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837 lines
45 KiB
Common Lisp
837 lines
45 KiB
Common Lisp
;;; The contents of this file are subject to the Mozilla Public
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;;; License Version 1.1 (the "License"); you may not use this file
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;;; except in compliance with the License. You may obtain a copy of
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;;; the License at http://www.mozilla.org/MPL/
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;;;
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;;; Software distributed under the License is distributed on an "AS
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;;; IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
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;;; implied. See the License for the specific language governing
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;;; rights and limitations under the License.
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;;;
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;;; The Original Code is the Language Design and Prototyping Environment.
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;;;
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;;; The Initial Developer of the Original Code is Netscape Communications
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;;; Corporation. Portions created by Netscape Communications Corporation are
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;;; Copyright (C) 1999 Netscape Communications Corporation. All
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;;; Rights Reserved.
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;;;
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;;; Contributor(s): Waldemar Horwat <waldemar@acm.org>
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;;;
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;;; LALR(1) and LR(1) grammar generator
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;;;
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;;; Waldemar Horwat (waldemar@acm.org)
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;;;
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;;; ------------------------------------------------------------------------------------------------------
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; kernel-item-alist is a list of pairs (item . prev), where item is a kernel item
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; and prev is either nil or a laitem. kernel is a list of the kernel items in a canonical order.
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; Return a new state with the given list of kernel items and state number.
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; If mode is :lalr-1, for each non-null prev in kernel-item-alist, update
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; (laitem-propagates prev) to include the corresponding laitem in the new state. Do this anyway
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; for internal lookaheads, regardless of mode.
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;
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; If mode is :canonical-lr-1, kernel-item-alist is a list of pairs (item . lookaheads), where
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; lookaheads is a terminalset of lookaheads for that item. Use these lookaheads instead of
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; initial-lookaheads.
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(defun make-state (grammar kernel kernel-item-alist mode number initial-lookaheads)
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(let ((laitems nil)
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(laitems-hash (make-hash-table :test #'eq))
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(laitems-maybe-forbidden nil)) ;Association list of: laitem -> terminalset of potentially forbidden terminals; missing means *empty-terminalset*
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(labels
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;Create a laitem for this item and add the association item->laitem to the laitems-hash
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;hash table if it's not there already. Regardless of whether a new laitem was created,
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;update the laitem's lookaheads to also include the given lookaheads.
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;forbidden is a terminalset of terminals that must not occur immediately after the dot in this
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;laitem. The forbidden set is inherited from constraints in parent laitems in the same state.
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;maybe-forbidden is an upper bounds on the forbidden lookaheads in this laitem.
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;If prev is non-null, update (laitem-propagates prev) to include the laitem and the given
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;passthrough terminalset if it's not already included there.
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;If a new laitem was created and its first symbol after the dot exists and is a
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;nonterminal A, recursively close items A->.rhs corresponding to all rhs's in the
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;grammar's rule for A.
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((close-item (item forbidden maybe-forbidden lookaheads prev passthroughs)
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(let ((production (item-production item))
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(dot (item-dot item))
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(laitem (gethash item laitems-hash)))
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(let ((extra-forbidden (terminalset-complement (general-production-constraint production dot))))
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(terminalset-union-f forbidden extra-forbidden)
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(terminalset-union-f maybe-forbidden extra-forbidden))
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(unless (terminalset-empty? forbidden)
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(multiple-value-bind (dot-lookaheads dot-passthroughs)
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(string-initial-terminals grammar (item-unseen item) (production-constraints production) (item-dot item) t)
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(let ((dot-initial (terminalset-union dot-lookaheads dot-passthroughs)))
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;Check whether any terminal can start this item. If not, skip this item altogether.
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(when (terminalset-empty? (terminalset-difference dot-initial forbidden))
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;Mark skipped items in the laitems-hash table.
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(when (and laitem (not (eq laitem 'forbidden)))
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(error "Two laitems in the same state differing only in forbidden initial terminal constraints: ~S" laitem))
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(setf (gethash item laitems-hash) 'forbidden)
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(return-from close-item))
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;Convert forbidden into a canonical format by removing terminals that cannot begin this item's expansion anyway.
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(terminalset-intersection-f forbidden dot-initial))))
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(if laitem
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(let ((laitem-maybe-forbidden-entry (assoc laitem laitems-maybe-forbidden))
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(new-forbidden (terminalset-union forbidden (laitem-forbidden laitem))))
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(when laitem-maybe-forbidden-entry
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(terminalset-intersection-f (cdr laitem-maybe-forbidden-entry) maybe-forbidden))
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(unless (terminalset-<= new-forbidden (or (cdr laitem-maybe-forbidden-entry) *empty-terminalset*))
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(error "Two laitems in the same state differing only in forbidden initial terminal constraints: ~S ~%old forbidden: ~S ~%new forbidden: ~S~%maybe forbidden: ~S"
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laitem
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(terminalset-list grammar (laitem-forbidden laitem))
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(terminalset-list grammar forbidden)
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(and laitem-maybe-forbidden-entry (terminalset-list grammar (cdr laitem-maybe-forbidden-entry)))))
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(setf (laitem-forbidden laitem) new-forbidden)
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(terminalset-union-f (laitem-lookaheads laitem) lookaheads))
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(let ((item-next-symbol (item-next-symbol item)))
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(setq laitem (allocate-laitem grammar item forbidden lookaheads))
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(push laitem laitems)
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(setf (gethash item laitems-hash) laitem)
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(unless (terminalset-empty? maybe-forbidden)
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(push (cons laitem maybe-forbidden) laitems-maybe-forbidden))
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(when (nonterminal? item-next-symbol)
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(multiple-value-bind (next-lookaheads next-passthroughs)
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(string-initial-terminals grammar (rest (item-unseen item)) (production-constraints production) (1+ dot) nil)
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(let ((next-prev (and (not (terminalset-empty? next-passthroughs)) laitem)))
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(dolist (production (rule-productions (grammar-rule grammar item-next-symbol)))
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(close-item (make-item grammar production 0) forbidden maybe-forbidden next-lookaheads next-prev next-passthroughs)))))))
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(when prev
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(laitem-add-propagation prev laitem passthroughs)))))
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(dolist (acons kernel-item-alist)
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(close-item (car acons)
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*empty-terminalset*
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*empty-terminalset*
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(if (eq mode :canonical-lr-1) (cdr acons) initial-lookaheads)
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(and (eq mode :lalr-1) (cdr acons))
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*full-terminalset*))
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(allocate-state number kernel (nreverse laitems)))))
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; f is a function that takes three arguments:
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; a grammar symbol;
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; a list of kernel items in order of increasing item number [list of (item . lookahead) when mode is :canonical-lr-1];
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; a list of pairs (item . prev), where item is a kernel item and prev is a laitem.
