If you have not completed exercise 8.2+8.6 from last Friday, you
should complete that. This exercise is important as it trains you in
using recursive datatypes to represent expression trees (abstract
syntax for language elements) -- an important application area.

Exercise 8.5 trains you in using recursive datatype
declarations to represent other kinds of trees than expression trees.

Exercise 8.8 trains you in using abstract data types. The problem is
the same as in exercise 6.1 (which is the same as "Programming
Exercise 2" that you solved in the very first exercise session),
but now you have to use an abstract data type declaration for
polynomials. So take your old solution and revise it.

Exercise 8.4 trains you in using recursive datatypes in the
application area of logic and points to topics that will be covered in
the other (logic) track of this course.
The exercise gives you the
challenge of making such a useful tool as a tautology checker.