source: branches/streams/abcl/src/org/armedbear/lisp/map.lisp

;;; map.lisp
;;;
;;; Copyright (C) 2005 Peter Graves
;;; $Id: map.lisp 11391 2008-11-15 22:38:34Z vvoutilainen $
;;;
;;; 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.

(in-package #:system)

(defun map (result-type function sequence &rest more-sequences)
  (let* ((sequences (cons sequence more-sequences))
         (limit (apply #'min (mapcar #'length sequences))))
    (declare (type index limit))
    (cond ((null result-type)
           (dotimes (i limit nil)
             (apply function (mapcar #'(lambda (z) (elt z i)) sequences))))
          ((eq result-type 'LIST)
           (let (result)
             (dotimes (i limit (nreverse result))
               (push (apply function (mapcar #'(lambda (z) (elt z i)) sequences))
                     result))))
          (t
           (let ((result (case result-type
                           (STRING
                            (make-string limit))
                           (VECTOR
                            (make-array limit))
                           (t
                            (make-sequence result-type limit)))))
             (dotimes (i limit result)
               (setf (elt result i)
                     (apply function (mapcar #'(lambda (z) (elt z i)) sequences)))))))))