diff --git a/src/HOL/Library/Code_Abstract_Char.thy b/src/HOL/Library/Code_Abstract_Char.thy
--- a/src/HOL/Library/Code_Abstract_Char.thy
+++ b/src/HOL/Library/Code_Abstract_Char.thy
@@ -1,190 +1,190 @@
 (*  Title:      HOL/Library/Code_Abstract_Char.thy
     Author:     Florian Haftmann, TU Muenchen
     Author:     René Thiemann, UIBK
 *)
 
 theory Code_Abstract_Char
   imports 
     Main
     "HOL-Library.Char_ord" 
 begin
 
 definition Chr :: \<open>integer \<Rightarrow> char\<close>
   where [simp]: \<open>Chr = char_of\<close>
 
 lemma char_of_integer_of_char [code abstype]:
   \<open>Chr (integer_of_char c) = c\<close>
   by (simp add: integer_of_char_def)
 
 lemma char_of_integer_code [code]:
-  \<open>integer_of_char (char_of_integer k) = (if 0 \<le> k \<and> k < 256 then k else take_bit 8 k)\<close>
+  \<open>integer_of_char (char_of_integer k) = (if 0 \<le> k \<and> k < 256 then k else k mod 256)\<close>
   by (simp add: integer_of_char_def char_of_integer_def take_bit_eq_mod unique_euclidean_semiring_numeral_class.mod_less)
 
 lemma of_char_code [code]:
   \<open>of_char c = of_nat (nat_of_integer (integer_of_char c))\<close>
 proof -
   have \<open>int_of_integer (of_char c) = of_char c\<close>
     by (cases c) simp
   then show ?thesis
     by (simp add: integer_of_char_def nat_of_integer_def of_nat_of_char)
 qed
 
 definition byte :: \<open>bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> bool \<Rightarrow> integer\<close>
   where [simp]: \<open>byte b0 b1 b2 b3 b4 b5 b6 b7 = horner_sum of_bool 2 [b0, b1, b2, b3, b4, b5, b6, b7]\<close>
 
 lemma byte_code [code]:
   \<open>byte b0 b1 b2 b3 b4 b5 b6 b7 = (
     let
       s0 = if b0 then 1 else 0;
       s1 = if b1 then s0 + 2 else s0;
       s2 = if b2 then s1 + 4 else s1;
       s3 = if b3 then s2 + 8 else s2;
       s4 = if b4 then s3 + 16 else s3;
       s5 = if b5 then s4 + 32 else s4;
       s6 = if b6 then s5 + 64 else s5;
       s7 = if b7 then s6 + 128 else s6
     in s7)\<close>
   by simp
 
 lemma Char_code [code]:
   \<open>integer_of_char (Char b0 b1 b2 b3 b4 b5 b6 b7) = byte b0 b1 b2 b3 b4 b5 b6 b7\<close>
   by (simp add: integer_of_char_def)
-                     
+
 lemma digit_0_code [code]:
   \<open>digit0 c \<longleftrightarrow> bit (integer_of_char c) 0\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_1_code [code]:
   \<open>digit1 c \<longleftrightarrow> bit (integer_of_char c) 1\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_2_code [code]:
   \<open>digit2 c \<longleftrightarrow> bit (integer_of_char c) 2\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_3_code [code]:
   \<open>digit3 c \<longleftrightarrow> bit (integer_of_char c) 3\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_4_code [code]:
   \<open>digit4 c \<longleftrightarrow> bit (integer_of_char c) 4\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_5_code [code]:
   \<open>digit5 c \<longleftrightarrow> bit (integer_of_char c) 5\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_6_code [code]:
   \<open>digit6 c \<longleftrightarrow> bit (integer_of_char c) 6\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma digit_7_code [code]:
   \<open>digit7 c \<longleftrightarrow> bit (integer_of_char c) 7\<close>
   by (cases c) (simp add: integer_of_char_def)
 
 lemma case_char_code [code]:
   \<open>case_char f c = f (digit0 c) (digit1 c) (digit2 c) (digit3 c) (digit4 c) (digit5 c) (digit6 c) (digit7 c)\<close>
   by (fact char.case_eq_if)
 
 lemma rec_char_code [code]:
   \<open>rec_char f c = f (digit0 c) (digit1 c) (digit2 c) (digit3 c) (digit4 c) (digit5 c) (digit6 c) (digit7 c)\<close>
   by (cases c) simp
 
 lemma char_of_code [code]:
   \<open>integer_of_char (char_of a) =
     byte (bit a 0) (bit a 1) (bit a 2) (bit a 3) (bit a 4) (bit a 5) (bit a 6) (bit a 7)\<close>
   by (simp add: char_of_def integer_of_char_def)
 
