/ 
Grammar-Marpa-1.000
River stage zero No dependents
/ Grammar::Marpa

NAME

Grammar::Marpa - No-frills overload wrapper around Marpa::R2::Scanless

VERSION

Version 1.000

SYNOPSIS

use Grammar::Marpa;

my $dsl = <<'END_OF_DSL';
:default ::= action => ::first
:start ::= Expression
Expression ::= Term
Term ::= Factor
       | Term '+' Term action => do_add
Factor ::= Number
         | Factor '*' Factor action => do_multiply
Number ~ digits
digits ~ [\d]+
:discard ~ whitespace
whitespace ~ [\s]+
END_OF_DSL

sub M::do_add {
    my (undef, $t1, undef, $t2) = @_;
    return $t1 + $t2;
}

sub M::do_multiply {
    my (undef, $t1, undef, $t2) = @_;
    return $t1 * $t2;
}

my $g = Grammar::Marpa($dsl, 'M');

'1 + 2 * 3' =~ $g;

say $^R; # '7'

DESCRIPTION

This module provides a quick & dirty interface to the very basics of Marpa::R2's Scanless interface, including overloading the '=~' operator in a way that is only slightly inconvenient.

CONSTRUCTORS

Grammar::Marpa(GRAMMAR, PACKAGE)

Create a new grammar object, based on a well-formed SLIF EBNF grammar (which must be provided as a scalar string) and using the specified package to provide the semantics of the grammar.

USAGE

'=~'

Once you have a grammar object, you can parse a string by performing

$string =~ $grammar;

$^R

Once you have parsed a string with a grammar object, the $^R variable will contain the value of the last parse.