# HG changeset patch
# User haftmann
# Date 1571510469 -7200
# Node ID 8c2bef3df48885f0cf3e2ba73579f1337690b84d
# Parent  38298c04c12e4f373fbe2a649306686fad3a7dff
refined proof of concept for bit operations

diff -r 38298c04c12e -r 8c2bef3df488 src/HOL/ex/Bit_Lists.thy
--- a/src/HOL/ex/Bit_Lists.thy	Sat Oct 19 20:41:03 2019 +0200
+++ b/src/HOL/ex/Bit_Lists.thy	Sat Oct 19 20:41:09 2019 +0200
@@ -1,169 +1,938 @@
 (*  Author:  Florian Haftmann, TUM
 *)
 
-section \<open>Proof of concept for algebraically founded lists of bits\<close>
+section \<open>Proof(s) of concept for algebraically founded lists of bits\<close>
 
 theory Bit_Lists
   imports Main
 begin
 
+subsection \<open>Bit representations\<close>
+
+subsubsection \<open>Mere syntactic bit representation\<close>
+
+class bit_representation =
+  fixes bits_of :: "'a \<Rightarrow> bool list"
+    and of_bits :: "bool list \<Rightarrow> 'a"
+  assumes of_bits_of [simp]: "of_bits (bits_of a) = a"
+
+
+subsubsection \<open>Algebraic bit representation\<close>
+
 context comm_semiring_1
 begin
+ 
+primrec radix_value :: "('b \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'b list \<Rightarrow> 'a"
+  where "radix_value f b [] = 0"
+  | "radix_value f b (a # as) = f a + radix_value f b as * b"
+
+abbreviation (input) unsigned_of_bits :: "bool list \<Rightarrow> 'a"
+  where "unsigned_of_bits \<equiv> radix_value of_bool 2"
+
+lemma unsigned_of_bits_replicate_False [simp]:
+  "unsigned_of_bits (replicate n False) = 0"
+  by (induction n) simp_all
+
+end
+
+context unique_euclidean_semiring_with_nat
+begin
 
-primrec of_unsigned :: "bool list \<Rightarrow> 'a"
-  where "of_unsigned [] = 0"
-  | "of_unsigned (b # bs) = of_bool b + 2 * of_unsigned bs"
+lemma unsigned_of_bits_append [simp]:
+  "unsigned_of_bits (bs @ cs) = unsigned_of_bits bs
+    + push_bit (length bs) (unsigned_of_bits cs)"
+  by (induction bs) (simp_all add: push_bit_double,
+    simp_all add: algebra_simps)
+
+lemma unsigned_of_bits_take [simp]:
+  "unsigned_of_bits (take n bs) = take_bit n (unsigned_of_bits bs)"
+proof (induction bs arbitrary: n)
+  case Nil
+  then show ?case
+    by simp
+next
+  case (Cons b bs)
+  then show ?case
+    by (cases n) (simp_all add: ac_simps)
+qed
+
+lemma unsigned_of_bits_drop [simp]:
+  "unsigned_of_bits (drop n bs) = drop_bit n (unsigned_of_bits bs)"
+proof (induction bs arbitrary: n)
+  case Nil
+  then show ?case
+    by simp
+next
+  case (Cons b bs)
+  then show ?case
+    by (cases n) simp_all
+qed
+
+end
+
+
+subsubsection \<open>Instances\<close>
+
+text \<open>Unclear whether a \<^typ>\<open>bool\<close> instantiation is needed or not\<close>
+
+instantiation nat :: bit_representation
+begin
+
+fun bits_of_nat :: "nat \<Rightarrow> bool list"
+  where "bits_of (n::nat) =
+    (if n = 0 then [] else odd n # bits_of (n div 2))"
+
+lemma bits_of_nat_simps [simp]:
+  "bits_of (0::nat) = []"
+  "n > 0 \<Longrightarrow> bits_of n = odd n # bits_of (n div 2)" for n :: nat
+  by simp_all
+
+declare bits_of_nat.simps [simp del]
+
+definition of_bits_nat :: "bool list \<Rightarrow> nat"
+  where [simp]: "of_bits_nat = unsigned_of_bits"
+  \<comment> \<open>remove simp\<close>
+
+instance proof
+  show "of_bits (bits_of n) = n" for n :: nat
+    by (induction n rule: nat_bit_induct) simp_all
+qed
 
 end
 
-context comm_ring_1
+lemma bits_of_Suc_0 [simp]:
+  "bits_of (Suc 0) = [True]"
+  by simp
+
+lemma bits_of_1_nat [simp]:
+  "bits_of (1 :: nat) = [True]"
+  by simp
+
+lemma bits_of_nat_numeral_simps [simp]:
+  "bits_of (numeral Num.One :: nat) = [True]" (is ?One)
+  "bits_of (numeral (Num.Bit0 n) :: nat) = False # bits_of (numeral n :: nat)" (is ?Bit0)
+  "bits_of (numeral (Num.Bit1 n) :: nat) = True # bits_of (numeral n :: nat)" (is ?Bit1)
+proof -
+  show ?One
+    by simp
+  define m :: nat where "m = numeral n"
+  then have "m > 0" and *: "numeral n = m" "numeral (Num.Bit0 n) = 2 * m" "numeral (Num.Bit1 n) = Suc (2 * m)"
+    by simp_all
+  from \<open>m > 0\<close> show ?Bit0 ?Bit1
+    by (simp_all add: *)
+qed
+
+lemma unsigned_of_bits_of_nat [simp]:
+  "unsigned_of_bits (bits_of n) = n" for n :: nat
+  using of_bits_of [of n] by simp
+
+instantiation int :: bit_representation
 begin
 
