home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
OS/2 Shareware BBS: 10 Tools
/
10-Tools.zip
/
mitsch75.zip
/
scheme-7_5_17-src.zip
/
scheme-7.5.17
/
src
/
runtime
/
qsort.scm
< prev
next >
Wrap
Text File
|
1999-01-02
|
2KB
|
76 lines
#| -*-Scheme-*-
$Id: qsort.scm,v 14.4 1999/01/02 06:11:34 cph Exp $
Copyright (c) 1988-1999 Massachusetts Institute of Technology
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at
your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
|#
;;;; Quick Sort
;;; package: ()
(declare (usual-integrations))
(define (quick-sort vector predicate)
(if (vector? vector)
(quick-sort! (vector-copy vector) predicate)
(vector->list (quick-sort! (list->vector vector) predicate))))
(define (quick-sort! vector predicate)
(define (outer-loop l r)
(if (fix:> r l)
(if (fix:= r (fix:+ l 1))
(if (predicate (vector-ref vector r)
(vector-ref vector l))
(exchange! l r))
(let ((lth-element (vector-ref vector l)))
(define (increase-i i)
(if (or (fix:> i r)
(predicate lth-element (vector-ref vector i)))
i
(increase-i (fix:+ i 1))))
(define (decrease-j j)
(if (or (fix:<= j l)
(not (predicate lth-element (vector-ref vector j))))
j
(decrease-j (fix:- j 1))))
(define (inner-loop i j)
(if (fix:< i j) ;used to be <=
(begin
(exchange! i j)
(inner-loop (increase-i (fix:+ i 1))
(decrease-j (fix:- j 1))))
(begin
(if (fix:> j l)
(exchange! j l))
(outer-loop (fix:+ j 1) r)
(outer-loop l (fix:- j 1)))))
(inner-loop (increase-i (fix:+ l 1))
(decrease-j r))))))
(define-integrable (exchange! i j)
(let ((ith-element (vector-ref vector i)))
(vector-set! vector i (vector-ref vector j))
(vector-set! vector j ith-element)))
(if (not (vector? vector))
(error:wrong-type-argument vector "vector" 'QUICK-SORT!))
(outer-loop 0 (fix:- (vector-length vector) 1))
vector)