Re: [Caml-list] Weak hash table

[Jean-Christophe Filliatre <Jean-Christophe.Filliatre@lri.fr>]

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Christophe Raffalli writes:
 > 
 > did anyone implemented weak hash table using weak pointers in OCaml ?
 > 
 > I need that, and if I can save work ...

I did  it once,  but a very  naive implementation with  only functions
"create",  "add" and  "find" (I  finally ended  using some  other data
structure,  so I  didn't pursue).  Anyhow,  I attach  these two  small
files.

-- 
Jean-Christophe Filliâtre (http://www.lri.fr/~filliatr)


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type ('a,'b) t

val create : int -> ('a,'b) t

val add : ('a,'b) t -> 'a -> 'b -> unit

val find : ('a,'b) t -> 'a -> 'b



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type ('a,'b) t = ('a * 'b) list Weak.t

let create = Weak.create

let add t x y =
  let n = Weak.length t in
  let i = (Hashtbl.hash x) mod n in
  let old  = match Weak.get t i with
    | None -> []
    | Some l -> l
  in
  Weak.set t i (Some ((x,y) :: old))

let find t x =
  let n = Weak.length t in
  let i = (Hashtbl.hash x) mod n in
  match Weak.get t i with
    | None -> raise Not_found
    | Some l -> List.assoc x l