r - 为什么从索引零开始对向量进行切片是有效的？

Question

v <- 1:10

于是我无意中发现:

v[0:10] == v[1:10]

输出:

[1] TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE

如何？首先，我认为 R 指数从 1 开始？

Answer 1

来自 R language definition (第 3.4.1 节，“按向量索引”，“整数”):

A special case is the zero index, which has null effects: x[0] is an empty vector and otherwise including zeros among positive or negative indices has the same effect as if they were omitted.

Another SO question asks "why is this useful"? ，没有很多令人满意的答案:这是一个有趣的问题，但似乎是 r-devel@r-project.org 的主题。而不是...