NAME
MarpaX::ESLIF::Symbol - MarpaX::ESLIF's symbol
VERSION
version 6.0.35.1
SYNOPSIS
use MarpaX::ESLIF;
my $eslif = MarpaX::ESLIF->new();
my $stringSymbol = MarpaX::ESLIF::Symbol->new($eslif, type => 'string', pattern => '"String Pattern"');
#
# In ESLIF, a regex is anchored by default
#
my $regexSymbol = MarpaX::ESLIF::Symbol->new($eslif, type => 'regex', pattern => 'Regex.*Pattern', modifiers => 'A');
my $metaSymbol = MarpaX::ESLIF::Symbol->new($eslif, type => 'meta',
grammar => MarpaX::ESLIF::Grammar->new(
$eslif,
"<something> ::= <SOMETHING>\n<SOMETHING> ~ 'that'"),
symbol => 'SOMETHING');
#
# For regex, a substitution pattern is supported
#
my $substitutionSymbol = MarpaX::ESLIF::Symbol->new($eslif, type => 'regex', pattern => 'Regex(.*)Pattern', modifiers => 'A', substitutionPattern => '$1', substitutionModifiers => 'g');
if (defined(my $match = $stringSymbol->try('String Pattern here'))) {
print "==> String match: $match\n";
}
if (defined(my $match = $regexSymbol->try('Should match Regex etc Pattern in there'))) {
print "==> Regex match: $match\n";
}
if (defined(my $match = $metaSymbol->try('something'))) {
print "==> Meta match: $match\n";
}
if (defined(my $match = $substitutionSymbol->try('Should match Regex etc Pattern in there'))) {
print "==> Meta match: $match\n";
}External symbols can be of type string, regex or meta. They can be used agains a MarpaX::ESLIF::Recognizer or any external input.
A string pattern must follow ESLIF)s BNF, i.e. start and ends with:
'(single quote) character"(double quote) character“(LEFT DOUBLE QUOTATION MARK) and”characters (RIGHT DOUBLE QUOTATION MARK), respectively
A meta symbol must be a lexeme in the given external grammar.
DESCRIPTION
MarpaX::ESLIF::Symbol allows to create external symbols on demand
METHODS
MarpaX::ESLIF::Symbol->new($eslif, %options)
Returns a symbol instance, noted $symbol later. %options is a hash that contains:
type-
Value must be "string", "regex" or "meta". Required.
pattern-
Value is the pattern content. Required for "string" and "regex" types.
encoding-
Value is the pattern encoding. Optional for "string" and "regex" types.
modifiers-
Value is a string containing modifiers. Optional for "string" and "regex" types.
It must follow the specification of the Terminals section of MarpaX::ESLIF::BNF:
---------------------------------------------------------------- Modifiers Explanation ---------------------------------------------------------------- e Unset back-references in the pattern will match to empty strings i Case-insensitive j \u, \U and \x and unset back-references will act as JavaScript standard m Multi-line regex n Enable Unicode properties and extend meaning of meta-characters s A dot meta-character in the pattern matches all characters, including newlines x Enable comments. This has some limitation due marpaESLIF semantics D A dollar meta-character matches only at the end of the subject string J Allow duplicate names for sub-patterns U Inverts the "greediness" of the quantifiers a Meta-characters will be limited to their ASCII equivalent u Forces support of large codepoints b Could mean "forced binary" mode c Could mean "forced unicode character" mode A Remove the systematic anchoring ----------------------------------------------------------------Note that a string pattern accepts only the
iandcmodifiers. substitutionPattern-
Value is the substitution content, writen as if this was an ESLIF string. Optional and supported only for "regex" type. If set, it is assumed that it is in the same encoding as
pattern. substitutionModifiers-
Value is a string containing substitution modifiers. Optional and supported only for "regex" type.
It must follow the substitution specification of the Terminals section of MarpaX::ESLIF::BNF:
---------------------------------------------------------------- Modifiers PCRE2 flag unset PCR2 flag set ---------------------------------------------------------------- x PCRE2_SUBSTITUTE_EXTENDED g PCRE2_SUBSTITUTE_GLOBAL l PCRE2_SUBSTITUTE_LITERAL ! PCRE2_SUBSTITUTE_UNKNOWN_UNSET f PCRE2_SUBSTITUTE_UNSET_EMPTY ---------------------------------------------------------------- grammar-
Value is an external grammar. Required for "meta" type.
symbol-
Value is a lexeme in the external grammar. Required for "meta" type.
$symbol->try($eslif, $scalar)
Try to match the external symbol $symbol on $scalar, that can be anything. Return undef if failure, the matched string if success.
SEE ALSO
MarpaX::ESLIF, MarpaX::ESLIF::Recognizer
AUTHOR
Jean-Damien Durand <jeandamiendurand@free.fr>
COPYRIGHT AND LICENSE
This software is copyright (c) 2017 by Jean-Damien Durand.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.