A class that knows how to walk down the tree. None of the individual visit methods are implemented on this visitor, so it forces the consumer to implement each one that they need. For a default implementation that continues walking the tree, see the Visitor class.

Instance Methods

Calls ‘accept` on the given node if it is not `nil`, which in turn should call back into this visitor by calling the appropriate `visit_*` method.

Visits each node in ‘nodes` by calling `accept` on each one.

Visits the child nodes of ‘node` by calling `accept` on each one.