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peg-parser.scm

Revision 15, 19.2 kB (checked in by hayamizu, 17 years ago)
initial import

Line
1	#!/usr/bin/env gosh
2	;; -- coding: utf-8 mode: scheme --
3
4	;;;
5	;;; Original PEG Grammars
6	;;;
7	;; Hierarchical syntax
8	; Grammar <- Spacing Definition+ EndOfFile
9	; Definition <- Identifier LEFTARROW Expression
10	;
11	; Expression <- Sequence (SLASH Sequence)*
12	; Sequence <- Prefix*
13	; Prefix <- (AND / NOT)? Suffix
14	; Suffix <- Primary (QUESTION / STAR / PLUS)?
15	; Primary <- Identifier !LEFTARROW
16	; / OPEN Expression CLOSE
17	; / Literal / Class / DOT
18	;
19	;; Lexical syntax
20	; Identifier <- IdentStart IdentCont* Spacing
21	; IdentStart <- [a-zA-Z_]
22	; IdentCont <- IdentStart / [0-9]
23	;
24	; Literal <- ['] (!['] Char)* ['] Spacing
25	; / ["] (!["] Char)* ["] Spacing
26	; Class <- '[' (!']' Range)* ']' Spacing
27	; Range <- Char '-' Char / Char
28	; Char <- '\\' [nrt'"\[\]\\]
29	; / '\\' [0-2][0-7][0-7]
30	; / '\\' [0-7][0-7]?
31	; / !'\\' .
32	;
33	; LEFTARROW <- '<-' Spacing
34	; SLASH <- '/' Spacing
35	; AND <- '&' Spacing
36	; NOT <- '!' Spacing
37	; QUESTION <- '?' Spacing
38	; STAR <- '*' Spacing
39	; PLUS <- '+' Spacing
40	; OPEN <- '(' Spacing
41	; CLOSE <- ')' Spacing
42	; DOT <- '.' Spacing
43	;
44	; Spacing <- (Space / Comment)*
45	; Comment <- '#' (!EndOfLine .)* EndOfLine
46	; Space <- ' ' / '\t' / EndOfLine
47	; EndOfLine <- '\r\n' / '\n' / '\r'
48	; EndOfFile <- !.
49
50	;;;
51	;;; S-exp PEG Grammar
52	;;;
53	;
54	;; Hierarchical syntax
55	;
56	; Definition <- Identifier LEFTARROW Expression
57	;
58	; Expression <- Sequence (SLASH Sequence)*
59	; Sequence <- Prefix* (RETURN .)?
60	; Prefix <- IdentifierClause / (AND / NOT)? Suffix
61	; Suffix <- Primary (QUESTION / STAR / PLUS)?
62	; IdentifierClause <- OPEN CaptureName Primary CLOSE
63	; Primary <- Identifier !LEFTARROW
64	; / OPEN Expression CLOSE
65	; / Literal / Class / ANY
66	;
67	;; Lexical syntax
68	;
69	; Identifier <- !NonIdentifier <scheme-symbol>
70	; NonIdentifier <- OPEN / CLOSE
71	; CaptureName <- <scheme-keyword>
72	; Literal <- <scheme-string> / <scheme-char>
73	; Class <- <scheme-char-set>
74	;
75	; OPEN <- \|<\|
76	; CLOSE <- \|>\|
77	; LEFTARROW <- \|<-\|
78	; SLASH <- \|/\|
79	; AND <- \|&\|
80	; NOT <- \|!\|
81	; QUESTION <- \|?\|
82	; STAR <- \|*\|
83	; PLUS <- \|+\|
84	; RETURN <- :return
85	; ANY <- \|%any%\|
86
87	; (define-parser math-exp
88	; (additive <- (multitive left-val) #\+ (additive right-val)
89	; &return (+ left-val right-val)
90	; / multitive)
91	; (multitive <- (primary left-val) #\* (multitive right-val)
92	; &return (* left-val right-val)
93	; / primary)
94	; (primary <- #$ (additive val) #$ &return val
95	; / decimal)
96	; (decimal <- (#[0-9] num-char)
97	; &return (- (char->integer num-char) (char->integer #\0))))
98
99	(use peg)
100	(use util.match)
101
102	(define (main args)
103	0)
104
105	(define nil ())
106
107	(define-class <derivs> ()
108	(; Hierarchical tokens (non-terminals)
109	(grammar :init-keyword :grammar)
110	(definition :init-keyword :definition)
111	(expression :init-keyword :expression)
112	(sequence :init-keyword :sequence)
113	(prefix :init-keyword :prefix)
114	(suffix :init-keyword :suffix)
115	(identifier-clause :init-keyword :identifier-clause)
116	(primary :init-keyword :primary)
117
118	; Lexical tokens (terminals)
119	(identifier :init-keyword :identifier)
120	(non-identifier :init-keyword :non-identifier)
121	(capture-name :init-keyword :capture-name)
122	(literal :init-keyword :literal)
123	(class :init-keyword :class)
124
