This file is indexed.

/usr/share/perl5/PPIx/Regexp.pm is in libppix-regexp-perl 0.036-1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  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
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
=head1 NAME

PPIx::Regexp - Represent a regular expression of some sort

=head1 SYNOPSIS

 use PPIx::Regexp;
 use PPIx::Regexp::Dumper;
 my $re = PPIx::Regexp->new( 'qr{foo}smx' );
 PPIx::Regexp::Dumper->new( $re )
     ->print();

=head1 INHERITANCE

C<PPIx::Regexp> is a L<PPIx::Regexp::Node|PPIx::Regexp::Node>.

C<PPIx::Regexp> has no descendants.

=head1 DESCRIPTION

The purpose of the F<PPIx-Regexp> package is to parse regular
expressions in a manner similar to the way the L<PPI|PPI> package parses
Perl. This class forms the root of the parse tree, playing a role
similar to L<PPI::Document|PPI::Document>.

This package shares with L<PPI|PPI> the property of being round-trip
safe. That is,

 my $expr = 's/ ( \d+ ) ( \D+ ) /$2$1/smxg';
 my $re = PPIx::Regexp->new( $expr );
 print $re->content() eq $expr ? "yes\n" : "no\n"

should print 'yes' for any valid regular expression.

Navigation is similar to that provided by L<PPI|PPI>. That is to say,
things like C<children>, C<find_first>, C<snext_sibling> and so on all
work pretty much the same way as in L<PPI|PPI>.

The class hierarchy is also similar to L<PPI|PPI>. Except for some
utility classes (the dumper, the lexer, and the tokenizer) all classes
are descended from L<PPIx::Regexp::Element|PPIx::Regexp::Element>, which
provides basic navigation. Tokens are descended from
L<PPIx::Regexp::Token|PPIx::Regexp::Token>, which provides content. All
containers are descended from L<PPIx::Regexp::Node|PPIx::Regexp::Node>,
which provides for children, and all structure elements are descended
from L<PPIx::Regexp::Structure|PPIx::Regexp::Structure>, which provides
beginning and ending delimiters, and a type.

There are two features of L<PPI|PPI> that this package does not provide
- mutability and operator overloading. There are no plans for serious
mutability, though something like L<PPI|PPI>'s C<prune> functionality
might be considered. Similarly there are no plans for operator
overloading, which appears to the author to represent a performance hit
for little tangible gain.

=head1 NOTICE

The author will attempt to preserve the documented interface, but if the
interface needs to change to correct some egregiously bad design or
implementation decision, then it will change.  Any incompatible changes
will go through a deprecation cycle.

The goal of this package is to parse well-formed regular expressions
correctly. A secondary goal is not to blow up on ill-formed regular
expressions. The correct identification and characterization of
ill-formed regular expressions is B<not> a goal of this package.

This policy attempts to track features in development releases as well
as public releases. However, features added in a development release and
then removed before the next production release B<will not> be tracked,
and any functionality relating to such features B<will be removed>. The
issue here is the potential re-use (with different semantics) of syntax
that did not make it into the production release.

=head1 METHODS

This class provides the following public methods. Methods not documented
here are private, and unsupported in the sense that the author reserves
the right to change or remove them without notice.

=cut

package PPIx::Regexp;

use strict;
use warnings;

use base qw{ PPIx::Regexp::Node };

use PPIx::Regexp::Lexer ();
use PPIx::Regexp::Token::Modifier ();	# For its modifier manipulations.
use PPIx::Regexp::Util qw{ __instance };
use Scalar::Util qw{ refaddr };

our $VERSION = '0.036';

=head2 new

 my $re = PPIx::Regexp->new('/foo/');

This method instantiates a C<PPIx::Regexp> object from a string, a
L<PPI::Token::QuoteLike::Regexp|PPI::Token::QuoteLike::Regexp>, a
L<PPI::Token::Regexp::Match|PPI::Token::Regexp::Match>, or a
L<PPI::Token::Regexp::Substitute|PPI::Token::Regexp::Substitute>.
Honestly, any L<PPI::Element|PPI::Element> will do, but only the three
Regexp classes mentioned previously are likely to do anything useful.

