "numeral a" "numeral b"] for a b
 lemmas word_less_no [simp] = word_less_def [of "numeral a" "numeral b"] for a b
 lemmas word_le_no [simp] = word_le_def [of "numeral a" "numeral b"] for a b
 lemmas word_sless_no [simp] = word_sless_eq [of "numeral a" "numeral b"] for a b
 lemmas word_sle_no [simp] = word_sle_eq [of "numeral a" "numeral b"] for a b
 
 lemma size_0_same': "size w = 0 \<Longrightarrow> w = v"
   for v w :: "'a::len word"
   by (unfold word_size) simp
 
 lemmas size_0_same = size_0_same' [unfolded word_size]
 
 lemmas unat_eq_0 = unat_0_iff
 lemmas unat_eq_zero = unat_0_iff
 
 
 subsection \<open>Transferring goals from words to ints\<close>
 
 lemma word_ths:
   shows word_succ_p1: "word_succ a = a + 1"
     and word_pred_m1: "word_pred a = a - 1"
     and word_pred_succ: "word_pred (word_succ a) = a"
     and word_succ_pred: "word_succ (word_pred a) = a"
     and word_mult_succ: "word_succ a * b = b + a * b"
   by (transfer, simp add: algebra_simps)+
 
 lemma uint_cong: "x = y \<Longrightarrow> uint x = uint y"
   by simp
 
 lemma uint_word_ariths:
   fixes a b :: "'a::len word"
   shows "uint (a + b) = (uint a + uint b) mod 2 ^ LENGTH('a::len)"
     and "uint (a - b) = (uint a - uint b) mod 2 ^ LENGTH('a)"
     and "uint (a * b) = uint a * uint b mod 2 ^ LENGTH('a)"
     and "uint (- a) = - uint a mod 2 ^ LENGTH('a)"
     and "uint (word_succ a) = (uint a + 1) mod 2 ^ LENGTH('a)"
     and "uint (word_pred a) = (uint a - 1) mod 2 ^ LENGTH('a)"
     and "uint (0 :: 'a word) = 0 mod 2 ^ LENGTH('a)"
     and "uint (1 :: 'a word) = 1 mod 2 ^ LENGTH('a)"
   by (simp_all only: word_arith_wis uint_word_of_int_eq flip: take_bit_eq_mod)
 
 lemma uint_word_arith_bintrs:
   fixes a b :: "'a::len word"
   shows "uint (a + b) = take_bit (LENGTH('a)) (uint a + uint b)"
     and "uint (a - b) = take_bit (LENGTH('a)) (uint a - uint b)"
     and "uint (a * b) = take_bit (LENGTH('a)) (uint a * uint b)"
     and "uint (- a) = take_bit (LENGTH('a)) (- uint a)"
     and "uint (word_succ a) = take_bit (LENGTH('a)) (uint a + 1)"
     and "uint (word_pred a) = take_bit (LENGTH('a)) (uint a - 1)"
     and "uint (0 :: 'a word) = take_bit (LENGTH('a)) 0"
     and "uint (1 :: 'a word) = take_bit (LENGTH('a)) 1"
   by (simp_all add: uint_word_ariths take_bit_eq_mod)
 
 lemma sint_word_ariths:
   fixes a b :: "'a::len word"
   shows "sint (a + b) = signed_take_bit (LENGTH('a) - 1) (sint a + sint b)"
     and "sint (a - b) = signed_take_bit (LENGTH('a) - 1) (sint a - sint b)"
     and "sint (a * b) = signed_take_bit (LENGTH('a) - 1) (sint a * sint b)"
     and "sint (- a) = signed_take_bit (LENGTH('a) - 1) (- sint a)"
     and "sint (word_succ a) = signed_take_bit (LENGTH('a) - 1) (sint a + 1)"
     and "sint (word_pred a) = signed_take_bit (LENGTH('a) - 1) (sint a - 1)"
     and "sint (0 :: 'a word) = signed_take_bit (LENGTH('a) - 1) 0"
     and "sint (1 :: 'a word) = signed_take_bit (LENGTH('a) - 1) 1"
   subgoal
     by transfer (simp add: signed_take_bit_add)
   subgoal
     by transfer (simp add: signed_take_bit_diff)
   subgoal
     by transfer (simp add: signed_take_bit_mult)
   subgoal
     by transfer (simp add: signed_take_bit_minus)
      apply (metis of_int_sint scast_id sint_sbintrunc' wi_hom_succ)
     apply (metis of_int_sint scast_id sint_sbintrunc' wi_hom_pred)
    apply (simp_all add: sint_uint)
   done
 
 lemma word_pred_0_n1: "word_pred 0 = word_of_int (- 1)"
   unfolding word_pred_m1 by simp
 
 lemma succ_pred_no [simp]:
     "word_succ (numeral w) = numeral w + 1"
     "word_pred (numeral w) = numeral w - 1"
     "word_succ (- numeral w) = - numeral w + 1"
     "word_pred (- numeral w) = - numeral w - 1"
   by (simp_all add: word_succ_p1 word_pred_m1)
 
 lemma word_sp_01 [simp]:
   "word_succ (- 1) = 0 \<and> word_succ 0 = 1 \<and> word_pred 0 = - 1 \<and> word_pred 1 = 0"
   by (simp_all add: word_succ_p1 word_pred_m1)
 
 \<comment> \<open>alternative approach to lifting arithmetic equalities\<close>
 lemma word_of_int_Ex: "\<exists>y. x = word_of_int y"
   by (rule_tac x="uint x" in exI) simp
 
 
 subsection \<open>Order on fixed-length words\<close>
 
 lift_definition udvd :: \<open>'a::len word \<Rightarrow> 'a::len word \<Rightarrow> bool\<close> (infixl \<open>udvd\<close> 50)
   is \<open>\<lambda>k l. take_bit LENGTH('a) k dvd take_bit LENGTH('a) l\<close> by simp
 
 lemma udvd_iff_dvd:
   \<open>x udvd y \<longleftrightarrow> unat x dvd unat y\<close>
   by transfer (simp add: nat_dvd_iff)
 
 lemma udvd_iff_dvd_int:
   \<open>v udvd w \<longleftrightarrow> uint v dvd uint w\<close>
   by transfer rule
 
 lemma udvdI [intro]:
   \<open>v udvd w\<close> if \<open>unat w = unat v * unat u\<close>
 proof -
   from that have \<open>unat v dvd unat w\<close> ..
   then show ?thesis
     by (simp add: udvd_iff_dvd)
 qed
 
 lemma udvdE [elim]:
   fixes v w :: \<open>'a::len word\<close>
   assumes \<open>v udvd w\<close>
   obtains u :: \<open>'a word\<close> where \<open>unat w = unat v * unat u\<close>
 proof (cases \<open>v = 0\<close>)
   case True
   moreover from True \<open>v udvd w\<close> have \<open>w = 0\<close>
     by transfer simp
   ultimately show thesis
     using that by simp
 next
   case False
   then have \<open>unat v > 0\<close>
     by (simp add: unat_gt_0)
   from \<open>v udvd w\<close> have \<open>unat v dvd unat w\<close>
     by (simp add: udvd_iff_dvd)
   then obtain n where \<open>unat w = unat v * n\<close> ..
   moreover have \<open>n < 2 ^ LENGTH('a)\<close>
   proof (rule ccontr)
     assume \<open>\<not> n < 2 ^ LENGTH('a)\<close>
     then have \<open>n \<ge> 2 ^ LENGTH('a)\<close>
       by (simp add: not_le)
     then have \<open>unat v * n \<ge> 2 ^ LENGTH('a)\<close>
       using \<open>unat v > 0\<close> mult_le_mono [of 1 \<open>unat v\<close> \<open>2 ^ LENGTH('a)\<close> n]
       by simp
     with \<open>unat w = unat v * n\<close>
     have \<open>unat w \<ge> 2 ^ LENGTH('a)\<close>
       by simp
     with unsigned_less [of w, where ?'a = nat] show False
       by linarith
   qed
   ultimately have \<open>unat w = unat v * unat (word_of_nat n :: 'a word)\<close>
     by (auto simp add: take_bit_nat_eq_self_iff intro: sym)
   with that show thesis .
 qed
 
 lemma udvd_imp_mod_eq_0:
   \<open>w mod v = 0\<close> if \<open>v udvd w\<close>
   using that by transfer simp
 
 lemma mod_eq_0_imp_udvd [intro?]:
   \<open>v udvd w\<close> if \<open>w mod v = 0\<close>
 proof -
   from that have \<open>unat (w mod v) = unat 0\<close>
     by simp
   then have \<open>unat w mod unat v = 0\<close>
     by (simp add: unat_mod_distrib)
   then have \<open>unat v dvd unat w\<close> ..
   then show ?thesis
     by (simp add: udvd_iff_dvd)
 qed
 
 lemma udvd_imp_dvd:
   \<open>v dvd w\<close> if \<open>v udvd w\<close> for v w :: \<open>'a::len word\<close>
 proof -
   from that obtain u :: \<open>'a word\<close> where \<open>unat w = unat v * unat u\<close> ..
   then have \<open>(word_of_nat (unat w) :: 'a word) = word_of_nat (unat v * unat u)\<close>
     by simp
   then have \<open>w = v * u\<close>
     by simp
   then show \<open>v dvd w\<close> ..
 qed
 
 lemma exp_dvd_iff_exp_udvd:
   \<open>2 ^ n dvd w \<longleftrightarrow> 2 ^ n udvd w\<close> for v w :: \<open>'a::len word\<close>
 proof
   assume \<open>2 ^ n udvd w\<close> then show \<open>2 ^ n dvd w\<close>
     by (rule udvd_imp_dvd) 
 next
   assume \<open>2 ^ n dvd w\<close>
   then obtain u :: \<open>'a word\<close> where \<open>w = 2 ^ n * u\<close> ..
   then have \<open>w = push_bit n u\<close>
     by (simp add: push_bit_eq_mult)
   then show \<open>2 ^ n udvd w\<close>
     by transfer (simp add: take_bit_push_bit dvd_eq_mod_eq_0 flip: take_bit_eq_mod)
 qed
 
 lemma udvd_nat_alt:
   \<open>a udvd b \<longleftrightarrow> (\<exists>n. unat b = n * unat a)\<close>
   by (auto simp add: udvd_iff_dvd)
 
 lemma udvd_unfold_int:
   \<open>a udvd b \<longleftrightarrow> (\<exists>n\<ge>0. uint b = n * uint a)\<close>
   unfolding udvd_iff_dvd_int
   by (metis dvd_div_mult_self dvd_triv_right uint_div_distrib uint_ge_0)
 
 lemma unat_minus_one:
   \<open>unat (w - 1) = unat w - 1\<close> if \<open>w \<noteq> 0\<close>
 proof -
   have "0 \<le> uint w" by (fact uint_nonnegative)
   moreover from that have "0 \<noteq> uint w"
     by (simp add: uint_0_iff)
   ultimately have "1 \<le> uint w"
     by arith
   from uint_lt2p [of w] have "uint w - 1 < 2 ^ LENGTH('a)"
     by arith
   with \<open>1 \<le> uint w\<close> have "(uint w - 1) mod 2 ^ LENGTH('a) = uint w - 1"
     by (auto intro: mod_pos_pos_trivial)
   with \<open>1 \<le> uint w\<close> have "nat ((uint w - 1) mod 2 ^ LENGTH('a)) = nat (uint w) - 1"
     by (auto simp del: nat_uint_eq)
   then show ?thesis
     by (simp only: unat_eq_nat_uint word_arith_wis mod_diff_right_eq)
       (metis of_int_1 uint_word_of_int unsigned_1)
 qed
 
 lemma measure_unat: "p \<noteq> 0 \<Longrightarrow> unat (p - 1) < unat p"
   by (simp add: unat_minus_one) (simp add: unat_0_iff [symmetric])
 
 lemmas uint_add_ge0 [simp] = add_nonneg_nonneg [OF uint_ge_0 uint_ge_0]
 lemmas uint_mult_ge0 [simp] = mult_nonneg_nonneg [OF uint_ge_0 uint_ge_0]
 
 lemma uint_sub_lt2p [simp]: "uint x - uint y < 2 ^ LENGTH('a)"
   for x :: "'a::len word" and y :: "'b::len word"
   using uint_ge_0 [of y] uint_lt2p [of x] by arith
 
 
 subsection \<open>Conditions for the addition (etc) of two words to overflow\<close>
 
 lemma uint_add_lem:
   "(uint x + uint y < 2 ^ LENGTH('a)) =
     (uint (x + y) = uint x + uint y)"
   for x y :: "'a::len word"
   by (metis add.right_neutral add_mono_thms_linordered_semiring(1) mod_pos_pos_trivial of_nat_0_le_iff uint_lt2p uint_nat uint_word_ariths(1))
 
 lemma uint_mult_lem:
   "(uint x * uint y < 2 ^ LENGTH('a)) =
     (uint (x * y) = uint x * uint y)"
   for x y :: "'a::len word"
   by (metis mod_pos_pos_trivial uint_lt2p uint_mult_ge0 uint_word_ariths(3))
 
 lemma uint_sub_lem: "uint x \<ge> uint y \<longleftrightarrow> uint (x - y) = uint x - uint y"
   by (metis diff_ge_0_iff_ge of_nat_0_le_iff uint_nat uint_sub_lt2p uint_word_of_int unique_euclidean_semiring_numeral_class.mod_less word_sub_wi)
 
 lemma uint_add_le: "uint (x + y) \<le> uint x + uint y"
   unfolding uint_word_ariths by (simp add: zmod_le_nonneg_dividend) 
 
 lemma uint_sub_ge: "uint (x - y) \<ge> uint x - uint y"
   unfolding uint_word_ariths
   by (simp flip: take_bit_eq_mod add: take_bit_int_greater_eq_self_iff)
 
 lemma int_mod_ge: \<open>a \<le> a mod n\<close> if \<open>a < n\<close> \<open>0 < n\<close>
   for a n :: int
 proof (cases \<open>a < 0\<close>)
   case True
   with \<open>0 < n\<close> show ?thesis
     by (metis less_trans not_less pos_mod_conj)
     
 next
   case False
   with \<open>a < n\<close> show ?thesis
     by simp
 qed
 
 lemma mod_add_if_z:
   "\<lbrakk>x < z; y < z; 0 \<le> y; 0 \<le> x; 0 \<le> z\<rbrakk> \<Longrightarrow>
     (x + y) mod z = (if x + y < z then x + y else x + y - z)"
   for x y z :: int
   apply (simp add: not_less)
   by (metis (no_types) add_strict_mono diff_ge_0_iff_ge diff_less_eq minus_mod_self2 mod_pos_pos_trivial)
 
 lemma uint_plus_if':
   "uint (a + b) =
     (if uint a + uint b < 2 ^ LENGTH('a) then uint a + uint b
      else uint a + uint b - 2 ^ LENGTH('a))"
   for a b :: "'a::len word"
   using mod_add_if_z [of "uint a" _ "uint b"] by (simp add: uint_word_ariths)
 
 lemma mod_sub_if_z:
   "\<lbrakk>x < z; y < z; 0 \<le> y; 0 \<le> x; 0 \<le> z\<rbrakk> \<Longrightarrow>
     (x - y) mod z = (if y \<le> x then x - y else x - y + z)"
   for x y z :: int
   using mod_pos_pos_trivial [of "x - y + z" z] by (auto simp add: not_le)
 
 lemma uint_sub_if':
   "uint (a - b) =
     (if uint b \<le> uint a then uint a - uint b
      else uint a - uint b + 2 ^ LENGTH('a))"
   for a b :: "'a::len word"
   using mod_sub_if_z [of "uint a" _ "uint b"] by (simp add: uint_word_ariths)
 
 
 subsection \<open>Definition of \<open>uint_arith\<close>\<close>
 
 lemma word_of_int_inverse:
   "word_of_int r = a \<Longrightarrow> 0 \<le> r \<Longrightarrow> r < 2 ^ LENGTH('a) \<Longrightarrow> uint a = r"
   for a :: "'a::len word"
   by transfer (simp add: take_bit_int_eq_self)
 
 lemma uint_split:
   "P (uint x) = (\<forall>i. word_of_int i = x \<and> 0 \<le> i \<and> i < 2^LENGTH('a) \<longrightarrow> P i)"
   for x :: "'a::len word"
   by transfer (auto simp add: take_bit_eq_mod)
 
 lemma uint_split_asm:
   "P (uint x) = (\<nexists>i. word_of_int i = x \<and> 0 \<le> i \<and> i < 2^LENGTH('a) \<and> \<not> P i)"
   for x :: "'a::len word"
   by auto (metis take_bit_int_eq_self_iff)
 
 lemmas uint_splits = uint_split uint_split_asm
 
 lemmas uint_arith_simps =
   word_le_def word_less_alt
   word_uint_eq_iff
   uint_sub_if' uint_plus_if'
 
