1pt::peg::to::param(n) Parser Tools pt::peg::to::param(n)
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6
8 pt::peg::to::param - PEG Conversion. Write PARAM format
9
11 package require Tcl 8.5
12 package require pt::peg::to::param ?1?
14 package require pt::peg
16 package require pt::pe
18 pt::peg::to::param reset
20 pt::peg::to::param configure
22 pt::peg::to::param configure option
24 pt::peg::to::param configure option value...
26 pt::peg::to::param convert serial
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30
32 Are you lost ? Do you have trouble understanding this document ? In
33 that case please read the overview provided by the Introduction to
34 Parser Tools. This document is the entrypoint to the whole system the
35 current package is a part of.
36 This package implements the converter from parsing expression grammars
38 to PARAM markup.
39 It resides in the Export section of the Core Layer of Parser Tools, and
41 can be used either directly with the other packages of this layer, or
42 indirectly through the export manager provided by pt::peg::export. The
43 latter is intented for use in untrusted environments and done through
44 the corresponding export plugin pt::peg::export::param sitting between
45 converter and export manager.
46 IMAGE: arch_core_eplugins
48
50 The API provided by this package satisfies the specification of the
51 Converter API found in the Parser Tools Export API specification.
52 pt::peg::to::param reset
54 This command resets the configuration of the package to its
55 default settings.
56 pt::peg::to::param configure
58 This command returns a dictionary containing the current config‐
59 uration of the package.
60 pt::peg::to::param configure option
62 This command returns the current value of the specified configu‐
63 ration option of the package. For the set of legal options,
64 please read the section Options.
65 pt::peg::to::param configure option value...
67 This command sets the given configuration options of the pack‐
68 age, to the specified values. For the set of legal options,
69 please read the section Options.
70 pt::peg::to::param convert serial
72 This command takes the canonical serialization of a parsing
73 expression grammar, as specified in section PEG serialization
74 format, and contained in serial, and generates PARAM markup
75 encoding the grammar, per the current package configuration.
76 The created string is then returned as the result of the com‐
77 mand.
78
80 The converter to PARAM markup recognizes the following configuration
81 variables and changes its behaviour as they specify.
82 -template string
84 The value of this configuration variable is a string into which
85 to put the generated text and the other configuration settings.
86 The various locations for user-data are expected to be specified
87 with the placeholders listed below. The default value is
88 "@code@".
89 @user@ To be replaced with the value of the configuration vari‐
91 able -user.
92 @format@
94 To be replaced with the the constant PARAM.
95 @file@ To be replaced with the value of the configuration vari‐
97 able -file.
98 @name@ To be replaced with the value of the configuration vari‐
100 able -name.
101 @code@ To be replaced with the generated text.
103 -name string
105 The value of this configuration variable is the name of the
106 grammar for which the conversion is run. The default value is
107 a_pe_grammar.
108 -user string
110 The value of this configuration variable is the name of the user
111 for which the conversion is run. The default value is unknown.
112 -file string
114 The value of this configuration variable is the name of the file
115 or other entity from which the grammar came, for which the con‐
116 version is run. The default value is unknown.
117
119 The PARAM code representation of parsing expression grammars is assem‐
120 bler-like text using the instructions of the virtual machine documented
121 in the PackRat Machine Specification, plus a few more for control flow
122 (jump ok, jump fail, call symbol, return).
123 It is not really useful, except possibly as a tool demonstrating how a
125 grammar is compiled in general, without getting distracted by the inci‐
126 dentials of a framework, i.e. like the supporting C and Tcl code gener‐
127 ated by the other PARAM-derived formats.