Optionally you can pass one or more name/value pairs after the regular
expression. The possible options are:

=over

=item default_modifiers array_reference

This option specifies a reference to an array of default modifiers to
apply to the regular expression being parsed. Each modifier is specified
as a string. Any actual modifiers found supersede the defaults.

When applying the defaults, C<'?'> and C<'/'> are completely ignored,
and C<'^'> is ignored unless it occurs at the beginning of the modifier.
The first dash (C<'-'>) causes subsequent modifiers to be negated.

So, for example, if you wish to produce a C<PPIx::Regexp> object
representing the regular expression in

 use re '/smx';
 {
    no re '/x';
    m/ foo /;
 }

you would (after some help from L<PPI|PPI> in finding the relevant
statements), do something like

 my $re = PPIx::Regexp->new( 'm/ foo /',
     default_modifiers => [ '/smx', '-/x' ] );
`
=item encoding name

This option specifies the encoding of the regular expression. This is
passed to the tokenizer, which will C<decode> the regular expression
string before it tokenizes it. For example:

 my $re = PPIx::Regexp->new( '/foo/',
     encoding => 'iso-8859-1',
 );

=item trace number

If greater than zero, this option causes trace output from the parse.
The author reserves the right to change or eliminate this without
notice.

=back

Passing optional input other than the above is not an error, but neither
is it supported.

=cut

{

    my $errstr;

    sub new {
	my ( $class, $content, %args ) = @_;
	ref $class and $class = ref $class;

	$errstr = undef;

	my $tokenizer = PPIx::Regexp::Tokenizer->new(
	    $content, %args ) or do {
	    $errstr = PPIx::Regexp::Tokenizer->errstr();
	    return;
	};

	my $lexer = PPIx::Regexp::Lexer->new( $tokenizer, %args );
	my @nodes = $lexer->lex();
	my $self = $class->SUPER::_new( @nodes );
	$self->{source} = $content;
	$self->{failures} = $lexer->failures();
	$self->{effective_modifiers} =
	    $tokenizer->__effective_modifiers();
	return $self;
    }

    sub errstr {
	return $errstr;
    }

}

=head2 new_from_cache

This static method wraps L</new> in a caching mechanism. Only one object
will be generated for a given L<PPI::Element|PPI::Element>, no matter
how many times this method is called. Calls after the first for a given
L<PPI::Element|PPI::ELement> simply return the same C<PPIx::Regexp>
object.

When the C<PPIx::Regexp> object is returned from cache, the values of
the optional arguments are ignored.

Calls to this method with the regular expression in a string rather than
a L<PPI::Element|PPI::Element> will not be cached.

B<Caveat:> This method is provided for code like
L<Perl::Critic|Perl::Critic> which might instantiate the same object
multiple times. The cache will persist until L</flush_cache> is called.

=head2 flush_cache

 $re->flush_cache();            # Remove $re from cache
 PPIx::Regexp->flush_cache();   # Empty the cache

This method flushes the cache used by L</new_from_cache>. If called as a
static method with no arguments, the entire cache is emptied. Otherwise
any objects specified are removed from the cache.

