File: pt_peg_export_container.html

package info (click to toggle)
tcllib 1.20%2Bdfsg-1
  • links: PTS
  • area: main
  • in suites: bullseye
  • size: 68,064 kB
  • sloc: tcl: 216,842; ansic: 14,250; sh: 2,846; xml: 1,766; yacc: 1,145; pascal: 881; makefile: 107; perl: 84; f90: 84; python: 33; ruby: 13; php: 11
file content (557 lines) | stat: -rw-r--r-- 28,435 bytes parent folder | download | duplicates (2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
<!DOCTYPE html><html><head>
<title>pt::peg::export::container - Parser Tools</title>
<style type="text/css"><!--
    HTML {
	background: 	#FFFFFF;
	color: 		black;
    }
    BODY {
	background: 	#FFFFFF;
	color:	 	black;
    }
    DIV.doctools {
	margin-left:	10%;
	margin-right:	10%;
    }
    DIV.doctools H1,DIV.doctools H2 {
	margin-left:	-5%;
    }
    H1, H2, H3, H4 {
	margin-top: 	1em;
	font-family:	sans-serif;
	font-size:	large;
	color:		#005A9C;
	background: 	transparent;
	text-align:		left;
    }
    H1.doctools_title {
	text-align: center;
    }
    UL,OL {
	margin-right: 0em;
	margin-top: 3pt;
	margin-bottom: 3pt;
    }
    UL LI {
	list-style: disc;
    }
    OL LI {
	list-style: decimal;
    }
    DT {
	padding-top: 	1ex;
    }
    UL.doctools_toc,UL.doctools_toc UL, UL.doctools_toc UL UL {
	font:		normal 12pt/14pt sans-serif;
	list-style:	none;
    }
    LI.doctools_section, LI.doctools_subsection {
	list-style: 	none;
	margin-left: 	0em;
	text-indent:	0em;
	padding: 	0em;
    }
    PRE {
	display: 	block;
	font-family:	monospace;
	white-space:	pre;
	margin:		0%;
	padding-top:	0.5ex;
	padding-bottom:	0.5ex;
	padding-left:	1ex;
	padding-right:	1ex;
	width:		100%;
    }
    PRE.doctools_example {
	color: 		black;
	background: 	#f5dcb3;
	border:		1px solid black;
    }
    UL.doctools_requirements LI, UL.doctools_syntax LI {
	list-style: 	none;
	margin-left: 	0em;
	text-indent:	0em;
	padding:	0em;
    }
    DIV.doctools_synopsis {
	color: 		black;
	background: 	#80ffff;
	border:		1px solid black;
	font-family:	serif;
	margin-top: 	1em;
	margin-bottom: 	1em;
    }
    UL.doctools_syntax {
	margin-top: 	1em;
	border-top:	1px solid black;
    }
    UL.doctools_requirements {
	margin-bottom: 	1em;
	border-bottom:	1px solid black;
    }
--></style>
</head>
<!-- Generated from file 'plugin.inc' by tcllib/doctools with format 'html'
   -->
<!-- Copyright &amp;copy; 2009 Andreas Kupries &amp;lt;andreas_kupries@users.sourceforge.net&amp;gt;
   -->
<!-- pt::peg::export::container.n
   -->
<body><hr> [
   <a href="../../../../../../../../home">Tcllib Home</a>
&#124; <a href="../../../../toc.html">Main Table Of Contents</a>
&#124; <a href="../../../toc.html">Table Of Contents</a>
&#124; <a href="../../../../index.html">Keyword Index</a>
&#124; <a href="../../../../toc0.html">Categories</a>
&#124; <a href="../../../../toc1.html">Modules</a>
&#124; <a href="../../../../toc2.html">Applications</a>
 ] <hr>
<div class="doctools">
<h1 class="doctools_title">pt::peg::export::container(n) 1 tcllib &quot;Parser Tools&quot;</h1>
<div id="name" class="doctools_section"><h2><a name="name">Name</a></h2>
<p>pt::peg::export::container - PEG Export Plugin. Write CONTAINER format</p>
</div>
<div id="toc" class="doctools_section"><h2><a name="toc">Table Of Contents</a></h2>
<ul class="doctools_toc">
<li class="doctools_section"><a href="#toc">Table Of Contents</a></li>
<li class="doctools_section"><a href="#synopsis">Synopsis</a></li>
<li class="doctools_section"><a href="#section1">Description</a></li>
<li class="doctools_section"><a href="#section2">API</a></li>
<li class="doctools_section"><a href="#section3">Configuration</a></li>
<li class="doctools_section"><a href="#section4">Grammar Container</a>
<ul>