128 It has no direct formal specification beyond what was said above.
130 EXAMPLE
132 Assuming the following PEG for simple mathematical expressions
133 PEG calculator (Expression)
135 Digit <- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9' ;
136 Sign <- '-' / '+' ;
137 Number <- Sign? Digit+ ;
138 Expression <- Term (AddOp Term)* ;
139 MulOp <- '*' / '/' ;
140 Term <- Factor (MulOp Factor)* ;
141 AddOp <- '+'/'-' ;
142 Factor <- '(' Expression ')' / Number ;
143 END;
144 one possible PARAM serialization for it is
147 # -*- text -*-
149 # Parsing Expression Grammar 'TEMPLATE'.
150 # Generated for unknown, from file 'TEST'
151 #
153 # Grammar Start Expression
154 #
155 <<MAIN>>:
157 call sym_Expression
158 halt
159 #
161 # value Symbol 'AddOp'
162 #
163 sym_AddOp:
165 # /
166 # '-'
167 # '+'
168 symbol_restore AddOp
170 found! jump found_7
171 loc_push
172 call choice_5
174 fail! value_clear
176 ok! value_leaf AddOp
177 symbol_save AddOp
178 error_nonterminal AddOp
179 loc_pop_discard
180 found_7:
182 ok! ast_value_push
183 return
184 choice_5:
186 # /
187 # '-'
188 # '+'
189 error_clear
191 loc_push
193 error_push
194 input_next "t -"
196 ok! test_char "-"
197 error_pop_merge
199 ok! jump oknoast_4
200 loc_pop_rewind
202 loc_push
203 error_push
204 input_next "t +"
206 ok! test_char "+"
207 error_pop_merge
209 ok! jump oknoast_4
210 loc_pop_rewind
212 status_fail
213 return
214 oknoast_4:
216 loc_pop_discard
217 return
218 #
219 # value Symbol 'Digit'
220 #
221 sym_Digit:
223 # /
224 # '0'
225 # '1'
226 # '2'
227 # '3'
228 # '4'
229 # '5'
230 # '6'
231 # '7'
232 # '8'
233 # '9'
234 symbol_restore Digit
236 found! jump found_22
237 loc_push
238 call choice_20
240 fail! value_clear
242 ok! value_leaf Digit
243 symbol_save Digit
244 error_nonterminal Digit
245 loc_pop_discard
246 found_22:
248 ok! ast_value_push
249 return
250 choice_20:
252 # /
253 # '0'
254 # '1'
255 # '2'
256 # '3'
257 # '4'
258 # '5'
259 # '6'
260 # '7'
261 # '8'
262 # '9'
263 error_clear
265 loc_push
267 error_push
268 input_next "t 0"
270 ok! test_char "0"
271 error_pop_merge
273 ok! jump oknoast_19
274 loc_pop_rewind
276 loc_push
277 error_push
278 input_next "t 1"
280 ok! test_char "1"
281 error_pop_merge
283 ok! jump oknoast_19
284 loc_pop_rewind
286 loc_push
287 error_push
288 input_next "t 2"
290 ok! test_char "2"
291 error_pop_merge
293 ok! jump oknoast_19
294 loc_pop_rewind
296 loc_push
297 error_push
298 input_next "t 3"
300 ok! test_char "3"
301 error_pop_merge
303 ok! jump oknoast_19
304 loc_pop_rewind
306 loc_push
307 error_push
308 input_next "t 4"
310 ok! test_char "4"
311 error_pop_merge
313 ok! jump oknoast_19
314 loc_pop_rewind
316 loc_push
317 error_push
318 input_next "t 5"
320 ok! test_char "5"
321 error_pop_merge
323 ok! jump oknoast_19
324 loc_pop_rewind
326 loc_push
327 error_push
328 input_next "t 6"
330 ok! test_char "6"
331 error_pop_merge
333 ok! jump oknoast_19
334 loc_pop_rewind
336 loc_push
337 error_push
338 input_next "t 7"
