xtc.tree

In contrast to the original visitor pattern, node visitors do not implement a fixed interface. Rather, the appropriate method is selected through reflection-based dynamic dispatch, based on the type of a node. On invocation of {@link xtc.tree.Visitor#dispatch}, the dynamic dispatch mechanism tries to find a method name visit() that takes either the specified node, any of its interfaces, or any of its superclaseses as its only argument. The search starts with the class of the node, then checks for all implemented interfaces, then for the superclass, then for all interfaces of the superclass, and so on until it reaches java.lang.Object, which is not considered.

For {@link xtc.tree.GNode generic nodes} the appropriate visit() method is selected based on the name of the generic node. For example, if the target name is Node, then the dynamic dispatch mechanism tries to locate a method visitNode(GNode). If no such method exists, the dynamic dispatch mechanism also tries to locate a visit(GNode) and visit(Node) method (in that order).

Note that to improve the performance of dynamic dispatch, our implementation uses a static method lookup cache that is not thread-safe. Source-to-source transformers thus cannot be multi-threaded.

A note on memory conservation: Generic nodes created through the GNode.create(String) or GNode.create(String,int) methods can have a variable number of children.