For MP4:

Exercise 3.38: [*]
Extend the lexical address translator to handle cond from exercise 3.12.

This question is correctly marked with a single star. Can you write the
lexical address translator in such a way, called structure-shy, that this exercise disappears?
In the new solution, all you need is to add an additional alternative CondExp
to Exp in the class dictionary:

Exp : ... | CondExp.
CondExp = "cond" List(CondElement) "end".
CondElement = <lhs> Exp "==>" <rhs> Exp.

No other changes should be needed in your structure-shy solution.

In this exercise you don't have to write such a program. 
But you should identify constructs that your programming language should have so that
you can program in a structure-shy manner.
You have already seen many programming language extensions in this course.
In this exercise we look for extension needed for structure-shy programming.
How would you extend Scheme? How would you extend one of the languages covered in EOPL?

It is important to recognize that for the lexical address computation, a CondExp is
just a consumer but not a producer that influences the lexical
address computation. All we need to do in the CondExp is to find all the bound variables
and replace them by a lexical address.
The same can be said of an application: 
we need to traverse to all bound variables in the rator and rand
and replace them by a lexical address.
Once you have a structure-shy solution, it will be easy to add new constructs to the language
provided they are consumers in the sense described above.

Turn in a list of constructs you would need and an informal program that uses those
constructs to solve the problem in a structure-shy way.

Hint: We have already done a structure-shy solution for the occurs-free problem.