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; For each possible symbol X that can be shifted while in the given state S, call
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; f giving it S and the list of items that constitute the kernel of that shift's destination
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; state. The prev's are the sources of the corresponding shifted items.
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(defun state-each-shift-item-alist (f state mode)
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(let ((shift-symbols-hash (make-hash-table :test *grammar-symbol-=*)))
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(dolist (source-laitem (state-laitems state))
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(let* ((source-item (laitem-item source-laitem))
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(shift-symbol (item-next-symbol source-item)))
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(when shift-symbol
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(push (cons (item-next source-item) source-laitem)
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(gethash shift-symbol shift-symbols-hash)))))
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;Use dolist/gethash instead of maphash to make state assignments deterministic.
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(dolist (shift-symbol (sorted-hash-table-keys shift-symbols-hash))
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(let* ((kernel-item-alist (gethash shift-symbol shift-symbols-hash))
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(kernel (if (eq mode :canonical-lr-1)
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(sort (mapcar #'(lambda (acons)
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(cons (car acons) (laitem-lookaheads (cdr acons))))
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kernel-item-alist)
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#'<
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:key #'(lambda (acons) (item-number (car acons))))
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(sort (mapcar #'car kernel-item-alist) #'< :key #'item-number))))
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(funcall f shift-symbol kernel kernel-item-alist)))))
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; f is a function that takes a terminal variant as an argument.
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; For each variant of the given terminal (which, along with kernel-item-alist, was obtained from
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; state-each-shift-item-alist's callback), determine whether that variant can actually occur at the
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; current position or whether it is forbidden by constraints. If it can occur, call f with that variant.
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; Signal an error if some laitems in kernel-item-alist indicate that a variant can occur while others
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; indicate that the same variant cannot occur. Also signal an internal error if no variant can occur, as
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; make-state should have filtered such shift items out.
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(defun each-shift-symbol-variant (f grammar terminal kernel-item-alist)
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(let ((n-applicable-variants 0))
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(dolist (variant (terminal-variants grammar terminal))
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(let ((allowed nil)
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(forbidden nil))
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(dolist (acons kernel-item-alist)
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(if (terminal-in-terminalset grammar variant (laitem-forbidden (cdr acons)))
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(setq forbidden t)
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(setq allowed t)))
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(when (eq allowed forbidden)
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(error "Symbol ~S ~A" variant
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(if allowed "both allowed and forbidden" "neither allowed nor forbidden")))
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(unless forbidden
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(incf n-applicable-variants)
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(funcall f variant))))
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(when (zerop n-applicable-variants)
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(error "Internal parser error"))))
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;;; ------------------------------------------------------------------------------------------------------
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;;; CANONICAL LR(1)
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;;;
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;;; Canonical LR(1) is accepts the same set of languages as LR(1) except that it produces vastly larger,
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;;; unoptimizied state tables. The only advantage to using Canonical LR(1) instead of LR(1) is that
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;;; a Canonical LR(1) parser will not make any reductions from an error state, whereas a LR(1) or LALR(1)
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;;; parser might make reductions (but not shifts). In other words, a Canonical LR(1) parser's shift and
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;;; reduce tables are fully accurate rather than conservative approximations based on merged states.
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; Make all states in the grammar and return the initial state.
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; Initialize the grammar's list of states.
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; Initialize the states' gotos lists.
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; Initialize the states' shift (but not reduce or accept) transitions in the transitions lists.
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(defun add-all-canonical-lr-states (grammar)
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(let* ((initial-item (make-item grammar (grammar-start-production grammar) 0))
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(lr-states-hash (make-hash-table :test #'equal)) ;canonical kernel -> state
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(initial-kernel (list (cons initial-item (make-terminalset grammar *end-marker*))))
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(initial-state (make-state grammar initial-kernel initial-kernel :canonical-lr-1 0 nil))
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(states (list initial-state))
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(next-state-number 1))
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(setf (gethash initial-kernel lr-states-hash) initial-state)
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(do ((source-states (list initial-state)))
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((endp source-states))
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(let ((source-state (pop source-states)))
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;Propagate the source state's internal lookaheads and then erase the propagates chains.
