Exam 1

3 Responses to Exam 1

1. mkd5m says:

   24 September 2010 at 12:47 pm

   For #4, in the overview of the MultiSet type, it states “where the set braces mean the collection is ordered.” Should this say unordered?
   • David Evans says:

     24 September 2010 at 5:18 pm

     Yes, that is a mistake. It collection is unordered. The multiset is an unordered bag of elements, where the same value can appear more than once.
2. David Evans says:

   27 September 2010 at 4:56 pm

   Several people have asked questions about the abstraction function for HashMap:

   private HashMap map;
   // Abstraction function:
   // AF(c) = { x_1, …, x_n } where
   // forall key: rep.map()
   // the value of key appears in x map.get(key) number of times.
   

   This is a bit confusingly worded since I didn’t define what “x” is here. By x, I mean the set { x_1, … , x_n} that is the abstract representation of the multiset. So, if say, map.get(3) = 7 then the value 3 (key) appears in this set (x) 7 times.