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(*
*
* Copyright (c) 2001-2002,
* John Kodumal <jkodumal@eecs.berkeley.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. The names of the contributors may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
* IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
* OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*)
exception Bad_find
type 'a urefC =
Ecr of 'a * int
| Link of 'a uref
and 'a uref = 'a urefC ref
let rec find p =
match !p with
| Ecr _ -> p
| Link p' ->
let p'' = find p'
in p := Link p''; p''
let uref x = ref (Ecr(x,0))
let equal (p,p') = (find p == find p')
let deref p =
match ! (find p) with
| Ecr (x,_) -> x
| _ -> raise Bad_find
let update (p,x) =
let p' = find p
in
match !p' with
| Ecr (_,rank) -> p' := Ecr(x,rank)
| _ -> raise Bad_find
let unify f (p,q) =
let p',q' = find p, find q in
match (!p',!q') with
| (Ecr(px,pr),Ecr(qx,qr)) ->
let x = f(px,qx) in
if (p' == q') then
p' := Ecr(x,pr)
else if pr == qr then
(q' := Ecr(x,qr+1); p' := Link q')
else if pr < qr then
(q' := Ecr(x,qr); p' := Link q')
else (* pr > qr *)
(p' := Ecr(x,pr); q' := Link p')
| _ -> raise Bad_find
let union (p,q) =
let p',q' = find p, find q in
match (!p',!q') with
| (Ecr(px,pr),Ecr(qx,qr)) ->
if (p' == q') then
()
else if pr == qr then
(q' := Ecr(qx, qr+1); p' := Link q')
else if pr < qr then
p' := Link q'
else (* pr > qr *)
q' := Link p'
| _ -> raise Bad_find
|
