1 ;;; semantic/wisent/wisent.el --- GNU Bison for Emacs - Runtime
3 ;;; Copyright (C) 2002-2007, 2009-2013 Free Software Foundation, Inc.
5 ;; Author: David Ponce <david@dponce.com>
6 ;; Maintainer: David Ponce <david@dponce.com>
7 ;; Created: 30 January 2002
10 ;; This file is part of GNU Emacs.
12 ;; GNU Emacs is free software: you can redistribute it and/or modify
13 ;; it under the terms of the GNU General Public License as published by
14 ;; the Free Software Foundation, either version 3 of the License, or
15 ;; (at your option) any later version.
17 ;; GNU Emacs is distributed in the hope that it will be useful,
18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;; GNU General Public License for more details.
22 ;; You should have received a copy of the GNU General Public License
23 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
27 ;; Parser engine and runtime of Wisent.
29 ;; Wisent (the European Bison ;-) is an Elisp implementation of the
30 ;; GNU Compiler Compiler Bison. The Elisp code is a port of the C
31 ;; code of GNU Bison 1.28 & 1.31.
33 ;; For more details on the basic concepts for understanding Wisent,
34 ;; read the Bison manual ;)
36 ;; For more details on Wisent itself read the Wisent manual.
45 /\\_.-^^^-._/\\ The GNU
47 ( `o ` (European ;-) Bison
61 (if (fboundp 'char-valid-p)
62 (defalias 'wisent-char-p 'char-valid-p)
63 (defalias 'wisent-char-p 'char-or-char-int-p)))
65 ;;; Printed representation of terminals and nonterminals
66 (defconst wisent-escape-sequence-strings
69 (?\b . "'\\b'") ; backspace, BS, C-h
70 (?\t . "'\\t'") ; tab, TAB, C-i
71 (?\n . "'\\n'") ; newline, C-j
72 (?\v . "'\\v'") ; vertical tab, C-k
73 (?\f . "'\\f'") ; formfeed character, C-l
74 (?\r . "'\\r'") ; carriage return, RET, C-m
75 (?\e . "'\\e'") ; escape character, ESC, C-[
76 (?\\ . "'\\'") ; backslash character, \
77 (?\d . "'\\d'") ; delete character, DEL
79 "Printed representation of usual escape sequences.")
81 (defsubst wisent-item-to-string (item)
82 "Return a printed representation of ITEM.
83 ITEM can be a nonterminal or terminal symbol, or a character literal."
84 (if (wisent-char-p item)
85 (or (cdr (assq item wisent-escape-sequence-strings))
89 (defsubst wisent-token-to-string (token)
90 "Return a printed representation of lexical token TOKEN."
91 (format "%s%s(%S)" (wisent-item-to-string (car token))
92 (if (nth 2 token) (format "@%s" (nth 2 token)) "")
96 (defconst wisent-eoi-term '$EOI
97 "End Of Input token.")
99 (defconst wisent-error-term 'error
100 "Error recovery token.")
102 (defconst wisent-accept-tag 'accept
103 "Accept result after input successfully parsed.")
105 (defconst wisent-error-tag 'error
106 "Process a syntax error.")
108 ;;; Special functions
109 (defun wisent-automaton-p (obj)
110 "Return non-nil if OBJ is a LALR automaton.
111 If OBJ is a symbol check its value."
112 (and obj (symbolp obj) (boundp obj)
113 (setq obj (symbol-value obj)))
114 (and (vectorp obj) (= 4 (length obj))
115 (vectorp (aref obj 0)) (vectorp (aref obj 1))
116 (= (length (aref obj 0)) (length (aref obj 1)))
117 (listp (aref obj 2)) (vectorp (aref obj 3))))
119 (defsubst wisent-region (&rest positions)
120 "Return the start/end positions of the region including POSITIONS.
121 Each element of POSITIONS is a pair (START-POS . END-POS) or nil. The
122 returned value is the pair (MIN-START-POS . MAX-END-POS) or nil if no
123 POSITIONS are available."
124 (let ((pl (delq nil positions)))
126 (cons (apply #'min (mapcar #'car pl))
127 (apply #'max (mapcar #'cdr pl))))))
130 (defvar wisent-parse-verbose-flag nil
131 "*Non-nil means to issue more messages while parsing.")
