cannam@127: (*
cannam@127:  * Copyright (c) 1997-1999 Massachusetts Institute of Technology
cannam@127:  * Copyright (c) 2003, 2007-14 Matteo Frigo
cannam@127:  * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology
cannam@127:  *
cannam@127:  * This program is free software; you can redistribute it and/or modify
cannam@127:  * it under the terms of the GNU General Public License as published by
cannam@127:  * the Free Software Foundation; either version 2 of the License, or
cannam@127:  * (at your option) any later version.
cannam@127:  *
cannam@127:  * This program is distributed in the hope that it will be useful,
cannam@127:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
cannam@127:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
cannam@127:  * GNU General Public License for more details.
cannam@127:  *
cannam@127:  * You should have received a copy of the GNU General Public License
cannam@127:  * along with this program; if not, write to the Free Software
cannam@127:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
cannam@127:  *
cannam@127:  *)
cannam@127: 
cannam@127: (*************************************************************
cannam@127:  *    Functional associative table
cannam@127:  *************************************************************)
cannam@127: 
cannam@127: (* 
cannam@127:  * this module implements a functional associative table.  
cannam@127:  * The table is parametrized by an equality predicate and
cannam@127:  * a hash function, with the restriction that (equal a b) ==>
cannam@127:  * hash a == hash b.
cannam@127:  * The table is purely functional and implemented using a binary
cannam@127:  * search tree (not balanced for now)
cannam@127:  *)
cannam@127: 
cannam@127: type ('a, 'b) elem = 
cannam@127:     Leaf 
cannam@127:   | Node of int * ('a, 'b) elem * ('a, 'b) elem * ('a * 'b) list
cannam@127: 
cannam@127: let empty = Leaf
cannam@127: 
cannam@127: let lookup hash equal key table =
cannam@127:   let h = hash key in
cannam@127:   let rec look = function
cannam@127:       Leaf -> None
cannam@127:     | Node (hash_key, left, right, this_list) ->
cannam@127:         if (hash_key < h) then look left
cannam@127:         else if (hash_key > h) then look right
cannam@127:         else let rec loop = function
cannam@127:             [] -> None
cannam@127:           | (a, b) :: rest -> if (equal key a) then Some b else loop rest
cannam@127:         in loop this_list
cannam@127:   in look table
cannam@127: 
cannam@127: let insert hash key value table =
cannam@127:   let h = hash key in
cannam@127:   let rec ins = function
cannam@127:       Leaf -> Node (h, Leaf, Leaf, [(key, value)])
cannam@127:     | Node (hash_key, left, right, this_list) ->
cannam@127:         if (hash_key < h) then 
cannam@127:           Node (hash_key, ins left, right, this_list)
cannam@127:         else if (hash_key > h) then 
cannam@127:           Node (hash_key, left, ins right, this_list)
cannam@127:         else 
cannam@127:           Node (hash_key, left, right, (key, value) :: this_list)
cannam@127:   in ins table