2009/11/7 Matthew Gruen :

Forgot to cc haskell-cafe. Trying again:

---------- Forwarded message ---------- From: Matthew Gruen Date: Sat, Nov 7, 2009 at 2:16 PM Subject: Re: [Haskell-cafe] Is () a 0-length tuple? To: Pasqualino Titto Assini

On Sat, Nov 7, 2009 at 2:00 PM, Pasqualino "Titto" Assini 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