public class PascalSet : IVisitableCollection<int>, ISet
{
      // Methods
      public PascalSet Difference(PascalSet set);
      public PascalSet Intersection(PascalSet set);
      public PascalSet Inverse();
      public bool IsEqual(PascalSet set);
      public bool IsProperSubsetOf(PascalSet set);
      public bool IsProperSupersetOf(PascalSet set);
      public bool IsSubsetOf(PascalSet set);
      public bool IsSupersetOf(PascalSet set);
      public static PascalSet operator +(PascalSet s1, PascalSet s2);
      public static bool operator >(PascalSet s1, PascalSet s2);
      public static bool operator >=(PascalSet s1, PascalSet s2);
      public static bool operator <(PascalSet s1, PascalSet s2);
      public static bool operator <=(PascalSet s1, PascalSet s2);
      public static PascalSet op_LogicalNot(PascalSet set);
      public static PascalSet operator *(PascalSet s1, PascalSet s2);
      public static PascalSet operator -(PascalSet s1, PascalSet s2);
      public PascalSet Union(PascalSet set);

      // ...

      // Properties
      public bool this[int i] { get; }
      public int LowerBound { get; }
      public int UpperBound { get; }

      // ...
}

A PascalSet (so called because it implements a set not unlike the Set class used in Pascal) corresponds to the mathematical notation of a set, where items in some finite universe can be contained in the collection. The PascalSet class implements simple operations like checking subsets, supersets, unions, and differences between sets.

More information on Sets