Re: Evaluate arbitrary boolean expressions

[choroba]

If you don't want to use eval for security purposes, write a parser. Marpa::R2 is a module that can help you with that:

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

use Marpa::R2;

my $dsl = << '__DSL__';

:default ::= action => ::first
lexeme default = latm => 1

Exp         ::= Term
              | Exp (disj) Term     action => disj
Term        ::= Factor
              | Term (conj) Factor  action => conj
Factor      ::= Atom
              | Negation
              | Bracketed
Bracketed   ::= (lbra) Exp (rbra)
Negation    ::= (excl) Factor       action => neg
Atom        ::= true                action => true
              | false               action => false

true  ~ 'T'
false ~ 'F'
excl  ~ '!'
conj  ~ '&&'
disj  ~ '||'
lbra  ~ '('
rbra  ~ ')'

ws    ~ [\s]+
:discard ~ ws

__DSL__

sub true   { 1 }
sub false  { 0 }
sub neg    { ! $_[1] }
sub conj   { $_[1] && $_[2] }
sub disj   { $_[1] || $_[2] }

my $grammar = 'Marpa::R2::Scanless::G'->new({source => \$dsl});

my $input = '((T) || (!(T))) && !(F && F && F && F && ! (T))';

my $value = ${ $grammar->parse(\$input, 'main') };

say $value ? 'TRUE' : 'FALSE';