/usr/share/acl2-4.3/books/unicode/flatten.lisp is in acl2-books-source 4.3-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 | ;; 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 "app")
(include-book "consless-listp")
(defun binary-append-without-guard (x y)
(declare (xargs :guard t))
(mbe :logic
(append x y)
:exec
(if (consp x)
(cons (car x)
(binary-append-without-guard (cdr x) y))
y)))
(defmacro append-without-guard (x y &rest rst)
(xxxjoin 'binary-append-without-guard (list* x y rst)))
(add-macro-alias append-without-guard binary-append-without-guard)
(defund flatten (x)
(declare (xargs :guard t))
(if (consp x)
(mbe :logic (app (car x)
(flatten (cdr x)))
:exec (binary-append-without-guard (car x)
(flatten (cdr x))))
nil))
(defthm flatten-when-not-consp
(implies (not (consp x))
(equal (flatten x)
nil))
:hints(("Goal" :in-theory (enable flatten))))
(defthm flatten-of-cons
(equal (flatten (cons a x))
(app a (flatten x)))
:hints(("Goal" :in-theory (enable flatten))))
(defthm flatten-of-list-fix
(equal (flatten (list-fix x))
(flatten x))
:hints(("Goal" :induct (len x))))
(defthm flattenp-of-app
(equal (flatten (app x y))
(app (flatten x)
(flatten y)))
:hints(("Goal" :induct (len x))))
(defthm flatten-under-iff
(iff (flatten x)
(not (consless-listp x)))
:hints(("Goal" :induct (len x))))
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