Parsing a JSON string with Marpa.

test-string-parse.pl

use strict;
use Marpa::R2;

my $g = Marpa::R2::Scanless::G->new({
        action_object  => 'main',
        default_action => 'do_first_arg',
        source         => \(<<'END_OF_SOURCE'),

:start        ::= string

string          ~ '"' in_string '"'
in_string       ~ in_string_char*
in_string_char  ~ [^"\\]
                | '\"'
                #| [\\] '"'
                | [\\] 'b'
                | [\\] 'f'
                | [\\] 't'
                | [\\] 'n'
                | [\\] 'r'
                | [\\] 'u' four_hex_digits
                | [\\] '/'
                | [\\] [\\]                   # \\ (1)
                | '\\'                        # \\ (2)
                | [\x{005c}] [\x{005c}]       # \\ (3)

four_hex_digits ~ hex_digit hex_digit hex_digit hex_digit
hex_digit       ~ [0-9a-fA-F]

:discard        ~ ws
ws              ~ [\s]+

END_OF_SOURCE
});

my $string = <<'INPUT';
"hello world\\\""
INPUT

my $re = Marpa::R2::Scanless::R->new({ grammar => $g });
$re->read(\$string);
my $res = $re->value;
print $$res;

sub new {
    return bless {}, 'main';
}
sub do_first_arg { shift; return $_[0]; }