 lemma ascii_of_code [code]:
   \<open>integer_of_char (String.ascii_of c) = (let k = integer_of_char c in if k < 128 then k else k - 128)\<close>
 proof (cases \<open>of_char c < (128 :: integer)\<close>)
   case True
   moreover have \<open>(of_nat 0 :: integer) \<le> of_nat (of_char c)\<close>
     by simp
   then have \<open>(0 :: integer) \<le> of_char c\<close>
     by (simp only: of_nat_0 of_nat_of_char)
   ultimately show ?thesis
     by (simp add: Let_def integer_of_char_def take_bit_eq_mod unique_euclidean_semiring_numeral_class.mod_less)
 next
   case False
   then have \<open>(128 :: integer) \<le> of_char c\<close>
     by simp
   moreover have \<open>of_nat (of_char c) < (of_nat 256 :: integer)\<close>
     by (simp only: of_nat_less_iff) simp
   then have \<open>of_char c < (256 :: integer)\<close>
     by (simp add: of_nat_of_char)
   moreover define k :: integer where \<open>k = of_char c - 128\<close>
   then have \<open>of_char c = k + 128\<close>
     by simp
   ultimately show ?thesis
     by (simp add: Let_def integer_of_char_def take_bit_eq_mod unique_euclidean_semiring_numeral_class.mod_less)
 qed    
 
 lemma equal_char_code [code]:
   \<open>HOL.equal c d \<longleftrightarrow> integer_of_char c = integer_of_char d\<close>
   by (simp add: integer_of_char_def equal)
 
 lemma less_eq_char_code [code]:
   \<open>c \<le> d \<longleftrightarrow> integer_of_char c \<le> integer_of_char d\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof -
   have \<open>?P \<longleftrightarrow> of_nat (of_char c) \<le> (of_nat (of_char d) :: integer)\<close>
     by (simp add: less_eq_char_def)
   also have \<open>\<dots> \<longleftrightarrow> ?Q\<close>
     by (simp add: of_nat_of_char integer_of_char_def)
   finally show ?thesis .
 qed
 
 lemma less_char_code [code]:
   \<open>c < d \<longleftrightarrow> integer_of_char c < integer_of_char d\<close> (is \<open>?P \<longleftrightarrow> ?Q\<close>)
 proof -
   have \<open>?P \<longleftrightarrow> of_nat (of_char c) < (of_nat (of_char d) :: integer)\<close>
     by (simp add: less_char_def)
   also have \<open>\<dots> \<longleftrightarrow> ?Q\<close>
     by (simp add: of_nat_of_char integer_of_char_def)
   finally show ?thesis .
 qed
 
 lemma absdef_simps:
   \<open>horner_sum of_bool 2 [] = (0 :: integer)\<close>
   \<open>horner_sum of_bool 2 (False # bs) = (0 :: integer) \<longleftrightarrow> horner_sum of_bool 2 bs = (0 :: integer)\<close>
   \<open>horner_sum of_bool 2 (True # bs) = (1 :: integer) \<longleftrightarrow> horner_sum of_bool 2 bs = (0 :: integer)\<close>
   \<open>horner_sum of_bool 2 (False # bs) = (numeral (Num.Bit0 n) :: integer) \<longleftrightarrow> horner_sum of_bool 2 bs = (numeral n :: integer)\<close>
   \<open>horner_sum of_bool 2 (True # bs) = (numeral (Num.Bit1 n) :: integer) \<longleftrightarrow> horner_sum of_bool 2 bs = (numeral n :: integer)\<close>
   by auto (auto simp only: numeral_Bit0 [of n] numeral_Bit1 [of n] mult_2 [symmetric] add.commute [of _ 1] add.left_cancel mult_cancel_left)
 
 local_setup \<open>
   let
     val simps = @{thms absdef_simps integer_of_char_def of_char_Char numeral_One}
     fun prove_eqn lthy n lhs def_eqn =
       let
         val eqn = (HOLogic.mk_Trueprop o HOLogic.mk_eq)
           (\<^term>\<open>integer_of_char\<close> $ lhs, HOLogic.mk_number \<^typ>\<open>integer\<close> n)
       in
         Goal.prove_future lthy [] [] eqn (fn {context = ctxt, ...} =>
           unfold_tac ctxt (def_eqn :: simps))
       end
     fun define n =
       let
         val s = "Char_" ^ String_Syntax.hex n;
         val b = Binding.name s;
         val b_def = Thm.def_binding b;
         val b_code = Binding.name (s ^ "_code");
       in
         Local_Theory.define ((b, Mixfix.NoSyn),
           ((Binding.empty, []), HOLogic.mk_char n))
         #-> (fn (lhs, (_, raw_def_eqn)) =>
           Local_Theory.note ((b_def, @{attributes [code_abbrev]}), [HOLogic.mk_obj_eq raw_def_eqn])
           #-> (fn (_, [def_eqn]) => `(fn lthy => prove_eqn lthy n lhs def_eqn))
           #-> (fn raw_code_eqn => Local_Theory.note ((b_code, []), [raw_code_eqn]))
           #-> (fn (_, [code_eqn]) => Code.declare_abstract_eqn code_eqn))
       end
   in
     fold define (0 upto 255)
   end
 \<close>
 
 code_identifier
   code_module Code_Abstract_Char \<rightharpoonup>
     (SML) Str and (OCaml) Str and (Haskell) Str and (Scala) Str
 
 end