Marpa::R2 2.020000

Marpa parses any language whose grammar can be written in BNF. That includes recursive grammars, infinitely ambiguous grammars, ambiguous grammars and grammars with useless or empty productions.

Marpa's advanced features, and full reference details of all features, can be found in the other Marpa API documents.

SYNOPSIS

 use Marpa::R2;

 my $grammar = Marpa::R2::Grammar->new(
 { start => 'Expression',
 actions => 'My_Actions',
 default_action => 'first_arg',
 rules => [
 { lhs => 'Expression', rhs => [qw/Term/] },
 { lhs => 'Term', rhs => [qw/Factor/] },
 { lhs => 'Factor', rhs => [qw/Number/] },
 { lhs => 'Term', rhs => [qw/Term Add Term/], action => 'do_add' },
 { lhs => 'Factor',
 rhs => [qw/Factor Multiply Factor/],
 action => 'do_multiply'
 },
 ],
 }
 );

 $grammar->precompute();

 my $recce = Marpa::R2::Recognizer->new( { grammar => $grammar } );

 $recce->read( 'Number', 42 );
 $recce->read( 'Multiply', );
 $recce->read( 'Number', 1 );
 $recce->read( 'Add', );
 $recce->read( 'Number', 7 );

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

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

 sub My_Actions::first_arg { shift; return shift; }

 my $value_ref = $recce->value;
 my $value = $value_ref ? ${$value_ref} : 'No Parse';


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Requirements:

· Perl