Re: Parsing Boolean expressions

[choroba]

I like Marpa::R2 for building grammars:

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Marpa::R2;

my $dsl = << '__DSL__';

lexeme default = latm => 1

Assignment ::= var ('=') Expression         action => ASSIGN
Expression ::= var                          action => VAR
             | ('(') Expression (')')       action => ::first  assoc  
+=> group
            || Expression (q)               action => NOT
            || Expression ('*') Expression  action => AND
            || Expression ('+') Expression  action => OR

q          ~ [']
var        ~ [A-Z]+
:discard   ~ whitespace
whitespace ~ [\s]+

__DSL__

my %var;


sub ASSIGN { $var{ $_[1] } = 0 + $_[2] }
sub NOT    { ! $_[1] }
sub AND    { $_[1] && $_[2] }
sub OR     { $_[1] || $_[2] }
sub VAR    { $var{ $_[1] } }

my @input = ('Y = A + (B*C)',
             "Y = A + (B' + (C*D)')",
             "Y = A*(B*(C'+D)')");

my $grammar = 'Marpa::R2::Scanless::G'->new({ source => \$dsl });
for my $line (@input) {
    %var = map +( $_ => int rand 2 ), 'A' .. 'D';
    my $result = $grammar->parse(\$line, { semantics_package => 'main'
+ });
    say join ' ', %var;
}