Transforming Syntax – Marpa parsing example

gistfile1.pl

use strict; use warnings; use 5.010;

use Data::Dumper;

my $data = <<'END';
If ((Myvalue.xyz == 1) Or (Frmae_1.signal_1 == 1)) Then a = 1
Else a = 0;
END

my $ast = Parser->parse(\$data);

print Dumper $ast;

# Below is a class that wraps the Marpa Parser

package Parser;

use Marpa::R2;

my ($grammar);

sub parse {
    my ($self, $ref) = @_;
    my $recce = Marpa::R2::Scanless::R->new({ grammar => $grammar });
    $recce->read($ref);
    my $val = $recce->value // die "No parse found";
    return $$val;
}

BEGIN {
    $grammar = Marpa::R2::Scanless::G->new({
        bless_package => 'Ast',
        source => \<<'END SOURCE',
            :default    ::= action => [values]
            :start      ::= StatementList
            :discard    ~   ws
            
            StatementList ::= <Expression>+ separator => <op semicolon> bless => Block
            
            Expression ::=
                    ('(') Expression (')')  assoc => group action => ::first
                |   Number                  bless => Literal
                ||   Ident                   bless => Var
                ||  Expression  '=='    Expression  bless => Binop
                ||  Expression  '='     Expression  bless => Binop
                ||  Expression  'Or'    Expression  bless => Binop
                ||  Conditional
                
            Conditional ::=
                    ('If') Expression ('Then') Expression
                        bless => Cond
                |   ('If') Expression ('Then') Expression ('Else') Expression
                        bless => Cond
                        
            Ident   ~ ident
            Number  ~ <number int> | <number rat>
                        
            word    ~ [\w]+
            ident   ~ word | ident '.' word
            <number int> ~ [\d]+
            <number rat> ~ <number int> '.' <number int>
            ws      ~ [\s]+
            <op semicolon> ~ ';'
END SOURCE
    });
}