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(propagate-internal-lookaheads source-state)
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(dolist (laitem (state-laitems source-state))
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(setf (laitem-propagates laitem) nil))
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(state-each-shift-item-alist
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#'(lambda (shift-symbol kernel kernel-item-alist)
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(let ((destination-state (gethash kernel lr-states-hash)))
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(unless destination-state
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(setq destination-state (make-state grammar kernel kernel :canonical-lr-1 next-state-number nil))
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(setf (gethash kernel lr-states-hash) destination-state)
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(incf next-state-number)
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(push destination-state states)
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(push destination-state source-states))
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(if (nonterminal? shift-symbol)
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(push (cons shift-symbol destination-state)
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(state-gotos source-state))
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(each-shift-symbol-variant
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#'(lambda (shift-symbol-variant)
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(push (cons shift-symbol-variant (make-shift-transition destination-state))
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(state-transitions source-state)))
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grammar shift-symbol kernel-item-alist))))
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source-state :canonical-lr-1)))
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(setf (grammar-states grammar) (nreverse states))
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initial-state))
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;;; ------------------------------------------------------------------------------------------------------
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;;; LR(1)
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; kernel-item-alist should have the same kernel items as state.
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; Return true if the prev lookaheads in kernel-item-alist are the same as or subsets of
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; the corresponding lookaheads in the state's kernel laitems.
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(defun state-subsumes-lookaheads (state kernel-item-alist)
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(every
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#'(lambda (acons)
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(terminalset-<= (laitem-lookaheads (cdr acons))
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(laitem-lookaheads (state-laitem state (car acons)))))
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kernel-item-alist))
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; kernel-item-alist should have the same kernel items as state.
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; Return true if the prev lookaheads in kernel-item-alist are weakly compatible
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; with the lookaheads in the state's kernel laitems.
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(defun state-weakly-compatible (state kernel-item-alist)
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(labels
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((lookahead-weakly-compatible (lookahead1a lookahead1b lookahead2a lookahead2b)
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(or (and (terminalsets-disjoint lookahead1a lookahead2b)
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(terminalsets-disjoint lookahead1b lookahead2a))
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(not (terminalsets-disjoint lookahead1a lookahead1b))
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(not (terminalsets-disjoint lookahead2a lookahead2b))))
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(lookahead-list-weakly-compatible (lookahead1a lookaheads1 lookahead2a lookaheads2)
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(or (endp lookaheads1)
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(and (lookahead-weakly-compatible lookahead1a (first lookaheads1) lookahead2a (first lookaheads2))
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(lookahead-list-weakly-compatible lookahead1a (rest lookaheads1) lookahead2a (rest lookaheads2)))))
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(lookahead-lists-weakly-compatible (lookaheads1 lookaheads2)
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(or (endp lookaheads1)
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(and (lookahead-list-weakly-compatible (first lookaheads1) (rest lookaheads1) (first lookaheads2) (rest lookaheads2))
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(lookahead-lists-weakly-compatible (rest lookaheads1) (rest lookaheads2))))))
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(or (= (length kernel-item-alist) 1)
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(lookahead-lists-weakly-compatible
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(mapcar #'(lambda (acons) (laitem-lookaheads (state-laitem state (car acons)))) kernel-item-alist)
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(mapcar #'(lambda (acons) (laitem-lookaheads (cdr acons))) kernel-item-alist)))))
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; Propagate all lookaheads in the state.
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(defun propagate-internal-lookaheads (state)
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(do ((changed t))
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((not changed))
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(setq changed nil)
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(dolist (src-laitem (state-laitems state))
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(let ((src-lookaheads (laitem-lookaheads src-laitem)))
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(dolist (propagation (laitem-propagates src-laitem))
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(let* ((dst-laitem (car propagation))
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(mask (cdr propagation))
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(old-dst-lookaheads (laitem-lookaheads dst-laitem))
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(new-dst-lookaheads (terminalset-union old-dst-lookaheads (terminalset-intersection src-lookaheads mask))))
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(setf (laitem-lookaheads dst-laitem) new-dst-lookaheads)
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(unless (terminalset-= old-dst-lookaheads new-dst-lookaheads)
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(setq changed t))))))))
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; Propagate all lookaheads in kernel-item-alist, which must target destination-state.
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; Mark destination-state as dirty in the dirty-states hash table.
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(defun propagate-external-lookaheads (kernel-item-alist destination-state dirty-states)
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(dolist (acons kernel-item-alist)
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(let ((dest-laitem (state-laitem destination-state (car acons)))
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(src-laitem (cdr acons)))
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(terminalset-union-f (laitem-lookaheads dest-laitem) (laitem-lookaheads src-laitem))))
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(setf (gethash destination-state dirty-states) t))
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; Make all states in the grammar and return the initial state.
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; Initialize the grammar's list of states.
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; Initialize the states' gotos lists.
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; Initialize the states' shift (but not reduce or accept) transitions in the transitions lists.