 \<comment> \<open>use this to stop, eg. \<open>2 ^ LENGTH(32)\<close> being simplified\<close>
 lemma power_False_cong: "False \<Longrightarrow> a ^ b = c ^ d"
   by auto
 
 \<comment> \<open>\<open>uint_arith_tac\<close>: reduce to arithmetic on int, try to solve by arith\<close>
 ML \<open>
 val uint_arith_simpset =
   @{context}
   |> fold Simplifier.add_simp @{thms uint_arith_simps}
   |> fold Splitter.add_split @{thms if_split_asm}
   |> fold Simplifier.add_cong @{thms power_False_cong}
   |> simpset_of;
   
 fun uint_arith_tacs ctxt =
   let
     fun arith_tac' n t =
       Arith_Data.arith_tac ctxt n t
         handle Cooper.COOPER _ => Seq.empty;
   in
     [ clarify_tac ctxt 1,
       full_simp_tac (put_simpset uint_arith_simpset ctxt) 1,
       ALLGOALS (full_simp_tac
         (put_simpset HOL_ss ctxt
           |> fold Splitter.add_split @{thms uint_splits}
           |> fold Simplifier.add_cong @{thms power_False_cong})),
       rewrite_goals_tac ctxt @{thms word_size},
       ALLGOALS  (fn n => REPEAT (resolve_tac ctxt [allI, impI] n) THEN
                          REPEAT (eresolve_tac ctxt [conjE] n) THEN
                          REPEAT (dresolve_tac ctxt @{thms word_of_int_inverse} n
                                  THEN assume_tac ctxt n
                                  THEN assume_tac ctxt n)),
       TRYALL arith_tac' ]
   end
 
 fun uint_arith_tac ctxt = SELECT_GOAL (EVERY (uint_arith_tacs ctxt))
 \<close>
 
 method_setup uint_arith =
   \<open>Scan.succeed (SIMPLE_METHOD' o uint_arith_tac)\<close>
   "solving word arithmetic via integers and arith"
 
 
 subsection \<open>More on overflows and monotonicity\<close>
 
 lemma no_plus_overflow_uint_size: "x \<le> x + y \<longleftrightarrow> uint x + uint y < 2 ^ size x"
   for x y :: "'a::len word"
   unfolding word_size by uint_arith
 
 lemmas no_olen_add = no_plus_overflow_uint_size [unfolded word_size]
 
 lemma no_ulen_sub: "x \<ge> x - y \<longleftrightarrow> uint y \<le> uint x"
   for x y :: "'a::len word"
   by uint_arith
 
 lemma no_olen_add': "x \<le> y + x \<longleftrightarrow> uint y + uint x < 2 ^ LENGTH('a)"
   for x y :: "'a::len word"
   by (simp add: ac_simps no_olen_add)
 
 lemmas olen_add_eqv = trans [OF no_olen_add no_olen_add' [symmetric]]
 
 lemmas uint_plus_simple_iff = trans [OF no_olen_add uint_add_lem]
 lemmas uint_plus_simple = uint_plus_simple_iff [THEN iffD1]
 lemmas uint_minus_simple_iff = trans [OF no_ulen_sub uint_sub_lem]
 lemmas uint_minus_simple_alt = uint_sub_lem [folded word_le_def]
 lemmas word_sub_le_iff = no_ulen_sub [folded word_le_def]
 lemmas word_sub_le = word_sub_le_iff [THEN iffD2]
 
 lemma word_less_sub1: "x \<noteq> 0 \<Longrightarrow> 1 < x \<longleftrightarrow> 0 < x - 1"
   for x :: "'a::len word"
   by uint_arith
 
 lemma word_le_sub1: "x \<noteq> 0 \<Longrightarrow> 1 \<le> x \<longleftrightarrow> 0 \<le> x - 1"
   for x :: "'a::len word"
   by uint_arith
 
 lemma sub_wrap_lt: "x < x - z \<longleftrightarrow> x < z"
   for x z :: "'a::len word"
   by uint_arith
 
 lemma sub_wrap: "x \<le> x - z \<longleftrightarrow> z = 0 \<or> x < z"
   for x z :: "'a::len word"
   by uint_arith
 
 lemma plus_minus_not_NULL_ab: "x \<le> ab - c \<Longrightarrow> c \<le> ab \<Longrightarrow> c \<noteq> 0 \<Longrightarrow> x + c \<noteq> 0"
   for x ab c :: "'a::len word"
   by uint_arith
 
 lemma plus_minus_no_overflow_ab: "x \<le> ab - c \<Longrightarrow> c \<le> ab \<Longrightarrow> x \<le> x + c"
   for x ab c :: "'a::len word"
   by uint_arith
 
 lemma le_minus': "a + c \<le> b \<Longrightarrow> a \<le> a + c \<Longrightarrow> c \<le> b - a"
   for a b c :: "'a::len word"
   by uint_arith
 
 lemma le_plus': "a \<le> b \<Longrightarrow> c \<le> b - a \<Longrightarrow> a + c \<le> b"
   for a b c :: "'a::len word"
   by uint_arith
 
 lemmas le_plus = le_plus' [rotated]
 
 lemmas le_minus = leD [THEN thin_rl, THEN le_minus'] (* FIXME *)
 
 lemma word_plus_mono_right: "y \<le> z \<Longrightarrow> x \<le> x + z \<Longrightarrow> x + y \<le> x + z"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_less_minus_cancel: "y - x < z - x \<Longrightarrow> x \<le> z \<Longrightarrow> y < z"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_less_minus_mono_left: "y < z \<Longrightarrow> x \<le> y \<Longrightarrow> y - x < z - x"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_less_minus_mono: "a < c \<Longrightarrow> d < b \<Longrightarrow> a - b < a \<Longrightarrow> c - d < c \<Longrightarrow> a - b < c - d"
   for a b c d :: "'a::len word"
   by uint_arith
 
 lemma word_le_minus_cancel: "y - x \<le> z - x \<Longrightarrow> x \<le> z \<Longrightarrow> y \<le> z"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_le_minus_mono_left: "y \<le> z \<Longrightarrow> x \<le> y \<Longrightarrow> y - x \<le> z - x"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_le_minus_mono:
   "a \<le> c \<Longrightarrow> d \<le> b \<Longrightarrow> a - b \<le> a \<Longrightarrow> c - d \<le> c \<Longrightarrow> a - b \<le> c - d"
   for a b c d :: "'a::len word"
   by uint_arith
 
 lemma plus_le_left_cancel_wrap: "x + y' < x \<Longrightarrow> x + y < x \<Longrightarrow> x + y' < x + y \<longleftrightarrow> y' < y"
   for x y y' :: "'a::len word"
   by uint_arith
 
 lemma plus_le_left_cancel_nowrap: "x \<le> x + y' \<Longrightarrow> x \<le> x + y \<Longrightarrow> x + y' < x + y \<longleftrightarrow> y' < y"
   for x y y' :: "'a::len word"
   by uint_arith
 
 lemma word_plus_mono_right2: "a \<le> a + b \<Longrightarrow> c \<le> b \<Longrightarrow> a \<le> a + c"
   for a b c :: "'a::len word"
   by uint_arith
 
 lemma word_less_add_right: "x < y - z \<Longrightarrow> z \<le> y \<Longrightarrow> x + z < y"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_less_sub_right: "x < y + z \<Longrightarrow> y \<le> x \<Longrightarrow> x - y < z"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_le_plus_either: "x \<le> y \<or> x \<le> z \<Longrightarrow> y \<le> y + z \<Longrightarrow> x \<le> y + z"
   for x y z :: "'a::len word"
   by uint_arith
 
 lemma word_less_nowrapI: "x < z - k \<Longrightarrow> k \<le> z \<Longrightarrow> 0 < k \<Longrightarrow> x < x + k"
   for x z k :: "'a::len word"
   by uint_arith
 
 lemma inc_le: "i < m \<Longrightarrow> i + 1 \<le> m"
   for i m :: "'a::len word"
   by uint_arith
 
 lemma inc_i: "1 \<le> i \<Longrightarrow> i < m \<Longrightarrow> 1 \<le> i + 1 \<and> i + 1 \<le> m"
   for i m :: "'a::len word"
   by uint_arith
 
 lemma udvd_incr_lem:
   "up < uq \<Longrightarrow> up = ua + n * uint K \<Longrightarrow>
     uq = ua + n' * uint K \<Longrightarrow> up + uint K \<le> uq"
   by auto (metis int_distrib(1) linorder_not_less mult.left_neutral mult_right_mono uint_nonnegative zless_imp_add1_zle)
 
 lemma udvd_incr':
   "p < q \<Longrightarrow> uint p = ua + n * uint K \<Longrightarrow>
     uint q = ua + n' * uint K \<Longrightarrow> p + K \<le> q"
   unfolding word_less_alt word_le_def
   by (metis (full_types) order_trans udvd_incr_lem uint_add_le)
 
 lemma udvd_decr':
   assumes "p < q" "uint p = ua + n * uint K" "uint q = ua + n' * uint K"
     shows "uint q = ua + n' * uint K \<Longrightarrow> p \<le> q - K"
 proof -
   have "\<And>w wa. uint (w::'a word) \<le> uint wa + uint (w - wa)"
     by (metis (no_types) add_diff_cancel_left' diff_add_cancel uint_add_le)
   moreover have "uint K + uint p \<le> uint q"
     using assms by (metis (no_types) add_diff_cancel_left' diff_add_cancel udvd_incr_lem word_less_def)
   ultimately show ?thesis
     by (meson add_le_cancel_left order_trans word_less_eq_iff_unsigned)
 qed
 
 lemmas udvd_incr_lem0 = udvd_incr_lem [where ua=0, unfolded add_0_left]
 lemmas udvd_incr0 = udvd_incr' [where ua=0, unfolded add_0_left]
 lemmas udvd_decr0 = udvd_decr' [where ua=0, unfolded add_0_left]
 
 lemma udvd_minus_le': "xy < k \<Longrightarrow> z udvd xy \<Longrightarrow> z udvd k \<Longrightarrow> xy \<le> k - z"
   unfolding udvd_unfold_int
   by (meson udvd_decr0)
 
 lemma udvd_incr2_K:
   "p < a + s \<Longrightarrow> a \<le> a + s \<Longrightarrow> K udvd s \<Longrightarrow> K udvd p - a \<Longrightarrow> a \<le> p \<Longrightarrow>
     0 < K \<Longrightarrow> p \<le> p + K \<and> p + K \<le> a + s"
   unfolding udvd_unfold_int
   apply (simp add: uint_arith_simps split: if_split_asm)
   apply (metis (no_types, opaque_lifting) le_add_diff_inverse le_less_trans udvd_incr_lem)
   using uint_lt2p [of s] by simp
 
 
 subsection \<open>Arithmetic type class instantiations\<close>
 
 lemmas word_le_0_iff [simp] =
   word_zero_le [THEN leD, THEN antisym_conv1]
 
 lemma word_of_int_nat: "0 \<le> x \<Longrightarrow> word_of_int x = of_nat (nat x)"
   by simp
 
 text \<open>
   note that \<open>iszero_def\<close> is only for class \<open>comm_semiring_1_cancel\<close>,
   which requires word length \<open>\<ge> 1\<close>, ie \<open>'a::len word\<close>
 \<close>
 lemma iszero_word_no [simp]:
   "iszero (numeral bin :: 'a::len word) =
     iszero (take_bit LENGTH('a) (numeral bin :: int))"
   by (metis iszero_def uint_0_iff uint_bintrunc)
 
 text \<open>Use \<open>iszero\<close> to simplify equalities between word numerals.\<close>
 
 lemmas word_eq_numeral_iff_iszero [simp] =
   eq_numeral_iff_iszero [where 'a="'a::len word"]
 
 
 subsection \<open>Word and nat\<close>
 
 lemma word_nchotomy: "\<forall>w :: 'a::len word. \<exists>n. w = of_nat n \<and> n < 2 ^ LENGTH('a)"
   by (metis of_nat_unat ucast_id unsigned_less)
 
 lemma of_nat_eq: "of_nat n = w \<longleftrightarrow> (\<exists>q. n = unat w + q * 2 ^ LENGTH('a))"
   for w :: "'a::len word"
   using mod_div_mult_eq [of n "2 ^ LENGTH('a)", symmetric]
   by (auto simp flip: take_bit_eq_mod)
 
 lemma of_nat_eq_size: "of_nat n = w \<longleftrightarrow> (\<exists>q. n = unat w + q * 2 ^ size w)"
   unfolding word_size by (rule of_nat_eq)
 
 lemma of_nat_0: "of_nat m = (0::'a::len word) \<longleftrightarrow> (\<exists>q. m = q * 2 ^ LENGTH('a))"
   by (simp add: of_nat_eq)
 
 lemma of_nat_2p [simp]: "of_nat (2 ^ LENGTH('a)) = (0::'a::len word)"
   by (fact mult_1 [symmetric, THEN iffD2 [OF of_nat_0 exI]])
 
 lemma of_nat_gt_0: "of_nat k \<noteq> 0 \<Longrightarrow> 0 < k"
   by (cases k) auto
 
 lemma of_nat_neq_0: "0 < k \<Longrightarrow> k < 2 ^ LENGTH('a::len) \<Longrightarrow> of_nat k \<noteq> (0 :: 'a word)"
   by (auto simp add : of_nat_0)
 
 lemma Abs_fnat_hom_add: "of_nat a + of_nat b = of_nat (a + b)"
   by simp
 
 lemma Abs_fnat_hom_mult: "of_nat a * of_nat b = (of_nat (a * b) :: 'a::len word)"
   by (simp add: wi_hom_mult)
 
 lemma Abs_fnat_hom_Suc: "word_succ (of_nat a) = of_nat (Suc a)"
   by transfer (simp add: ac_simps)
 
 lemma Abs_fnat_hom_0: "(0::'a::len word) = of_nat 0"
   by simp
 
 lemma Abs_fnat_hom_1: "(1::'a::len word) = of_nat (Suc 0)"
   by simp
 
 lemmas Abs_fnat_homs =
   Abs_fnat_hom_add Abs_fnat_hom_mult Abs_fnat_hom_Suc
   Abs_fnat_hom_0 Abs_fnat_hom_1
 
