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

2009-11-08 Thread Deniz Dogan
2009/11/8 Matthew Gruen :
> On Sun, Nov 8, 2009 at 6:21 AM, Deniz Dogan 
> wrote:
>> 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
>>
>
> It seems I underestimated the typedness of null in JavaScript :) I checked
> the ECMAScript specification, and it does refer to a "null type".. so titto
> was right.[1] My opinion is that JSON's 'type system' should be analyzed
> orthogonal to JavaScript's regardless. If JSON is a subset of JavaScript, it
> is primarily a syntactic one. When I said "Null can be only one value",
> implying that null is a type, I was referring to JSON's null, not
> JavaScript's null. In JSON, null *is* definitely a unit type. When
> considering mappings between Haskell and JSON in the case of (), we should
> see that () is a unit type in Haskell, null is a unit type in JSON
> (regardless of its role in JavaScript), and maybe try to associate them.
>
> —Matt
>
> [1] I was misled by the fact that typeof null = 'object'. The logic behind
> this, I think, is that null is meant to be bound to a variable that would
> otherwise be a reference to an actual object value. Many have criticized
> this result, e.g. Douglas Crockford
> (http://javascript.crockford.com/remedial.html)
>

Let's keep in mind when reading the ECMAScript specification that
JavaScript is merely based on it and breaks it on several different
points. :)

-- 
Deniz Dogan
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-08 Thread Matthew Gruen
On Sun, Nov 8, 2009 at 6:21 AM, Deniz Dogan 
wrote:
> 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
>

It seems I underestimated the typedness of null in JavaScript :) I checked
the ECMAScript specification, and it does refer to a "null type".. so titto
was right.[1] My opinion is that JSON's 'type system' should be analyzed
orthogonal to JavaScript's regardless. If JSON is a subset of JavaScript, it
is primarily a syntactic one. When I said "Null can be only one value",
implying that null is a type, I was referring to JSON's null, not
JavaScript's null. In JSON, null *is* definitely a unit type. When
considering mappings between Haskell and JSON in the case of (), we should
see that () is a unit type in Haskell, null is a unit type in JSON
(regardless of its role in JavaScript), and maybe try to associate them.

—Matt

[1] I was misled by the fact that typeof null = 'object'. The logic behind
this, I think, is that null is meant to be bound to a variable that would
otherwise be a reference to an actual object value. Many have criticized
this result, e.g. Douglas Crockford (
http://javascript.crockford.com/remedial.html)
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-08 Thread Deniz Dogan
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
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-08 Thread Conor McBride

How about this?

{-# LANGUAGE ThinkTotal #-}

On 8 Nov 2009, at 09:53, Svein Ove Aas wrote:


On Sun, Nov 8, 2009 at 9:52 AM, Ketil Malde  wrote:

Eugene Kirpichov  writes:

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?



No, () has two values: () and undefined (t.i., _|_).


() is the only value of ().

If we could agree a standard set of email pragmas, we could save
ourselves a lot of violent agreement.

Cheers

Conor

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

2009-11-08 Thread Svein Ove Aas
On Sun, Nov 8, 2009 at 9:52 AM, Ketil Malde  wrote:
> Eugene Kirpichov  writes:
>
>>> 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?
>
>> No, () has two values: () and undefined (t.i., _|_).
>
How should I put it..?
undefined is bottom, but bottom is not undefined?

There are plenty of other constructions that are bottom. Infinite
loops, throws, errors.. common for all of them, of course, is that you
can't pattern-match on them or otherwise use them in pure code, and
they generally don't act like values.

So, can't we just say that () has a single value, namely ()? It'd make
this much simpler, and we won't have to deal with the Nihil monoid.

==

data Nihil

instance Monoid Nihil where
  mappend _ _ = undefined

-- 
Svein Ove Aas
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-08 Thread Ketil Malde
Eugene Kirpichov  writes:

>> 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?

> No, () has two values: () and undefined (t.i., _|_).

I'd argue that yes, they're the same thing, since any function returning
"null" in JS might also fail to terminate or terminate with an
exception.

-k
-- 
If I haven't seen further, it is by standing in the footprints of giants
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-07 Thread 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.
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Re: [Haskell-cafe] Is () a 0-length tuple?

2009-11-07 Thread Eugene Kirpichov
2009/11/7 Pasqualino "Titto" Assini :
> 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?
>
No, () has two values: () and undefined (t.i., _|_).

> Best,
>
>                 titto
>
>
> 2009/11/6 John Dorsey :
>>> In what sense () is a 0-length tuple?
>>
>> In what sense isn't it?
>>
>> Data.Tuple is much to narrow to be of any use here.  () is in at least most,
>> if not all, of the type classes that tuples are in.  The syntax is
>> strikingly similar.
>>
>> If you ask me, it walks/quacks/smells like a duck, so it's a duck.
>>
>> Regards,
>> John
>>
>> ___
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>>
>
>
>
> --
> Pasqualino "Titto" Assini, Ph.D.
> http://quicquid.org/
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-- 
Eugene Kirpichov
Web IR developer, market.yandex.ru
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Fwd: [Haskell-cafe] Is () a 0-length tuple?

2009-11-07 Thread Pasqualino "Titto" Assini
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


2009/11/6 John Dorsey :
>> In what sense () is a 0-length tuple?
>
> In what sense isn't it?
>
> Data.Tuple is much to narrow to be of any use here.  () is in at least most,
> if not all, of the type classes that tuples are in.  The syntax is
> strikingly similar.
>
> If you ask me, it walks/quacks/smells like a duck, so it's a duck.
>
> Regards,
> John
>
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>



-- 
Pasqualino "Titto" Assini, Ph.D.
http://quicquid.org/
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