-definition of_signed :: "bool list \<Rightarrow> 'a"
-  where "of_signed bs = (if bs = [] then 0 else if last bs
-    then - (of_unsigned (map Not bs) + 1) else of_unsigned bs)"
+fun bits_of_int :: "int \<Rightarrow> bool list"
+  where "bits_of_int k = odd k #
+    (if k = 0 \<or> k = - 1 then [] else bits_of_int (k div 2))"
+
+lemma bits_of_int_simps [simp]:
+  "bits_of (0 :: int) = [False]"
+  "bits_of (- 1 :: int) = [True]"
+  "k \<noteq> 0 \<Longrightarrow> k \<noteq> - 1 \<Longrightarrow> bits_of k = odd k # bits_of (k div 2)" for k :: int
+  by simp_all
+
+lemma bits_of_not_Nil [simp]:
+  "bits_of k \<noteq> []" for k :: int
+  by simp
+
+declare bits_of_int.simps [simp del]
+
+definition of_bits_int :: "bool list \<Rightarrow> int"
+  where "of_bits_int bs = (if bs = [] \<or> \<not> last bs then unsigned_of_bits bs
+    else unsigned_of_bits bs - 2 ^ length bs)"
+
+lemma of_bits_int_simps [simp]:
+  "of_bits [] = (0 :: int)"
+  "of_bits [False] = (0 :: int)"
+  "of_bits [True] = (- 1 :: int)"
+  "of_bits (bs @ [b]) = (unsigned_of_bits bs :: int) - (2 ^ length bs) * of_bool b"
+  "of_bits (False # bs) = 2 * (of_bits bs :: int)"
+  "bs \<noteq> [] \<Longrightarrow> of_bits (True # bs) = 1 + 2 * (of_bits bs :: int)"
+  by (simp_all add: of_bits_int_def push_bit_of_1)
+
+instance proof
+  show "of_bits (bits_of k) = k" for k :: int
+    by (induction k rule: int_bit_induct) simp_all
+qed
+
+lemma bits_of_1_int [simp]:
+  "bits_of (1 :: int) = [True, False]"
+  by simp
+
+lemma bits_of_int_numeral_simps [simp]:
+  "bits_of (numeral Num.One :: int) = [True, False]" (is ?One)
+  "bits_of (numeral (Num.Bit0 n) :: int) = False # bits_of (numeral n :: int)" (is ?Bit0)
+  "bits_of (numeral (Num.Bit1 n) :: int) = True # bits_of (numeral n :: int)" (is ?Bit1)
+  "bits_of (- numeral (Num.Bit0 n) :: int) = False # bits_of (- numeral n :: int)" (is ?nBit0)
+  "bits_of (- numeral (Num.Bit1 n) :: int) = True # bits_of (- numeral (Num.inc n) :: int)" (is ?nBit1)
+proof -
+  show ?One
+    by simp
+  define k :: int where "k = numeral n"
+  then have "k > 0" and *: "numeral n = k" "numeral (Num.Bit0 n) = 2 * k" "numeral (Num.Bit1 n) = 2 * k + 1"
+    "numeral (Num.inc n) = k + 1"
+    by (simp_all add: add_One)
+  have "- (2 * k) div 2 = - k" "(- (2 * k) - 1) div 2 = - k - 1"
+    by simp_all
+  with \<open>k > 0\<close> show ?Bit0 ?Bit1 ?nBit0 ?nBit1
+    by (simp_all add: *)
+qed
+
+lemma of_bits_append [simp]:
+  "of_bits (bs @ cs) = of_bits bs + push_bit (length bs) (of_bits cs :: int)"
+    if "bs \<noteq> []" "\<not> last bs"
+using that proof (induction bs rule: list_nonempty_induct)
+  case (single b)
+  then show ?case
+    by simp
+next
+  case (cons b bs)
+  then show ?case
+    by (cases b) (simp_all add: push_bit_double)
+qed
+
+lemma of_bits_replicate_False [simp]:
+  "of_bits (replicate n False) = (0 :: int)"
+  by (auto simp add: of_bits_int_def)
+
+lemma of_bits_drop [simp]:
+  "of_bits (drop n bs) = drop_bit n (of_bits bs :: int)"
+    if "n < length bs"
+using that 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 n)
+    with Cons.prems have "bs \<noteq> []"
+      by auto
+    with Suc Cons.IH [of n] Cons.prems show ?thesis
+      by (cases b) simp_all
+  qed
+qed
 
 end
 
-class semiring_bits = unique_euclidean_semiring_with_nat +
-  assumes half_measure: "a div 2 \<noteq> a \<Longrightarrow> euclidean_size (a div 2) < euclidean_size a"
-  \<comment> \<open>It is not clear whether this could be derived from already existing assumptions.\<close>
+
+subsection \<open>Syntactic bit operations\<close>
+
+class bit_operations = bit_representation +
+  fixes not :: "'a \<Rightarrow> 'a"  ("NOT _" [70] 71)
+    and "and" :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixr "AND" 64)
+    and or :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixr "OR"  59)
+    and xor :: "'a \<Rightarrow> 'a \<Rightarrow> 'a"  (infixr "XOR" 59)
+    and shift_left :: "'a \<Rightarrow> nat \<Rightarrow> 'a"  (infixl "<<" 55)
+    and shift_right :: "'a \<Rightarrow> nat \<Rightarrow> 'a"  (infixl ">>" 55)
+  assumes not_eq: "not = of_bits \<circ> map Not \<circ> bits_of"
+    and and_eq: "length bs = length cs \<Longrightarrow>
+      of_bits bs AND of_bits cs = of_bits (map2 (\<and>) bs cs)"
+    and semilattice_and: "semilattice (AND)"
+    and or_eq: "length bs = length cs \<Longrightarrow>
+      of_bits bs OR of_bits cs = of_bits (map2 (\<or>) bs cs)"
+    and semilattice_or: "semilattice (OR)"
+    and xor_eq: "length bs = length cs \<Longrightarrow>
+      of_bits bs XOR of_bits cs = of_bits (map2 (\<noteq>) bs cs)"
+    and abel_semigroup_xor: "abel_semigroup (XOR)"
+    and shift_right_eq: "a << n = of_bits (replicate n False @ bits_of a)"
+    and shift_left_eq: "n < length (bits_of a) \<Longrightarrow> a >> n = of_bits (drop n (bits_of a))"
 begin
 
