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|
; MFC Utilities
; Copyright (C) 2008-2013 Centaur Technology
;
; Contact:
; Centaur Technology Formal Verification Group
; 7600-C N. Capital of Texas Highway, Suite 300, Austin, TX 78731, USA.
; http://www.centtech.com/
;
; License: (An MIT/X11-style license)
;
; Permission is hereby granted, free of charge, to any person obtaining a
; copy of this software and associated documentation files (the "Software"),
; to deal in the Software without restriction, including without limitation
; the rights to use, copy, modify, merge, publish, distribute, sublicense,
; and/or sell copies of the Software, and to permit persons to whom the
; Software is furnished to do so, subject to the following conditions:
;
; The above copyright notice and this permission notice shall be included in
; all copies or substantial portions of the Software.
;
; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
; FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
; DEALINGS IN THE SOFTWARE.
;
; mfc-utils.lisp -- some generally useful syntaxp/metafunction stuff
;
; Original author: Jared Davis <jared@centtech.com>
; Sol Swords <sswords@centtech.com>
; BOZO probably belongs in std/ks, but, surprise surprise, circular dependencies
; would arise, so we're putting it in lists.
(in-package "ACL2")
(program)
; REWRITING-POSITIVE-LITERAL
;
; Recall that an ACL2 goal like (IMPLIES (AND HYP1 ... HYPN) CONCL) is really
; represented as a clause, e.g.,
;
; (NOT HYP1) \/ (NOT HYP2) \/ ... \/ (NOT HYPN) \/ CONCL
;
; In this representation, ordinarily the hyps are "negative" literals and the
; conclusion is a "positive" literal. Of course, thanks to eliminating
; double-negatives, a hypothesis like (NOT (EQUAL X Y)) is also a positive
; literal.
;
; Sometimes we want a rewrite rule only to apply when we are rewriting a
; positive literal.
;
; A classic example is:
;
; - If the CONCL is (EQUAL X Y), and we know that X and Y are sets, then we
; might want to do something drastic like replace (EQUAL X Y) with (EQUAL
; (MEMBER A X) (MEMBER A Y)) for some new fresh variable A.
;
; - But if a HYP is (EQUAL X Y), we probably do not want to apply this same
; rewrite, because knowing that (MEMBER A X) = (MEMBER A Y) is a much weaker
; hypothesis than knowing (EQUAL X Y).
;
; Given a rewrite rule such as:
;
; (implies (and hyp1 ... hypN) (equiv (foo x y z) rhs))
;
; We can restrict the rule to only apply to positive literals by adding a new
; hyp like this:
;
; (rewriting-positive-literal `(foo ,x ,y ,z))
;
; This expands to a syntaxp hypothesis that looks at the MFC to decide if we
; are currently rewriting a positive literal of the specified form.
(defun mfc-rcnst (mfc state)
(declare (xargs :stobjs state)
(ignore state))
(access metafunction-context mfc :rcnst))
(defun mfc-current-literal (mfc state)
(declare (xargs :stobjs state))
(let ((rcnst (mfc-rcnst mfc state)))
(access rewrite-constant rcnst :current-literal)))
(defun rewriting-positive-literal-fn (term mfc state)
(declare (xargs :stobjs state))
(and (or (equal (mfc-current-literal mfc state)
(cons nil term)))
(or (null (mfc-ancestors mfc)))))
(defmacro rewriting-positive-literal (term)
`(syntaxp (rewriting-positive-literal-fn ,term mfc state)))
(defun rewriting-negative-literal-fn (term mfc state)
(declare (xargs :stobjs state))
(and (or (equal (mfc-current-literal mfc state)
(cons t term)))
(or (null (mfc-ancestors mfc)))))
(defmacro rewriting-negative-literal (term)
`(syntaxp (rewriting-negative-literal-fn ,term mfc state)))
(defun print-mfc (name mfc state)
(declare (xargs :stobjs state)
(ignore state))
(cw "~x0 mfc: ~X12~%" name
mfc
(evisc-tuple
nil nil
`((,(access metafunction-context mfc :wrld) . "<world>")
(,(access rewrite-constant
(access metafunction-context mfc :rcnst)
:current-enabled-structure) "<ens>")) nil)))
;; Arrgh, I'm not really sure how to craft theorems with must-fail/etc that
;; will ensure this is working properly, in case ACL2's MFC representation
;; changes.
;; (logic)
;; (encapsulate
;; (((hyp *) => *)
;; ((foo * * *) => *))
;; (local (defun hyp (x) (declare (ignore x)) nil))
;; (local (defun foo (x y z) (declare (ignore x y z)) t))
;; (defthmd constraint
;; (implies (hyp x) (foo x y z))))
;; (defthm rule1
;; (implies (and (rewriting-positive-literal `(foo ,x ,y ,z))
;; (hyp x))
;; (foo x y z))
;; :hints(("Goal" :in-theory (enable constraint))))
;; (defthm test1
;; (implies (and (posp z)
;; (consp y)
;; (hyp x)
;; (foo x y z))
;; x)
;; :rule-classes nil))
;; (defthm test1
;; (implies (hyp x)
;; (foo x y z))
;; :rule-classes nil))
;; (defthm test2
;; (implies (hyp x)
;; (not (foo x y z)))
;; :rule-classes nil))
|
