PPIx::Regexp::Token::Modifier(3)
NAME
PPIx::Regexp::Token::Modifier - Represent modifiers.
SYNOPSIS
use PPIx::Regexp::Dumper;
PPIx::Regexp::Dumper->new( 'qr{foo}smx' )
->print();
The trailing "smx" will be represented by this class.
This class also represents the whole of things like "(?ismx)". But the
modifiers in something like "(?i:foo)" are represented by a
PPIx::Regexp::Token::GroupType::Modifier.
INHERITANCE
"PPIx::Regexp::Token::Modifier" is a PPIx::Regexp::Token.
"PPIx::Regexp::Token::Modifier" is the parent of
PPIx::Regexp::Token::GroupType::Modifier.
DESCRIPTION
This class represents modifier characters at the end of the regular
expression. For example, in "qr{foo}smx" this class would represent
the terminal "smx".
The "a", "aa", "d", "l", and "u" modifiers
The "a", "aa", "d", "l", and "u" modifiers, introduced starting in Perl
5.13.6, are used to force either Unicode pattern semantics ("u"),
locale semantics ("l") default semantics ("d" the traditional Perl
semantics, which can also mean 'dual' since it means Unicode if the
string's UTF-8 bit is on, and locale if the UTF-8 bit is off), or
restricted default semantics ("a"). These are mutually exclusive, and
only one can be asserted at a time. Asserting any of these overrides
the inherited value of any of the others. The "asserted()" method
reports as asserted the last one it sees, or none of them if it has
seen none.
For example, given "PPIx::Regexp::Token::Modifier" $elem representing
the invalid regular expression fragment "(?dul)", "$elem->asserted( 'l'
)" would return true, but "$elem->asserted( 'u' )" would return false.
Note that "$elem->negated( 'u' )" would also return false, since "u" is
not explicitly negated.
If $elem represented regular expression fragment "(?i)",
"$elem->asserted( 'd' )" would return false, since even though "d"
represents the default behavior it is not explicitly asserted.
The caret ("^") modifier
Calling "^" a modifier is a bit of a misnomer. The "(?^...)"
construction was introduced in Perl 5.13.6, to prevent the inheritance
of modifiers. The documentation calls the caret a shorthand equivalent
for "d-imsx", and that it the way this class handles it.
For example, given "PPIx::Regexp::Token::Modifier" $elem representing
regular expression fragment "(?^i)", "$elem->asserts( 'd' )" would
return true, since in the absence of an explicit "l" or "u" this class
considers the "^" to explicitly assert "d".
The caret handling is complicated by the fact that the 'n' modifier was
introduced in 5.21.8, at which point the caret became equivalent to
"d-imnsx". I did not feel I could unconditionally add the "-n" to the
expansion of the caret, because that would produce confusing output
from methods like explain(). Nor could I make it conditional on the
minimum perl version, because that information is not available early
enough in the parse. What I did was to expand the caret into "d-imnsx"
if and only if 'n' was in effect at some point in the scope in which
the modifier was parsed.
Continuing the above example, "$elem->asserts( 'n' )" and
"$elem->modifier_asserted( 'n' )" would both return false, but
"$elem->negates( 'n' )" would return true if and only if the "/m"
modifier has been asserted somewhere before and in-scope from this
token. The modifier_asserted( 'n' ) method is inherited from
PPIx::Regexp::Element.
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.
asserts
$token->asserts( 'i' ) and print "token asserts i";
foreach ( $token->asserts() ) { print "token asserts $_\n" }
This method returns true if the token explicitly asserts the given
modifier. The example would return true for the modifier in "(?i:foo)",
but false for "(?-i:foo)".
Starting with version 0.036_01, if the argument is a single-character
modifier followed by an asterisk (intended as a wild card character),
the return is the number of times that modifier appears. In this case
an exception will be thrown if you specify a multi-character modifier
(e.g. 'ee*').
If called without an argument, or with an undef argument, all modifiers
explicitly asserted by this token are returned.
match_semantics
my $sem = $token->match_semantics();
defined $sem or $sem = 'undefined';
print "This token has $sem match semantics\n";
This method returns the match semantics asserted by the token, as one
of the strings 'a', 'aa', 'd', 'l', or 'u'. If no explicit match
semantics are asserted, this method returns "undef".
modifiers
my %mods = $token->modifiers();
Returns all modifiers asserted or negated by this token, and the values
set (true for asserted, false for negated). If called in scalar
context, returns a reference to a hash containing the values.
negates
$token->negates( 'i' ) and print "token negates i\n";
foreach ( $token->negates() ) { print "token negates $_\n" }
This method returns true if the token explicitly negates the given
modifier. The example would return true for the modifier in
"(?-i:foo)", but false for "(?i:foo)".
If called without an argument, or with an undef argument, all modifiers
explicitly negated by this token are returned.
SUPPORT
Support is by the author. Please file bug reports at
<http://rt.cpan.org>, or in electronic mail to the author.
AUTHOR
Thomas R. Wyant, III wyant at cpan dot org
COPYRIGHT AND LICENSE
Copyright (C) 2009-2019 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.
perl v5.28.1 2019-04-04 PPIx::Regexp::Token::Modifier(3)
ppix-regexp 0.64.0 - Generated Thu Apr 4 19:23:06 CDT 2019