Re: Empty? No. Array? No. Has? Yes.

[Coda Highland <chighland@...>]

On Wed, Jul 3, 2013 at 12:31 PM, Sean Conner <sean@conman.org> wrote:
> It was thus said that the Great Coda Highland once stated:
>> On Wed, Jul 3, 2013 at 11:44 AM, Roberto Ierusalimschy
>> <roberto@inf.puc-rio.br> wrote:
>> >> With my JSON library it is possible to write
>> >>
>> >>   getmetatable(db.null).__tojson = function () return "null" end
>> >>
>> >> and db.null would work for the JSON encoder as well.  And in the other
>> >> direction you can just tell the decoder to use any arbitrary value for null.
>> >
>> > It should be clear that how to represent "null" in JSON is a problem
>> > quite different from how to represent "null" in Lua.
>> >
>> > If we add a new value in Lua (call it null, empty, nothing, whatever)
>> > to represent null in JSON, the problem with JSON is solved, because
>> > we do not change JSON. This change is trivial to do, but only solves
>> > the JSON problem.
>> >
>> > If we add a new value in Lua (call it null, empty, nothing, whatever)
>> > to represent null in *Lua*, the problem is not solved. Now Lua has a new
>> > value, and therefore we need yet another value to represent this new
>> > Lua value. Adding new values will not solve the problem in Lua. Period.
>> >
>> > -- Roberto
>> >
>>
>> I'm afraid I don't understand the problem here. How is it that you'd
>> need a new value to describe a "null" value? It seems to me that if
>> it's permitted to be its own description, problem solved.
>
>   Here's a JSON object:
>
>         [ 1 , 2 , 3 , null , 5 , 6 , 7 ]
>
>   While that does have a represntation in Lua:
>
>         { 1 , 2 , 3 , nil , 5 , 6 , 7 }
>
> it doesn't have a defined length (depending on implementation of Lua and/or
> the JSON parser, I can see it having a length of 3, 6 or 7).
>
>   -spc (Erm ... that reminds me, I need to figure out how to handle that
>         with my JSON [1] parser ... )
>
> [1]     https://github.com/spc476/LPeg-Parsers/blob/master/json.lua
>
>

No, no, that's not what I mean. If we did introduce a "null" value,
what complications would arise from that?

/s/ Adam