static IterableIterator<L<Int>> allSpreads(final int toSpread, final int buckets) {
  ret iff(new F0 {
    L<Int> collecting = ll();
    int remaining = toSpread;
    bool incrementing;

    public O get() {
      while true {
        ping();
        
        if (incrementing)
          if (remaining == 0) {
            remaining -= last(collecting);
            dropLast(collecting);
            if (empty(collecting)) ret endMarker();
          } else {
            setLast(collecting, last(collecting)+1);
            --remaining;
        
        // return list
        if (l(collecting) >= buckets-1)
          L<Int> result = listPlus(collecting, last(remaining));
          setLast(collecting, last(collecting)+1);
          ret result;
        }
      
        // backtrace
        while (nempty(collecting) && last(collecting) >= last(remaining)) {
          dropLast(collecting);
          dropLast(remaining);
          setLast(collecting, last(collecting)+1);
        }

        // done
        if (empty(collecting)) ret endMarker();
        
        // recurse
        remaining.add(last(remaining)-last(collecting));
        collecting.add(0);
      }
    }
  });
}