public function valuesExpr($expression) {
		$args = func_get_args();
		$this->expression = array_shift($args);
		
		if (empty($args))
			return $this;
		
		//check if argument is a list
		try {
			$this->valuesArray($args[0]);
		}
		catch (\InvalidArgumentException $e) {
			$this->valueList = $args;
		}
		
		return $this;
	}