try.t

#!perl
use strict;
use warnings;
use 5.010;
use Data::Dumper;
use Marpa::R2;

# This grammar tries to be equivalent to a PEG or Regex with ordered choice:
# List: Item*
# Item: VAR = VAR // VAR = // VAR
# In order to force that "order", this grammar specifies "rank"s.
# This seems to fail because ranks are not evaluated left-to-right?
use constant BNF => <<'BNF';
  :default ::= bless => ::lhs
  :discard ~ ws; ws ~ [\s]+
  
  List ::=
  List ::= List2
  List2 ::= List1 rank => 1
  List2 ::= List1 Item
  List1 ::= Item rank => 1
  List1 ::= Item Item
  Item ::= VAR '=' VAR
  Item ::= VAR '='
  Item ::= VAR
  VAR ~ [\w]+
BNF

my $g = Marpa::R2::Scanless::G->new({ source => \BNF, bless_package => 'main' });

local $Data::Dumper::Terse = 1;

sub all_parses {
  my ($input) = @_;
  my $r = Marpa::R2::Scanless::R->new({ grammar => $g, ranking_method => 'high_rule_only' });
  $r->read(\$input);
  say "Input: $input";
  my $i = 0;
  while (my $value_ref = $r->value()) {
    $i++;
    say "Parse $i: ", Data::Dumper::Dumper($value_ref);
  }
  return $i;
}

all_parses("a = b");
# expected: List(Item(a = b))
# actual 1: List(Item(a = b))
# actual 2: List(Item(a =) Item(b))

all_parses("a = b c");
# expected: List(Item(a = b) Item(c))
# actual 1: List(Item(a = b) Item(c))
# actual 2: List(Item(a =) Item(b) Item(c))

all_parses("a = b c = d");
# expected: List(Item(a = b) Item(c = d))
# actual 1: List(Item(a = b) Item(c = d))
# actual 2: List(Item(a =) Item(b) Item(c = d)
# but not this one??? List(Item(a = b) Item(c =) Item(d)) ??