Return the name associated with the node (if any).

Return the operator associated with a Node (if any)

Return the pfmc of a node (if any)

Accept the visitor.

This method tells the node to add its argument to the node's list of children.

This method is called after all the child nodes have been added.

This method returns a child node. The children are numbered from zero, left to right.

Return the number of children the node has.

This method is called after the node has been made the current node. It indicates that child nodes can now be added to it.

This pair of methods are used to inform the node of its parent.