-function bits_of :: "'a \<Rightarrow> bool list"
-  where "bits_of a = odd a # (let b = a div 2 in if a = b then [] else bits_of b)"
+text \<open>
+  We want the bitwise operations to bind slightly weaker
+  than \<open>+\<close> and \<open>-\<close>, but \<open>~~\<close> to
+  bind slightly stronger than \<open>*\<close>.
+\<close>
+
+sublocale "and": semilattice "(AND)"
+  by (fact semilattice_and)
+
+sublocale or: semilattice "(OR)"
+  by (fact semilattice_or)
+
+sublocale xor: abel_semigroup "(XOR)"
+  by (fact abel_semigroup_xor)
+
+end
+
+
+subsubsection \<open>Instance \<^typ>\<open>nat\<close>\<close>
+
+locale zip_nat = single: abel_semigroup f
+    for f :: "bool \<Rightarrow> bool \<Rightarrow> bool"  (infixl "\<^bold>*" 70) +
+  assumes end_of_bits: "\<not> False \<^bold>* False"
+begin
+
+lemma False_P_imp:
+  "False \<^bold>* True \<and> P" if "False \<^bold>* P"
+  using that end_of_bits by (cases P) simp_all
+
+function F :: "nat \<Rightarrow> nat \<Rightarrow> nat"  (infixl "\<^bold>\<times>" 70)
+  where "m \<^bold>\<times> n = (if m = 0 \<and> n = 0 then 0
+    else of_bool (odd m \<^bold>* odd n) + (m div 2) \<^bold>\<times> (n div 2) * 2)"
   by auto
 
 termination
-  by (relation "measure euclidean_size") (auto intro: half_measure)
+  by (relation "measure (case_prod (+))") auto
 
-lemma bits_of_not_empty [simp]:
-  "bits_of a \<noteq> []"
-  by (induction a rule: bits_of.induct) simp_all
+lemma zero_left_eq:
+  "0 \<^bold>\<times> n = of_bool (False \<^bold>* True) * n"
+  by (induction n rule: nat_bit_induct) (simp_all add: end_of_bits)
+
+lemma zero_right_eq:
+  "m \<^bold>\<times> 0 = of_bool (True \<^bold>* False) * m"
+  by (induction m rule: nat_bit_induct) (simp_all add: end_of_bits)
 
-lemma bits_of_0 [simp]:
-  "bits_of 0 = [False]"
-  by simp
+lemma simps [simp]:
+  "0 \<^bold>\<times> 0 = 0"
+  "0 \<^bold>\<times> n = of_bool (False \<^bold>* True) * n"
+  "m \<^bold>\<times> 0 = of_bool (True \<^bold>* False) * m"
+  "m > 0 \<Longrightarrow> n > 0 \<Longrightarrow> m \<^bold>\<times> n = of_bool (odd m \<^bold>* odd n) + (m div 2) \<^bold>\<times> (n div 2) * 2"
+  by (simp_all only: zero_left_eq zero_right_eq) simp
 
-lemma bits_of_1 [simp]:
-  "bits_of 1 = [True, False]"
-  by simp
+lemma rec:
+  "m \<^bold>\<times> n = of_bool (odd m \<^bold>* odd n) + (m div 2) \<^bold>\<times> (n div 2) * 2"
+  by (cases "m = 0 \<and> n = 0") (auto simp add: end_of_bits)
+
+declare F.simps [simp del]
 
-lemma bits_of_double [simp]:
-  "bits_of (a * 2) = False # (if a = 0 then [] else bits_of a)"
-  by simp (simp add: mult_2_right)
-
-lemma bits_of_add_1_double [simp]:
-  "bits_of (1 + a * 2) = True # (if a + 1 = 0 then [] else bits_of a)"
-  by simp (simp add: mult_2_right algebra_simps)
-
-declare bits_of.simps [simp del]
+sublocale abel_semigroup F
+proof
+  show "m \<^bold>\<times> n \<^bold>\<times> q = m \<^bold>\<times> (n \<^bold>\<times> q)" for m n q :: nat
+  proof (induction m arbitrary: n q rule: nat_bit_induct)
+    case zero
+    show ?case
+      by simp
+  next
+    case (even m)
+    with rec [of "2 * m"] rec [of _ q] show ?case
+      by (cases "even n") (auto dest: False_P_imp)
+  next
+    case (odd m)
+    with rec [of "Suc (2 * m)"] rec [of _ q] show ?case
+      by (cases "even n"; cases "even q")
+        (auto dest: False_P_imp simp add: ac_simps)
+  qed
+  show "m \<^bold>\<times> n = n \<^bold>\<times> m" for m n :: nat
+  proof (induction m arbitrary: n rule: nat_bit_induct)
+    case zero
+    show ?case
+      by (simp add: ac_simps)
+  next
+    case (even m)
+    with rec [of "2 * m" n] rec [of n "2 * m"] show ?case
+      by (simp add: ac_simps)
+  next
+    case (odd m)
+    with rec [of "Suc (2 * m)" n] rec [of n "Suc (2 * m)"] show ?case
+      by (simp add: ac_simps)
+  qed
+qed
 