 lemma word_arith_nat_add: "a + b = of_nat (unat a + unat b)"
   by simp
 
 lemma word_arith_nat_mult: "a * b = of_nat (unat a * unat b)"
   by simp
 
 lemma word_arith_nat_Suc: "word_succ a = of_nat (Suc (unat a))"
   by (subst Abs_fnat_hom_Suc [symmetric]) simp
 
 lemma word_arith_nat_div: "a div b = of_nat (unat a div unat b)"
   by (metis of_int_of_nat_eq of_nat_unat of_nat_div word_div_def)
   
 lemma word_arith_nat_mod: "a mod b = of_nat (unat a mod unat b)"
   by (metis of_int_of_nat_eq of_nat_mod of_nat_unat word_mod_def)
 
 lemmas word_arith_nat_defs =
   word_arith_nat_add word_arith_nat_mult
   word_arith_nat_Suc Abs_fnat_hom_0
   Abs_fnat_hom_1 word_arith_nat_div
   word_arith_nat_mod
 
 lemma unat_cong: "x = y \<Longrightarrow> unat x = unat y"
   by (fact arg_cong)
 
 lemma unat_of_nat:
   \<open>unat (word_of_nat x :: 'a::len word) = x mod 2 ^ LENGTH('a)\<close>
   by transfer (simp flip: take_bit_eq_mod add: nat_take_bit_eq)
 
 lemmas unat_word_ariths = word_arith_nat_defs
   [THEN trans [OF unat_cong unat_of_nat]]
 
 lemmas word_sub_less_iff = word_sub_le_iff
   [unfolded linorder_not_less [symmetric] Not_eq_iff]
 
 lemma unat_add_lem:
   "unat x + unat y < 2 ^ LENGTH('a) \<longleftrightarrow> unat (x + y) = unat x + unat y"
   for x y :: "'a::len word"
   by (metis mod_less unat_word_ariths(1) unsigned_less)
 
 lemma unat_mult_lem:
   "unat x * unat y < 2 ^ LENGTH('a) \<longleftrightarrow> unat (x * y) = unat x * unat y"
   for x y :: "'a::len word"
   by (metis mod_less unat_word_ariths(2) unsigned_less)
 
 lemma unat_plus_if':
   \<open>unat (a + b) =
     (if unat a + unat b < 2 ^ LENGTH('a)
     then unat a + unat b
     else unat a + unat b - 2 ^ LENGTH('a))\<close> for a b :: \<open>'a::len word\<close>
   apply (auto simp: unat_word_ariths not_less le_iff_add)
   by (metis add.commute add_less_cancel_right add_strict_mono mod_less unsigned_less)
 
 lemma le_no_overflow: "x \<le> b \<Longrightarrow> a \<le> a + b \<Longrightarrow> x \<le> a + b"
   for a b x :: "'a::len word"
   using word_le_plus_either by blast
 
 lemmas un_ui_le =
   trans [OF word_le_nat_alt [symmetric] word_le_def]
 
 lemma unat_sub_if_size:
   "unat (x - y) =
     (if unat y \<le> unat x
      then unat x - unat y
      else unat x + 2 ^ size x - unat y)"
 proof -
   { assume xy: "\<not> uint y \<le> uint x"
     have "nat (uint x - uint y + 2 ^ LENGTH('a)) = nat (uint x + 2 ^ LENGTH('a) - uint y)"
       by simp
     also have "... = nat (uint x + 2 ^ LENGTH('a)) - nat (uint y)"
       by (simp add: nat_diff_distrib')
     also have "... = nat (uint x) + 2 ^ LENGTH('a) - nat (uint y)"
       by (metis nat_add_distrib nat_eq_numeral_power_cancel_iff order_less_imp_le unsigned_0 unsigned_greater_eq unsigned_less)
     finally have "nat (uint x - uint y + 2 ^ LENGTH('a)) = nat (uint x) + 2 ^ LENGTH('a) - nat (uint y)" .
   }
   then show ?thesis
   unfolding word_size
   by (metis nat_diff_distrib' uint_sub_if' un_ui_le unat_eq_nat_uint unsigned_greater_eq)
 qed
 
 lemmas unat_sub_if' = unat_sub_if_size [unfolded word_size]
 
 lemma uint_div:
   \<open>uint (x div y) = uint x div uint y\<close>
   by (fact uint_div_distrib)
 
 lemma unat_div:
   \<open>unat (x div y) = unat x div unat y\<close>
   by (fact unat_div_distrib)
 
 lemma uint_mod:
   \<open>uint (x mod y) = uint x mod uint y\<close>
   by (fact uint_mod_distrib)
   
 lemma unat_mod:
   \<open>unat (x mod y) = unat x mod unat y\<close>
   by (fact unat_mod_distrib)
 
 
 text \<open>Definition of \<open>unat_arith\<close> tactic\<close>
 
 lemma unat_split: "P (unat x) \<longleftrightarrow> (\<forall>n. of_nat n = x \<and> n < 2^LENGTH('a) \<longrightarrow> P n)"
   for x :: "'a::len word"
   by auto (metis take_bit_nat_eq_self_iff)
 
 lemma unat_split_asm: "P (unat x) \<longleftrightarrow> (\<nexists>n. of_nat n = x \<and> n < 2^LENGTH('a) \<and> \<not> P n)"
   for x :: "'a::len word"
   by auto (metis take_bit_nat_eq_self_iff)
 
 lemma of_nat_inverse:
   \<open>word_of_nat r = a \<Longrightarrow> r < 2 ^ LENGTH('a) \<Longrightarrow> unat a = r\<close>
   for a :: \<open>'a::len word\<close>
   by (metis mod_if unat_of_nat)
 
 lemma word_unat_eq_iff:
   \<open>v = w \<longleftrightarrow> unat v = unat w\<close>
   for v w :: \<open>'a::len word\<close>
   by (fact word_eq_iff_unsigned)
 
 lemmas unat_splits = unat_split unat_split_asm
 
 lemmas unat_arith_simps =
   word_le_nat_alt word_less_nat_alt
   word_unat_eq_iff
   unat_sub_if' unat_plus_if' unat_div unat_mod
 
 \<comment> \<open>\<open>unat_arith_tac\<close>: tactic to reduce word arithmetic to \<open>nat\<close>, try to solve via \<open>arith\<close>\<close>
 ML \<open>
 val unat_arith_simpset =
   @{context} (* TODO: completely explicitly determined simpset *)
   |> fold Simplifier.del_simp @{thms unsigned_of_nat unsigned_of_int}
   |> fold Simplifier.add_simp @{thms unat_arith_simps}
   |> fold Splitter.add_split @{thms if_split_asm}
   |> fold Simplifier.add_cong @{thms power_False_cong}
   |> simpset_of
 
 fun unat_arith_tacs ctxt =
   let
     fun arith_tac' n t =
       Arith_Data.arith_tac ctxt n t
         handle Cooper.COOPER _ => Seq.empty;
   in
     [ clarify_tac ctxt 1,
       full_simp_tac (put_simpset unat_arith_simpset ctxt) 1,
       ALLGOALS (full_simp_tac
         (put_simpset HOL_ss ctxt
           |> fold Splitter.add_split @{thms unat_splits}
           |> fold Simplifier.add_cong @{thms power_False_cong})),
       rewrite_goals_tac ctxt @{thms word_size},
       ALLGOALS (fn n => REPEAT (resolve_tac ctxt [allI, impI] n) THEN
                          REPEAT (eresolve_tac ctxt [conjE] n) THEN
                          REPEAT (dresolve_tac ctxt @{thms of_nat_inverse} n THEN assume_tac ctxt n)),
       TRYALL arith_tac' ]
   end
 
 fun unat_arith_tac ctxt = SELECT_GOAL (EVERY (unat_arith_tacs ctxt))
 \<close>
 
 method_setup unat_arith =
   \<open>Scan.succeed (SIMPLE_METHOD' o unat_arith_tac)\<close>
   "solving word arithmetic via natural numbers and arith"
 
 lemma no_plus_overflow_unat_size: "x \<le> x + y \<longleftrightarrow> unat x + unat y < 2 ^ size x"
   for x y :: "'a::len word"
   unfolding word_size by unat_arith
 
 lemmas no_olen_add_nat =
   no_plus_overflow_unat_size [unfolded word_size]
 
 lemmas unat_plus_simple =
   trans [OF no_olen_add_nat unat_add_lem]
 
 lemma word_div_mult: "\<lbrakk>0 < y; unat x * unat y < 2 ^ LENGTH('a)\<rbrakk> \<Longrightarrow> x * y div y = x"
   for x y :: "'a::len word"
   by (simp add: unat_eq_zero unat_mult_lem word_arith_nat_div)
 
 lemma div_lt': "i \<le> k div x \<Longrightarrow> unat i * unat x < 2 ^ LENGTH('a)"
   for i k x :: "'a::len word"
   by unat_arith (meson le_less_trans less_mult_imp_div_less not_le unsigned_less)
 
 lemmas div_lt'' = order_less_imp_le [THEN div_lt']
 
 lemma div_lt_mult: "\<lbrakk>i < k div x; 0 < x\<rbrakk> \<Longrightarrow> i * x < k"
   for i k x :: "'a::len word"
   by (metis div_le_mono div_lt'' not_le unat_div word_div_mult word_less_iff_unsigned)
 
 lemma div_le_mult: "\<lbrakk>i \<le> k div x; 0 < x\<rbrakk> \<Longrightarrow> i * x \<le> k"
   for i k x :: "'a::len word"
   by (metis div_lt' less_mult_imp_div_less not_less unat_arith_simps(2) unat_div unat_mult_lem)
 
 lemma div_lt_uint': "i \<le> k div x \<Longrightarrow> uint i * uint x < 2 ^ LENGTH('a)"
   for i k x :: "'a::len word"
   unfolding uint_nat
   by (metis div_lt' int_ops(7) of_nat_unat uint_mult_lem unat_mult_lem)
 
 lemmas div_lt_uint'' = order_less_imp_le [THEN div_lt_uint']
 
 lemma word_le_exists': "x \<le> y \<Longrightarrow> \<exists>z. y = x + z \<and> uint x + uint z < 2 ^ LENGTH('a)"
   for x y z :: "'a::len word"
   by (metis add.commute diff_add_cancel no_olen_add)
   
 lemmas plus_minus_not_NULL = order_less_imp_le [THEN plus_minus_not_NULL_ab]
 
 lemmas plus_minus_no_overflow =
   order_less_imp_le [THEN plus_minus_no_overflow_ab]
 
 lemmas mcs = word_less_minus_cancel word_less_minus_mono_left
   word_le_minus_cancel word_le_minus_mono_left
 
 lemmas word_l_diffs = mcs [where y = "w + x", unfolded add_diff_cancel] for w x
 lemmas word_diff_ls = mcs [where z = "w + x", unfolded add_diff_cancel] for w x
 lemmas word_plus_mcs = word_diff_ls [where y = "v + x", unfolded add_diff_cancel] for v x
 
 lemma le_unat_uoi:
   \<open>y \<le> unat z \<Longrightarrow> unat (word_of_nat y :: 'a word) = y\<close>
   for z :: \<open>'a::len word\<close>
   by transfer (simp add: nat_take_bit_eq take_bit_nat_eq_self_iff le_less_trans)
 
 lemmas thd = times_div_less_eq_dividend
 
 lemmas uno_simps [THEN le_unat_uoi] = mod_le_divisor div_le_dividend
 
 lemma word_mod_div_equality: "(n div b) * b + (n mod b) = n"
   for n b :: "'a::len word"
   by (fact div_mult_mod_eq)
 
 lemma word_div_mult_le: "a div b * b \<le> a"
   for a b :: "'a::len word"
   by (metis div_le_mult mult_not_zero order.not_eq_order_implies_strict order_refl word_zero_le)
 
 lemma word_mod_less_divisor: "0 < n \<Longrightarrow> m mod n < n"
   for m n :: "'a::len word"
   by (simp add: unat_arith_simps)
   
 lemma word_of_int_power_hom: "word_of_int a ^ n = (word_of_int (a ^ n) :: 'a::len word)"
   by (induct n) (simp_all add: wi_hom_mult [symmetric])
 
 lemma word_arith_power_alt: "a ^ n = (word_of_int (uint a ^ n) :: 'a::len word)"
   by (simp add : word_of_int_power_hom [symmetric])
 
 lemma unatSuc: "1 + n \<noteq> 0 \<Longrightarrow> unat (1 + n) = Suc (unat n)"
   for n :: "'a::len word"
   by unat_arith
 
 
 subsection \<open>Cardinality, finiteness of set of words\<close>
 
 lemma inj_on_word_of_int: \<open>inj_on (word_of_int :: int \<Rightarrow> 'a word) {0..<2 ^ LENGTH('a::len)}\<close>
   unfolding inj_on_def
   by (metis atLeastLessThan_iff word_of_int_inverse)
 
 lemma range_uint: \<open>range (uint :: 'a word \<Rightarrow> int) = {0..<2 ^ LENGTH('a::len)}\<close>
   apply transfer
   apply (auto simp add: image_iff)
   apply (metis take_bit_int_eq_self_iff)
   done
 
 lemma UNIV_eq: \<open>(UNIV :: 'a word set) = word_of_int ` {0..<2 ^ LENGTH('a::len)}\<close>
   by (auto simp add: image_iff) (metis atLeastLessThan_iff linorder_not_le uint_split)
 
 lemma card_word: "CARD('a word) = 2 ^ LENGTH('a::len)"
   by (simp add: UNIV_eq card_image inj_on_word_of_int)
 
 lemma card_word_size: "CARD('a word) = 2 ^ size x"
   for x :: "'a::len word"
   unfolding word_size by (rule card_word)
 
 end
 
 instance word :: (len) finite
   by standard (simp add: UNIV_eq)
 
 
 subsection \<open>Bitwise Operations on Words\<close>
 
 context
   includes bit_operations_syntax
 begin
 
 lemma word_wi_log_defs:
   "NOT (word_of_int a) = word_of_int (NOT a)"
   "word_of_int a AND word_of_int b = word_of_int (a AND b)"
   "word_of_int a OR word_of_int b = word_of_int (a OR b)"
   "word_of_int a XOR word_of_int b = word_of_int (a XOR b)"
   by (transfer, rule refl)+
 
 lemma word_no_log_defs [simp]:
   "NOT (numeral a) = word_of_int (NOT (numeral a))"
   "NOT (- numeral a) = word_of_int (NOT (- numeral a))"
   "numeral a AND numeral b = word_of_int (numeral a AND numeral b)"
   "numeral a AND - numeral b = word_of_int (numeral a AND - numeral b)"
   "- numeral a AND numeral b = word_of_int (- numeral a AND numeral b)"
   "- numeral a AND - numeral b = word_of_int (- numeral a AND - numeral b)"
   "numeral a OR numeral b = word_of_int (numeral a OR numeral b)"
   "numeral a OR - numeral b = word_of_int (numeral a OR - numeral b)"
   "- numeral a OR numeral b = word_of_int (- numeral a OR numeral b)"
   "- numeral a OR - numeral b = word_of_int (- numeral a OR - numeral b)"
   "numeral a XOR numeral b = word_of_int (numeral a XOR numeral b)"
   "numeral a XOR - numeral b = word_of_int (numeral a XOR - numeral b)"
   "- numeral a XOR numeral b = word_of_int (- numeral a XOR numeral b)"
   "- numeral a XOR - numeral b = word_of_int (- numeral a XOR - numeral b)"
   by (transfer, rule refl)+
 
