Chris@42: (*
Chris@42:  * Copyright (c) 1997-1999 Massachusetts Institute of Technology
Chris@42:  * Copyright (c) 2003, 2007-14 Matteo Frigo
Chris@42:  * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
Chris@42:  *
Chris@42:  * This program is free software; you can redistribute it and/or modify
Chris@42:  * it under the terms of the GNU General Public License as published by
Chris@42:  * the Free Software Foundation; either version 2 of the License, or
Chris@42:  * (at your option) any later version.
Chris@42:  *
Chris@42:  * This program is distributed in the hope that it will be useful,
Chris@42:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
Chris@42:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
Chris@42:  * GNU General Public License for more details.
Chris@42:  *
Chris@42:  * You should have received a copy of the GNU General Public License
Chris@42:  * along with this program; if not, write to the Free Software
Chris@42:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
Chris@42:  *
Chris@42:  *)
Chris@42: 
Chris@42: (*************************************************************
Chris@42:  *    Functional associative table
Chris@42:  *************************************************************)
Chris@42: 
Chris@42: (* 
Chris@42:  * this module implements a functional associative table.  
Chris@42:  * The table is parametrized by an equality predicate and
Chris@42:  * a hash function, with the restriction that (equal a b) ==>
Chris@42:  * hash a == hash b.
Chris@42:  * The table is purely functional and implemented using a binary
Chris@42:  * search tree (not balanced for now)
Chris@42:  *)
Chris@42: 
Chris@42: type ('a, 'b) elem = 
Chris@42:     Leaf 
Chris@42:   | Node of int * ('a, 'b) elem * ('a, 'b) elem * ('a * 'b) list
Chris@42: 
Chris@42: let empty = Leaf
Chris@42: 
Chris@42: let lookup hash equal key table =
Chris@42:   let h = hash key in
Chris@42:   let rec look = function
Chris@42:       Leaf -> None
Chris@42:     | Node (hash_key, left, right, this_list) ->
Chris@42:         if (hash_key < h) then look left
Chris@42:         else if (hash_key > h) then look right
Chris@42:         else let rec loop = function
Chris@42:             [] -> None
Chris@42:           | (a, b) :: rest -> if (equal key a) then Some b else loop rest
Chris@42:         in loop this_list
Chris@42:   in look table
Chris@42: 
Chris@42: let insert hash key value table =
Chris@42:   let h = hash key in
Chris@42:   let rec ins = function
Chris@42:       Leaf -> Node (h, Leaf, Leaf, [(key, value)])
Chris@42:     | Node (hash_key, left, right, this_list) ->
Chris@42:         if (hash_key < h) then 
Chris@42:           Node (hash_key, ins left, right, this_list)
Chris@42:         else if (hash_key > h) then 
Chris@42:           Node (hash_key, left, ins right, this_list)
Chris@42:         else 
Chris@42:           Node (hash_key, left, right, (key, value) :: this_list)
Chris@42:   in ins table