-lemma not_last_bits_of_nat [simp]:
-  "\<not> last (bits_of (of_nat n))"
-  by (induction n rule: nat_bit_induct)
-    (use of_nat_neq_0 in \<open>simp_all add: algebra_simps\<close>)
+lemma self [simp]:
+  "n \<^bold>\<times> n = of_bool (True \<^bold>* True) * n"
+  by (induction n rule: nat_bit_induct) (simp_all add: end_of_bits)
 
-lemma of_unsigned_bits_of_nat:
-  "of_unsigned (bits_of (of_nat n)) = of_nat n"
-  by (induction n rule: nat_bit_induct)
-    (use of_nat_neq_0 in \<open>simp_all add: algebra_simps\<close>)
+lemma even_iff [simp]:
+  "even (m \<^bold>\<times> n) \<longleftrightarrow> \<not> (odd m \<^bold>* odd n)"
+proof (induction m arbitrary: n rule: nat_bit_induct)
+  case zero
+  show ?case
+    by (cases "even n") (simp_all add: end_of_bits)
+next
+  case (even m)
+  then show ?case
+    by (simp add: rec [of "2 * m"])
+next
+  case (odd m)
+  then show ?case
+    by (simp add: rec [of "Suc (2 * m)"])
+qed
+
+lemma of_bits:
+  "of_bits bs \<^bold>\<times> of_bits cs = (of_bits (map2 (\<^bold>*) bs cs) :: nat)"
+    if "length bs = length cs" for bs cs
+using that proof (induction bs cs rule: list_induct2)
+  case Nil
+  then show ?case
+    by simp
+next
+  case (Cons b bs c cs)
+  then show ?case
+    by (cases "of_bits bs = (0::nat) \<or> of_bits cs = (0::nat)")
+      (auto simp add: ac_simps end_of_bits rec [of "Suc 0"])
+qed
 
 end
 
-instance nat :: semiring_bits
-  by standard simp
-
-lemma bits_of_Suc_double [simp]:
-  "bits_of (Suc (n * 2)) = True # bits_of n"
-  using bits_of_add_1_double [of n] by simp
-
-lemma of_unsigned_bits_of:
-  "of_unsigned (bits_of n) = n" for n :: nat
-  using of_unsigned_bits_of_nat [of n, where ?'a = nat] by simp
-
-class ring_bits = unique_euclidean_ring_with_nat + semiring_bits
+instantiation nat :: bit_operations
 begin
 
-lemma bits_of_minus_1 [simp]:
-  "bits_of (- 1) = [True]"
-  using bits_of.simps [of "- 1"] by simp
+definition not_nat :: "nat \<Rightarrow> nat"
+  where "not_nat = of_bits \<circ> map Not \<circ> bits_of"
+
+global_interpretation and_nat: zip_nat "(\<and>)"
+  defines and_nat = and_nat.F
+  by standard auto
 
-lemma bits_of_double [simp]:
-  "bits_of (- (a * 2)) = False # (if a = 0 then [] else bits_of (- a))"
-  using bits_of.simps [of "- (a * 2)"] nonzero_mult_div_cancel_right [of 2 "- a"]
-  by simp (simp add: mult_2_right)
+global_interpretation and_nat: semilattice "(AND) :: nat \<Rightarrow> nat \<Rightarrow> nat"
+proof (rule semilattice.intro, fact and_nat.abel_semigroup_axioms, standard)
+  show "n AND n = n" for n :: nat
+    by (simp add: and_nat.self)
+qed
+
+declare and_nat.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
 
-lemma bits_of_minus_1_diff_double [simp]:
-  "bits_of (- 1 - a * 2) = True # (if a = 0 then [] else bits_of (- 1 - a))"
-proof -
-  have [simp]: "- 1 - a = - a - 1"
-    by (simp add: algebra_simps)
-  show ?thesis
-    using bits_of.simps [of "- 1 - a * 2"] div_mult_self1 [of 2 "- 1" "- a"]
-    by simp (simp add: mult_2_right algebra_simps)
+lemma zero_nat_and_eq [simp]:
+  "0 AND n = 0" for n :: nat
+  by simp
+
+lemma and_zero_nat_eq [simp]:
+  "n AND 0 = 0" for n :: nat
+  by simp
+
+global_interpretation or_nat: zip_nat "(\<or>)"
+  defines or_nat = or_nat.F
+  by standard auto
+
+global_interpretation or_nat: semilattice "(OR) :: nat \<Rightarrow> nat \<Rightarrow> nat"
+proof (rule semilattice.intro, fact or_nat.abel_semigroup_axioms, standard)
+  show "n OR n = n" for n :: nat
+    by (simp add: or_nat.self)
 qed
 
