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