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|
(************************************************************************)
(* v * The Coq Proof Assistant / The Coq Development Team *)
(* <O___,, * INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2015 *)
(* \VV/ **************************************************************)
(* // * This file is distributed under the terms of the *)
(* * GNU Lesser General Public License Version 2.1 *)
(************************************************************************)
open Errors
open Pp
module type S =
sig
type 'a tag
type t = Dyn : 'a tag * 'a -> t
val create : string -> 'a tag
val eq : 'a tag -> 'b tag -> ('a, 'b) CSig.eq option
val repr : 'a tag -> string
val dump : unit -> (int * string) list
end
module Make(M : CSig.EmptyS) =
struct
(* Dynamics, programmed with DANGER !!! *)
type 'a tag = int
type t = Dyn : 'a tag * 'a -> t
let dyntab = ref (Int.Map.empty : string Int.Map.t)
(** Instead of working with tags as strings, which are costly, we use their
hash. We ensure unicity of the hash in the [create] function. If ever a
collision occurs, which is unlikely, it is sufficient to tweak the offending
dynamic tag. *)
let create (s : string) =
let hash = Hashtbl.hash s in
let () =
if Int.Map.mem hash !dyntab then
let old = Int.Map.find hash !dyntab in
let msg = str "Dynamic tag collision: " ++ str s ++ str " vs. " ++ str old in
anomaly ~label:"Dyn.create" msg
in
let () = dyntab := Int.Map.add hash s !dyntab in
hash
let eq : 'a 'b. 'a tag -> 'b tag -> ('a, 'b) CSig.eq option =
fun h1 h2 -> if Int.equal h1 h2 then Some (Obj.magic CSig.Refl) else None
let repr s =
try Int.Map.find s !dyntab
with Not_found ->
anomaly (str "Unknown dynamic tag " ++ int s)
let dump () = Int.Map.bindings !dyntab
end
|