-lemma last_bits_of_neg_of_nat [simp]:
-  "last (bits_of (- 1 - of_nat n))"
-proof (induction n rule: nat_bit_induct)
-  case zero
-  then show ?case
+declare or_nat.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
+
+lemma zero_nat_or_eq [simp]:
+  "0 OR n = n" for n :: nat
+  by simp
+
+lemma or_zero_nat_eq [simp]:
+  "n OR 0 = n" for n :: nat
+  by simp
+
+global_interpretation xor_nat: zip_nat "(\<noteq>)"
+  defines xor_nat = xor_nat.F
+  by standard auto
+
+declare xor_nat.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
+
+lemma zero_nat_xor_eq [simp]:
+  "0 XOR n = n" for n :: nat
+  by simp
+
+lemma xor_zero_nat_eq [simp]:
+  "n XOR 0 = n" for n :: nat
+  by simp
+
+definition shift_left_nat :: "nat \<Rightarrow> nat \<Rightarrow> nat"
+  where [simp]: "m << n = push_bit n m" for m :: nat
+
+definition shift_right_nat :: "nat \<Rightarrow> nat \<Rightarrow> nat"
+  where [simp]: "m >> n = drop_bit n m" for m :: nat
+
+instance proof
+  show "semilattice ((AND) :: nat \<Rightarrow> _)"
+    by (fact and_nat.semilattice_axioms)
+  show "semilattice ((OR):: nat \<Rightarrow> _)"
+    by (fact or_nat.semilattice_axioms)
+  show "abel_semigroup ((XOR):: nat \<Rightarrow> _)"
+    by (fact xor_nat.abel_semigroup_axioms)
+  show "(not :: nat \<Rightarrow> _) = of_bits \<circ> map Not \<circ> bits_of"
+    by (fact not_nat_def)
+  show "of_bits bs AND of_bits cs = (of_bits (map2 (\<and>) bs cs) :: nat)"
+    if "length bs = length cs" for bs cs
+    using that by (fact and_nat.of_bits)
+  show "of_bits bs OR of_bits cs = (of_bits (map2 (\<or>) bs cs) :: nat)"
+    if "length bs = length cs" for bs cs
+    using that by (fact or_nat.of_bits)
+  show "of_bits bs XOR of_bits cs = (of_bits (map2 (\<noteq>) bs cs) :: nat)"
+    if "length bs = length cs" for bs cs
+    using that by (fact xor_nat.of_bits)
+  show "m << n = of_bits (replicate n False @ bits_of m)"
+    for m n :: nat
     by simp
-next
-  case (even n)
-  then show ?case
-    by (simp add: algebra_simps)
-next
-  case (odd n)
-  then have "last (bits_of ((- 1 - of_nat n) * 2))"
-    by auto
-  also have "(- 1 - of_nat n) * 2 = - 1 - (1 + 2 * of_nat n)"
-    by (simp add: algebra_simps)
-  finally show ?case
+  show "m >> n = of_bits (drop n (bits_of m))"
+    for m n :: nat
     by simp
 qed
 
-lemma of_signed_bits_of_nat:
-  "of_signed (bits_of (of_nat n)) = of_nat n"
-  by (simp add: of_signed_def of_unsigned_bits_of_nat)
+end
+
+global_interpretation or_nat: semilattice_neutr "(OR)" "0 :: nat"
+  by standard simp
+
+global_interpretation xor_nat: comm_monoid "(XOR)" "0 :: nat"
+  by standard simp
+
+lemma not_nat_simps [simp]:
+  "NOT 0 = (0::nat)"
+  "n > 0 \<Longrightarrow> NOT n = of_bool (even n) + 2 * NOT (n div 2)" for n :: nat
+  by (simp_all add: not_eq)
+
+lemma not_1_nat [simp]:
+  "NOT 1 = (0::nat)"
+  by simp
+
+lemma not_Suc_0 [simp]:
+  "NOT (Suc 0) = (0::nat)"
+  by simp
+
+lemma Suc_0_and_eq [simp]:
+  "Suc 0 AND n = n mod 2"
+  by (cases n) auto
+
+lemma and_Suc_0_eq [simp]:
+  "n AND Suc 0 = n mod 2"
+  using Suc_0_and_eq [of n] by (simp add: ac_simps)
+
+lemma Suc_0_or_eq [simp]:
+  "Suc 0 OR n = n + of_bool (even n)"
+  by (cases n) (simp_all add: ac_simps)
+
+lemma or_Suc_0_eq [simp]:
+  "n OR Suc 0 = n + of_bool (even n)"
+  using Suc_0_or_eq [of n] by (simp add: ac_simps)
+
+lemma Suc_0_xor_eq [simp]:
+  "Suc 0 XOR n = n + of_bool (even n) - of_bool (odd n)"
+  by (cases n) (simp_all add: ac_simps)
+
+lemma xor_Suc_0_eq [simp]:
+  "n XOR Suc 0 = n + of_bool (even n) - of_bool (odd n)"
+  using Suc_0_xor_eq [of n] by (simp add: ac_simps)
+
+
+subsubsection \<open>Instance \<^typ>\<open>int\<close>\<close>
+
+abbreviation (input) complement :: "int \<Rightarrow> int"
+  where "complement k \<equiv> - k - 1"
+
+lemma complement_half:
+  "complement (k * 2) div 2 = complement k"
+  by simp
+
+locale zip_int = single: abel_semigroup f
+  for f :: "bool \<Rightarrow> bool \<Rightarrow> bool"  (infixl "\<^bold>*" 70)
+begin
+ 
+lemma False_False_imp_True_True:
+  "True \<^bold>* True" if "False \<^bold>* False"
+proof (rule ccontr)
+  assume "\<not> True \<^bold>* True"
+  with that show False
+    using single.assoc [of False True True]
+    by (cases "False \<^bold>* True") simp_all
+qed
+
+function F :: "int \<Rightarrow> int \<Rightarrow> int"  (infixl "\<^bold>\<times>" 70)
+  where "k \<^bold>\<times> l = (if k \<in> {0, - 1} \<and> l \<in> {0, - 1}
+    then - of_bool (odd k \<^bold>* odd l)
+    else of_bool (odd k \<^bold>* odd l) + (k div 2) \<^bold>\<times> (l div 2) * 2)"
+  by auto
+
+termination
+  by (relation "measure (\<lambda>(k, l). nat (\<bar>k\<bar> + \<bar>l\<bar>))") auto
+
+lemma zero_left_eq:
+  "0 \<^bold>\<times> l = (case (False \<^bold>* False, False \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> l
+     | (True, False) \<Rightarrow> complement l
+     | (True, True) \<Rightarrow> - 1)"
+  by (induction l rule: int_bit_induct)
+   (simp_all split: bool.split) 
+
+lemma minus_left_eq:
+  "- 1 \<^bold>\<times> l = (case (True \<^bold>* False, True \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> l
+     | (True, False) \<Rightarrow> complement l
+     | (True, True) \<Rightarrow> - 1)"
+  by (induction l rule: int_bit_induct)
+   (simp_all split: bool.split) 
+
+lemma zero_right_eq:
+  "k \<^bold>\<times> 0 = (case (False \<^bold>* False, False \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> k
+     | (True, False) \<Rightarrow> complement k
+     | (True, True) \<Rightarrow> - 1)"
+  by (induction k rule: int_bit_induct)
+    (simp_all add: ac_simps split: bool.split)
 
