source: trunk/abcl/src/org/armedbear/lisp/reduce.lisp @ 12516

Last change on this file since 12516 was 12516, checked in by astalla, 11 years ago

Support for user-extensible sequences, adapted from SBCL.

  • Property svn:eol-style set to native
  • Property svn:keywords set to Id
File size: 4.0 KB
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1;;; reduce.lisp
2;;;
3;;; Copyright (C) 2003-2005 Peter Graves
4;;; $Id: reduce.lisp 12516 2010-03-03 21:05:41Z astalla $
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;;; Adapted from OpenMCL.
33
34(in-package #:system)
35
36(require "EXTENSIBLE-SEQUENCES-BASE")
37
38(defmacro list-reduce (function sequence start end initial-value ivp key)
39  (let ((what `(if ,key (funcall ,key (car sequence)) (car sequence))))
40    `(let ((sequence (nthcdr ,start ,sequence)))
41       (do ((count (if ,ivp ,start (1+ ,start)) (1+ count))
42            (sequence (if ,ivp sequence (cdr sequence))
43                      (cdr sequence))
44            (value (if ,ivp ,initial-value ,what)
45                   (funcall ,function value ,what)))
46           ((= count ,end) value)))))
47
48
49(defmacro list-reduce-from-end (function sequence start end
50                                         initial-value ivp key)
51  (let ((what `(if ,key (funcall ,key (car sequence)) (car sequence))))
52    `(let ((sequence (nthcdr (- (length ,sequence) ,end) (reverse ,sequence))))
53       (do ((count (if ,ivp ,start (1+ ,start)) (1+ count))
54            (sequence (if ,ivp sequence (cdr sequence))
55                      (cdr sequence))
56            (value (if ,ivp ,initial-value ,what)
57                   (funcall ,function ,what value)))
58           ((= count ,end) value)))))
59
60
61(defun reduce (function sequence &rest args &key from-end (start 0)
62                        end (initial-value nil ivp) key)
63  (unless end (setq end (length sequence)))
64  (if (= end start)
65      (if ivp initial-value (funcall function))
66      (sequence::seq-dispatch sequence
67          (if from-end
68              (list-reduce-from-end function sequence start end initial-value ivp key)
69              (list-reduce function sequence start end initial-value ivp key))
70          (let* ((disp (if from-end -1 1))
71                 (index (if from-end (1- end) start))
72                 (terminus (if from-end (1- start) end))
73                 (value (if ivp initial-value
74                            (let ((elt (aref sequence index)))
75                              (setf index (+ index disp))
76                              (if key (funcall key elt) elt))))
77                 (element nil))
78            (do* ()
79                 ((= index terminus) value)
80              (setf element (aref sequence index)
81                    index (+ index disp)
82                    element (if key (funcall key element) element)
83                    value (funcall function
84                                   (if from-end element value)
85                                   (if from-end value element)))))
86    (apply #'sequence:reduce function sequence args))))
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