null Vs [] return arrays

[Torarin]

2011/4/1 Regan Heath <regan at netmail.co.nz>:
> On Mon, 28 Mar 2011 17:54:29 +0100, bearophile <bearophileHUGS at lycps.com>
> wrote:
>>
>> Steven Schveighoffer:
>>
>>> So essentially, you are getting the same thing, but using [] is slower.
>>
>> It seems I was right then, thank you and Kagamin for the answers.
>
> This may be slightly OT but I just wanted to raise the point that
> conceptually it's nice to be able to express (exists but is empty) and (does
> not exist).  Pointers/references have null as a (does not exist) "value" and
> this is incredibly useful.  Try doing the same thing with 'int' .. it
> requires you either use int* or pass an additional boolean to indicate
> existence.. yuck.
>
> I'd suggest if someone types '[]' they mean (exists but is empty) and if
> they type 'null' they mean (does not exist) and they may be relying on the
> .ptr value to differentiate these cases, which is useful.  If you're not
> interested in the difference, and you need performance, you simply use
> 'null'.  Everybody is happy. :)
>
> R
>

For associative arrays it certainly would be nice to be able to do
something like
string[string] options = [:];
so that functions can manipulate an empty aa without using ref.

Torarin