-lemma of_signed_bits_neg_of_nat:
-  "of_signed (bits_of (- 1 - of_nat n)) = - 1 - of_nat n"
-proof -
-  have "of_unsigned (map Not (bits_of (- 1 - of_nat n))) = of_nat n"
-  proof (induction n rule: nat_bit_induct)
+lemma minus_right_eq:
+  "k \<^bold>\<times> - 1 = (case (True \<^bold>* False, True \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> k
+     | (True, False) \<Rightarrow> complement k
+     | (True, True) \<Rightarrow> - 1)"
+  by (induction k rule: int_bit_induct)
+    (simp_all add: ac_simps split: bool.split)
+
+lemma simps [simp]:
+  "0 \<^bold>\<times> 0 = - of_bool (False \<^bold>* False)"
+  "- 1 \<^bold>\<times> 0 = - of_bool (True \<^bold>* False)"
+  "0 \<^bold>\<times> - 1 = - of_bool (False \<^bold>* True)"
+  "- 1 \<^bold>\<times> - 1 = - of_bool (True \<^bold>* True)"
+  "0 \<^bold>\<times> l = (case (False \<^bold>* False, False \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> l
+     | (True, False) \<Rightarrow> complement l
+     | (True, True) \<Rightarrow> - 1)"
+  "- 1 \<^bold>\<times> l = (case (True \<^bold>* False, True \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> l
+     | (True, False) \<Rightarrow> complement l
+     | (True, True) \<Rightarrow> - 1)"
+  "k \<^bold>\<times> 0 = (case (False \<^bold>* False, False \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> k
+     | (True, False) \<Rightarrow> complement k
+     | (True, True) \<Rightarrow> - 1)"
+  "k \<^bold>\<times> - 1 = (case (True \<^bold>* False, True \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> k
+     | (True, False) \<Rightarrow> complement k
+     | (True, True) \<Rightarrow> - 1)"
+  "k \<noteq> 0 \<Longrightarrow> k \<noteq> - 1 \<Longrightarrow> l \<noteq> 0 \<Longrightarrow> l \<noteq> - 1
+    \<Longrightarrow> k \<^bold>\<times> l = of_bool (odd k \<^bold>* odd l) + (k div 2) \<^bold>\<times> (l div 2) * 2"
+  by simp_all[4] (simp_all only: zero_left_eq minus_left_eq zero_right_eq minus_right_eq, simp)
+
+declare F.simps [simp del]
+
+lemma rec:
+  "k \<^bold>\<times> l = of_bool (odd k \<^bold>* odd l) + (k div 2) \<^bold>\<times> (l div 2) * 2"
+  by (cases "k \<in> {0, - 1} \<and> l \<in> {0, - 1}") (auto simp add: ac_simps F.simps [of k l] split: bool.split)
+
+sublocale abel_semigroup F
+proof
+  show "k \<^bold>\<times> l \<^bold>\<times> r = k \<^bold>\<times> (l \<^bold>\<times> r)" for k l r :: int
+  proof (induction k arbitrary: l r rule: int_bit_induct)
     case zero
+    have "complement l \<^bold>\<times> r = complement (l \<^bold>\<times> r)" if "False \<^bold>* False" "\<not> False \<^bold>* True"
+    proof (induction l arbitrary: r rule: int_bit_induct)
+      case zero
+      from that show ?case
+        by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case minus
+      from that show ?case
+        by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case (even l)
+      with that rec [of _ r] show ?case
+        by (cases "even r")
+          (auto simp add: complement_half ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case (odd l)
+      moreover have "- l - 1 = - 1 - l"
+        by simp
+      ultimately show ?case
+        using that rec [of _ r]
+        by (cases "even r")
+          (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    qed
     then show ?case
+      by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+  next
+    case minus
+    have "complement l \<^bold>\<times> r = complement (l \<^bold>\<times> r)" if "\<not> True \<^bold>* True" "False \<^bold>* True"
+    proof (induction l arbitrary: r rule: int_bit_induct)
+      case zero
+      from that show ?case
+        by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case minus
+      from that show ?case
+        by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case (even l)
+      with that rec [of _ r] show ?case
+        by (cases "even r")
+          (auto simp add: complement_half ac_simps False_False_imp_True_True split: bool.splits)
+    next
+      case (odd l)
+      moreover have "- l - 1 = - 1 - l"
+        by simp
+      ultimately show ?case
+        using that rec [of _ r]
+        by (cases "even r")
+          (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+    qed
+    then show ?case
+      by (auto simp add: ac_simps False_False_imp_True_True split: bool.splits)
+  next
+    case (even k)
+    with rec [of "k * 2"] rec [of _ r] show ?case
+      by (cases "even r"; cases "even l") (auto simp add: ac_simps False_False_imp_True_True)
+  next
+    case (odd k)
+    with rec [of "1 + k * 2"] rec [of _ r] show ?case
+      by (cases "even r"; cases "even l") (auto simp add: ac_simps False_False_imp_True_True)
+  qed
+  show "k \<^bold>\<times> l = l \<^bold>\<times> k" for k l :: int
+  proof (induction k arbitrary: l rule: int_bit_induct)
+    case zero
+    show ?case
       by simp
   next
-    case (even n)
-    then show ?case
-      by (simp add: algebra_simps)
+    case minus
+    show ?case
+      by simp
   next
-    case (odd n)
-    have *: "- 1 - (1 + of_nat n * 2) = - 2 - of_nat n * 2"
-      by (simp add: algebra_simps) (metis add_assoc one_add_one)
-    from odd show ?case
-      using bits_of_double [of "of_nat (Suc n)"] of_nat_neq_0
-      by (simp add: algebra_simps *)
+    case (even k)
+    with rec [of "k * 2" l] rec [of l "k * 2"] show ?case
+      by (simp add: ac_simps)
+  next
+    case (odd k)
+    with rec [of "k * 2 + 1" l] rec [of l "k * 2 + 1"] show ?case
+      by (simp add: ac_simps)
   qed
-  then show ?thesis
-    by (simp add: of_signed_def algebra_simps)
 qed
 
