protected function expand_format_expression($format) {

		$increment = 1;

		if(strpos($format, '/') !== false) {
			list($format, $increment) = explode('/', $format, 2);
			$increment = ($increment === '*') ? 1 : (int) $increment;
		}

		$parts = explode('-', $format, 2);

		$start = array_shift($parts);
		$end = array_shift($parts);

		if($start === '*') $start = $this->min;
		if($end === null) $end = $this->max;

		$start = max($this->min, $start);
		$end = min($this->max, $end);

		if( ($end - $start) < $increment) return array($start);
		return range($start, $end, $increment);

	}