The ICallbackEvaluation type exposes the following members.
Performs some special evaluation on the node. This method has the responsibility for evaluating the children of the node and it should generally call pv.eval(node.jjtGetChild(i)) for each child.
The SymbolTable is not passed as an argument. This is because it is better practice to get and set variable values by using node.GetVar().SetValue() rather that through the SymbolTable with requires a hashtable lookup.