code: func symSwap(u Comparators, start1, start2, end int) {
  	for i := 0; i < end; i++ {
  		u[start1+i], u[start2+i] = u[start2+i], u[start1+i]
  	}
  }
docs: // symSwap will perform a rotation or swap between the provided
  // indices.  Again, there is duplication here with swap, but
  // we are buying performance.