code: func rangeSelection(str string) Selection {
  	m := selRx.FindStringSubmatch(str)
  	if len(m) >= 2 {
  		from, _ := strconv.Atoi(m[1])
  		to, _ := strconv.Atoi(m[2])
  		if from < to {
  			return makeSelection([][]int{{from, to}})
  		}
  	}
  	return nil
  }
docs: // rangeSelection computes the Selection for a text range described
  // by the argument str; the range description must match the selRx
  // regular expression.
  //