source: trunk/abcl/src/org/armedbear/lisp/butlast.lisp @ 14207

Last change on this file since 14207 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: 2.5 KB
Line 
1;;; butlast.lisp
2;;;
3;;; Copyright (C) 2003 Peter Graves
4;;; $Id: butlast.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 "COMMON-LISP")
33
34(export '(butlast nbutlast))
35
36(defun butlast (list &optional (n 1))
37  (unless (and (listp list) (typep n '(integer 0)))
38    (error 'type-error))
39  (unless (null list)
40    (let ((length (do ((list list (cdr list))
41           (i 0 (1+ i)))
42                      ((atom list) (1- i)))))
43      (unless (< length n)
44  (do* ((top (cdr list) (cdr top))
45        (result (list (car list)))
46        (splice result)
47        (count length (1- count)))
48             ((= count n) result)
49    (setq splice (cdr (rplacd splice (list (car top))))))))))
50
51(defun nbutlast (list &optional (n 1))
52  (unless (and (listp list) (typep n '(integer 0)))
53    (error 'type-error))
54  (unless (null list)
55    (let ((length (do ((list list (cdr list))
56           (i 0 (1+ i)))
57                      ((atom list) (1- i)))))
58      (unless (< length n)
59  (do ((1st (cdr list) (cdr 1st))
60       (2nd list 1st)
61       (count length (1- count)))
62            ((= count n)
63             (rplacd 2nd ())
64             list))))))
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