Name
Data::DFA - Deterministic finite state parser from regular expression
Synopsis
Create a deterministic finite state parser to recognize sequences of symbols that match a given regular expression.
To recognize sequences of symbols drawn from 'a'..'e' that match the regular expression: a (b|c)+ d? e:
# Construct a deterministic finite state automaton from the regular expression:
use Data::DFA qw(:all);
use Data::Table::Text qw(:all);
use Test::More qw(no_plan);
my $dfa = fromExpr
(element("a"),
oneOrMore(choice(element("b"), element("c"))),
optional(element("d")),
element("e")
);
ok $dfa->parser->accepts(qw(a b e));
ok !$dfa->parser->accepts(qw(a d));# Print the symbols used and the transitions table:
is_deeply ['a'..'e'], [$dfa->symbols];
ok $dfa->print("Dfa for a(b|c)+d?e :") eq nws <<END;
Dfa for a(b|c)+d?e :
State Final Symbol Target Final
1 0 a 1 3 0
2 1 2 3 4 5 6 0 b 1 2 3 4 5 6 0
3 c 1 3 4 5 6 0
4 d 6 0
5 e 7 1
6 1 3 0 b 1 2 3 4 5 6 0
7 c 1 3 4 5 6 0
8 1 3 4 5 6 0 b 1 2 3 4 5 6 0
9 c 1 3 4 5 6 0
10 d 6 0
11 e 7 1
12 6 0 e 7 1
END# Create a parser and use it to parse a sequence of symbols
my $parser = $dfa->parser; # New parser
eval { $parser->accept($_) } for qw(a b a); # Try to parse a b a
say STDERR $@; # Error message
# Already processed: a b
# Expected one of : b c d e
# But was given : a
is_deeply [$parser->next], [qw(b c d e)]; # Next acceptable symbol
is_deeply $parser->processed, [qw(a b)]; # Symbols processed
ok !$parser->final; # Not in a final stateDescription
Deterministic finite state parser from regular expression
Version "20181027".
The following sections describe the methods in each functional area of this module. For an alphabetic listing of all methods by name see Index.
Index
Installation
This module is written in 100% Pure Perl and, thus, it is easy to read, comprehend, use, modify and install via cpan:
sudo cpan install Data::DFAAuthor
Copyright
Copyright (c) 2016-2018 Philip R Brenan.
This module is free software. It may be used, redistributed and/or modified under the same terms as Perl itself.