User blog comment:Syst3ms/Funky Notation/@comment-35470197-20181003080925/@comment-35470197-20181004220910

> I seriously don't understand what is the problem.

The point is that the notion of a nested array depends on not only the current array itself but also on another array.

Remember the following: > \([#]\) is an array, where \(#\) is an array. We call \(#\) a nested array" For example, \([1]\) is an array, and we call \(1\) a nested array.

If the notion of a nested array did not depend on another array (here \([1]\)), then \(1\) in your example \(2[ [1] ]\) were also a nested array. It is not what you intend. Therefore the notion of a nested array depends on another array.

> because the current entry isn't a nested array between a pair of square brackets.

Then I now understand that you are considering a nested array with respect to \(A_0\), but not \(A_1\).