 text \<open>Special cases for when one of the arguments equals 1.\<close>
 
 lemma word_bitwise_1_simps [simp]:
   "NOT (1::'a::len word) = -2"
   "1 AND numeral b = word_of_int (1 AND numeral b)"
   "1 AND - numeral b = word_of_int (1 AND - numeral b)"
   "numeral a AND 1 = word_of_int (numeral a AND 1)"
   "- numeral a AND 1 = word_of_int (- numeral a AND 1)"
   "1 OR numeral b = word_of_int (1 OR numeral b)"
   "1 OR - numeral b = word_of_int (1 OR - numeral b)"
   "numeral a OR 1 = word_of_int (numeral a OR 1)"
   "- numeral a OR 1 = word_of_int (- numeral a OR 1)"
   "1 XOR numeral b = word_of_int (1 XOR numeral b)"
   "1 XOR - numeral b = word_of_int (1 XOR - numeral b)"
   "numeral a XOR 1 = word_of_int (numeral a XOR 1)"
   "- numeral a XOR 1 = word_of_int (- numeral a XOR 1)"
               apply (simp_all add: word_uint_eq_iff unsigned_not_eq unsigned_and_eq unsigned_or_eq unsigned_xor_eq not_one_eq of_nat_take_bit ac_simps)
        apply (simp_all add: minus_numeral_eq_not_sub_one)
    apply (simp_all only: sub_one_eq_not_neg bit.xor_compl_right take_bit_xor bit.double_compl)
    apply simp_all
   done
 
 text \<open>Special cases for when one of the arguments equals -1.\<close>
 
 lemma word_bitwise_m1_simps [simp]:
   "NOT (-1::'a::len word) = 0"
   "(-1::'a::len word) AND x = x"
   "x AND (-1::'a::len word) = x"
   "(-1::'a::len word) OR x = -1"
   "x OR (-1::'a::len word) = -1"
   " (-1::'a::len word) XOR x = NOT x"
   "x XOR (-1::'a::len word) = NOT x"
   by (transfer, simp)+
 
 lemma word_of_int_not_numeral_eq [simp]:
   \<open>(word_of_int (NOT (numeral bin)) :: 'a::len word) = - numeral bin - 1\<close>
   by transfer (simp add: not_eq_complement)
 
 lemma uint_and:
   \<open>uint (x AND y) = uint x AND uint y\<close>
   by transfer simp
 
 lemma uint_or:
   \<open>uint (x OR y) = uint x OR uint y\<close>
   by transfer simp
 
 lemma uint_xor:
   \<open>uint (x XOR y) = uint x XOR uint y\<close>
   by transfer simp
 
 \<comment> \<open>get from commutativity, associativity etc of \<open>int_and\<close> etc to same for \<open>word_and etc\<close>\<close>
 lemmas bwsimps =
   wi_hom_add
   word_wi_log_defs
 
 lemma word_bw_assocs:
   "(x AND y) AND z = x AND y AND z"
   "(x OR y) OR z = x OR y OR z"
   "(x XOR y) XOR z = x XOR y XOR z"
   for x :: "'a::len word"
   by (fact ac_simps)+
 
 lemma word_bw_comms:
   "x AND y = y AND x"
   "x OR y = y OR x"
   "x XOR y = y XOR x"
   for x :: "'a::len word"
   by (fact ac_simps)+
 
 lemma word_bw_lcs:
   "y AND x AND z = x AND y AND z"
   "y OR x OR z = x OR y OR z"
   "y XOR x XOR z = x XOR y XOR z"
   for x :: "'a::len word"
   by (fact ac_simps)+
 
 lemma word_log_esimps:
   "x AND 0 = 0"
   "x AND -1 = x"
   "x OR 0 = x"
   "x OR -1 = -1"
   "x XOR 0 = x"
   "x XOR -1 = NOT x"
   "0 AND x = 0"
   "-1 AND x = x"
   "0 OR x = x"
   "-1 OR x = -1"
   "0 XOR x = x"
   "-1 XOR x = NOT x"
   for x :: "'a::len word"
   by simp_all
 
 lemma word_not_dist:
   "NOT (x OR y) = NOT x AND NOT y"
   "NOT (x AND y) = NOT x OR NOT y"
   for x :: "'a::len word"
   by simp_all
 
 lemma word_bw_same:
   "x AND x = x"
   "x OR x = x"
   "x XOR x = 0"
   for x :: "'a::len word"
   by simp_all
 
 lemma word_ao_absorbs [simp]:
   "x AND (y OR x) = x"
   "x OR y AND x = x"
   "x AND (x OR y) = x"
   "y AND x OR x = x"
   "(y OR x) AND x = x"
   "x OR x AND y = x"
   "(x OR y) AND x = x"
   "x AND y OR x = x"
   for x :: "'a::len word"
   by (auto intro: bit_eqI simp add: bit_and_iff bit_or_iff)
 
 lemma word_not_not [simp]: "NOT (NOT x) = x"
   for x :: "'a::len word"
   by (fact bit.double_compl)
 
 lemma word_ao_dist: "(x OR y) AND z = x AND z OR y AND z"
   for x :: "'a::len word"
   by (fact bit.conj_disj_distrib2)
 
 lemma word_oa_dist: "x AND y OR z = (x OR z) AND (y OR z)"
   for x :: "'a::len word"
   by (fact bit.disj_conj_distrib2)
   
 lemma word_add_not [simp]: "x + NOT x = -1"
   for x :: "'a::len word"
   by (simp add: not_eq_complement)
   
 lemma word_plus_and_or [simp]: "(x AND y) + (x OR y) = x + y"
   for x :: "'a::len word"
   by transfer (simp add: plus_and_or)
 
 lemma leoa: "w = x OR y \<Longrightarrow> y = w AND y"
   for x :: "'a::len word"
   by auto
 
 lemma leao: "w' = x' AND y' \<Longrightarrow> x' = x' OR w'"
   for x' :: "'a::len word"
   by auto
 
 lemma word_ao_equiv: "w = w OR w' \<longleftrightarrow> w' = w AND w'"
   for w w' :: "'a::len word"
   by (auto intro: leoa leao)
 
 lemma le_word_or2: "x \<le> x OR y"
   for x y :: "'a::len word"
   by (simp add: or_greater_eq uint_or word_le_def)
 
 lemmas le_word_or1 = xtrans(3) [OF word_bw_comms (2) le_word_or2]
 lemmas word_and_le1 = xtrans(3) [OF word_ao_absorbs (4) [symmetric] le_word_or2]
 lemmas word_and_le2 = xtrans(3) [OF word_ao_absorbs (8) [symmetric] le_word_or2]
 
 lemma bit_horner_sum_bit_word_iff [bit_simps]:
   \<open>bit (horner_sum of_bool (2 :: 'a::len word) bs) n
     \<longleftrightarrow> n < min LENGTH('a) (length bs) \<and> bs ! n\<close>
   by transfer (simp add: bit_horner_sum_bit_iff)
 
 definition word_reverse :: \<open>'a::len word \<Rightarrow> 'a word\<close>
   where \<open>word_reverse w = horner_sum of_bool 2 (rev (map (bit w) [0..<LENGTH('a)]))\<close>
 
 lemma bit_word_reverse_iff [bit_simps]:
   \<open>bit (word_reverse w) n \<longleftrightarrow> n < LENGTH('a) \<and> bit w (LENGTH('a) - Suc n)\<close>
   for w :: \<open>'a::len word\<close>
   by (cases \<open>n < LENGTH('a)\<close>)
     (simp_all add: word_reverse_def bit_horner_sum_bit_word_iff rev_nth)
 
 lemma word_rev_rev [simp] : "word_reverse (word_reverse w) = w"
   by (rule bit_word_eqI)
     (auto simp add: bit_word_reverse_iff bit_imp_le_length Suc_diff_Suc)
 
 lemma word_rev_gal: "word_reverse w = u \<Longrightarrow> word_reverse u = w"
   by (metis word_rev_rev)
 
 lemma word_rev_gal': "u = word_reverse w \<Longrightarrow> w = word_reverse u"
   by simp
 
 lemma uint_2p: "(0::'a::len word) < 2 ^ n \<Longrightarrow> uint (2 ^ n::'a::len word) = 2 ^ n"
   by (cases \<open>n < LENGTH('a)\<close>; transfer; force)
 
 lemma word_of_int_2p: "(word_of_int (2 ^ n) :: 'a::len word) = 2 ^ n"
   by (induct n) (simp_all add: wi_hom_syms)
 
 
 subsubsection \<open>shift functions in terms of lists of bools\<close>
 
 text \<open>TODO: rules for \<^term>\<open>- (numeral n)\<close>\<close>
 
 lemma drop_bit_word_numeral [simp]:
   \<open>drop_bit (numeral n) (numeral k) =
     (word_of_int (drop_bit (numeral n) (take_bit LENGTH('a) (numeral k))) :: 'a::len word)\<close>
   by transfer simp
 
 lemma signed_drop_bit_word_numeral [simp]:
   \<open>signed_drop_bit (numeral n) (numeral k) =
     (word_of_int (drop_bit (numeral n) (signed_take_bit (LENGTH('a) - 1) (numeral k))) :: 'a::len word)\<close>
   by transfer simp
 
 lemma False_map2_or: "\<lbrakk>set xs \<subseteq> {False}; length ys = length xs\<rbrakk> \<Longrightarrow> map2 (\<or>) xs ys = ys"
   by (induction xs arbitrary: ys) (auto simp: length_Suc_conv)
 
 lemma align_lem_or:
   assumes "length xs = n + m" "length ys = n + m" 
     and "drop m xs = replicate n False" "take m ys = replicate m False"
   shows "map2 (\<or>) xs ys = take m xs @ drop m ys"
   using assms
 proof (induction xs arbitrary: ys m)
   case (Cons a xs)
   then show ?case
     by (cases m) (auto simp: length_Suc_conv False_map2_or)
 qed auto
 
 lemma False_map2_and: "\<lbrakk>set xs \<subseteq> {False}; length ys = length xs\<rbrakk> \<Longrightarrow> map2 (\<and>) xs ys = xs"
   by (induction xs arbitrary: ys) (auto simp: length_Suc_conv)
 
 lemma align_lem_and:
   assumes "length xs = n + m" "length ys = n + m" 
     and "drop m xs = replicate n False" "take m ys = replicate m False"
   shows "map2 (\<and>) xs ys = replicate (n + m) False"
   using assms
 proof (induction xs arbitrary: ys m)
   case (Cons a xs)
   then show ?case
     by (cases m) (auto simp: length_Suc_conv set_replicate_conv_if False_map2_and)
 qed auto
 
 
 subsubsection \<open>Mask\<close>
 
 lemma minus_1_eq_mask:
   \<open>- 1 = (mask LENGTH('a) :: 'a::len word)\<close>
   by (rule bit_eqI) (simp add: bit_exp_iff bit_mask_iff)
 
 lemma mask_eq_decr_exp:
   \<open>mask n = 2 ^ n - (1 :: 'a::len word)\<close>
   by (fact mask_eq_exp_minus_1)
 
 lemma mask_Suc_rec:
   \<open>mask (Suc n) = 2 * mask n + (1 :: 'a::len word)\<close>
   by (simp add: mask_eq_exp_minus_1)
 
 context
 begin
 
 qualified lemma bit_mask_iff [bit_simps]:
   \<open>bit (mask m :: 'a::len word) n \<longleftrightarrow> n < min LENGTH('a) m\<close>
   by (simp add: bit_mask_iff not_le)
 
 end
 
 lemma mask_bin: "mask n = word_of_int (take_bit n (- 1))"
   by transfer (simp add: take_bit_minus_one_eq_mask) 
 
 lemma and_mask_bintr: "w AND mask n = word_of_int (take_bit n (uint w))"
   by transfer (simp add: ac_simps take_bit_eq_mask)
 
 lemma and_mask_wi: "word_of_int i AND mask n = word_of_int (take_bit n i)"
   by (auto simp add: and_mask_bintr min_def not_le wi_bintr)
 
 lemma and_mask_wi':
   "word_of_int i AND mask n = (word_of_int (take_bit (min LENGTH('a) n) i) :: 'a::len word)"
   by (auto simp add: and_mask_wi min_def wi_bintr)
 
 lemma and_mask_no: "numeral i AND mask n = word_of_int (take_bit n (numeral i))"
   unfolding word_numeral_alt by (rule and_mask_wi)
 
 lemma and_mask_mod_2p: "w AND mask n = word_of_int (uint w mod 2 ^ n)"
   by (simp only: and_mask_bintr take_bit_eq_mod)
 
 lemma uint_mask_eq:
   \<open>uint (mask n :: 'a::len word) = mask (min LENGTH('a) n)\<close>
   by transfer simp
 
 lemma and_mask_lt_2p: "uint (w AND mask n) < 2 ^ n"
   by (metis take_bit_eq_mask take_bit_int_less_exp unsigned_take_bit_eq)
 
 lemma mask_eq_iff: "w AND mask n = w \<longleftrightarrow> uint w < 2 ^ n"
   apply (auto simp flip: take_bit_eq_mask)
    apply (metis take_bit_int_eq_self_iff uint_take_bit_eq)
   apply (simp add: take_bit_int_eq_self unsigned_take_bit_eq word_uint_eqI)
   done
 
 lemma and_mask_dvd: "2 ^ n dvd uint w \<longleftrightarrow> w AND mask n = 0"
   by (simp flip: take_bit_eq_mask take_bit_eq_mod unsigned_take_bit_eq add: dvd_eq_mod_eq_0 uint_0_iff)
 
 lemma and_mask_dvd_nat: "2 ^ n dvd unat w \<longleftrightarrow> w AND mask n = 0"
   by (simp flip: take_bit_eq_mask take_bit_eq_mod unsigned_take_bit_eq add: dvd_eq_mod_eq_0 unat_0_iff uint_0_iff)
 
 lemma word_2p_lem: "n < size w \<Longrightarrow> w < 2 ^ n = (uint w < 2 ^ n)"
   for w :: "'a::len word"
   by transfer simp
 
 lemma less_mask_eq:
   fixes x :: "'a::len word"
   assumes "x < 2 ^ n" shows "x AND mask n = x"
   by (metis (no_types) assms lt2p_lem mask_eq_iff not_less word_2p_lem word_size)
 
 lemmas mask_eq_iff_w2p = trans [OF mask_eq_iff word_2p_lem [symmetric]]
 
 lemmas and_mask_less' = iffD2 [OF word_2p_lem and_mask_lt_2p, simplified word_size]
 
 lemma and_mask_less_size: "n < size x \<Longrightarrow> x AND mask n < 2 ^ n"
   for x :: \<open>'a::len word\<close>
   unfolding word_size by (erule and_mask_less')
 
 lemma word_mod_2p_is_mask [OF refl]: "c = 2 ^ n \<Longrightarrow> c > 0 \<Longrightarrow> x mod c = x AND mask n"
   for c x :: "'a::len word"
   by (auto simp: word_mod_def uint_2p and_mask_mod_2p)
 
 lemma mask_eqs:
   "(a AND mask n) + b AND mask n = a + b AND mask n"
   "a + (b AND mask n) AND mask n = a + b AND mask n"
   "(a AND mask n) - b AND mask n = a - b AND mask n"
   "a - (b AND mask n) AND mask n = a - b AND mask n"
   "a * (b AND mask n) AND mask n = a * b AND mask n"
   "(b AND mask n) * a AND mask n = b * a AND mask n"
   "(a AND mask n) + (b AND mask n) AND mask n = a + b AND mask n"
   "(a AND mask n) - (b AND mask n) AND mask n = a - b AND mask n"
   "(a AND mask n) * (b AND mask n) AND mask n = a * b AND mask n"
   "- (a AND mask n) AND mask n = - a AND mask n"
   "word_succ (a AND mask n) AND mask n = word_succ a AND mask n"
   "word_pred (a AND mask n) AND mask n = word_pred a AND mask n"
   using word_of_int_Ex [where x=a] word_of_int_Ex [where x=b]
   unfolding take_bit_eq_mask [symmetric]
   by (transfer; simp add: take_bit_eq_mod mod_simps)+
 
