public ISet<T> diff(ISet<T> aSet)
    {
         T[] aTmp = (T[])aSet.getAll();
       ISet<T> newSet = new Set();

       for(int i = 0 ; i < this.elem; i++)
       {
           newSet.add(((T)this.set[i]));
       }
       for(int i = 0; i < aTmp.length; i++)
       {
            if(newSet.isMember(aTmp[i]))
            {
                newSet.remove(aTmp[i]);
            }
       }
       return newSet;
    }