-lemma of_signed_bits_of_int:
-  "of_signed (bits_of (of_int k)) = of_int k"
-  by (cases k rule: int_cases)
-    (simp_all add: of_signed_bits_of_nat of_signed_bits_neg_of_nat)
+lemma self [simp]:
+  "k \<^bold>\<times> k = (case (False \<^bold>* False, True \<^bold>* True)
+    of (False, False) \<Rightarrow> 0
+     | (False, True) \<Rightarrow> k
+     | (True, True) \<Rightarrow> - 1)"
+  by (induction k rule: int_bit_induct) (auto simp add: False_False_imp_True_True split: bool.split)
+
+lemma even_iff [simp]:
+  "even (k \<^bold>\<times> l) \<longleftrightarrow> \<not> (odd k \<^bold>* odd l)"
+proof (induction k arbitrary: l rule: int_bit_induct)
+  case zero
+  show ?case
+    by (cases "even l") (simp_all split: bool.splits)
+next
+  case minus
+  show ?case
+    by (cases "even l") (simp_all split: bool.splits)
+next
+  case (even k)
+  then show ?case
+    by (simp add: rec [of "k * 2"])
+next
+  case (odd k)
+  then show ?case
+    by (simp add: rec [of "1 + k * 2"])
+qed
+
+lemma of_bits:
+  "of_bits bs \<^bold>\<times> of_bits cs = (of_bits (map2 (\<^bold>*) bs cs) :: int)"
+    if "length bs = length cs" and "\<not> False \<^bold>* False" for bs cs
+using \<open>length bs = length cs\<close> proof (induction bs cs rule: list_induct2)
+  case Nil
+  then show ?case
+    using \<open>\<not> False \<^bold>* False\<close> by (auto simp add: False_False_imp_True_True split: bool.splits)
+next
+  case (Cons b bs c cs)
+  show ?case
+  proof (cases "bs = []")
+    case True
+    with Cons show ?thesis
+      using \<open>\<not> False \<^bold>* False\<close> by (cases b; cases c)
+        (auto simp add: ac_simps split: bool.splits)
+  next
+    case False
+    with Cons.hyps have "cs \<noteq> []"
+      by auto
+    with \<open>bs \<noteq> []\<close> have "map2 (\<^bold>*) bs cs \<noteq> []"
+      by (simp add: zip_eq_Nil_iff)
+    from \<open>bs \<noteq> []\<close> \<open>cs \<noteq> []\<close> \<open>map2 (\<^bold>*) bs cs \<noteq> []\<close> Cons show ?thesis
+      by (cases b; cases c)
+        (auto simp add: \<open>\<not> False \<^bold>* False\<close> ac_simps
+          rec [of "of_bits bs * 2"] rec [of "of_bits cs * 2"]
+          rec [of "1 + of_bits bs * 2"])
+  qed
+qed
 
 end
 
-instance int :: ring_bits
-  by standard auto
+instantiation int :: bit_operations
+begin
+
+definition not_int :: "int \<Rightarrow> int"
+  where "not_int = complement"
+
+global_interpretation and_int: zip_int "(\<and>)"
+  defines and_int = and_int.F
+  by standard
+
+declare and_int.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
+
+global_interpretation and_int: semilattice "(AND) :: int \<Rightarrow> int \<Rightarrow> int"
+proof (rule semilattice.intro, fact and_int.abel_semigroup_axioms, standard)
+  show "k AND k = k" for k :: int
+    by (simp add: and_int.self)
+qed
+
+lemma zero_int_and_eq [simp]:
+  "0 AND k = 0" for k :: int
+  by simp
+
+lemma and_zero_int_eq [simp]:
+  "k AND 0 = 0" for k :: int
+  by simp
+
+lemma minus_int_and_eq [simp]:
+  "- 1 AND k = k" for k :: int
+  by simp
+
+lemma and_minus_int_eq [simp]:
+  "k AND - 1 = k" for k :: int
+  by simp
+
+global_interpretation or_int: zip_int "(\<or>)"
+  defines or_int = or_int.F
+  by standard
+
+declare or_int.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
+
+global_interpretation or_int: semilattice "(OR) :: int \<Rightarrow> int \<Rightarrow> int"
+proof (rule semilattice.intro, fact or_int.abel_semigroup_axioms, standard)
+  show "k OR k = k" for k :: int
+    by (simp add: or_int.self)
+qed
+
+lemma zero_int_or_eq [simp]:
+  "0 OR k = k" for k :: int
+  by simp
+
+lemma and_zero_or_eq [simp]:
+  "k OR 0 = k" for k :: int
+  by simp
+
+lemma minus_int_or_eq [simp]:
+  "- 1 OR k = - 1" for k :: int
+  by simp
 