 lemma mask_power_eq: "(x AND mask n) ^ k AND mask n = x ^ k AND mask n"
   for x :: \<open>'a::len word\<close>
   using word_of_int_Ex [where x=x]
   unfolding take_bit_eq_mask [symmetric]
   by (transfer; simp add: take_bit_eq_mod mod_simps)+
 
 lemma mask_full [simp]: "mask LENGTH('a) = (- 1 :: 'a::len word)"
   by transfer (simp add: take_bit_minus_one_eq_mask)
 
 
 subsubsection \<open>Slices\<close>
 
 definition slice1 :: \<open>nat \<Rightarrow> 'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>slice1 n w = (if n < LENGTH('a)
     then ucast (drop_bit (LENGTH('a) - n) w)
     else push_bit (n - LENGTH('a)) (ucast w))\<close>
 
 lemma bit_slice1_iff [bit_simps]:
   \<open>bit (slice1 m w :: 'b::len word) n \<longleftrightarrow> m - LENGTH('a) \<le> n \<and> n < min LENGTH('b) m
     \<and> bit w (n + (LENGTH('a) - m) - (m - LENGTH('a)))\<close>
   for w :: \<open>'a::len word\<close>
   by (auto simp add: slice1_def bit_ucast_iff bit_drop_bit_eq bit_push_bit_iff not_less not_le ac_simps
     dest: bit_imp_le_length)
 
 definition slice :: \<open>nat \<Rightarrow> 'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>slice n = slice1 (LENGTH('a) - n)\<close>
 
 lemma bit_slice_iff [bit_simps]:
   \<open>bit (slice m w :: 'b::len word) n \<longleftrightarrow> n < min LENGTH('b) (LENGTH('a) - m) \<and> bit w (n + LENGTH('a) - (LENGTH('a) - m))\<close>
   for w :: \<open>'a::len word\<close>
   by (simp add: slice_def word_size bit_slice1_iff)
 
 lemma slice1_0 [simp] : "slice1 n 0 = 0"
   unfolding slice1_def by simp
 
 lemma slice_0 [simp] : "slice n 0 = 0"
   unfolding slice_def by auto
 
 lemma ucast_slice1: "ucast w = slice1 (size w) w"
   unfolding slice1_def by (simp add: size_word.rep_eq)
 
 lemma ucast_slice: "ucast w = slice 0 w"
   by (simp add: slice_def slice1_def)
 
 lemma slice_id: "slice 0 t = t"
   by (simp only: ucast_slice [symmetric] ucast_id)
 
 lemma rev_slice1:
   \<open>slice1 n (word_reverse w :: 'b::len word) = word_reverse (slice1 k w :: 'a::len word)\<close>
   if \<open>n + k = LENGTH('a) + LENGTH('b)\<close>
 proof (rule bit_word_eqI)
   fix m
   assume *: \<open>m < LENGTH('a)\<close>
   from that have **: \<open>LENGTH('b) = n + k - LENGTH('a)\<close>
     by simp
   show \<open>bit (slice1 n (word_reverse w :: 'b word) :: 'a word) m \<longleftrightarrow> bit (word_reverse (slice1 k w :: 'a word)) m\<close>
     unfolding bit_slice1_iff bit_word_reverse_iff
     using * **
     by (cases \<open>n \<le> LENGTH('a)\<close>; cases \<open>k \<le> LENGTH('a)\<close>) auto
 qed
 
 lemma rev_slice:
   "n + k + LENGTH('a::len) = LENGTH('b::len) \<Longrightarrow>
     slice n (word_reverse (w::'b word)) = word_reverse (slice k w :: 'a word)"
   unfolding slice_def word_size
   by (simp add: rev_slice1)
 
 
 subsubsection \<open>Revcast\<close>
 
 definition revcast :: \<open>'a::len word \<Rightarrow> 'b::len word\<close>
   where \<open>revcast = slice1 LENGTH('b)\<close>
 
 lemma bit_revcast_iff [bit_simps]:
   \<open>bit (revcast w :: 'b::len word) n \<longleftrightarrow> LENGTH('b) - LENGTH('a) \<le> n \<and> n < LENGTH('b)
     \<and> bit w (n + (LENGTH('a) - LENGTH('b)) - (LENGTH('b) - LENGTH('a)))\<close>
   for w :: \<open>'a::len word\<close>
   by (simp add: revcast_def bit_slice1_iff)
 
 lemma revcast_slice1 [OF refl]: "rc = revcast w \<Longrightarrow> slice1 (size rc) w = rc"
   by (simp add: revcast_def word_size)
 
 lemma revcast_rev_ucast [OF refl refl refl]:
   "cs = [rc, uc] \<Longrightarrow> rc = revcast (word_reverse w) \<Longrightarrow> uc = ucast w \<Longrightarrow>
     rc = word_reverse uc"
   by (metis rev_slice1 revcast_slice1 ucast_slice1 word_size)
 
 lemma revcast_ucast: "revcast w = word_reverse (ucast (word_reverse w))"
   using revcast_rev_ucast [of "word_reverse w"] by simp
 
 lemma ucast_revcast: "ucast w = word_reverse (revcast (word_reverse w))"
   by (fact revcast_rev_ucast [THEN word_rev_gal'])
 
 lemma ucast_rev_revcast: "ucast (word_reverse w) = word_reverse (revcast w)"
   by (fact revcast_ucast [THEN word_rev_gal'])
 
 
 text "linking revcast and cast via shift"
 
 lemmas wsst_TYs = source_size target_size word_size
 
 lemmas sym_notr =
   not_iff [THEN iffD2, THEN not_sym, THEN not_iff [THEN iffD1]]
 
 
 subsection \<open>Split and cat\<close>
 
 lemmas word_split_bin' = word_split_def
 lemmas word_cat_bin' = word_cat_eq
 
 \<comment> \<open>this odd result is analogous to \<open>ucast_id\<close>,
       result to the length given by the result type\<close>
 
 lemma word_cat_id: "word_cat a b = b"
   by transfer (simp add: take_bit_concat_bit_eq)
 
 lemma word_cat_split_alt: "\<lbrakk>size w \<le> size u + size v; word_split w = (u,v)\<rbrakk> \<Longrightarrow> word_cat u v = w"
   unfolding word_split_def
   by (rule bit_word_eqI) (auto simp add: bit_word_cat_iff not_less word_size bit_ucast_iff bit_drop_bit_eq)
 
 lemmas word_cat_split_size = sym [THEN [2] word_cat_split_alt [symmetric]]
 
 
 subsubsection \<open>Split and slice\<close>
 
 lemma split_slices:
   assumes "word_split w = (u, v)"
   shows "u = slice (size v) w \<and> v = slice 0 w"
   unfolding word_size
 proof (intro conjI)
   have \<section>: "\<And>n. \<lbrakk>ucast (drop_bit LENGTH('b) w) = u; LENGTH('c) < LENGTH('b)\<rbrakk> \<Longrightarrow> \<not> bit u n"
     by (metis bit_take_bit_iff bit_word_of_int_iff diff_is_0_eq' drop_bit_take_bit less_imp_le less_nat_zero_code of_int_uint unsigned_drop_bit_eq)
   show "u = slice LENGTH('b) w"
   proof (rule bit_word_eqI)
     show "bit u n = bit ((slice LENGTH('b) w)::'a word) n" if "n < LENGTH('a)" for n
       using assms bit_imp_le_length
       unfolding word_split_def bit_slice_iff
       by (fastforce simp add: \<section> ac_simps word_size bit_ucast_iff bit_drop_bit_eq)
   qed
   show "v = slice 0 w"
     by (metis Pair_inject assms ucast_slice word_split_bin')
 qed
 
 
 lemma slice_cat1 [OF refl]:
   "\<lbrakk>wc = word_cat a b; size a + size b \<le> size wc\<rbrakk> \<Longrightarrow> slice (size b) wc = a"
   by (rule bit_word_eqI) (auto simp add: bit_slice_iff bit_word_cat_iff word_size)
 
 lemmas slice_cat2 = trans [OF slice_id word_cat_id]
 
 lemma cat_slices:
   "\<lbrakk>a = slice n c; b = slice 0 c; n = size b; size c \<le> size a + size b\<rbrakk> \<Longrightarrow> word_cat a b = c"
   by (rule bit_word_eqI) (auto simp add: bit_slice_iff bit_word_cat_iff word_size)
 
 lemma word_split_cat_alt:
   assumes "w = word_cat u v" and size: "size u + size v \<le> size w"
   shows "word_split w = (u,v)"
 proof -
   have "ucast ((drop_bit LENGTH('c) (word_cat u v))::'a word) = u" "ucast ((word_cat u v)::'a word) = v"
     using assms
     by (auto simp add: word_size bit_ucast_iff bit_drop_bit_eq bit_word_cat_iff intro: bit_eqI)
   then show ?thesis
     by (simp add: assms(1) word_split_bin')
 qed
 
 lemma horner_sum_uint_exp_Cons_eq:
   \<open>horner_sum uint (2 ^ LENGTH('a)) (w # ws) =
     concat_bit LENGTH('a) (uint w) (horner_sum uint (2 ^ LENGTH('a)) ws)\<close>
   for ws :: \<open>'a::len word list\<close>
   by (simp add: bintr_uint concat_bit_eq push_bit_eq_mult)
 
 lemma bit_horner_sum_uint_exp_iff:
   \<open>bit (horner_sum uint (2 ^ LENGTH('a)) ws) n \<longleftrightarrow>
     n div LENGTH('a) < length ws \<and> bit (ws ! (n div LENGTH('a))) (n mod LENGTH('a))\<close>
   for ws :: \<open>'a::len word list\<close>
 proof (induction ws arbitrary: n)
   case Nil
   then show ?case
     by simp
 next
   case (Cons w ws)
   then show ?case
     by (cases \<open>n \<ge> LENGTH('a)\<close>)
       (simp_all only: horner_sum_uint_exp_Cons_eq, simp_all add: bit_concat_bit_iff le_div_geq le_mod_geq bit_uint_iff Cons)
 qed
 
 
 subsection \<open>Rotation\<close>
 
 lemma word_rotr_word_rotr_eq: \<open>word_rotr m (word_rotr n w) = word_rotr (m + n) w\<close>
   by (rule bit_word_eqI) (simp add: bit_word_rotr_iff ac_simps mod_add_right_eq)
 
 lemma word_rot_lem: "\<lbrakk>l + k = d + k mod l; n < l\<rbrakk> \<Longrightarrow> ((d + n) mod l) = n" for l::nat
   by (metis (no_types, lifting) add.commute add.right_neutral add_diff_cancel_left' mod_if mod_mult_div_eq mod_mult_self2 mod_self)
  
 lemma word_rot_rl [simp]: \<open>word_rotl k (word_rotr k v) = v\<close>
 proof (rule bit_word_eqI)
   show "bit (word_rotl k (word_rotr k v)) n = bit v n" if "n < LENGTH('a)" for n
     using that
     by (auto simp: word_rot_lem word_rotl_eq_word_rotr word_rotr_word_rotr_eq bit_word_rotr_iff algebra_simps split: nat_diff_split)
 qed
 
 lemma word_rot_lr [simp]: \<open>word_rotr k (word_rotl k v) = v\<close>
 proof (rule bit_word_eqI)
   show "bit (word_rotr k (word_rotl k v)) n = bit v n" if "n < LENGTH('a)" for n
     using that
     by (auto simp add: word_rot_lem word_rotl_eq_word_rotr word_rotr_word_rotr_eq bit_word_rotr_iff algebra_simps split: nat_diff_split)
 qed
 
 lemma word_rot_gal:
   \<open>word_rotr n v = w \<longleftrightarrow> word_rotl n w = v\<close>
   by auto
 
 lemma word_rot_gal':
   \<open>w = word_rotr n v \<longleftrightarrow> v = word_rotl n w\<close>
   by auto
 
 lemma word_rotr_rev:
   \<open>word_rotr n w = word_reverse (word_rotl n (word_reverse w))\<close>
 proof (rule bit_word_eqI)
   fix m
   assume \<open>m < LENGTH('a)\<close>
   moreover have \<open>1 +
     ((int m + int n mod int LENGTH('a)) mod int LENGTH('a) +
      ((int LENGTH('a) * 2) mod int LENGTH('a) - (1 + (int m + int n mod int LENGTH('a)))) mod int LENGTH('a)) =
     int LENGTH('a)\<close>
     apply (cases \<open>(1 + (int m + int n mod int LENGTH('a))) mod
          int LENGTH('a) = 0\<close>)
     using zmod_zminus1_eq_if [of \<open>1 + (int m + int n mod int LENGTH('a))\<close> \<open>int LENGTH('a)\<close>]
     apply simp_all
      apply (auto simp add: algebra_simps)
     apply (metis (mono_tags, opaque_lifting) Abs_fnat_hom_add mod_Suc mod_mult_self2_is_0 of_nat_Suc of_nat_mod semiring_char_0_class.of_nat_neq_0)
     apply (metis (no_types, opaque_lifting) Abs_fnat_hom_add less_not_refl mod_Suc of_nat_Suc of_nat_gt_0 of_nat_mod)
     done
   then have \<open>int ((m + n) mod LENGTH('a)) =
     int (LENGTH('a) - Suc ((LENGTH('a) - Suc m + LENGTH('a) - n mod LENGTH('a)) mod LENGTH('a)))\<close>
     using \<open>m < LENGTH('a)\<close>
     by (simp only: of_nat_mod mod_simps)
       (simp add: of_nat_diff of_nat_mod Suc_le_eq add_less_mono algebra_simps mod_simps)
   then have \<open>(m + n) mod LENGTH('a) =
     LENGTH('a) - Suc ((LENGTH('a) - Suc m + LENGTH('a) - n mod LENGTH('a)) mod LENGTH('a))\<close>
     by simp
   ultimately show \<open>bit (word_rotr n w) m \<longleftrightarrow> bit (word_reverse (word_rotl n (word_reverse w))) m\<close>
     by (simp add: word_rotl_eq_word_rotr bit_word_rotr_iff bit_word_reverse_iff)
 qed
 
 lemma word_roti_0 [simp]: "word_roti 0 w = w"
   by transfer simp
 
 lemma word_roti_add: "word_roti (m + n) w = word_roti m (word_roti n w)"
   by (rule bit_word_eqI)
     (simp add: bit_word_roti_iff nat_less_iff mod_simps ac_simps)
 
 lemma word_roti_conv_mod':
   "word_roti n w = word_roti (n mod int (size w)) w"
   by transfer simp
 
 lemmas word_roti_conv_mod = word_roti_conv_mod' [unfolded word_size]
 
 end
 
 
 subsubsection \<open>"Word rotation commutes with bit-wise operations\<close>
 
 \<comment> \<open>using locale to not pollute lemma namespace\<close>
 locale word_rotate
 begin
 
 context
   includes bit_operations_syntax
 begin
 
 lemma word_rot_logs:
   "word_rotl n (NOT v) = NOT (word_rotl n v)"
   "word_rotr n (NOT v) = NOT (word_rotr n v)"
   "word_rotl n (x AND y) = word_rotl n x AND word_rotl n y"
   "word_rotr n (x AND y) = word_rotr n x AND word_rotr n y"
   "word_rotl n (x OR y) = word_rotl n x OR word_rotl n y"
   "word_rotr n (x OR y) = word_rotr n x OR word_rotr n y"
   "word_rotl n (x XOR y) = word_rotl n x XOR word_rotl n y"
   "word_rotr n (x XOR y) = word_rotr n x XOR word_rotr n y"
   by (rule bit_word_eqI, auto simp add: bit_word_rotl_iff bit_word_rotr_iff bit_and_iff bit_or_iff bit_xor_iff bit_not_iff algebra_simps not_le)+
 
