gecko-dev/js2/semantics/Parser.lisp

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1999-01-30 01:19:00 +00:00
;;; The contents of this file are subject to the Netscape Public License
;;; Version 1.0 (the "NPL"); you may not use this file except in
;;; compliance with the NPL. You may obtain a copy of the NPL at
;;; http://www.mozilla.org/NPL/
;;;
;;; Software distributed under the NPL is distributed on an "AS IS" basis,
;;; WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
;;; for the specific language governing rights and limitations under the
;;; NPL.
;;;
;;; The Initial Developer of this code under the NPL is Netscape
;;; Communications Corporation. Portions created by Netscape are
;;; Copyright (C) 1998 Netscape Communications Corporation. All Rights
;;; Reserved.
;;;
;;; LALR(1) and LR(1) grammar generator
;;;
;;; Waldemar Horwat (waldemar@netscape.com)
;;;
;;; ------------------------------------------------------------------------------------------------------
; kernel-item-alist is a list of pairs (item . prev), where item is a kernel item
; and prev is either nil or a laitem. kernel is a list of the kernel items in a canonical order.
; Return a new state with the given list of kernel items and state number.
; For each non-null prev in kernel-item-alist, update (laitem-propagates prev) to include the
; corresponding laitem in the new state.
(defun make-state (grammar kernel kernel-item-alist number initial-lookaheads)
(let ((laitems nil)
(laitems-hash (make-hash-table :test #'eq)))
(labels
;Create a laitem for this item and add the association item->laitem to the laitems-hash
;hash table if it's not there already. Regardless of whether a new laitem was created,
;update the laitem's lookaheads to also include the given lookaheads.
;If prev is non-null, update (laitem-propagates prev) to include the laitem if it's not
;already included there.
;If a new laitem was created and its first symbol after the dot exists and is a
;nonterminal A, recursively close items A->.rhs corresponding to all rhs's in the
;grammar's rule for A.
((close-item (item lookaheads prev)
(let ((laitem (gethash item laitems-hash)))
(if laitem
(setf (laitem-lookaheads laitem)
(terminalset-union (laitem-lookaheads laitem) lookaheads))
(let ((item-next-symbol (item-next-symbol item)))
(setq laitem (allocate-laitem grammar item lookaheads))
(push laitem laitems)
(setf (gethash item laitems-hash) laitem)
(when (nonterminal? item-next-symbol)
(multiple-value-bind (next-lookaheads epsilon-lookahead)
(string-initial-terminals grammar (rest (item-unseen item)))
(let ((next-prev (and epsilon-lookahead laitem)))
(dolist (production (rule-productions (grammar-rule grammar item-next-symbol)))
(close-item (make-item grammar production 0) next-lookaheads next-prev)))))))
(when prev
(pushnew laitem (laitem-propagates prev))))))
(dolist (acons kernel-item-alist nil)
(let ((item (car acons))
(prev (cdr acons)))
(close-item item initial-lookaheads prev)))
(allocate-state number kernel (nreverse laitems)))))
; f is a function that takes two arguments:
; a grammar symbol, and
; a list of kernel items in order of increasing item number.
; a list of pairs (item . prev), where item is a kernel item and prev is a laitem;
; For each possible symbol X that can be shifted while in the given state S, call
; f giving it S and the list of items that constitute the kernel of that shift's destination
; state. The prev's are the sources of the corresponding shifted items.
(defun state-each-shift-item-alist (f state)
(let ((shift-symbols-hash (make-hash-table :test *grammar-symbol-=*)))
(dolist (source-laitem (state-laitems state))
(let* ((source-item (laitem-item source-laitem))
(shift-symbol (item-next-symbol source-item)))
(when shift-symbol
(push (cons (item-next source-item) source-laitem)
(gethash shift-symbol shift-symbols-hash)))))
;Use dolist/gethash instead of maphash to make state assignments deterministic.
(dolist (shift-symbol (sorted-hash-table-keys shift-symbols-hash))
(let ((kernel-item-alist (gethash shift-symbol shift-symbols-hash)))
(funcall f shift-symbol (sort (mapcar #'car kernel-item-alist) #'< :key #'item-number) kernel-item-alist)))))
;;; ------------------------------------------------------------------------------------------------------
;;; LR(1)
; kernel-item-alist should have the same kernel items as state.
