source: trunk/abcl/src/org/armedbear/lisp/lcm.lisp @ 14196

Last change on this file since 14196 was 11391, checked in by vvoutilainen, 12 years ago

ABCL license is GPL + Classpath exception. This was intended
by Peter Graves, the original author. For reference, see
http://sourceforge.net/mailarchive/forum.php?thread_name=20040721115302.839%40prufrock&forum_name=armedbear-j-announce

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 2.1 KB
Line 
1;;; lcm.lisp
2;;;
3;;; Copyright (C) 2003 Peter Graves
4;;; $Id: lcm.lisp 11391 2008-11-15 22:38:34Z vvoutilainen $
5;;;
6;;; This program is free software; you can redistribute it and/or
7;;; modify it under the terms of the GNU General Public License
8;;; as published by the Free Software Foundation; either version 2
9;;; of the License, or (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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
19;;;
20;;; As a special exception, the copyright holders of this library give you
21;;; permission to link this library with independent modules to produce an
22;;; executable, regardless of the license terms of these independent
23;;; modules, and to copy and distribute the resulting executable under
24;;; terms of your choice, provided that you also meet, for each linked
25;;; independent module, the terms and conditions of the license of that
26;;; module.  An independent module is a module which is not derived from
27;;; or based on this library.  If you modify this library, you may extend
28;;; this exception to your version of the library, but you are not
29;;; obligated to do so.  If you do not wish to do so, delete this
30;;; exception statement from your version.
31
32(in-package "SYSTEM")
33
34(defun two-arg-lcm (n m)
35  (cond ((zerop n) 0)
36        ((zerop m) 0)
37        (t
38         (/ (abs (* n m)) (gcd n m)))))
39
40(defun lcm (&rest integers)
41  (unless (every #'integerp integers)
42    (error 'type-error :datum (find-if-not #'integerp integers) :expected-type 'integer))
43  (case (length integers)
44    (0 1)
45    (1 (abs (car integers)))
46    (2 (two-arg-lcm (car integers) (cadr integers)))
47    (t
48     (do ((result (car integers) (two-arg-lcm result (car rest)))
49          (rest (cdr integers) (cdr rest)))
50         ((null rest) result)))))
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