private function visitString(TreeNode $node)
{
$tokens = array();
foreach ($node->getChildren() as $child) {
$value = $child->getValue();
if ($value === null || !isset($value['value'])) {
throw new InvalidArgumentException(sprintf('A token node was expected, got "%s".', $child->getId()));
}
$tokens[] = $value['value'];
}
return implode($tokens);
}
private function leftRotateTree(TreeNode &$root)
{
// Pivot = Root.Left
$pivot = $root->getChild(1);
// Root.Right = Pivot.Left
$children = $root->getChildren();
$children[1] = $pivot->getChild(0);
// Pivot, rotation side
$root->setChildren($children);
// Pivot.Left = Root
$children = $pivot->getChildren();
$children[0] = $root;
$pivot->setChildren($children);
// Root = Pivot
$root = $pivot;
}
