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module type S = sig
type key
type 'a t
val create: unit -> 'a t
val fold: 'a t -> (key -> 'a -> 'b -> 'b) -> 'b -> 'b
val clear: 'a t -> unit
val add: 'a t -> key -> 'a -> unit
val find: 'a t -> key -> 'a
val mem: 'a t -> key -> bool
val remove: 'a t -> key -> unit
end
type key = int
type 'a t = 'a option array ref
let create () = ref (Array.create 16 None)
let clear t = t := Array.create 16 None
let fold t f x =
let rec aux i x =
if i < 0 then x
else
let x =
match !t.(i) with
| Some y -> f i y x
| None -> x
in
aux (pred i) x
in
aux (pred (Array.length !t)) x
let add t i x =
let l = Array.length !t in
if i >= l then (
let n = max (i + 1) (l * 2) in
let a = Array.create n None in
Array.blit !t 0 a 0 l;
t := a;
);
(!t).(i) <- Some x
let remove t i =
if (i <= Array.length !t) then (!t).(i) <- None
let find t i =
if i >= Array.length !t then raise Not_found
else match (!t).(i) with
| None -> raise Not_found
| Some x -> x
let mem t i =
if i >= Array.length !t then false
else match (!t).(i) with
| None -> false
| Some _ -> true
|