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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. *)
(* We use a dynamic "name" allocator. But if we needed to serialise stores, we
might want something static to avoid troubles with plugins order. *)
module type T =
sig
end
module type S =
sig
type t
type 'a field
val empty : t
val set : t -> 'a field -> 'a -> t
val get : t -> 'a field -> 'a option
val remove : t -> 'a field -> t
val merge : t -> t -> t
val field : unit -> 'a field
end
module Make (M : T) : S =
struct
let next =
let count = ref 0 in fun () ->
let n = !count in
incr count;
n
type t = Obj.t Int.Map.t
type 'a field = int
let empty = Int.Map.empty
let set s (id : 'a field) (x : 'a) = Int.Map.add id (Obj.repr x) s
let get s (id : 'a field) : 'a option =
try Some (Obj.obj (Int.Map.find id s))
with Not_found -> None
let remove s (id : 'a field) =
Int.Map.remove id s
let merge s1 s2 =
Int.Map.fold Int.Map.add s1 s2
let field () = next ()
end
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