125	(open :init-keyword :open)
126	(close :init-keyword :close)
127	(leftarrow :init-keyword :leftarrow)
128	(return :init-keyword :return)
129	(any :init-keyword :any)
130	(plus :init-keyword :plus)
131	(star :init-keyword :star)
132	(question :init-keyword :question)
133	(not :init-keyword :not)
134	(and :init-keyword :and)
135	(slash :init-keyword :slash)
136
137	; Raw input
138	(token :init-keyword :token :getter deriv-token)
139	))
140
141	(define-macro (define-deriv name)
142	`(define-method ,(string->symbol
143	(string-append "deriv-" (symbol->string name)))
144	((derivs <derivs>))
145	(let1 slt (slot-ref derivs ',name)
146	(if (promise? slt)
147	(let1 forced (force slt)
148	(slot-set! derivs ',name forced)
149	forced)
150	slt))))
151
152	(define-macro (define-derivs . names)
153	`(begin
154	,@(map
155	(lambda (deriv-name)
156	`(define-deriv ,deriv-name))
157	names)))
158
159	(define-derivs ; define generic function *-deriv
160	; for hierarchical syntax
161	grammar definition expression sequence prefix suffix primary identifier-clause
162	; for lexical tokens
163	identifier non-identifier capture-name literal class
164	open close leftarrow slash and not question star plus return any)
165
166	(define (make-result val chars)
167	`(:result ,val ,chars))
168
169	(define (parse tokens)
170	(let loop((ret-deriv nil) (tokens (cons nil (reverse tokens))))
171	(if (null? tokens)
172	ret-deriv
173	(loop
174	(letrec
175	((deriv
176	(make <derivs>
177	; code for generating code
178	; (for-each (lambda (ident) (format #t ":~a (lazy (parse-~a deriv))\n" ident ident)) '(leftarrow slash and not question star plus any))
179
180	; hierarychical syntax
181	:grammar (lazy (parse-grammar deriv))
182	:definition (lazy (parse-definition deriv))
183	:expression (lazy (parse-expression deriv))
184	:sequence (lazy (parse-sequence deriv))
185	:prefix (lazy (parse-prefix deriv))
186	:suffix (lazy (parse-suffix deriv))
187	:identifier-clause (lazy (parse-identifier-clause deriv))
188	:primary (lazy (parse-primary deriv))
189
190	; lexical syntax
191	:identifier (lazy (parse-identifier deriv))
192	:non-identifier (lazy (parse-non-identifier deriv))
193	:capture-name (lazy (parse-capture-name deriv))
194	:literal (lazy (parse-literal deriv))
195	:class (lazy (parse-class deriv))
196
197	:open (lazy (parse-open deriv))
198	:close (lazy (parse-close deriv))
199	:leftarrow (lazy (parse-leftarrow deriv))
200	:slash (lazy (parse-slash deriv))
201	:and (lazy (parse-and deriv))
202	:not (lazy (parse-not deriv))
203	:question (lazy (parse-question deriv))
204	:star (lazy (parse-star deriv))
205	:plus (lazy (parse-plus deriv))
206	:return (lazy (parse-return deriv))
207	:any (lazy (parse-any deriv))
208
209	;raw input
210	:token (if (null? tokens)
211	nil
212	(make-result (car tokens) ret-deriv)))))
213	deriv)
214	(cdr tokens)))))
215
216	(define (parse-grammars pegs)
217	(map
218	(lambda (gram)
219	(let1 gram (flatten-grammar gram)
220	(let* ((ret (deriv-definition (parse gram)))
221	(derivs (caddr (deriv-token (caddr ret)))))
222	(if (not (null? derivs))
223	(error (format #f "Syntax error: ~a" gram))
224	(cadr ret)))))
225	pegs))
226
227
228	;;;
229	;;; Preprocessor of grammar input
230	;;;
231	;;; input:
232	;;; '(foo -> (e1 bar) (e2 baz) :return (do 'sth) / (e3 hoge) :return (do 'anth))
233	;;;
234	;;; output:
235	;;; '(foo -> < e1 bar > < e2 baz > :return (do 'sth) / < e3 hoge > :return (do 'anth))
236	;;;
237	(define (flatten-grammar gram)
238	(let loop((ret nil) (gram (reverse gram)) (expression? #f))
239	(if (null? gram)
240	ret
241	(loop
242	(if (and expression?