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(defun add-all-lr-states (grammar)
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(let* ((initial-item (make-item grammar (grammar-start-production grammar) 0))
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(lr-states-hash (make-hash-table :test #'equal)) ;kernel -> list of states with that kernel
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(initial-kernel (list initial-item))
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(initial-state (make-state grammar initial-kernel (list (cons initial-item nil)) :lr-1 0 (make-terminalset grammar *end-marker*)))
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(states (list initial-state))
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(next-state-number 1))
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(setf (gethash initial-kernel lr-states-hash) (list initial-state))
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(do ((source-states (list initial-state))
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(dirty-states (make-hash-table :test #'eq))) ;Set of states whose kernel lookaheads changed and haven't been propagated yet
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((and (endp source-states) (zerop (hash-table-count dirty-states))))
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(labels
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((make-destination-state (kernel kernel-item-alist)
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(let* ((possible-destination-states (gethash kernel lr-states-hash))
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(destination-state (find-if #'(lambda (possible-destination-state)
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(state-subsumes-lookaheads possible-destination-state kernel-item-alist))
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possible-destination-states)))
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(cond
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(destination-state)
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((setq destination-state (find-if #'(lambda (possible-destination-state)
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(state-weakly-compatible possible-destination-state kernel-item-alist))
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possible-destination-states))
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(propagate-external-lookaheads kernel-item-alist destination-state dirty-states))
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(t
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(setq destination-state (make-state grammar kernel kernel-item-alist :lr-1 next-state-number *empty-terminalset*))
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(propagate-external-lookaheads kernel-item-alist destination-state dirty-states)
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(push destination-state (gethash kernel lr-states-hash))
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(incf next-state-number)
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(push destination-state states)
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(push destination-state source-states)))
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destination-state))
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(update-destination-state (destination-state kernel-item-alist)
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(cond
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((state-subsumes-lookaheads destination-state kernel-item-alist)
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destination-state)
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((state-weakly-compatible destination-state kernel-item-alist)
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(propagate-external-lookaheads kernel-item-alist destination-state dirty-states)
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destination-state)
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(t (make-destination-state (state-kernel destination-state) kernel-item-alist)))))
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(if source-states
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(let ((source-state (pop source-states)))
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(remhash source-state dirty-states)
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(propagate-internal-lookaheads source-state)
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(state-each-shift-item-alist
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#'(lambda (shift-symbol kernel kernel-item-alist)
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(let ((destination-state (make-destination-state kernel kernel-item-alist)))
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(if (nonterminal? shift-symbol)
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(push (cons shift-symbol destination-state)
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(state-gotos source-state))
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(each-shift-symbol-variant
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#'(lambda (shift-symbol-variant)
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(push (cons shift-symbol-variant (make-shift-transition destination-state))
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(state-transitions source-state)))
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grammar shift-symbol kernel-item-alist))))
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source-state :lr-1))
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(dolist (dirty-state (sort (hash-table-keys dirty-states) #'< :key #'state-number))
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(when (remhash dirty-state dirty-states)
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(propagate-internal-lookaheads dirty-state)
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(state-each-shift-item-alist
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#'(lambda (shift-symbol kernel kernel-item-alist)
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(declare (ignore kernel))
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(if (nonterminal? shift-symbol)
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(let* ((destination-binding (assoc shift-symbol (state-gotos dirty-state) :test *grammar-symbol-=*))
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(destination-state (assert-non-null (cdr destination-binding))))
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(setf (cdr destination-binding) (update-destination-state destination-state kernel-item-alist)))
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(each-shift-symbol-variant
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#'(lambda (shift-symbol-variant)
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(let* ((destination-transition (state-transition dirty-state shift-symbol-variant))
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(destination-state (assert-non-null (transition-state destination-transition))))
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(setf (transition-state destination-transition)
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(update-destination-state destination-state kernel-item-alist))))
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grammar shift-symbol kernel-item-alist)))
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dirty-state :lr-1))))))
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(setf (grammar-states grammar) (nreverse states))
|
|
initial-state))
|
|
|
|
|
|
;;; ------------------------------------------------------------------------------------------------------
|
|
;;; LALR(1)
|
|
|
|
|
|
; Make all states in the grammar and return the initial state.
|
|
; Initialize the grammar's list of states.
|
|
; Set up the laitems' propagate lists but do not propagate lookaheads yet.
|
|
; Initialize the states' gotos lists.
|
|
; Initialize the states' shift (but not reduce or accept) transitions in the transitions lists.
|
|
(defun add-all-lalr-states (grammar)
|
|
(let* ((initial-item (make-item grammar (grammar-start-production grammar) 0))
|
|
(lalr-states-hash (make-hash-table :test #'equal)) ;kernel -> state
|
|
(initial-kernel (list initial-item))
|
|
(initial-state (make-state grammar initial-kernel (list (cons initial-item nil)) :lalr-1 0 (make-terminalset grammar *end-marker*)))
|
|
(states (list initial-state))
|
|
(next-state-number 1))
|
|
(setf (gethash initial-kernel lalr-states-hash) initial-state)
|
|
(do ((source-states (list initial-state)))
|
|
((endp source-states))
|
|
(let ((source-state (pop source-states)))
|
|
(state-each-shift-item-alist
|
|
#'(lambda (shift-symbol kernel kernel-item-alist)
|
|
(let ((destination-state (gethash kernel lalr-states-hash)))
|
|
(if destination-state
|
|
(dolist (acons kernel-item-alist)
|
|
(laitem-add-propagation (cdr acons) (state-laitem destination-state (car acons)) *full-terminalset*))
|
|
(progn
|
|
(setq destination-state (make-state grammar kernel kernel-item-alist :lalr-1 next-state-number *empty-terminalset*))
|
|
(setf (gethash kernel lalr-states-hash) destination-state)
|
|
(incf next-state-number)
|
|
(push destination-state states)
|
|
(push destination-state source-states)))
|
|
(if (nonterminal? shift-symbol)
|
|
(push (cons shift-symbol destination-state)
|
|
(state-gotos source-state))
|
|
(each-shift-symbol-variant
|
|
#'(lambda (shift-symbol-variant)
|
|
(push (cons shift-symbol-variant (make-shift-transition destination-state))
|
|
(state-transitions source-state)))
|
|
grammar shift-symbol kernel-item-alist))))
|
|
source-state :lalr-1)))
|
|
(setf (grammar-states grammar) (nreverse states))
|
|
initial-state))
|
|
|
|
|
|
; Propagate the lookaheads in the LALR(1) grammar.
