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|
(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * CNRS-Ecole Polytechnique-INRIA Futurs-Universite Paris Sud *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
(* $Id$ *)
(* This file defines the printer for natural numbers in [nat] *)
(*i*)
open Pcoq
open Pp
open Util
open Names
open Coqlib
open Rawterm
open Libnames
open Bigint
open Coqlib
open Notation
open Pp
open Util
open Names
(*i*)
(**********************************************************************)
(* Parsing via scopes *)
(* For example, (nat_of_string "3") is <<(S (S (S O)))>> *)
let nat_of_int dloc n =
if is_pos_or_zero n then begin
if less_than (of_string "5000") n & Options.is_verbose () then begin
warning ("You may experience stack overflow and segmentation fault\
\nwhile parsing numbers in nat greater than 5000");
flush_all ()
end;
let ref_O = RRef (dloc, glob_O) in
let ref_S = RRef (dloc, glob_S) in
let rec mk_nat acc n =
if n <> zero then
mk_nat (RApp (dloc,ref_S, [acc])) (sub_1 n)
else
acc
in
mk_nat ref_O n
end
else
user_err_loc (dloc, "nat_of_int",
str "Cannot interpret a negative number as a number of type nat")
(************************************************************************)
(* Printing via scopes *)
exception Non_closed_number
let rec int_of_nat = function
| RApp (_,RRef (_,s),[a]) when s = glob_S -> add_1 (int_of_nat a)
| RRef (_,z) when z = glob_O -> zero
| _ -> raise Non_closed_number
let uninterp_nat p =
try
Some (int_of_nat p)
with
Non_closed_number -> None
(************************************************************************)
(* Declare the primitive parsers and printers *)
let _ =
Notation.declare_numeral_interpreter "nat_scope"
(nat_path,["Coq";"Init";"Datatypes"])
nat_of_int
([RRef (dummy_loc,glob_S); RRef (dummy_loc,glob_O)], uninterp_nat, true)
|
