protected function foldConstantXPathExpression(array $m)
	{
		$expr = $m[0];
		if ($this->isConstantExpression($expr))
		{
			$result = $this->evaluate($expr);
			if ($this->canBeSerialized($result))
			{
				$foldedExpr = XPath::export($result);
				if (strlen($foldedExpr) < strlen($expr))
				{
					$expr = $foldedExpr;
				}
			}
		}

		return $expr;
	}