=cut

{

    my %cache;

    our $DISABLE_CACHE;		# Leave this undocumented, at least for
				# now.

    sub _cache_size {
	return scalar keys %cache;
    }

    sub new_from_cache {
	my ( $class, $content, %args ) = @_;

	__instance( $content, 'PPI::Element' )
	    or return $class->new( $content, %args );

	$DISABLE_CACHE and return $class->new( $content, %args );

	my $addr = refaddr( $content );
	exists $cache{$addr} and return $cache{$addr};

	my $self = $class->new( $content, %args )
	    or return;

	$cache{$addr} = $self;

	return $self;

    }

    sub flush_cache {
	my @args = @_;

	ref $args[0] or shift @args;

	if ( @args ) {
	    foreach my $obj ( @args ) {
		if ( __instance( $obj, __PACKAGE__ ) &&
		    __instance( ( my $parent = $obj->source() ),
			'PPI::Element' ) ) {
		    delete $cache{ refaddr( $parent ) };
		}
	    }
	} else {
	    %cache = ();
	}
	return;
    }

}

sub can_be_quantified { return; }


=head2 capture_names

 foreach my $name ( $re->capture_names() ) {
     print "Capture name '$name'\n";
 }

This convenience method returns the capture names found in the regular
expression.

This method is equivalent to

 $self->regular_expression()->capture_names();

except that if C<< $self->regular_expression() >> returns C<undef>
(meaning that something went terribly wrong with the parse) this method
will simply return.

=cut

sub capture_names {
    my ( $self ) = @_;
    my $re = $self->regular_expression() or return;
    return $re->capture_names();
}

=head2 delimiters

 print join("\t", PPIx::Regexp->new('s/foo/bar/')->delimiters());
 # prints '//      //'

When called in list context, this method returns either one or two
strings, depending on whether the parsed expression has a replacement
string. In the case of non-bracketed substitutions, the start delimiter
of the replacement string is considered to be the same as its finish
delimiter, as illustrated by the above example.

When called in scalar context, you get the delimiters of the regular
expression; that is, element 0 of the array that is returned in list
context.

Optionally, you can pass an index value and the corresponding delimiters
will be returned; index 0 represents the regular expression's
delimiters, and index 1 represents the replacement string's delimiters,
which may be undef. For example,

 print PPIx::Regexp->new('s{foo}<bar>')-delimiters(1);
 # prints '<>'

If the object was not initialized with a valid regexp of some sort, the
results of this method are undefined.

=cut

sub delimiters {
    my ( $self, $inx ) = @_;

    my @rslt;
    foreach my $method ( qw{ regular_expression replacement } ) {
	defined ( my $obj = $self->$method() ) or next;
	push @rslt, $obj->delimiters();
    }

    defined $inx and return $rslt[$inx];
    wantarray and return @rslt;
    defined wantarray and return $rslt[0];
    return;
}

=head2 errstr

This static method returns the error string from the most recent attempt
to instantiate a C<PPIx::Regexp>. It will be C<undef> if the most recent
attempt succeeded.

=cut

# defined above, just after sub new.

=head2 failures

 print "There were ", $re->failures(), " parse failures\n";

This method returns the number of parse failures. This is a count of the
number of unknown tokens plus the number of unterminated structures plus
the number of unmatched right brackets of any sort.

=cut

sub failures {
    my ( $self ) = @_;
    return $self->{failures};
}

=head2 max_capture_number

 print "Highest used capture number ",
     $re->max_capture_number(), "\n";

This convenience method returns the highest capture number used by the
regular expression. If there are no captures, the return will be 0.

This method is equivalent to

 $self->regular_expression()->max_capture_number();

except that if C<< $self->regular_expression() >> returns C<undef>
(meaning that something went terribly wrong with the parse) this method
will too.

=cut

sub max_capture_number {
    my ( $self ) = @_;
    my $re = $self->regular_expression() or return;
    return $re->max_capture_number();
}

=head2 modifier

 my $re = PPIx::Regexp->new( 's/(foo)/${1}bar/smx' );
 print $re->modifier()->content(), "\n";
 # prints 'smx'.

This method retrieves the modifier of the object. This comes from the
end of the initializing string or object and will be a
L<PPIx::Regexp::Token::Modifier|PPIx::Regexp::Token::Modifier>.