243	(list? (car gram)))
244	(append `(< ,@(car gram) >) ret)
245	(cons (car gram) ret))
246	(cdr gram)
247	(cond
248	((eq? '/ (car gram)) #f)
249	((eq? :return (car gram)) #t)
250	(else expression?))))))
251
252	(define (flatten-grammar gram)
253	(concat-with
254	'/
255	(map
256	(lambda (sequence)
257	(concat-with
258	:return
259	(let1 seq-pair (separate (cut eq? :return <>) sequence)
260	`(,(apply append
261	(map (lambda (elem)
262	(if (pair? elem)
263	`(< ,@(flatten-grammar elem) >)
264	`(,elem)))
265	(car seq-pair)))
266	,@(cdr seq-pair)))))
267	(separate (cut eq? '/ <>) gram))))
268
269	(define (separate separator? ls)
270	(let loop1((ret ()) (lst ls))
271	(if (null? lst)
272	(if (separator? (car (reverse ls)))
273	(reverse (cons () ret))
274	(reverse ret))
275	(receive (head tails)
276	(let loop2((ret ()) (ls lst))
277	(cond
278	((null? ls) (values (reverse ret) ls))
279	((separator? (car ls))
280	(values (reverse ret) (cdr ls)))
281	(else
282	(loop2 (cons (car ls) ret) (cdr ls)))))
283	(loop1 (cons head ret)
284	tails)))))
285
286	(define (concat-with joiner ls)
287	(let loop((ret (car (reverse ls))) (ls (cdr (reverse ls))))
288	(if (null? ls)
289	ret
290	(loop `(,@(car ls) ,joiner ,@ret) (cdr ls)))))
291
292	(define-macro (parse-string-with grammars str)
293	`(let ()
294	,@(map translate-definition
295	(parse-grammars grammars))
296	(parse-string ,(caar grammars) ,str)))
297
298
299	(define-macro (define-parse-symbol ident sym)
300	`(define (,(string->symbol (string-append "parse-" (symbol->string ident))) derivs)
301	(match (deriv-token derivs)
302	((:result ',sym derivs-) (make-result ',sym derivs-))
303	(_ nil))))
304
305
306	(define-parse-symbol open <)
307	(define-parse-symbol close >)
308	(define-parse-symbol leftarrow <-)
309	(define-parse-symbol slash /)
310	(define-parse-symbol and &)
311	(define-parse-symbol not !)
312	(define-parse-symbol question ?)
