理解下面mylist[2]和mylist[[2]]下面之间差异的基本逻辑或哲学基础是什么？
理解单方括号与双方括号的简单逻辑方法是什么？
> mylist <- list(1, list("a","b","c"))
> mylist[2]
# [[1]]
# [[1]][[1]]
# [1] "a"
# [[1]][[2]]
# [1] "b"
# [[1]][[3]]
# [1] "c"
> mylist[[2]]
# [[1]]
# [1] "a"
# [[2]]
# [1] "b"
# [[3]]
# [1] "c"