protected function castArray($value, TypeHandler $typeHandler, $join_string = ',') {
		$list = [];
	
		//build expression list
		foreach ($value as $val) {
			$val = $typeHandler->castParameter($val);
	
			if (is_null($val))
				$new_elem = 'NULL';
			else {
				$new_elem = $typeHandler->setParameter($val);
				if (is_null($new_elem))
					$new_elem = 'NULL';
				elseif (!is_string($new_elem))
					$new_elem = strval($new_elem);
			}
				
			$list[] = $new_elem;
		}
	
		//return joined expression
		return implode($join_string, $list);
	}