313	(define-parse-symbol star *)
314	(define-parse-symbol plus +)
315	(define-parse-symbol return :return)
316	(define-parse-symbol any %any%)
317
318	(define (parse-class derivs)
319	(match (deriv-token derivs)
320	((:result val derivs-)
321	(if (char-set? val)
322	(make-result `(:char-set ,val) derivs-)
323	nil))
324	(_ nil)))
325
326	(define (parse-literal derivs)
327	(match (deriv-token derivs)
328	((:result val derivs-)
329	(cond
330	((string? val) (make-result `(:string ,val) derivs-))
331	((char? val) (make-result `(:char ,val) derivs-))
332	(else nil)))
333	(_ nil)))
334
335	(define (parse-capture-name derivs)
336	(match (deriv-token derivs)
337	((:result val derivs-)
338	(if (keyword? val)
339	(make-result val derivs-)
340	nil))
341	(_ nil)))
342
343	(define (parse-non-identifier derivs)
344	(let* ((alt3
345	(lazy
346	(match (deriv-slash derivs)
347	((:result ret derivs-)
348	(make-result '/ derivs-))
349	(_ nil))))
350	(alt2
351	(lazy
352	(match (deriv-close derivs)
353	((:result ret derivs-)
354	(make-result '> derivs-))
355	(_ alt3))))
356	(alt1
357	(lazy
358	(match (deriv-open derivs)
359	((:result ret derivs-)
360	(make-result '< derivs-))
361	(_ alt2)))))
362	(force alt1)))
363
364	(define (parse-identifier derivs)
365	(match (deriv-non-identifier derivs)
366	(()
367	(match (deriv-token derivs)
368	((:result val derivs-)
369	(if (symbol? val)
370	(make-result `(:identifier ,val) derivs-)
371	nil))
372	(_ nil)))
373	(_ nil)))
374
375	(define (parse-primary derivs)
376	(let* ((alt6
377	(lazy
378	(match (deriv-any derivs)
379	((:result val derivs-)
380	(make-result val derivs-))
381	(_ nil))))
382	(alt5
383	(lazy
384	(match (deriv-class derivs)
385	((:result val derivs-)
386	(make-result val derivs-))
387	(_ alt6))))
388	(alt4
389	(lazy
390	(match (deriv-literal derivs)
391	((:result val derivs-)
392	(make-result val derivs-))
393	(_ alt5))))
394	(alt3
395	(lazy
396	(match (deriv-open derivs)
397	((:result val derivs-)
398	(match (deriv-expression derivs-)
399	((:result exp derivs--)
400	(match (deriv-close derivs--)
401	((:result val derivs---)
402	(make-result exp derivs---))
403	(_ alt4)))
404	(_ alt4)))
405	(_ alt4))))
406	(alt1
407	(lazy
408	(match (deriv-identifier derivs)
409	((:result ident derivs-)
410	(match (deriv-leftarrow derivs-)
411	((:result val derivs--) alt3)
412	(_ (make-result ident derivs-))))
413	(_ alt3)))))
414	(force alt1)))
415
416	(define (parse-identifier-clause derivs)
417	(let* ((alt1
418	(lazy
419	(match (deriv-open derivs)
420	((:result opn derivs-)
421	(match (deriv-capture-name derivs-)
422	((:result capt derivs--)
423	(match (deriv-primary derivs--)
424	((:result primary derivs---)
425	(match (deriv-close derivs---)
426	((:result cls derivs----)
427	(make-result `(:identifier-clause
428	,primary
429	:capture
430	,(string->symbol (x->string capt)))
431	derivs----))
432	(_ nil)))
433	(_ nil)))
434	(_ nil)))
435	(_ nil)))))
436	(force alt1)))
437
438	(define (parse-suffix derivs)
439	(match (deriv-primary derivs)
440	((:result prim derivs-)
441	(let* ((alt3
442	(lazy
443	(match (deriv-plus derivs-)
444	((:result plus derivs--)
445	(make-result `(:one-more ,prim) derivs--))
446	(_ (make-result prim derivs-)))))
447	(alt2
448	(lazy
449	(match (deriv-star derivs-)
450	((:result star derivs--)
451	(make-result `(:zero-more ,prim) derivs--))
452	(_ alt3))))
453	(alt1
454	(lazy
455	(match (deriv-question derivs-)
456	((:result qstn derivs--)
457	(make-result `(:optional ,prim) derivs--))
458	(_ alt2)))))
459	(force alt1)))
460	(_ nil)))
461
462	(define (parse-prefix derivs)
463	(let* ((glob-alt2
464	(lazy
465	(let* ((alt2
466	(lazy
467	(match (deriv-not derivs)
468	((:result val derivs-)
469	(values :not derivs-))
470	(_ (values nil derivs)))))
471	(alt1
472	(lazy
473	(match (deriv-and derivs)
474	((:result val derivs-)
475	(values :and derivs-))
476	(_ alt2)))))
477	(receive (val derivs-) (force alt1)
478	(match (deriv-suffix derivs-)
479	((:result suffix derivs--)
480	(if (null? val)
481	(make-result suffix derivs--)
482	(make-result `(,val ,suffix) derivs--)))
483	(_ nil))))))
484	(glob-alt1
485	(lazy
486	(match (deriv-identifier-clause derivs)
487	((:result ident-clause derivs-)
488	(make-result ident-clause derivs-))
