src/HOL/Tools/numeral_syntax.ML
 author berghofe Wed, 13 Nov 2002 15:28:41 +0100 changeset 13708 a3a410782c95 parent 13495 af27202d6d1c child 14981 e73f8140af78 permissions -rw-r--r--
prove_goal' -> Goal.simple_prove_goal_cterm
```
(*  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

(* bits *)

fun dest_bit (Const ("False", _)) = 0
| dest_bit (Const ("True", _)) = 1
| dest_bit _ = raise Match;

(* 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 bin_of (Const ("bin.Pls", _)) = []
| bin_of (Const ("bin.Min", _)) = [~1]
| bin_of (Const ("Bit", _) \$ bs \$ b) = dest_bit b :: bin_of bs
| bin_of _ = raise Match;

val dest_bin = HOLogic.int_of o bin_of;

fun dest_bin_str tm =
let
val rev_digs = bin_of tm;
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 = string_of_int (abs i);
in
if i = 0 orelse i = 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 (Syntax.read_xnum 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 false ["Numeral.bin.Pls", "Numeral.bin.Min"],
Theory.add_trfuns ([], [("_Numeral", numeral_tr)], [], []),