1(* 2 * Copyright (c) 1997-1999 Massachusetts Institute of Technology 3 * Copyright (c) 2003, 2007-14 Matteo Frigo 4 * Copyright (c) 2003, 2007-14 Massachusetts Institute of Technology 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 19 * 20 *) 21 22(************************************************************* 23 * Functional associative table 24 *************************************************************) 25 26(* 27 * this module implements a functional associative table. 28 * The table is parametrized by an equality predicate and 29 * a hash function, with the restriction that (equal a b) ==> 30 * hash a == hash b. 31 * The table is purely functional and implemented using a binary 32 * search tree (not balanced for now) 33 *) 34 35type ('a, 'b) elem = 36 Leaf 37 | Node of int * ('a, 'b) elem * ('a, 'b) elem * ('a * 'b) list 38 39let empty = Leaf 40 41let lookup hash equal key table = 42 let h = hash key in 43 let rec look = function 44 Leaf -> None 45 | Node (hash_key, left, right, this_list) -> 46 if (hash_key < h) then look left 47 else if (hash_key > h) then look right 48 else let rec loop = function 49 [] -> None 50 | (a, b) :: rest -> if (equal key a) then Some b else loop rest 51 in loop this_list 52 in look table 53 54let insert hash key value table = 55 let h = hash key in 56 let rec ins = function 57 Leaf -> Node (h, Leaf, Leaf, [(key, value)]) 58 | Node (hash_key, left, right, this_list) -> 59 if (hash_key < h) then 60 Node (hash_key, ins left, right, this_list) 61 else if (hash_key > h) then 62 Node (hash_key, left, ins right, this_list) 63 else 64 Node (hash_key, left, right, (key, value) :: this_list) 65 in ins table 66