<li class="doctools_subsection"><a href="#subsection1">Example</a></li>
</ul>
</li>
<li class="doctools_section"><a href="#section5">PEG serialization format</a>
<ul>
<li class="doctools_subsection"><a href="#subsection2">Example</a></li>
</ul>
</li>
<li class="doctools_section"><a href="#section6">PE serialization format</a>
<ul>
<li class="doctools_subsection"><a href="#subsection3">Example</a></li>
</ul>
</li>
<li class="doctools_section"><a href="#section7">Bugs, Ideas, Feedback</a></li>
<li class="doctools_section"><a href="#keywords">Keywords</a></li>
<li class="doctools_section"><a href="#category">Category</a></li>
<li class="doctools_section"><a href="#copyright">Copyright</a></li>
</ul>
</div>
<div id="synopsis" class="doctools_section"><h2><a name="synopsis">Synopsis</a></h2>
<div class="doctools_synopsis">
<ul class="doctools_requirements">
<li>package require <b class="pkgname">Tcl 8.5</b></li>
<li>package require <b class="pkgname">pt::peg::export::container <span class="opt">?1?</span></b></li>
<li>package require <b class="pkgname">pt::peg::to::container</b></li>
</ul>
<ul class="doctools_syntax">
<li><a href="#1"><b class="cmd"><a href="../../../../index.html#export">export</a></b> <i class="arg">serial</i> <i class="arg">configuration</i></a></li>
</ul>
</div>
</div>
<div id="section1" class="doctools_section"><h2><a name="section1">Description</a></h2>
<p>Are you lost ?
Do you have trouble understanding this document ?
In that case please read the overview provided by the
<i class="term"><a href="pt_introduction.html">Introduction to Parser Tools</a></i>. This document is the
entrypoint to the whole system the current package is a part of.</p>
<p>This package implements the parsing expression grammar export plugin
for the generation of CONTAINER markup.</p>
<p>It resides in the Export section of the Core Layer of Parser Tools and
is intended to be used by <b class="package"><a href="pt_peg_export.html">pt::peg::export</a></b>, the export
manager, sitting between it and the corresponding core conversion
functionality provided by <b class="package"><a href="pt_peg_to_container.html">pt::peg::to::container</a></b>.</p>
<p><img alt="arch_core_eplugins" src="../../../../image/arch_core_eplugins.png"></p>
<p>While the direct use of this package with a regular interpreter is
possible, this is strongly disrecommended and requires a number of
contortions to provide the expected environment.
The proper way to use this functionality depends on the situation:</p>
<ol class="doctools_enumerated">
<li><p>In an untrusted environment the proper access is through the package
<b class="package"><a href="pt_peg_export.html">pt::peg::export</a></b> and the export manager objects it
provides.</p></li>
<li><p>In a trusted environment however simply use the package
<b class="package"><a href="pt_peg_to_container.html">pt::peg::to::container</a></b> and access the core
conversion functionality directly.</p></li>
</ol>
</div>
<div id="section2" class="doctools_section"><h2><a name="section2">API</a></h2>
<p>The API provided by this package satisfies the specification of the
Plugin API found in the <i class="term"><a href="pt_to_api.html">Parser Tools Export API</a></i>
specification.</p>
<dl class="doctools_definitions">
<dt><a name="1"><b class="cmd"><a href="../../../../index.html#export">export</a></b> <i class="arg">serial</i> <i class="arg">configuration</i></a></dt>
<dd><p>This command takes the canonical serialization of a parsing expression
grammar, as specified in section <span class="sectref"><a href="#section5">PEG serialization format</a></span>,
and contained in <i class="arg">serial</i>, the <i class="arg">configuration</i>, a dictionary,
and generates CONTAINER markup encoding the grammar.