; Return true if the prev lookaheads in kernel-item-alist are the same as or subsets of
; the corresponding lookaheads in the state's kernel laitems.
(defun state-subsumes-lookaheads (state kernel-item-alist)
(every
#'(lambda (acons)
(terminalset-<= (laitem-lookaheads (cdr acons))
(laitem-lookaheads (state-laitem state (car acons)))))
kernel-item-alist))
; kernel-item-alist should have the same kernel items as state.
; Return true if the prev lookaheads in kernel-item-alist are weakly compatible
; with the lookaheads in the state's kernel laitems.
(defun state-weakly-compatible (state kernel-item-alist)
(labels
((lookahead-weakly-compatible (lookahead1a lookahead1b lookahead2a lookahead2b)
(or (and (terminalsets-disjoint lookahead1a lookahead2b)
(terminalsets-disjoint lookahead1b lookahead2a))
(not (terminalsets-disjoint lookahead1a lookahead1b))
(not (terminalsets-disjoint lookahead2a lookahead2b))))
(lookahead-list-weakly-compatible (lookahead1a lookaheads1 lookahead2a lookaheads2)
(or (endp lookaheads1)
(and (lookahead-weakly-compatible lookahead1a (first lookaheads1) lookahead2a (first lookaheads2))
(lookahead-list-weakly-compatible lookahead1a (rest lookaheads1) lookahead2a (rest lookaheads2)))))
(lookahead-lists-weakly-compatible (lookaheads1 lookaheads2)
(or (endp lookaheads1)
(and (lookahead-list-weakly-compatible (first lookaheads1) (rest lookaheads1) (first lookaheads2) (rest lookaheads2))
(lookahead-lists-weakly-compatible (rest lookaheads1) (rest lookaheads2))))))
(or (= (length kernel-item-alist) 1)
(lookahead-lists-weakly-compatible
(mapcar #'(lambda (acons) (laitem-lookaheads (state-laitem state (car acons)))) kernel-item-alist)
(mapcar #'(lambda (acons) (laitem-lookaheads (cdr acons))) kernel-item-alist)))))
; Propagate all lookaheads in the state.
(defun propagate-internal-lookaheads (state)
(dolist (src-laitem (state-laitems state))
(let ((src-lookaheads (laitem-lookaheads src-laitem)))
(dolist (dst-laitem (laitem-propagates src-laitem))
(setf (laitem-lookaheads dst-laitem)
(terminalset-union (laitem-lookaheads dst-laitem) src-lookaheads))))))
; Propagate all lookaheads in kernel-item-alist, which must target destination-state.
; Mark destination-state as dirty in the dirty-states hash table.
(defun propagate-external-lookaheads (kernel-item-alist destination-state dirty-states)
(dolist (acons kernel-item-alist)
(let ((dest-laitem (state-laitem destination-state (car acons)))
(src-laitem (cdr acons)))
(setf (laitem-lookaheads dest-laitem)
(terminalset-union (laitem-lookaheads dest-laitem) (laitem-lookaheads src-laitem)))))
(setf (gethash destination-state dirty-states) t))
; 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-lr-states (grammar)
(let* ((initial-item (make-item grammar (grammar-start-production grammar) 0))
(lr-states-hash (make-hash-table :test #'equal)) ;kernel -> list of states with that kernel
(initial-kernel (list initial-item))
(initial-state (make-state grammar initial-kernel (list (cons initial-item nil)) 0 (make-terminalset grammar *end-marker*)))
(states (list initial-state))
(next-state-number 1))
(setf (gethash initial-kernel lr-states-hash) (list initial-state))
(do ((source-states (list initial-state))
(dirty-states (make-hash-table :test #'eq))) ;Set of states whose kernel lookaheads changed and haven't been propagated yet
((and (endp source-states) (zerop (hash-table-count dirty-states))))
(labels
((make-destination-state (kernel kernel-item-alist)
(let* ((possible-destination-states (gethash kernel lr-states-hash))
(destination-state (find-if #'(lambda (possible-destination-state)
(state-subsumes-lookaheads possible-destination-state kernel-item-alist))
possible-destination-states)))
(cond
(destination-state)
((setq destination-state (find-if #'(lambda (possible-destination-state)
(state-weakly-compatible possible-destination-state kernel-item-alist))
possible-destination-states))
(propagate-external-lookaheads kernel-item-alist destination-state dirty-states))
