>> I think it's actually more correct to say that {} has an undefined
>> number of dimensions.
>
> That is your opinion, but not my argument above.
I'm aware of that. I believe that the semantics of array operations
should carry more weight than a count of curly braces, but certainly
you don't have to agree.
>> But {}, and ONLY {}, can be concatenated with an array of any number
>> of dimensions.
>
> Which doesn't necessarily make much sense ...
Well, we could change it, which would render the argument about the
current semantics of {} moot. The obvious thing to do would be create
separate empty arrays of dimensions 1, 2, 3, 4, 5, and 6, say
'{}'::int[], '{{}}'::int[], etc. This would break backward
compatibility for people using multi-dimensional arrays, but that
might not be that many people. (Dunno.)
Alternatively, we could make separate types int[], int[][], int[][][],
etc. Then '{}'::int[] would be an empty one-dimensional array,
'{}'::int[][] would be an empty two-dimensional array, etc.
...Robert