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(***********************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA-Rocquencourt & LRI-CNRS-Orsay *)
(* \VV/ *************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(***********************************************************************)
(*** This module implements an "untyped store", in this particular case we
see it as an extensible record whose fields are left unspecified. ***)
(* We give a short implementation of a universal type. This is mostly equivalent
to what is proposed by module Dyn.ml, except that it requires no explicit tag. *)
module type Universal = sig
type t
type 'a etype = {
put : 'a -> t ;
get : t -> 'a option
}
val embed : unit -> 'a etype
end
(* We use a dynamic "name" allocator. But if we needed to serialise stores, we
might want something static to avoid troubles with plugins order. *)
let next =
let count = ref 0 in fun () ->
let n = !count in
incr count;
n
type t = Obj.t Util.Intmap.t
module Field = struct
type 'a field = {
set : 'a -> t -> t ;
get : t -> 'a option ;
remove : t -> t
}
type 'a t = 'a field
end
open Field
let empty = Util.Intmap.empty
let field () =
let fid = next () in
let set a s =
Util.Intmap.add fid (Obj.repr a) s
in
let get s =
try Some (Obj.obj (Util.Intmap.find fid s))
with _ -> None
in
let remove s =
Util.Intmap.remove fid s
in
{ set = set ; get = get ; remove = remove }
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