The created string is then returned as the result of the command.</p></dd>
</dl>
</div>
<div id="section3" class="doctools_section"><h2><a name="section3">Configuration</a></h2>
<p>The CONTAINER export plugin recognizes the following configuration
variables and changes its behaviour as they specify.</p>
<dl class="doctools_arguments">
<dt>enum <i class="arg">mode</i></dt>
<dd><p>The value of this configuration variable controls which methods of
<b class="package"><a href="pt_pegrammar.html">pt::peg</a></b> instances the plugin will use to specify the
grammar. There are two legal values</p>
<dl class="doctools_definitions">
<dt><b class="const">bulk</b></dt>
<dd><p>In this mode the methods <b class="method">start</b>, <b class="method">add</b>, <b class="method">modes</b>,
and <b class="method">rules</b> are used to specify the grammar in a bulk manner,
i.e. as a set of nonterminal symbols, and two dictionaries mapping
from the symbols to their semantic modes and parsing expressions.</p>
<p>This mode is the default.</p></dd>
<dt><b class="const">incremental</b></dt>
<dd><p>In this mode the methods <b class="method">start</b>, <b class="method">add</b>, <b class="method">mode</b>,
and <b class="method">rule</b> are used to specify the grammar piecemal, with each
nonterminal having its own block of defining commands.</p></dd>
</dl></dd>
<dt>string <i class="arg">template</i></dt>
<dd><p>If this configuration variable is set it is assumed to contain a
string into which to put the generated code and other configuration
data. The various locations are expected to be specified with the
following placeholders:</p>
<dl class="doctools_definitions">
<dt><b class="const">@user@</b></dt>
<dd><p>To be replaced with the value of the configuration variable <b class="option">user</b>.</p></dd>
<dt><b class="const">@format@</b></dt>
<dd><p>To be replaced with the the constant <b class="const">CONTAINER</b>.</p></dd>
<dt><b class="const">@file@</b></dt>
<dd><p>To be replaced with the value of the configuration variable <b class="option">file</b>.</p></dd>
<dt><b class="const">@name@</b></dt>
<dd><p>To be replaced with the value of the configuration variable <b class="option">name</b>.</p></dd>
<dt><b class="const">@mode@</b></dt>
<dd><p>To be replaced with the value of the configuration variable <b class="option">mode</b>.</p></dd>
<dt><b class="const">@code@</b></dt>
<dd><p>To be replaced with the generated code.</p></dd>
</dl>
<p>If this configuration variable is not set, or empty, then the plugin
falls back to a standard template, which is defined as &quot;<b class="const">@code@</b>&quot;.</p></dd>
</dl>
<p><em>Note</em> that this plugin may ignore the standard configuration
variables <b class="variable">user</b>, <b class="variable">format</b>, <b class="variable">file</b>, and their values,
depending on the chosen template.</p>
<p>The content of the standard configuration variable <b class="variable">name</b>, if set,
is used as name of the grammar in the output. Otherwise the plugin
falls back to the default name <b class="const">a_pe_grammar</b>.</p>
</div>
<div id="section4" class="doctools_section"><h2><a name="section4">Grammar Container</a></h2>
<p>The <b class="const">container</b> format is another form of describing parsing
expression grammars. While data in this format is executable it does
not constitute a parser for the grammar. It always has to be used in
conjunction with the package <b class="package"><a href="pt_peg_interp.html">pt::peg::interp</a></b>, a grammar
interpreter.</p>
<p>The format represents grammars by a <b class="cmd">snit::type</b>, i.e. class,
whose instances are API-compatible to the instances of the
<b class="package"><a href="pt_peg_container.html">pt::peg::container</a></b> package, and which are preloaded with the
grammar in question.</p>
<p>It has no direct formal specification beyond what was said above.</p>