 end
 
 end
 
 lemmas word_rot_logs = word_rotate.word_rot_logs
 
 lemma word_rotx_0 [simp] : "word_rotr i 0 = 0 \<and> word_rotl i 0 = 0"
   by transfer simp_all
 
 lemma word_roti_0' [simp] : "word_roti n 0 = 0"
   by transfer simp
 
 declare word_roti_eq_word_rotr_word_rotl [simp]
 
 
 subsection \<open>Maximum machine word\<close>
 
 context
   includes bit_operations_syntax
 begin
 
 lemma word_int_cases:
   fixes x :: "'a::len word"
   obtains n where "x = word_of_int n" and "0 \<le> n" and "n < 2^LENGTH('a)"
   by (rule that [of \<open>uint x\<close>]) simp_all
 
 lemma word_nat_cases [cases type: word]:
   fixes x :: "'a::len word"
   obtains n where "x = of_nat n" and "n < 2^LENGTH('a)"
   by (rule that [of \<open>unat x\<close>]) simp_all
 
 lemma max_word_max [intro!]:
   \<open>n \<le> - 1\<close> for n :: \<open>'a::len word\<close>
   by (fact word_order.extremum)
 
 lemma word_of_int_2p_len: "word_of_int (2 ^ LENGTH('a)) = (0::'a::len word)"
   by simp
 
 lemma word_pow_0: "(2::'a::len word) ^ LENGTH('a) = 0"
   by (fact word_exp_length_eq_0)
 
 lemma max_word_wrap: 
   \<open>x + 1 = 0 \<Longrightarrow> x = - 1\<close> for x :: \<open>'a::len word\<close>
   by (simp add: eq_neg_iff_add_eq_0)
 
 lemma word_and_max:
   \<open>x AND - 1 = x\<close> for x :: \<open>'a::len word\<close>
   by (fact word_log_esimps)
 
 lemma word_or_max:
   \<open>x OR - 1 = - 1\<close> for x :: \<open>'a::len word\<close>
   by (fact word_log_esimps)
 
 lemma word_ao_dist2: "x AND (y OR z) = x AND y OR x AND z"
   for x y z :: "'a::len word"
   by (fact bit.conj_disj_distrib)
 
 lemma word_oa_dist2: "x OR y AND z = (x OR y) AND (x OR z)"
   for x y z :: "'a::len word"
   by (fact bit.disj_conj_distrib)
 
 lemma word_and_not [simp]: "x AND NOT x = 0"
   for x :: "'a::len word"
   by (fact bit.conj_cancel_right)
 
 lemma word_or_not [simp]:
   \<open>x OR NOT x = - 1\<close> for x :: \<open>'a::len word\<close>
   by (fact bit.disj_cancel_right)
 
 lemma word_xor_and_or: "x XOR y = x AND NOT y OR NOT x AND y"
   for x y :: "'a::len word"
   by (fact bit.xor_def)
 
 lemma uint_lt_0 [simp]: "uint x < 0 = False"
   by (simp add: linorder_not_less)
 
 lemma word_less_1 [simp]: "x < 1 \<longleftrightarrow> x = 0"
   for x :: "'a::len word"
   by (simp add: word_less_nat_alt unat_0_iff)
 
 lemma uint_plus_if_size:
   "uint (x + y) =
     (if uint x + uint y < 2^size x
      then uint x + uint y
      else uint x + uint y - 2^size x)"
   by (simp add: take_bit_eq_mod word_size uint_word_of_int_eq uint_plus_if')
 
 lemma unat_plus_if_size:
   "unat (x + y) =
     (if unat x + unat y < 2^size x
      then unat x + unat y
      else unat x + unat y - 2^size x)"
   for x y :: "'a::len word"
   by (simp add: size_word.rep_eq unat_arith_simps)
 
 lemma word_neq_0_conv: "w \<noteq> 0 \<longleftrightarrow> 0 < w"
   for w :: "'a::len word"
   by (fact word_coorder.not_eq_extremum)
 
 lemma max_lt: "unat (max a b div c) = unat (max a b) div unat c"
   for c :: "'a::len word"
   by (fact unat_div)
 
 lemma uint_sub_if_size:
   "uint (x - y) =
     (if uint y \<le> uint x
      then uint x - uint y
      else uint x - uint y + 2^size x)"
   by (simp add: size_word.rep_eq uint_sub_if')
 
 lemma unat_sub:
   \<open>unat (a - b) = unat a - unat b\<close>
   if \<open>b \<le> a\<close>
   by (meson that unat_sub_if_size word_le_nat_alt)
 
 lemmas word_less_sub1_numberof [simp] = word_less_sub1 [of "numeral w"] for w
 lemmas word_le_sub1_numberof [simp] = word_le_sub1 [of "numeral w"] for w
 
 lemma word_of_int_minus: "word_of_int (2^LENGTH('a) - i) = (word_of_int (-i)::'a::len word)"
   by simp
 
 lemma word_of_int_inj:
   \<open>(word_of_int x :: 'a::len word) = word_of_int y \<longleftrightarrow> x = y\<close>
   if \<open>0 \<le> x \<and> x < 2 ^ LENGTH('a)\<close> \<open>0 \<le> y \<and> y < 2 ^ LENGTH('a)\<close>
   using that by (transfer fixing: x y) (simp add: take_bit_int_eq_self) 
 
 lemma word_le_less_eq: "x \<le> y \<longleftrightarrow> x = y \<or> x < y"
   for x y :: "'z::len word"
   by (auto simp add: order_class.le_less)
 
 lemma mod_plus_cong:
   fixes b b' :: int
   assumes 1: "b = b'"
     and 2: "x mod b' = x' mod b'"
     and 3: "y mod b' = y' mod b'"
     and 4: "x' + y' = z'"
   shows "(x + y) mod b = z' mod b'"
 proof -
   from 1 2[symmetric] 3[symmetric] have "(x + y) mod b = (x' mod b' + y' mod b') mod b'"
     by (simp add: mod_add_eq)
   also have "\<dots> = (x' + y') mod b'"
     by (simp add: mod_add_eq)
   finally show ?thesis
     by (simp add: 4)
 qed
 
 lemma mod_minus_cong:
   fixes b b' :: int
   assumes "b = b'"
     and "x mod b' = x' mod b'"
     and "y mod b' = y' mod b'"
     and "x' - y' = z'"
   shows "(x - y) mod b = z' mod b'"
   using assms [symmetric] by (auto intro: mod_diff_cong)
 
 lemma word_induct_less [case_names zero less]:
   \<open>P m\<close> if zero: \<open>P 0\<close> and less: \<open>\<And>n. n < m \<Longrightarrow> P n \<Longrightarrow> P (1 + n)\<close>
   for m :: \<open>'a::len word\<close>
 proof -
   define q where \<open>q = unat m\<close>
   with less have \<open>\<And>n. n < word_of_nat q \<Longrightarrow> P n \<Longrightarrow> P (1 + n)\<close>
     by simp
   then have \<open>P (word_of_nat q :: 'a word)\<close>
   proof (induction q)
     case 0
     show ?case
       by (simp add: zero)
   next
     case (Suc q)
     show ?case
     proof (cases \<open>1 + word_of_nat q = (0 :: 'a word)\<close>)
       case True
       then show ?thesis
         by (simp add: zero)
     next
       case False
       then have *: \<open>word_of_nat q < (word_of_nat (Suc q) :: 'a word)\<close>
         by (simp add: unatSuc word_less_nat_alt)
       then have **: \<open>n < (1 + word_of_nat q :: 'a word) \<longleftrightarrow> n \<le> (word_of_nat q :: 'a word)\<close> for n
         by (metis (no_types, lifting) add.commute inc_le le_less_trans not_less of_nat_Suc)
       have \<open>P (word_of_nat q)\<close>
         by (simp add: "**" Suc.IH Suc.prems)
       with * have \<open>P (1 + word_of_nat q)\<close>
         by (rule Suc.prems)
       then show ?thesis
         by simp
     qed
   qed
   with \<open>q = unat m\<close> show ?thesis
     by simp
 qed
 
 lemma word_induct: "P 0 \<Longrightarrow> (\<And>n. P n \<Longrightarrow> P (1 + n)) \<Longrightarrow> P m"
   for P :: "'a::len word \<Rightarrow> bool"
   by (rule word_induct_less)
 
 lemma word_induct2 [case_names zero suc, induct type]: "P 0 \<Longrightarrow> (\<And>n. 1 + n \<noteq> 0 \<Longrightarrow> P n \<Longrightarrow> P (1 + n)) \<Longrightarrow> P n"
   for P :: "'b::len word \<Rightarrow> bool"
 by (induction rule: word_induct_less; force)
 
 
 subsection \<open>Recursion combinator for words\<close>
 
 definition word_rec :: "'a \<Rightarrow> ('b::len word \<Rightarrow> 'a \<Rightarrow> 'a) \<Rightarrow> 'b word \<Rightarrow> 'a"
   where "word_rec forZero forSuc n = rec_nat forZero (forSuc \<circ> of_nat) (unat n)"
 
 lemma word_rec_0 [simp]: "word_rec z s 0 = z"
   by (simp add: word_rec_def)
 
 lemma word_rec_Suc [simp]: "1 + n \<noteq> 0 \<Longrightarrow> word_rec z s (1 + n) = s n (word_rec z s n)"
   for n :: "'a::len word"
   by (simp add: unatSuc word_rec_def)
 
 lemma word_rec_Pred: "n \<noteq> 0 \<Longrightarrow> word_rec z s n = s (n - 1) (word_rec z s (n - 1))"
   by (metis add.commute diff_add_cancel word_rec_Suc)
 
 lemma word_rec_in: "f (word_rec z (\<lambda>_. f) n) = word_rec (f z) (\<lambda>_. f) n"
   by (induct n) simp_all
 
 lemma word_rec_in2: "f n (word_rec z f n) = word_rec (f 0 z) (f \<circ> (+) 1) n"
   by (induct n) simp_all
 
 lemma word_rec_twice:
   "m \<le> n \<Longrightarrow> word_rec z f n = word_rec (word_rec z f (n - m)) (f \<circ> (+) (n - m)) m"
 proof (induction n arbitrary: z f)
   case zero
   then show ?case
     by (metis diff_0_right word_le_0_iff word_rec_0)
 next
   case (suc n z f)
   show ?case
   proof (cases "1 + (n - m) = 0")
     case True
     then show ?thesis
       by (simp add: add_diff_eq)
   next
     case False
     then have eq: "1 + n - m = 1 + (n - m)"
       by simp
     with False have "m \<le> n"
       by (metis "suc.prems" add.commute dual_order.antisym eq_iff_diff_eq_0 inc_le leI)
     with False "suc.hyps" show ?thesis
       using suc.IH [of "f 0 z" "f \<circ> (+) 1"] 
       by (simp add: word_rec_in2 eq add.assoc o_def)
   qed
 qed
 
 lemma word_rec_id: "word_rec z (\<lambda>_. id) n = z"
   by (induct n) auto
 
 lemma word_rec_id_eq: "(\<And>m. m < n \<Longrightarrow> f m = id) \<Longrightarrow> word_rec z f n = z"
   by (induction n) (auto simp add: unatSuc unat_arith_simps(2))
 
 lemma word_rec_max:
   assumes "\<forall>m\<ge>n. m \<noteq> - 1 \<longrightarrow> f m = id"
   shows "word_rec z f (- 1) = word_rec z f n"
 proof -
   have \<section>: "\<And>m. \<lbrakk>m < - 1 - n\<rbrakk> \<Longrightarrow> (f \<circ> (+) n) m = id"
     using assms
     by (metis (mono_tags, lifting) add.commute add_diff_cancel_left' comp_apply less_le olen_add_eqv plus_minus_no_overflow word_n1_ge)
   have "word_rec z f (- 1) = word_rec (word_rec z f (- 1 - (- 1 - n))) (f \<circ> (+) (- 1 - (- 1 - n))) (- 1 - n)"
     by (meson word_n1_ge word_rec_twice)
   also have "... = word_rec z f n"
     by (metis (no_types, lifting) \<section> diff_add_cancel minus_diff_eq uminus_add_conv_diff word_rec_id_eq)
   finally show ?thesis .
 qed
 
 
 subsection \<open>More\<close>
 
 lemma mask_1: "mask 1 = 1"
   by simp
 
 lemma mask_Suc_0: "mask (Suc 0) = 1"
   by simp
 
 lemma bin_last_bintrunc: "odd (take_bit l n) \<longleftrightarrow> l > 0 \<and> odd n"
   by simp
 
 
 lemma push_bit_word_beyond [simp]:
   \<open>push_bit n w = 0\<close> if \<open>LENGTH('a) \<le> n\<close> for w :: \<open>'a::len word\<close>
   using that by (transfer fixing: n) (simp add: take_bit_push_bit)
 
 lemma drop_bit_word_beyond [simp]:
   \<open>drop_bit n w = 0\<close> if \<open>LENGTH('a) \<le> n\<close> for w :: \<open>'a::len word\<close>
   using that by (transfer fixing: n) (simp add: drop_bit_take_bit)
 
 lemma signed_drop_bit_beyond:
   \<open>signed_drop_bit n w = (if bit w (LENGTH('a) - Suc 0) then - 1 else 0)\<close>
   if \<open>LENGTH('a) \<le> n\<close> for w :: \<open>'a::len word\<close>
   by (rule bit_word_eqI) (simp add: bit_signed_drop_bit_iff that)
 
 end
 
 
 subsection \<open>SMT support\<close>
 
 ML_file \<open>Tools/smt_word.ML\<close>
 
 end
diff --git a/src/HOL/String.thy b/src/HOL/String.thy
--- a/src/HOL/String.thy
+++ b/src/HOL/String.thy
@@ -1,753 +1,753 @@
 (* Author: Tobias Nipkow, Florian Haftmann, TU Muenchen *)
 
 section \<open>Character and string types\<close>
 
 theory String
 imports Enum Bit_Operations Code_Numeral
 begin
 
 subsection \<open>Strings as list of bytes\<close>
 
 text \<open>
   When modelling strings, we follow the approach given
   in \<^url>\<open>https://utf8everywhere.org/\<close>:
 
   \<^item> Strings are a list of bytes (8 bit).
 
   \<^item> Byte values from 0 to 127 are US-ASCII.
 