133 (defun wisent-parse-toggle-verbose-flag ()
134 "Toggle whether to issue more messages while parsing."
136 (setq wisent-parse-verbose-flag (not wisent-parse-verbose-flag))
137 (when (called-interactively-p 'interactive)
138 (message "More messages while parsing %sabled"
139 (if wisent-parse-verbose-flag "en" "dis"))))
141 (defsubst wisent-message (string &rest args)
142 "Print a one-line message if `wisent-parse-verbose-flag' is set.
143 Pass STRING and ARGS arguments to `message'."
144 (and wisent-parse-verbose-flag
145 (apply 'message string args)))
147 ;;;; --------------------
148 ;;;; The LR parser engine
149 ;;;; --------------------
151 (defcustom wisent-parse-max-stack-size 500
152 "The parser stack size."
156 (defcustom wisent-parse-max-recover 3
157 "Number of tokens to shift before turning off error status."
161 (defvar wisent-discarding-token-functions nil
162 "List of functions to be called when discarding a lexical token.
163 These functions receive the lexical token discarded.
164 When the parser encounters unexpected tokens, it can discards them,
165 based on what directed by error recovery rules. Either when the
166 parser reads tokens until one is found that can be shifted, or when an
167 semantic action calls the function `wisent-skip-token' or
169 For language specific hooks, make sure you define this as a local
172 (defvar wisent-pre-parse-hook nil
173 "Normal hook run just before entering the LR parser engine.")
175 (defvar wisent-post-parse-hook nil
176 "Normal hook run just after the LR parser engine terminated.")
178 (defvar wisent-loop nil
179 "The current parser action.
180 Stop parsing when set to nil.
181 This variable only has meaning in the scope of `wisent-parse'.")
183 (defvar wisent-nerrs nil
184 "The number of parse errors encountered so far.")
186 (defvar wisent-lookahead nil
187 "The lookahead lexical token.
188 This value is non-nil if the parser terminated because of an
189 unrecoverable error.")
191 ;; Variables and macros that are useful in semantic actions.
192 (defvar wisent-parse-lexer-function nil
193 "The user supplied lexer function.
194 This function don't have arguments.
195 This variable only has meaning in the scope of `wisent-parse'.")
197 (defvar wisent-parse-error-function nil
198 "The user supplied error function.
199 This function must accept one argument, a message string.
200 This variable only has meaning in the scope of `wisent-parse'.")
202 (defvar wisent-input nil
203 "The last token read.
204 This variable only has meaning in the scope of `wisent-parse'.")
206 (defvar wisent-recovering nil
207 "Non-nil means that the parser is recovering.
208 This variable only has meaning in the scope of `wisent-parse'.")
210 ;; Variables that only have meaning in the scope of a semantic action.
211 ;; These global definitions avoid byte-compiler warnings.
216 (defmacro wisent-lexer ()
217 "Obtain the next terminal in input."
218 '(funcall wisent-parse-lexer-function))
220 (defmacro wisent-error (msg)
221 "Call the user supplied error reporting function with message MSG."
222 `(funcall wisent-parse-error-function ,msg))
224 (defmacro wisent-errok ()
225 "Resume generating error messages immediately for subsequent syntax errors.
226 This is useful primarily in error recovery semantic actions."
227 '(setq wisent-recovering nil))
229 (defmacro wisent-clearin ()
230 "Discard the current lookahead token.
231 This will cause a new lexical token to be read.
232 This is useful primarily in error recovery semantic actions."
233 '(setq wisent-input nil))
235 (defmacro wisent-abort ()
236 "Abort parsing and save the lookahead token.
237 This is useful primarily in error recovery semantic actions."
238 '(setq wisent-lookahead wisent-input
241 (defmacro wisent-set-region (start end)
242 "Change the region of text matched by the current nonterminal.
243 START and END are respectively the beginning and end positions of the
244 region. If START or END values are not a valid positions the region
246 `(setq $region (and (number-or-marker-p ,start)
247 (number-or-marker-p ,end)
248 (cons ,start ,end))))
250 (defun wisent-skip-token ()
251 "Skip the lookahead token in order to resume parsing.
