/**
* Determine if $node is in fact a unary operator.
*
* If $node can be a unary operator (i.e. is a '+' or '-' node),
* **and** this is the first node we parse or the previous node
* was a SubExpressionNode, i.e. an opening parenthesis, or the
* previous node was already a unary minus, this means that the
* current node is in fact a unary '+' or '-' and we return true,
* otherwise we return false.
*
* @param Node $node Current node
* @param Node|null $lastNode Previous node handled by the Parser
* @retval boolean
*/
protected function isUnary($node, $lastNode)
{
if (!$node->canBeUnary()) {
return false;
}
// Unary if it is the first token
if ($this->operatorStack->isEmpty() && $this->operandStack->isEmpty()) {
return true;
}
// or if the previous token was '('
if ($lastNode instanceof SubExpressionNode) {
return true;
}
// or last node was already a unary minus
if ($lastNode instanceof ExpressionNode && $lastNode->getOperator() == '~') {
return true;
}
return false;
}
