SWE/CS 332 In Class Exercise # 8


Name(s):
Consider Liskov's IntSet.java class.
  1. Derive the abstraction function and the rep-invariant for this class. If you need a hint, Liskov has done exactly this on a closely related implementation.
  2. Weaken the rep-invariant by removing the prohibition on duplicates in the rep.
    Important: whether there are duplicates in the rep has nothing to do with whether there are duplicates in the abstract state - which there most definitely aren't since the abstract state is a set. Students often struggle with this - probably because they don't yet understand that the client state and the implementation state are truly distinct things. It's important to get it straight.
  3. The abstraction function does not change, but the the abstraction function must nonetheless be re-implemented. Explain this, and make it happen.
  4. Rewrite methods as needed for the new rep-invariant.