|
|
(defun propagate-lalr-lookaheads (grammar)
|
|
(let ((dirty-laitems (make-hash-table :test #'eq)))
|
|
(dolist (state (grammar-states grammar))
|
|
(dolist (laitem (state-laitems state))
|
|
(when (and (laitem-propagates laitem) (not (terminalset-empty? (laitem-lookaheads laitem))))
|
|
(setf (gethash laitem dirty-laitems) t))))
|
|
(do ()
|
|
((zerop (hash-table-count dirty-laitems)))
|
|
(dolist (dirty-laitem (hash-table-keys dirty-laitems))
|
|
(remhash dirty-laitem dirty-laitems)
|
|
(let ((src-lookaheads (laitem-lookaheads dirty-laitem)))
|
|
(dolist (propagation (laitem-propagates dirty-laitem))
|
|
(let ((dst-laitem (car propagation))
|
|
(mask (cdr propagation)))
|
|
(let* ((old-dst-lookaheads (laitem-lookaheads dst-laitem))
|
|
(new-dst-lookaheads (terminalset-union old-dst-lookaheads (terminalset-intersection src-lookaheads mask))))
|
|
(unless (terminalset-= old-dst-lookaheads new-dst-lookaheads)
|
|
(setf (laitem-lookaheads dst-laitem) new-dst-lookaheads)
|
|
(setf (gethash dst-laitem dirty-laitems) t))))))))
|
|
|
|
;Erase the propagates chains in all laitems.
|
|
(dolist (state (grammar-states grammar))
|
|
(dolist (laitem (state-laitems state))
|
|
(setf (laitem-propagates laitem) nil)))))
|
|
|
|
|
|
;;; ------------------------------------------------------------------------------------------------------
|
|
|
|
|
|
; Calculate the reduce and accept transitions in the grammar.
|
|
; Also sort all transitions by their terminal numbers and gotos by their nonterminal numbers.
|
|
; Conflicting transitions are sorted as follows:
|
|
; shifts come before reduces and accepts
|
|
; accepts come before reduces
|
|
; reduces with lower production numbers come before reduces with higher production numbers
|
|
; Disambiguation will choose the first member of a sorted list of conflicting transitions.
|
|
(defun finish-transitions (grammar)
|
|
(dolist (state (grammar-states grammar))
|
|
(dolist (laitem (state-laitems state))
|
|
(let ((item (laitem-item laitem)))
|
|
(unless (item-next-symbol item)
|
|
(let ((lookaheads (terminalset-difference
|
|
(terminalset-intersection
|
|
(laitem-lookaheads laitem)
|
|
(general-production-constraint (item-production item) (item-dot item)))
|
|
(laitem-forbidden laitem))))
|
|
(if (grammar-symbol-= (item-lhs item) *start-nonterminal*)
|
|
(when (terminal-in-terminalset grammar *end-marker* lookaheads)
|
|
(push (cons *end-marker* (make-accept-transition))
|
|
(state-transitions state)))
|
|
(map-terminalset-reverse
|
|
#'(lambda (lookahead)
|
|
(push (cons lookahead (make-reduce-transition (item-production item)))
|
|
(state-transitions state)))
|
|
grammar
|
|
lookaheads))))))
|
|
(setf (state-gotos state)
|
|
(sort (state-gotos state) #'< :key #'(lambda (goto-cons) (state-number (cdr goto-cons)))))
|
|
(setf (state-transitions state)
|
|
(sort (state-transitions state)
|
|
#'(lambda (transition-cons-1 transition-cons-2)
|
|
(let ((terminal-number-1 (terminal-number grammar (car transition-cons-1)))
|
|
(terminal-number-2 (terminal-number grammar (car transition-cons-2))))
|
|
(cond
|
|
((< terminal-number-1 terminal-number-2) t)
|
|
((> terminal-number-1 terminal-number-2) nil)
|
|
(t (let* ((transition1 (cdr transition-cons-1))
|
|
(transition2 (cdr transition-cons-2))
|
|
(transition-kind-1 (transition-kind transition1))
|
|
(transition-kind-2 (transition-kind transition2)))
|
|
(cond
|
|
((eq transition-kind-2 :shift) nil)
|
|
((eq transition-kind-1 :shift) t)
|
|
((eq transition-kind-2 :accept) nil)
|
|
((eq transition-kind-1 :accept) t)
|
|
(t (let ((production-number-1 (production-number (transition-production transition1)))
|
|
(production-number-2 (production-number (transition-production transition2))))
|
|
(< production-number-1 production-number-2)))))))))))))
|
|
|
|
|
|
; Find ambiguities, if any, in the grammar. Report them on the given stream.
|
|
; Fix all ambiguities in favor of the first transition listed
|
|
; (the transitions were ordered by finish-transitions).
|
|
; Return true if ambiguities were found.
|
|
(defun report-and-fix-ambiguities (grammar stream)
|
|
(let ((found-ambiguities nil))
|
|
(dolist (state (grammar-states grammar))
|
|
(labels
|
|
|
|
((report-ambiguity (transition-cons other-transition-conses)
|
|
(unless found-ambiguities
|
|
(setq found-ambiguities t)
|
|
(format stream "~&Ambiguities:"))
|
|
(write-char #\newline stream)
|
|
(pprint-logical-block (stream nil)
|
|
(format stream "S~D: ~W => " (state-number state) (car transition-cons))
|
|
(pprint-logical-block (stream nil)
|
|
(dolist (a (cons transition-cons other-transition-conses))
|
|
(print-transition (cdr a) stream)
|
|
(format stream " ~:_")))))
|
|
|
|
; Check the list of transition-conses and report ambiguities.
