File: repeat.lisp

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;; Processing Unicode Files with ACL2
;; Copyright (C) 2005-2006 by Jared Davis <jared@cs.utexas.edu>
;;
;; 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.

(in-package "ACL2")
(include-book "take")

(defund repeat (x n)
  (declare (xargs :guard (natp n)))
  (if (zp n)
      nil
    (cons x (repeat x (1- n)))))

(defthm simpler-take-when-not-consp
  (implies (not (consp x))
           (equal (simpler-take n x)
                  (repeat nil n)))
  :hints(("Goal" :in-theory (enable repeat))))