class ExpressionNode { ExpressionNode() { } String print(String indent) { return indent + "ExpressionNode(" + getClass().toString() + ")\n"; } void evalLHS(Environment theEnv) { System.out.println("Unimplemented evalLHS for " + print("")); } void eval(Environment theEnv) { System.out.println("Unimplemented eval for " + print("")); } }