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lfu.hs revision 1.1 
      1 {-
      2 /*	$NetBSD: lfu.hs,v 1.1 2006/10/09 12:32:46 yamt Exp $	*/
      3 
      4 /*-
      5  * Copyright (c)2005 YAMAMOTO Takashi,
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  *
     17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     27  * SUCH DAMAGE.
     28  */
     29 -}
     30 
     31 import System.Environment
     32 import System.IO
     33 import List
     34 import Maybe
     35 import Monad
     36 
     37 pgmatch idx pg = idx == fst pg
     38 
     39 pglookup :: Eq a => a -> [(a,b)] -> Maybe (a,b)
     40 pglookup x = find (pgmatch x)
     41 
     42 pgdequeue :: Eq a => a -> [a] -> [a]
     43 pgdequeue = delete
     44 
     45 victim :: Ord b => [(a,b)] -> (a,b)
     46 victim = minimumBy p where
     47 	p x y = compare (snd x) (snd y)
     48 
     49 do_lfu1 npg n q qlen [] = (reverse n, q)
     50 do_lfu1 npg n q qlen rs@(r:rs2) =
     51 	let
     52 		p = pglookup r q
     53 	in
     54 	if isJust p then
     55 		let
     56 			opg = fromJust p
     57 			nq = pgdequeue opg q
     58 			pg = (fst opg, snd opg + 1)
     59 		in
     60 		do_lfu1 npg n (pg:nq) qlen rs2
     61 	else if qlen < npg then
     62 		do_lfu1 npg (r:n) ((r,1):q) (qlen+1) rs2
     63 	else
     64 		let
     65 			opg = victim q
     66 			nq = pgdequeue opg q
     67 		in
     68 		do_lfu1 npg (r:n) ((r,1):nq) qlen rs2
     69 
     70 do_lfu npg rs = fst $ do_lfu1 npg [] [] 0 rs
     71 
     72 main = do
     73 	xs <- getContents
     74 	args <- getArgs
     75 	let
     76 		ls = lines xs
     77 		npgs::Int
     78 		npgs = read $ args !! 0
     79 		pgs::[Int]
     80 		pgs = map read ls
     81 	mapM_ print $ do_lfu npgs pgs
     82