B<Note> that this object represents the actual modifiers present on the
regexp, and does not take into account any that may have been applied by
default (i.e. via the C<default_modifiers> argument to C<new()>). For
something that takes account of default modifiers, see
L<modifier_asserted()|/modifier_asserted>, below.

In the event of a parse failure, there may not be a modifier present, in
which case nothing is returned.

=cut

sub modifier {
    my ( $self ) = @_;
    return $self->_component( 'PPIx::Regexp::Token::Modifier' );
}

=head2 modifier_asserted

 my $re = PPIx::Regexp->new( '/ . /',
     default_modifiers => [ 'smx' ] );
 print $re->modifier_asserted( 'x' ) ? "yes\n" : "no\n";
 # prints 'yes'.

This method returns true if the given modifier is asserted for the
regexp, whether explicitly or by the modifiers passed in the
C<default_modifiers> argument.

=cut

sub modifier_asserted {
    my ( $self, $modifier ) = @_;
    return PPIx::Regexp::Token::Modifier::__asserts(
	$self->{effective_modifiers},
	$modifier,
    );
}

# This is a kluge for both determining whether the object asserts
# modifiers (hence the 'ductype') and determining whether the given
# modifier is actually asserted. The signature is the invocant and the
# modifier name, which must not be undef. The return is a boolean.
*__ducktype_modifier_asserted = \&modifier_asserted;

=head2 regular_expression

 my $re = PPIx::Regexp->new( 's/(foo)/${1}bar/smx' );
 print $re->regular_expression()->content(), "\n";
 # prints '/(foo)/'.

This method returns that portion of the object which actually represents
a regular expression.

=cut

sub regular_expression {
    my ( $self ) = @_;
    return $self->_component( 'PPIx::Regexp::Structure::Regexp' );
}

=head2 replacement

 my $re = PPIx::Regexp->new( 's/(foo)/${1}bar/smx' );
 print $re->replacement()->content(), "\n";
 # prints '${1}bar/'.

This method returns that portion of the object which represents the
replacement string. This will be C<undef> unless the regular expression
actually has a replacement string. Delimiters will be included, but
there will be no beginning delimiter unless the regular expression was
bracketed.

=cut

sub replacement {
    my ( $self ) = @_;
    return $self->_component( 'PPIx::Regexp::Structure::Replacement' );
}

=head2 source

 my $source = $re->source();

This method returns the object or string that was used to instantiate
the object.

=cut

sub source {
    my ( $self ) = @_;
    return $self->{source};
}

=head2 type

 my $re = PPIx::Regexp->new( 's/(foo)/${1}bar/smx' );
 print $re->type()->content(), "\n";
 # prints 's'.

This method retrieves the type of the object. This comes from the
beginning of the initializing string or object, and will be a
L<PPIx::Regexp::Token::Structure|PPIx::Regexp::Token::Structure>
whose C<content> is one of 's',
'm', 'qr', or ''.

=cut

sub type {
    my ( $self ) = @_;
    return $self->_component( 'PPIx::Regexp::Token::Structure' );
}

sub _component {
    my ( $self, $class ) = @_;
    foreach my $elem ( $self->children() ) {
	$elem->isa( $class ) and return $elem;
    }
    return;
}

1;

__END__

=head1 RESTRICTIONS

By the nature of this module, it is never going to get everything right.
Many of the known problem areas involve interpolations one way or
another.

=head2 Ambiguous Syntax

Perl's regular expressions contain cases where the syntax is ambiguous.
A particularly egregious example is an interpolation followed by square
or curly brackets, for example C<$foo[...]>. There is nothing in the
syntax to say whether the programmer wanted to interpolate an element of
array C<@foo>, or whether he wanted to interpolate scalar C<$foo>, and
then follow that interpolation by a character class.

The F<perlop> documentation notes that in this case what Perl does is to
guess. That is, it employs various heuristics on the code to try to
figure out what the programmer wanted. These heuristics are documented
as being undocumented (!) and subject to change without notice.

