1PPIx::Regexp::Token::MoUdsiefrieCro(n3t)ributed Perl DocPuPmIexn:t:aRteigoenxp::Token::Modifier(3)
2
6 PPIx::Regexp::Token::Modifier - Represent modifiers.
7
9 use PPIx::Regexp::Dumper;
10 PPIx::Regexp::Dumper->new( 'qr{foo}smx' )
11 ->print();
12 The trailing "smx" will be represented by this class.
14 This class also represents the whole of things like "(?ismx)". But the
16 modifiers in something like "(?i:foo)" are represented by a
17 PPIx::Regexp::Token::GroupType::Modifier.
18
20 "PPIx::Regexp::Token::Modifier" is a PPIx::Regexp::Token.
21 "PPIx::Regexp::Token::Modifier" is the parent of
23 PPIx::Regexp::Token::GroupType::Modifier.
24
26 This class represents modifier characters at the end of the regular
27 expression. For example, in "qr{foo}smx" this class would represent
28 the terminal "smx".
29 The "a", "aa", "d", "l", and "u" modifiers
31 The "a", "aa", "d", "l", and "u" modifiers, introduced starting in Perl
32 5.13.6, are used to force either Unicode pattern semantics ("u"),
33 locale semantics ("l") default semantics ("d" the traditional Perl
34 semantics, which can also mean 'dual' since it means Unicode if the
35 string's UTF-8 bit is on, and locale if the UTF-8 bit is off), or
36 restricted default semantics ("a"). These are mutually exclusive, and
37 only one can be asserted at a time. Asserting any of these overrides
38 the inherited value of any of the others. The "asserted()" method
39 reports as asserted the last one it sees, or none of them if it has
40 seen none.
41 For example, given "PPIx::Regexp::Token::Modifier" $elem representing
43 the invalid regular expression fragment "(?dul)", "$elem->asserted( 'l'
44 )" would return true, but "$elem->asserted( 'u' )" would return false.
45 Note that "$elem->negated( 'u' )" would also return false, since "u" is
46 not explicitly negated.
47 If $elem represented regular expression fragment "(?i)",
49 "$elem->asserted( 'd' )" would return false, since even though "d"
50 represents the default behavior it is not explicitly asserted.
51 The caret ("^") modifier
53 Calling "^" a modifier is a bit of a misnomer. The "(?^...)"
54 construction was introduced in Perl 5.13.6, to prevent the inheritance
55 of modifiers. The documentation calls the caret a shorthand equivalent
56 for "d-imsx", and that it the way this class handles it.
57 For example, given "PPIx::Regexp::Token::Modifier" $elem representing
59 regular expression fragment "(?^i)", "$elem->asserts( 'd' )" would
60 return true, since in the absence of an explicit "l" or "u" this class
61 considers the "^" to explicitly assert "d".
62 The caret handling is complicated by the fact that the 'n' modifier was
64 introduced in 5.21.8, at which point the caret became equivalent to
65 "d-imnsx". I did not feel I could unconditionally add the "-n" to the
66 expansion of the caret, because that would produce confusing output
67 from methods like explain(). Nor could I make it conditional on the
68 minimum perl version, because that information is not available early
69 enough in the parse. What I did was to expand the caret into "d-imnsx"
70 if and only if 'n' was in effect at some point in the scope in which
71 the modifier was parsed.
72 Continuing the above example, "$elem->asserts( 'n' )" and
74 "$elem->modifier_asserted( 'n' )" would both return false, but
75 "$elem->negates( 'n' )" would return true if and only if the "/m"
76 modifier has been asserted somewhere before and in-scope from this
77 token. The modifier_asserted( 'n' ) method is inherited from
78 PPIx::Regexp::Element.
79
81 This class provides the following public methods. Methods not
82 documented here are private, and unsupported in the sense that the
83 author reserves the right to change or remove them without notice.
84 asserts
86 $token->asserts( 'i' ) and print "token asserts i";
87 foreach ( $token->asserts() ) { print "token asserts $_\n" }
88 This method returns true if the token explicitly asserts the given
90 modifier. The example would return true for the modifier in "(?i:foo)",
91 but false for "(?-i:foo)".
92 Starting with version 0.036_01, if the argument is a single-character
94 modifier followed by an asterisk (intended as a wild card character),
95 the return is the number of times that modifier appears. In this case
96 an exception will be thrown if you specify a multi-character modifier
97 (e.g. 'ee*').
98 If called without an argument, or with an undef argument, all modifiers
100 explicitly asserted by this token are returned.
101 match_semantics
103 my $sem = $token->match_semantics();
104 defined $sem or $sem = 'undefined';
105 print "This token has $sem match semantics\n";
106 This method returns the match semantics asserted by the token, as one
108 of the strings 'a', 'aa', 'd', 'l', or 'u'. If no explicit match
109 semantics are asserted, this method returns "undef".
110 modifiers
112 my %mods = $token->modifiers();
113 Returns all modifiers asserted or negated by this token, and the values
115 set (true for asserted, false for negated). If called in scalar
116 context, returns a reference to a hash containing the values.
117 negates
119 $token->negates( 'i' ) and print "token negates i\n";
120 foreach ( $token->negates() ) { print "token negates $_\n" }
121 This method returns true if the token explicitly negates the given
123 modifier. The example would return true for the modifier in
124 "(?-i:foo)", but false for "(?i:foo)".
125 If called without an argument, or with an undef argument, all modifiers
127 explicitly negated by this token are returned.
128
130 Support is by the author. Please file bug reports at
131 <https://rt.cpan.org>, or in electronic mail to the author.
132
134 Thomas R. Wyant, III wyant at cpan dot org
135
137 Copyright (C) 2009-2020 by Thomas R. Wyant, III
138 This program is free software; you can redistribute it and/or modify it
140 under the same terms as Perl 5.10.0. For more details, see the full
141 text of the licenses in the directory LICENSES.
142 This program is distributed in the hope that it will be useful, but
144 without any warranty; without even the implied warranty of
145 merchantability or fitness for a particular purpose.
146perl v5.30.1 2020-02-10 PPIx::Regexp::Token::Modifier(3)