340 ok! test_char "7"
341 error_pop_merge
343 ok! jump oknoast_19
344 loc_pop_rewind
346 loc_push
347 error_push
348 input_next "t 8"
350 ok! test_char "8"
351 error_pop_merge
353 ok! jump oknoast_19
354 loc_pop_rewind
356 loc_push
357 error_push
358 input_next "t 9"
360 ok! test_char "9"
361 error_pop_merge
363 ok! jump oknoast_19
364 loc_pop_rewind
366 status_fail
367 return
368 oknoast_19:
370 loc_pop_discard
371 return
372 #
373 # value Symbol 'Expression'
374 #
375 sym_Expression:
377 # /
378 # x
379 # '\('
380 # (Expression)
381 # '\)'
382 # x
383 # (Factor)
384 # *
385 # x
386 # (MulOp)
387 # (Factor)
388 symbol_restore Expression
390 found! jump found_46
391 loc_push
392 ast_push
393 call choice_44
395 fail! value_clear
397 ok! value_reduce Expression
398 symbol_save Expression
399 error_nonterminal Expression
400 ast_pop_rewind
401 loc_pop_discard
402 found_46:
404 ok! ast_value_push
405 return
406 choice_44:
408 # /
409 # x
410 # '\('
411 # (Expression)
412 # '\)'
413 # x
414 # (Factor)
415 # *
416 # x
417 # (MulOp)
418 # (Factor)
419 error_clear
421 ast_push
423 loc_push
424 error_push
425 call sequence_27
427 error_pop_merge
429 ok! jump ok_43
430 ast_pop_rewind
432 loc_pop_rewind
433 ast_push
434 loc_push
435 error_push
436 call sequence_40
438 error_pop_merge
440 ok! jump ok_43
441 ast_pop_rewind
443 loc_pop_rewind
444 status_fail
445 return
446 ok_43:
448 ast_pop_discard
449 loc_pop_discard
450 return
451 sequence_27:
453 # x
454 # '\('
455 # (Expression)
456 # '\)'
457 loc_push
459 error_clear
460 error_push
462 input_next "t ("
464 ok! test_char "("
465 error_pop_merge
467 fail! jump failednoast_29
468 ast_push
469 error_push
470 call sym_Expression
472 error_pop_merge
474 fail! jump failed_28
475 error_push
476 input_next "t )"
478 ok! test_char ")"
479 error_pop_merge
481 fail! jump failed_28
482 ast_pop_discard
484 loc_pop_discard
485 return
486 failed_28:
488 ast_pop_rewind
489 failednoast_29:
491 loc_pop_rewind
492 return
493 sequence_40:
495 # x
496 # (Factor)
497 # *
498 # x
499 # (MulOp)
500 # (Factor)
501 ast_push
503 loc_push
504 error_clear
505 error_push
507 call sym_Factor
509 error_pop_merge
511 fail! jump failed_41
512 error_push
513 call kleene_37
515 error_pop_merge
517 fail! jump failed_41
518 ast_pop_discard
520 loc_pop_discard
521 return
522 failed_41:
524 ast_pop_rewind
525 loc_pop_rewind
526 return
527 kleene_37:
529 # *
530 # x
531 # (MulOp)
532 # (Factor)
533 loc_push
535 error_push
536 call sequence_34
538 error_pop_merge
540 fail! jump failed_38
541 loc_pop_discard
542 jump kleene_37
543 failed_38:
545 loc_pop_rewind
546 status_ok
547 return
548 sequence_34:
550 # x
551 # (MulOp)
552 # (Factor)
553 ast_push
555 loc_push
556 error_clear
557 error_push
559 call sym_MulOp
561 error_pop_merge
563 fail! jump failed_35
564 error_push
565 call sym_Factor
567 error_pop_merge
569 fail! jump failed_35
570 ast_pop_discard
572 loc_pop_discard
573 return
574 failed_35:
576 ast_pop_rewind