<div id="subsection1" class="doctools_subsection"><h3><a name="subsection1">Example</a></h3>
<p>Assuming the following PEG for simple mathematical expressions</p>
<pre class="doctools_example">
PEG calculator (Expression)
    Digit      &lt;- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9'       ;
    Sign       &lt;- '-' / '+'                                     ;
    Number     &lt;- Sign? Digit+                                  ;
    Expression &lt;- Term (AddOp Term)*                            ;
    MulOp      &lt;- '*' / '/'                                     ;
    Term       &lt;- Factor (MulOp Factor)*                        ;
    AddOp      &lt;- '+'/'-'                                       ;
    Factor     &lt;- '(' Expression ')' / Number                   ;
END;
</pre>
<p>one possible CONTAINER serialization for it is</p>
<pre class="doctools_example">
snit::type a_pe_grammar {
    constructor {} {
        install myg using pt::peg::container ${selfns}::G
        $myg start {n Expression}
        $myg add   AddOp Digit Expression Factor MulOp Number Sign Term
        $myg modes {
            AddOp      value
            Digit      value
            Expression value
            Factor     value
            MulOp      value
            Number     value
            Sign       value
            Term       value
        }
        $myg rules {
            AddOp      {/ {t -} {t +}}
            Digit      {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}}
            Expression {/ {x {t \50} {n Expression} {t \51}} {x {n Factor} {* {x {n MulOp} {n Factor}}}}}
            Factor     {x {n Term} {* {x {n AddOp} {n Term}}}}
            MulOp      {/ {t *} {t /}}
            Number     {x {? {n Sign}} {+ {n Digit}}}
            Sign       {/ {t -} {t +}}
            Term       {n Number}
        }
        return
    }
    component myg
    delegate method * to myg
}
</pre>
</div>
</div>
<div id="section5" class="doctools_section"><h2><a name="section5">PEG serialization format</a></h2>
<p>Here we specify the format used by the Parser Tools to serialize
Parsing Expression Grammars as immutable values for transport,
comparison, etc.</p>
<p>We distinguish between <i class="term">regular</i> and <i class="term">canonical</i>
serializations.
While a PEG may have more than one regular serialization only exactly
one of them will be <i class="term">canonical</i>.</p>
<dl class="doctools_definitions">
<dt>regular serialization</dt>
<dd><ol class="doctools_enumerated">
<li><p>The serialization of any PEG is a nested Tcl dictionary.</p></li>
<li><p>This dictionary holds a single key, <b class="const">pt::grammar::peg</b>, and its
value. This value holds the contents of the grammar.</p></li>
<li><p>The contents of the grammar are a Tcl dictionary holding the set of
nonterminal symbols and the starting expression. The relevant keys and
their values are</p>
<dl class="doctools_definitions">
<dt><b class="const">rules</b></dt>
<dd><p>The value is a Tcl dictionary whose keys are the names of the
nonterminal symbols known to the grammar.</p>
<ol class="doctools_enumerated">
<li><p>Each nonterminal symbol may occur only once.</p></li>
<li><p>The empty string is not a legal nonterminal symbol.</p></li>
<li><p>The value for each symbol is a Tcl dictionary itself. The relevant
keys and their values in this dictionary are</p>
<dl class="doctools_definitions">
<dt><b class="const">is</b></dt>
<dd><p>The value is the serialization of the parsing expression describing
the symbols sentennial structure, as specified in the section
<span class="sectref"><a href="#section6">PE serialization format</a></span>.</p></dd>
<dt><b class="const">mode</b></dt>
<dd><p>The value can be one of three values specifying how a parser should
handle the semantic value produced by the symbol.</p>
<dl class="doctools_definitions">
<dt><b class="const">value</b></dt>
<dd><p>The semantic value of the nonterminal symbol is an abstract syntax
