Re: Re: Now, how about Roman Numerals?

["Hugh Bothwell" <hugh_bothwell@hotmail.com>]

"George Pitcher" <george.pitcher@ingenta.com> wrote in message
HHEIKBOENJPJNLHFCCCCCEFOCGAA.george.pitcher@ingenta.com">news:HHEIKBOENJPJNLHFCCCCCEFOCGAA.george.pitcher@ingenta.com...
> That's great, but what about the reverse: Roman to Arabic?
>
> George in Oxford


// NOTE: the order of the table is
// important! I will use greedy parsing,
// so (for example) IX and IV must precede
// I to parse correctly.
$RomanTable = array(
    "M" => 1000,
    "CM" => 900,
    "D" => 500,
    "CD" => 400,
    "C" => 100,
    "XC" => 90,
    "L" => 50,
    "XL" => 40,
    "X" => 10,
    "IX" => 9,
    "V" => 5,
    "IV" => 4,
    "I" => 1
);

    function MatchClause($needle, $haystack) {
        // These two tests are probably just paranoia,
        // but - hey, I'm paranoid. ;-)
        if (strlen($haystack) < 1)
            return false;
        if (strlen($haystack) < strlen($needle))
            return false;

        return( strncasecmp($needle, $haystack, strlen($needle)) == 0 );
    }

    function RemoveClause($needle, $haystack) {
        return( substr($haystack, strlen($needle)) );
    }

function RomanToInt($str) {
    global $RomanTable;
    $sum = 0;

    do
    {
        $done = true;

        foreach($RomanTable as $clause => $value)
            if ( MatchClause($clause, $str) ) {
                $sum += $value;
                $str = RemoveClause($clause, $str);

                $done = false;
                break;
            }
    }
    while ($done == false);

    return($sum);
}



NOTE!  This algorithm is sufficient but not complete -
it will correctly translate all legal Roman-numeral strings,
but cannot detect illegal strings.


--
Hugh Bothwell     hugh_bothwell@hotmail.com     Kingston ON Canada
v3.1 GCS/E/AT d- s+: a- C+++ L++>+++$ P+ E- W+++$ N++ K? w++ M PS+
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