asf_per_traversal.t

use 5.010;
use strict;
use warnings;

use Data::Dumper;

use Marpa::R2;

my $g = Marpa::R2::Scanless::G->new( { 
    bless_package => 'main',
    source => \(<<'END_OF_SOURCE'),
:default ::= action => [values] bless => ::lhs
lexeme default = action => [value] bless => ::name

    seq ::= item+ separator => [,]
    item ~ 'item'

:discard ~ whitespace
whitespace ~ [\s]+
END_OF_SOURCE
} );

for my $input ('item, item'){
    my $r = Marpa::R2::Scanless::R->new( { grammar => $g } );
    $r->read(\$input);
    use Marpa::R2::ASF;
    my $asf = Marpa::R2::ASF->new( { slr => $r } );
    say $asf->traverse( { 'grammar' => $g }, \&generic_traverser );
}

sub generic_traverser{
    
    # convert the glade into string
    my ($glade, $scratch)     = @_;
    my $rule_id     = $glade->rule_id();
    my $symbol_id   = $glade->symbol_id();

   say $scratch->{grammar};
   my $symbol_name = $scratch->{grammar}->symbol_name($symbol_id);

    # token is a single choice, and we know enough to return it
    if ( not defined $rule_id ) {
        my $literal = $glade->literal();
        return "$literal";
    }

    my $length = $glade->rh_length();
    my @return_value = map { $glade->rh_value($_) } 0 .. $length - 1;

    # Special case for the start rule
    return (join q{ }, @return_value) . "\n" if  $symbol_name eq '[:start]' ;

    return "<$symbol_name: " . ( join q{ }, @return_value ) . ">";
}