Void type in base

[Edward Kmett]

It doesn't sound like the newtype coercions we are likely to get are going
to be usable in this way regardless. It was just the historical reason for
why I kept vacuous around. =)

-Edward

On Thu, Jul 18, 2013 at 8:24 PM, Dan Doel <dan.doel at gmail.com> wrote:

> Are GHC's newtype coercions going to know that the second step of 'f Void
> -> f (forall a. a) -> forall a. f a' is valid due to f being a Functor? I'm
> not sure that can be counted upon.
>
>
>
> On Thu, Jul 18, 2013 at 1:33 PM, Edward Kmett <ekmett at gmail.com> wrote:
>
>> You can get there if you use
>>
>> newtype Void = Void { absurd :: forall a. a }
>>
>> instead.
>>
>> -Edward
>>
>> On Wed, Jul 17, 2013 at 6:03 PM, Joachim Breitner <
>> mail at joachim-breitner.de> wrote:
>>
>>> Hi,
>>>
>>> Am Mittwoch, den 17.07.2013, 15:27 -0400 schrieb Edward Kmett:
>>> > Now the Data.Void.Unsafe module provides that functionality (as
>>> > unsafeVacuous) and vacuous itself is provided for compatibility with
>>> > code that used it, and is left in case we ever get something in
>>> > Functor that lets us apply newtype coercions directly to the Functor's
>>> > parameter.
>>>
>>> how would lifting newtype coercions to functors help here:
>>>   vacuous :: Functor f => f Void -> f a
>>> Void is not a newtype of a.
>>>
>>> Greetings,
>>> Joachim
>>>
>>>
>>> --
>>> Joachim “nomeata” Breitner
>>>   mail at joachim-breitner.de • http://www.joachim-breitner.de/
>>>   Jabber: nomeata at joachim-breitner.de  • GPG-Key: 0x4743206C
>>>   Debian Developer: nomeata at debian.org
>>>
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>>>
>>
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