(t
(setq destination-state (make-state grammar kernel kernel-item-alist next-state-number *empty-terminalset*))
(propagate-external-lookaheads kernel-item-alist destination-state dirty-states)
(push destination-state (gethash kernel lr-states-hash))
(incf next-state-number)
(push destination-state states)
(push destination-state source-states)))
destination-state))
(update-destination-state (destination-state kernel-item-alist)
(cond
((state-subsumes-lookaheads destination-state kernel-item-alist)
destination-state)
((state-weakly-compatible destination-state kernel-item-alist)
(propagate-external-lookaheads kernel-item-alist destination-state dirty-states)
destination-state)
(t (make-destination-state (state-kernel destination-state) kernel-item-alist)))))
(if source-states
(let ((source-state (pop source-states)))
(remhash source-state dirty-states)
(propagate-internal-lookaheads source-state)
(state-each-shift-item-alist
#'(lambda (shift-symbol kernel kernel-item-alist)
(let ((destination-state (make-destination-state kernel kernel-item-alist)))
(if (nonterminal? shift-symbol)
(push (cons shift-symbol destination-state)
(state-gotos source-state))
(push (cons shift-symbol (make-shift-transition destination-state))
(state-transitions source-state)))))
source-state))
(dolist (dirty-state (sort (hash-table-keys dirty-states) #'< :key #'state-number))
(when (remhash dirty-state dirty-states)
(propagate-internal-lookaheads dirty-state)
(state-each-shift-item-alist
#'(lambda (shift-symbol kernel kernel-item-alist)
(declare (ignore kernel))
(if (nonterminal? shift-symbol)
(let* ((destination-binding (assoc shift-symbol (state-gotos dirty-state) :test *grammar-symbol-=*))
(destination-state (assert-non-null (cdr destination-binding))))
(setf (cdr destination-binding) (update-destination-state destination-state kernel-item-alist)))
(let* ((destination-transition (cdr (assoc shift-symbol (state-transitions dirty-state) :test *grammar-symbol-=*)))
(destination-state (assert-non-null (transition-state destination-transition))))
(setf (transition-state destination-transition)
(update-destination-state destination-state kernel-item-alist)))))
dirty-state))))))
(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)) 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)
(pushnew (state-laitem destination-state (car acons)) (laitem-propagates (cdr acons))))
(progn
(setq destination-state (make-state grammar kernel kernel-item-alist 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))
(push (cons shift-symbol (make-shift-transition destination-state))
(state-transitions source-state)))))
source-state)))
(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 (dst-laitem (laitem-propagates dirty-laitem))
(let* ((old-dst-lookaheads (laitem-lookaheads dst-laitem))
(new-dst-lookaheads (terminalset-union old-dst-lookaheads src-lookaheads)))
(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)
(if (grammar-symbol-= (item-lhs item) *start-nonterminal*)
(when (terminal-in-terminalset grammar *end-marker* (laitem-lookaheads laitem))
(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
(laitem-lookaheads laitem))))))
(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).
(defun report-and-fix-ambiguities (grammar stream)
(let ((found-ambiguities nil))
(pprint-logical-block (stream nil)
(dolist (state (grammar-states grammar))
(labels
((report-ambiguity (transition-cons other-transition-conses)
(unless found-ambiguities
(setq found-ambiguities t)
(format stream "~&Ambiguities:")
(pprint-indent :block 2 stream))
(pprint-newline :mandatory 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
(pprint-newline :mandatory stream))))
; Erase the existing parser, if any, for the given grammar.
(defun clear-parser (grammar)
(clrhash (grammar-items-hash grammar))
(setf (grammar-states grammar) nil))
; Construct a LR or LALR parser in the given grammar. kind should be either :lalr-1 or :lr-1.
; Return the grammar.
