/usr/share/acl2-6.3/books/misc/seqw.lisp is in acl2-books-source 6.3-5.
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; Copyright (C) 2008-2010 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/
;
; 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., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA.
;
; Original author: Jared Davis <jared@centtech.com>
(in-package "ACL2")
(include-book "seq")
; THE SEQW MACRO
;
; SEQW is an alternative implementation of the SEQ language which allows for
; warnings to be implicitly collected and stored in a list as your program
; executes. This comment only describes the differences between SEQW and SEQ,
; so if you have not yet examined seq.lisp and seq-examples.lsp, you will
; want to look at them first.
;
; The difference is quite straightforward:
;
; - Whereas a SEQ program has the form (seq <stream> ...), a SEQW program
; instead has one additional argument, (seqw <stream> <warnings> ...),
; where <warnings> is the name of a warnings structure.
;
; - Whereas every SEQ action returns (MV ERROR VAL STREAM), each SEQW action
; instead returns (MV ERROR VAL STREAM WARNINGS), where WARNINGS is the
; updated warnings structure.
;
; Similarly, every SEQW program returns (MV ERROR VAL STREAM WARNINGS) instead
; of (MV ERROR VAL STREAM).
;
; What is a warnings structure? When we use SEQW, we generally accumulate
; warnings into a list, so our actions just cons new warnings into this list
; when desired. But SEQW itself imposes no particular constraints on what
; a warnings structure is, and generally the way in which a warning is updated
; is determined by the actions of the program rather than by SEQW itself.
;
; For examples of using SEQW, see the file seqw-examples.lsp.
(program)
(defun seqw-process-bind (x stream warnings rest)
; X is a bind statement, stream is the name of the stream we are processing,
; and rest is the expansion of the rest of the lines in the block. We are to
; write the MV code for this bind statement.
(declare (xargs :guard (and (seq-bind-p x)
(seq-name-p stream)
(seq-name-p warnings))))
(cond ((eq (car x) :=)
(let ((action (second x)))
`(mv-let (!!!error !!!val ,stream ,warnings)
,action
(if !!!error
(mv !!!error !!!val ,stream ,warnings)
(check-vars-not-free (!!!error !!!val !!!stream)
,rest)))))
((or (eq (car x) :w=)
(eq (car x) :s=))
(let ((action (second x)))
`(let ((!!!stream ,stream))
(mv-let (!!!error !!!val ,stream ,warnings)
,action
(cond (!!!error
(mv !!!error !!!val ,stream ,warnings))
((not (mbt (,(case (car x) (:s= '<) (:w= '<=))
(acl2-count ,stream)
(acl2-count !!!stream))))
(prog2$ (er hard? "SEQW count failed for (~x0 ~x1.)~%"
',(car x) ',action)
(mv "SEQW count failure." nil !!!stream ,warnings)))
(t
(check-vars-not-free (!!!error !!!val !!!stream)
,rest)))))))
(t
(let* ((nametree (first x))
(type (second x))
(action (third x)))
(if (and nametree (symbolp nametree))
;; We have only a single variable. We can write some cleaner
;; mv-let code without any of this nametree destucturing.
(case type
(:= `(mv-let (!!!error ,nametree ,stream ,warnings)
,action
(if !!!error
(mv !!!error ,nametree ,stream ,warnings)
(check-vars-not-free (!!!error !!!val !!!stream)
,rest))))
((:w= :s=)
`(let ((!!!stream ,stream))
(mv-let (!!!error ,nametree ,stream ,warnings)
,action
(cond (!!!error
(mv !!!error ,nametree ,stream ,warnings))
((not (mbt (,(case type (:s= '<) (:w= '<=))
(acl2-count ,stream)
(acl2-count !!!stream))))
(prog2$ (er hard? "SEQW count failed for (~x0 ~x1 ~x2.)~%"
',nametree ',type ',action)
(mv "SEQW count failure." nil !!!stream ,warnings)))
(t
(check-vars-not-free (!!!error !!!val !!!stream)
,rest)))))))
;; Multiple variables; do the destructuring.
(case type
(:= `(mv-let (!!!error !!!val ,stream ,warnings)
,action
(if !!!error
(mv !!!error !!!val ,stream ,warnings)
(let ,(seq-nametree-to-let-bindings nametree '!!!val)
(check-vars-not-free (!!!error !!!val !!!stream)
,rest)))))
((:w= :s=)
`(let ((!!!stream ,stream))
(mv-let (!!!error !!!val ,stream ,warnings)
,action
(cond (!!!error
(mv !!!error !!!val ,stream ,warnings))
((not (mbt (,(case type (:s= '<) (:w= '<=))
(acl2-count ,stream)
(acl2-count !!!stream))))
(prog2$ (er hard? "SEQW count failed for (~x0 ~x1 ~x2.)~%"
',nametree ',type ',action)
(mv "SEQW count failure." nil !!!stream ,warnings)))
(t
(let ,(seq-nametree-to-let-bindings nametree '!!!val)
(check-vars-not-free (!!!error !!!val !!!stream)
,rest)))))))))))))
;(seqw-process-bind '(:= action) 'stream 'warnings '<rest>)
;(seqw-process-bind '(foo := action) 'stream 'warnings '<rest>)
;(seqw-process-bind '((foo . bar) := action) 'stream 'warnings '<rest>)
;(seqw-process-bind '((foo . nil) := action) 'stream 'warnings '<rest>)
(mutual-recursion
(defun seqw-process-unless (x stream warnings rest)
; Unless statements are easily transformed into when statements.