253 Must be used in error recovery semantic actions."
254 (if (eq (car wisent-input) wisent-eoi-term)
255 ;; Does nothing at EOI to avoid infinite recovery loop.
257 (wisent-message "%s: skip %s" $action
258 (wisent-token-to-string wisent-input))
260 'wisent-discarding-token-functions wisent-input)
264 (defun wisent-skip-block (&optional bounds)
265 "Safely skip a parenthesized block in order to resume parsing.
267 Must be used in error recovery semantic actions.
268 Optional argument BOUNDS is a pair (START . END) which indicates where
269 the parenthesized block starts. Typically the value of a `$regionN'
270 variable, where `N' is the Nth element of the current rule components
271 that match the block beginning. It defaults to the value of the
273 (let ((start (car (or bounds $region)))
275 (if (not (number-or-marker-p start))
276 ;; No nonterminal region available, skip the lookahead token.
278 ;; Try to skip a block.
279 (if (not (setq end (save-excursion
281 (and (looking-at "\\s(")
283 (1- (scan-lists (point) 1 0))
285 ;; Not actually a block, skip the lookahead token.
287 ;; OK to safely skip the block, so read input until a matching
288 ;; close paren or EOI is encountered.
289 (setq input wisent-input)
290 (while (and (not (eq (car input) wisent-eoi-term))
291 (< (nth 2 input) end))
293 'wisent-discarding-token-functions input)
294 (setq input (wisent-lexer)))
295 (wisent-message "%s: in enclosing block, skip from %s to %s"
297 (wisent-token-to-string wisent-input)
298 (wisent-token-to-string input))
299 (if (eq (car wisent-input) wisent-eoi-term)
300 ;; Does nothing at EOI to avoid infinite recovery loop.
304 ;; Set end of $region to end of block.
305 (wisent-set-region (car $region) (1+ end))
308 ;;; Core parser engine
309 (defsubst wisent-production-bounds (stack i j)
310 "Determine the start and end locations of a production value.
311 Return a pair (START . END), where START is the first available start
312 location, and END the last available end location, in components
313 values of the rule currently reduced.
314 Return nil when no component location is available.
315 STACK is the parser stack.
316 I and J are the indices in STACK of respectively the value of the
317 first and last components of the current rule.
318 This function is for internal use by semantic actions' generated
320 (let ((f (cadr (aref stack i)))
321 (l (cddr (aref stack j))))
324 ((not f) (setq f (cadr (aref stack (setq i (+ i 2))))))
325 ((not l) (setq l (cddr (aref stack (setq j (- j 2))))))
327 (and f l (cons f l))))
329 (defmacro wisent-parse-action (i al)
330 "Return the next parser action.
331 I is a token item number and AL is the list of (item . action)
332 available at current state. The first element of AL contains the
333 default action for this state."
334 `(cdr (or (assq ,i ,al) (car ,al))))
336 (defsubst wisent-parse-start (start starts)
337 "Return the first lexical token to shift for START symbol.
338 STARTS is the table of allowed start symbols or nil if the LALR
339 automaton has only one entry point."
341 ;; Only one entry point, return the first lexical token
342 ;; available in input.
344 ;; Multiple start symbols defined, return the internal lexical
345 ;; token associated to START. By default START is the first
346 ;; nonterminal defined in STARTS.
347 (let ((token (cdr (if start (assq start starts) (car starts)))))
349 (list token (symbol-name token))
350 (error "Invalid start symbol %s" start)))))
352 (defun wisent-parse (automaton lexer &optional error start)
353 "Parse input using the automaton specified in AUTOMATON.
355 - AUTOMATON is an LALR(1) automaton generated by
356 `wisent-compile-grammar'.
358 - LEXER is a function with no argument called by the parser to obtain
359 the next terminal (token) in input.
361 - ERROR is an optional reporting function called when a parse error
362 occurs. It receives a message string to report. It defaults to the
363 function `wisent-message'.
365 - START specify the start symbol (nonterminal) used by the parser as
366 its goal. It defaults to the start symbol defined in the grammar
367 \(see also `wisent-compile-grammar')."
