(*  Title:      HOL/Library/Code_Char_chr.thy

     ID:         $Id$

     Author:     Florian Haftmann

 *)

 header {* Code generation of pretty characters with character codes *}

 theory Code_Char_chr

 imports Char_nat Code_Char Code_Integer

 begin

 definition

   "int_of_char = int o nat_of_char"

 lemma [code func]:

   "nat_of_char = nat o int_of_char"

   unfolding int_of_char_def by (simp add: expand_fun_eq)

 definition

   "char_of_int = char_of_nat o nat"

 lemma [code func]:

   "char_of_nat = char_of_int o int"

   unfolding char_of_int_def by (simp add: expand_fun_eq)

 lemmas [code func del] = char.recs char.cases char.size

 lemma [code func, code inline]:

   "char_rec f c = split f (nibble_pair_of_nat (nat_of_char c))"

   by (cases c) (auto simp add: nibble_pair_of_nat_char)

 lemma [code func, code inline]:

   "char_case f c = split f (nibble_pair_of_nat (nat_of_char c))"

   by (cases c) (auto simp add: nibble_pair_of_nat_char)

 lemma [code func]:

   "size (c\<Colon>char) = 0"

   by (cases c) auto

 code_const int_of_char and char_of_int

   (SML "!(IntInf.fromInt o Char.ord)" and "!(Char.chr o IntInf.toInt)")

   (OCaml "Big'_int.big'_int'_of'_int (Char.code _)" and "Char.chr (Big'_int.int'_of'_big'_int _)")

   (Haskell "toInteger (fromEnum (_ :: Char))" and "!(let chr k | k < 256 = toEnum k :: Char in chr . fromInteger)")

 end