-lemma of_signed_bits_of:
-  "of_signed (bits_of k) = k" for k :: int
-  using of_signed_bits_of_int [of k, where ?'a = int] by simp
+lemma or_minus_int_eq [simp]:
+  "k OR - 1 = - 1" for k :: int
+  by simp
+
+global_interpretation xor_int: zip_int "(\<noteq>)"
+  defines xor_int = xor_int.F
+  by standard
+
+declare xor_int.simps [simp] \<comment> \<open>inconsistent declaration handling by
+  \<open>global_interpretation\<close> in \<open>instantiation\<close>\<close>
+
+lemma zero_int_xor_eq [simp]:
+  "0 XOR k = k" for k :: int
+  by simp
+
+lemma and_zero_xor_eq [simp]:
+  "k XOR 0 = k" for k :: int
+  by simp
+
+lemma minus_int_xor_eq [simp]:
+  "- 1 XOR k = complement k" for k :: int
+  by simp
+
+lemma xor_minus_int_eq [simp]:
+  "k XOR - 1 = complement k" for k :: int
+  by simp
+
+definition shift_left_int :: "int \<Rightarrow> nat \<Rightarrow> int"
+  where [simp]: "k << n = push_bit n k" for k :: int
+
+definition shift_right_int :: "int \<Rightarrow> nat \<Rightarrow> int"
+  where [simp]: "k >> n = drop_bit n k" for k :: int
+
+instance proof
+  show "semilattice ((AND) :: int \<Rightarrow> _)"
+    by (fact and_int.semilattice_axioms)
+  show "semilattice ((OR) :: int \<Rightarrow> _)"
+    by (fact or_int.semilattice_axioms)
+  show "abel_semigroup ((XOR) :: int \<Rightarrow> _)"
+    by (fact xor_int.abel_semigroup_axioms)
+  show "(not :: int \<Rightarrow> _) = of_bits \<circ> map Not \<circ> bits_of"
+  proof (rule sym, rule ext)
+    fix k :: int
+    show "(of_bits \<circ> map Not \<circ> bits_of) k = NOT k"
+      by (induction k rule: int_bit_induct) (simp_all add: not_int_def)
+  qed
+  show "of_bits bs AND of_bits cs = (of_bits (map2 (\<and>) bs cs) :: int)"
+    if "length bs = length cs" for bs cs
+    using that by (rule and_int.of_bits) simp
+  show "of_bits bs OR of_bits cs = (of_bits (map2 (\<or>) bs cs) :: int)"
+    if "length bs = length cs" for bs cs
+    using that by (rule or_int.of_bits) simp
+  show "of_bits bs XOR of_bits cs = (of_bits (map2 (\<noteq>) bs cs) :: int)"
+    if "length bs = length cs" for bs cs
+    using that by (rule xor_int.of_bits) simp
+  show "k << n = of_bits (replicate n False @ bits_of k)"
+    for k :: int and n :: nat
+    by (cases "n = 0") simp_all
+  show "k >> n = of_bits (drop n (bits_of k))"
+    if "n < length (bits_of k)"
+    for k :: int and n :: nat
+    using that by simp
+qed
 
 end
+
+global_interpretation and_int: semilattice_neutr "(AND)" "- 1 :: int"
+  by standard simp
+
+global_interpretation or_int: semilattice_neutr "(OR)" "0 :: int"
+  by standard simp
+
+global_interpretation xor_int: comm_monoid "(XOR)" "0 :: int"
+  by standard simp
+
+lemma not_int_simps [simp]:
+  "NOT 0 = (- 1 :: int)"
+  "NOT - 1 = (0 :: int)"
+  "k \<noteq> 0 \<Longrightarrow> k \<noteq> - 1 \<Longrightarrow> NOT k = of_bool (even k) + 2 * NOT (k div 2)" for k :: int
+  by (auto simp add: not_int_def elim: oddE)
+
+lemma not_one_int [simp]:
+  "NOT 1 = (- 2 :: int)"
+  by simp
+
+lemma one_and_int_eq [simp]:
+  "1 AND k = k mod 2" for k :: int
+  using and_int.rec [of 1] by (simp add: mod2_eq_if)
+
+lemma and_one_int_eq [simp]:
+  "k AND 1 = k mod 2" for k :: int
+  using one_and_int_eq [of 1] by (simp add: ac_simps)
+
+lemma one_or_int_eq [simp]:
+  "1 OR k = k + of_bool (even k)" for k :: int
+  using or_int.rec [of 1] by (auto elim: oddE)
+
+lemma or_one_int_eq [simp]:
+  "k OR 1 = k + of_bool (even k)" for k :: int
+  using one_or_int_eq [of k] by (simp add: ac_simps)
+
+lemma one_xor_int_eq [simp]:
+  "1 XOR k = k + of_bool (even k) - of_bool (odd k)" for k :: int
+  using xor_int.rec [of 1] by (auto elim: oddE)
+
+lemma xor_one_int_eq [simp]:
+  "k XOR 1 = k + of_bool (even k) - of_bool (odd k)" for k :: int
+  using one_xor_int_eq [of k] by (simp add: ac_simps)
+
+end