static <A> LL<A> allSubsetsOfLength(int m, L<A> objects) {
  new LL<A> subsets;
  new L<int> pot;
  int n = l(objects);
  int p = 1;
  if (m==0) { subsets.add(new L); ret subsets; }
  for (int i=0; i<=n; i++){
      pot.add(p);
      p*=2;
  }
  for (int i=1; i<p; i++){
      bool[] binArray = new bool[n];
      int y = i;
      int sum = 0;
      for (int j = n-1; j>=0; j--) {
          int currentPot = pot.get(j);
          if (y >= currentPot) {
              binArray[j] = true;
              y -= currentPot;
              sum++;
          }
          if (y<=0)
              break;
      }
      if (sum==m){
          new L<A> subsubset;
          for (int j=0; j < n; j++)
              if (binArray[j])
                  subsubset.add(objects.get(j));
          subsets.add(subsubset);
      }
  }

  ret subsets;
}