(declare (xargs :guard (and (seq-unless-p x)
(seq-name-p stream)
(seq-name-p warnings))))
(let ((condition (second x))
(subblock (cddr x)))
(seqw-process-when (list* 'when
`(not ,condition)
subblock)
stream warnings rest)))
(defun seqw-process-when (x stream warnings rest)
; X is a when statement, stream is the name of the stream we are processing,
; warnings is the name of the warnings structure, and rest is the expansion for
; the statements that come after this when statement in the current block. We
; are to write the MV code for this when statement.
(declare (xargs :guard (and (seq-when-p x)
(seq-name-p stream)
(seq-name-p warnings))))
(let* ((condition (second x))
(subblock (cddr x))
(ends-with-returnp (seq-list-ends-with-returnp subblock))
(bound-in-subblock (seq-block-names subblock nil)))
(cond
; Easy case 1. The subblock ends with a return, so we always either process it
; or rest but never both.
(ends-with-returnp
`(if ,condition
,(seqw-process-block subblock stream warnings nil)
,rest))
; Easy case 2. The subblock doesn't end with a return, so we may process it or
; and rest; but since it binds no variables so the only thing that it changes is
; the stream.
((not bound-in-subblock)
`(mv-let (!!!error !!!val ,stream ,warnings)
(if ,condition
,(seqw-process-block subblock stream warnings nil)
(mv nil nil ,stream ,warnings))
(if !!!error
(mv !!!error !!!val ,stream ,warnings)
(check-vars-not-free (!!!error !!!val) ,rest))))
; Hard case. The subblock does not end with a return. So if the condition is
; met, we're just going to do some additional bindings and stream manipulation
; before the processing rest. The hard part of this is dealing with all of the
; things that variables that might have been bound in the subblock.
; Our basic approach is to add a return statement to the end of the subblock
; before processing it, which returns to us a list of all the values for the
; variables it binds. We can then rebind these variables before giving them to
; rest.
(t
(let* ((return-stmt `(return (list ,@bound-in-subblock)))
(return-expansion `(mv nil (list ,@bound-in-subblock) ,stream ,warnings))
(new-subblock (append subblock (list return-stmt)))
(rebindings (seq-make-let-pairs-for-when bound-in-subblock)))
`(mv-let (!!!error !!!val ,stream ,warnings)
(if ,condition
,(seqw-process-block new-subblock stream warnings nil)
,return-expansion)
(if !!!error
(mv !!!error !!!val ,stream ,warnings)
; At this point, !!!val holds the list of all the values for the variables
; which were bound in the subblock. We just need to redo these bindings so
; that they are available in rest.
(let* ,rebindings
(check-vars-not-free (!!!error !!!val) ,rest)))))))))
(defun seqw-process-stmt (x stream warnings rest)
(declare (xargs :guard (and (or (seq-bind-p x)
(seq-when-p x)
(seq-unless-p x)
(seq-return-p x))
(seq-name-p stream)
(seq-name-p warnings))))
(cond ((seq-bind-p x)
(seqw-process-bind x stream warnings rest))
((seq-when-p x)
(seqw-process-when x stream warnings rest))
((seq-unless-p x)
(seqw-process-unless x stream warnings rest))
(t
(let ((type (first x))
(value (second x)))
(cond ((eq type 'return)
`(mv nil ,value ,stream ,warnings))
((eq type 'return-raw)
value))))))
(defun seqw-process-block (x stream warnings toplevelp)
(declare (xargs :guard (and (seq-block-p x toplevelp)
(seq-name-p stream)
(seq-name-p warnings))))
(if (atom (cdr x))
(seqw-process-stmt (car x) stream warnings `(mv nil nil ,stream ,warnings))
(let ((rest (seqw-process-block (cdr x) stream warnings toplevelp)))
(seqw-process-stmt (car x) stream warnings rest)))))
(defun seqw-fn (stream warnings block)
(declare (xargs :guard (and (seq-name-p stream)
(seq-name-p warnings)
(seq-block-p block t))))
(let* ((names (seq-block-names block t))
(initial-bindings (seq-make-initial-let-pairs (remove-duplicates names))))
`(let ,initial-bindings
(declare (ignorable ,@names))
,(seqw-process-block block stream warnings t))))
(defmacro seqw (stream warnings &rest block)
(seqw-fn stream warnings block))
(defun seqw-backtrack-fn (stream warnings blocks)
(declare (xargs :guard (and (seq-name-p stream)
(seq-name-p warnings)
(seq-block-list-p blocks t)
(consp blocks))))
(if (atom (cdr blocks))
`(seqw ,stream ,warnings . ,(car blocks))
`(mv-let (!!!error !!!val updated-stream updated-warnings)
(seqw ,stream ,warnings . ,(car blocks))
(if (not !!!error)
(mv !!!error !!!val updated-stream updated-warnings)
(check-vars-not-free (!!!error !!!val)
,(seqw-backtrack-fn stream warnings (cdr blocks)))))))
(defmacro seqw-backtrack (stream warnings &rest blocks)
(seqw-backtrack-fn stream warnings blocks))
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