/**
* Compares this binary tree with the specified comparable object.
* The specified comparable object is assumed to be a BinaryTree instance.
*
* @param object IComparable $obj
* The comparable object with which to compare this
* binary tree.
* @return integer A number less than zero if this binary tree is less
* than the specified binary tree;
* greater than zero if this binary tree is greater
* than the specified binary tree;
* zero if the two trees are identical.
*/
protected function compareTo(IComparable $obj)
{
if ($this->isEmpty()) {
return $obj->isEmpty() ? 0 : -1;
} elseif ($obj->isEmpty()) {
return 1;
} else {
$result = $this->getKey()->compare($obj->getKey());
if ($result == 0) {
$result = $this->getLeft()->compare($obj->getLeft());
}
if ($result == 0) {
$result = $this->getRight()->compare($obj->getRight());
}
return $result;
}
}