Given this situation, this module's chances of duplicating every Perl
version's interpretation of every regular expression are pretty much nil.
What it does now is to assume that square brackets containing B<only> an
integer or an interpolation represent a subscript; otherwise they
represent a character class. Similarly, curly brackets containing
B<only> a bareword or an interpolation are a subscript; otherwise they
represent a quantifier.

=head2 Changes in Syntax

Sometimes the introduction of new syntax changes the way a regular
expression is parsed. For example, the C<\v> character class was
introduced in Perl 5.9.5. But it did not represent a syntax error prior
to that version of Perl, it was simply parsed as C<v>. So

 $ perl -le 'print "v" =~ m/\v/ ? "yes" : "no"'

prints "yes" under Perl 5.8.9, but "no" under 5.10.0. C<PPIx::Regexp>
generally assumes the more modern parse in cases like this.

=head2 Static Parsing

It is well known that Perl can not be statically parsed. That is, you
can not completely parse a piece of Perl code without executing that
same code.

Nevertheless, this class is trying to statically parse regular
expressions. The main problem with this is that there is no way to know
what is being interpolated into the regular expression by an
interpolated variable. This is a problem because the interpolated value
can change the interpretation of adjacent elements.

This module deals with this by making assumptions about what is in an
interpolated variable. These assumptions will not be enumerated here,
but in general the principal is to assume the interpolated value does
not change the interpretation of the regular expression. For example,

 my $foo = 'a-z]';
 my $re = qr{[$foo};

is fine with the Perl interpreter, but will confuse the dickens out of
this module. Similarly and more usefully, something like

 my $mods = 'i';
 my $re = qr{(?$mods:foo)};

or maybe

 my $mods = 'i';
 my $re = qr{(?$mods)$foo};

probably sets a modifier of some sort, and that is how this module
interprets it. If the interpolation is B<not> about modifiers, this
module will get it wrong. Another such semi-benign example is

 my $foo = $] >= 5.010 ? '?<foo>' : '';
 my $re = qr{($foo\w+)};

which will parse, but this module will never realize that it might be
looking at a named capture.

=head2 Non-Standard Syntax

There are modules out there that alter the syntax of Perl. If the syntax
of a regular expression is altered, this module has no way to understand
that it has been altered, much less to adapt to the alteration. The
following modules are known to cause problems:

L<Acme::PerlML|Acme::PerlML>, which renders Perl as XML.

L<Data::PostfixDeref|Data::PostfixDeref>, which causes Perl to interpret
suffixed empty brackets as dereferencing the thing they suffix.

L<Filter::Trigraph|Filter::Trigraph>, which recognizes ANSI C trigraphs,
allowing Perl to be written in the ISO 646 character set.

L<Perl6::Pugs|Perl6::Pugs>. Enough said.

L<Perl6::Rules|Perl6::Rules>, which back-ports some of the Perl 6
regular expression syntax to Perl 5.

L<Regexp::Extended|Regexp::Extended>, which extends regular expressions
in various ways, some of which seem to conflict with Perl 5.010.

=head1 SEE ALSO

L<Regexp::Parser|Regexp::Parser>, which parses a bare regular expression
(without enclosing C<qr{}>, C<m//>, or whatever) and uses a different
navigation model.

=head1 SUPPORT

Support is by the author. Please file bug reports at
L<http://rt.cpan.org>, or in electronic mail to the author.

=head1 AUTHOR

Thomas R. Wyant, III F<wyant at cpan dot org>

=head1 COPYRIGHT AND LICENSE

Copyright (C) 2009-2014 by Thomas R. Wyant, III

This program is free software; you can redistribute it and/or modify it
under the same terms as Perl 5.10.0. For more details, see the full text
of the licenses in the directory LICENSES.

This program is distributed in the hope that it will be useful, but
without any warranty; without even the implied warranty of
merchantability or fitness for a particular purpose.

=cut

# ex: set textwidth=72 :