Read "Clousot: Static Contract Checking with Abstract Interpretation" (focusing on their handling of
arrays, which is what we'll discuss in class) and "Lightweight Verification of Array Indexing".
Then, answer the following questions:

1. Explain the "pentagons" abstract domain in one sentence. Then, name one fact that it can express,
and one fact that it cannot.

2. Compare and contrast the way that Clousot combines domains and the multiple checkers of the
Index Checker. What is similar about the two, and what is different?

3. Consider the code in Figure 5 of the Clousot paper. Is there a set of Index Checker annotations
that would enable the Index Checker to prove that code correct? If so, what is it? If not, what
property is necessary to prove the code correct that the Index Checker cannot express?

4. Name one important design difference between the Index Checker and Clousot. What are the consequences
of that design decision (in terms of precision, recall, speed, or other properties of the analysis)?

5. Name one important design similarity between the Index Checker and Clousot. Why did both sets of
authors choose to structure their analysis that way (or, what might have gone wrong had they not
done what they did)?

6. What was the most confusing part of the reading? Is there anything you still don't understand?

7. How much time did you spend on this assignment (both the reading and answering the questions, combined)?