(* Title: HOL/Tools/numeral_syntax.ML
ID: $Id$
Author: Markus Wenzel, TU Muenchen
Concrete syntax for generic numerals. Assumes consts and syntax of
theory HOL/Numeral.
*)
signature NUMERAL_SYNTAX =
sig
val setup: (theory -> theory) list
end;
structure NumeralSyntax: NUMERAL_SYNTAX =
struct
(* bit strings *) (*we try to handle superfluous leading digits nicely*)
fun prefix_len _ [] = 0
| prefix_len pred (x :: xs) =
if pred x then 1 + prefix_len pred xs else 0;
fun dest_bin_str tm =
let
val rev_digs = HOLogic.bin_of tm handle TERM _ => raise Match
val (sign, zs) =
(case rev rev_digs of
~1 :: bs => ("-", prefix_len (equal 1) bs)
| bs => ("", prefix_len (equal 0) bs));
val i = HOLogic.int_of rev_digs;
val num = IntInf.toString (IntInf.abs i);
in
if i = IntInf.fromInt 0 orelse i = IntInf.fromInt 1 then raise Match
else sign ^ implode (replicate zs "0") ^ num
end;
(* translation of integer numeral tokens to and from bitstrings *)
fun numeral_tr (*"_Numeral"*) [t as Const (str, _)] =
(Syntax.const "Numeral.number_of" $ (HOLogic.mk_bin (valOf (IntInf.fromString str))))
| numeral_tr (*"_Numeral"*) ts = raise TERM ("numeral_tr", ts);
fun numeral_tr' show_sorts (*"number_of"*) (Type ("fun", [_, T])) (t :: ts) =
let val t' = Syntax.const "_Numeral" $ Syntax.free (dest_bin_str t) in
if not (! show_types) andalso can Term.dest_Type T then t'
else Syntax.const Syntax.constrainC $ t' $ Syntax.term_of_typ show_sorts T
end
| numeral_tr' _ (*"number_of"*) T (t :: ts) =
if T = dummyT then Syntax.const "_Numeral" $ Syntax.free (dest_bin_str t)
else raise Match
| numeral_tr' _ (*"number_of"*) _ _ = raise Match;
(* theory setup *)
val setup =
[Theory.hide_consts_i false ["Numeral.Pls", "Numeral.Min"],
Theory.hide_consts_i false ["Numeral.bit.B0", "Numeral.bit.B1"],
Theory.add_trfuns ([], [("_Numeral", numeral_tr)], [], []),
Theory.add_trfunsT [("number_of", numeral_tr'), ("Numeral.number_of", numeral_tr')]];
end;