/**
* Walks the tree to restore left-associativity of some operators
*
* @param TreeNode $root AST root node
*/
private function fixOperatorAssociativity(TreeNode &$root)
{
switch ($root->getChildrenNumber()) {
case 0:
// Leaf nodes can't be rotated, and have no childs
return;
case 2:
// We only want to rotate tree contained in the left associative
// subset of operators
$rootType = $root->getId();
if (!in_array($rootType, self::$leftAssociativeOperators)) {
break;
}
// Do not break operator precedence
$pivot = $root->getChild(1);
if ($pivot->getId() !== $rootType) {
break;
}
$this->leftRotateTree($root);
break;
}
// Recursively fix tree branches
$children = $root->getChildren();
foreach ($children as $index => $_) {
$this->fixOperatorAssociativity($children[$index]);
}
$root->setChildren($children);
}
private function assertChildrenCount(TreeNode $node, $count)
{
if ($node->getChildrenNumber() !== $count) {
throw new Exception(sprintf('Node was expected to have only %s children.', $count));
}
}