tree consisting of a single node node for the nonterminal itself,
which has the ASTs of the symbol's right hand side as its children.</p></dd>
<dt><b class="const">leaf</b></dt>
<dd><p>The semantic value of the nonterminal symbol is an abstract syntax
tree consisting of a single node node for the nonterminal, without any
children. Any ASTs generated by the symbol's right hand side are
discarded.</p></dd>
<dt><b class="const">void</b></dt>
<dd><p>The nonterminal has no semantic value. Any ASTs generated by the
symbol's right hand side are discarded (as well).</p></dd>
</dl></dd>
</dl>
</li>
</ol></dd>
<dt><b class="const">start</b></dt>
<dd><p>The value is the serialization of the start parsing expression of the
grammar, as specified in the section <span class="sectref"><a href="#section6">PE serialization format</a></span>.</p></dd>
</dl>
</li>
<li><p>The terminal symbols of the grammar are specified implicitly as the
set of all terminal symbols used in the start expression and on the
RHS of the grammar rules.</p></li>
</ol></dd>
<dt>canonical serialization</dt>
<dd><p>The canonical serialization of a grammar has the format as specified
in the previous item, and then additionally satisfies the constraints
below, which make it unique among all the possible serializations of
this grammar.</p>
<ol class="doctools_enumerated">
<li><p>The keys found in all the nested Tcl dictionaries are sorted in
ascending dictionary order, as generated by Tcl's builtin command
<b class="cmd">lsort -increasing -dict</b>.</p></li>
<li><p>The string representation of the value is the canonical representation
of a Tcl dictionary. I.e. it does not contain superfluous whitespace.</p></li>
</ol></dd>
</dl>
<div id="subsection2" class="doctools_subsection"><h3><a name="subsection2">Example</a></h3>
<p>Assuming the following PEG for simple mathematical expressions</p>
<pre class="doctools_example">
PEG calculator (Expression)
    Digit      &lt;- '0'/'1'/'2'/'3'/'4'/'5'/'6'/'7'/'8'/'9'       ;
    Sign       &lt;- '-' / '+'                                     ;
    Number     &lt;- Sign? Digit+                                  ;
    Expression &lt;- Term (AddOp Term)*                            ;
    MulOp      &lt;- '*' / '/'                                     ;
    Term       &lt;- Factor (MulOp Factor)*                        ;
    AddOp      &lt;- '+'/'-'                                       ;
    Factor     &lt;- '(' Expression ')' / Number                   ;
END;
</pre>
<p>then its canonical serialization (except for whitespace) is</p>
<pre class="doctools_example">
pt::grammar::peg {
    rules {
        AddOp      {is {/ {t -} {t +}}                                                                mode value}
        Digit      {is {/ {t 0} {t 1} {t 2} {t 3} {t 4} {t 5} {t 6} {t 7} {t 8} {t 9}}                mode value}
        Expression {is {x {n Term} {* {x {n AddOp} {n Term}}}}                                        mode value}
        Factor     {is {/ {x {t (} {n Expression} {t )}} {n Number}}                                  mode value}
        MulOp      {is {/ {t *} {t /}}                                                                mode value}
        Number     {is {x {? {n Sign}} {+ {n Digit}}}                                                 mode value}
        Sign       {is {/ {t -} {t +}}                                                                mode value}
        Term       {is {x {n Factor} {* {x {n MulOp} {n Factor}}}}                                    mode value}
    }
    start {n Expression}
}
</pre>
</div>
</div>
<div id="section6" class="doctools_section"><h2><a name="section6">PE serialization format</a></h2>
<p>Here we specify the format used by the Parser Tools to serialize
Parsing Expressions as immutable values for transport, comparison,
etc.</p>
<p>We distinguish between <i class="term">regular</i> and <i class="term">canonical</i>
serializations.
