Source file `InfiniteArray.ml`

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(******************************************************************************)
(*                                                                            *)
(*                                  Inferno                                   *)
(*                                                                            *)
(*                       François Pottier, Inria Paris                        *)
(*                                                                            *)
(*  Copyright Inria. All rights reserved. This file is distributed under the  *)
(*  terms of the MIT License, as described in the file LICENSE.               *)
(*                                                                            *)
(******************************************************************************)

(** This module implements infinite arrays, that is, arrays that grow
    transparently upon demand. *)

type 'a t = {
    default: 'a;
    mutable table: 'a array;
  } 

let make default_size x = {
  default = x;
  table = Array.make default_size x;
} 

let rec new_length length i =
  if i < length then
    length
  else
    new_length (2 * length) i

let ensure a i =
  let table = a.table in
  let length = Array.length table in
  if i >= length then begin
    let table' = Array.make (new_length (2 * length) i) a.default in
    Array.blit table 0 table' 0 length;
    a.table <- table'
  end

let get a i =
  ensure a i;
  a.table.(i)

let set a i x =
  ensure a i;
  a.table.(i) <- x