Simple Marpa events example

events_example.pl

use 5.010;
use strict;
use warnings;
use Data::Dumper; 
use English qw( -no_match_vars );
use Marpa::R2;
 
my $rules = <<'END_OF_GRAMMAR';
:start ::= sequence
sequence ::= FIRST SECOND
    action => OK
FIRST ::= A B C D E F G
SECOND ::= H I J K L
A ::= 'a'
B ::= 'b'
C ::= 'c'
D ::= 'd'
E ::= 'e'
F ::= 'f'
G ::= 'g'
H ::= 'h'
I ::= 'i'
J ::= 'j'
K ::= 'k'
L ::= 'l'
 
event 'FIRST' = completed FIRST
event 'SECOND' = completed SECOND
END_OF_GRAMMAR
  
my %pos_by_event = ();
my @events;

my $grammar = Marpa::R2::Scanless::G->new( { source => \$rules } );
my $string = "abcdefghijkl";
my $actual_events = [];
my $slr = Marpa::R2::Scanless::R->new({ grammar => $grammar, semantics_package => 'My_Actions' } );

my $length = length $string;
my $pos    = $slr->read( \$string );
READ: while (1) {
  my @current_events = ();
  EVENT:
  for my $event ( @{ $slr->events() } ) {
    my ($name) = @{$event};
    push @current_events, $name;
  }
 if (@current_events) {
      push @$actual_events, [$pos, @current_events];
  }
  last READ if $pos >= $length;
  $pos = $slr->resume($pos);
} ## end READ: while (1)
my $value_ref = $slr->value();
if ( not defined $value_ref ) {
  die "No parse\n";
}
my $actual_value = ${$value_ref};
print STDERR "Actual value: $actual_value\n";
print STDERR "Actual events: ",Dumper($actual_events);


sub My_Actions::OK { return 1792 };