While a parsing expression may have more than one regular
serialization only exactly one of them will be <i class="term">canonical</i>.</p>
<dl class="doctools_definitions">
<dt>Regular serialization</dt>
<dd><dl class="doctools_definitions">
<dt><b class="const">Atomic Parsing Expressions</b></dt>
<dd><ol class="doctools_enumerated">
<li><p>The string <b class="const">epsilon</b> is an atomic parsing expression. It matches
the empty string.</p></li>
<li><p>The string <b class="const">dot</b> is an atomic parsing expression. It matches
any character.</p></li>
<li><p>The string <b class="const">alnum</b> is an atomic parsing expression. It matches
any Unicode alphabet or digit character. This is a custom extension of
PEs based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">alpha</b> is an atomic parsing expression. It matches
any Unicode alphabet character. This is a custom extension of PEs
based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">ascii</b> is an atomic parsing expression. It matches
any Unicode character below U0080. This is a custom extension of PEs
based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">control</b> is an atomic parsing expression. It matches
any Unicode control character. This is a custom extension of PEs based
on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">digit</b> is an atomic parsing expression. It matches
any Unicode digit character. Note that this includes characters
outside of the [0..9] range. This is a custom extension of PEs
based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">graph</b> is an atomic parsing expression. It matches
any Unicode printing character, except for space. This is a custom
extension of PEs based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">lower</b> is an atomic parsing expression. It matches
any Unicode lower-case alphabet character. This is a custom extension
of PEs based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">print</b> is an atomic parsing expression. It matches
any Unicode printing character, including space. This is a custom
extension of PEs based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">punct</b> is an atomic parsing expression. It matches
any Unicode punctuation character. This is a custom extension of PEs
based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">space</b> is an atomic parsing expression. It matches
any Unicode space character. This is a custom extension of PEs based
on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">upper</b> is an atomic parsing expression. It matches
any Unicode upper-case alphabet character. This is a custom extension
of PEs based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">wordchar</b> is an atomic parsing expression. It
matches any Unicode word character. This is any alphanumeric character
(see alnum), and any connector punctuation characters (e.g.
underscore). This is a custom extension of PEs based on Tcl's builtin
command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">xdigit</b> is an atomic parsing expression. It matches
any hexadecimal digit character. This is a custom extension of PEs
based on Tcl's builtin command <b class="cmd">string is</b>.</p></li>
<li><p>The string <b class="const">ddigit</b> is an atomic parsing expression. It matches
any decimal digit character. This is a custom extension of PEs based
on Tcl's builtin command <b class="cmd">regexp</b>.</p></li>
<li><p>The expression
    [list t <b class="variable">x</b>]
is an atomic parsing expression. It matches the terminal string <b class="variable">x</b>.</p></li>
<li><p>The expression
    [list n <b class="variable">A</b>]
is an atomic parsing expression. It matches the nonterminal <b class="variable">A</b>.</p></li>
</ol></dd>
<dt><b class="const">Combined Parsing Expressions</b></dt>
<dd><ol class="doctools_enumerated">
<li><p>For parsing expressions <b class="variable">e1</b>, <b class="variable">e2</b>, ... the result of
    [list / <b class="variable">e1</b> <b class="variable">e2</b> ... ]
is a parsing expression as well.
This is the <i class="term">ordered choice</i>, aka <i class="term">prioritized choice</i>.</p></li>
<li><p>For parsing expressions <b class="variable">e1</b>, <b class="variable">e2</b>, ... the result of
    [list x <b class="variable">e1</b> <b class="variable">e2</b> ... ]
is a parsing expression as well.
This is the <i class="term">sequence</i>.</p></li>
<li><p>For a parsing expression <b class="variable">e</b> the result of
    [list * <b class="variable">e</b>]
is a parsing expression as well.
This is the <i class="term">kleene closure</i>, describing zero or more
repetitions.</p></li>
<li><p>For a parsing expression <b class="variable">e</b> the result of
    [list + <b class="variable">e</b>]
is a parsing expression as well.
This is the <i class="term">positive kleene closure</i>, describing one or more
repetitions.</p></li>
<li><p>For a parsing expression <b class="variable">e</b> the result of
    [list &amp; <b class="variable">e</b>]
is a parsing expression as well.