489	(_ glob-alt2)))))
490	(force glob-alt1)))
491
492	(define (parse-sequence derivs)
493	(receive (seqs derivs)
494	(let loop((ret ()) (derivs derivs))
495	(match (deriv-prefix derivs)
496	((:result val derivs-)
497	(loop (cons val ret) derivs-))
498	(_ (values (reverse ret) derivs))))
499	(let* ((alt2
500	(lazy
501	(make-result `(:sequence ,seqs :callback ()) derivs)))
502	(alt1
503	(lazy
504	(match (deriv-return derivs)
505	((:result val derivs-)
506	(match (deriv-token derivs-)
507	((:result callback derivs--)
508	(make-result `(:sequence ,seqs :callback ,callback) derivs--))
509	(_ alt2)))
510	(_ alt2)))))
511	(force alt1))))
512
513	(define (parse-expression derivs)
514	(match (deriv-sequence derivs)
515	((:result seq derivs-)
516	(receive (ret derivs)
517	(let loop((ret `(,seq)) (derivs derivs-))
518	(match (deriv-slash derivs)
519	((:result sla derivs-)
520	(match (deriv-sequence derivs-)
521	((:result seq derivs--)
522	(loop (cons seq ret) derivs--))
523	(_ (values (reverse ret) derivs))))
524	(_ (values (reverse ret) derivs))))
525	(make-result (if (null? (cdr ret))
526	(car ret)
527	(cons :expression ret))
528	derivs)))))
529
530	(define (parse-definition derivs)
531	(match (deriv-identifier derivs)
532	((:result ident derivs-)
533	(match (deriv-leftarrow derivs-)
534	((:result larr derivs--)
535	(match (deriv-expression derivs--)
536	((:result expr derivs---)
537	(make-result `(:definition ,ident ,expr) derivs---))
538	(_ nil)))
539	(_ nil)))
540	(_ nil)))
541
542	;;;
543	;;; AST translation to PEG
544	;;;
545	;;; ref. WiLiKi:Rui:ParsingExpressionGrammar
546	;;;
547
548	;;
549	;; expected input
550	;; * identifier
551	;; (:identifier <symbol>)
552	;; * identifier-clause
553	;; (:identifier-clause (:identifier <symbol>) :capture <symbol>)
554	;; * char(literal)
555	;; (:char <char>)
556	;; * string(literal)
557	;; (:string <string>)
558	;; * char-set(class)
559	;; (:char-set <char-set>)
560	;; * expression
561	;; (:expression (:sequence (...) :callback ...) ...)
562	;;
563	;; return (values <parser> <captured-name>)
564	;;
565	(define (translate-primary primary)
566	(let ((tag (car primary))
567	(value (cadr primary)))
568	(case tag
569	((:identifier) value)
570	((:char) `($char ,value))
571	((:string) `($string ,value))
572	((:char-set) `($one-of ,value))
573	((:sequence) (translate-sequence primary))
574	((:expression) (translate-expression primary)))))
575
576	;;
577	;; expected input
578	;; * more than zero
579	;; (:zero-more <primary>)
580	;; * more than one
581	;; (:one-more <primary>)
582	;; * primary
583	;; <primary> (see translate-primary)
584	;;
585	;; return (values <parser> <captured-name>)
586	;;
587	(define (translate-suffix suffix)
588	(let ((tag (car suffix))
589	(value (cadr suffix)))
590	(case tag
591	((:zero-more) `($many ,(translate-primary value)))
592	((:one-more) `($many ,(translate-primary value) 1))
593	((:optional) `($optional ,(translate-primary value)))
594	(else (translate-primary suffix)))))
595
596	;;
597	;; expected input
598	;; * and(syntactic predicate)
599	;; (:and <suffix>)
600	;; * not(syntactic predicate)
601	;; (:not <suffix>)
602	;; * suffix
603	;; <suffix> (see translate-suffix)
604	;;
605	;; return (values <parser> <ident-clause?>)
606	;;
607	(define (translate-prefix prefix)
608	(let ((tag (car prefix))
609	(value (cadr prefix)))
610	(case tag
611	((:not) (values `($not ,(translate-suffix value)) #f))
612	((:identifier-clause)
613	(values `(,(get-keyword :capture prefix)
614	,(translate-primary value))
615	#t))
616	(else (values (translate-suffix prefix) #f)))))
617
618	(define (translate-sequence sequence)
619	(let ((tag (car sequence))
620	(prefixes (cadr sequence))
621	(callback (get-keyword :callback sequence #f)))
622	(case tag
623	((:sequence)
624	(if (null? prefixes)
625	`($do ($return ,callback))
626	(if
627	(and (null? (cdr prefixes)) (null? callback))
628	(translate-prefix (car prefixes))
629	(let loop((items nil) (capture-names nil) (prefixes prefixes))
630	(cond
631	((null? prefixes)
632	(cons
633	'$do
634	(reverse
635	(cons
636	(if (null? callback)
637	`($return (list ,@(reverse capture-names)))
638	`($return ,callback))
639	items))))
640	(else
641	(receive (prefix ident-clause?)
