protected function calculateIndex( $list, $search, $lowbound, $highbound )
	{
		$spanIndex	= $list[$highbound] - $list[$lowbound];
		$spanValues	= $highbound - $lowbound;
		$spanDiff	= $search - $list[$lowbound];
		$index		= $lowbound + round( $spanValues * ( $spanDiff / $spanIndex ) );
		return $index;
	}