577 loc_pop_rewind
578 return
579 #
580 # value Symbol 'Factor'
581 #
582 sym_Factor:
584 # x
585 # (Term)
586 # *
587 # x
588 # (AddOp)
589 # (Term)
590 symbol_restore Factor
592 found! jump found_60
593 loc_push
594 ast_push
595 call sequence_57
597 fail! value_clear
599 ok! value_reduce Factor
600 symbol_save Factor
601 error_nonterminal Factor
602 ast_pop_rewind
603 loc_pop_discard
604 found_60:
606 ok! ast_value_push
607 return
608 sequence_57:
610 # x
611 # (Term)
612 # *
613 # x
614 # (AddOp)
615 # (Term)
616 ast_push
618 loc_push
619 error_clear
620 error_push
622 call sym_Term
624 error_pop_merge
626 fail! jump failed_58
627 error_push
628 call kleene_54
630 error_pop_merge
632 fail! jump failed_58
633 ast_pop_discard
635 loc_pop_discard
636 return
637 failed_58:
639 ast_pop_rewind
640 loc_pop_rewind
641 return
642 kleene_54:
644 # *
645 # x
646 # (AddOp)
647 # (Term)
648 loc_push
650 error_push
651 call sequence_51
653 error_pop_merge
655 fail! jump failed_55
656 loc_pop_discard
657 jump kleene_54
658 failed_55:
660 loc_pop_rewind
661 status_ok
662 return
663 sequence_51:
665 # x
666 # (AddOp)
667 # (Term)
668 ast_push
670 loc_push
671 error_clear
672 error_push
674 call sym_AddOp
676 error_pop_merge
678 fail! jump failed_52
679 error_push
680 call sym_Term
682 error_pop_merge
684 fail! jump failed_52
685 ast_pop_discard
687 loc_pop_discard
688 return
689 failed_52:
691 ast_pop_rewind
692 loc_pop_rewind
693 return
694 #
695 # value Symbol 'MulOp'
696 #
697 sym_MulOp:
699 # /
700 # '*'
701 # '/'
702 symbol_restore MulOp
704 found! jump found_67
705 loc_push
706 call choice_65
708 fail! value_clear
710 ok! value_leaf MulOp
711 symbol_save MulOp
712 error_nonterminal MulOp
713 loc_pop_discard
714 found_67:
716 ok! ast_value_push
717 return
718 choice_65:
720 # /
721 # '*'
722 # '/'
723 error_clear
725 loc_push
727 error_push
728 input_next "t *"
730 ok! test_char "*"
731 error_pop_merge
733 ok! jump oknoast_64
734 loc_pop_rewind
736 loc_push
737 error_push
738 input_next "t /"
740 ok! test_char "/"
741 error_pop_merge
743 ok! jump oknoast_64
744 loc_pop_rewind
746 status_fail
747 return
748 oknoast_64:
750 loc_pop_discard
751 return
752 #
753 # value Symbol 'Number'
754 #
755 sym_Number:
757 # x
758 # ?
759 # (Sign)
760 # +
761 # (Digit)
762 symbol_restore Number
764 found! jump found_80
765 loc_push
766 ast_push
767 call sequence_77
769 fail! value_clear
771 ok! value_reduce Number
772 symbol_save Number
773 error_nonterminal Number
774 ast_pop_rewind
775 loc_pop_discard
776 found_80:
778 ok! ast_value_push
779 return
780 sequence_77:
782 # x
783 # ?
784 # (Sign)
785 # +
786 # (Digit)
787 ast_push
789 loc_push
790 error_clear
791 error_push
793 call optional_70
795 error_pop_merge
797 fail! jump failed_78
798 error_push
799 call poskleene_73
801 error_pop_merge
803 fail! jump failed_78
804 ast_pop_discard
806 loc_pop_discard
807 return
808 failed_78:
810 ast_pop_rewind
811 loc_pop_rewind
812 return
813 optional_70:
815 # ?
