Re: Adding 2 + 2

[mr_mischief]

I didn't notice anyone using Roman numerals. I tested the applicable subroutine with lots of values, since I wrote it for this and hadn't used it before. If there are any bugs with it other than the design decision documented, please let me know. This might actually sneak into a project since I spent a good half hour designing, coding, testing, and commenting it.

Chris

$x = 'ii';
$y = 'ii';

sub Roman {

=pod
    This doesn't check for validity, as the
    subtraction rule is always honored, even
    for I before M if you want to do that.
    Roman numerals generally allow I only before
    V or X for the subtraction rule, X before
    an L or a C, and C before a D or an M.

    If you need to check validity, it'd be a
    task suitable for a separate sub since
    this one should be able to handle horked
    but workable values by design, just in
    case. Heck, this doesn't even check for
    the existence of invalid characters. It
    just ignores them.
=cut

    my $z = 0;
    my @foo = uc(shift) =~ /(M+|D+|C+|L+|X+|V+|I+)/g;
    my %value = (
        'M' => 1000,
        'D' => 500,
        'C' => 100,
        'L' => 50,
        'X' => 10,
        'V' => 5,
        'I' => 1,
    );
    for ( my $i = 0; $i < scalar @foo; $i++ ) {
        my $ch = substr $foo[$i], 0, 1;
        my $v = $value{$ch};
        my $nxt_ch = '';
        my $nxt_v = -1;
        if ( defined ( $foo[$i + 1] ) ) {
            $nxt_ch = substr( $foo[$i + 1], 0, 1 );
            $nxt_v = $value{$nxt_ch};
        }
        foreach ( 1..length $foo[$i] ) {
            if ( $nxt_v > $v ) {
                $z -= $value{$ch};
            } else {
                $z += $value{$ch};
            }
         }
    }
    return $z;
}

printf "The result is: %d\n", (Roman $x) + (Roman $y);

[Juerd]

A very creative solution :)
Be sure to check out Roman if you didn't know it already. It can convert roman numbers both ways, and checks if your roman input is valid.



use Roman;
$calc = "II + II";
$calc =~ s/([MDCLXVI]+)/isroman($1) ? arabic($1) : $1/;
print eval $calc;

2;0 juerd@ouranos:~$ perl -e'undef christmas'
Segmentation fault
2;139 juerd@ouranos:~$

[mr_mischief]

Thanks for the review and the suggestion.

I knew Roman was available, but it didn't feel right to use it for this. I felt it was more in the spirit of the thread to go overboard and develop the needed tools specifically for the node. I'm actually a bit surprised it took someone posting a hand-crafted Roman to Arabic numeral conversion before someone gave an example using the module. It was one of the first twists on the problem that popped into my deranged mind.

[ambrus]

It's a bit late to ask, but did you enter this to the Fonalty Perl Golf Challenge?

[mr_mischief]

I didn't know about the contest until just now. Thanks for asking, though. I'm enjoying looking at the site.