642	(translate-prefix (car prefixes))
643	(let1 capt (gensym)
644	(loop (cons (if ident-clause?
645	prefix
646	`(,capt ,prefix))
647	items)
648	(cons (if ident-clause?
649	(car prefix)
650	capt)
651	capture-names)
652	(cdr prefixes)
653	)))))))))
654	(else
655	(translate-prefix sequence)))))
656
657	(define (translate-expression expression)
658	(let ((tag (car expression)))
659	(case tag
660	((:expression)
661	(let1 sequences (cdr expression)
662	(if (null? (cdr sequences))
663	(translate-sequence (car sequences))
664	`($or ,@(map translate-sequence sequences)))))
665	(else
666	(translate-sequence expression)))))
667
668	(define (translate-definition definition)
669	(let ((tag (car definition))
670	(ident (cadr (cadr definition)))
671	(expression (caddr definition)))
672	(case tag
673	((:definition)
674	`(define ,ident ,(translate-expression expression)))
675	(else (error "Translation error")))))
676
677	(define (hoge)
678	(let* ((spaces ($many ($one-of #[ \t])))
679	(comma ($seq spaces ($char #\,) spaces))
680	(dquote ($char #\"))
681	(double-dquote ($do (($string "\"\"")) ($return #\")))
682	(quoted-body ($many ($or double-dquote ($one-of #[^\"]))))
683	(quoted ($between dquote quoted-body dquote))
684	(unquoted ($many-till anychar ($or comma newline)))
685	(field ($or quoted unquoted))
686	(record ($sep-by ($->rope field) comma)))
687	#?=(parse-string record "a,b,c")
688	#?=(parse-string record "\"a\" , b , c")
689	#?=(parse-string record "\"a \"\" \n\" , b , c"))
690
691	(parse-string-with
692	((Record <- (:fld Field) (:suffix RecordSuffix) :return (cons fld suffix))
693	(RecordSuffix <- Comma (:fld Field) (:suffix RecordSuffix)
694	:return (cons fld suffix)
695	/ :return () )
696	(Field <- (:charlist Quoted) :return (list->string charlist)
697	/ (:charlist UnQuoted) :return (list->string charlist))
698	(Spaces <- #[ \t] *)
699	(Comma <- Spaces #\, Spaces)
700	(DQuote <- #\")
701	(DoubleDQuote <- #\" #\" :return #\")
702	(Quoted <- DQuote
703	(:body ((DoubleDQuote / #[^\"]) *))
704	DQuote
705	:return body)
706	(UnQuoted <- ((! (Comma / newline) (:ch anychar) :return ch) *))
707	)
708	"\"a\" , b , c")
709	)
710
711	;; (parse-string-with
712	;; ((Record <- (:fld Field)
713	;; (:rest-fld ((Comma (:fld Field) :return fld) *))
714	;; :return (cons fld rest-fld))
715	;; (Field <- (:charlist Quoted) :return (list->string charlist)
716	;; / (:charlist UnQuoted) :return (list->string charlist))
717	;; (Spaces <- #[ \t] *)
718	;; (Comma <- Spaces #\, Spaces)
719	;; (DQuote <- #\")
720	;; (Quoted <- DQuote
721	;; (:body ((#\" #\" :return #\" / #[^\"]) *))
722	;; DQuote
723	;; :return body)
724	;; (UnQuoted <- ! (Comma / newline) (:ch anychar) (:unq UnQuoted)
725	;; :return (cons ch unq)
726	;; / :return ())
727	;; )
728	;; "\"a\"\"bc\" , b , c")
729
730	;; (parse-string-with
731	;; ((A <- "a" A "a" / "a"))
732	;; "aaaaa")

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