[Haskell-cafe] an idea for modifiyng data/newtype syntax: use `::=` instead of `=`

[MigMit]

I disagree.

Отправлено с iPad

> 9 авг. 2015 г., в 12:37, Tom Ellis <tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk> написал(а):
> 
> On Sun, Aug 09, 2015 at 12:15:47PM +0200, MigMit wrote:
>>> Right, you can distinguish data declarations from newtype declarations this
>>> way, but by using Template Haskell you can also distinguish
>>> 
>>>   * data A = A Int
>>>   * data A = A { a :: Int }
>>>   * data A = A' Int
>>>   * data A = A Int !(), and
>>>   * newtype B = B A (where A has one of the above definitions)
>> 
>> Sure, because they are different.
>> 
>>> from each other.  My claim is that
>>> 
>>>   * data B = B !A
>>> 
>>> is as indistinguishable from the above four as they are from each other.
>> 
>> Can you please NOT say that some thing can be distinguished AND that they
>> are indistinguishable in the same post?
> 
> I think we are perhaps talking at cross purposes.
> 
> To clarify, here is an explicit statement (somewhat weaker than the full
> generality of my claim):
> 
>    `data D = D !T` and `newtype N = N T` are isomorphic in the sense that
>    there exist `f :: D -> N` and `g :: N -> D` such that `f . g = id` and
>    `g . f = id`.
> 
> Do you agree or disagree with this statement?  Then we may proceed.
> 
> Tom
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