   \<^item> Byte values from 128 to 255 are uninterpreted blobs.
 \<close>
 
 subsubsection \<open>Bytes as datatype\<close>
 
 datatype char =
   Char (digit0: bool) (digit1: bool) (digit2: bool) (digit3: bool)
        (digit4: bool) (digit5: bool) (digit6: bool) (digit7: bool)
 
 context comm_semiring_1
 begin
 
 definition of_char :: \<open>char \<Rightarrow> 'a\<close>
   where \<open>of_char c = horner_sum of_bool 2 [digit0 c, digit1 c, digit2 c, digit3 c, digit4 c, digit5 c, digit6 c, digit7 c]\<close>
 
 lemma of_char_Char [simp]:
   \<open>of_char (Char b0 b1 b2 b3 b4 b5 b6 b7) =
     horner_sum of_bool 2 [b0, b1, b2, b3, b4, b5, b6, b7]\<close>
   by (simp add: of_char_def)
 
 end
 
 context unique_euclidean_semiring_with_bit_operations
 begin
 
 definition char_of :: \<open>'a \<Rightarrow> char\<close>
   where \<open>char_of n = Char (odd n) (bit n 1) (bit n 2) (bit n 3) (bit n 4) (bit n 5) (bit n 6) (bit n 7)\<close>
 
 lemma char_of_take_bit_eq:
   \<open>char_of (take_bit n m) = char_of m\<close> if \<open>n \<ge> 8\<close>
   using that by (simp add: char_of_def bit_take_bit_iff)
 
 lemma char_of_char [simp]:
   \<open>char_of (of_char c) = c\<close>
   by (simp only: of_char_def char_of_def bit_horner_sum_bit_iff) simp
 
 lemma char_of_comp_of_char [simp]:
   "char_of \<circ> of_char = id"
   by (simp add: fun_eq_iff)
 
 lemma inj_of_char:
   \<open>inj of_char\<close>
 proof (rule injI)
   fix c d
   assume "of_char c = of_char d"
   then have "char_of (of_char c) = char_of (of_char d)"
     by simp
   then show "c = d"
     by simp
 qed
 
 lemma of_char_eqI:
   \<open>c = d\<close> if \<open>of_char c = of_char d\<close>
   using that inj_of_char by (simp add: inj_eq)
 
 lemma of_char_eq_iff [simp]:
   \<open>of_char c = of_char d \<longleftrightarrow> c = d\<close>
   by (auto intro: of_char_eqI)
 
 lemma of_char_of [simp]:
   \<open>of_char (char_of a) = a mod 256\<close>
 proof -
   have \<open>[0..<8] = [0, Suc 0, 2, 3, 4, 5, 6, 7 :: nat]\<close>
     by (simp add: upt_eq_Cons_conv)
   then have \<open>[odd a, bit a 1, bit a 2, bit a 3, bit a 4, bit a 5, bit a 6, bit a 7] = map (bit a) [0..<8]\<close>
     by simp
   then have \<open>of_char (char_of a) = take_bit 8 a\<close>
     by (simp only: char_of_def of_char_def char.sel horner_sum_bit_eq_take_bit)
   then show ?thesis
     by (simp add: take_bit_eq_mod)
 qed
 
 lemma char_of_mod_256 [simp]:
   \<open>char_of (n mod 256) = char_of n\<close>
   by (rule of_char_eqI) simp
 
 lemma of_char_mod_256 [simp]:
   \<open>of_char c mod 256 = of_char c\<close>
 proof -
   have \<open>of_char (char_of (of_char c)) mod 256 = of_char (char_of (of_char c))\<close>
     by (simp only: of_char_of) simp
   then show ?thesis
     by simp
 qed
 
 lemma char_of_quasi_inj [simp]:
   \<open>char_of m = char_of n \<longleftrightarrow> m mod 256 = n mod 256\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof
   assume ?Q
   then show ?P
     by (auto intro: of_char_eqI)
 next
   assume ?P
   then have \<open>of_char (char_of m) = of_char (char_of n)\<close>
     by simp
   then show ?Q
     by simp
 qed
 
 lemma char_of_eq_iff:
   \<open>char_of n = c \<longleftrightarrow> take_bit 8 n = of_char c\<close>
   by (auto intro: of_char_eqI simp add: take_bit_eq_mod)
 
 lemma char_of_nat [simp]:
   \<open>char_of (of_nat n) = char_of n\<close>
-  by (simp add: char_of_def String.char_of_def drop_bit_of_nat bit_simps)
+  by (simp add: char_of_def String.char_of_def drop_bit_of_nat bit_simps possible_bit_def)
 
 end
 
 lemma inj_on_char_of_nat [simp]:
   "inj_on char_of {0::nat..<256}"
   by (rule inj_onI) simp
 
 lemma nat_of_char_less_256 [simp]:
   "of_char c < (256 :: nat)"
 proof -
   have "of_char c mod (256 :: nat) < 256"
     by arith
   then show ?thesis by simp
 qed
 
 lemma range_nat_of_char:
   "range of_char = {0::nat..<256}"
 proof (rule; rule)
   fix n :: nat
   assume "n \<in> range of_char"
   then show "n \<in> {0..<256}"
     by auto
 next
   fix n :: nat
   assume "n \<in> {0..<256}"
   then have "n = of_char (char_of n)"
     by simp
   then show "n \<in> range of_char"
     by (rule range_eqI)
 qed
 
 lemma UNIV_char_of_nat:
   "UNIV = char_of ` {0::nat..<256}"
 proof -
   have "range (of_char :: char \<Rightarrow> nat) = of_char ` char_of ` {0::nat..<256}"
     by (auto simp add: range_nat_of_char intro!: image_eqI)
   with inj_of_char [where ?'a = nat] show ?thesis
     by (simp add: inj_image_eq_iff)
 qed
 
 lemma card_UNIV_char:
   "card (UNIV :: char set) = 256"
   by (auto simp add: UNIV_char_of_nat card_image)
 
 context
   includes lifting_syntax integer.lifting natural.lifting
 begin
 
 lemma [transfer_rule]:
   \<open>(pcr_integer ===> (=)) char_of char_of\<close>
   by (unfold char_of_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_integer) of_char of_char\<close>
   by (unfold of_char_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>(pcr_natural ===> (=)) char_of char_of\<close>
   by (unfold char_of_def) transfer_prover
 
 lemma [transfer_rule]:
   \<open>((=) ===> pcr_natural) of_char of_char\<close>
   by (unfold of_char_def) transfer_prover
 
 end
 
 lifting_update integer.lifting
 lifting_forget integer.lifting
 
 lifting_update natural.lifting
 lifting_forget natural.lifting
 
 syntax
   "_Char" :: "str_position \<Rightarrow> char"    ("CHR _")
   "_Char_ord" :: "num_const \<Rightarrow> char"   ("CHR _")
 
 type_synonym string = "char list"
 
 syntax
   "_String" :: "str_position \<Rightarrow> string"    ("_")
 
 ML_file \<open>Tools/string_syntax.ML\<close>
 
 instantiation char :: enum
 begin
 
 definition
   "Enum.enum = [
     CHR 0x00, CHR 0x01, CHR 0x02, CHR 0x03,
     CHR 0x04, CHR 0x05, CHR 0x06, CHR 0x07,
     CHR 0x08, CHR 0x09, CHR ''\<newline>'', CHR 0x0B,
     CHR 0x0C, CHR 0x0D, CHR 0x0E, CHR 0x0F,
     CHR 0x10, CHR 0x11, CHR 0x12, CHR 0x13,
     CHR 0x14, CHR 0x15, CHR 0x16, CHR 0x17,
     CHR 0x18, CHR 0x19, CHR 0x1A, CHR 0x1B,
     CHR 0x1C, CHR 0x1D, CHR 0x1E, CHR 0x1F,
     CHR '' '', CHR ''!'', CHR 0x22, CHR ''#'',
     CHR ''$'', CHR ''%'', CHR ''&'', CHR 0x27,
     CHR ''('', CHR '')'', CHR ''*'', CHR ''+'',
     CHR '','', CHR ''-'', CHR ''.'', CHR ''/'',
     CHR ''0'', CHR ''1'', CHR ''2'', CHR ''3'',
     CHR ''4'', CHR ''5'', CHR ''6'', CHR ''7'',
     CHR ''8'', CHR ''9'', CHR '':'', CHR '';'',
     CHR ''<'', CHR ''='', CHR ''>'', CHR ''?'',
     CHR ''@'', CHR ''A'', CHR ''B'', CHR ''C'',
     CHR ''D'', CHR ''E'', CHR ''F'', CHR ''G'',
     CHR ''H'', CHR ''I'', CHR ''J'', CHR ''K'',
     CHR ''L'', CHR ''M'', CHR ''N'', CHR ''O'',
     CHR ''P'', CHR ''Q'', CHR ''R'', CHR ''S'',
     CHR ''T'', CHR ''U'', CHR ''V'', CHR ''W'',
     CHR ''X'', CHR ''Y'', CHR ''Z'', CHR ''['',
     CHR 0x5C, CHR '']'', CHR ''^'', CHR ''_'',
     CHR 0x60, CHR ''a'', CHR ''b'', CHR ''c'',
     CHR ''d'', CHR ''e'', CHR ''f'', CHR ''g'',
     CHR ''h'', CHR ''i'', CHR ''j'', CHR ''k'',
     CHR ''l'', CHR ''m'', CHR ''n'', CHR ''o'',
     CHR ''p'', CHR ''q'', CHR ''r'', CHR ''s'',
     CHR ''t'', CHR ''u'', CHR ''v'', CHR ''w'',
     CHR ''x'', CHR ''y'', CHR ''z'', CHR ''{'',
     CHR ''|'', CHR ''}'', CHR ''~'', CHR 0x7F,
     CHR 0x80, CHR 0x81, CHR 0x82, CHR 0x83,
     CHR 0x84, CHR 0x85, CHR 0x86, CHR 0x87,
     CHR 0x88, CHR 0x89, CHR 0x8A, CHR 0x8B,
     CHR 0x8C, CHR 0x8D, CHR 0x8E, CHR 0x8F,
     CHR 0x90, CHR 0x91, CHR 0x92, CHR 0x93,
     CHR 0x94, CHR 0x95, CHR 0x96, CHR 0x97,
     CHR 0x98, CHR 0x99, CHR 0x9A, CHR 0x9B,
     CHR 0x9C, CHR 0x9D, CHR 0x9E, CHR 0x9F,
     CHR 0xA0, CHR 0xA1, CHR 0xA2, CHR 0xA3,
     CHR 0xA4, CHR 0xA5, CHR 0xA6, CHR 0xA7,
     CHR 0xA8, CHR 0xA9, CHR 0xAA, CHR 0xAB,
     CHR 0xAC, CHR 0xAD, CHR 0xAE, CHR 0xAF,
     CHR 0xB0, CHR 0xB1, CHR 0xB2, CHR 0xB3,
     CHR 0xB4, CHR 0xB5, CHR 0xB6, CHR 0xB7,
     CHR 0xB8, CHR 0xB9, CHR 0xBA, CHR 0xBB,
     CHR 0xBC, CHR 0xBD, CHR 0xBE, CHR 0xBF,
     CHR 0xC0, CHR 0xC1, CHR 0xC2, CHR 0xC3,
     CHR 0xC4, CHR 0xC5, CHR 0xC6, CHR 0xC7,
     CHR 0xC8, CHR 0xC9, CHR 0xCA, CHR 0xCB,
     CHR 0xCC, CHR 0xCD, CHR 0xCE, CHR 0xCF,
     CHR 0xD0, CHR 0xD1, CHR 0xD2, CHR 0xD3,
     CHR 0xD4, CHR 0xD5, CHR 0xD6, CHR 0xD7,
     CHR 0xD8, CHR 0xD9, CHR 0xDA, CHR 0xDB,
     CHR 0xDC, CHR 0xDD, CHR 0xDE, CHR 0xDF,
     CHR 0xE0, CHR 0xE1, CHR 0xE2, CHR 0xE3,
     CHR 0xE4, CHR 0xE5, CHR 0xE6, CHR 0xE7,
     CHR 0xE8, CHR 0xE9, CHR 0xEA, CHR 0xEB,
     CHR 0xEC, CHR 0xED, CHR 0xEE, CHR 0xEF,
     CHR 0xF0, CHR 0xF1, CHR 0xF2, CHR 0xF3,
     CHR 0xF4, CHR 0xF5, CHR 0xF6, CHR 0xF7,
     CHR 0xF8, CHR 0xF9, CHR 0xFA, CHR 0xFB,
     CHR 0xFC, CHR 0xFD, CHR 0xFE, CHR 0xFF]"
 
 definition
   "Enum.enum_all P \<longleftrightarrow> list_all P (Enum.enum :: char list)"
 
 definition
   "Enum.enum_ex P \<longleftrightarrow> list_ex P (Enum.enum :: char list)"
 
 lemma enum_char_unfold:
   "Enum.enum = map char_of [0..<256]"
 proof -
   have "map (of_char :: char \<Rightarrow> nat) Enum.enum = [0..<256]"
     by (simp add: enum_char_def of_char_def upt_conv_Cons_Cons numeral_2_eq_2 [symmetric])
   then have "map char_of (map (of_char :: char \<Rightarrow> nat) Enum.enum) =
     map char_of [0..<256]"
     by simp
   then show ?thesis
     by simp
 qed
 
 instance proof
   show UNIV: "UNIV = set (Enum.enum :: char list)"
     by (simp add: enum_char_unfold UNIV_char_of_nat atLeast0LessThan)
   show "distinct (Enum.enum :: char list)"
     by (auto simp add: enum_char_unfold distinct_map intro: inj_onI)
   show "\<And>P. Enum.enum_all P \<longleftrightarrow> Ball (UNIV :: char set) P"
     by (simp add: UNIV enum_all_char_def list_all_iff)
   show "\<And>P. Enum.enum_ex P \<longleftrightarrow> Bex (UNIV :: char set) P"
     by (simp add: UNIV enum_ex_char_def list_ex_iff)
 qed
 
 end
 
 lemma linorder_char:
   "class.linorder (\<lambda>c d. of_char c \<le> (of_char d :: nat)) (\<lambda>c d. of_char c < (of_char d :: nat))"
   by standard auto
 
 text \<open>Optimized version for execution\<close>
 
 definition char_of_integer :: "integer \<Rightarrow> char"
   where [code_abbrev]: "char_of_integer = char_of"
 
 definition integer_of_char :: "char \<Rightarrow> integer"
   where [code_abbrev]: "integer_of_char = of_char"
 
 lemma char_of_integer_code [code]:
   "char_of_integer k = (let
      (q0, b0) = bit_cut_integer k;
      (q1, b1) = bit_cut_integer q0;
      (q2, b2) = bit_cut_integer q1;
      (q3, b3) = bit_cut_integer q2;
      (q4, b4) = bit_cut_integer q3;
      (q5, b5) = bit_cut_integer q4;
      (q6, b6) = bit_cut_integer q5;
      (_, b7) = bit_cut_integer q6
     in Char b0 b1 b2 b3 b4 b5 b6 b7)"
   by (simp add: bit_cut_integer_def char_of_integer_def char_of_def div_mult2_numeral_eq bit_iff_odd_drop_bit drop_bit_eq_div)
 
 lemma integer_of_char_code [code]:
   "integer_of_char (Char b0 b1 b2 b3 b4 b5 b6 b7) =
     ((((((of_bool b7 * 2 + of_bool b6) * 2 +
       of_bool b5) * 2 + of_bool b4) * 2 +
         of_bool b3) * 2 + of_bool b2) * 2 +
           of_bool b1) * 2 + of_bool b0"
   by (simp add: integer_of_char_def of_char_def)
 
 
 subsection \<open>Strings as dedicated type for target language code generation\<close>
 
 subsubsection \<open>Logical specification\<close>
 
 context
 begin
 
 qualified definition ascii_of :: "char \<Rightarrow> char"
   where "ascii_of c = Char (digit0 c) (digit1 c) (digit2 c) (digit3 c) (digit4 c) (digit5 c) (digit6 c) False"
 
 qualified lemma ascii_of_Char [simp]:
   "ascii_of (Char b0 b1 b2 b3 b4 b5 b6 b7) = Char b0 b1 b2 b3 b4 b5 b6 False"
   by (simp add: ascii_of_def)
 
 qualified lemma not_digit7_ascii_of [simp]:
   "\<not> digit7 (ascii_of c)"
   by (simp add: ascii_of_def)
 
 qualified lemma ascii_of_idem:
   "ascii_of c = c" if "\<not> digit7 c"
   using that by (cases c) simp
 
 qualified lemma char_of_ascii_of [simp]:
   "of_char (ascii_of c) = take_bit 7 (of_char c :: nat)"
   by (cases c) (simp only: ascii_of_Char of_char_Char take_bit_horner_sum_bit_eq, simp)
 
 qualified typedef literal = "{cs. \<forall>c\<in>set cs. \<not> digit7 c}"
   morphisms explode Abs_literal
 proof
   show "[] \<in> {cs. \<forall>c\<in>set cs. \<not> digit7 c}"
     by simp
 qed
 
 qualified setup_lifting type_definition_literal
 
 qualified lift_definition implode :: "string \<Rightarrow> literal"
   is "map ascii_of"
   by auto
 
 qualified lemma implode_explode_eq [simp]:
   "String.implode (String.explode s) = s"
 proof transfer
   fix cs
   show "map ascii_of cs = cs" if "\<forall>c\<in>set cs. \<not> digit7 c"
     using that
       by (induction cs) (simp_all add: ascii_of_idem)
 qed
 
 qualified lemma explode_implode_eq [simp]:
   "String.explode (String.implode cs) = map ascii_of cs"
   by transfer rule
 
 end
 
 
 subsubsection \<open>Syntactic representation\<close>
 
 text \<open>
   Logical ground representations for literals are:
 
   \<^enum> \<open>0\<close> for the empty literal;
 
   \<^enum> \<open>Literal b0 \<dots> b6 s\<close> for a literal starting with one
     character and continued by another literal.
 