816 # (Sign)
817 loc_push
819 error_push
820 call sym_Sign
822 error_pop_merge
824 fail! loc_pop_rewind
825 ok! loc_pop_discard
826 status_ok
827 return
828 poskleene_73:
830 # +
831 # (Digit)
832 loc_push
834 call sym_Digit
836 fail! jump failed_74
838 loop_75:
840 loc_pop_discard
841 loc_push
842 error_push
843 call sym_Digit
845 error_pop_merge
847 ok! jump loop_75
848 status_ok
849 failed_74:
851 loc_pop_rewind
852 return
853 #
854 # value Symbol 'Sign'
855 #
856 sym_Sign:
858 # /
859 # '-'
860 # '+'
861 symbol_restore Sign
863 found! jump found_86
864 loc_push
865 call choice_5
867 fail! value_clear
869 ok! value_leaf Sign
870 symbol_save Sign
871 error_nonterminal Sign
872 loc_pop_discard
873 found_86:
875 ok! ast_value_push
876 return
877 #
878 # value Symbol 'Term'
879 #
880 sym_Term:
882 # (Number)
883 symbol_restore Term
885 found! jump found_89
886 loc_push
887 ast_push
888 call sym_Number
890 fail! value_clear
892 ok! value_reduce Term
893 symbol_save Term
894 error_nonterminal Term
895 ast_pop_rewind
896 loc_pop_discard
897 found_89:
899 ok! ast_value_push
900 return
901 #
903 #
904
907 Here we specify the format used by the Parser Tools to serialize Pars‐
908 ing Expression Grammars as immutable values for transport, comparison,
909 etc.
910 We distinguish between regular and canonical serializations. While a
912 PEG may have more than one regular serialization only exactly one of
913 them will be canonical.
914 regular serialization
916 [1] The serialization of any PEG is a nested Tcl dictionary.
918 [2] This dictionary holds a single key, pt::grammar::peg, and
920 its value. This value holds the contents of the grammar.
921 [3] The contents of the grammar are a Tcl dictionary holding
923 the set of nonterminal symbols and the starting expres‐
924 sion. The relevant keys and their values are
925 rules The value is a Tcl dictionary whose keys are the
927 names of the nonterminal symbols known to the
928 grammar.
929 [1] Each nonterminal symbol may occur only
931 once.
932 [2] The empty string is not a legal nonterminal
934 symbol.
935 [3] The value for each symbol is a Tcl dictio‐
937 nary itself. The relevant keys and their
938 values in this dictionary are
939 is The value is the serialization of
941 the parsing expression describing
942 the symbols sentennial structure, as
943 specified in the section PE serial‐
944 ization format.
945 mode The value can be one of three values
947 specifying how a parser should han‐
948 dle the semantic value produced by
949 the symbol.
950 value The semantic value of the
952 nonterminal symbol is an
953 abstract syntax tree consist‐
954 ing of a single node node for
955 the nonterminal itself, which
956 has the ASTs of the symbol's
957 right hand side as its chil‐
958 dren.
959 leaf The semantic value of the
961 nonterminal symbol is an
962 abstract syntax tree consist‐
963 ing of a single node node for
964 the nonterminal, without any
965 children. Any ASTs generated
966 by the symbol's right hand
967 side are discarded.
968 void The nonterminal has no seman‐
970 tic value. Any ASTs generated
971 by the symbol's right hand
972 side are discarded (as well).
973 start The value is the serialization of the start pars‐
975 ing expression of the grammar, as specified in the
976 section PE serialization format.
977 [4] The terminal symbols of the grammar are specified implic‐
979 itly as the set of all terminal symbols used in the start
980 expression and on the RHS of the grammar rules.
981 canonical serialization
983 The canonical serialization of a grammar has the format as spec‐
984 ified in the previous item, and then additionally satisfies the
985 constraints below, which make it unique among all the possible
986 serializations of this grammar.
987 [1] The keys found in all the nested Tcl dictionaries are
989 sorted in ascending dictionary order, as generated by
990 Tcl's builtin command lsort -increasing -dict.
991 [2] The string representation of the value is the canonical
993 representation of a Tcl dictionary. I.e. it does not con‐
994 tain superfluous whitespace.