368 (run-hooks 'wisent-pre-parse-hook)
369 (let* ((actions (aref automaton 0))
370 (gotos (aref automaton 1))
371 (starts (aref automaton 2))
372 (stack (make-vector wisent-parse-max-stack-size nil))
375 (wisent-parse-error-function (or error 'wisent-message))
376 (wisent-parse-lexer-function lexer)
377 (wisent-recovering nil)
378 (wisent-input (wisent-parse-start start starts))
379 state tokid choices choice)
380 (setq wisent-nerrs 0 ;; Reset parse error counter
381 wisent-lookahead nil) ;; and lookahead token
382 (aset stack 0 0) ;; Initial state
384 (setq state (aref stack sp)
385 tokid (car wisent-input)
386 wisent-loop (wisent-parse-action tokid (aref actions state)))
389 ;; Input successfully parsed
390 ;; -------------------------
391 ((eq wisent-loop wisent-accept-tag)
392 (setq wisent-loop nil))
394 ;; Syntax error in input
395 ;; ---------------------
396 ((eq wisent-loop wisent-error-tag)
397 ;; Report this error if not already recovering from an error.
398 (setq choices (aref actions state))
399 (or wisent-recovering
401 (format "Syntax error, unexpected %s, expecting %s"
402 (wisent-token-to-string wisent-input)
403 (mapconcat 'wisent-item-to-string
404 (delq wisent-error-term
405 (mapcar 'car (cdr choices)))
407 ;; Increment the error counter
408 (setq wisent-nerrs (1+ wisent-nerrs))
409 ;; If just tried and failed to reuse lookahead token after an
410 ;; error, discard it.
411 (if (eq wisent-recovering wisent-parse-max-recover)
412 (if (eq tokid wisent-eoi-term)
413 (wisent-abort) ;; Terminate if at end of input.
414 (wisent-message "Error recovery: skip %s"
415 (wisent-token-to-string wisent-input))
417 'wisent-discarding-token-functions wisent-input)
418 (setq wisent-input (wisent-lexer)))
420 ;; Else will try to reuse lookahead token after shifting the
423 ;; Each real token shifted decrements this.
424 (setq wisent-recovering wisent-parse-max-recover)
425 ;; Pop the value/state stack to see if an action associated
426 ;; to special terminal symbol 'error exists.
427 (while (and (>= sp 0)
428 (not (and (setq state (aref stack sp)
429 choices (aref actions state)
430 choice (assq wisent-error-term choices))
431 (natnump (cdr choice)))))
435 ;; No 'error terminal was found. Just terminate.
437 ;; Try to recover and continue parsing.
438 ;; Shift the error terminal.
439 (setq state (cdr choice) ; new state
441 (aset stack (1- sp) nil) ; push value
442 (aset stack sp state) ; push new state
443 ;; Adjust input to error recovery state. Unless 'error
444 ;; triggers a reduction, eat the input stream until an
445 ;; expected terminal symbol is found, or EOI is reached.
446 (if (cdr (setq choices (aref actions state)))
447 (while (not (or (eq (car wisent-input) wisent-eoi-term)
448 (assq (car wisent-input) choices)))
449 (wisent-message "Error recovery: skip %s"
450 (wisent-token-to-string wisent-input))
452 'wisent-discarding-token-functions wisent-input)
453 (setq wisent-input (wisent-lexer)))))))
455 ;; Shift current token on top of the stack
456 ;; ---------------------------------------
457 ((natnump wisent-loop)
458 ;; Count tokens shifted since error; after
459 ;; `wisent-parse-max-recover', turn off error status.
460 (setq wisent-recovering (and (natnump wisent-recovering)
461 (> wisent-recovering 1)
462 (1- wisent-recovering)))
464 (aset stack (1- sp) (cdr wisent-input))
465 (aset stack sp wisent-loop)
466 (setq wisent-input (wisent-lexer)))
468 ;; Reduce by rule (call semantic action)
469 ;; -------------------------------------
471 (setq sp (funcall wisent-loop stack sp gotos))
472 (or wisent-input (setq wisent-input (wisent-lexer))))))
473 (run-hooks 'wisent-post-parse-hook)
474 (car (aref stack 1))))
476 (provide 'semantic/wisent/wisent)
479 ;; generated-autoload-load-name: "semantic/wisent/wisent"
482 ;;; semantic/wisent/wisent.el ends here