|
|
; start is the start of a possibly larger list of transition-conses whose tail
|
|
; is the given list. If ambiguities exist, return a copy of start up to the
|
|
; position of list in it followed by list with ambiguities removed. If not,
|
|
; return start unchanged.
|
|
(check (transition-conses start)
|
|
(if transition-conses
|
|
(let* ((transition-cons (first transition-conses))
|
|
(transition-terminal (car transition-cons))
|
|
(transition-conses-rest (rest transition-conses)))
|
|
(if transition-conses-rest
|
|
(if (grammar-symbol-= transition-terminal (car (first transition-conses-rest)))
|
|
(let ((unrelated-transitions
|
|
(member-if #'(lambda (a) (not (grammar-symbol-= transition-terminal (car a))))
|
|
transition-conses-rest)))
|
|
(report-ambiguity transition-cons (ldiff transition-conses-rest unrelated-transitions))
|
|
(check unrelated-transitions (append (ldiff start transition-conses-rest) unrelated-transitions)))
|
|
(check transition-conses-rest start))
|
|
start))
|
|
start)))
|
|
|
|
(let ((transition-conses (state-transitions state)))
|
|
(setf (state-transitions state) (check transition-conses transition-conses)))))
|
|
(when found-ambiguities
|
|
(write-char #\newline stream))
|
|
found-ambiguities))
|
|
|
|
|
|
; Remove the temporary item and laitem lists from the grammar's states. This reduces the grammar's lisp
|
|
; heap usage but prevents it from being printed.
|
|
(defun clean-grammar (grammar)
|
|
(when (grammar-items-hash grammar)
|
|
(setf (grammar-items-hash grammar) nil)
|
|
(dolist (state (grammar-states grammar))
|
|
(setf (state-kernel state) nil)
|
|
(setf (state-laitems state) nil))))
|
|
|
|
|
|
; Erase the existing parser, if any, for the given grammar.
|
|
(defun clear-parser (grammar)
|
|
(setf (grammar-items-hash grammar) nil)
|
|
(setf (grammar-states grammar) nil))
|
|
|
|
|
|
; Construct a LR or LALR parser in the given grammar. kind should be :lalr-1, :lr-1, or :canonical-lr-1.
|
|
; Return true if ambiguities were found.
|
|
(defun compile-parser (grammar kind)
|
|
(clear-parser grammar)
|
|
(setf (grammar-items-hash grammar) (make-hash-table :test #'equal))
|
|
(ecase kind
|
|
(:lalr-1
|
|
(add-all-lalr-states grammar)
|
|
(propagate-lalr-lookaheads grammar))
|
|
(:lr-1
|
|
(add-all-lr-states grammar))
|
|
(:canonical-lr-1
|
|
(add-all-canonical-lr-states grammar)))
|
|
(finish-transitions grammar)
|
|
(report-and-fix-ambiguities grammar *error-output*))
|
|
|
|
|
|
|
|
; (cons (list <kind> <start-symbol> <grammar-source> <grammar-options>) <grammar>)
|
|
(defvar *make-and-compile-grammar-cache* (cons nil nil))
|
|
|
|
; Make the grammar and compile its parser. kind should be :lalr-1, :lr-1, or :canonical-lr-1.
|
|
(defun make-and-compile-grammar (kind parametrization start-symbol grammar-source &rest grammar-options)
|
|
(let ((key (list kind start-symbol grammar-source grammar-options))
|
|
(cached-grammar (cdr *make-and-compile-grammar-cache*)))
|
|
(if (and (equal key (car *make-and-compile-grammar-cache*))
|
|
(grammar-parametrization-= parametrization cached-grammar))
|
|
(progn
|
|
(format *trace-output* "Re-using grammar ~S ~S ~S~%" kind start-symbol grammar-options)
|
|
cached-grammar)
|
|
(let* ((grammar (apply #'make-grammar parametrization start-symbol grammar-source grammar-options))
|
|
(found-ambiguities (compile-parser grammar kind)))
|
|
(setq *make-and-compile-grammar-cache*
|
|
(if found-ambiguities
|
|
(cons nil nil)
|
|
(cons key grammar)))
|
|
grammar))))
|
|
|
|
|
|
; Collapse states that have at most one possible reduction into forwarding states.
|
|
; DON'T DO THIS ON GRAMMARS THAT HAVE CONSTRAINTS AT THE TAIL END OF A PRODUCTION.
|
|
; Return the number of states optimized.
|
|
(defun forward-parser-states (grammar)
|
|
(let ((n-forwarded-states 0))
|
|
(dolist (state (grammar-states grammar))
|
|
(let ((production (forwarding-state-production state)))
|
|
(when production
|
|
(setf (state-transitions state) (list (cons nil (make-reduce-transition production))))
|
|
(incf n-forwarded-states))))
|
|
n-forwarded-states))
|
|
|
|
|
|
;;; ------------------------------------------------------------------------------------------------------
|
|
|
|
; Parse the input list of tokens to produce a parse tree.
|
|
; token-terminal is a function that returns a terminal symbol when given an input token.
|
|
(defun parse (grammar token-terminal input)
|
|
(labels
|
|
(;Continue the parse with the given parser stack and remainder of input.
