in reply to Using qw to check for balanced parentheses

It took a long time and didn't give me the right answer for some reason: 

Is  );system('rm -rf /');# balanced? ~$#& NO CARRIER

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Update: While I was trying to get back into that server I whipped up how I'd do this: 

sub balanced {
    my( $str )= @_;
    my $d= 0;
    while(  $str =~ m(([(])|([)]))g  ) {
        if(  $1  ) {
            $d++;
        } elsif(  --$d < 0  ) {
            return 0;
        }
    }
    return 0 == $d;
}

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- tye        

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Re^2: Using qw to check for balanced parentheses (oops)
by jdporter (Paladin) on Sep 16, 2011 at 19:06 UTC 
    sub balanced {
    local $_ = shift;
    s/[^()]//g;
    eval "qw($_)";
    ! $@
}

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[reply]
[d/l]

      Simplified return value and shortened code by avoiding needless use of $_: 

      sub balanced {
    (my $s = shift) =~ s/[^()]//g;
    eval "qw($s); 1"
}

      [download]

      Or in 5.14+: 

      sub balanced {
    my $s = shift =~ s/[^()]//rg;
    eval "qw($s); 1"
}

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[reply]
[d/l]
[select]

        I may be mistaken, but this does not detect a case like

        "}a{"

        , or does it?

        how about

        sub balanced {
    (my $s = shift) =~ s/[^()]//g;
    while ( $s =~s /\(\)// ){};
    return $s ? 0 : 1;
}

        [download]
        It does not use qr and is slower, I would think, but reports '}{' as incorrect
[reply]
[d/l]

      Very nice!

      - tye        

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In Section Cool Uses for Perl