为什么array.slice表现不同的（长度，N） [英] Why does array.slice behave differently for (length, n)

问题描述

如果我有一个数组 A ：

1. A [则为a.length] 收益无。不错。


2. A [则为a.length，X] 收益 [] 。不错。


3. A [则为a.length + X，Y] 收益无。不符合2。

1. a[a.length] returns nil. Good.
2. a[a.length, x] returns []. Good.
3. a[a.length+x, y] returns nil. Inconsistent with 2.

虽然这种行为是记录，这似乎很奇怪。

While this behavior is documented, it seems odd.

谁能解释一下这个设计背后的原因是什么？

Can anybody explain the reasons behind this design?

推荐答案

考虑这个

a = [0, 1, 2, 3] #=> [0, 1, 2, 3]
a[0, 10]         #=> [0, 1, 2, 3]
a[1, 10]         #=>    [1, 2, 3]
a[2, 10]         #=>       [2, 3]
a[3, 10]         #=>          [3]
a[4, 10]         #=>           []
a[5, 10]         #=>          nil

所以 A [4,10] 是和数组的一端之间的切片 3 []

So a[4, 10] is the slice between the 3 and the end of the array which is []

在哪里为 A [4] 和 A [5,10] 正在访问不在元素数组

Where as a[4] and a[5, 10] are accessing elements that aren't in the array

有可能有助于认为限幅点的作为在元件之间存在，而非元件本身。

It may help to think of the slice points as being between the elements, rather than the elements themselves.

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