(*
* Copyright (c) 1997-1999 Massachusetts Institute of Technology
* Copyright (c) 2003, 2007-11 Matteo Frigo
* Copyright (c) 2003, 2007-11 Massachusetts Institute of Technology
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*)
(*************************************************************
* Functional associative table
*************************************************************)
(*
* this module implements a functional associative table.
* The table is parametrized by an equality predicate and
* a hash function, with the restriction that (equal a b) ==>
* hash a == hash b.
* The table is purely functional and implemented using a binary
* search tree (not balanced for now)
*)
type ('a, 'b) elem =
Leaf
| Node of int * ('a, 'b) elem * ('a, 'b) elem * ('a * 'b) list
let empty = Leaf
let lookup hash equal key table =
let h = hash key in
let rec look = function
Leaf -> None
| Node (hash_key, left, right, this_list) ->
if (hash_key < h) then look left
else if (hash_key > h) then look right
else let rec loop = function
[] -> None
| (a, b) :: rest -> if (equal key a) then Some b else loop rest
in loop this_list
in look table
let insert hash key value table =
let h = hash key in
let rec ins = function
Leaf -> Node (h, Leaf, Leaf, [(key, value)])
| Node (hash_key, left, right, this_list) ->
if (hash_key < h) then
Node (hash_key, ins left, right, this_list)
else if (hash_key > h) then
Node (hash_key, left, ins right, this_list)
else
Node (hash_key, left, right, (key, value) :: this_list)
in ins table