/**
* 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);
}
/**
* Merge recursively.
* Please, see self::mergeTree() to know the context.
*
* @param \Hoa\Compiler\Llk\TreeNode $node Node that receives.
* @param \Hoa\Compiler\Llk\TreeNode $newNode Node to merge.
* @return void
*/
protected function mergeTreeRecursive(TreeNode $node, TreeNode $newNode)
{
$nNId = $newNode->getId();
if ('token' === $nNId) {
$node->appendChild($newNode);
$newNode->setParent($node);
return;
}
$children = $node->getChildren();
end($children);
$last = current($children);
if ($last->getId() !== $nNId) {
$node->appendChild($newNode);
$newNode->setParent($node);
return;
}
foreach ($newNode->getChildren() as $child) {
$this->mergeTreeRecursive($last, $child);
}
return;
}