(* Title: HOL/Library/Code_Char_chr.thy
Author: Florian Haftmann
*)
header {* Code generation of pretty characters with character codes *}
theory Code_Char_chr
imports Char_nat Code_Char Code_Integer Main
begin
definition
"int_of_char = int o nat_of_char"
lemma [code]:
"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]:
"char_of_nat = char_of_int o int"
unfolding char_of_int_def by (simp add: expand_fun_eq)
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 | (0 <= k && k < 256) = toEnum k :: Char in chr . fromInteger)")
(Scala "BigInt(_.toInt)" and "!((k: BigInt) => if (BigInt(0) <= k && k < BigInt(256)) k.charValue else error(\"character value out of range\"))")
end