995 EXAMPLE
997 Assuming the following PEG for simple mathematical expressions
998 PEG calculator (Expression)
1000 Digit <- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9' ;
1001 Sign <- '-' / '+' ;
1002 Number <- Sign? Digit+ ;
1003 Expression <- Term (AddOp Term)* ;
1004 MulOp <- '*' / '/' ;
1005 Term <- Factor (MulOp Factor)* ;
1006 AddOp <- '+'/'-' ;
1007 Factor <- '(' Expression ')' / Number ;
1008 END;
1009 then its canonical serialization (except for whitespace) is
1012 pt::grammar::peg {
1014 rules {
1015 AddOp {is {/ {t -} {t +}} mode value}
1016 Digit {is {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}} mode value}
1017 Expression {is {x {n Term} {* {x {n AddOp} {n Term}}}} mode value}
1018 Factor {is {/ {x {t (} {n Expression} {t )}} {n Number}} mode value}
1019 MulOp {is {/ {t *} {t /}} mode value}
1020 Number {is {x {? {n Sign}} {+ {n Digit}}} mode value}
1021 Sign {is {/ {t -} {t +}} mode value}
1022 Term {is {x {n Factor} {* {x {n MulOp} {n Factor}}}} mode value}
1023 }
1024 start {n Expression}
1025 }
1026
1029 Here we specify the format used by the Parser Tools to serialize Pars‐
1030 ing Expressions as immutable values for transport, comparison, etc.
1031 We distinguish between regular and canonical serializations. While a
1033 parsing expression may have more than one regular serialization only
1034 exactly one of them will be canonical.
1035 Regular serialization
1037 Atomic Parsing Expressions
1039 [1] The string epsilon is an atomic parsing expres‐
1041 sion. It matches the empty string.
1042 [2] The string dot is an atomic parsing expression. It
1044 matches any character.
1045 [3] The string alnum is an atomic parsing expression.
1047 It matches any Unicode alphabet or digit charac‐
1048 ter. This is a custom extension of PEs based on
1049 Tcl's builtin command string is.
1050 [4] The string alpha is an atomic parsing expression.
1052 It matches any Unicode alphabet character. This is
1053 a custom extension of PEs based on Tcl's builtin
1054 command string is.
1055 [5] The string ascii is an atomic parsing expression.
1057 It matches any Unicode character below U0080. This
1058 is a custom extension of PEs based on Tcl's
1059 builtin command string is.
1060 [6] The string control is an atomic parsing expres‐
1062 sion. It matches any Unicode control character.
1063 This is a custom extension of PEs based on Tcl's
1064 builtin command string is.
1065 [7] The string digit is an atomic parsing expression.
1067 It matches any Unicode digit character. Note that
1068 this includes characters outside of the [0..9]
1069 range. This is a custom extension of PEs based on
1070 Tcl's builtin command string is.
1071 [8] The string graph is an atomic parsing expression.
1073 It matches any Unicode printing character, except
1074 for space. This is a custom extension of PEs based
1075 on Tcl's builtin command string is.
1076 [9] The string lower is an atomic parsing expression.
1078 It matches any Unicode lower-case alphabet charac‐
1079 ter. This is a custom extension of PEs based on
1080 Tcl's builtin command string is.
1081 [10] The string print is an atomic parsing expression.
1083 It matches any Unicode printing character, includ‐
1084 ing space. This is a custom extension of PEs based
1085 on Tcl's builtin command string is.
1086 [11] The string punct is an atomic parsing expression.
1088 It matches any Unicode punctuation character. This
1089 is a custom extension of PEs based on Tcl's
1090 builtin command string is.
1091 [12] The string space is an atomic parsing expression.
1093 It matches any Unicode space character. This is a
1094 custom extension of PEs based on Tcl's builtin
1095 command string is.
1096 [13] The string upper is an atomic parsing expression.
