3. In the object-oriented approach to the Core interpreter (where we had separate classes corresponding to the various non-terminals in the grammar), we took advantage of an opportunity that used the static mechanism to deal with identifiers. What did use of this mechanism enable us to do? In other words, why did we use this mechanism? Why didnt we use the static mechanism in the previous approach to the interpreter (where we had a single ParseTree class)? Explain.

4. In languages such as C++ and Java, static methods of a class are not allowed to access, through the implied receiver object formal parameter, this, instance variables of the class. Why is this? Explain.