two target language numeral types: integer and natural, as replacement for code_numeral;
former theory HOL/Library/Code_Numeral_Types replaces HOL/Code_Numeral;
refined stack of theories implementing int and/or nat by target language numerals;
reduced number of target language numeral types to exactly one
(* 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_Target_Int 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: fun_eq_iff)
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: fun_eq_iff)
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 "Prelude.toInteger (Prelude.fromEnum (_ :: Prelude.Char))" and "!(let chr k | (0 <= k && k < 256) = Prelude.toEnum k :: Prelude.Char in chr . Prelude.fromInteger)")
(Scala "BigInt(_.toInt)" and "!((k: BigInt) => if (BigInt(0) <= k && k < BigInt(256)) k.charValue else error(\"character value out of range\"))")
end