1098 It matches any Unicode upper-case alphabet charac‐
1099 ter. This is a custom extension of PEs based on
1100 Tcl's builtin command string is.
1101 [14] The string wordchar is an atomic parsing expres‐
1103 sion. It matches any Unicode word character. This
1104 is any alphanumeric character (see alnum), and any
1105 connector punctuation characters (e.g. under‐
1106 score). This is a custom extension of PEs based on
1107 Tcl's builtin command string is.
1108 [15] The string xdigit is an atomic parsing expression.
1110 It matches any hexadecimal digit character. This
1111 is a custom extension of PEs based on Tcl's
1112 builtin command string is.
1113 [16] The string ddigit is an atomic parsing expression.
1115 It matches any decimal digit character. This is a
1116 custom extension of PEs based on Tcl's builtin
1117 command regexp.
1118 [17] The expression [list t x] is an atomic parsing
1120 expression. It matches the terminal string x.
1121 [18] The expression [list n A] is an atomic parsing
1123 expression. It matches the nonterminal A.
1124 Combined Parsing Expressions
1126 [1] For parsing expressions e1, e2, ... the result of
1128 [list / e1 e2 ... ] is a parsing expression as
1129 well. This is the ordered choice, aka prioritized
1130 choice.
1131 [2] For parsing expressions e1, e2, ... the result of
1133 [list x e1 e2 ... ] is a parsing expression as
1134 well. This is the sequence.
1135 [3] For a parsing expression e the result of [list *
1137 e] is a parsing expression as well. This is the
1138 kleene closure, describing zero or more repeti‐
1139 tions.
1140 [4] For a parsing expression e the result of [list +
1142 e] is a parsing expression as well. This is the
1143 positive kleene closure, describing one or more
1144 repetitions.
1145 [5] For a parsing expression e the result of [list &
1147 e] is a parsing expression as well. This is the
1148 and lookahead predicate.
1149 [6] For a parsing expression e the result of [list !
1151 e] is a parsing expression as well. This is the
1152 not lookahead predicate.
1153 [7] For a parsing expression e the result of [list ?
1155 e] is a parsing expression as well. This is the
1156 optional input.
1157 Canonical serialization
1159 The canonical serialization of a parsing expression has the for‐
1160 mat as specified in the previous item, and then additionally
1161 satisfies the constraints below, which make it unique among all
1162 the possible serializations of this parsing expression.
1163 [1] The string representation of the value is the canonical
1165 representation of a pure Tcl list. I.e. it does not con‐
1166 tain superfluous whitespace.
1167 [2] Terminals are not encoded as ranges (where start and end
1169 of the range are identical).
1170 EXAMPLE
1172 Assuming the parsing expression shown on the right-hand side of the
1173 rule
1174 Expression <- Term (AddOp Term)*
1176 then its canonical serialization (except for whitespace) is
1179 {x {n Term} {* {x {n AddOp} {n Term}}}}
1181
1184 This document, and the package it describes, will undoubtedly contain
1185 bugs and other problems. Please report such in the category pt of the
1186 Tcllib Trackers [http://core.tcl.tk/tcllib/reportlist]. Please also
1187 report any ideas for enhancements you may have for either package
1188 and/or documentation.
1189 When proposing code changes, please provide unified diffs, i.e the out‐
1191 put of diff -u.
1192 Note further that attachments are strongly preferred over inlined
1194 patches. Attachments can be made by going to the Edit form of the
1195 ticket immediately after its creation, and then using the left-most
1196 button in the secondary navigation bar.
1197
1199 EBNF, LL(k), PARAM, PEG, TDPL, context-free languages, conversion,
1200 expression, format conversion, grammar, matching, parser, parsing
1201 expression, parsing expression grammar, push down automaton, recursive
1202 descent, serialization, state, top-down parsing languages, transducer
1203
1205 Parsing and Grammars
1206
1208 Copyright (c) 2009 Andreas Kupries <andreas_kupries@users.sourceforge.net>
1209tcllib 1 pt::peg::to::param(n)