This is the <i class="term">and lookahead predicate</i>.</p></li>
<li><p>For a parsing expression <b class="variable">e</b> the result of
    [list ! <b class="variable">e</b>]
is a parsing expression as well.
This is the <i class="term">not lookahead predicate</i>.</p></li>
<li><p>For a parsing expression <b class="variable">e</b> the result of
    [list ? <b class="variable">e</b>]
is a parsing expression as well.
This is the <i class="term">optional input</i>.</p></li>
</ol></dd>
</dl></dd>
<dt>Canonical serialization</dt>
<dd><p>The canonical serialization of a parsing expression has the format as
specified in the previous item, and then additionally satisfies the
constraints below, which make it unique among all the possible
serializations of this parsing expression.</p>
<ol class="doctools_enumerated">
<li><p>The string representation of the value is the canonical representation
of a pure Tcl list. I.e. it does not contain superfluous whitespace.</p></li>
<li><p>Terminals are <em>not</em> encoded as ranges (where start and end of the
range are identical).</p></li>
</ol></dd>
</dl>
<div id="subsection3" class="doctools_subsection"><h3><a name="subsection3">Example</a></h3>
<p>Assuming the parsing expression shown on the right-hand side of the
rule</p>
<pre class="doctools_example">
    Expression &lt;- Term (AddOp Term)*
</pre>
<p>then its canonical serialization (except for whitespace) is</p>
<pre class="doctools_example">
    {x {n Term} {* {x {n AddOp} {n Term}}}}
</pre>
</div>
</div>
<div id="section7" class="doctools_section"><h2><a name="section7">Bugs, Ideas, Feedback</a></h2>
<p>This document, and the package it describes, will undoubtedly contain
bugs and other problems.
Please report such in the category <em>pt</em> of the
<a href="http://core.tcl.tk/tcllib/reportlist">Tcllib Trackers</a>.
Please also report any ideas for enhancements you may have for either
package and/or documentation.</p>
<p>When proposing code changes, please provide <em>unified diffs</em>,
i.e the output of <b class="const">diff -u</b>.</p>
<p>Note further that <em>attachments</em> are strongly preferred over
inlined patches. Attachments can be made by going to the <b class="const">Edit</b>
form of the ticket immediately after its creation, and then using the
left-most button in the secondary navigation bar.</p>
</div>
<div id="keywords" class="doctools_section"><h2><a name="keywords">Keywords</a></h2>
<p><a href="../../../../index.html#container">CONTAINER</a>, <a href="../../../../index.html#ebnf">EBNF</a>, <a href="../../../../index.html#ll_k_">LL(k)</a>, <a href="../../../../index.html#peg">PEG</a>, <a href="../../../../index.html#tdpl">TDPL</a>, <a href="../../../../index.html#context_free_languages">context-free languages</a>, <a href="../../../../index.html#export">export</a>, <a href="../../../../index.html#expression">expression</a>, <a href="../../../../index.html#grammar">grammar</a>, <a href="../../../../index.html#matching">matching</a>, <a href="../../../../index.html#parser">parser</a>, <a href="../../../../index.html#parsing_expression">parsing expression</a>, <a href="../../../../index.html#parsing_expression_grammar">parsing expression grammar</a>, <a href="../../../../index.html#plugin">plugin</a>, <a href="../../../../index.html#push_down_automaton">push down automaton</a>, <a href="../../../../index.html#recursive_descent">recursive descent</a>, <a href="../../../../index.html#serialization">serialization</a>, <a href="../../../../index.html#state">state</a>, <a href="../../../../index.html#top_down_parsing_languages">top-down parsing languages</a>, <a href="../../../../index.html#transducer">transducer</a></p>
</div>
<div id="category" class="doctools_section"><h2><a name="category">Category</a></h2>
<p>Parsing and Grammars</p>
</div>
<div id="copyright" class="doctools_section"><h2><a name="copyright">Copyright</a></h2>
<p>Copyright &copy; 2009 Andreas Kupries &lt;andreas_kupries@users.sourceforge.net&gt;</p>
</div>
</div></body></html>