|
|
(parse-step (stack input)
|
|
(if (endp input)
|
|
(parse-step-1 stack *end-marker* nil nil)
|
|
(let ((token (first input)))
|
|
(parse-step-1 stack (funcall token-terminal token) token (rest input)))))
|
|
|
|
;Same as parse-step except that the next input terminal has been determined already.
|
|
;input-rest contains the input tokens after the next token.
|
|
(parse-step-1 (stack terminal token input-rest)
|
|
(let* ((state (caar stack))
|
|
(transition (state-transition state terminal)))
|
|
(if transition
|
|
(case (transition-kind transition)
|
|
(:shift (parse-step (acons (transition-state transition) token stack) input-rest))
|
|
(:reduce (let ((production (transition-production transition))
|
|
(expansion nil))
|
|
(dotimes (i (production-rhs-length production))
|
|
(push (cdr (pop stack)) expansion))
|
|
(let* ((state (caar stack))
|
|
(dst-state (assert-non-null
|
|
(cdr (assoc (production-lhs production) (state-gotos state) :test *grammar-symbol-=*))))
|
|
(named-expansion (cons (production-name production) expansion)))
|
|
(parse-step-1 (acons dst-state named-expansion stack) terminal token input-rest))))
|
|
(:accept (cdar stack))
|
|
(t (error "Bad transition: ~S" transition)))
|
|
(error "Parse error on ~S followed by ~S ..." token (ldiff input-rest (nthcdr 10 input-rest)))))))
|
|
|
|
(parse-step (list (cons (grammar-start-state grammar) nil)) input)))
|
|
|
|
|
|
;;; ------------------------------------------------------------------------------------------------------
|
|
;;; ACTIONS
|
|
|
|
; Initialize the action-signatures hash table, setting each grammar symbol's signature
|
|
; to null for now. Also clear all production actions in the grammar.
|
|
(defun clear-actions (grammar)
|
|
(let ((action-signatures (make-hash-table :test *grammar-symbol-=*))
|
|
(terminals (grammar-terminals grammar))
|
|
(nonterminals (grammar-nonterminals grammar)))
|
|
(dotimes (i (length terminals))
|
|
(setf (gethash (svref terminals i) action-signatures) nil))
|
|
(dotimes (i (length nonterminals))
|
|
(setf (gethash (svref nonterminals i) action-signatures) nil))
|
|
(setf (grammar-action-signatures grammar) action-signatures)
|
|
(each-grammar-production
|
|
grammar
|
|
#'(lambda (production)
|
|
(setf (production-actions production) nil)
|
|
(setf (production-n-action-args production) nil)
|
|
(setf (production-evaluator production) nil)))
|
|
(clrhash (grammar-terminal-actions grammar))))
|
|
|
|
|
|
; Declare the type of action action-symbol, when called on general-grammar-symbol, to be type-expr.
|
|
; Signal an error on duplicate actions.
|
|
; It's OK if some of the symbol instances don't exist, as long as at least one does.
|
|
(defun declare-action (grammar general-grammar-symbol action-symbol type-expr)
|
|
(unless (and action-symbol (symbolp action-symbol))
|
|
(error "Bad action name ~S" action-symbol))
|
|
(let ((action-signatures (grammar-action-signatures grammar))
|
|
(grammar-symbols (general-grammar-symbol-instances grammar general-grammar-symbol))
|
|
(symbol-exists nil))
|
|
(dolist (grammar-symbol grammar-symbols)
|
|
(let ((signature (gethash grammar-symbol action-signatures :undefined)))
|
|
(unless (eq signature :undefined)
|
|
(setq symbol-exists t)
|
|
(when (assoc action-symbol signature :test #'eq)
|
|
(error "Attempt to redefine the type of action ~S on ~S" action-symbol grammar-symbol))
|
|
(setf (gethash grammar-symbol action-signatures)
|
|
(nconc signature (list (cons action-symbol type-expr))))
|
|
(if (nonterminal? grammar-symbol)
|
|
(dolist (production (rule-productions (grammar-rule grammar grammar-symbol)))
|
|
(setf (production-actions production)
|
|
(nconc (production-actions production) (list (cons action-symbol nil)))))
|
|
(let ((terminal-actions (grammar-terminal-actions grammar)))
|
|
(assert-type grammar-symbol terminal)
|
|
(setf (gethash grammar-symbol terminal-actions)
|
|
(nconc (gethash grammar-symbol terminal-actions) (list (cons action-symbol nil)))))))))
|
|
(unless symbol-exists
|
|
(error "Bad action grammar symbol ~S" grammar-symbols))))
|
|
|
|
|
|
; Return the list of pairs (action-symbol . type-or-type-expr) for this grammar-symbol.
|
|
; The pairs are in order from oldest to newest action-symbols added to this grammar-symbol.
|
|
(declaim (inline grammar-symbol-signature))
|
|
(defun grammar-symbol-signature (grammar grammar-symbol)
|
|
(gethash grammar-symbol (grammar-action-signatures grammar)))
|
|
|
|
|
|
; Return the list of action types of the grammar's user start-symbol.
|
|
(defun grammar-user-start-action-types (grammar)
|
|
(mapcar #'cdr (grammar-symbol-signature grammar (gramar-user-start-symbol grammar))))
|
|
|
|
|
|
; If action action-symbol is declared on grammar-symbol, return two values:
|
|
; t, and
|
|
; the action's type-expr;
|
|
; If not, return nil.
