public function partitionFacts( $variableSet )
	{
		if ( ! $this->var->bindAsSequence ) return;

		$groups = array();

		// This is a bit belt-and-braces but just to be sure
		if ( $this->facts instanceof XPath2NodeIterator )
		{
			$groups[] = $this->facts->CloneInstance();
		}
		else if ( is_array( $this->facts ) )
		{
			$groups[] = DocumentOrderNodeIterator::fromItemset( $this->facts, true );
		}
		else
		{
			$groups[] = DocumentOrderNodeIterator::fromItemset( array( $this->facts ) );
		}

		$this->facts = DocumentOrderNodeIterator::fromItemset( $groups );
	}