访问数组边界以外的数组＃拆分行为

Question

irb会话如下：

>> ar = [:peanute, :butter, :and, :jelly]
=> [:peanute, :butter, :and, :jelly]
>> ar[0, 1]
=> [:peanute]
>> ar[4, 1]
=> []
>> ar[5, 1]
=> nil

为什么ar [4,1]不像ar [5,1]那样返回nil？有人会解释这种行为吗？

Answer 1

documentation中提到了这一特例。