|
|
(defun action-declaration (grammar grammar-symbol action-symbol)
|
|
(let ((declaration (assoc action-symbol (grammar-symbol-signature grammar grammar-symbol) :test #'eq)))
|
|
(and declaration
|
|
(values t (cdr declaration)))))
|
|
|
|
|
|
; Call f on every action declaration, passing it two arguments:
|
|
; the grammar-symbol;
|
|
; a pair (action-symbol . type-expr).
|
|
; f may modify the action's type-expr.
|
|
(defun each-action-declaration (grammar f)
|
|
(maphash #'(lambda (grammar-symbol signature)
|
|
(dolist (action-declaration signature)
|
|
(funcall f grammar-symbol action-declaration)))
|
|
(grammar-action-signatures grammar)))
|
|
|
|
|
|
; Define action action-symbol, when called on the production with the given name,
|
|
; to be action-expr. The action should have been declared already.
|
|
(defun define-action (grammar production-name action-symbol type action-expr)
|
|
(dolist (production (general-production-productions (grammar-general-production grammar production-name)))
|
|
(let ((definition (assoc action-symbol (production-actions production) :test #'eq)))
|
|
(cond
|
|
((null definition)
|
|
(error "Attempt to define action ~S on ~S, which hasn't been declared yet" action-symbol production-name))
|
|
((cdr definition)
|
|
(error "Duplicate definition of action ~S on ~S" action-symbol production-name))
|
|
(t (setf (cdr definition) (make-action type action-expr)))))))
|
|
|
|
|
|
; Define action action-symbol, when called on the given terminal,
|
|
; to execute the given function, which should take a token as an input and
|
|
; produce a value of the proper type as output.
|
|
; The action should have been declared already.
|
|
(defun define-terminal-action (grammar terminal action-symbol action-function)
|
|
(assert-type action-function function)
|
|
(let ((definition (assoc action-symbol (gethash terminal (grammar-terminal-actions grammar)) :test #'eq)))
|
|
(cond
|
|
((null definition)
|
|
(error "Attempt to define action ~S on ~S, which hasn't been declared yet" action-symbol terminal))
|
|
((cdr definition)
|
|
(error "Duplicate definition of action ~S on ~S" action-symbol terminal))
|
|
(t (setf (cdr definition) action-function)))))
|
|
|
|
|
|
|
|
; Parse the input list of tokens to produce a list of action results.
|
|
; token-terminal is a function that returns a terminal symbol when given an input token.
|
|
; If trace is:
|
|
; nil, don't print trace information
|
|
; :code, print trace information, including action code
|
|
; other print trace information
|
|
; Return two values:
|
|
; the list of action results;
|
|
; the list of action results' types.
|
|
(defun action-parse (grammar token-terminal input &key trace)
|
|
(labels
|
|
(;Continue the parse with the given stacks and remainder of input.
|
|
;When trace is non-null, type-stack contains the types of corresponding value-stack entries.
|
|
(parse-step (state-stack value-stack type-stack input)
|
|
(if (endp input)
|
|
(parse-step-1 state-stack value-stack type-stack *end-marker* nil nil)
|
|
(let ((token (first input)))
|
|
(parse-step-1 state-stack value-stack type-stack (funcall token-terminal token) token (rest input)))))
|
|
|
|
;Same as parse-step except that the next input terminal has been determined already.
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;input-rest contains the input tokens after the next token.
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(parse-step-1 (state-stack value-stack type-stack terminal token input-rest)
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(let* ((state (car state-stack))
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(transition (state-transition state terminal)))
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(when trace
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(format *trace-output* "S~D: ~@_" (state-number state))
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(print-values (reverse value-stack) (reverse type-stack) *trace-output*)
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(pprint-newline :mandatory *trace-output*))
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(if transition
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(case (transition-kind transition)
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(:shift
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(when trace
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(format *trace-output* " shift ~W~:@_" terminal)
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(dolist (action-signature (grammar-symbol-signature grammar terminal))
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(push (cdr action-signature) type-stack)))
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(dolist (action-function-binding (gethash terminal (grammar-terminal-actions grammar)))
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(push (funcall (cdr action-function-binding) token) value-stack))
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(parse-step (cons (transition-state transition) state-stack) value-stack type-stack input-rest))
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(:reduce
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(let ((production (transition-production transition)))
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(when trace
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(write-string " reduce " *trace-output*)
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(if (eq trace :code)
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(write production :stream *trace-output* :pretty t)
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(print-production production *trace-output*))
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(pprint-newline :mandatory *trace-output*))
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(let* ((state-stack (nthcdr (production-rhs-length production) state-stack))
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(state (car state-stack))
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(dst-state (assert-non-null
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(cdr (assoc (production-lhs production) (state-gotos state) :test *grammar-symbol-=*))))
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(value-stack (funcall (production-evaluator production) value-stack)))
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(when trace
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(setq type-stack (nthcdr (production-n-action-args production) type-stack))
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(dolist (action-signature (grammar-symbol-signature grammar (production-lhs production)))
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(push (cdr action-signature) type-stack)))
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(parse-step-1 (cons dst-state state-stack) value-stack type-stack terminal token input-rest))))
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(:accept
|
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(when trace
|
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(format *trace-output* " accept~:@_"))
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(values
|
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(nreverse value-stack)
|
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(if trace
|
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(nreverse type-stack)
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(grammar-user-start-action-types grammar))))
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(t (error "Bad transition: ~S" transition)))
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(error "Parse error on ~S followed by ~S ..." token (ldiff input-rest (nthcdr 10 input-rest)))))))
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(parse-step (list (grammar-start-state grammar)) nil nil input)))
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