[Haskell-cafe] Is () a 0-length tuple?

[Deniz Dogan]

2009/11/7 Matthew Gruen <wikigracenotes at gmail.com>:
> Forgot to cc haskell-cafe. Trying again:
>
> ---------- Forwarded message ----------
> From: Matthew Gruen <wikigracenotes at gmail.com>
> Date: Sat, Nov 7, 2009 at 2:16 PM
> Subject: Re: [Haskell-cafe] Is () a 0-length tuple?
> To: Pasqualino Titto Assini <tittoassini at gmail.com>
>
> On Sat, Nov 7, 2009 at 2:00 PM, Pasqualino "Titto" Assini
> <tittoassini at gmail.com> wrote:
>> The syntax is similar, but what else is?
>>
>> In JavaScript there is a "null" value, that is the only value of the null type.
>>
>> Isn't () the same thing?  The only value of the unary type?
>>
>> Best,
>>
>>                 titto
>>
>> Pasqualino "Titto" Assini, Ph.D.
>> http://quicquid.org/
>
> In JavaScript's case, there is not a null type. The null value belongs
> to the 'object' type, whereas the undefined value belongs to the
> 'undefined' type. This is all a lot less useful when you realize that
> JavaScript has a dynamic type system. But this is JSON, not
> JavaScript.
>
> In JSON, arrays, objects, strings, and numbers can be any number of
> values. Booleans can be two values. Null can only be one value.
> Personally, I think a better mapping for () would be JSNull, since
> both have only one value in normal form. However, there is not
> necessarily any natural mapping between Haskell values and JSON
> values. The library tries to provide as many as possible, including
> (), which it happens to map to JSArray [] instead of JSNull. As long
> as the library is internally consistent, though, it should be fine.

What point are you trying to make by distinguishing JSON from
JavaScript? JSON is a subset of JavaScript, they share the same type
system. "Null can be only one value." This doesn't make sense to me,
since as you say null is not a type, but a value.

-- 
Deniz Dogan