source: branches/streams/abcl/src/org/armedbear/lisp/copy-seq.lisp

;;; copy-seq.lisp
;;;
;;; Copyright (C) 2003 Peter Graves
;;; $Id: copy-seq.lisp 12516 2010-03-03 21:05:41Z astalla $
;;;
;;; 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
;;;
;;; As a special exception, the copyright holders of this library give you
;;; permission to link this library with independent modules to produce an
;;; executable, regardless of the license terms of these independent
;;; modules, and to copy and distribute the resulting executable under
;;; terms of your choice, provided that you also meet, for each linked
;;; independent module, the terms and conditions of the license of that
;;; module.  An independent module is a module which is not derived from
;;; or based on this library.  If you modify this library, you may extend
;;; this exception to your version of the library, but you are not
;;; obligated to do so.  If you do not wish to do so, delete this
;;; exception statement from your version.

(require "EXTENSIBLE-SEQUENCES-BASE")

(in-package "SYSTEM")

;; From CMUCL.

(defmacro vector-copy-seq (sequence type)
  `(let ((length (length ,sequence)))
     (do ((index 0 (1+ index))
    (copy (make-sequence-of-type ,type length)))
       ((= index length) copy)
       (aset copy index (aref ,sequence index)))))

(defmacro list-copy-seq (list)
  `(if (atom ,list) '()
       (let ((result (cons (car ,list) '()) ))
   (do ((x (cdr ,list) (cdr x))
        (splice result
          (cdr (rplacd splice (cons (car x) '() ))) ))
           ((atom x) (unless (null x)
                       (rplacd splice x))
            result)))))

(defun copy-seq (sequence)
  "Return a copy of SEQUENCE which is EQUAL to SEQUENCE but not EQ."
  (sequence::seq-dispatch sequence
    (list-copy-seq sequence)
    (vector-copy-seq sequence (type-of sequence))
    (sequence:copy-seq sequence)))