   Syntactic representations for literals are:
 
   \<^enum> Printable text as string prefixed with \<open>STR\<close>;
 
   \<^enum> A single ascii value as numerical hexadecimal value prefixed with \<open>STR\<close>.
 \<close>
 
 instantiation String.literal :: zero
 begin
 
 context
 begin
 
 qualified lift_definition zero_literal :: String.literal
   is Nil
   by simp
 
 instance ..
 
 end
 
 end
 
 context
 begin
 
 qualified abbreviation (output) empty_literal :: String.literal
   where "empty_literal \<equiv> 0"
 
 qualified lift_definition Literal :: "bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> String.literal \<Rightarrow> String.literal"
   is "\<lambda>b0 b1 b2 b3 b4 b5 b6 cs. Char b0 b1 b2 b3 b4 b5 b6 False # cs"
   by auto
 
 qualified lemma Literal_eq_iff [simp]:
   "Literal b0 b1 b2 b3 b4 b5 b6 s = Literal c0 c1 c2 c3 c4 c5 c6 t
      \<longleftrightarrow> (b0 \<longleftrightarrow> c0) \<and> (b1 \<longleftrightarrow> c1) \<and> (b2 \<longleftrightarrow> c2) \<and> (b3 \<longleftrightarrow> c3)
          \<and> (b4 \<longleftrightarrow> c4) \<and> (b5 \<longleftrightarrow> c5) \<and> (b6 \<longleftrightarrow> c6) \<and> s = t"
   by transfer simp
 
 qualified lemma empty_neq_Literal [simp]:
   "empty_literal \<noteq> Literal b0 b1 b2 b3 b4 b5 b6 s"
   by transfer simp
 
 qualified lemma Literal_neq_empty [simp]:
   "Literal b0 b1 b2 b3 b4 b5 b6 s \<noteq> empty_literal"
   by transfer simp
 
 end
 
 code_datatype "0 :: String.literal" String.Literal
 
 syntax
   "_Literal" :: "str_position \<Rightarrow> String.literal"   ("STR _")
   "_Ascii" :: "num_const \<Rightarrow> String.literal"        ("STR _")
 
 ML_file \<open>Tools/literal.ML\<close>
 
 
 subsubsection \<open>Operations\<close>
 
 instantiation String.literal :: plus
 begin
 
 context
 begin
 
 qualified lift_definition plus_literal :: "String.literal \<Rightarrow> String.literal \<Rightarrow> String.literal"
   is "(@)"
   by auto
 
 instance ..
 
 end
 
 end
 
 instance String.literal :: monoid_add
   by (standard; transfer) simp_all
 
 instantiation String.literal :: size
 begin
 
 context
   includes literal.lifting
 begin
 
 lift_definition size_literal :: "String.literal \<Rightarrow> nat"
   is length .
 
 end
 
 instance ..
 
 end
 
 instantiation String.literal :: equal
 begin
 
 context
 begin
 
 qualified lift_definition equal_literal :: "String.literal \<Rightarrow> String.literal \<Rightarrow> bool"
   is HOL.equal .
 
 instance
   by (standard; transfer) (simp add: equal)
 
 end
 
 end
 
 instantiation String.literal :: linorder
 begin
 
 context
 begin
 
 qualified lift_definition less_eq_literal :: "String.literal \<Rightarrow> String.literal \<Rightarrow> bool"
   is "ord.lexordp_eq (\<lambda>c d. of_char c < (of_char d :: nat))"
   .
 
 qualified lift_definition less_literal :: "String.literal \<Rightarrow> String.literal \<Rightarrow> bool"
   is "ord.lexordp (\<lambda>c d. of_char c < (of_char d :: nat))"
   .
 
 instance proof -
   from linorder_char interpret linorder "ord.lexordp_eq (\<lambda>c d. of_char c < (of_char d :: nat))"
     "ord.lexordp (\<lambda>c d. of_char c < (of_char d :: nat)) :: string \<Rightarrow> string \<Rightarrow> bool"
     by (rule linorder.lexordp_linorder)
   show "PROP ?thesis"
     by (standard; transfer) (simp_all add: less_le_not_le linear)
 qed
 
 end
 
 end
 
 lemma infinite_literal:
   "infinite (UNIV :: String.literal set)"
 proof -
   define S where "S = range (\<lambda>n. replicate n CHR ''A'')"
   have "inj_on String.implode S"
   proof (rule inj_onI)
     fix cs ds
     assume "String.implode cs = String.implode ds"
     then have "String.explode (String.implode cs) = String.explode (String.implode ds)"
       by simp
     moreover assume "cs \<in> S" and "ds \<in> S"
     ultimately show "cs = ds"
       by (auto simp add: S_def)
   qed
   moreover have "infinite S"
     by (auto simp add: S_def dest: finite_range_imageI [of _ length])
   ultimately have "infinite (String.implode ` S)"
     by (simp add: finite_image_iff)
   then show ?thesis
     by (auto intro: finite_subset)
 qed
 
 
 subsubsection \<open>Executable conversions\<close>
 
 context
 begin
 
 qualified lift_definition asciis_of_literal :: "String.literal \<Rightarrow> integer list"
   is "map of_char"
   .
 
 qualified lemma asciis_of_zero [simp, code]:
   "asciis_of_literal 0 = []"
   by transfer simp
 
 qualified lemma asciis_of_Literal [simp, code]:
   "asciis_of_literal (String.Literal b0 b1 b2 b3 b4 b5 b6 s) =
     of_char (Char b0 b1 b2 b3 b4 b5 b6 False) # asciis_of_literal s "
   by transfer simp
 
 qualified lift_definition literal_of_asciis :: "integer list \<Rightarrow> String.literal"
   is "map (String.ascii_of \<circ> char_of)"
   by auto
 
 qualified lemma literal_of_asciis_Nil [simp, code]:
   "literal_of_asciis [] = 0"
   by transfer simp
 
 qualified lemma literal_of_asciis_Cons [simp, code]:
   "literal_of_asciis (k # ks) = (case char_of k
     of Char b0 b1 b2 b3 b4 b5 b6 b7 \<Rightarrow> String.Literal b0 b1 b2 b3 b4 b5 b6 (literal_of_asciis ks))"
   by (simp add: char_of_def) (transfer, simp add: char_of_def)
 
 qualified lemma literal_of_asciis_of_literal [simp]:
   "literal_of_asciis (asciis_of_literal s) = s"
 proof transfer
   fix cs
   assume "\<forall>c\<in>set cs. \<not> digit7 c"
   then show "map (String.ascii_of \<circ> char_of) (map of_char cs) = cs"
     by (induction cs) (simp_all add: String.ascii_of_idem)
 qed
 
 qualified lemma explode_code [code]:
   "String.explode s = map char_of (asciis_of_literal s)"
   by transfer simp
 
 qualified lemma implode_code [code]:
   "String.implode cs = literal_of_asciis (map of_char cs)"
   by transfer simp
 
 qualified lemma equal_literal [code]:
   "HOL.equal (String.Literal b0 b1 b2 b3 b4 b5 b6 s)
     (String.Literal a0 a1 a2 a3 a4 a5 a6 r)
     \<longleftrightarrow> (b0 \<longleftrightarrow> a0) \<and> (b1 \<longleftrightarrow> a1) \<and> (b2 \<longleftrightarrow> a2) \<and> (b3 \<longleftrightarrow> a3)
       \<and> (b4 \<longleftrightarrow> a4) \<and> (b5 \<longleftrightarrow> a5) \<and> (b6 \<longleftrightarrow> a6) \<and> (s = r)"
   by (simp add: equal)
 
 end
 
 
 subsubsection \<open>Technical code generation setup\<close>
 
 text \<open>Alternative constructor for generated computations\<close>
 
 context
 begin
 
 qualified definition Literal' :: "bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> String.literal \<Rightarrow> String.literal"
   where [simp]: "Literal' = String.Literal"
 
 lemma [code]:
   \<open>Literal' b0 b1 b2 b3 b4 b5 b6 s = String.literal_of_asciis
     [foldr (\<lambda>b k. of_bool b + k * 2) [b0, b1, b2, b3, b4, b5, b6] 0] + s\<close>
 proof -
   have \<open>foldr (\<lambda>b k. of_bool b + k * 2) [b0, b1, b2, b3, b4, b5, b6] 0 = of_char (Char b0 b1 b2 b3 b4 b5 b6 False)\<close>
     by simp
   moreover have \<open>Literal' b0 b1 b2 b3 b4 b5 b6 s = String.literal_of_asciis
     [of_char (Char b0 b1 b2 b3 b4 b5 b6 False)] + s\<close>
     by (unfold Literal'_def) (transfer, simp only: list.simps comp_apply char_of_char, simp)
   ultimately show ?thesis
     by simp
 qed
 
 lemma [code_computation_unfold]:
   "String.Literal = Literal'"
   by simp
 
 end
 
 code_reserved SML string String Char List
 code_reserved OCaml string String Char List
 code_reserved Haskell Prelude
 code_reserved Scala string
 
 code_printing
   type_constructor String.literal \<rightharpoonup>
     (SML) "string"
     and (OCaml) "string"
     and (Haskell) "String"
     and (Scala) "String"
 | constant "STR ''''" \<rightharpoonup>
     (SML) "\"\""
     and (OCaml) "\"\""
     and (Haskell) "\"\""
     and (Scala) "\"\""
 
 setup \<open>
   fold Literal.add_code ["SML", "OCaml", "Haskell", "Scala"]
 \<close>
 
 code_printing
   constant "(+) :: String.literal \<Rightarrow> String.literal \<Rightarrow> String.literal" \<rightharpoonup>
     (SML) infixl 18 "^"
     and (OCaml) infixr 6 "^"
     and (Haskell) infixr 5 "++"
     and (Scala) infixl 7 "+"
 | constant String.literal_of_asciis \<rightharpoonup>
     (SML) "!(String.implode/ o List.map (fn k => if 0 <= k andalso k < 128 then (Char.chr o IntInf.toInt) k else raise Fail \"Non-ASCII character in literal\"))"
     and (OCaml) "!(let xs = _
       and chr k =
         let l = Z.to'_int k
           in if 0 <= l && l < 128
           then Char.chr l
           else failwith \"Non-ASCII character in literal\"
       in String.init (List.length xs) (List.nth (List.map chr xs)))"
     and (Haskell) "map/ (let chr k | (0 <= k && k < 128) = Prelude.toEnum k :: Prelude.Char in chr . Prelude.fromInteger)"
     and (Scala) "\"\"/ ++/ _.map((k: BigInt) => if (BigInt(0) <= k && k < BigInt(128)) k.charValue else sys.error(\"Non-ASCII character in literal\"))"
 | constant String.asciis_of_literal \<rightharpoonup>
     (SML) "!(List.map (fn c => let val k = Char.ord c in if k < 128 then IntInf.fromInt k else raise Fail \"Non-ASCII character in literal\" end) /o String.explode)"
     and (OCaml) "!(let s = _ in let rec exp i l = if i < 0 then l else exp (i - 1) (let k = Char.code (String.get s i) in
       if k < 128 then Z.of'_int k :: l else failwith \"Non-ASCII character in literal\") in exp (String.length s - 1) [])"
     and (Haskell) "map/ (let ord k | (k < 128) = Prelude.toInteger k in ord . (Prelude.fromEnum :: Prelude.Char -> Prelude.Int))"
     and (Scala) "!(_.toList.map(c => { val k: Int = c.toInt; if (k < 128) BigInt(k) else sys.error(\"Non-ASCII character in literal\") }))"
 | class_instance String.literal :: equal \<rightharpoonup>
     (Haskell) -
 | constant "HOL.equal :: String.literal \<Rightarrow> String.literal \<Rightarrow> bool" \<rightharpoonup>
     (SML) "!((_ : string) = _)"
     and (OCaml) "!((_ : string) = _)"
     and (Haskell) infix 4 "=="
     and (Scala) infixl 5 "=="
 | constant "(\<le>) :: String.literal \<Rightarrow> String.literal \<Rightarrow> bool" \<rightharpoonup>
     (SML) "!((_ : string) <= _)"
     and (OCaml) "!((_ : string) <= _)"
     and (Haskell) infix 4 "<="
     \<comment> \<open>Order operations for \<^typ>\<open>String.literal\<close> work in Haskell only
           if no type class instance needs to be generated, because String = [Char] in Haskell
           and \<^typ>\<open>char list\<close> need not have the same order as \<^typ>\<open>String.literal\<close>.\<close>
     and (Scala) infixl 4 "<="
     and (Eval) infixl 6 "<="
 | constant "(<) :: String.literal \<Rightarrow> String.literal \<Rightarrow> bool" \<rightharpoonup>
     (SML) "!((_ : string) < _)"
     and (OCaml) "!((_ : string) < _)"
     and (Haskell) infix 4 "<"
     and (Scala) infixl 4 "<"
     and (Eval) infixl 6 "<"
 
 
 subsubsection \<open>Code generation utility\<close>
 
 setup \<open>Sign.map_naming (Name_Space.mandatory_path "Code")\<close>
 
 definition abort :: "String.literal \<Rightarrow> (unit \<Rightarrow> 'a) \<Rightarrow> 'a"
   where [simp]: "abort _ f = f ()"
 
 declare [[code drop: Code.abort]]
 
 lemma abort_cong:
   "msg = msg' \<Longrightarrow> Code.abort msg f = Code.abort msg' f"
   by simp
 
 setup \<open>Sign.map_naming Name_Space.parent_path\<close>
 
 setup \<open>Code_Simp.map_ss (Simplifier.add_cong @{thm Code.abort_cong})\<close>
 
 code_printing
   constant Code.abort \<rightharpoonup>
     (SML) "!(raise/ Fail/ _)"
     and (OCaml) "failwith"
     and (Haskell) "!(error/ ::/ forall a./ String -> (() -> a) -> a)"
     and (Scala) "!{/ sys.error((_));/ ((_)).apply(())/ }"
 
 
 subsubsection \<open>Finally\<close>
 
 lifting_update literal.lifting
 lifting_forget literal.lifting
 
 end