(defun compile-parser (grammar kind)
(clear-parser grammar)
(ecase kind
(:lalr-1
(add-all-lalr-states grammar)
(propagate-lalr-lookaheads grammar))
(:lr-1
(add-all-lr-states grammar)))
(finish-transitions grammar)
(report-and-fix-ambiguities grammar *error-output*)
grammar)
; Make the grammar and compile its parser. kind should be either :lalr-1 or :lr-1.
(defun make-and-compile-grammar (kind parametrization start-symbol grammar-source &optional excluded-nonterminals-source)
(compile-parser (make-grammar parametrization start-symbol grammar-source excluded-nonterminals-source)
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kind))
;;; ------------------------------------------------------------------------------------------------------
; 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 (cdr (assoc terminal (state-transitions state) :test *grammar-symbol-=*))))
(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-code 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 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 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.
(parse-step (state-stack value-stack input)
(if (endp input)
(parse-step-1 state-stack value-stack *end-marker* nil nil)
(let ((token (first input)))
(parse-step-1 state-stack value-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 (state-stack value-stack terminal token input-rest)
(let* ((state (car state-stack))
(transition (cdr (assoc terminal (state-transitions state) :test *grammar-symbol-=*))))
(if transition
(case (transition-kind transition)
(:shift
(dolist (action-function-binding (gethash terminal (grammar-terminal-actions grammar)))
(push (funcall (cdr action-function-binding) token) value-stack))
(parse-step (cons (transition-state transition) state-stack) value-stack input-rest))
(:reduce
(let* ((production (transition-production transition))
(state-stack (nthcdr (production-rhs-length production) state-stack))
(state (car state-stack))
(dst-state (assert-non-null
(cdr (assoc (production-lhs production) (state-gotos state) :test *grammar-symbol-=*))))
(value-stack (funcall (production-evaluator production) value-stack)))
(parse-step-1 (cons dst-state state-stack) value-stack terminal token input-rest)))
(:accept (values (nreverse value-stack) (grammar-user-start-action-types grammar)))
(t (error "Bad transition: ~S" transition)))
(error "Parse error on ~S followed by ~S ..." token (ldiff input-rest (nthcdr 10 input-rest)))))))
(if trace
(trace-action-parse grammar token-terminal input trace)
(parse-step (list (grammar-start-state grammar)) nil input))))
; Same as action-parse, but with tracing information
; If trace is:
; :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 trace-action-parse (grammar token-terminal input trace)
(labels
(;Continue the parse with the given stacks and remainder of input.
;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.
;input-rest contains the input tokens after the next token.
(parse-step-1 (state-stack value-stack type-stack terminal token input-rest)
(let* ((state (car state-stack))
(transition (cdr (assoc terminal (state-transitions state) :test *grammar-symbol-=*))))
(format *trace-output* "S~D: ~@_" (state-number state))
(print-values (reverse value-stack) (reverse type-stack) *trace-output*)
(pprint-newline :mandatory *trace-output*)
(if transition
(case (transition-kind transition)
(:shift
(format *trace-output* " shift ~W~:@_" terminal)
(dolist (action-function-binding (gethash terminal (grammar-terminal-actions grammar)))
(push (funcall (cdr action-function-binding) token) value-stack))
(dolist (action-signature (grammar-symbol-signature grammar terminal))
(push (cdr action-signature) type-stack))
(parse-step (cons (transition-state transition) state-stack) value-stack type-stack input-rest))
(:reduce
(let ((production (transition-production transition)))
(write-string " reduce " *trace-output*)
(if (eq trace :code)
(write production :stream *trace-output* :pretty t)
(print-production production *trace-output*))
(pprint-newline :mandatory *trace-output*)
(let* ((state-stack (nthcdr (production-rhs-length production) state-stack))
(state (car state-stack))
(dst-state (assert-non-null
(cdr (assoc (production-lhs production) (state-gotos state) :test *grammar-symbol-=*))))
(value-stack (funcall (production-evaluator production) value-stack))
(type-stack (nthcdr (production-n-action-args production) type-stack)))
(dolist (action-signature (grammar-symbol-signature grammar (production-lhs production)))
(push (cdr action-signature) type-stack))
(parse-step-1 (cons dst-state state-stack) value-stack type-stack terminal token input-rest))))
(:accept
(format *trace-output* " accept~:@_")
(values (nreverse value-stack) (nreverse type-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 (grammar-start-state grammar)) nil nil input)))