public function createNode(Node $left = null, Node $right = null, Node $middle = null)
{
$node = new OperatorNode($this);
if ($left) {
$node->addChild($left, OperatorNode::OPERAND_LEFT);
}
if ($middle) {
$node->addChild($middle, OperatorNode::OPERAND_MIDDLE);
}
if ($right) {
$node->addChild($right, OperatorNode::OPERAND_RIGHT);
}
return $node;
}
